JP4996025B2 - Manufacturing method of solar cell - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for manufacturing a solar cell, and more particularly to a technique for realizing a system with high power generation efficiency by removing a high impurity concentration region on a semiconductor surface.
[0002]
[Prior art]
In recent years, the mainstream of solar cells for electric power has become silicon solar cells made of silicon, but the spread of the solar cells requires reduction of product cost. Improving the power generation efficiency of solar cells can be said to be a means of reducing product prices. Moreover, there is an additional advantage that the installation area can be reduced by using a solar cell device having high power generation efficiency.
[0003]
5 and 6 are diagrams showing a conventional and generally performed manufacturing process of a solar cell. In FIG. 5, reference numeral 101 denotes a p-type Si substrate, and reference numeral 102 denotes an n-type diffusion layer formed on the p-type Si substrate 101. Reference numeral 102 a denotes phosphorous glass formed on the surface portion of the n-type diffusion layer 102, and reference numeral 103 denotes an insulating film that functions as an antireflection film formed on the n-type diffusion layer 102.
[0004]
In FIG. 6, 104 is a front electrode formed so as to be connected to the n-type diffusion layer 102, and 105 is a back electrode formed on the back surface of the p-type Si substrate 101. Reference numeral 106 denotes a filler film made of EVA (Ethylene Vinyl Acetate) or the like formed so as to cover the front electrode 104, and 107 is a glass plate formed on the filler film 106.
[0005]
First, the p-type Si substrate 101 shown in FIG. 5A is used, and as shown in FIG. 5B, for example, phosphorus is thermally diffused into the surface portion of the p-type Si substrate 101 to thereby change the conductivity type. An n-type diffusion layer 102 made of inverted phosphorus-containing silicon is formed on the surface portion of the p-type Si substrate 101. At this time, the n-type diffusion layer 102 is formed on the entire surface of the Si substrate 101, and a phosphorus glass 102a made of a compound containing phosphorus and oxygen or a part of the diffusion source is formed on the surface portion of the n-type diffusion layer 102.
[0006]
It should be noted that the n-type diffusion layer 102 is formed on the entire surface of the p-type Si substrate 101 unless there is a particular technique such as a photographic technique or a selective film formation technique. Next, as shown in FIG. 5C, the phosphorus glass 102a generated on the surface portion of the n-type diffusion layer 102 is removed by etching by dipping in a hydrofluoric acid aqueous solution. Next, as shown in FIG. 5D, the n-type diffusion layer 102 is selectively etched away so as to leave the n-type diffusion layer 102 only on one main surface of the p-type Si substrate 101.
[0007]
Next, as illustrated in FIG. 6A, an insulating film 103 that functions as an antireflection film is formed over the n-type diffusion layer 102. Since the insulating film 103 functions as an antireflection film, the performance of the solar cell device is improved. Thereafter, as shown in FIG. 6B, a silver paste or the like is applied over the insulating film 103, and the silver paste is formed into a predetermined pattern shape by a printing technique. Form. The surface electrode 104 is connected to the n-type diffusion layer 102 through the insulating film 103 by firing.
[0008]
Further, as shown in FIG. 6B, silver aluminum or aluminum paste is applied to the back surface of the p-type Si substrate 101 and formed into a predetermined pattern shape by a printing technique, and then the metal pattern is baked to form p. A back electrode 105 is formed on the back surface of the mold Si substrate 101. Then, by sequentially forming a filler film 106 such as EVA and a glass plate 107 so as to cover the surface electrode 104, a solar cell device having a structure as shown in FIG. 6C can be obtained.
[0009]
The formation of the n-type diffusion layer 102 in a conventional solar cell device is generally performed by thermally diffusing gas, liquid, or solid on the surface of the substrate 101. In this case, the n-type diffusion layer 102 has a distribution in which the phosphorus impurity concentration in the surface portion is high and the phosphorus impurity concentration decreases toward the inside.
[0010]
Thus, when forming a pn junction of a silicon solar cell, if a high impurity concentration region of phosphorus is generated on the surface portion of the diffusion layer 102, the device performance of the solar cell is degraded. For this reason, the performance of the solar cell device can be improved by removing the high impurity concentration region of phosphorus generated on the surface portion of the diffusion layer 102.
[0011]
Conventionally, methods for removing the high impurity concentration region of phosphorus include plasma etching, etching with an aqueous solution containing hydrofluoric acid (HF) and nitric acid (HNO3), and fluorination of an oxide film formed on the surface. A method of removing with a hydrogen acid (HF) aqueous solution, etc.
[0012]
[Problems to be solved by the invention]
However, in the conventional solar cell manufacturing method as described above, in order to improve the performance of the solar cell device, the high concentration impurity region on the surface of the n-type diffusion layer 102 is removed by etching or fluorination using plasma. Etching with an aqueous solution in which hydrogen acid (HF) and nitric acid (HNO3) are mixed, and an oxide film formed on the surface is removed with an aqueous hydrofluoric acid (HF) solution.
[0013]
Since plasma etching physically etches the substrate, it easily damages the substrate surface. Etching with an aqueous solution in which hydrofluoric acid (HF) and nitric acid (HNO3) are mixed is accompanied by an exothermic reaction at the time of preparing a chemical solution and etching, and the etching rate of the substrate is easily accelerated. For this reason, the entire n-type diffusion layer 102 required for forming the pn junction is easily etched, the substrate surface is easily damaged, and a problem remains in that good device characteristics are obtained.
[0014]
In addition, as described above, the conventional solar cell manufacturing method is difficult to apply to mass production due to the stability of the aqueous solution and the complicated manufacturing process, such as an exothermic reaction during chemical preparation and etching. Therefore, the high concentration region of the surface portion of the diffusion layer 102 often remains without being etched, and there is a problem that it is difficult to improve the solar cell performance.
[0015]
Therefore, the present invention makes it possible to easily etch only the high concentration region on the surface of the diffusion layer so that the entire diffusion layer is not etched, making it difficult to cause damage to the substrate surface, and good device characteristics. It is an object to provide a method for producing a solar cell capable of obtaining
[0016]
[Means for Solving the Problems]
The method of manufacturing a solar cell according to the present invention includes a step of forming a second conductive type diffusion layer by introducing an impurity into a surface portion of a first conductive type semiconductor substrate and diffusing the impurity, and the second conductive type. And a step of immersing the diffusion layer in an aqueous solution in which hydrofluoric acid and hydrogen peroxide are mixed.
[0017]
In the solar cell manufacturing method, the hydrogen fluoride concentration of the aqueous solution is 0.01 to 5% by weight.
[0018]
In the solar cell manufacturing method, the hydrogen peroxide concentration of the aqueous solution is higher than the concentration of hydrofluoric acid in the aqueous solution.
[0019]
In the solar cell manufacturing method, the temperature of the aqueous solution is 5 to 35 ° C.
[0020]
In the method for producing a solar cell, the treatment time immersed in the aqueous solution is within 10 minutes.
[0021]
In the method for manufacturing a solar cell, the diffusion layer has a sheet resistance of 30 to 100Ω / □.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Embodiment 1 FIG.
1 and 2 are diagrams showing a method for manufacturing a solar cell according to Embodiment 1 of the present invention. 1 and 2, reference numeral 1 denotes a p-type Si substrate, and reference numeral 2 denotes an n-type diffusion layer formed on the p-type Si substrate 1. Reference numeral 2a denotes phosphorous glass formed on the surface portion of the n-type diffusion layer 2, and reference numeral 3 denotes an insulating film made of silicon nitride or the like that functions as an antireflection film formed on the n-type diffusion layer 2.
[0023]
Reference numeral 4 denotes a front electrode made of silver or the like formed so as to be connected to the n-type diffusion layer 2, and reference numeral 5 denotes a back electrode made of silver aluminum or aluminum formed on the back surface of the p-type Si substrate 1. Reference numeral 6 denotes a filler film made of EVA (Ethylene Vinyl Acetate) or the like formed so as to cover the front electrode 4, and 7 is a glass plate formed on the filler film 6.
[0024]
As the substrate 1, for example, a single crystal silicon substrate manufactured by a pulling method or a polycrystalline silicon substrate manufactured by a casting method is usually used. In the solar cell in the present embodiment, substrate 1 made of polycrystalline silicon is used, and substrate 1 that is sliced from an ingot is used. The conductivity type is p-type, but n-type may be used.
[0025]
In order to remove the mechanically altered layer and dirt on the surface of the p-type Si substrate 1 generated in this slicing step, an alkaline aqueous solution such as potassium hydroxide or aqueous sodium hydroxide solution or a mixed solution of hydrofluoric acid and nitric acid is used. The surface of the substrate 1 is etched by about 5 to 20 μm (FIG. 1A). Furthermore, in order to remove heavy metals such as iron adhering to the surface of the substrate 1, a step of washing with a mixed solution of hydrochloric acid and hydrogen peroxide may be added.
[0026]
Next, using the cleaned p-type Si substrate 1 shown in FIG. 1A, as shown in FIG. 1B, for example, thermal diffusion using phosphorus oxychloride (POCl3) to form a pn junction. Accordingly, by thermally diffusing phosphorus into the p-type Si substrate 1 surface portion, an n-type diffusion layer 2 consisting of phosphorus-containing silicon obtained by inverting the conductivity type, formed on the p-type Si substrate 1 surface portion.
[0027]
At this time, the n-type diffusion layer 2 is formed on the entire surface of the p-type Si substrate 1 , and a phosphorus glass 2a made of a compound containing phosphorus and oxygen or a part of the diffusion source is generated on the surface portion of the n-type diffusion layer 2 . In the present embodiment, since the substrate 1 to be used is configured as a p-type, the n-type diffusion layer 2 is formed on the surface of the p-type Si substrate 1 in order to form a pn junction.
[0028]
As a method of forming the n-type diffusion layer 2, thermal diffusion using phosphorus oxychloride (POCl3) was used, but other methods include, for example, SOD (Spin-On-Dopant), PSG (Phospho-Slicate-Glass). In general, phosphoric acid (H3PO4), phosphorous acid (H3PO3), hypophosphorous acid (H3PO2), phosphoric acid aqueous solutions such as metaphosphoric acid (HPO3), or film diffusion sources are used as diffusion sources. The n-type diffusion layer 2 may be formed on the surface of the p-type Si substrate 1 by attaching an impurity containing phosphorus to the surface of the p-type Si substrate 1 under appropriate diffusion conditions and thermally diffusing it.
[0029]
As a method for attaching impurities including phosphorus to the surface of the substrate 1, any method such as gas (gas), spin coating, spraying, roll coating, and immersion may be used. In any case, when thermal diffusion is performed by attaching a diffusion source to the surface of the p-type Si substrate 1 as described above, the n-type diffusion layer 2 formed on the surface of the p-type Si substrate 1 The phosphorus concentration is high, and the phosphorus concentration decreases as the distance from the surface portion increases. If the sheet resistance of the n-type diffusion layer 2 is less than 30 Ω / □, the cell efficiency is lowered, for example, the photocurrent is lowered.
[0030]
Further, when the sheet resistance of the n-type diffusion layer 2 is larger than 100Ω / □, the junction depth becomes shallower and the contact with the surface electrode 4 (ohmic contact) is reduced, such as FF (curve factor) is reduced. It becomes difficult and not preferable. Therefore, by configuring the sheet resistance of the n-type diffusion layer 2 at 30 to 100Ω / □, it is possible to achieve good cell efficiency and to easily make good contact with the surface electrode 4.
[0031]
Next, as shown in FIG. 1C, the phosphorus glass 2a formed on the n-type diffusion layer 2 after phosphorus diffusion is removed by etching with a hydrofluoric acid aqueous solution, and an n-type diffusion layer made of phosphorus-containing silicon is used. 2 is exposed. The hydrofluoric acid aqueous solution etches the phosphor glass 2a but does not etch silicon, so that only the phosphor glass 2a can be selectively etched. The phosphorus glass 2a is made of a compound containing phosphorus and oxygen or a residual material of a diffusion source.
[0032]
Here, the phosphor glass 2a is described as being etched away with a hydrofluoric acid aqueous solution. However, phosphorous glass 2a is obtained by using an aqueous solution obtained by mixing hydrofluoric acid and hydrogen peroxide water, which will be described in the next step. The glass 2a may be configured to be removed by etching. According to this method, the etching step using the hydrofluoric acid aqueous solution described in FIG. 1C can be omitted.
[0033]
Next, as shown in FIG. 1C, the p-type Si substrate 1 having the n-type diffusion layer 2 formed on the surface portion is immersed in an aqueous solution in which hydrofluoric acid and hydrogen peroxide are mixed. As a result, the high concentration impurity region in the surface portion of the n-type diffusion layer 2 having a high phosphorus concentration is removed by etching. This process is called an etch back process. This etch-back process includes a silicon oxidation process using hydrogen peroxide and a silicon oxide film etching process using hydrofluoric acid, as shown in FIG. 3 showing the chemical reaction of the etch-back process in the diffusion layer 2. It consists of two stages of processing.
[0034]
The n-type diffusion layer 2 made of phosphorus-containing silicon can be etched slowly by the etch-back process including the two stages of the silicon oxidation process and the silicon oxide film etching process. Therefore, the entire n-type diffusion layer 2 is not etched all at once, but only the surface portion of the n-type diffusion layer 2 which is a high concentration region of phosphorus can be easily etched. Therefore, the entire n-type diffusion layer 2 necessary for forming the pn junction can be prevented from being etched, and good device characteristics can be obtained.
[0035]
For example, in the case of the n-type diffusion layer 2 having a sheet resistance of 30 to 100Ω / □, if the high concentration impurity region of phosphorus on the surface portion of the diffusion layer 2 is left without being etched, the diffusion layer 2 The phosphorus concentration on the surface becomes as high as 1E + 20 cm −3 or more, causing an increase in the carrier recombination rate and a decrease in the amount of incident light, leading to a decrease in performance of the solar cell device. According to the present embodiment, since only the high-concentration impurity region on the surface portion of n-type diffusion layer 2 can be removed, the performance of the solar cell device can be improved.
[0036]
In addition, since the chemical solution of an aqueous solution in which hydrofluoric acid and hydrogen peroxide are mixed does not cause an exothermic reaction, there is no change in temperature at the time of chemical solution preparation or etching. For this reason, there is no increase in the etching rate due to a temperature increase change, and stable etching can be performed. Further, the etch-back process in the present embodiment does not require heating and can be realized at room temperature. Therefore, no heating equipment or the like is required, and the apparatus cost can be reduced.
[0037]
In addition, the above etch-back process can be realized in a short time even with a low concentration chemical solution, so that the manufacturing throughput is high and the manufacturing cost can be reduced. In addition, since the above etch-back process allows the etching to proceed slowly, the etching amount can be easily controlled, and a predetermined sheet resistance of the solar cell device can be easily realized. For this reason, a freedom degree can be increased in electrode material and an electrode pattern design.
[0038]
When etching back with an aqueous solution in which hydrofluoric acid and hydrogen peroxide are mixed, if the concentration of hydrogen fluoride in the aqueous solution is less than 0.01% by weight, taking too much etching time, etc. It is not preferable in terms of etching time and chemical life. On the other hand, when the hydrogen fluoride concentration of the aqueous solution is larger than 5% by weight, the etching rate of the diffusion layer 2 (substrate 1) is increased, which is not preferable in terms of damage to the diffusion layer 2. Therefore, it is preferable that the concentration of hydrogen fluoride in the aqueous solution is 0.01 to 5% by weight so that diffusion layer etching excellent in mass productivity can be realized without causing damage to the diffusion layer 2.
[0039]
When etching back, the concentration of hydrogen peroxide in the aqueous solution is set higher than the concentration of hydrofluoric acid in the aqueous solution. Thereby, the silicon oxidation by the hydrogen peroxide solution can be promoted sufficiently, and an appropriate etching rate can be determined by changing the hydrofluoric acid. When the temperature of the aqueous solution is lower than 5 ° C., the etching rate is undesirably reduced, and when the temperature is higher than 35 ° C., the etching rate is increased, which is not preferable in terms of damage to the diffusion layer 2. Therefore, it is preferable that the temperature of the aqueous solution is 5 to 35 ° C. because an appropriate etching rate can be obtained.
[0040]
If the treatment time immersed in the aqueous solution is longer than 10 minutes, it becomes easy to etch all of the diffusion layer 2, which is not preferable in terms of damage to the diffusion layer 2. Therefore, the treatment time immersed in the aqueous solution is preferably within 10 minutes, so that the diffusion layer 2 can be appropriately etched.
[0041]
The preferable conditions for the etch back described above are determined as conditions that do not damage the surface of the diffusion layer 2. Further, as a measure of the etching amount, it can be said that measuring the increase in sheet resistance is a simple method. That is, the greater the increase in sheet resistance, the greater the etching amount and the lower the phosphorus concentration on the surface. As a result, the desired effect is increased, but there is a disadvantage that good contact with the electrode cannot be obtained.
[0042]
Accordingly, when selecting each etch back condition, although there is a great deal of technical restrictions on the electrode forming process, the increase in sheet resistance is generally 0.1% within a range that does not damage the surface of the diffusion layer 2. It is preferable to set appropriately so as to be in the range of 20Ω / □.
[0043]
The pn junction separation is a process performed so that the back electrode 5 serving as the p electrode and the front electrode 4 serving as the n electrode do not short-circuit. As shown in FIG. 1D, the same chemical solution as that used for etching the surface of the substrate 1 obtained in the above-described slicing step is used to leave the n-type diffusion layer 2 only on one main surface of the p-type Si substrate 1. Thus, the n-type diffusion layer 2 is selectively etched.
[0044]
As a method for removing the unnecessary n-type diffusion layer 2 other than the main surface of the substrate 1, other than the method described above, etching by plasma or mechanical method by sandblasting may be used. Further, when the diffusion region is selectively formed, such as diffusion represented by a method of attaching SOD or the like only to one surface of the substrate 1, the above-described pn junction isolation step can be omitted.
[0045]
Next, as shown in FIG. 2A, an insulating film 3 functioning as an antireflection film is formed on the n-type diffusion layer 2. Since the insulating film 3 serving as the antireflection film reduces the surface reflectance with respect to the incident light of the solar cell, the generated current can be increased. For example, when a silicon nitride film is applied to the insulating film 3 serving as the antireflection film, the formation method can be formed using a low pressure thermal CVD method or a plasma CVD method.
[0046]
When a silicon nitride film is formed by a thermal CVD method, dichlorosilane (SiCl2H2) and ammonia (NH3) are often used as source gases. At this time, for example, the film formation is performed under the film formation conditions in which the gas flow ratio is NH3 / SiCl2H2 = 10 to 20, the pressure in the reaction chamber is 0.2 to 0.5 Torr, and the film formation temperature is 760 ° C.
[0047]
When a silicon nitride film is formed by plasma CVD, a mixed gas of SiH4 and NH3 is generally used as a source gas. As film formation conditions, for example, the gas flow rate ratio is NH3 / SiH4 = 0.5 to 1.5, the pressure in the reaction chamber is 1 to 2 Torr, and the film formation temperature is 300 to 550C. Further, a frequency of a high frequency power source necessary for plasma discharge is suitably several hundred kHz or more.
[0048]
Next, as shown in FIG. 2 (B), a silver paste or the like is applied onto the insulating film 3, and the silver paste is formed into a predetermined pattern shape by a screen printing technique. The surface electrode 4 to be an n-electrode is formed by baking at a temperature of several tens of seconds to several minutes. The front electrode 4 penetrates the insulating film 3 by firing and is ohmically connected to the n-type diffusion layer 2.
[0049]
Further, as shown in FIG. 2B, silver aluminum or aluminum paste is applied to the back surface of the p-type Si substrate 1 and formed into a predetermined pattern shape by a screen printing technique. Baking is performed at a temperature of 0 ° C. for several tens of seconds to several minutes to form a back electrode 5 serving as a p-electrode on the back surface of the p-type Si substrate 1. The back electrode 5 is ohmically connected to the p-type Si substrate 1 by firing.
[0050]
Then, by sequentially forming a filler film 6 such as EVA and a glass plate 7 so as to cover the surface electrode 4 , a solar cell device having a structure as shown in FIG. 2C can be obtained. Here, FIG. 4 is a diagram showing the device characteristics of the solar cell produced as described above and the solar cell produced by the conventional method (comparative example). In FIG. 4, Voc is an open circuit voltage, Jsc is a short-circuit current, FF is a fill factor, and Eff is power generation efficiency.
[0051]
The comparative example is a solar cell in which phosphorous glass generated on the surface of the n-type diffusion layer is etched with an aqueous hydrofluoric acid solution, and the high concentration impurity region on the surface portion of the n-type diffusion layer is not removed. is there. Other manufacturing processes are the same as in the present embodiment. Note that the hydrofluoric acid aqueous solution does not etch silicon and therefore does not have the ability to remove the n-type diffusion layer.
[0052]
The solar cell of the present invention has an open circuit voltage higher than that of the solar cell of the comparative example. In the solar cell of the present invention, it is presumed that the surface recombination rate of carriers is reduced by etching a region having a high phosphorus concentration in the diffusion layer 2, and the open circuit voltage is increased as compared with the solar cell of the comparative example. The
[0053]
In the solar cell of the present invention, the short-circuit current is increased and the power generation efficiency is higher than that of the solar cell of the comparative example. In the solar cell of the present invention, in addition to the decrease in the surface recombination rate, it is presumed that the short circuit current is increased as compared with the solar cell of the comparative example due to the increase in the amount of incident light. The solar cell of the present invention has higher power generation efficiency than the solar cell of the comparative example, and it has been found that the device performance of the solar cell is improved. Therefore, according to the solar cell of the present invention, the product cost can be reduced and desired power can be obtained even in a small area.
[0054]
【Effect of the invention】
According to the present invention, after the impurity is introduced into the surface portion of the first conductivity type semiconductor substrate and diffused to form the second conductivity type diffusion layer, the second conductivity type diffusion layer is then fluorinated. By performing the immersion treatment with an aqueous solution in which hydrogen acid and hydrogen peroxide are mixed, two-stage treatment of silicon oxidation with hydrogen peroxide and silicon oxide film etching with hydrofluoric acid is performed. Can be etched slowly. For this reason, only the surface part which is a high concentration area | region of a diffused layer can be etched, and the damage to a board | substrate can be reduced significantly. In addition, since the chemical solution of an aqueous solution in which hydrofluoric acid and hydrogen peroxide are mixed does not cause an exothermic reaction, there is no change in temperature at the time of chemical solution preparation or etching. For this reason, there is no increase in the etching rate due to a temperature increase change, and stable etching can be performed.
[0055]
If the concentration of hydrogen fluoride in the aqueous solution is less than 0.01% by weight, taking into account the mass productivity such as excessive etching time, it is not preferable in terms of etching time and chemical life. On the other hand, when the hydrogen fluoride concentration of the aqueous solution is larger than 5% by weight, the etching rate of the substrate is increased, which is not preferable in terms of damage to the substrate. Therefore, when the concentration of hydrogen fluoride in the aqueous solution is 0.01 to 5% by weight, substrate etching excellent in mass productivity can be realized without causing damage to the substrate.
[0056]
By making the hydrogen peroxide concentration of the aqueous solution higher than the concentration of hydrofluoric acid in the aqueous solution, the silicon oxidation by the hydrogen peroxide solution can be promoted abundantly. I can decide.
[0057]
When the temperature of the aqueous solution is lower than 5 ° C., the etching rate decreases, which is not preferable. When the temperature of the aqueous solution is higher than 35 ° C., the etching rate increases, which is not preferable in terms of damage to the substrate. Therefore, by setting the temperature of the aqueous solution at 5 to 35 ° C., an appropriate etching rate can be obtained.
[0058]
When the treatment time immersed in the aqueous solution is longer than 10 minutes, it becomes easy to etch all the diffusion layers, which is not preferable in terms of damage to the substrate. Therefore, the diffusion layer can be appropriately etched by configuring the treatment time to be immersed in the aqueous solution within 10 minutes.
[0059]
If the sheet resistance of the diffusion layer is less than 30 Ω / □, the cell efficiency is lowered, such as a decrease in photocurrent, which is not preferable. On the other hand, if the sheet resistance of the diffusion layer is larger than 100 Ω / □, it is difficult to make contact with the surface electrode (ohmic contact) because FF (curve factor) and the like are lowered. Therefore, by configuring the sheet resistance of the diffusion layer at 30 to 100Ω / □, it is possible to achieve good cell efficiency and to easily make good contact with the surface electrode.
[Brief description of the drawings]
FIG. 1 is a diagram showing a method for manufacturing a solar cell in a first embodiment according to the present invention.
FIG. 2 is a diagram showing a method for manufacturing a solar cell in the first embodiment according to the present invention.
3 is a diagram showing a chemical reaction of an etch back process in the diffusion layer shown in FIG. 1. FIG.
FIG. 4 is a diagram showing a characteristic effect when etching back is performed in the present invention / comparative example.
FIG. 5 is a diagram showing a conventional method for manufacturing a solar cell.
FIG. 6 is a diagram showing a conventional method for manufacturing a solar cell.
[Explanation of symbols]
1 p-type Si substrate, 2 n-type diffusion layer, 2a phosphorous glass, 3 antireflection film, 4 surface electrode, 5 back electrode, 6 filler film, 7 glass film.

Claims (5)

A first step of forming a second conductivity type diffusion layer by introducing and diffusing phosphorus into the surface portion of the first conductivity type P-type Si substrate;
And a second step of etching the surface portion of the diffusion layer of the second conductivity type with an aqueous solution in which hydrofluoric acid and hydrogen peroxide are mixed,
The second step is performed after the first step without a thermal oxidation step, and the concentration of hydrogen peroxide in the aqueous solution is higher than the concentration of hydrofluoric acid in the aqueous solution. Production method.   2. The method for manufacturing a solar cell according to claim 1, wherein the concentration of hydrogen fluoride in the aqueous solution is 0.01 to 5% by weight.   3. The method for manufacturing a solar cell according to claim 1, wherein the temperature of the aqueous solution is 5 to 35 ° C. 4.   4. The method for manufacturing a solar cell according to claim 1, wherein a treatment time immersed in the aqueous solution is within 10 minutes.   5. The method of manufacturing a solar cell according to claim 1, wherein the diffusion layer has a sheet resistance of 30 to 100Ω / □. 6.

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