CH713453A1 - Process for producing a substrate with a boron-doped surface. - Google Patents

Abstract

A process for the production of a substrate having at least one boron doped surface, at least in a subarea, comprising the following steps: providing a substrate which is introduced into a vacuum treatment plant in a preparatory step and treated there with a boron-containing first layer by means of a PVD or paCVD process has been; Annealing the substrate to diffuse the boron into the surface. Wafer with a boron-containing surface, prepared by such a process. Furthermore, a sputtering method is claimed for depositing a first boron-containing layer or a layer system on a substrate which is arranged in a vacuum treatment chamber with respect to a boron-containing support, wherein the target comprises a covalent boron compound and the sputtering process by applying a high-frequency voltage in an inert gas and / or nitrogen atmosphere takes place. A wafer having a first surface-mounted layer system comprising at least one boron-containing layer produced by the sputtering method.

Description

Description: The present application relates to a method for producing a substrate having a boron doped surface according to claim 1, to a wafer according to claim 8 and 22, to a sputtering method according to claim 10 for depositing a boron-containing layer on a substrate, and to a vacuum treatment system according to claim 29 for performing the sputtering method.

Background Art Silicon substrates can be made for a variety of applications, for example, as silicon substrates in the form of a wafer or for a thin film solar cell or for other electronic devices. In a part or in the entire region of at least one surface of the silicon substrate, regions or partial regions are generated for this purpose which differ with regard to the dopant elements and / or dopant concentrations introduced therein from neighboring regions or from regions further away from the surface. Here, dopants such as e.g. Phosphorus, the negative charges, i. Electrons, release (n-type dopants). Alternatively, dopants such as e.g. Boron, the positive charges, i. Holes, release (p-type dopants). Due to the associated formation of an electrical potential, different desired functions can be formed in the substrate, depending on the arrangement.

For example, solar cells generally include a silicon substrate that may be predoped (eg, slightly p-doped) with an n-doped n + region introduced on the surface of the front side. An additional p-doped p + region can be provided on the rear side.

The production of doped regions, for example, by applying a phosphorpentoxidhaltigen silicon dioxide solutions, by spin coating or Spin method), in which a corresponding solution is applied centrally on a surface of the wafer and then distributed by rotation. In the following, the substrate is dried at an increased speed and / or thermally. The procedure is repeated for the opposite side with a complementary, for example boron oxide-containing silicon dioxide solution, and then the wafer coated on both sides is tempered, for example, at 1010 ° in order to form the diffusion regions on both sides of the wafer. In WO 2011/061 693 A2 as well as in WO 2011/061 694 A2 u.a. the production of a solar cell with a method as described above in detail. It is important to ensure that the respective solutions do not contaminate parts of the opposite surface.

Corresponding spin processes require a large number of process steps and are critical with respect to the choice and compliance with the parameters, such as concentration ratios in the solutions, rotational speed and layer thickness produced, etc.

DISCLOSURE AND EMBODIMENTS It is therefore an object of the present method to provide a method that is more reproducible than the prior art for producing a boron-doped surface of a planar, ie substantially two-dimensional semiconductor substrate. Furthermore, this is intended to reduce the number of process steps and to the greatest extent possible to dispense with the use of critical chemicals, in particular under atmospheric conditions.

Such a method for producing a boron-doped surface, at least in a partial area, comprises the following steps: Providing a substrate that is introduced in a preliminary step in a vacuum treatment plant and there, using a PVD or a paCVD method with a drill-containing first Layer, and - annealing the substrate to diffuse the boron into the surface.

The provision of the substrate may comprise the following steps: introducing the substrate into a vacuum treatment plant and pumping out the vacuum treatment plant, arranging the substrate in a coating chamber of the vacuum treatment plant and coating the substrate by means of a PVD or a paCVD process a boron-containing first layer in a coating chamber of the vacuum treatment plant.

The tempering can be carried out in an annealing chamber of the vacuum treatment plant or in a tempering outside the vacuum treatment plant.

Between the coating and tempering, a silicon-containing second layer may additionally be applied to the drill-containing first layer in a coating chamber of the vacuum treatment plant by means of a PVD or paCVD process.

The substrate may be a wafer, in particular a silicon wafer, which is coated on a first surface, wherein a second, the first surface opposite surface during the application of the first and / or the second layer, is protected against a coating. Such protection can be ensured in known manner by holding a vacuum system or, for example, by flying up the surface of the substrate which is not to be coated, for example onto a chuck of a coating installation.

The wafer may in principle be pre-coated on the second surface with a phosphorus-containing third layer or, alternatively, post-coated before annealing. In principle, the preceding coating is to be preferred, since in this case the wafers, for example, can also be tempered directly in the vacuum treatment plant.

As a method for applying the first and / or the second layer, a PVD method, preferably a sputtering method, in particular a magnetron sputtering method can be used.

The invention also includes a wafer or a solar cell with a boron doped surface which was prepared by a method as described above. In particular, so-called bifacial solar cell can be produced, which absorb light on both the front and on the back or use for power generation.

For producing the first boron-containing layer or a boron-containing layer system on a planar semiconductor substrate, a sputtering process is particularly suitable in which the substrate is arranged in a coating chamber of a va-kuumbbehandlungsanlage against a boron-containing target, wherein the target comprises a covalent boron compound and this sputtering the application of a high-frequency voltage in an at least noble gas-containing and / or nitrogen-containing atmosphere. Under covalent here a connection of the boron with another element is considered, in which the difference in the electronegativity according to Pauling between boron and the second compound constituting element <1.1, in particular <1. The target advantageously consists of at least 99.0%, in particular 99.9%, of the boron compound to be sputtered, for example of boron nitride (BN). With such a sputtering method, a boron nitride layer can be deposited, wherein a nitrogen-containing gas, in particular nitrogen, can be used to adjust the B / N ratio. Alternatively or additionally, a BOxNy layer can be deposited by sputtering the boron-containing target in an oxygen-containing atmosphere. Preferably, the sputtering atmosphere for the deposition of the BOxNy layer contains at least oxygen and a noble gas. Thus, with the sputtering method for producing a drilling layer system, first a BN layer by sputtering the target containing boron in an at least noble gas and / or nitrogen-containing atmosphere and then a BOxNy layer by sputtering the boron-containing target in an oxygen-containing, or additionally nitrogen-containing atmosphere are deposited, wherein in the last step preferably in addition to oxygen, a noble gas is used. Suitable noble gases are helium, neon, krypton, but especially argon. Metering of nitrogen, for example as N 2 gas or N x O y gas (e.g., N 2 O, NO or NO 2) may also be used in this process step to control, for example, a graded N / O ratio. The target may comprise boron nitride, but in particular consist of boron nitride. An alternative compound with little difference in electronegativity is boron carbide (BC). The layer thickness is set independently of the method between 1 nm and 6 nm, preferably between 2 nm and 5 nm, to which the sputtering method is particularly suitable due to the high image fidelity of the nature of the coated surface and the low number of defects. By adjusting the corresponding layer thicknesses, the sheet resistance after annealing is also set. Thus, after annealing the wafer or solar cells coated therewith, a sheet resistance between 30 Ω and 100 Ω is set, which was measured using the four-point probe resistance measurement method.

In addition to the boron-containing layer, or the first boron-containing layer system, a second silicon-containing layer, or a second silicon-containing layer system can be applied, wherein the substrate disposed in a coating chamber of the vacuum treatment plant against a silicon-containing target and this in an at least noble gas-containing and / or reactive gas-containing atmosphere is sputtered. In addition to the reactive gases mentioned above, in particular nitrogen and / or oxygen can be used here. In this case, a silicon, a silicon nitride, a silicon oxide and / or a silicon oxynitride layer can be deposited. Preferably, a silicon nitride layer, in particular a silicon oxide layer is deposited. Silicon, silicon nitride or silicon oxide can be sputtered off as the target material. The layer thickness of the second layer system can be adjusted in a 10 to 20 nm range.

The power for operating the targets in sputtering can be set for the different target materials, for example, for a target with 300mm diameter, in a range of 0.1 to 10 kW while preferably in a range of 2 to 4 kW, from which also derive the services to be set per area unit for other target dimensions. The targets are operated at a frequency between and including 2 to 30 MHz inclusive, preferably between 10 to 15 inclusive, more preferably 13.56 MHz.

The present invention also includes a wafer having a layer system applied to a first side of the wafer, comprising at least one boron-containing first layer deposited directly on the first surface and deposited according to the method described above and in the following examples. The first layer may comprise a boron carbide (BC) layer, but preferably a boron nitride (BN) layer and / or a boron oxide (BOxNy) layer. In a preferred embodiment, the first layer system is a BN layer or consists of a BN layer with a BOxNy layer deposited thereon. The layer transition in the first layer system, i. between BN and BOxNy layer may be formed stepwise or preferably gradiiert.

In a further embodiment of the invention, the layer system applied to the wafer comprises a silicon-containing second layer, which is applied to an outer side of the first layer facing away from the wafer. The second layer may be a silicon layer, but preferably a silicon oxide or a silicon nitride layer, also the use of mixed layers or of graded layers which, for example, from a nitride region adjacent to the boron-containing first layer to an oxidic region formed on the surface formed between formed oxydnitridischen silicon layer is formed. The second layer may therefore also comprise a multilayer with at least one silicon layer or / and a silicon oxide layer and / or a silicon nitride layer, wherein the layer transitions may be formed with respect to their elemental composition into one another or stepwise. The wafer can be designed as a solar cell, in particular as a bifacial solar cell.

The final annealing of the substrates, for example, the silicon wafer, takes place at the temperatures comprising the limiting values of 850 ° to 1200 ° C, preferably at 950 ° <Ttemper 1050 ° C. For example, wafers coated as described above and described in more detail below were treated at a temperature of 1025 ° C for 30 minutes in a nitrogen atmosphere. At corresponding higher temperatures, a somewhat shorter coating time of up to about 20 minutes, but at least 15 minutes can be selected. If the process is to be controlled in a controlled manner and at the lowest possible induced thermal stress, annealing times of up to approximately one hour at a correspondingly lower temperature can also be provided.

The present invention also encompasses a vacuum treatment plant, which is designed, for example, as a coating system with a plurality of process chambers and is suitable for coating a wafer according to the invention and producing a layer system according to the invention. Such a vacuum treatment plant comprises at least one lock chamber for introducing and / or discharging one or more substrates into the vacuum treatment system and at least one first coating chamber comprising at least one boron carbide (BC) target or preferably a boron nitride (BN) target. In this case, the vacuum treatment system downstream of the at least one first coating chamber may comprise at least one second coating chamber containing at least one silicon target, or at least one silicon nitride (SiN) target, a silicon oxide (SiO 2) target but preferably a silicon (Si) target includes. The vacuum treatment plant, which is preferably designed as a multi-chamber coating system, may already include means for pretreatment of the substrate, such as a heater and / or an etching apparatus, in the lock chamber. In addition, at least one pretreatment chamber with a corresponding heating device and / or etching device can be provided between the lock chamber and the first coating chamber. As heating device, for example, known radiant heaters and / or heated substrate holder or bearing surfaces, such as a heated chuck come into question. As an etching device can serve, for example, a radio frequency acted upon substrate holder. Alternatively or additionally, a gas inlet may be provided for an etching gas. Thus, in order to achieve particularly short cycle times, for example, in the lock chamber and a first pretreatment chamber, the substrate or substrates are heated and thus degassed, and the substrate or substrates are etched in a subsequent second pretreatment chamber.

In one embodiment of the vacuum treatment plant, at least one or two pretreatment chambers are arranged downstream of the lock chamber, followed by one or two first coating chambers, each having at least one boron-containing target, followed by one or two second coating chambers each having at least one silicon-containing target from the lock chamber or another lock chamber. The chambers of the vacuum treatment plant are arranged either circumferentially with respect to a path from the lock chamber either linearly or around an installation center. With circumferential arrangement and thus closed path from the lock chamber back to the lock chamber can be dispensed with a second lock chamber for discharging the substrates from the system, since the lock chamber can take both functions so input and output of the substrates. In a linear arrangement, the provision of a second lock chamber is mandatory. The provision of a second lock chamber can also be advantageous in the case of a closed, for example circular or polygonal, ie polyhedral, arrangement of the chambers of the vacuum treatment system, if, for example, very short cycle times between the chambers are to be achieved. Thus, for example, the input-side lock chamber during the entire cycle time for a possibly supported by a heating degassing and / or an etching process can be used. In addition, the substrate or the wafer can also be additionally heated on the way between the chambers, in particular between the lock chamber and the pretreatment chamber, or between the pretreatment chambers and the first coating chamber, since the substrates are kept continuously under vacuum.

In the following, the invention will be described by way of example with reference to figures. Figures 1 to 5 show:

1 a circumferential coating system for carrying out a method according to the invention FIG. 2 a linear inline coating system for carrying out the method according to the invention FIG. 3 A wafer surface with a two-layer layer. FIG

FIG. 4 shows a wafer coated on both sides FIG. 5 shows a wafer after tempering The vacuum treatment plant I shown schematically in FIG. 7 consists of a lock chamber S and six process chambers 10 to 60. One or more substrates, in particular wafers In this case, as indicated by the two opposite arrows, by means of a loading and unloading system positioned before or at the installation I, for example, a transport line, not shown here, can be taken from the lock chamber S, brought into the lock chamber and evacuated there, or Conversely, after the process steps have been completed, they are vented in the lock chamber and, in turn, deposited on the transport line by means of the loading and unloading system. This can also take place with a lock chamber S with two each for the only one or. In the lock chamber, in addition to the pumping off, a first heating of the wafer for accelerated degassing may also take place, which is subsequently transferred, for example by means of a carousel 7 along the transport path 7s1, into the first process chamber 10 The wafer is further transported along the transport paths 712 to 76s via the individual process chambers back to the sluice chamber S, preferably clocked, then discharged and deposited again on the transport line.

Alternatively, the system I may be formed with a central handling system 8, which takes over the substrates via the alternative transport path 8SZ from the lock chamber S and after a corresponding, in the case shown a seventh rotation via the transport path 8zi in the first chamber be handed over. The handling system can be designed such that it can also remove and / or return two or more substrates at the same time from lock or process chambers along the alternative transport paths 8SZ, 8Z- |... 86z, 8ZS. Such an alternative arrangement has the advantage that individual chambers or process stations can be skipped more easily, but is more complicated with respect to the mechanics and control, in particular if, for example, all process chambers and lock chambers are to be loaded or unloaded at the same time. In both variants, the substrates are always kept under vacuum from the transfer to the discharge. Advantageously, both lock chamber 5 and individual process chambers 10-60 and carousel 7 or handling system 8, or the corresponding chambers containing the carousel or handling system, not shown here, can be pumped off separately.

Process chamber 10 and 20 may be designed as a pre-treatment chambers in which a degassing of the substrates at, for example. By additional heating elements generated, higher temperatures is performed. In addition, in both or only one chamber, an etching step, for example by an etching device arranged in each case in the chambers, can be carried out. Process chambers 30 to 60 are designed as coating chambers, each having one or more sputtering tare targets 5, 6, wherein process chamber 30 and 40 in the present case at least with a boron, eg. Boron nitride 5 and process chambers 50 and 60 each with at least one silicon-containing, eg Silicon oxide target 6 are equipped for sputter coating the substrates. Coating systems configured in this way are suitable for particularly short cycle or cycle times. Thus, with a treatment time between 1 to 3 seconds in the process chambers 10 to 60 and an intermediate transfer time of about one second, for transferring the respective substrates from one chamber (lock chamber or process chamber) to the next chamber, for example, throughputs of 900, 1200 bis 1800 wafers per hour can be achieved. By means of the process chambers, which are each carried out twice for pretreatment steps and coating steps, it is also possible, for example, to coat thermally sensitive substrates with a correspondingly high throughput. Alternatively, as the skilled person readily apparent, even with more systems, eg. 8, 9, etc., or less, for example. Only 3 process chambers, be configured to the individual process steps, with constant throughput with an even smaller or larger per Process step introduced performance (heating, etching, sputtering) perform.

An alternative, with respect to the functional sequence of the individual process chambers but analogous arrangement for a linear coating system II, Fig. 2. Such a linear coating system II can be installed directly in a production line, the wafer in the lock chamber S 'then introduced the Process chambers 10 to 60 are cycled in a correspondingly timed manner and then discharged again in the lock chamber S. In this case too, additional chambers can be added or chamber omitted, as in the above case, although in principle all coating steps can be carried out in one process chamber However, for reasons of process economics, it is advantageous if a minimal system is provided with at least one lock chamber and two coating chambers, each equipped with a boron nitride or a silicon target, this being when degassing and possibly etching the substrates in a sufficiently short time is already possible in the lock chamber. Otherwise, at least one pretreatment chamber should be provided.

For the production of the layer shown in Fig. 3, a commercial coating system of the company Evatec with the name Solaris S151, that is analogous to the illustrated in Fig. 1 vacuum treatment plant I, is used. For this purpose, a respective BN target with a diameter of 300 mm and a thickness of 6 mm was installed in the coating chambers 30 and 40, and in each case a corresponding target of silicon, silicon oxide or SiN in the coating chambers 50 and 60. Corresponding experiments with different targets in chambers 50 and 60, for example a Si target or a SiN target in chamber 50 and a Si target or a SiO 2 target in chamber 60 were also performed.

The following parameters were set for deposition of the boron-containing layers:

Power of the 13.56 MHz RF supply for the sputter source at 4 kW;

Ar process and purge flow (i.e., argon flow in stand-by mode) each 68 sccm;

Oxygen flux for BOxNy layers: 5-20 sccm (= 10-40%)

The sputtering rates obtained were for BN: 0.56-0.63 nm / s and for BOxNy: 1.28 nm / s.

The sputtering time was determined on the one hand via in-situ measurement of the layer thickness, on the other hand adjusted according to the once determined rates.

The parameters for the deposition of a silicon-containing layer from a silicon target were as follows: power of the DC pulse supply (100 kHz, 1.6 μs sampling rate) for the sputter source at 6.5 kW;

Ar process and purge flow (i.e., argon flow in stand-by mode) each 40 sccm;

Nitrogen flow for SiN layers: 45 sccm (45%) The resulting sputtering rates for SiN were 3.2 nm / s.

The substrates used were 5 "(inch / inch) n-pre-doped (n-type) silicon wafers of which the surface was first stripped of 10 μm of material, and both surfaces were polished on both sides and polished using a so-called RCA process (2-stage aqueous cleaning method of Radio Corporation of America). Immediately prior to coating, the substrates were etched with 1% hydrofluoric acid, rinsed with DI water, and blown dry with nitrogen.

FIG. 3 shows a surface according to the invention of a wafer W with layer system A deposited thereon, with a first boron-containing layer 1 and a second silicon-containing layer 2. The first layer 1 may be formed as a boron nitride (BN), or a Boroxynitrid (BON) layer, or comprise corresponding mixed or gradient layers. Thus, for example, after the deposition of a boron nitride layer on the surface of the wafer, a corresponding layer having a higher oxygen content can then be deposited by adding oxygen to the process gas, whereby a certain protection against a layer degradation by atmospheric oxygen can already be achieved. The possible two or merlity of a first layer formed in this way is represented in the drawing by a dashed line. Subsequently, the second silicon-containing layer is applied in one or more process chambers of the coating system by sputtering material from a silicon, a silicon oxide or a silicon nitride target and depositing it on the first layer. This can also be carried out two or more times. The deposition can be done in a known manner with the addition of oxygen, nitrogen or / and inert gas to achieve a desired layer composition. Although it is fundamentally possible to achieve a boron doping to be achieved by the subsequent tempering even with a boron-containing layer system 1 without additional silicon-containing layer or layer system 2, the provision of the second layer is particularly advantageous if the surface of the layer or the Layer system after the coating process is exposed to the atmosphere for a longer time, for example. If a longer period of time should elapse between coating process and tempering, since very thin boron-containing, eg boron nitride have been found to be very sensitive to atmospheric influences and, for example, after a few days storage under Air are often no longer detectable. The silicon-containing layer acts in this context as a protective layer, for example, against oxidation, delamination or other atmospheric degradation of the boron nitride layer. Both layers here form the layer system A for later production of the p + region in the diffusion zone D1. Here, SiN and SiO 2 layers have shown particularly good protective properties as a capping layer. The second surface of the wafer can be precoated analogously to the following example.

FIG. 4 shows a wafer W which has a pre-coating applied to the second surface with a phosphorus-containing third layer 3, for later production of the n + region of the diffusion zone D2. In addition, a mixed layer M is provided in the boron-containing layer system A 'between the first and second layer, which has a different composition in the direction perpendicular to the surface of the wafer or the layer system, for example, the nitrogen or oxygen concentrations and / or the boron and silicon content having. Such a mixed layer M can be produced, for example, in chamber 40 or 50 if, for example, the corresponding reactive gas flows are changed or / and simultaneously co-sputtered by a boron and a silicon-containing target. Alternatively, it is also possible to sputter in one of the coating chambers 40 or 50 from a boron- as well as silicon-containing target, for example a borosilicate target. Again, the transition between the boron-containing first layer and the silicon-containing second layer can be graded or gradual. To ensure sufficient protection of the boron-containing layer from atmospheric influences, the silicon-containing layer can be deposited thicker than the very thin boron-containing layer. If the layer thickness of the boron-containing layer is set between 1 and 6 nm, the silicon-containing layer can be adjusted between 10 and 20 nm, wherein the optional mixed layer can be set, for example, between 0 and 10 nm. In principle, first and second layer system 1, 2 as well as a possibly additional mixed layer M in addition to the sputtering method can also be produced by paCVD method. For this purpose, the wafer in one of the coating chambers, for example, on an RF chuck with an RF voltage can be applied, while at the same time process gas is admitted into the chamber. Due to the partially toxic and / or explosive properties of suitable process gases such as boranes or silanes, however, special precautions must be taken here. The

Precoating of the second surface of the wafer with the third phosphorus-containing layer 3 can be carried out analogously by means of paCVD coating, for example using phosphorus-containing gases in the pretreatment chamber 20 or between pre-treatment chamber 20 and coating chamber 30 additionally provided here not further executed precoating. However, since the phosphorus-containing gases used in this regard are critical with regard to toxicity and / or combustibility, wafers precoated by spin coating can also be used here in a known manner outside the coating system 1.11. In principle, a corresponding post-coating is also possible, in which then also vacuum-suitable spin-coating layers can be used.

Fig. 5 shows a wafer coated according to Fig. 3 or Fig. 4, or was precoated after an annealing step to produce the diffusion zones D1 and D2. The first and second layers were converted by diffusion into the near-surface region of the wafer into a boron-doped first p + diffusion zone D1. Surprisingly, the boron forms a sufficient diffusion profile, independently of the additional silicon layer and possibly the mixed layer present, without leaving any further residues on the first surface of the wafer. This in contrast to known conventional spin coatings, in which often an additional processing of the surface, for example, by a polishing step is necessary.

In the same annealing step, the phosphorus-containing second n + diffusion zone D2 is also generated in the near-surface region of the second surface. In order to be able to simultaneously anneal as many wafers as possible in the annealing step of an annealing furnace or a here not shown, for example between the last coating chamber 60 and lock chamber S, S "tempering chamber of Vakuumbehand-lungs-plant I, II these are advantageously alternately with the first surface above or stacked on top of each other, so that in each case only identically coated surfaces touch, whereby an undesirable diffusion of phosphorus in the D1 region, and the boron in the D2 region can be avoided.

Although in the present description and figures the principle of the invention has been described with reference to different examples and features, the invention also includes all individual features disclosed herein in combination with examples and embodiments to which these features have not been explicitly mentioned, unless such a combination as one of the skilled person readily recognizes, from the outset seems to be inappropriate.

LIST OF REFERENCE NUMBERS A first layer, p-dopant-containing, eg boron-containing 2 second layer, substrate element-containing, for example silicon-containing 3 third layer, n-dopant-containing, for example, phosphorus-containing 5, 6 target, in particular: 5 boron-containing target 6 target containing silicon Target 7 carousel 7si, 712 ... 756, 76s through carousel 7 operated transport routes 8 handling system (alternative to carousel 7) 8zi, 8SZ, 8z1 ... 86z, 8zs by handling system 8 operated alternative transport routes 10-60 treatment chambers, Process chambers in particular: 10.20 Pre-treatment chamber 30, 40 First coating chamber 50, 60 Second coating chamber I Coating system with peripherally arranged chambers II Coating system with linearly arranged chambers

A, A 'layer system on the first surface of W S lock chamber

Claims (34)

W substrate, wafer claims 1. A method for producing a substrate having at least one, at least in a partial area boron doped surface comprising the following steps: - Providing a substrate, which is introduced in a preparatory step in a vacuum treatment plant and there, by means of a PVD or a paCVD method with a boron-containing first layer, annealing the substrate to diffuse the boron into the surface. 2. The method according to claim 1, characterized in that the provision of the substrate comprises the following steps: - introducing the substrate into a vacuum treatment plant and applying a vacuum; Placing the substrate in a coating chamber of the vacuum treatment plant and coating the substrate by means of a PVD or a paCVD process with a boron-containing first layer in a coating chamber of the vacuum treatment plant. 3. The method according to any one of the preceding claims, characterized in that the annealing is carried out in an annealing chamber of the vacuum treatment plant or in a tempering outside the vacuum treatment plant. 4. The method according to any one of the preceding claims, characterized in that is applied between coating and annealing, in a coating chamber of the vacuum treatment plant, a silicon-containing second layer by means of a PVD or a paCVD method on the first layer. 5. The method according to any one of the preceding claims, characterized in that the substrate is a wafer, in particular a silicon wafer is coated on a first surface, wherein a second, the first surface opposite surface during the application of the first and / or the second layer, is protected against a coating. 6. The method according to claim 5, characterized in that the wafer is precoated on the second surface with a phosphorus-containing third layer. 7. The method according to any one of the preceding claims, characterized in that the method for applying the first and / or the second layer is a PVD method, preferably a sputtering method, in particular a Magnetronsputterverfahren. 8. Wafer with a boron-doped surface, produced by a method according to one of claims 1 to 7. 9. wafer according to claim 8, characterized in that the wafer is a solar cell, preferably a bifacial So larzelle. 10. Sputtering method for depositing a first boron-containing layer or a boron-containing layer system on a substrate, wherein the substrate is arranged in a coating chamber of a vacuum treatment plant to a boron-containing target, characterized in that the target comprises a covalent boron compound and this by the application of a high-frequency voltage is sputtered in an at least inert gas-containing and / or nitrogen-containing atmosphere. 11. Sputtering method according to claim 10, characterized in that a BN layer is deposited. 12. Sputtering method according to claim 10 or 11, characterized in that a nitrogen-containing gas, in particular nitrogen is used to adjust a B / N ratio. 13. Sputtering method according to one of claims 10 to 12, characterized in that alone or additionally a BOxNy layer is deposited by sputtering of the boron-containing target in an oxygen-containing atmosphere. 14. Sputtering method according to claim 10, characterized in that to produce a boron-containing layer system, first a BN layer is formed by sputtering the boron-containing target in an atmosphere containing at least one inert gas and / or nitrogen, and then a BOxNy layer by sputtering the boron-containing Targets in an additional oxygen-containing atmosphere is deposited. 15. Sputtering method according to one of claims 10 to 14, characterized in that the target comprises boron nitride, in particular consists of boron nitride. 16. Sputtering method according to one of claims 10 to 15, characterized in that the layer thickness of the boron-containing layer, or of the boron-containing layer system between 1 nm and 6 nm, in particular between 2nm and 5nm is deposited. 17. Sputtering method according to claim 10, characterized in that, in addition to the first boron-containing layer or the first boron-containing layer system, a second silicon-containing layer or a second silicon-containing layer system is applied, the substrate being treated in a coating chamber of the vacuum treatment plant arranged silicon-containing target and this is sputtered in an at least inert gas-containing and / or reactive gas-containing atmosphere. 18. Sputtering method according to claim 17, characterized in that a silicon, a silicon nitride, a silicon oxide and / or a Siliziumoxinitridschicht is deposited. {preferably a SiO 2, in particular a SiN layer} 19. Sputtering method according to claim 17 or 18, characterized in that a silicon nitride, a silicon oxide, preferably a silicon target is sputtered off. 20. Sputtering method according to one of claims 17 to 19, characterized in that the second layer, or the second layer system is deposited with a layer thickness in a range of 10 to 20 nm. 21. Sputtering method according to one of claims 10 to 20, characterized in that the target with a frequency between 2 inclusive including 30 MHz, preferably between 10 inclusive including 15 MHz, in particular 13.56 MHz is operated. 22. Wafer with a coating system applied on a first surface comprising at least one boron-containing first layer, produced by a sputtering method according to one of claims 10 to 21. 23. Wafer according to claim 22, characterized in that the first layer is a BN or / and a BOxNy layer. 24. Wafer according to one of claims 22 to 23, characterized in that the first layer comprises a BN and a BOxNy layer. 25. Wafer according to one of claims 22 to 24, characterized in that the wafer comprises a silicon-containing second layer on an outer side of the first layer. 26. Wafer according to claim 25, characterized in that the second layer is a silicon layer, preferably a silicon oxide or a silicon nitride layer. 27. A wafer according to any one of claims 25 to 26, characterized in that the second layer is a multi-layer comprising a silicon layer, a silicon oxide and / or a silicon nitride layer, wherein the layer junctions with respect to their elemental composition into each other or may be formed stepwise. 28. Wafer according to one of claims 22 to 27, characterized in that the wafer is a solar cell, preferably a bifacial solar cell. 29. A vacuum treatment system having a lock chamber for introducing and / or discharging at least one wafer into the vacuum treatment installation and at least one first coating chamber, characterized in that the first coating chamber comprises a BN target. 30. Vacuum treatment plant according to claim 29, characterized in that the vacuum treatment plant downstream of the first coating chamber comprises at least a second coating chamber and this comprises a silicon target, preferably an SiO 2 target, a SiN target, but preferably a Si target. 31. Vacuum treatment installation according to one of claims 29 to 30, characterized in that the lock chamber comprises a heating device for heating and / or an etching device for treating the at least one wafer. 32. Vacuum treatment plant according to one of claims 29 to 31, characterized in that between the lock chamber and the first coating chamber at least one pre-treatment chamber is provided with a heating device for heating and / or an etching apparatus for treating the at least one wafer. 33. Vacuum treatment plant according to one of claims 29 to 32, characterized in that the vacuum treatment plant downstream of the lock chamber (S, S ') one or two pre-treatment chamber followed by one or two coating chambers each having at least one boron-containing target followed by one or two coating chambers, respectively at least one silicon-containing target, followed by the lock chamber (S) or another lock chamber (S "). 34. Vacuum treatment plant according to one of claims 29 to 33, characterized in that the chambers of the system are arranged linear, circular or polyhedral.