A method and device for stripping metal electrodes of solar cells

Abstract

The invention discloses a metal electrode stripping method and device for a solar cell. In the photolithography process, only one layer of photoresist is coated without secondary exposure. The expected inverted trapezoidal graphic interface can be achieved by adjusting the thickness, exposure intensity and development time of the photoresist layer. Then, a metal electrode with a thickness less than that of the photoresist layer is evaporated, so that the desired metal electrode and the photoresist layer, as well as the desired metal electrode and the metal to be stripped are not adhered to each other. Then, a metal electrode stripping device with a roller is used to rotate the wafer, so that the photoresist layer and the photoresist stripping liquid fully react, and the metal on the photoresist is driven to be evenly and completely separated. No additional manual operation is required for stripping, thereby reducing production costs and improving production efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of solar cells, and in particular relates to a method and a device for stripping a metal electrode of a solar cell. Background Art

[0002] With the rapid development of my country's aerospace industry, gallium arsenide solar cells are widely used in the aerospace field due to their high photoelectric conversion efficiency and good reliability. Among them, the metal electrode stripping process is a crucial link in the field of solar cell chip manufacturing. The current metal electrode stripping process includes the following steps:

[0003] First, a photolithography process is used to spin-coat photoresist on a wafer to produce a photoresist pattern. The photoresist usually used is a reverse photoresist or a multilayer photoresist. Secondly, a metal electrode is plated on the surface of the wafer with the pattern produced by electron beam evaporation. Thirdly, the wafer is immersed in acetone or a photoresist stripping solution to remove the photoresist, and most of the metal electrodes on the photoresist fall off the wafer surface. Then, the stripping solution is used to rinse the wafer surface under high pressure to wash away the residual metal on the wafer surface, leaving only the metal with the original pattern as the electrode. Finally, the wafer is soaked in acetone and isopropyl alcohol to clean the stripping solution residue on the wafer surface. After rinsing with water and high-speed spin drying, a wafer with the expected metal electrode pattern is obtained.

[0004] This traditional stripping process is not friendly to the manufacture of solar cell chips. The metal to be stripped often cannot be completely stripped due to the adhesion of metal electrodes, resulting in metal wires hanging on the side walls of the wafer, causing wafer short circuits, or tearing the required electrodes and damaging the electrode surface, reducing product yield.

[0005] For example, a Chinese patent with patent application number CN202110868316.2 discloses a method for making a metal electrode peeling film. The semi-finished chip is first cleaned by soaking it in an alkaline solution, and then the chip surface is cleaned with acetone, ethanol and deionized water. Then, a reverse glue is applied to the chip, and an electrode peeling cornea is formed by pre-baking, exposure, reverse baking, flood exposure and development. This method uses an alkaline solution to passivate the surface so that the passivated surface exhibits a certain hydrophilicity, which is conducive to making the inclination angle of the film and expanding the width of the bottom of the inverted platform, solving the problems of unstable inclination angle of the inverted platform and thinning thickness of the film, making the size of the peeling electrode stable and controllable, and there is no metal wire adhesion on the edge of the electrode. However, this method requires a secondary exposure of the film, which increases the cost and the risk of generating fragments, and reduces the yield of the product.

[0006] Another example is a Chinese patent with patent application number CN202310778200.9, which discloses a metal stripper wafer immersion device. The immersion device is driven by a mechanical coupling, and can be raised and lowered and tilted during the immersion process to give full play to the immersion effect. At the same time, the wafer is placed horizontally and can be taken and placed individually. The shaking of the wafer can be controlled during the immersion process to increase the degumming ability. The tilt of the synchronous mechanism can prevent the photoresist and metal from accumulating on the wafer during stripping. However, this device has a complex structure and high cost. Moreover, since the wafer is placed horizontally, it is not suitable for the classic method of using a basket to vertically hold multiple wafers for metal stripping at the same time, which reduces production efficiency and is not conducive to large-scale batch manufacturing.

[0007] In summary, the existing metal electrode stripping process has the following disadvantages:

[0008] (1) The photolithography process requires reverse glue, double-layer glue or triple-layer glue, which is complex and has low yield.

[0009] When reverse glue is used in lithography, the chip coated with reverse glue needs to undergo pre-bake, exposure, reverse bake, flood exposure, development and other processes. There are two exposure processes, which increases time costs and reduces production efficiency. It is also easy to bring uncontrollable risks such as breakage and sticking boards, which reduces the product yield.

[0010] Similarly, when using a double-layer or triple-layer resist process for photolithography, each additional layer of resist requires a whole set of processes such as coating, pre-baking, exposure, development, and post-baking, and the costs of materials, time, and manpower also increase accordingly. At the same time, the developers for different resist layers are also different, and the second developer is very likely to react with the first layer of resist, thereby destroying the structure of the first layer of resist as the base, causing irregular changes in the overall structure of the multiple layers of resist, and failing to form the expected inverted trapezoidal or inverted "convex" interface, resulting in adhesion of the subsequent evaporated metal layer, and thus failing to effectively peel off the metal on the resist layer.

[0011] (2) When removing the photoresist and stripping the metal, the electrode is easily damaged and the pattern is destroyed

[0012] The wafer is placed in the photoresist stripping solution and soaked. Although the photoresist will react and decompose with the photoresist stripping solution, causing the metal on the glue to fall off, the thickness of the glue layer is uneven, and the degree of metal shedding in different areas of the wafer is inconsistent when soaking, resulting in the metal on the glue layer The whole cannot fall off synchronously. Therefore, it is usually necessary to introduce a specially customized soaking device, or the operator manually assists in stripping the metal. The special soaking device is expensive, the production cost is high, and it is impossible to strip multiple wafers at the same time, which reduces production efficiency; manual operation requires frequent placement of wafers from the flower basket, and manual washing of the wafer surface to remove the metal electrode on the photoresist, which adds more uncontrollable factors. Not only is the metal electrode adhesion site prone to tearing, resulting in damage to the metal electrode surface, or the stretched metal wire adheres to the side wall of the wafer to cause a short circuit in the wafer, but also due to the different forces when clamping and washing the wafer, it is very easy to produce fragments. Summary of the invention

[0013] The purpose of the present invention is to provide a method and device for stripping metal electrodes of solar cells, thereby improving the stripping efficiency and success rate of metal electrodes, reducing production costs, and greatly improving the manufacturing efficiency and yield of solar cells.

[0014] To achieve the above object, the present invention provides the following technical solutions:

[0015] A method for stripping a metal electrode of a solar cell, comprising:

[0016] Providing a substrate wafer, and growing an epitaxial layer on the substrate wafer to form a semi-finished chip;

[0017] A layer of negative photoresist is spin-coated on the epitaxial layer surface of the semi-finished chip to form a photoresist layer, and then baked, exposed, developed, and hardened and baked to form a graphic interface required for the metal electrode pattern on the photoresist layer;

[0018] Vapor-depositing a metal electrode on the surface of the epitaxial layer with a graphic interface, wherein the thickness of the metal electrode is less than the thickness of the photoresist layer;

[0019] A metal electrode stripping device is prepared, the metal electrode stripping device comprises a cylinder, a roller platform, and a roller, the cylinder contains a photoresist stripping liquid, the roller platform is placed in the cylinder, the roller is rotatably arranged on the roller platform, and the roller platform is provided with a basket slot on the periphery of the roller;

[0020] Take a plurality of wafers with metal electrodes deposited thereon and place them in a basket with their flat edges facing upwards, insert the basket into the basket slot, make the side walls of the wafer contact the roller, and immerse the basket in the photoresist stripping solution to remove the metal electrodes near the flat edges of the wafers. Then rotate the rollers, which drive the wafers to rotate slowly until the flat edges of the wafers face downwards, and remove the metal electrodes far from the flat edges of the wafers.

[0021] The wafer from which the metal electrode has been stripped is cleaned and subjected to subsequent processes to complete the production of the solar cell chip.

[0022] Optionally, the flower basket is immersed in the photoresist stripping solution for 15 minutes, and after the roller is rotated to make the flat edge of the wafer face downward, it is immersed for another 15 minutes to complete the stripping of the metal electrode.

[0023] Optionally, the substrate wafer is a Ge substrate, and growing an epitaxial layer on the substrate wafer to form a semi-finished chip includes:

[0024] A Ge bottom cell, an InGaAs middle cell and a GaInP top cell are grown sequentially on a Ge substrate using MOCVD equipment.

[0025] Optionally, after the epitaxial layer is grown, the semi-finished chip is soaked in acetone for 10 minutes and in isopropanol for 10 minutes, then rinsed with water and spun dry at high speed.

[0026] Optionally, the thickness of the photoresist layer is 3 μm, and the steps of baking, exposure, development, and hardening the film include:

[0027] The semi-finished chip with negative photoresist was placed in an oven and baked at 100°C for 30 minutes. Then, it was exposed through a mask in an exposure machine. The exposure intensity was 100 mJ / cm 2 ; Then, soak in the developer for 1 minute to remove the photoresist in the mask shielding area; finally, put it into the oven and bake it at 100°C for 30 minutes to harden the film and form an inverted trapezoidal graphic interface on the photoresist layer.

[0028] Optionally, evaporating a metal electrode on the surface of the epitaxial layer having a graphic interface includes:

[0029] The semi-finished chip with a graphic interface is placed in a metal coating machine, and Au, AuGe, Ni, and Au are evaporated on the surface of the epitaxial layer with the graphic interface by electron beam evaporation, with thicknesses of 150nm, 90nm, 120nm, and 600nm respectively, to complete the preparation of the metal electrode.

[0030] Optionally, the wafer from which the metal electrode has been stripped is cleaned and subsequent processes include:

[0031] The flower basket is taken out of the photoresist stripping solution, and is placed in a water bath to rinse with water to wash away the metal wire that has fallen off the flower basket; the flower basket is then immersed in acetone and isopropanol in turn for 10 minutes each, and then rinsed and spun dry;

[0032] Etching and electrode vapor deposition are performed on the back of the wafer, followed by selective etching and vapor deposition of anti-reflection film on the front of the wafer, followed by annealing, and then gluing protection, cutting, and end corrosion are performed on the front of the wafer. Finally, IV testing is performed to complete the production of solar cell chips.

[0033] The present invention also provides a metal electrode stripping device for a solar cell, comprising a cylinder body, a roller platform, a roller, and a rotating bracket, wherein the cylinder body contains a photoresist stripping liquid, the roller platform is arranged in the cylinder body, the roller is rotatably arranged on the roller platform, the roller platform is provided with a flower basket slot for inserting a flower basket supporting foot on the outer periphery of the roller, and the side wall of the wafer inside the flower basket abuts against the roller; the rotating bracket is arranged on the side wall of the cylinder body, the rotating shaft at the center of the roller is connected to the rotating bracket, and the rotating bracket is provided with a handle for driving the roller to rotate.

[0034] Optionally, the roller platform is further provided with two flower basket baffles, two roller baffles and two limit baffles, the two flower basket baffles are respectively arranged on the front and rear sides of the roller, the roller baffle is arranged between the flower basket baffle and the roller, a flower basket slot is formed between the flower basket baffle and the limit baffle, and the two limit baffles are respectively arranged on the left and right sides of the roller.

[0035] Optionally, a first liquid drain groove is opened in the middle of the flower basket baffle, and a second liquid drain groove is formed by leaving a gap between the two ends of the flower basket baffle and the two limit baffles.

[0036] After adopting the above scheme, the beneficial effects of the present invention are:

[0037] 1. The present invention adopts a single-layer photoresist process, and can realize the graphic interface required by the metal electrode pattern through coating, exposure and development. The height difference formed by the thickness of the photoresist layer and the thickness of the metal electrode realizes the separation between the metal electrode and the photoresist, and the required metal electrode and the metal to be stripped. There is no need to perform secondary exposure of the reverse coating process or repeated photolithography of multiple layers of coating. The process is simple and easy to implement, which reduces production costs and improves production efficiency, while avoiding the risk of reduced yield caused by complex processes.

[0038] 2. Use a cylinder with a roller device to soak and strip the metal electrode on the photoresist. The rotation of the roller can drive the wafer to rotate slowly. On the one hand, the photoresist fully reacts with the photoresist stripping liquid, driving the metal on the photoresist to fall off the wafer. On the other hand, when the roller is not rotated, the metal on the upper part of the wafer will fall off first and rest on the surface of the adjacent wafer. Rotating the roller can make the metal originally at the bottom of the wafer rotate to the upper part of the wafer and slowly and automatically fall off the wafer. Therefore, the rotation of the wafer driven by the rotation of the roller can make the photoresist on different areas of the wafer surface fully contact the photoresist stripping liquid. With the help of the tension of the photoresist stripping liquid and the gravity traction of the falling metal wire, the metal on the photoresist can be completely detached and peeled off autonomously. There is no need for complex and expensive special spray devices to assist in the stripping of metal electrodes, nor is there a need for manual operation to strip the electrodes, which reduces production costs and improves production efficiency.

[0039] 3. A method of using a cylinder with rollers to soak wafers to achieve metal electrode stripping. Multiple wafers can also be placed in the same basket for operation, which further improves production efficiency. It is easy to operate, has wide practicability, low cost, high efficiency, and can also be applied to other semiconductor device metal stripping processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 It is a structural schematic diagram of manufacturing a photoresist layer on the surface of an epitaxial layer according to the present invention;

[0041] Figure 2 It is a front view of the metal electrode stripping device of the present invention;

[0042] Figure 3 A top view of the metal electrode stripping device of the present invention;

[0043] Figure 4 A three-dimensional diagram of a metal electrode stripping device according to the present invention;

[0044] Figure 5 It is a schematic diagram of the flower basket of the present invention being placed in the metal electrode stripping device with the flat side of the wafer facing upwards;

[0045] Figure 6 It is a schematic diagram of the flower basket of the present invention being placed in the metal electrode stripping device with the flat side of the wafer facing downward;

[0046] Figure 7 It is a schematic diagram of the wafer of the present invention being placed in a flower basket with its flat side facing upwards;

[0047] Figure 8 This is a schematic diagram of the rounded shape of the present invention placed with the flat side facing downwards in a flower basket;

[0048] Fig. 9 It is a schematic diagram of the abutment cooperation between the side wall of the wafer and the roller of the present invention;

[0049] Fig.10 The figure is a flow chart of the metal electrode stripping method of the present invention.

[0050] Description of labels:

[0051] 1. Wafer; 2. Epitaxial layer; 3. Photoresist layer; 4. Cylinder; 5. Roller platform; 51. Roller base; 52. Flower basket slot; 53. Flower basket baffle; 54. Roller baffle; 55. Limit baffle; 56. First row of liquid tanks; 57. Second row of liquid tanks; 6. Roller; 61. Roller bracket; 7. Rotating bracket; 71. Handle; 8. Flower basket; 9. Flat edge. DETAILED DESCRIPTION

[0052] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0053] like Figure 1-10 As shown, the present invention provides a method for stripping a metal electrode of a solar cell, comprising:

[0054] S1. Epitaxial growth of GaAs multi-junction cells:

[0055] A substrate wafer 1 is provided, and an epitaxial layer 2 is grown on the substrate wafer 1 to form a semi-finished chip.

[0056] Optionally, the substrate wafer 1 is a Ge substrate, and growing the epitaxial layer 2 on the substrate wafer 1 to form a semi-finished chip specifically includes:

[0057] Through MOCVD equipment, Ge bottom cells, InGaAs middle cells and GaInP top cells are grown in sequence on the Ge substrate to complete the epitaxial growth of the Ge substrate and form a semi-finished chip.

[0058] S2. Organic cleaning of semi-finished chips:

[0059] After the epitaxial layer 2 is grown, the semi-finished chip is soaked in acetone for 10 minutes and in isopropanol for 10 minutes, then rinsed with water and spun dry at high speed.

[0060] S3, photolithography process:

[0061] Only a layer of negative photoresist is spin-coated on the surface of the epitaxial layer 2 of the semi-finished chip to form a photoresist layer 3, which is then baked, exposed, developed, and hardened and baked to form a graphic interface required for the metal electrode pattern on the photoresist layer 3.

[0062] Optionally, the thickness of the photoresist layer 3 is 3 μm, and the steps of baking, exposure, development, and post-baking for hardening the film specifically include:

[0063] The semi-finished chip with negative photoresist was placed in an oven and baked at 100°C for 30 minutes. Then, it was exposed through a mask in an exposure machine. The exposure intensity was 100 mJ / cm 2 ; Then, soak in the developer for 1 minute to remove the photoresist in the mask shielding area; finally, put it in the oven and bake it at 100℃ for 30 minutes to harden the film.

[0064] The present invention only applies a layer of photoresist without secondary exposure. By controlling the film thickness, exposure intensity, development time, etc. of the photoresist, the desired graphic interface can be formed. The graphic interface is preferably an inverted trapezoid. The specific structure can be referred to Figure 1 .

[0065] S4, Evaporation of metal electrode:

[0066] A metal electrode is evaporated on the surface of the epitaxial layer 2 with a graphic interface (i.e., the front side of the wafer 1), and the thickness of the metal electrode is controlled to be smaller than the thickness of the photoresist layer 3. The height difference formed by the photoresist layer 3 and the metal electrode realizes the separation between the metal electrode and the photoresist, as well as the separation between the required metal electrode and the metal to be stripped, without the need for secondary exposure of the reverse photoresist process or repeated photolithography of multiple layers of photoresist.

[0067] Optionally, evaporating a metal electrode on the surface of the epitaxial layer 2 having a graphic interface specifically includes:

[0068] The semi-finished chip with a graphic interface is placed in a metal coating machine, and Au, AuGe, Ni, and Au are evaporated on the surface of the epitaxial layer 2 with the graphic interface by electron beam evaporation, with thicknesses of 150nm, 90nm, 120nm, and 600nm respectively, to complete the preparation of the metal electrode. The thickness of the metal electrode is 960nm, which is less than the thickness of the photoresist layer 3, thereby achieving a height difference between the two, so that the required metal electrode and the photoresist layer 3, as well as the required metal electrode and the metal to be stripped are not adhered to each other, which is convenient for subsequent metal stripping.

[0069] S5. Metal electrode stripping:

[0070] Prepare a metal electrode stripping device. The specific structure can be referred to Figure 2-9The metal electrode stripping device is a metal electrode stripping device for immersing and stripping metal electrodes provided by the present invention, including a cylinder body 4, a roller platform 5, a roller 6, and a rotating bracket 7. The cylinder body 4 contains a photoresist stripping liquid, and the photoresist stripping liquid is acetone or other organic solution that can strip metal. The roller platform 5 is placed in the cylinder body 4, and a roller base 51 supporting the roller platform 5 is provided at the bottom of the roller platform 5. The roller 6 is mounted at the center of the roller platform 5 by a roller bracket 61. The roller platform 5 is provided with a flower basket slot 52 for inserting the supporting foot of the flower basket 8 on the outer periphery of the roller 6. The flower basket slot 52 can limit the flower basket 8 to prevent the flower basket 8 from moving. The flower basket 8 is provided with a plurality of slots for inserting the wafer 1, and the bottom of the flower basket 8 is hollow. After the wafer 1 is inserted into the slot, the supporting foot of the flower basket is placed into the flower basket slot 52, and the side wall of the wafer 1 will abut against the roller 6; the rotating bracket 7 is arranged on the side wall of the cylinder body 4, and the rotating shaft at the center of the roller 6 is connected to the rotating bracket 7. The rotating bracket 7 extends out of the outer wall of the cylinder body 4, and a handle 71 for driving the roller 6 to rotate is provided on the outer part of the cylinder body 4. Turning the handle 71 can drive the roller 6 to rotate. Fig. 9 As shown, since the side wall of the wafer 1 is in contact with the roller 6 , the roller 6 can drive the wafer 1 to rotate while rotating due to the friction between the roller 6 and the wafer 1 .

[0071] After preparing the metal electrode stripping device, refer to Figure 5 and Figure 7 , take a plurality of wafers with metal electrodes evaporated thereon and put them into the basket 8 with the flat edges 9 facing upwards, insert the basket 8 into the basket slot 52, so that the side wall of the wafer 1 abuts against the roller 6. At this time, the flat edge 9 of the wafer faces upwards, and the side wall of the wafer opposite to the flat edge 9 abuts against the roller 6, and the basket 8 and the wafer 1 will be immersed in the photoresist stripping solution, specifically for 15 minutes. During this process, the metal in the upper part of the wafer 1 near the flat edge 9 will slowly fall off from the surface of the wafer 1 and float in the stripping solution, but the metal in the lower part of the wafer 1 away from the flat edge 9 is not completely stripped, so the roller 6 should be rotated next, so that the roller 6 drives the wafer 1 to rotate slowly until the flat edge 9 of the wafer 1 faces downwards, and then soaks for 15 minutes. The specific structure can be referred to Figure 6 and Figure 8 In this process, the area of ​​wafer 1 away from flat edge 9 rotates to the upper part. At this time, the glue layer in this area can fully react with the stripping liquid, and the metal on the photoresist is also smoothly stripped from wafer 1, achieving complete stripping of the metal electrode in the non-graphic area (except the graphic interface) on wafer 1.

[0072] Optionally, the roller platform 5 is further provided with two flower basket baffles 53, two roller baffles 54 and two limit baffles 55, the two flower basket baffles 53 are respectively arranged on the front and rear sides of the roller 6, the roller baffle 54 is arranged between the flower basket baffle 53 and the roller 6, the roller baffle 54 separates the roller 6, and a flower basket slot 52 is formed between the flower basket baffle 53 and the limit baffle 55, the flower basket slot 52 can prevent the flower basket 8 from moving forward and backward and tipping over, in addition, two limit baffles 55 are respectively arranged on the left and right sides of the roller 6, the limit baffles 55 can limit the left and right movement of the flower basket 8 to prevent the flower basket 8 from sliding off the roller platform 5.

[0073] Optionally, a first liquid drain groove 56 is opened in the middle of the basket baffle 53, and the two ends of the basket baffle 53 are not connected to the two limit baffles 55, but are spaced to form a second liquid drain groove 57. The basket baffle 53 and the limit baffle 55 enclose a stripping space. The first liquid drain groove 56 and the second liquid drain groove 57 can circulate the photoresist stripping liquid inside and outside the stripping space to prevent the reactants in the stripping process from accumulating in the stripping space and affecting the stripping of the metal. The first liquid drain groove 56 and the second liquid drain groove 57 can be square grooves or other shaped grooves or hole-like structures, which are not limited here.

[0074] Optionally, the cylinder body 4 is a quartz cylinder made of quartz, which has high strength and corrosion resistance. All parts of the roller platform 5 and the roller 6 are made of polytetrafluoroethylene, which can withstand the corrosion of strong acids, strong alkalis and organic solvents, and have good wear resistance, insulation and non-stick properties, which not only meets the specific needs of metal electrode stripping, but also improves the service life and expands the application range of the metal electrode stripping device in metal stripping of semiconductor devices.

[0075] Optionally, after the metal electrode stripping is completed, the flower basket 8 needs to be taken out of the stripping solution, and then placed in a water bath to rinse with water to wash away a small amount of metal wire that has fallen off and is hanging on the flower basket 8. Then, the flower basket 8 is immersed in acetone and isopropanol in turn, soaking for 10 minutes respectively, and then rinsed and spun dry before proceeding with subsequent processes.

[0076] S6, proceed with subsequent processes:

[0077] Etching and electrode vapor deposition are performed on the back side of wafer 1 (i.e. the side of wafer 1 opposite to epitaxial layer 2). The N-pole electrode is made on the front side of wafer 1 and needs to be patterned, while the P-pole electrode is made on the back side of wafer 1 and does not need to be patterned and can be vapor deposited on the entire surface. Then, selective etching and vapor deposition of anti-reflection film are performed on the front side of wafer 1, followed by annealing. Then, the front side of wafer 1 is protected by glue, cut, and end-etched. Finally, IV testing is performed to complete the production of solar cell chips.

[0078] In summary, the present invention provides a method and device for stripping a metal electrode of a solar cell. In the photolithography process, only one layer of photoresist is applied without secondary exposure. The expected inverted trapezoidal graphic interface can be achieved by adjusting the thickness, exposure intensity and development time of the photoresist layer 3. Then, a metal electrode with a thickness less than that of the photoresist layer 3 is evaporated, so as to achieve the purpose of non-adhesion between the required metal electrode and the photoresist layer 3, and between the required metal electrode and the metal to be stripped. Then, a metal electrode stripping device with a roller 6 is used to rotate the wafer 1, so that the photoresist layer 3 and the photoresist stripping liquid fully react, thereby driving the metal on the photoresist to be evenly and completely detached. No additional manual operation is required for stripping, thereby reducing production costs and improving production efficiency.

[0079] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0080] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for stripping a metal electrode of a solar cell, characterized in that: include: Providing a substrate wafer, and growing an epitaxial layer on the substrate wafer to form a semi-finished chip; A layer of negative photoresist is spin-coated on the epitaxial layer surface of the semi-finished chip to form a photoresist layer, and then baked, exposed, developed, and hardened to form an inverted trapezoidal graphic interface on the photoresist layer; A metal electrode is deposited on the surface of the epitaxial layer with a graphic interface, wherein the thickness of the metal electrode is less than the thickness of the photoresist layer, so that the desired metal electrode and the photoresist layer, as well as the desired metal electrode and the metal to be stripped, are not adhered to each other; A metal electrode stripping device is prepared, the metal electrode stripping device comprises a cylinder, a roller platform, and a roller, the cylinder contains a photoresist stripping liquid, the roller platform is placed in the cylinder, the roller is rotatably arranged on the roller platform, and the roller platform is provided with a basket slot on the periphery of the roller; Take a number of wafers with metal electrodes deposited thereon and place them in a basket with their flat sides facing upwards, insert the basket into the basket slot, make the side walls of the wafer contact the roller, and immerse the basket in the photoresist stripping solution. The basket is immersed in the photoresist stripping solution for 15 minutes, and the metal electrodes in the area near the flat edge of the wafer fall off. Then, rotate the roller, and the roller drives the wafer to rotate slowly until the flat edge of the wafer faces downwards. Then, immerse the wafer for another 15 minutes to detach the metal electrodes in the area far from the flat edge of the wafer. The wafer from which the metal electrode has been stripped is cleaned and subjected to subsequent processes to complete the production of the solar cell chip.

2. A method for stripping a metal electrode of a solar cell according to claim 1, characterized in that: The substrate wafer is a Ge substrate, and growing an epitaxial layer on the substrate wafer to form a semi-finished chip includes: A Ge bottom cell, an InGaAs middle cell and a GaInP top cell are grown sequentially on a Ge substrate using MOCVD equipment.

3. A method for stripping a metal electrode of a solar cell according to claim 1, characterized in that: After the epitaxial layer is grown, the semi-finished chip is soaked in acetone for 10 minutes and in isopropanol for 10 minutes, then rinsed with water and spun dry at high speed.

4. A method for stripping a metal electrode of a solar cell according to claim 1, characterized in that: The thickness of the photoresist layer is 3 μm, and the steps of baking, exposure, development, and hardening the film include: The semi-finished chip with negative photoresist was placed in an oven and baked at 100°C for 30 minutes. Then, it was exposed through a mask in an exposure machine. The exposure intensity was 100 mJ / cm 2 ; Then, soak in the developer for 1 minute to remove the photoresist in the mask shielding area; finally, put it in the oven and bake it at 100℃ for 30 minutes to harden the film.

5. The method for stripping a metal electrode of a solar cell according to claim 1, characterized in that: The process of evaporating a metal electrode on the surface of an epitaxial layer having a graphic interface includes: The semi-finished chip with a graphic interface is placed in a metal coating machine, and Au, AuGe, Ni, and Au are evaporated on the surface of the epitaxial layer with the graphic interface by electron beam evaporation, with thicknesses of 150nm, 90nm, 120nm, and 600nm respectively, to complete the preparation of the metal electrode.

6. A method for stripping a metal electrode of a solar cell according to claim 1, characterized in that: The wafer stripped of the metal electrode is cleaned and the subsequent processes include: The flower basket is taken out of the photoresist stripping solution, and is placed in a water bath to rinse with water to wash away the metal wire that has fallen off the flower basket; the flower basket is then immersed in acetone and isopropanol in turn for 10 minutes each, and then rinsed and spun dry; Etching and electrode vapor deposition are performed on the back of the wafer, followed by selective etching and vapor deposition of anti-reflection film on the front of the wafer, followed by annealing, and then gluing protection, cutting, and end corrosion are performed on the front of the wafer. Finally, IV testing is performed to complete the production of solar cell chips.

7. A metal electrode stripping device for a solar cell, the stripping device being a metal electrode stripping device used in the metal electrode stripping method according to any one of claims 1 to 6, characterized in that: It includes a cylinder body, a roller platform, a roller, and a rotating bracket. The cylinder body contains photoresist stripping liquid. The roller platform is arranged in the cylinder body. The roller is rotatably arranged on the roller platform. The roller platform is provided with a flower basket slot for inserting a flower basket supporting foot on the outer periphery of the roller. The side wall of the wafer inside the flower basket abuts against the roller. The rotating bracket is arranged on the side wall of the cylinder body. The rotating shaft at the center of the roller is connected to the rotating bracket. The rotating bracket is provided with a handle for driving the roller to rotate.

8. The metal electrode stripping device for a solar cell according to claim 7, characterized in that: The roller platform is also provided with two flower basket baffles, two roller baffles and two limit baffles, the two flower basket baffles are respectively arranged on the front and rear sides of the roller, the roller baffle is arranged between the flower basket baffle and the roller, a flower basket slot is formed between the flower basket baffle and the limit baffle, and the two limit baffles are respectively arranged on the left and right sides of the roller.

9. A metal electrode stripping device for a solar cell as claimed in claim 8, characterized in that: A first liquid drain groove is provided in the middle of the flower basket baffle, and a second liquid drain groove is formed by leaving a gap between the two ends of the flower basket baffle and the two limit baffles.

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