KR101065769B1 - Laser ablation apparatus and Method for manufacturing opening using it - Google Patents

Abstract

The present invention relates to a laser etching apparatus used for manufacturing a solar cell and a method of forming a void using the same. According to an aspect of the present invention, in the laser etching apparatus for forming a void in the back passivation layer during solar cell manufacturing, the stage portion for mounting the silicon substrate of the solar cell on which the back passivation layer is formed, and the characteristics of the silicon substrate A laser oscillation unit for oscillating the laser beam adjusted according to the laser beam; a beam forming unit for modifying the size and shape of the spot of the laser beam according to the size and shape of the void; and the laser beam according to the air gap pattern in which one or more voids are arranged. According to the laser etching apparatus including a scanning unit for scanning to be irradiated to a position, and a projection unit for condensing and irradiating the laser beam scanned by the scanning unit, in the process of manufacturing a thin thin solar cell of high efficiency, instead of a photo etching technology Etching technology creates a void pattern in the back passivation layer through a simplified process Can.

Solar cell, laser, etching, passivation

Description

Laser ablation apparatus and method for manufacturing opening using it

The present invention relates to a solar cell, and more particularly, to a laser etching apparatus used for manufacturing a solar cell and a method of forming a void using the same.

A solar cell is a semiconductor device that converts light energy generated from the sun into electrical energy by a photovoltaic effect. Depending on the type of solar cell, it can be classified into silicon solar cell and compound semiconductor solar cell. Among these, silicon solar cells are classified into crystalline silicon solar cells such as monocrystalline or polycrystalline silicon solar cells and amorphous silicon solar cells.

Among these, crystalline silicon solar cells use a single crystal or polycrystalline silicon wafer produced by cutting a single crystal or polycrystalline silicon ingot as a base. Generally, a p-type silicon wafer is used as a solar cell substrate, and an n-type emitter, an anti-reflection coating (ARC), and a front contact are formed on the front surface of the solar cell substrate. A back electrode and a back surface field (BSF) are formed on the rear surface of the solar cell substrate.

Here, the backside electric field is a kind of high-low junction, which suppresses the migration of the minority electrons to the backside by an energy barrier having a field effect. This decreases the probability that electrons, which are minority carriers, exist in the rear side, thereby decreasing the probability of recombination with holes, thereby lowering the rear side recombination speed.

Trivalent aluminum as a metal constituting the back electrode diffuses into the tetravalent silicon constituting the substrate and forms a p-type semiconductor region. During firing, the back electrode of aluminum diffuses to the back surface of the silicon substrate and forms a back electric field.

In the conventional structure in which the solar cell substrate made of silicon and the back electrode made of metal are in direct contact to form a back electric field, many defects exist at the interface between silicon and metal as the solar cell substrate and the back electrode make direct contact at the back. . This defect becomes a place where electrons and holes recombine and disappear. This back structure has a low back reflectance of less than 65% and a high back recombination rate of 750 cm / s.

1 is a cross-sectional view of a solar cell having a thick silicon substrate, and FIG. 2 is a cross-sectional view of a solar cell having a thin silicon substrate. Here, reference numeral 2 denotes a back metal electrode.

Referring to FIG. 1, when the silicon substrate 1 is sufficiently thick, incident light can be sufficiently absorbed inside the silicon substrate 1. In this case, since less light reaches the rear surface, less charge is generated from the rear surface, thereby reducing the amount of photo-generated charge. In other words, since the photogenerated charge is less likely to be collected by both electrodes, it hardly contributes to efficiency.

Silicon wafer takes about 60% of the manufacturing cost of crystalline silicon solar cell, and as shown in FIG. 2, the thickness of silicon substrate 3 is made thin (in FIGS. 1 and 2, where T1> T2). By reducing the manufacturing cost can be reduced. However, in the case where the thickness of the silicon substrate 3 is reduced to seek thinning, the path capable of absorbing incident light, that is, the light absorption path, is shortened.

As the silicon substrate 3 becomes thinner, the recombination at the surface becomes more important as compared to the recombination of electrons and holes generated inside the silicon substrate 3, and therefore, the recombination rate at the surface needs to be lowered.

In the thick silicon substrate 1, the front recombination rate, which is the portion where light is incident, greatly influences the efficiency of the solar cell. However, in the thin silicon substrate 3, not only the front recombination rate but also the rear recombination rate contributes to the solar cell efficiency. It grows bigger.

In this case, when the passivation layer is formed on the rear surface, surface defects of the silicon substrate may be reduced, thereby lowering the recombination rate. In addition, the rear structure of the rear passivation serves as a rear reflection layer, and the light absorption path that is not absorbed inside the thin silicon substrate may be reflected back from the rear reflection layer into the silicon substrate to increase the light absorption path.

In this case, if the rear structure is the rear point contact structure, the rear reflection can be relatively increased and the rear recombination speed can be lowered. 3 is a cross-sectional view of a solar cell having such a back point contact structure. When the solar cell has a back point contact structure, as the light absorption path increases, the amount of charge generated by the photovoltaic cell increases, thereby increasing the short circuit current. In addition, it is possible to improve absorption characteristics for long wavelengths penetrating to the rear surface of the silicon substrate.

The passivation layer 5 is mainly composed of dielectric materials and thus is close to an insulator. Therefore, in order to collect charges generated in the silicon substrate, in particular holes, in the back electrode, voids need to be formed in the passivation layer 5. These pores are a path through which a current can pass through the silicon substrate and the back metal electrode directly contact.

The p-type semiconductor region is formed inside the silicon substrate by diffusion of aluminum from the back electrode formed of aluminum through the pores of the passivation layer to serve as a local back field (4). The local rear electric field 4 formed on the silicon substrate is heavily doped with aluminum so that the contact resistance is low, so that current can flow well through this portion.

In manufacturing a solar cell having a back point contact structure, a photolithography technique is used to form voids. In the case of using a photolithography technique, the photolithography technique is manufactured through a complex process of several steps, and the photolithography technique is expensive, complicated in process steps, long in manufacturing time, and high in manufacturing cost. In addition, photoresist used for photolithography may contaminate unwanted parts, and in chemical wet etching, toxic chemicals are used to generate wastewater, which causes environmental problems and wastewater treatment problems.

The background art described above is technical information possessed by the inventors for the derivation of the present invention or acquired during the derivation process of the present invention, and is not necessarily a publicly known technique disclosed to the general public before the application of the present invention.

The present invention provides a laser etching apparatus and a solar cell using the same, which can form a pore pattern on a rear passivation layer through a simplified process using a laser etching technique instead of a photolithography technique in the manufacture of a highly efficient thinned solar cell. It is to provide a manufacturing method.

Another object of the present invention is to provide a laser etching apparatus capable of forming a pore pattern having various sizes, intervals, and array shapes in a large area in a very short time using a galvano mirror, and a method of manufacturing a solar cell using the same.

In addition, the present invention is a laser etching apparatus capable of manufacturing a thin-film solar cell of high efficiency and eco-friendly yet does not require any consumables such as masks or pot resists, low maintenance costs, no waste water and no chemicals It is to provide a solar cell manufacturing method.

According to an aspect of the present invention, in the laser etching apparatus for forming a void in the back passivation layer during solar cell manufacturing, the stage portion for mounting the silicon substrate of the solar cell on which the back passivation layer is formed, and the characteristics of the silicon substrate A laser oscillation unit for oscillating the laser beam adjusted according to the laser beam; a beam forming unit for modifying the size and shape of the spot of the laser beam according to the size and shape of the air gap; and a laser beam according to the air gap pattern in which one or more air gaps are arranged. There is provided a laser etching apparatus including a scanning unit for scanning to be irradiated to a position, and a projection unit for condensing and irradiating a laser beam scanned by the scanning unit.

The scanning unit receives a first galvano mirror that receives and reflects a laser beam from the beam forming unit and rotates about a first axis, and receives and reflects a laser beam that is reflected from the first galvano mirror and is different from the first axis. It may include a second galvano mirror that rotates about two axes. Here, the scan unit may adjust at least one of an angle formed by the first axis and the second axis, a degree of rotation of the first galvano mirror, and a degree of rotation of the second galvano mirror in response to the gap pattern.

Alternatively, the scan unit may include a galvano mirror and a polygon mirror, and may adjust at least one of an angle formed by a rotation axis of the galvano mirror and a rotation axis of the polygon mirror, a degree of rotation of the galvano mirror, and a degree of rotation of the polygon mirror.

Alternatively, the scan unit may include any one of a galvano mirror or a polygon mirror that performs a one-way scan, and the stage unit may be moved in a direction different from the scan direction of the scan unit.

According to another aspect of the present invention, in the method of forming a void by using a laser etching device in manufacturing a solar cell, preparing a silicon substrate having a passivation layer formed on the back, determining the characteristics of the silicon substrate, According to the determined characteristics, there is provided a method of forming voids in a solar cell, the method including adjusting laser processing conditions of a laser etching apparatus, and forming a pore pattern in a passivation layer using the laser etching apparatus.

Here, the processing power of the laser oscillated at the laser oscillation unit and adjusted according to the laser processing conditions is 0.3 watt, the wavelength of the laser beam is 126 nm, the pulse width is 10 ns at 20 khz, and the repetition rate. (rep rate) may be 100khz.

Alternatively, the processing power of the laser may be 0.5 watts, the wavelength of the laser beam may be 266 nm, the pulse width may be from 20khz to 100ps, and the repetition rate may be 100khz.

Alternatively, the laser may have a processing power of 0.8 watts, a laser beam wavelength of 355 nm, a pulse width of 20 khz to 15 ns, and a repetition rate of 100 khz.

Alternatively, the processing power of the laser may be 0.9 watts, the wavelength of the laser beam may be 400 nm, the pulse width may be 20khz to 100fs, and the repetition rate may be 100khz.

Alternatively, the processing power of the laser may be 1 watt, the wavelength of the laser beam may be 532 nm, the pulse width may be 20khz to 15ns, and the repetition rate may be 100khz.

Alternatively, the processing power of the laser may be 3 watts, the wavelength of the laser beam may be 1064 nm, the pulse width may be 20khz to 30ns, and the repetition rate may be 300khz.

Alternatively, the processing power of the laser may be 10 watts, the wavelength of the laser beam is 2940 nm, the pulse width may be 20khz to 100ns, and the repetition rate may be 100khz.

Other aspects, features, and advantages other than those described above will become apparent from the following drawings, claims, and detailed description of the invention.

According to a preferred embodiment of the present invention, a pore pattern may be formed on the rear passivation layer through a simplified process by using laser etching instead of photolithography in the process of manufacturing a highly efficient thinned solar cell.

In addition, by using a galvano mirror, it is possible to form a void pattern having various sizes, intervals and arrangement shapes in a large area in a very short time.

In addition, maintenance costs are low because no consumables such as masks or pot resists are required, and wastewater does not occur and chemicals are not used, thereby making it possible to manufacture an eco-friendly and highly efficient thinned solar cell.

As the invention allows for various changes and numerous embodiments, particular embodiments will be illustrated in the drawings and described in detail in the written description. However, this is not intended to limit the present invention to specific embodiments, it should be understood to include all transformations, equivalents, and substitutes included in the spirit and scope of the present invention. In the following description of the present invention, if it is determined that the detailed description of the related known technology may obscure the gist of the present invention, the detailed description thereof will be omitted.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another.

The terminology used herein is for the purpose of describing particular example embodiments only and is not intended to be limiting of the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In this application, the terms "comprise" or "have" are intended to indicate that there is a feature, number, step, operation, component, part, or combination thereof described in the specification, and one or more other features. It is to be understood that the present invention does not exclude the possibility of the presence or the addition of numbers, steps, operations, components, components, or a combination thereof.

In the present invention, the pore pattern refers to a pattern in which at least one pore, which is an electrical connection path between the inside of the silicon substrate and the back electrode, is arranged on the back passivation layer of the silicon substrate of the solar cell. The size of the pore pattern may be represented by the ratio of the sum of the area of all the pores to the back surface area of the silicon substrate, and each pore may be arranged at regular intervals or irregularly with regularity.

Hereinafter, a method of forming a pore pattern in a solar cell according to a conventional photolithography technique will be described in detail with reference to the accompanying drawings of an embodiment of the present invention.

4 is a flowchart illustrating a method of forming a pore pattern in a rear passivation layer of a solar cell according to a conventional photolithography technique.

First, the passivation layer 51 is formed on the back surface of the silicon substrate 50 of the solar cell (see (a)).

Then, the photoresist 52 is coated on the passivation layer 51, and a soft baking process is performed (see (b)). The photoresist 52 is a photo sensitive material and will be apparent to those of ordinary skill in the art.

In order to form a pore pattern in the passivation layer 51, a portion of the photoresist 52 corresponding to the pore pattern must be removed. To do this, the following process is performed.

An exposure process is performed for a predetermined time using the photomask 53 on which the photoresist pattern corresponding to the void pattern is formed (see (c)). Thereafter, the exposed portion is subjected to a development process, a cleaning process, and a post baking process (see (d)).

The passivation layer 52 is formed by performing an etching process using an etching solution on the passivation layer 52 that is exposed after the predetermined portion 54 of the photoresist 53 is removed through the above-described process. A local opening 55 is formed in the portion corresponding to the middle void pattern (see (e)).

Thereafter, the remaining photoresist 52 is removed through a strip process to form the void pattern in the passivation layer 51 (see (f)).

Photomask or photoresist is used as a consumable during the above-described process, and the maintenance cost is high, and wastewater is generated by using chemicals such as etching solution, which causes environmental pollution and wastewater treatment problems. In addition, the photoresist applied on the passivation layer may contaminate the undesired portions, and as the above-described process requires many processes, the manufacturing time is long and the manufacturing cost is high.

Therefore, the above-described problem can be solved by forming a pore pattern on the back passivation layer of the solar cell using the laser etching apparatus according to the embodiment of the present invention.

FIG. 5 is a flowchart illustrating a method of forming a pore pattern in a rear passivation layer of a solar cell according to a laser etching technique using a laser etching apparatus according to an embodiment of the present invention.

Referring to FIG. 5A, a passivation layer 51 made of a dielectric material is formed on the back surface of the silicon substrate 50 of the solar cell.

Referring to FIG. 5B, a portion of the passivation layer 51 is removed by irradiating a laser beam to a position where a void pattern is to be formed using a laser etching device.

Here, the void pattern may be formed in the passivation layer 51 by adjusting the laser beam to have processing conditions according to the characteristics of the silicon substrate 50. Characteristics of the silicon substrate 50 affecting the laser processing conditions may be a laminated structure of the passivation layer 51, characteristics such as thickness, a surface structure of the back surface of the silicon substrate 50, and the like.

Thereafter, the back electrode is formed, and the metal constituting the electrode is diffused into the silicon substrate 50 of the solar cell through a firing process, thereby manufacturing a highly efficient and thinned solar cell.

6 is a block diagram of a laser etching apparatus according to an embodiment of the present invention, FIG. 7 is an embodiment of the scan unit, and FIG. 8 is another embodiment of the scan unit.

Referring to FIG. 6, the laser etching apparatus 100 includes a laser oscillator 110, a beam expanding unit 120, a beam forming unit 130, a scanning unit 140, a projection unit 150, and a stage unit 160. It may include.

The laser oscillator 110 includes a laser medium, a pumping unit, a switching unit, and the like to output a laser beam having a predetermined pulse width. The laser beam oscillated by the laser oscillator 110 may be in a pulse wave mode.

The wavelength of the laser beam oscillated by the laser oscillator 110 according to the present embodiment may be 126 nm to 2940 nm, has a processing power of 0.3 watts to 10 watts, and has a pulse width of 100 fs to 100 ns at 20 kHz. , Repetition rate may be 100khz to 300khz.

For example, laser processing conditions are shown in Table 1 below. Here, the pulse width and the like unit is ^{ns (nanosecond, 10 -9 s)} , ps (picosecond, 10 -12 s), fs (femtosecond, 10 -15 s).

However, the numerical values relating to the laser wavelength, the processing power, the pulse width, and the repetition rate shown in Table 1 do not mean numerical values in a strict sense, but also mean numerical values in the meanings commonly used by those skilled in the art for laser processing. to be.

Here, as the wavelength of the laser beam is shorter, fine and precise processing is possible in forming the pore pattern of the solar cell, and thus the processing performance is improved, and the longer the wavelength of the laser beam, the lower the price of the system is.

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Alternatively, in the use of a laser beam, lasers such as laser beam processing power, pulse width, repetition rate, as well as the wavelength of the laser beam, depending on the thickness of the back passivation layer, the laminated structure, and the back surface structure of the solar cell substrate to be processed. Processing conditions may change.

The beam expanding unit 120 enlarges the size of the laser beam so that a more precise laser beam spot can be formed in the beam forming unit 130 at the rear end.

The beam forming unit 130 may convert the energy distribution into a flat top form with respect to the laser beam enlarged by the beam expanding unit 120 so that energy may be evenly transmitted to the processing region.

In this embodiment, each pore may have various shapes such as a circle, an ellipse, and a polygon, and the beam forming unit 130 may change the size and shape of the laser beam according to the size and shape of each pore.

The scan unit 140 corresponds to a focus adjusting unit, and finely horizontally moves the focus of the laser beam on the rear passivation layer of the solar cell.

Referring to FIG. 7, a scan unit 140 according to an embodiment is shown.

The scan unit 140 includes a central portion 210, a rotating member 220, which is a rod-shaped structure having one end fixedly connected to the central portion 210, and a head portion 230 fixedly connected to the other end of the rotating member 220. It is a structure that includes, the first mirror 212 is provided in the central portion 210, the second mirror 232 is provided in the head 230. The laser beam transmitted from the front end component is reflected at the first mirror 212 and reflected back at the second mirror 232 along a path parallel to the rotating member 220 to focus the focusing element 240 (eg, And a solar cell substrate 200 mounted on the stage unit 160 by a projection unit or the like.

Here, the rotating member 220 is rotated in the clockwise or counterclockwise direction along the arrow around the central portion 210, the head portion 230 of the circumference having a radius corresponding to the length of the rotating member 220 The laser beam may be irradiated at some position in the path. The laser beam may be irradiated as shown in FIG. 9 by repeating the rotation of the head unit 230 while moving the stage unit 160 in a direction perpendicular to the path of the head unit 230.

Referring to FIG. 8, a scan unit 140 according to another embodiment is shown.

The scan unit 140 may be provided with two galvano mirrors 250 and 260 facing each other. The first galvano mirror 250 receives and reflects the laser beam and rotates about the first axis according to the driving of the motor 252. The second galvano mirror 252 receives and reflects a laser beam reflected from the first galvano mirror while rotating about a second axis different from the first axis according to the driving of the motor 262. Therefore, the laser beam is a desired point on the stage unit 160 by adjusting the angle between the first axis and the second axis, the degree of rotation of the first galvano mirror 250, and the degree of rotation of the second galvano mirror 260. It is possible to be investigated. In this embodiment, each axis of the two galvano mirrors is moved by the scan unit 140 and the respective galvano mirrors are rotated by the scan unit 140 according to the positions of the pores to be formed in the rear passivation layer of the solar cell according to a predetermined pattern.

That is, the laser beam is positioned at a position to form a void in the entire solar cell substrate without moving the stage unit 160 using two galvano mirrors or moving the solar cell substrate mounted on the stage unit 160. It is possible to investigate the area scan is possible, there is an advantage that has a high degree of freedom in the pore forming position.

In another embodiment, the scan unit 140 may be configured by a combination of a galvano mirror and a polygon mirror. In the above-described embodiment, one of the two galvano mirrors may be replaced with a polygon mirror.

Here, the laser beam is irradiated to the desired point on the stage unit 160 by adjusting one or more of the angle formed between the rotation axis of the galvano mirror and the rotation axis of the polygon mirror, the degree of rotation of the galvano mirror, and the degree of rotation of the polygon mirror. It is possible. In the present embodiment, the scanning unit 140 moves the respective rotation axes of the galvano mirror and the polygon mirror and rotates the galvano mirror and the polygon mirror in accordance with the positions of the pores to be formed in the rear passivation layer of the solar cell according to a predetermined pattern. Let's do it.

The combination of the galvano mirror and the polygon mirror is also possible to irradiate the laser beam to the position to form the voids on the entire solar cell substrate to scan the area, there is an advantage that has a high degree of freedom in the pore formation position.

In another embodiment, the scan unit 140 includes one of a galvano mirror and a polygon mirror to perform one-way scan. In this case, the stage 160 moves in a direction different from the scanning direction of the galvano mirror or the polygon mirror (for example, in a vertical direction) to irradiate a laser beam to a position where a void is to be formed in the entire solar cell substrate. Can be.

After positioning the laser beam to be irradiated to a specific position by the scanning unit 140, the projection unit 150 focuses the laser beam finely adjusted to irradiate a predetermined position of the rear passivation layer of the solar cell. The projection unit 150 may be configured of an fexeta lens, a telecentric lens, or the like. The fexeta lens or the telecentric lens may allow the laser beam to be irradiated substantially vertically at a predetermined position. The projection 150 must be focused so that the laser beam can be accurately irradiated to a predetermined position of the rear passivation layer where the target void pattern is to be formed. Here, the projection unit 150 may be composed of a single lens, a lens group of a combination of several convex and concave lenses may be composed of, or may be composed of a combination of one or more lenses and other optical systems. .

The etching is performed at the portion irradiated with the laser, so that the distance between the projection unit 150 and the stage unit 160 may be adjusted so that a focal point may be formed on the rear passivation layer. In addition, when the depth to be etched is deeper than the focal depth of the laser, it is necessary to operate to adjust the position of the lens by the etched depth as the etching proceeds.

The stage 160 is mounted with a solar cell substrate having a back passivation layer to be etched by the laser etching apparatus 100 according to the present embodiment. The stage 160 moves two-dimensionally on a plane along the X-axis or Y-axis, or moves up and down along the Z-axis to the solar cell substrate on which the focus of the laser beam passing through the projection 150 is placed on the stage 160. You can make it fit.

In the present embodiment, the laser oscillator 110, the beam expanding unit 120, the beam forming unit 130, the scanning unit 140, and the projection unit 150 are optically connected. Optical phenomena include various phenomena such as reflection, diffraction, and refraction of light. Here, 'optically connected' means that light emitted from one component is received by the other component by various optical phenomena. it means. Each component may be directly optically connected or may be optically connected by an optical system including a mirror, a lens, or the like that transmits or reflects a laser beam.

9 is a flowchart illustrating a pore forming method in manufacturing a solar cell using a laser etching apparatus according to an embodiment of the present invention.

The silicon substrate on which the back passivation layer is formed is mounted on the stage unit 160 (step S300). Since the silicon substrate is preferably mounted so that the laser beam can be irradiated to the rear surface of the silicon substrate, the back surface of the silicon substrate may be inverted and mounted on the upper surface of the stage unit 160.

A silicon substrate serving as the base of the solar cell is prepared (step S302), and a passivation layer is formed on the rear surface of the silicon substrate (step S304). In this process, a general texturing process, a diffusion process, an anti-reflection film manufacturing process, and the like may be further included in manufacturing a solar cell.

The substrate characteristics of the silicon substrate of the solar cell to be processed are determined using a laser etching apparatus (step S310). The substrate characteristic to be determined is passivation layer information such as thickness of the back passivation layer of the silicon substrate to which the laser beam is to be irradiated, laminated structure, or the back surface structure of the silicon substrate.

In this way, the substrate characteristics are analyzed to set the laser processing conditions or to adjust the laser processing conditions which are already set when forming the void pattern in a subsequent process.

According to another embodiment, the substrate characteristics of the solar cell may be determined or analyzed before step S300 in which the solar cell is provided to the stage unit 160 of the laser etching apparatus.

The silicon substrate of the solar cell mounted on the stage unit 160 is irradiated with a laser beam to form a void pattern (step S320).

The laser beam is oscillated (step S322), the substrate characteristics are determined in advance, and the laser beam is adjusted according to the set laser processing conditions (step S324). The laser beam is focused and irradiated to a position to be removed in the rear passivation layer by scanning in accordance with a predetermined gap pattern (step S326) (step S328). In the above process, the scan may be performed by the scan unit 140 including the galvano mirror, and the condensing and irradiation of the laser beam may be performed by the projection unit 150.

By repeating steps S326 to S328, a desired pore pattern is formed on the entire silicon substrate of the solar cell mounted on the stage unit 160.

After one or more pores are formed and the pore pattern is completed for the entire silicon substrate of the solar cell, a subsequent process for manufacturing the solar cell is performed (step S330).

In general, a metal electrode for collecting the photogenerated charge is formed on the front and rear of the solar cell (step S332). By twisting a very thin line like a net, the mesh is made into a structure that allows particles to fall out, and by screening with a screen having a certain pattern by blocking the part of the mesh with an emulsion (emulsion coating) where the particles do not want to fall out. Formation of the metal electrode is possible. The paste drawn on the screen mask in which the opening is formed may be rubbed with a squeeze to form a metal pattern on the surface of the substrate.

The metal paste used to form the electrode of the solar cell may be silver (Ag) as a metal for front contact, aluminum (Al) as a metal for forming a rear electric field, AgAl with 3% aluminum as a bus bar metal for rear soldering, and the like. .

Then, the metal electrode is dried and heat treatment is performed through a sintering process (step S334) to make the chemical contact with silicon while reducing the specific resistance of the metal itself, thereby completing the formation of the metal electrode.

In the present invention, a highly efficient thinned solar cell has been described assuming a solar cell having a rear point contact structure, but in addition, the rear point contact heterojunction structure, a simple back electrode structure (simplified back-point) Solar cells such as contact) can be formed using the above-described laser processing apparatus.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention as defined in the appended claims. It will be understood that the invention may be varied and varied without departing from the scope of the invention.

1 is a cross-sectional view of a solar cell with a thick silicon substrate.

2 is a cross-sectional view of a solar cell having a thin silicon substrate.

3 is a cross-sectional view of a solar cell having a back point contact structure.

Figure 4 is a flow chart of a method for forming a pore pattern on the back passivation layer of the solar cell according to the conventional photolithography technique.

FIG. 5 is a flowchart illustrating a method of forming a void pattern in a rear passivation layer of a solar cell according to a laser etching technique using a laser etching apparatus according to an embodiment of the present invention. FIG.

Figure 6 is a block diagram of a laser etching apparatus according to an embodiment of the present invention.

7 is a diagram illustrating an embodiment of a scan unit;

8 is a view showing another embodiment of a scanning unit.

9 is a flow chart of a pore forming method for manufacturing a solar cell using a laser etching apparatus according to an embodiment of the present invention.

<Explanation of symbols for the main parts of the drawings>

1, 3, 10: silicon substrate 2: back electrode

4: point contact electrode 5, 11: passivation layer

15: void 100: laser etching device

110: laser oscillation unit 120: beam expanding unit

130: beam forming unit 140: scanning unit

150: projection unit 160: stage unit

Claims (20)

In the laser etching apparatus for forming a void in the back passivation layer during solar cell manufacturing, A stage unit for mounting the silicon substrate of the solar cell on which the rear passivation layer is formed; A laser oscillator for oscillating a laser beam; A first galvano mirror that receives and reflects the laser beam and rotates about a first axis; and a second axis that receives and reflects the laser beam reflected from the first galvano mirror and is different from the first axis A scan unit including a second galvano mirror which rotates to scan the laser beam to a position determined according to a pore pattern for arranging one or more of the pores; It includes a projection for condensing and irradiating the laser beam scanned by the scanning unit, The scan unit independently drives the first galvano mirror and the second galvano mirror in correspondence with the air gap pattern to form an angle between the first axis and the second axis, and a degree of rotation of the first galvano mirror. And adjusting at least one of the degree of rotation of the second galvano mirror. delete delete In the laser etching apparatus for forming a void in the back passivation layer during solar cell manufacturing, A stage unit for mounting the silicon substrate of the solar cell on which the rear passivation layer is formed; A laser oscillator for oscillating a laser beam; A galvano mirror that receives and reflects the laser beam and rotates about a first axis of rotation, and receives and reflects the laser beam reflected from the galvano mirror and rotates about a second axis of rotation that is different from the first axis of rotation A scan unit for scanning the laser beam to a position determined according to a pore pattern for arranging one or more of the pores; It includes a projection for condensing and irradiating the laser beam scanned by the scanning unit, The scan unit independently drives the galvano mirror and the polygon mirror in correspondence with the air gap pattern, such that the angle formed by the first rotation axis and the second rotation axis, the degree of rotation of the galvano mirror, and the degree of rotation of the polygon mirror Laser etching apparatus, characterized in that for controlling at least one or more of. delete The method according to any one of claims 1 to 4, The processing power of the laser oscillated by the laser oscillation unit is 0.3 watt, the wavelength of the laser beam is 126 nm, the pulse width is 20khz to 10ns, and the repetition rate is 100khz. Laser etching apparatus, characterized in that. The method according to any one of claims 1 to 4, The processing power of the laser oscillating from the laser oscillation unit is 0.5 watts, the wavelength of the laser beam is 266nm, the pulse width is 20khz to 100ps, the laser etching apparatus, characterized in that the repetition rate is 100khz. The method according to any one of claims 1 to 4, The processing power of the laser oscillated from the laser oscillation unit is 0.8 watts, the wavelength of the laser beam is 355nm, the pulse width is 20khz to 15ns, the laser etching apparatus, characterized in that the repetition rate is 100khz. The method according to any one of claims 1 to 4, The processing power of the laser oscillated from the laser oscillation unit is 0.9 watts, the wavelength of the laser beam is 400nm, the pulse width is 20khz to 100fs, the laser etching apparatus, characterized in that the repetition rate is 100khz. The method according to any one of claims 1 to 4, The processing power of the laser oscillated by the laser oscillation unit is 1 watt, the wavelength of the laser beam is 532nm, the pulse width is 20khz to 15ns, the laser etching apparatus, characterized in that the repetition rate is 100khz. The method according to any one of claims 1 to 4, The processing power of the laser oscillated by the laser oscillation unit is 3 watts, the wavelength of the laser beam is 1064nm, the pulse width is 20khz to 30ns, the laser etching apparatus, characterized in that the repetition rate is 300khz. The method according to any one of claims 1 to 4, The processing power of the laser oscillating from the laser oscillation unit is 10 watts, the wavelength of the laser beam is 2940nm, the pulse width is 20khz to 100ns, the laser etching apparatus, characterized in that the repetition rate is 100khz. delete delete delete delete delete delete delete delete

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