DE102018124565A1 - Solar cell coating system - Google Patents

Abstract

The invention relates to a solar cell coating system for producing thin layers on a first solar cell side and / or a second solar cell side of crystalline silicon solar wafers with a throughput of at least 2000 solar wafers per hour (2000 W / h), and a solar cell production line and a Process for the production of solar cells with such a solar cell coating system. The object of the present invention is to show possibilities for the economical production of solar cells with at least one passivated contact. The object is achieved by a solar cell coating system which is designed to produce at least one thin boundary layer from a dielectric material on a first solar cell side and / or a second solar cell side, the boundary layer being electrically conductive, in particular by tunnel currents, at least one doped or undoped Silicon layer on the boundary layer, and at least one protective layer on the at least one silicon layer, the boundary layer and the silicon layer and the protective layer being able to be produced within the solar cell coating system without the silicon solar wafers leaving the solar cell coating system in the meantime.

Description

The present invention relates to a solar cell coating system for producing thin layers on a first solar cell side and / or a second solar cell side of crystalline silicon solar wafers with a throughput of at least 2000 solar wafers per hour (2000 W / h), as well as a solar cell production line and a process for the production of solar cells with such a solar cell coating system.

Various coating systems are used in the production of solar cells, the coating systems being equipped with technical means for producing this layer sequence in accordance with the layer sequence to be produced. For example, the Meyer Burger product FABiA ^{® is} a solar cell coating system for depositing a silicon nitride passivation and anti-reflection layer on the front of the crystalline silicon solar cell and an aluminum oxide and silicon nitride passivation layer on the back. This system can be used in a solar cell production line for the production of PERC solar cells. The coating chambers of this system are equipped with microwave plasma sources, for example for the deposition of silicon nitride (SiN _x ) and for the deposition of aluminum oxide (AlO _x ). Details of the system, for example the number of linear microwave plasma sources for a specific layer, are designed in such a way that the system as a whole has a high throughput and short maintenance intervals at sufficiently large intervals.

Continuous-flow systems with linear microwave plasma sources are frequently used for the oxidation and deposition of dielectric layers for the purposes of passivation and / or optical interference in antireflection or reflection layers. Systems with parallel plate arrangements and shower heads for homogeneous gas feed can be used well for the homogeneous deposition of high-purity semiconductor layers. Production systems with a high throughput of more than 2000 solar wafers per hour are very specialized in the layers to be produced in them, this applies in particular to systems such as the FABiA, which produce several layers in one pass. Such solar cell coating systems enable particularly low solar cell manufacturing costs.

State-of-the-art solar cell production lines, for example for the production of PERC solar cells, produce solar cells whose efficiencies are below those of top solar cells from the laboratory. Higher efficiencies than mainstream solar cells can be achieved, for example, by the additional passivation of conventionally unpassivated contacts, whereby the manufacturing process and the manufacturing line have to be expanded to implement additional manufacturing steps.

DE 10 2013 219 564 A1 discloses an approach to realizing solar cells with passivated contacts, but does not deal with plant technology that is suitable for carrying out the method.

It is therefore the object of the present invention to show possibilities for the economical production of solar cells with at least one passivated contact and suitable production lines and coating systems.

• - wenigstens einer dünnen Grenzschicht aus einem dielektrischen Material auf einer ersten Solarzellenseite und/oder einer zweiten Solarzellenseite, wobei die Grenzschicht einen elektrischen Stromfluss durch die Grenzschicht, insbesondere einen Tunnelstromfluss, ermöglicht und wenig behindert,
• - wenigstens einer dotierten oder undotierten insbesondere amorphen Siliziumschicht auf der Grenzschicht, und
• - wenigstens einer Schutzschicht auf der wenigstens einen Siliziumschicht , wobei die Grenzschicht und die Siliziumschicht und die Schutzschicht innerhalb der Solarzellen-Beschichtungsanlage herstellbar sind, ohne dass die Silizium-Solarwafer die Solarzellen-Beschichtungsanlage zwischenzeitlich verlassen.

The task is solved by a solar cell coating system which is designed for the production:

• at least one thin boundary layer made of a dielectric material on a first solar cell side and / or a second solar cell side, the boundary layer permitting and little obstructing an electrical current flow through the boundary layer, in particular a tunnel current flow,
• at least one doped or undoped, in particular amorphous, silicon layer on the boundary layer, and
• - At least one protective layer on the at least one silicon layer, the boundary layer and the silicon layer and the protective layer being able to be produced within the solar cell coating system without the silicon solar wafers leaving the solar cell coating system in the meantime.

The solar cell coating system according to the invention enables the upgrading of a conventional solar cell production line for the production of PERC solar cells with unpassivated contacts to a new production line that produces higher quality solar cells with passivated contacts. The improvement potential of the absolute solar cell efficiency is about 1% if one contact is passivated and about 2% if both contacts of the solar cell are passivated. The solar cell coating system can also be a component of a new solar cell production line for solar cells with passivated contacts. To explain the invention, the invention based on the description of a conventional solar cell production line and a conventional production method is to be classified and presented.

In a conventional solar cell production line for the production of solar cells, solar wafers are provided with a basic doping. The basic doping is predominantly p-doping and the solar cells produced from it are referred to as PERC solar cells. With smaller market shares, solar wafers with n-basic doping are also used and solar cells made from them are referred to as PERT solar cells. Because of the greater importance and notoriety of PERC technology, reference is made primarily to this, without this reference being a limitation of the invention thereto.

At the beginning of the manufacturing process, saw damage is usually removed from the sawing of a silicon block into thin wafers in wet chemical plants both from the front side of the solar cell, that is to say from the side of the solar wafer primarily intended for the incidence of light, and from the back side of the solar cell. In addition, textures are created on both sides or on one side. When sawing a single-crystalline silicon block or ingot, single-crystal solar wafers are produced, and when sawing a polycrystalline block or brick, poly-crystalline silicon wafers are formed. Single-crystalline and polycrystalline wafers are summarized under the generic term crystalline wafers. If light is only provided on the front side of the solar cell, then the solar cells are also referred to as monofacial solar cells. If the back of the solar cell also allows light to enter, this is referred to as the bifacial solar cell. Depending on the direction of installation and the optical properties of the substrate, bifacial solar modules made up of bifacial solar cells can produce 10-20% more annual yield compared to monofacial solar modules. Texturing, that is to say roughness generation, on the surface brings about an increase in efficiency on the light-incident side. In the case of bifacial solar cells in particular, a texture on both sides can also be provided. With monofacial solar cells, however, a texture on the back is disadvantageous. In some cases, therefore, a texture created on both sides by wet chemistry is removed from the back in an additional process step. Textures can also be produced using dry etching processes, whereby textures produced using dry etching processes can achieve lower reflectivities and higher solar yields.

Then a doping opposite to the basic doping is diffused into the solar wafer in a diffusion furnace; for example, a POCl ₃ gas phase is used to produce a phosphorus-doped emitter (n-doping) on the front by first p-doping in the surface layers of the front and the back Solar wafers diffuse in phosphorus and then the phosphorus-doped back layer is removed again, so that the boron or p-doped base material is again exposed on the back. Other diffusion steps can be used for superficial higher doping (surface field). Before applying layers, cleaning steps are necessary to remove chemical residues and contaminants. In some cases, a thin SiO ₂ layer is also grown on surfaces of the solar wafer in connection with cleaning, because this SiO ₂ produced by defined oxidation represents a good passivation basis.

In further production steps, dielectric layers or layer stacks are applied to both sides of the solar cell in coating systems, which serve as passivation layers and, at least on the front side, as anti-reflection layers. In a SiO ₂ -AlO _x -SiN _x : H layer stack on the back, the hydrogen-containing silicon nitride layer serves as a hydrogen source from which hydrogen can diffuse into the layers underneath, which ultimately results in a very good passivation. The stoichiometry index x and the hydrogen note: H are also partially omitted because a person skilled in the art knows useful properties of the addressed layers even without these notes and reads them when specifying a material without a stoichiometry index. On the back, the passivation layer can be designed as a reflection layer, which better reflects red and infrared light, which has shone through the solar cell from the front, back into the solar cell than other layer designs. In particular in the case of bifacial solar cells, an antireflection layer can also be provided on the back, which for the most part lets light incident from the back into the solar cell in order to be used there to generate electricity. CVD, PECVD and / or ALD systems are generally used to produce the passivation and reflection or anti-reflection layers.

Metal pastes, in particular silver and aluminum pastes, are often used to make electrical connections to industrial solar cells. The metal pastes can be applied in screen printing systems with screen printing on partial areas, for example in the area of contact fingers and bus bars on the front sides, or over the entire area on the back sides. With standard solar cells, an aluminum paste was applied over the entire surface of the back. In contrast to standard solar cells, the back of solar cells in PERC technology is no longer contacted over the entire area, but only at local contact points at which the back layers have been removed completely or to such an extent that the metal pastes etch through the remaining layers during contact firing can make a metallic contact. The PERC solar cell is passivated through the passivation layers between the local rear contacts achieves a higher efficiency than standard solar cells. In the area of the contacts, both on the front of the solar cell and on the back, the contacts formed by firing from the metal pastes have penetrated the passivation layers. In the area of the contacts, the PERC solar cells and PERT solar cells are not passivated, which means that there are still active recombination centers at which electron-hole pairs generated by the photo effect can recombine before they reach the contacts of the solar cell separately and can be used as electrical energy.

With the solar cell coating system according to the invention, it is now possible to expand a conventional solar cell production line in such a way that instead of conventional solar cells it is possible to produce improved solar cells with passivated contacts. In the case of passivated contacts, a boundary layer acting as a passivation layer is arranged between the contact area and the solar cell volume. This passivation layer can be such a thin dielectric boundary layer that it can be penetrated by tunnel currents as a tunnel layer of charge carriers, although it is made of a material that is insulating with a greater layer thickness, for example SiO ₂ . The guiding mechanism at the boundary layer does not necessarily have to be a tunnel current, other guiding mechanisms are also possible, for example via defects in the boundary layer. Defects in the crystallization can be defects in the boundary layer. The defects can also be filled, for example, with doped silicon. In the latter case, the dielectric layer contains conductive pore fillings, so that the layer of an actually dielectric material is then a conductive layer overall.

The current flow through the boundary layer is possible in particular perpendicularly through the boundary layer or in the direction of the surface normal. In contrast, the boundary layer can have insulator properties in lateral directions. In the solar cell coating system, the boundary layer is produced from a material that is actually a dielectric material, at least with a greater thickness. However, this does not mean that the boundary layer made of a dielectric material with the small thickness of at most a few nanometers actually consist of the dielectric material throughout. Instead, upon closer inspection, the boundary layer can also be a conductive layer, which is, for example, a composite layer made of a porous dielectric matrix and filled pores. The exact structural and chemical analysis of the smallest structures in atomic sizes is generally difficult and regularly involves uncertainties. What is essential is the result that, owing to the presence of the passivated contact arrangement, sufficiently low contact resistances and sufficiently good passivations and overall improved efficiency of the solar cell are achieved.

The solar cell coating system according to the invention is a system that produces several layers on top of one another in a system run or in a manufacturing step of the solar cell manufacturing method, namely the boundary layer, a silicon layer and a protective layer. The protective layer protects the freshly deposited silicon layer from unwanted absorption of air humidity or unwanted cross-contamination with other dopants.

Silicon layers deposited by PECVD, in particular amorphous silicon layers, which are produced at temperatures below 600 ° C., are porous layers. The amorphous layer can also already contain microcrystalline components, ie it can be a polymorphic layer. In the event of a vacuum interruption and contact with air containing moisture, moisture is built into these layers. The contact of the layer at higher temperatures with oxidizing agents such as oxygen or water vapor can lead to the oxidation of the entire layer. In the presence of dopant compounds, in particular diborane or phosphine, during the gas phase deposition, in-situ doped silicon layers are formed, which contain the dopants required for high conductivities immediately after the deposition, so that the dopants do not have to be subsequently introduced into the layer. However, some of the dopants are not yet electrically active after deposition, which means that they do not yet contribute to good conductivity. To activate the dopants, processing steps at higher temperatures are sometimes required. Properties of a layer that are present after layer deposition, for example the conductivity of an in situ doped deposited silicon layer, can still be changed in subsequent method steps, for example in a high temperature step. In the separation step, the prerequisites are created that the solar cell will work well in the end. The integration of the deposition step into the entire manufacturing process also influences the properties of the solar cell. A precise specification of the properties of layers produced in a patent claim is difficult because possible process windows depend on other process steps and boundary conditions. The result to be achieved, namely solar cells with passivated contacts which are improved compared to the prior art, is nevertheless not achievable with any layers, but only layers in narrow property ranges which can only be achieved by solar cell coating systems designed to meet requirements can be manufactured.

The protective layer is a dense layer which protects the silicon layer from unwanted changes in subsequent process steps. The protective layer can be a layer stack or a gradient layer. For example, the protective layer can first consist of a silicon nitride layer on the silicon surface and a silicon oxide layer thereon. In particular, the good diffusion barrier properties of the silicon nitride layer can be used. The property of silicon oxide layers can be exploited that silicon oxide can be removed again easily without damaging the underlying silicon. The material can also be an oxynitride gradient layer in which the proportion of nitrogen becomes smaller as the distance to the silicon layer increases and the proportion of oxygen increases. The precisely used materials and layer thicknesses have to be optimized for integration into the overall process. Part of the protective layer can also be deposited as a dopant source layer, from which a dopant diffuses into the underlying silicon layer. For the production of layers in individual process steps of the production process, the production line for carrying out the process is equipped with suitable coating systems which are designed in such a way that they can produce the required layers.

The solar cell coating system according to the invention can be integrated as an upgrade into a conventional solar cell production line. A separate, additional high-temperature step at temperatures above 600 ° C for the crystallization of the previously amorphous or partially microcrystalline silicon layer and for the activation of dopants or for the diffusion of dopants and a separate, additional crystallization furnace are unnecessary if the protective layer provides spatial separation and one already existing high-temperature step and an associated high-temperature treatment system already exist and can be easily used. The solar cell coating system according to the invention, the solar cell production line equipped with it and a method based thereon can thus represent a surprisingly simple solution for producing contact-passivated solar cells.

The largest possible system throughputs of over 2000 solar wafers / h (w / h), better greater than 4000 w / h or greater than 6000 w / h can either be achieved by processing a sufficient number of wafers together in a slow process or by having a few wafers in quick succession go through fast processes. Both approaches (or mixed approaches in between) are used in different plants according to the invention. The production of the different layers can be carried out at the same location with a time offset, for example, by first introducing exit gases for the production of a layer and later CVD output gases (precursors) for production into a batch furnace tube in which many wafers are on a boat another layer. The system can also have a plurality of batch processing reactors into which the wafers, substrate carriers loaded with wafers or loaded boats are transported one after the other.

• - wenigstens einen Grenzschicht-Herstellungsbereich, in welchem die dünne Grenzschicht aus einem dielektrischen Material herstellbar ist, wobei die Grenzschicht einen elektrischen Stromfluss durch die Grenzschicht, insbesondere einen Tunnelstromfluss, ermöglicht und wenig behindert,
• - wenigstens einen Si-Abscheidebereich, in welchem die dotierte oder undotierte insbesondere amorphe Siliziumschicht auf der Grenzschicht abscheidbar ist, und
• - wenigstens einen Schutzschicht-Abscheidebereich, in welchem die Schutzschicht direkt auf der Siliziumschicht oder auf einer zuvor auf der Siliziumschicht abgeschiedenen Dotierschicht abscheidbar ist, wobei die Grenzschicht und die Siliziumschicht und die Schutzschicht in einem Durchlauf durch die Solarzellen-Beschichtungsanlage herstellbar sind. Diese Anlage ist eine Durchlaufanlage, die durch schnelle gleichzeitige Bearbeitung weniger Solarwafer und eine große Durchlaufgeschwindigkeit vieler Solarwafer einen ausreichend großen Anlagendurchsatz erreicht.

The solar cell coating system according to the invention can also produce the different layers in spatially separated areas of the system, in that the solar cell coating system has:

• at least one boundary layer production area in which the thin boundary layer can be produced from a dielectric material, the boundary layer permitting and little obstructing an electrical current flow through the boundary layer, in particular a tunnel current flow,
• at least one Si deposition region in which the doped or undoped, in particular amorphous, silicon layer can be deposited on the boundary layer, and
• - At least one protective layer deposition area in which the protective layer can be deposited directly on the silicon layer or on a doping layer previously deposited on the silicon layer, the boundary layer and the silicon layer and the protective layer being able to be produced in one pass through the solar cell coating system. This system is a continuous system, which achieves a sufficiently large system throughput due to the rapid simultaneous processing of fewer solar wafers and a high throughput speed of many solar wafers.

The individual manufacturing areas can be separate chambers. In some cases, the individual manufacturing areas are not separated from each other by completely closed, physical chamber walls, but rather by simple means, such as Panels, gas curtains and / or clearances.

The silicon layer initially deposited on the boundary layer serves for contacting through the metal contacts. In this layer, the presence of recombination centers is less critical than in the solar cell volume, because the charge carriers are already separated here and the minority charge carrier type is more likely not available for recombination. For a sufficient The silicon layer must be doped for conductivity or for sufficiently low contact resistances. An in-situ doping deposition can be used to introduce the dopants, in which a dopant gas, for example diborane, is already present during the deposition and as a result the dopant, for example boron, is built into the layer during the deposition. Alternatively, the dopant can also be made from another layer, for example from a borosilicate glass layer ( BSG ) or from a layer of phosphorus silicate glass ( PSG ), are diffused into a previously undoped layer. Doped layers on one side of the solar cell can also be produced by diffusing a high doping into the crystalline wafer or into a silicon layer. P-doping with boron can be diffused, for example, from a BBr ₃ gas phase atmosphere or n-doping with phosphorus from a phosphorus oxychloride (POCl ₃ ) gas phase atmosphere. The side of the solar cell that is not to be doped is either protected from the diffusion step by means of a protective layer or the side is first doped with and then the doped layer is removed chemically (in particular wet-chemically) on one side of the solar cell. Dopants can also be introduced by ion implantation, areas of opposite doping regions being spatially separated from one another can be produced by mask techniques on the back of a solar wafer. In order for dopants to become largely effective in a layer deposited in situ at low temperatures, for example below 400 ° C., an activation, ie a temperature treatment at higher temperatures, is generally necessary. At these higher temperatures, the previously deposited silicon layer can also be compacted and crystallized at the same time.

The solar cell coating system can be equipped to produce the boundary layer on both sides in the boundary layer production area on the first solar cell side and the second solar cell side, as well as on the first solar cell side an Si coating of a first doping type (n-doping or p-doping) and to deposit a Si coating of a second doping type opposite to the first doping type on the second solar cell side. The deposited silicon layer can have a thickness between 15 and 500 nm, preferably between 50 and 150 nm, specifically, for example, 75 nm. In the production of one-sided passivated contacts on the backs of PERC and PERT solar cells using fired metal pastes, good results are achieved without optimizations with layer thicknesses of 120 nm; after process optimization, layer thicknesses of 80 nm and below can be mastered. Even minimizations of the layer thickness down to 15 nm appear possible. Thinner layers have the advantage of lower manufacturing costs. Thicker layers have the advantage that they provide defined layer properties and larger process windows for contacting with metal pastes. With contacting variants without metal pastes, thinner silicon layers can also work. If the silicon layer is partially etched off in subsequent process steps, then larger layer thicknesses may be required in accordance with the required sacrificial layer thickness.

Low-priced and therefore economical solar cells are regularly contacted on both sides, both on the front facing the light and on the back, which is generally at least less illuminated. Since the contacts cause shadowing locally when light falls, they should occupy as little space as possible. Different busbar and finger designs as contact structures and contact structures without busbars, such as those used in the Smart Wire Connection Technology (SWCT), are a technical field in addition to the present invention and are therefore not to be explained further here. Various known contact production methods can be integrated in various methods according to the invention for producing solar cells. Conventional solar cells contacted on both sides, for example PERC solar cells or PERT solar cells, have unpassivated contacts both on their front and on their back. There is potential for improvement for these solar cells in the introduction of passivated rear contacts as well as passivated front contacts. The greatest effect can be achieved if all contacts are passivated. However, only the contacts on the front or on the back can also be passivated, for example because the greatest effect is achieved with such a one-sided passivation or simply because the process used works the easiest. The production of passivated contacts on both sides of the solar cell is more complex, corresponding to twice the number of layers required, than the production of passivated contacts on only one side of the solar cell. A system according to the invention for producing the passivated contacts on the front and a system according to the invention for producing the passivated contacts on the back can be used for the production of passivated contacts on both sides. However, it is also possible to produce all layers on both sides of the solar cell in a single complex system according to the invention. In some cases, synergies can be used, for example by producing a layer such as the boundary layer or the protective layer in one process on both sides of the solar cell. For example, both sides of the solar wafer can be oxidized together to produce boundary layers on both sides. The Silicon layers to be doped on both sides of the solar cell must be carefully manufactured separately to ensure the desired doping. In some cases, it is also necessary to transfer the substrates to other substrate carriers dedicated to the respective deposition.

The boundary layer production area can be an oxidation area, in which in particular a surface layer of the silicon solar wafer is oxidized to form a silicon oxide layer. With its atomic structure, the oxide formed by oxidation is well matched to the crystalline silicon base and is therefore a good or even preferred passivation layer. In addition, oxidation of the substrate is a particularly simple and inexpensive process step. However, other oxide layers can also be produced by oxidation. Oxidations can also be part of ALD deposits. For example, aluminum oxide layers can be produced in layers by alternately attaching a layer of an aluminum precursor to the surface to be coated and then oxidizing it. Under certain conditions, such deposits are also referred to as atomic layer deposits (ALD). The oxidation area can have a shower head through which an O ₃ -containing gas can flow and which is fed by an ozone source. Ozone is a suitable gas to quickly form an oxide layer at low temperatures. The properties of the boundary layer, especially its thickness, have a direct effect on the properties of the solar cells produced. Therefore, the boundary layer must have good homogeneity both on a solar wafer (with-in-wafer (wiw) uniformity) and on neighboring solar wafers (wafer to wafer- (wtw) uniformity). A prerequisite for achieving good homogeneity is an even supply of gas. The uniform gas supply can be realized by shower heads. These can be linear injectors, which can also be viewed as one-dimensional shower heads, each of which provides a uniform gas outflow along a line for solar wafers passing underneath. Several adjacent linear or 1-dimensional injectors can be combined to form a 2-dimensional shower head. The shower head can also be a two-dimensional shower head which provides sufficiently defined partial pressures of the oxidizing agent for one or more solar wafers on an unmoving or moving surface in order to achieve the desired homogeneous oxidation. The ozone source can be an external ozone generator, the ozone being generated in a known manner in a separate room from the ozone generator and being brought into the oxidation region via a line. However, ozone can also be formed directly in the oxidation region from oxygen or another gas containing oxygen, for example by means of a plasma or by means of a UV light source. The oxidation region can have a microwave plasma source and a gas connection for a gas containing O ₂ , O ₃ or N ₂ O. Ions with low energies are generated in microwave plasmas, so that no radiation damage to the treated solar wafer surfaces occurs with a microwave plasma. In addition, high plasma densities and fast processes are possible with microwave plasma sources.

The solar cell coating system can be an inline system in which at least the boundary layer production area, the Si deposition area and the protective layer deposition area are lined up in a line. Plants with transport devices for a straight substrate pass are particularly simple when compared to other types of plant, for example with a circular chamber arrangement around a central handling area. Other advantages of inline systems are their compactness, ease of maintenance and economy. The solar cell coating system can also have two processing paths or inline arrangements that are just aligned or parallel with one another, for example a first processing path for coating the solar cell front side and a second coating path for coating the solar cell rear side.

A Si deposition area of the solar cell coating system can be a lockable PECVD chamber with a PECVD parallel plate arrangement contained therein which can be operated at HF frequency, the PECVD chamber having a silane and a diborane connection. In addition, the chamber has further gas connections, in particular an H ₂ connection. The dopant can also be provided in a dilution in H ₂ . A boron-containing a-Si layer can accordingly be deposited in this chamber. The lockable chamber allows the spatial carry-over of the dopant boron outside the deposition area provided for boron to be kept sufficiently small. A PECVD chamber for depositing an n-doped silicon layer can have a silane connection and a phosphine connection or an arsine connection. Separate PECVD chambers can also be provided for other depositions that involve dopants. For the deposition of the doped or undoped silicon layers, thermal CVD chambers or other spatially limited plasma coating areas can also be present.

The protective layer deposition area of the solar cell coating system according to the invention can have at least one microwave plasma source and in particular gas connections of silane, ammonia, Have nitrous oxide, oxygen and / or methane in order to be able to deposit a SiN _x , SiO _x N _y or SiC _x N _y layer. The protective layer is selected such that it protects the silicon layer underneath before the diffusion of undesired substances, in particular water and undesired dopants, for example a p-doped Si layer in front of phosphorus from a POCl ₃ atmosphere, and other parts of the solar wafer before protects dopant covered by the protective layer. The protective layer preferably also prevents dopant diffusion from the silicon layer into the protective layer, in particular in that it has a diffusion barrier made of silicon nitride.

The solar cell coating system according to the invention can have at least one multilayer production area, in which at least two of the following three layers can be produced one after the other in time: the thin boundary layer made of a dielectric material; the doped or undoped, in particular amorphous silicon layer; and the protective layer. In this solar cell coating system, the layer stack of at least two layers is therefore not produced in layer formation areas located at different locations, but at least two layers are produced at the same location by a time interval between different coating steps. A first layer, then a second layer is therefore produced at the same location. Sometimes a third layer is also made at the same location. The boundary layer and the silicon layer or the silicon layer and the protective layer or the boundary layer and the silicon layer and the protective layer are thus produced in a deposition area in various variants of the invention. If only two of the three layers mentioned are produced in one deposition area, the remaining layer is correspondingly produced in another deposition area.

The solar cell coating system can have at least two coating areas or multi-layer manufacturing areas that can be used simultaneously for layer production. It takes more time to produce several layers than to produce only one layer. In order to achieve the required high throughputs of the coating system even in the case of slow depositions in a coating area, the coating system can have two or more than the same coating areas or multi-layer production areas which can be used simultaneously, so that more substrates can be coated in one time interval than in one System with only one coating area or multi-layer manufacturing area. Further system components with shorter cycle times than the coating areas, for example lock chambers and automation components for reloading substrates, can be assigned to the several coating areas together, so that the coating system is compact and inexpensive overall.

The coating area or the multi-layer manufacturing area can each be a lockable vacuum chamber and the solar cell coating system can be an inline substrate processing system with at least two vacuum chambers and a transport device for two-dimensional substrate carriers, the substrate carriers being cycled by the transport device in transport cycles taking place between work cycles are movable between different chambers of the solar cell coating system. Coating processes are carried out regularly in vacuum chambers, on the one hand because the required clean process conditions can be provided in vacuum chambers and on the other hand partly because physical and / or chemical process requirements require deposition under reduced pressure or in a vacuum. In some cases, normal pressure processes or overpressure processes are also carried out in vacuum chambers because quick gas changes and the required gas purity can be provided in them. Inline systems in which several chambers are arranged along a line can be constructed more compactly than other multi-chamber systems in which several chambers are arranged around a central handling area. Inline solar cell coating systems use large two-dimensional substrate carriers, many of which support substrates, for example forty-two solar wafers arranged in six columns and seven rows, which have correspondingly large surfaces and which require correspondingly large vacuum chambers and other chambers. With these large chambers, the inline concept is of particular advantage over other, less space-saving concepts. The substrate coating system has a transport device for moving the substrate carrier through different chambers. The transport device can have driven and non-driven transport rollers, from which tracks of the substrate carriers are driven and guided. The transport device can also be constructed in some other way, for example using conveyor belts, pendulum beams, pull chains or push rods. Several identical processing chambers can also be arranged one behind the other in an inline system. The transport device then ensures that the multiple chambers are intermittently loaded with unprocessed substrates. After the processing cycle in which substrates have been processed in several chambers at the same time, the processed substrates are transported from several chambers by the transport device in a further transport cycle. The solar cell The coating system has a control system which, among other things, controls the logistical processes of the transport device.

The solar cell coating system can also be designed as a substrate processing system with at least two vacuum chambers and a transport device for the cyclical movement of three-dimensional substrate carriers. For example, the solar cell coating system can have several tube reactors in which substrates received in boats are processed. The substrate surfaces are in different planes in a three-dimensional space. The transport device transports the loaded boats into and out of the individual vacuum chambers. The transport device also partially realizes movements during processing, for example back and forth oscillations to prevent plant-specific processing patterns or for a homogeneous coating.

In various configurations of the invention, the vacuum chambers are equipped with means for in-situ cleaning. Coatings of system parts occur regularly in coating chambers, where no coating is actually required. The coatings must be removed regularly, for example to avoid flaking. A solar cell coating system according to the invention with a plurality of vacuum chambers can be designed to carry out deposition on substrates in one chamber and, at the same time, to clean another vacuum chamber. In such a system, cleaning can be seamlessly integrated into the production process, so that high system availability is achieved. For example, an inline coating system can be set up in such a way that four of the four coating chambers are always used for coating and the fourth chamber is cleaned, with all chambers being cleaned one after the other on a rolling basis.

The object of the invention is also achieved by a solar cell production line for producing solar cells from solar wafers, in which an oppositely doped layer is diffused into the p- or n-doped solar wafer or an oppositely doped layer on the p- or n-doped solar wafer is formed, solar wafers are coated with passivation layers and at least one antireflection layer, and the solar wafers are equipped with contacts for the external electrical connection, with the formation of solar cells, which is characterized in that the solar cell production line according to the invention is compared to a conventional solar cell production line from the prior art Technology additionally has at least one solar cell coating system according to the invention in order to implement at least one passivated contact of the solar cell with this solar cell coating system.

In some exemplary embodiments, a solar cell production line has a solar cell coating system for producing passivated contacts on the back of a PERC solar cell. In other exemplary embodiments, the solar cell production line has a solar cell coating system for producing passivated contacts on the back of a PERC solar cell and a solar cell coating system for producing passivated contacts on the front of the PERC solar cell. In further exemplary embodiments, the solar cell production line has a solar cell coating system for producing passivated contacts on the back and for producing passivated contacts on the front of a PERC solar cell. In other exemplary embodiments not listed individually, solar cell production lines of other technologies, e.g. PERT, equipped with suitable solar cell coating systems according to the invention. The various descriptions of options for solar cell coating systems according to the invention also apply accordingly to various options for different solar cell production lines.

• - in wenigstens einem Grenzschichtherstellungsschritt auf wenigstens einer Seite des Substrates die Grenzschicht hergestellt wird, insbesondere durch Oxidation von Silizium zu Siliziumoxid,
• - in einem auf den Grenzschichtherstellungsschritt vorzugsweise unmittelbar folgenden Si-Abscheideschritt auf der einseitigen Grenzschicht, eine dotierstoffhaltige PECVD Si Abscheidung einer insitu-dotierten Si-Schicht oder bei einer zweiseitigen Grenzschicht wenigstens einseitig eine dotierstoffhaltige PECVD Si-Abscheidung einer insitu-dotierten Si-Schicht und/oder eine einseitige, undotierte PECVD Si-Abscheidung einer undotierten Si-Schicht erfolgt,
• - in einem vorzugsweise unmittelbar darauffolgenden Verfahrensschritt wenigstens eine einseitige Schutzschicht auf der dotierstoffhaltigen Si-Schicht abgeschieden wird,
• - in wenigstens einem Hochtemperaturschritt bei Temperaturen über 800°C ein Dotierstoff in das Siliziumsubstrat oder in die zuvor undotiert abgeschiedene Si-Schicht eindiffundiert und/oder die Dotierung in der insitu-dotierten Schicht aktiviert wird als auch die eine Si-Schicht oder beide Si-Schichten zu nanokristallinen oder mikrokristallinen Si-Schichten mit aktivierten Dotierungen kristallisiert werden, das sich dadurch auszeichnet, dass alle aufgeführten Verfahrensschritte mit einer Schichtherstellung oder Abscheidung in einer erfindungsgemäßen Solarzellen-Beschichtungsanlage durchgeführt werden. Verschiedene Optionen erfindungsgemäßer Solarzellen-Beschichtungsanlagen sind mit entsprechenden Optionen des Herstellungsverfahrens gekoppelt. Der Hochtemperaturschritt kann hingegen in einem separaten Ofen durchgeführt werden.

Furthermore, the object of the invention of methods for producing crystalline silicon-based solar cells, each having a crystalline silicon substrate, at least one p-doped region and at least one n-doped region in the silicon substrate, metallic contacts on the p-doped region and the n-doped region, at least one dielectric boundary layer arranged between the contact and the silicon substrate and having a thickness of less than 5 nm, in particular less than 3 nm, wherein the boundary layer enables and little impedes an electrical current flow through the boundary layer, in particular a tunnel current flow, the Manufacturing process in addition to other process steps has the following process steps in which:

• the boundary layer is produced in at least one boundary layer production step on at least one side of the substrate, in particular by oxidation of silicon to silicon oxide,
• - In a Si deposition step on the one-sided boundary layer, preferably immediately following the boundary layer production step, a dopant-containing PECVD Si deposition of an in situ-doped Si layer or, in the case of a two-sided boundary layer, at least on one side a dopant-containing PECVD Si deposition of an insitu-doped Si layer and / or a one-sided, undoped PECVD Si deposition of an undoped Si layer takes place,
• at least one one-sided protective layer is deposited on the dopant-containing Si layer in a method step that preferably follows immediately afterwards,
• - In at least one high-temperature step at temperatures above 800 ° C., a dopant diffuses into the silicon substrate or into the previously undoped Si layer and / or the doping in the in-situ doped layer is activated as well as the one Si layer or both Si Layers are crystallized into nanocrystalline or microcrystalline Si layers with activated doping, which is characterized in that all the process steps listed are carried out with a layer production or deposition in a solar cell coating system according to the invention. Different options of solar cell coating systems according to the invention are coupled with corresponding options of the manufacturing process. The high temperature step, however, can be carried out in a separate oven.

Compared to a conventional method, the method according to the invention requires only minimal additional investments in additional system technology, because in the simplest case all new method steps can be carried out in a single solar cell coating system according to the invention. The method according to the invention can be carried out in a new production line according to the invention. A conventional solar cell production line can also be expanded to a solar cell production line according to the invention by retrofitting a solar cell coating system according to the invention. The method according to the invention is only slightly more complex than a conventional method, so that investments in solar cell coating systems according to the invention can quickly pay for themselves.

• 1 eine Außenansicht einer erfindungsgemäßen Solarzellen-Beschichtungsanlage,
• 2 eine Übersichtsskizze eines Solarzellen-Beschichtungsanlagen-Ausführungsbeispiels,
• 3. eine Übersichtsskizze eines Solarzellen-Beschichtungsanlagen-Ausführungsbeispiels,
• 4 einen Ablaufplan eines ersten Ausführungsbeispiels des Verfahrens,
• 5. einen Ablaufplan eines zweiten Ausführungsbeispiels des Verfahrens und
• 6. einen Ablaufplan eines dritten Ausführungsbeispiels des Verfahrens zeigt.

The present invention is to be explained in more detail below on the basis of figures and exemplary embodiments, wherein

• 1 an external view of a solar cell coating system according to the invention,
• 2nd an overview sketch of an embodiment of a solar cell coating system,
• 3rd . an overview sketch of an embodiment of a solar cell coating system,
• 4th 1 shows a flowchart of a first exemplary embodiment of the method,
• 5 . a flow chart of a second embodiment of the method and
• 6 . shows a flow chart of a third embodiment of the method.

Figure 1 shows the perspective external view of an embodiment of a solar cell coating system according to the invention 1 . Specifically, the example shown is an inline system in which a boundary layer production area is involved 2nd , a Si deposition area 3rd and a protective layer deposition area 4th are arranged in a line along a direction of passage of substrates through the solar cell coating system.

In addition, the solar cell coating system 1 other components, for example a loading chamber 16 , a transfer chamber 17th and an unloading chamber 18th . Solar cell coating systems 1 also have a large number of individual components, the description of which can be dispensed with in a patent application because the common components are known to a person skilled in the art in the field of the invention.

2nd outlines an embodiment of a solar cell coating system according to the invention 1 which is largely that of 1 corresponds, in a top view. The same reference symbols in different figures generally denote the same or similar elements, so that the explanations for one figure can be transferred to other figures. In 2nd you can see that at the loading module 16 where a substrate support 7 into the solar cell coating system 1 is loaded or smuggled into the boundary layer manufacturing area 2nd adjacent. The boundary layer manufacturing area has the machining direction shown in the illustration of 2nd runs from left to right, a shorter length than the substrate carrier 7 . To produce the boundary layer when passing through the substrate carrier 7 through the boundary layer manufacturing area 2nd Therefore, the chamber valves, not shown, have to be temporarily connected to the loading chamber 16 and a transfer chamber 17th be open to the required space for the substrate carrier 7 to provide. The boundary layer manufacturing area 2nd is an oxidation area, the shower head through which an ozone-containing gas can flow 5 having. In the exemplary embodiment shown, the ozone is generated by an external ozone generator 6 generated. The silicon deposition area 3rd is a separate vacuum chamber with four linear microwave plasma sources 8th , each with a silane connection 10th and a phosphine connector 11 are connected. The phosphine is heavily diluted in hydrogen. The protective layer separation area 4th has three microwave plasma sources 9 to deposit the protective layer, each with a Sil connection 10th , an ammonia connector 12th and a nitrous oxide connection 13 are connected.

In 3rd is another embodiment of a solar cell coating system according to the invention 1' outlines in which the silicon layer is different than in 2nd is deposited. This plant has four silicon deposition areas 3 ' or Si deposition chambers, each with a silane connection 10th and a phosphine connector 11 as well as an NF ₃ connection as a means 15 for in-situ cleaning. In addition, each of the Si deposition areas 3 ' here with a PECVD parallel plate arrangement 14 equipped with which very good layer thickness homogeneities of the Si layers produced can be achieved. In each of three of the four Si deposition areas 3 ' during operation of the system, the substrates are simultaneously placed on a substrate carrier 7 coated and in the fourth deposition chamber 3 ' an in-situ cleaning takes place at the same time, in which Si layers in the chamber are etched away. The gaseous reaction products are pumped out of the vacuum pump of the coating area.

The concept presented with several identical coating areas arranged one behind the other 3 ' can also be used in coating systems that deposit fewer or more than three layers.

1. 1. Bereitstellen eines p-dotierten Solarwafers und nasschemisches Überätzen 110 sowohl der Vorderseite als auch der Rückseite zur Entfernung von beim Sägen des Solarwafers entstandenen Sägeschäden (Stand der Technik),
2. 2. nasschemisches beidseitiges Texturieren 111 der Vorderseite und der Rückseite (Stand der Technik),
3. 3. beidseitiges Reinigen 112 (Stand der Technik),
4. 4. Herstellen einer Grenzschicht 116, nämlich einer Rückseitengrenzschicht durch Oxidation der Rückseite des Solarwafers in einem ozonhaltigen Gasgemisch in der erfindungsgemäßen Solarzellenbeschichtungsanlage, konkret in einer Inline-Durchlaufanlage mit Substratträgern für matrixartig von dem Substratträger aufgenommenen Substrate,
5. 5. PECVD-Abscheiden 117 einer insitu-Bor-dotierten Si Schicht auf der Rückseite der Solarwafer in der erfindungsgemäßen Solarzellenbeschichtungsanlage 1, 1',
6. 6. PECVD- Abscheidung 118 einer aus SiON bestehenden Schutzschicht auf der Bor-dotierten Si Schicht, sowohl auf den beschichteten Rückseiten der Solarwafer als auch auf den beschichteten Substratträgerbereichen, die die Solarwafer-Rückseiten umgeben, in der erfindungsgemäßen Solarzellenbeschichtungsanlage 1. 1',
7. 7. Diffusion 119 von Phosphor in die Solarzellen-Vorderseiten in einem Diffusionsofen, wobei auf der Vorderseite jeweils eine Phosphor-Silikat-Glas-Schicht (PSG) ausgebildet wird (Stand der Technik), und wobei gleichzeitig auf der Rückseite auch die Si-Schicht kristallisiert und auch die Bor-p-Dotierung aktiviert wird (neu),
8. 8. nasschemisches Entfernen 120 der PSG-Schicht von der Vorderseite (Stand der Technik), wobei im Rahmen der vorliegenden Erfindung gleichzeitig auf der Rückseite auch die Schutzschicht mit entfernt wird (neu),
9. 9. PECVD-Abscheidungen 121 - 123 einer Passivierungs- und Antireflexionsschicht auf der Rückseite, bestehend aus einer AlO_x und einer SiN_x:H Schicht, und einer SiN_x:H - Passivierungs- und Antireflexionsschicht auf der Vorderseite (Stand der Technik),
10. 10. Siebdrucken 124 von Metallpasten auf der Vorderseite und der Rückseite (Stand der Technik),
11. 11. Herstellen von metallischen Kontakten 125 aus den Metallpasten in einem Kontaktfeuerungsschritt, in welchem die Metallpasten durch die Passivierungs- und Antireflexionsschichten durchgefeuert und elektrische Kontakte mit der Solarzelle hergestellt werden(Stand der Technik), wobei auf der Rückseite infolge des Vorhandenseins der Grenzschicht die Kontakte passivierte Kontrakte sind (neu).

4th illustrates a first embodiment of the method according to the invention 101 for the production of solar cells based on a flow chart of process sections. The embodiment 1 relates to a process for the production of bifacial PERC solar cells with passivated rear contacts, a corresponding solar cell production line and a corresponding solar cell coating system used in the process. The method according to the first exemplary embodiment has the following steps:

1. 1. Provision of a p-doped solar wafer and wet chemical overetching 110 both the front and the back for removing saw damage caused by sawing the solar wafer (prior art),
2. 2. Wet chemical texturing on both sides 111 the front and the back (state of the art),
3. 3. Double-sided cleaning 112 (State of the art),
4. 4. Establish a boundary layer 116 , namely a rear boundary layer by oxidation of the rear side of the solar wafer in an ozone-containing gas mixture in the solar cell coating system according to the invention, specifically in an inline continuous system with substrate carriers for substrates received in matrix form by the substrate carrier,
5. 5. PECVD deposition 117 an in situ boron doped Si layer on the back of the solar wafer in the solar cell coating system according to the invention 1 , 1' ,
6. 6. PECVD deposition 118 a protective layer made of SiON on the boron-doped Si layer, both on the coated rear sides of the solar wafers and on the coated substrate support regions which surround the solar wafer rear sides, in the solar cell coating system according to the invention 1 . 1' ,
7. 7. Diffusion 119 of phosphorus in the front of the solar cells in a diffusion furnace, with a phosphorus silicate glass layer ( PSG ) is formed (prior art), and at the same time the Si layer also crystallizes on the back and the boron-p doping is also activated (new),
8. 8. Wet chemical removal 120 the PSG layer from the front (prior art), the protective layer on the back also being removed at the same time (new) in the context of the present invention,
9. 9. PECVD deposits 121-123 a passivation and anti-reflection layer on the back, consisting of an AlO _x and an SiN _x : H layer, and an SiN _x : H - passivation and anti-reflection layer on the front (prior art),
10. 10. Screen printing 124 of metal pastes on the front and the back (state of the art),
11. 11. Making metallic contacts 125 from the metal pastes in a contact firing step, in which the metal pastes are fired through the passivation and anti-reflection layers and electrical contacts are made with the solar cell (prior art), the contacts being passivated on the back due to the presence of the boundary layer (new).

The procedural steps 1-3 and 7-11 are identical or modified process steps compared to the prior art. These process steps can be carried out with the same plant technology that is also used in the prior art. In the method or in the production line according to the invention, only a new system is used, namely a solar cell coating system according to the invention 1 , 1' to carry out the procedural steps 4-6 . In the exemplary embodiment presented, the solar wafers are used to carry out the steps 4-6 with the Back side up in closed substrate nests of a plate-shaped substrate carrier. The solar cell coating system is an inline system. The substrate carriers loaded with solar wafers 7 pass through various processing areas of the solar cell coating system 1 , 1' .

In an oxidation area for performing the fourth step, a gas shower head with a plurality of gas outlet holes provides an ozone-containing gas as an oxidizing agent for the oxidation of the tempered solar wafers. The thickness of the boundary layer formed by oxidation can be controlled by the throughput speed, the size of the gas shower head, the temperature and the pressure or gas partial pressures. In the exemplary embodiment presented, the thickness of the boundary oxide is approximately 2 nm. In other exemplary embodiments, other thicknesses are set in the range between 1 nm and 5 nm. The ozone is generated in an ozone generator arranged directly in front of the gas shower head, in which ozone is generated from oxygen. In other exemplary embodiments, ozone is generated differently, for example by means of a plasma, or other oxidizing agents are used, for example O ₂ , N ₂ O or H ₂ O.

The Si layer is in 5 . Step in the exemplary embodiment presented is separated from linear microwave plasma sources in a chamber that can be separated from adjacent chambers by chamber valves. Boron-containing silicon layers (Si) are deposited from a gas mixture containing silane and diborane. To limit the boron dopant in the solar cell coating system, the chamber valves of the Si deposition chamber are only opened when the diborane feed is switched off in order to pass substrate carriers.

The protective layer in the 6th step of the method is an 80 nm thick SiON layer in the exemplary embodiment presented. In a first part of the production of the SiON layer, the surface of the Si layer to be protected is nitrided in an NH ₃ atmosphere. In further sub-steps, further layer thickness is deposited using the precursors silane (SiH ₄ ), ammonia (NH ₃ ) and laughing gas (N ₂ O) and from linear microwave plasma sources using PECVD. During the course of the SiON coating, the ammonia portion decreases and the laughing gas portion increases, so that the SiON layer is almost a silicon nitride at the boundary with the silicon layer and almost a silicon oxide layer on its surface. Too thin layers do not offer adequate protection against diffusion through the layer or through diffusion paths in the layer. Too thick layers have disadvantages such as increased costs for the later removal of the layers from the solar wafers. In other exemplary embodiments, the protective layer consists of a different material, for example SiN _x , SiO _x , SiC _x O _y N _z , AlO _x, or the protective layer is deposited using another method, for example using an HF-PECVD or an ALD deposition method.

• 1. Bereitstellen eines n-dotierten Solarwafers und nasschemisches Überätzen sowohl der Vorderseite als auch der Rückseite zur Entfernung von beim Sägen des Solarwafers entstandenen Sägeschäden (Stand der Technik, saw demage etch - SDE),
• 2. nasschemisches beidseitiges Texturieren 111 der Vorderseite und der Rückseite und anschließendes Reinigen 112 (Stand der Technik),
• 3. Diffusion 113 von Bor in die Solarzellen-Vorderseiten und Rückseiten in einem Diffusionsofen, wobei jeweils eine Bor-Silikat-Glas-Schicht (BSG) ausgebildet wird (Stand der Technik),
• 4. nasschemisches Entfernen 114 der BSG-Schichten von der Vorderseite und der Rückseite und des mit Bor dotierten Rückseiten-Oberflächenbereichs (single side etch SSE) und anschließender Reinigung 115 (Stand der Technik),
• 5. Herstellen einer Grenzschicht, nämlich einer Rückseitengrenzschicht durch Oxidieren 116 der Rückseite des Solarwafers in einem ozonhaltigen Gasgemisch in der erfindungsgemäßen Solarzellenbeschichtungsanlage 1, 1', konkret in einer Inline-Durchlaufanlage mit Substratträgern 7 für matrixartig von dem Substratträger aufgenommene Substrate, wobei in einem Oxidationsbereich der inline-Durchlaufanlage die Oxidschicht auf der Rückseite der Solarwafer beim Vorbeifahren an einem linearen Ozon-Duschkopf 5 gebildet wird,
• 6. PECVD-Abscheiden 117 einer insitu-Phosphor-dotierten Si-Schicht auf der Rückseite der Solarwafer in der erfindungsgemäßen Solarzellenbeschichtungsanlage 1, 1', wobei die Si-Schicht von Mikrowellenplasmaquellen 8 auf vorbeifahrende Substratträger 7 abgeschieden wird,
• 7. PECVD- Abscheiden 119 einer aus SiON bestehenden Schutzschicht auf der Phosphor-dotierten Si Schicht, wobei die Siliziumschicht eine weitgehend amorphe Morphologie mit wenig kristallinem Anteil hat, sie also näherungsweise eine a-Si Schicht ist,
• 8. Kristallisieren 119 der Si-Schicht in einem Offen bei wenigstens 800°C,
• 9. Entfernen 120 der Schutzschicht auf der Rückseite und Reinigen der Vorderseite,
• 10. PECVD-Abscheiden 121, 122 einer Passivierungs- und einer Antireflexionsschicht auf der Vorderseite und PECVD-Abscheiden 123 einer Passivierungs- und Reflexionsschicht auf der Rückseite,
• 10. Siebdrucken 124 von Metallpasten auf der Vorderseite und der Rückseite,
• 11. Herstellen von metallischen Kontakten aus den Metallpasten in einem Kontaktfeuerungsschritt 125, in welchem die Metallpasten durch die Passivierungs- und Antireflexionsschichten durchgefeuert und elektrische Kontakte mit der Solarzelle hergestellt werden, wobei auf der Rückseite infolge des Vorhandenseins der Grenzschicht die Kontakte passivierte Kontrakte sind.

This in 5 The illustrated second exemplary embodiment relates to a method according to the invention 102 for the production of monofacial PERT solar cells with passivated back contacts, a corresponding solar cell production line and a corresponding solar cell coating system that can be used in the process 1 , 1' . The method according to this exemplary embodiment has the following steps:

• 1. Provision of an n-doped solar wafer and wet chemical overetching of both the front side and the back side to remove saw damage caused by sawing the solar wafer (prior art, saw demage etch - SDE),
• 2. Wet chemical texturing on both sides 111 the front and back and then cleaning 112 (State of the art),
• 3. Diffusion 113 boron into the front and back of the solar cells in a diffusion furnace, each with a boron silicate glass layer ( BSG ) is trained (state of the art),
• 4. Wet chemical removal 114 the BSG layers from the front and the back and the boron-doped back surface area (single side etch SSE) and subsequent cleaning 115 (State of the art),
• 5 . Forming a boundary layer, namely a rear boundary layer by oxidation 116 the back of the solar wafer in an ozone-containing gas mixture in the solar cell coating system according to the invention 1 , 1' , specifically in an inline continuous system with substrate carriers 7 for substrates received in a matrix-like manner by the substrate carrier, the oxide layer on the back of the solar wafer in an oxidation area of the inline continuous system as it passes a linear ozone shower head 5 is formed
• 6. PECVD deposition 117 an in-situ phosphorus-doped Si layer on the back of the solar wafer in the solar cell coating system according to the invention 1 , 1' , wherein the Si layer from microwave plasma sources 8th on passing substrate carriers 7 is deposited
• 7. PECVD deposition 119 a protective layer made of SiON on the phosphorus-doped Si layer, the silicon layer having a largely amorphous morphology with little has a crystalline component, i.e. it is approximately an a-Si layer,
• 8. Crystallize 119 the Si layer in an open at at least 800 ° C,
• 9. Remove 120 the protective layer on the back and cleaning the front,
• 10. PECVD deposition 121 , 122 a passivation and an anti-reflective layer on the front and PECVD deposition 123 a passivation and reflection layer on the back,
• 10. Screen printing 124 of metal pastes on the front and back,
• 11. Production of metallic contacts from the metal pastes in one contact firing step 125 , in which the metal pastes are fired through the passivation and anti-reflection layers and electrical contacts are made with the solar cell, the contacts being passivated contracts on the back due to the presence of the boundary layer.

The procedural steps 1-4 and 10-11 are identical or modified process steps compared to the prior art. These process steps can be carried out with the same plant technology that is also used in the prior art. In the method or in the production line according to the invention, only two new systems are used, namely a solar cell coating system according to the invention 1 , 1' to carry out the procedural steps 5 . - 7th or 116-118 in 4th , as well as the crystallization furnace for performing the step 119 . The crystallization of the deposited silicon layer in a separate high-temperature step has the advantage that the crystallization can be optimized separately, this advantage outweighing the low additional costs of the furnace. In the exemplary embodiment presented, they become solar wafers for carrying out the steps 5-7 with the back up in closed substrate nests of a plate-shaped substrate carrier 7 inserted. (In other exemplary embodiments, the rear sides rest on small hooks of substrate carriers and the rear sides are oriented downwards.) The solar cell coating system is an inline system. The substrate carriers loaded with solar wafers 7 pass through various processing areas of the solar cell coating system 1 , 1' .

The Si layer is in the fifth step in the exemplary embodiment presented with linear microwave plasma sources 8th manufactured as in the in 2nd are outlined. In other exemplary embodiments, the Si layer is instead in the same coating chambers or coating areas arranged one behind the other 3 ' (see. 3rd ) deposited, which are loaded in the same loading cycles and unloaded in the same unloading cycles. Sometimes only three of the four coating chambers 3 ' used for coatings and the fourth multi-layer coating chamber 3 ' is cleaned in the coating cycle. In the Si coating chambers 3 ' of the exemplary embodiment shown and also in exemplary embodiments not shown, in situ phosphorus-doped silicon layers (n ⁺ -Si) are deposited from a gas mixture containing silane and phosphine, each of which generates an electrostatic back surface field (BSF).

The protective layer in the crotch 7 In the exemplary embodiment presented, the method is a layer stack of an ultra-thin Si ₃ N ₄ starting layer formed by plasma nitriding and an 80 nm thick SiO _x N _y layer, which is produced using the precursors silane (SiH ₄ ), ammonia (NH ₃ ) and Nitrous oxide (N ₂ O) is separated by HF-PECVD.

1. 1. Bereitstellen eines Solarwafers und nasschemisches Überätzen 110 sowohl der Vorderseite als auch der Rückseite zur Entfernung von beim Sägen des Solarwafers entstandenen Sägeschäden. (Stand der Technik),
2. 2. nasschemisches beidseitiges Texturieren 111 der Vorderseite und der Rückseite (Stand der Technik),
3. 3. Reinigung 112 beidseitig (Stand der Technik),
4. 4. Gleichzeitiges Herstellen von zwei Grenzschichten 116, nämlich einer Rückseitengrenzschicht durch Oxidation der Rückseite des Solarwafers und einer Vorderseitengrenzschicht durch Oxidation der Vorderseite des Solarwafers in einem ozonhaltigen Gasgemisch in der erfindungsgemäßen Solarzellenbeschichtungsanlage, konkret einer inline-Durchlaufanlage mit Substratträgern für matrixartig von dem Substratträger aufgenommene Substrate,
5. 5. PECVD-Abscheidung 117 mit insitu-Dotierung bzw. Dotierstoffeinbringung einer Bor-enthaltenden Si Schicht auf der Solarwafer-Rückseite,
6. 6. PECVD-Abscheidung 118 einer aus SiON bestehenden Schutzschicht auf der Bor-haltigen Si Schicht auf den beschichteten Rückseiten der Solarwafer,
7. 7. Umladen 126 der Substrate auf andere Substratträger,
8. 8. PECVD-Abscheiden 127 einer Phosphor enthaltenden Si-Schicht auf der Vorderseite des Solarwafers,
9. 9. PECVD-Abscheiden einer aus SiON 128 bestehenden Schutzschicht auf der Phosphor enthaltenden a-Si Schicht auf den Vorderseiten der Solarwafer,
10. 10. Temperaturbehandlung 119 in einem Ofen (Diffusionsofen aus dem Stand der Technik) zur Aktivierung der Phosphor-Dotierung in den Si-Schichten auf den Solarwafer-Vorderseiten und zur Aktivierung der Bor-Dotierung in den Si-Schichten auf den Solarzellen-Rückseiten, wobei gleichzeitig auf der Vorderseite und der Rückseite auch die Si-Schichten kristallisiert (zu c-Si-Schichten) werden,
11. 11. nasschemisches Entfernen der Schutzschichten 120,
12. 12. PECVD-Abscheidungen 121 - 123 einer Passivierungs- und Antireflexionsschicht auf der Rückseite, bestehend aus einer AlO_x und einer SiN_x:H Schicht, und einer SiN_x:H Schicht - Passivierungs- und Antireflexionsschicht auf der Vorderseite,
13. 13. Siebdrucken 124 von Metallisierungspasten auf der Vorderseite und der Rückseite,
14. 14. Herstellen von metallischen Kontakten 125 aus den Metallpasten in einem Kontaktfeuerungsschritt, in welchem die Metallpasten durch die Passivierungs- und Antireflexionsschichten durchgefeuert und elektrische Kontakte mit den c-Si-Schichten der Solarzelle hergestellt werden, wobei sowohl auf der Rückseite als auch auf der Vorderseite infolge des Vorhandenseins der Grenzschichten die Kontakte passivierte Kontrakte sind.

in the 3rd . Embodiment that in 6 A method is illustrated below 103 for the production of bifacial PERC solar cells with passivated rear contacts and passivated front contacts. A corresponding solar cell production line and a corresponding solar cell coating system that can be used in the process are also used in this context 1 , 1' presented. The method according to the third exemplary embodiment has the following steps:

1. 1. Provision of a solar wafer and wet chemical overetching 110 Both the front and the back for removing saw damage caused by sawing the solar wafer. (State of the art),
2. 2. Wet chemical texturing on both sides 111 the front and the back (state of the art),
3. 3. Cleaning 112 on both sides (state of the art),
4. 4. Simultaneous creation of two boundary layers 116 , namely a rear boundary layer by oxidation of the rear side of the solar wafer and a front boundary layer by oxidation of the front side of the solar wafer in an ozone-containing gas mixture in the solar cell coating system according to the invention, specifically an inline continuous system with substrate carriers for substrates taken up in matrix form by the substrate carrier,
5. 5. PECVD deposition 117 with in-situ doping or dopant introduction of a boron-containing Si layer on the back of the solar wafer,
6. 6. PECVD deposition 118 a protective layer made of SiON on the boron-containing Si Layer on the coated backs of the solar wafers,
7. 7. Reload 126 the substrates on other substrate carriers,
8. 8. PECVD deposition 127 a Si layer containing phosphorus on the front side of the solar wafer,
9. 9. PECVD deposition of a protective layer consisting of SiON 128 on the phosphorus-containing a-Si layer on the front sides of the solar wafers,
10. 10. Temperature treatment 119 in a furnace (diffusion furnace from the prior art) for activating the phosphorus doping in the Si layers on the solar wafer front sides and for activating the boron doping in the Si layers on the rear side of the solar cells, simultaneously on the front side and the rear side also crystallizes the Si layers (to c-Si layers),
11. 11. Wet chemical removal of the protective layers 120 ,
12. 12. PECVD deposits 121-123 a passivation and anti-reflection layer on the back, consisting of an AlO _x and an SiN _x : H layer, and an SiN _x : H layer - passivation and anti-reflection layer on the front,
13. 13. Screen printing 124 of metallization pastes on the front and the back,
14. 14. Making metallic contacts 125 from the metal pastes in a contact firing step, in which the metal pastes are fired through the passivation and antireflection layers and electrical contacts are made with the c-Si layers of the solar cell, the contacts on both the back and the front due to the presence of the boundary layers are passivated contracts.

In this exemplary embodiment, the method steps are in particular 5-9 new compared to the state of the art. With the Si deposits in the steps 5 and 8th with simultaneous introduction of dopant (in-situ doping), it is essential that the deposits and dopant spreads remain locally restricted to the chambers or areas provided for this purpose. In the specified exemplary embodiment, the carry-over of dopants into other coating chambers by the reloading 126 achieved on substrate carriers dedicated to the dopant. Instead of the in situ doping, in other exemplary embodiments undoped Si layers and doping source layers thereon, for example BSG or PSG , deposited, so that in a subsequent diffusion step at sufficiently high temperatures the dopants diffuse from the doping source layer into the Si layer. The doping source layers are here part of the protective layers designed as multilayer or gradient layers. In further exemplary embodiments, dopings are introduced over the entire surface or partially over masks by ion implantation into undoped deposited Si layers. In further exemplary embodiments, the same substrate carriers are used for both differently doped Si deposits. This is made possible by the deposits in multi-layer coating chambers, in which, in addition to the Si layer, the protective layer is also deposited, the protective layer being covered with doped Si-coated surfaces.

The exemplary embodiments presented are to be understood as examples not restrictive of the invention and not as a definition of the invention thereon. The invention also encompasses non-explicit alternatives defined by the person skilled in the art from the present disclosure and his specialist knowledge. Options that are described randomly one after the other are to be understood as separate options, not as a mandatory combination of features.

Reference list

1, 1 '

Solar cell coating system

2nd

Boundary layer manufacturing area

3, 3 '

Si separation area or PECVD chamber with Si separation area

4th

Protective layer deposition area

5

Shower head

6

Ozone generator

7

Substrate carrier

8, 9

Microwave plasma source for silicon deposition or protective layer deposition

10th

Silane connection

11

Phosphine connection

12th

Ammonia connection

13

Nitrous oxide connection

14

PECVD parallel plate arrangement

15

Means for in-situ cleaning

16

Loading chamber

17th

Transfer chamber

18th

Unloading chamber

101, 102, 103

Process for the production of crystalline silicon-based solar cells

110

wet chemical removal of saw damage

111

Texturing

112

Clean

113

Doping by diffusion

114

Removing layers of glass ( BSG or PSG )

115

Clean

116

Establishing at least one boundary layer

117, 127

Deposit a Si layer

118, 128

Deposit a protective layer

119

Crystallize

120

Clean + remove layers on Si

121, 122, 123

Deposition of passivation and anti-reflection or reflection layers

124

Screen printing of metallization pastes

125

Manufacture of metallic contacts through contact fires

126

Reloading on other substrate carriers

QUOTES INCLUDE IN THE DESCRIPTION

This list of documents listed by the applicant has been generated automatically and is only included for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102013219564 A1 [0005]

Claims (16)

Solar cell coating system (1, 1 ') for the production of thin layers on a first solar cell side and / or a second solar cell side of crystalline silicon solar wafers with a throughput of at least 2000 solar wafers per hour (2000 W / h), characterized in that the Solar cell coating system is designed for the production: - at least one thin boundary layer made of a dielectric material on the first solar cell side and / or the second solar cell side, the boundary layer permitting and little obstructing an electrical current flow through the boundary layer, in particular a tunnel current flow, - at least one doped or undoped in particular amorphous silicon layer on the boundary layer, and - at least one protective layer on the at least one silicon layer, the boundary layer and the silicon layer and the protective layer being able to be produced within the solar cell coating system without the silicon layer larwafer leave the solar cell coating system in the meantime. Solar cell coating system (1, 1 ') after Claim 1 , characterized in that the solar cell coating system has: - at least one boundary layer production area (2), in which the thin boundary layer can be produced from a dielectric material, the boundary layer allowing and little impedance to an electrical current flow through the boundary layer, in particular a tunnel current flow , - at least one Si deposition area (3), in which the doped or undoped, in particular amorphous, silicon layer can be deposited on the boundary layer, and - at least one protective layer deposition area (4), in which the protective layer is directly on the silicon layer or on one previously the doping layer deposited on the silicon layer can be deposited, the boundary layer and the silicon layer and the protective layer being able to be produced in one pass through the solar cell coating system (1, 1 '). Solar cell coating system (1, 1 ') after Claim 1 or 2nd , characterized in that the solar cell coating system is equipped to produce the boundary layer on both sides in the boundary layer manufacturing area (2) on the first solar cell side and the second solar cell side, and an Si coating of a first doping type on the first solar cell side and on the second To deposit a Si coating of a second doping type opposite to the first doping type on the solar cell side. Solar cell coating system (1, 1 ') after Claim 3 , characterized in that the boundary layer production area (2) is an oxidation area in which in particular a surface layer of the silicon solar wafer is oxidized to form a silicon oxide layer, the oxidation area having a shower head (5) through which an O ₃ -containing gas can flow, which is powered by an ozone source. Solar cell coating system (1, 1 ') after Claim 4 , characterized in that the ozone source is an external ozone generator (6). Solar cell coating system (1, 1 ') at least after Claim 2 , characterized in that the boundary layer production area (2) is an oxidation area and the oxidation area has a microwave plasma source and a gas connection for a gas containing O ₂ , O ₃ or N ₂ O. Solar cell coating system (1, 1 ') after Claim 2 , characterized in that the solar cell coating system (1) is an inline system in which at least the boundary layer production area (2), the Si deposition area (3) and the protective layer deposition area (4) are lined up in a line. Solar cell coating system (1, 1 ') after Claim 2 , characterized in that the Si deposition area (3) is a lockable PECVD chamber (3 ') with a PECVD parallel plate arrangement (14) contained therein which can be operated at RF frequency, the PECVD chamber (3') being a silane connection (10) and a diborane connection or a silane (10) and a phosphine connection (11). Solar cell coating system (1, 1 ') after Claim 2 , characterized in that the protective layer deposition area (4) has at least one microwave plasma source (9) and in particular gas connections of silane (10), ammonia (12), laughing gas (13), carbon dioxide and / or methane in order to To be able to deposit silicon nitride, silicon oxynitride or silicon carbonitride layer. Solar cell coating system (1, 1 ') after Claim 1 , characterized in that the solar cell coating system (1, 1 ') has at least one multi-layer production area in which at least two of the following three layers can be produced one after the other in time: the thin boundary layer made of a dielectric material, the doped or undoped, in particular amorphous silicon layer, and - the protective layer. Solar cell coating system (1, 1 ') after Claim 2 or 10th , characterized in that the solar cell coating system (1, 1 ') has at least two coating areas (3, 3', 4) or multi-layer manufacturing areas which can be used simultaneously for layer production. Solar cell coating system (1, 1 ') after Claim 11 , characterized in that the coating area (3, 3 ', 4) or the multi-layer manufacturing area is in each case a lockable vacuum chamber and the solar cell coating system is an inline substrate processing system with at least two vacuum chambers and a transport device for two-dimensional substrate carriers (7) The substrate carrier (7) can be moved by the transport device in cycles between transport cycles between different chambers of the solar cell coating system (1, 1 '). Solar cell coating system (1, 1 ') after Claim 11 , characterized in that the solar cell coating system is a substrate processing system with at least two vacuum chambers and a transport device for the cyclical movement of three-dimensional substrate carriers. Solar cell coating system (1, 1 ') after Claim 12 or 13 , characterized in that the vacuum chambers are equipped with means for in-situ cleaning (15). Solar cell production line for the production of solar cells from solar wafers, in which an oppositely doped layer is diffused into the p- or n-doped solar wafer or an oppositely doped layer is formed on the p- or n-doped solar wafer, solar wafers with passivation layers and at least one Antireflection layer are coated and the solar wafers are equipped with contacts for the external electrical connection to form solar cells, characterized in that the solar cell production line also has at least one solar cell coating system (1, 1 ') compared to a conventional solar cell production line from the prior art. ) according to at least one of the Claims 1 - 14 has in order to realize at least one passivated contact of the solar cell with this solar cell coating system (1, 1 '). Method (101, 102, 103) for producing crystalline silicon-based solar cells, each with a crystalline silicon substrate, at least one p-doped region and at least one n-doped region, metallic contacts on the p-doped region and the n-doped region , at least one dielectric boundary layer arranged between the contact and the silicon substrate and having a thickness of less than 5 nm, the boundary layer, with the small thickness, permitting and little hampering an electrical current flow, in particular a tunnel current flow, the method (101, 102, 103) which has the following method steps, in which: in at least one boundary layer production step 116, on at least one side of the substrate, an interface layer is produced from a dielectric material on the first solar cell side and / or the second solar cell side, the interface layer being produced in particular by oxidation of silicon to silicon oxide - In a Si deposition step 117, 127, in particular a-Si deposition step, preferably immediately following the boundary layer production step 116, on the one-sided boundary layer, a dopant-containing PECVD Si deposition of an insitu-doped Si layer or in the case of a two-sided boundary layer PECVD Si deposition of an in situ-doped Si layer and / or a one-sided, undoped PECVD Si deposition of an undoped Si layer takes place on at least one side, - in a protective layer deposition step 118, 128, preferably immediately following, at least one one-sided protective layer on the dopant-containing layer Si layer is deposited, - in at least one high-temperature step 113, 119 at temperatures above 800 ° C., both a dopant diffuses into the silicon substrate or into the previously undoped deposited Si layer and / or the doping in the insitu-doped Si layer is activated will be the one Si-Sc as well hicht or both Si layers are crystallized to nanocrystalline or microcrystalline Si layers with activated doping, all of the process steps listed with a layer production or layer deposition in at least one solar cell coating system (1, 1 ') according to at least one of the Claims 1 - 14 be performed.

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