JPS61500756A - Process for the preparation of cathodically depositable aqueous dispersions containing crosslinking agents based on polyisocyanates blocked with amino groups - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed description of the invention] [Name of invention] How to manufacture solar cells [Background of the invention] This work is a continuation of U.S. Patent Application No. 563.061, filed December 19, 1983. No. 659,279, filed October 10, 1984, This is a continuation application.

This research focuses on the manufacturing method of photovoltaic cells (photovoltaic cells), especially on hydrogen passivation measures. The fractured surface layer generated during the process is used as a plating mask in the final plating process. The present invention relates to an improved low-cost manufacturing method for polycrystalline silicon solar cells used in industrial applications.

Until now, the common method of manufacturing silicon solar cells has been to use silicon wafers. Or diffuse a suitable beapant against the front surface of the ribbon and form a Etching the grid electrode pattern on the dielectric masking for protection , all silicon exposed by etching is plated with nickel, and this A dielectric masking layer is layered from the front surface by over-plating the metal with copper and tin. Remove the remainder and apply an anti-reflective coating to the newly exposed portion of the front surface. The method includes a step of forming a pPN junction.

These manufacturing processes apply equally to both monocrystalline and polycrystalline silicon. However, due to cost considerations, it is better to manufacture solar cells using the latter method. desirable. However, as is well known, loss of minority carriers at grain boundaries, dislocation etc., the efficiency achieved in polycrystalline silicon solar cells is generally higher than that of monocrystalline cells. In the case of yoshi is also inferior. This situation makes monovalent elements such as hydrogen structurally minority carriers by generating structures that bind to the defect-associated conjunctival junctions. This has been improved by minimizing recombination loss.

As is well known in the art, an important consideration in structuring a cell's processing sequence is the Any combination of time and temperature in any step following the primary passivation step will The hydrogen introduced must not again diffuse out of the passivated substrate. this For example, hydrogen depletion exposed to a temperature of 600°C for 0.5 hours in vacuum The mobilization cell loses nearly all bound hydrogen and its observed electron beam is return to its pre-passivation level, as evidenced by its current level of activity. It turns out. In this regard, the junction diffusion process in the manufacture of solar cells is It should be noted that temperatures typically include temperatures of

Additionally, hydrogen passivation measures are usually sufficient to displace base metals such as copper from the junction. By heating the cell to high temperatures, a "soft" diode or short circuit can be created. It was also found that it occurs.

C, H, Seager, D, J, 5harp, J+, G, Pa n1tz and R, V, D’ Aiellc “Vacuum Science and Technology Journal” As shown in "Naru" No. 20 Dono 3, pages 430-435 (March 1982) , the passivation of polycrystalline silicon involves the generation of a hydrogen ion beam of kiloelectron volts. The Kaufman 111 ion generation source used in You can get it. High ion energies and fluxes (e.g. relatively short exposure times (e.g. 05-3 mA) at 77 mouths 2). A range of 2 to 4 minutes) is considered to be optimal. If such exposure is done, the board is carefully If the board is brought into contact with a suitable heat sink, it will generally reduce the temperature of the board to at least This results in an increase in temperature to approximately 275°C. Otherwise, temperatures exceeding 400℃ easily achieved. However, the temperature increases the steepness of the base metal relative to the silicon matrix. It is important that the temperature is limited to below about 300°C to avoid rapid migration. Ru. However, the substrate and heat sink for thermal control during the passivation procedure manual operation facilitates high-throughput operations with such ion sources. This is a limiting factor in the speed at which The result is a low-cost, high-throughput process. It is desirable to avoid heat sink operations.

Furthermore, in the case of EFG silicon ribbons that can be made economically, one surface Irregularities make heat sink operation difficult.

Furthermore, the hydrogen passivation operation is most efficient when the silicon surface of the substrate is exposed. be. For this reason, whatever is used to define the front grid electrode pattern Plating masks must also be removed before or added after the passivation operation. stomach.

[Purpose of the invention]

Therefore, it is an object of the present invention that the hydrogen passivation step is performed after a high temperature treatment step. Moreover, the process for manufacturing solar cells is carried out before base metals are included in the structure. It is provided by.

Another object of the invention is to remove the silica underside of the electrode structure on the front side of the partially formed cell. Hydrogen passivation process to improve silicon and nickel silicon passivation methods It is a further object of the present invention to incorporate open substrate heating of passivation measures. EFG silicon ribbon in a manner that avoids the need to perform sink operations. The aim is to incorporate a hydrogen passivation process into the solar cell processing process.

[Detailed description of the invention]

The above and other objects are desirable as applied as a method of manufacturing silicon solar cells. In some embodiments, the following steps, among others: (1) Shallow bonding silicon ribbon Form a thin grid electrode pattern of nickel (or similar material) on the front surface of the (2) Perform hydrogen passivation on the joining side of the cell, (3) Sinter the nickel. (4) covered another metal with the cell metal. (5) Anti-reflective coating on the exposed silicone surface. This is achieved by a process that includes the step of applying After that, the silicon is further processed. , for example, to be coupled to an electrical circuit.

Alternatively, in another process, heating the sample during the passivation operation is performed using nickel. Provides energy for the sintering process.

Such manufacturing methods bear several main characteristics. First, the applicant proposes that hydrogen During the passivation operation, the impinging hydrogen ions destroy the metal by immersion plating onto the metamorphic surface. discovered that it alters the surface of silicon wafers in a way that prevents plating. So As a result, the tampering machining machine that was first used to chamfer the front grid electrode chisel turn The mask can be removed after the first metal layer is plated onto the substrate. Passivity Passivation is then performed on the exposed silicon substrate, and passivation modifies the performance of the cell. Not only does it improve the surface layer, but it also prevents secondary immersion plating in the subsequent immersion plating process. Acts as a plating mask. As a result, the passivation of the exposed silicon substrate is Requires an extra masking process prior to metallization treatment for dip plating Can be done without attachment of base metals. Furthermore, the applicant also believes that passivation It has been found that this can occur over thin layers of metals such as nickel. In this way, before Silicon and nickel silicate defects below the first thin nickel plating of the plane O electrode. Dynamicization can be performed.

Other objects of the invention may be apparent in part or may be set forth below in the text. It will become clear. Therefore, some steps and the following details are not invented. One or more such steps with respect to each other exemplified in this disclosure. The scope of application thereof is indicated in the claims.

[Brief explanation of the drawing]

For a better understanding of the nature and purpose of the invention, preferred embodiments of the invention are described below. Below are drawings showing the many steps involved in the production of solar cells according to Please check the detailed description.

In all drawings), the same reference number indicates the same structure.

In the drawings, the thickness and depth of some coatings and areas are as shown. A scale that does not follow a fixed scale for stools, but precisely follows its relative proportions. This is not what is shown.

[Detailed description of the invention]

Next, in the drawings, a desirable embodiment of the present invention is a P type grown by the EFG method. The present invention relates to a method of manufacturing solar cells from bonded silicon ribbons. In this embodiment In this case, a partially completed cell 1 is provided as a starting piece. partially completed Cell 1 has a relatively shallow junction 4 (approximately 3,000 to 7,000 people) on one side. is preferably formed from a P-type conductive silicon ribbon with a depth of a new substrate 2 and a conductive region 6 of Nq.

It has a mask 8. The mask 8 is made of a material to which metal such as nickel slightly adheres ( For example, if the front surface of the board 2 is made up of many branched grids 9, poles (e.g., one electrode has the configuration shown in U.S. Pat. No. 3,686,036) It exhibits a form that is exposed to a pattern of The other side of this board (see text below) The aluminum layer 10 alloyed with the substrate and the P It is desirable that a + region 12 be provided.

Preferably, the P+ region 12 has a depth in the range of about 1 to 5 microns.

The partially completed cell 1 may be processed by any of a number of means known in the art. It can be manufactured using In other words, junction 4 and region 6 have P due to phosphorus diffusion. The silicon base [2] of the mold can be formed, and the mask 8 can be formed using the photophosphorographic method or can be formed on its front surface by a printing method. Layer 10 and P+ region 12 is a volatile organic compound such as terpineol that can be removed by evaporation on the backside of the substrate. Coated with an aluminum yeast layer consisting of aluminum powder in a carrier and then Heat the baking sheet to remove volatile or thermally decomposable organic compounds from the paste. Polymer is formed by alloying aluminum to the substrate to form a P+ region. be able to. However, other forms of substrates, bonding and backside electrodes, and other The manufacturing method can also be used to provide partially completed cells I as well.

Starting with such a pre-prepared part, first plate both sides of the board with nickel. The adhesive deposit of nickel is deposited on the rear side of the member over the entire area of the aluminum layer 10. A nickel layer 14 is formed on the front side, but adhesive precipitation of nickel on the front side is performed through a mask 8. A layer 16 is formed directly on the surface of the substrate 2 only on the areas exposed by the step.

Plating the nickel layers 14 and 16 can be accomplished in a variety of ways. Well-known wireless Reaction or dip plating methods, such as K Pate:L et al., U.S. Pat. No. 4,321, Preferably, this is done by an immersion plating method similar to that described in No. 283. Yes. In this text, the term "electroless plating" refers to an externally applied electric field. Refers to a plating method with a bath containing a reducing agent without the use of ``Plating method'' is a method of retaining a reducing agent on an object without using an externally applied electric field. means the process of plating metal by immersion in a plating bath without Plating involves a displacement action.

As a preliminary step, the surface of the cleaned silicon substrate is pre-activated using an appropriate chemical. Be sexualized. In this preactivation method, the silicon surface itself supports electroless plating. Nickel plated on an untreated surface will generally have a slight contact with this It is desirable for wearing clothes. As an activator, platinum chloride, tin chloride salt palladium chloride, or %j as shown in U.S. Pat. No. 3,489,603. Gold chloride is used as the activator, although other well-known activators, such as, may also be used. after that, Both sides of the silicone ribbon are preferably as described in U.S. Pat. No. 4,321,283. or nickel sulfamate with a pH of about 29 as described in and ammonium fluoride in an aqueous bath at about room temperature for a period of about 2 to 6 minutes. The ribbon is coated with a nickel layer by dip plating.

At this stage, the mask 8 is peeled off from the substrate 2. According to the nature of the mask, This stripping can be accomplished by any of a number of known methods, such as by using buffer etching. It can be done by

As a result of removing the mask, the front surface of the substrate 2 is covered with a grid electrode formed by the nickel layer 16. exposed along a polar pattern.

Next, the cell is passivated with hydrogen. A desirable method is to and the front surface of the nickel layer 16) is located approximately 15c7n from the substrate. exposed to a hydrogen ion beam from a wide beam ion source.

This ion source can be operated at pressures in the range of approximately 20 to 50 mTorr (hydrogen). with a hydrogen flow rate of 25 to 405 ccQi per minute, approximately 1.700 ccQi between source and substrate. At a potential of DC volts, and at the substrate, approximately 1 to 3 milliamps (A/crn) It is desirable to operate with a beam dose within the range of 2. A short time of about 1 to 4 minutes However, in the case of the E1'G method silicon cell (about 20 to 80μ depth, that is, the depth of junction 4) at the same time that the exposed edge of the substrate 2 is while providing a metamorphosed surface layer 18 at a depth of approximately 200X units to the together sufficient to minimize the minority carrier recombination losses typically experienced. It turned out to be. Additionally, the ion beam is cut off at 50% of the usage cycle. As a result of using a mechanical shutter to create a It was also found that the rise in temperature was kept to a minimum.

The exact nature of the metamorphosed surface layer 18 is unknown. However, the crystal structure is slightly collapsed. A portion of the silicon removed is removed from the ion beam to form SiH or SIH. 2, but the material is thought to be in the fracture phase, which is probably amorphous. Ru. For the formation of the required metamorphosed surface layer, a small amount of carbon or one or more Hydrocarbons are required. Kaufmann's used as originally assembled The ion source has a graphite support stage approximately 13 cm (5 inches) in diameter. on top of which typically 5 to 10 cm (2 to 4 inches) of substrate is placed inside one side. placed in the center. If a silicon support stage is provided in place of this graphite stage, , a metamorphic layer plating mask and a metamorphic layer formed as when graphite stages are used. It will not form. Based on this, the hydrogen ion beam on graphite The carbon or hydrocarbons produced by the collisions enhance the formation of a dielectric layer on the surface of the substrate. A hypothesis was made. Approximately 1400 to 1700 volts, regardless of its nature. This process with an accelerating voltage in the range of The metamorphic surface layer 18 is formed by subsequent immersion plating of the silicon substrate between the nickel layer 16. It was found to be sufficient to prevent

Next, the substrate is sintered in an inert gas, i.e. nitrogen atmosphere, to form a nickel layer on the front side of the substrate. The nickel layer 16 in the nickel silicate layer 16 is reacted with the adjacent silicon to form a nickel silicate heated to a certain temperature for a sufficient time to form contact. For this purpose, Preferably, the substrate is heated to a temperature of about 300° C. for about 15 to 40 minutes. child Therefore, the gap between the nickel layer 16 and the substrate 2 is approximately equal to the nickel silicate layer 20. Produces a depth of 200X units. The rear nickel layer 14 is connected to the aluminum layer 10. Forms an alloy.

As the temperature of this sintering process increases, the nickel layer 1 relative to silicon increases. The temperature should not be much higher than 300°C as this will result in excessive penetration of 6. This heat treatment is 1, if performed in the form of antigas (95% nitrogen and 5% hydrogen) By peeling off hydrogen loosely bonded to the nickel layer 16, subsequent plating is prevented. seems to strengthen the adhesion of

Following this, the nickel in layers 14 and 16 is etched with hot dilute nitric acid. followed by ultrasonic cleaning to remove excess nickel from both sides of the substrate. do. This nickel etching is not a way to remove excess nickel; Part of the nickel-aluminum alloy formed at 9.j during the bonding process was removed. I also leave. After the nickel etching step, the layer 14 is replaced by the aluminum electrode layer 1. Features a nickel-aluminum alloy layer overlapping 0, but 1 layer 16 is selected in advance To expose the nickel silicate layer 20 corresponding to the grid electrode pattern It will be peeled off.

After that, the nickel silicate layer 20 and nickel-aluminiumized are applied. Provides contact conditions. In such a metallization process, the substrate 2 is metamorphosed. The surface layer 18 acts as a plating mask to cover the nickel silicate layer to which metal has already been deposited. This prevents the salt layer 20 from adhering to the surface of the substrate between the -ξ turns. This other a metallization step results in the deposition of a second layer of nickel to layer 14.20. Although this is not an essential requirement, it is desirable. A further nickel layer is nickel layer 14. In connection with the formation of No. 16, it is impregnated by dip plating in the above method. Is this by dip plating? It adheres on the nickel layer 14.16, but on the metamorphic surface 18. This is because it does not stick. Immediately thereafter, one or more layers of copper (dip plating and (or → by electroplating methods, by various techniques well known in the art) The exposed nickel is coated on both sides of the substrate and bonded to the nickel layer. This also protects these layers from oxidation and ensures high electrical conductivity. Copper metal It is not necessary to provide a mask to the modified surface layer 18 for cleaning. This is a strange pot. This is because it does not adhere to the stratification. After that, the resulting product is processed in other ways for well-known purposes. For example, on a metal layer previously applied with a tin and solder layer. It can also be attached continuously. Following the metallization process, the edges of the cell (oral 2) and an anti-reflective coating 26 is applied to the front side of the cell. After this This process can be carried out by a number of known methods, such as TlO2 chemical vapor deposition. can become. Alternatively, the anti-reflective coating 26 is made of silicon nitrite. It can be formed by a salt plasma deposition method.

As an example, a preferred method of carrying out the invention is described in detail for each step. carrying out the individual steps as described above in a suitable manner and in the sequence described above; Consists of things.

The preferred method of the present invention includes the individual preferred steps described in detail: 1. these It will be appreciated that the steps are performed in the order indicated in the text.

Solar cells made according to the above process IC from ribbons grown by the EFG method have an average efficiency of It has been found that there is a 10-20% increase in rate. Furthermore, such substances The hydrogen passivation step was also found to significantly narrow the cell efficiency distribution in Ta.

The above process has many other points of interest. First, immersion plating method, e.g. The immobility of hydrogen is used as a mask for subsequent plating using the nickel plating method as described below. Upon use of the modified surface layer of the substrate that occurs during the transformation operation, the present method allows passivation measures of the exposed substrate prior to the metallization step.

For this purpose, a passivation operation on a clean substrate (passivation operation through a plating mask layer) is required. (instead of Avoid short-circuited batteries.

And since no further masking process is required, the passivation method is suitable for immersion plating. This aims to improve the economic efficiency of various processes between the metallization process and the subsequent metallization process. The above-mentioned hydrogen The mobilization area is also a mass that prevents copper deposition by immersion or electroplating. It also acts as a check. Furthermore, passivation measures are taken through a thin layer of front electrode material. By applying a You can do the following. Additionally, the method of the present invention allows the subsequent treatment of the battery to passivate. Including passivation operations at the stage of battery production, which do not adversely affect the effectiveness of the operation. It will also be understood that

Many modifications may be made to this process without departing from the scope of the invention as described herein. It will be understood that this can be done.

For this reason, in the preferred embodiment; (in the nickel sintering step 12 passivation step) Although performed subsequently, this sintering step can also be performed immediately before the passivation operation. . In such cases, batteries with shallow junctions should be provided with a suitable heat sink. Maintains anti-migration against nickel silicate bonds, regardless of thermal management of the substrate. A short ion beam exposure is desirable for verification. Such control also applies to other Ni□S1 instead of NiSi or N15t. The silicide molecules contain relatively little silicon, and the N0 region is completely covered by silicides. guarantees prevention of infiltration. Also, if the nickel sintering operation is performed before the passivation operation If carried out, the loosely bound hydrogen should be removed by addition of nickel prior to further processing. It is understood that a passivation operation may be followed by a torrefaction step for release. Good morning.

Additionally, the heating of the cell during the passivation operation performs at least part of the nickel sintering process. It will also be clear that it can be used to

Still further, a preferred embodiment of the method of the invention eliminates the previously plated nickel. Formed by hydrogen passivation to mask the subsequent nickel plating. This method utilizes a metamorphosed surface layer that is They can also be used together. For example, for shallow junctions, as will be understood by those skilled in the art. The first layer of the front electrode in a silicon device can be formed by various methods well known to those skilled in the art. to form ohmic contact (preferably at low temperature) and further processing. Many metals deposited in pots or other materials can act as a barrier to diffusion of metals. Any substance with a relatively small reaction can be attached by plating. Ru. Suitable metals used with copper include.

Includes palladium, platinum, cobalt, rhodium, and nickel. child All of these materials form silicides, but a silicide layer is not necessary.

However, if the first metal layer adheres properly and provides ohmic contact, then the act as a barrier to metal migration, and prevent significant migration to the bond itself. It is important that this does not occur.

Thermal theory, the process provided by the present invention is for the production of solar cells from substrates using the EFG method. It is not limited to. Thus, for example, cast polycrystalline line base plates, Epitaxial silicon on silicon at metallurgical processing level or chemical or ( 2. Physical vapor deposition method 1. The fine-level polysilicon layer formed by can be used for the formation of solar cells with relatively high DNS. Also, this professional The process is applicable to single crystal silicon. Furthermore, one process is N type. It can also be carried out using a P-type junction material.

In the process described above without departing from the scope of the invention contained herein. and all matters contained in the text and drawings, subject to other changes. are illustrative and should not be construed in a limiting sense.

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Claims (12)

[Claims] 1. In a method of manufacturing a solid-state semiconductor device, (a) first and second (b) hydrogen ion beams of a certain strength; forming a surface layer on said first surface to which the selected metal slightly adheres to the film; exposing the selected area of the first surface for a period of time sufficient to (c) coating said first surface, excluding said selected areas, with a small amount of said selected metal; A method comprising at least one metallizing step in this order. 2. Claim 1, comprising the step of forming a bond between the substrate adjacent to the first surface. The method described in Section 1. 3. The element is a photovoltaic cell, and the first surface is coated with a non-reflective coating. The method according to claim 1, comprising the step of attaching. 4. The metallization treatment includes nickel, palladium, cobalt, platinum and The claims are made of a metal selected from the group of metals including rhodium. The method described in box 1. 5. In a method of manufacturing a solid-state semiconductor device, (a) first and second a junction having opposing surfaces and adjacent to the first surface; and a selected portion of the first surface. (b) providing a silicon substrate having a plating mask that exposes a portion of the silicon substrate; Apply aluminum coating to the second side, (c) combining the aluminum of the aluminum coating with the silicon substrate; heating the silicon substrate to a certain temperature for a sufficient time to convert it into gold; (d) applying a nickel coating to said selected portions of said first side; height, (e) removing the plating mask; (f) For a hydrogen ion beam of a certain intensity, the value of the selected conductive metal the first surface for a period of time sufficient to form a surface layer on the first surface to be bonded; (g) exposing the surface of the nickel and silicon in the selected area; At its interface the nickel reacts to form nickel silicate. - sintering the coating, and (h) said nickel and aluminum coating. covering the ring with at least one layer of said conductive metal. Method. 6. said at least one layer (a) for removing unbonded nickel; (b) contacting said nickel coating with an etchant; Claim 5 attached by further covering the nickel coating with copper Method described. 7. Claims including the step of applying the anti-reflection coating to the first surface. The method described in box 5. 8. further exposing the substrate to the hydrogen ion beam; The time and intensity are sufficient to reduce the minority carrier loss of claim 5. How to put it on. 9. In a method of manufacturing a solid-state semiconductor device, (a) first and second a junction having opposing surfaces and adjacent to the first surface; and a selected portion of the first surface. (b) providing a silicon substrate having a plating mask that exposes a portion of the silicon substrate; applying a nickel coating to the selected portions of the face of 1; (c) removing the plating mask; (d) The first metal slightly adheres to the hydrogen ion beam of a certain chord size. exposing the first surface for a period of time sufficient to form a surface layer on the surface; (a) the nickel and silicon in the selected region are at the boundary; The above nickel coating reacts to form a nickel silicate. and (f) sintering said nickel coating with at least one other conductor. A method comprising the steps of covering with an electrically conductive metal layer in this order. 10. said at least one further conductive metal layer is formed by dip plating. 10. The method of claim 9, comprising nickel footwear made of nickel. 11. A claim in which the plating method uses a bath consisting of nickelate and fluoride ions. The method according to item 10. 12. Said at least one further conductive metal layer is formed by dip plating or electroplating. 8. The method of claim 7, comprising a single layer of copper formed by a plating process.