JPH10173208A - Manufacture of solar cell - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method capable of manufacturing a solar cell simply and at low cost, which reduces a dark current in the cell and can raise the low-illuminance characteristics and photoelectric conversion efficiency of the cell. SOLUTION: A method of manufacturing a solar cell comprises a process, wherein a dopant agent is applied on the light-receiving surfaces of semiconductor substrates 1 by a spin coating method, the dopant-coated rears 20 of the substrates 1 are superposed 6n each other to heat-treat the rears 20, whereby while the dopant agent 3 is prevented from being diffused in the rears, diffused layers are respectively formed in the light-receiving surfaces 19 only.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a solar cell, and more particularly to a method for forming a diffusion layer on a light-receiving surface of a semiconductor substrate for a solar cell by using a spin coating method.
The present invention relates to a method for manufacturing a solar cell capable of preventing diffusion of a dopant agent to the back surface of a semiconductor substrate by a simple process.

[0002]

2. Description of the Related Art With reference to FIGS. 15 to 25, an example of a manufacturing process of a conventional single crystal substrate type solar cell will be described.

First, in FIG. 15, a p-type single-crystal Si substrate 1 having a main surface composed of a (100) crystal plane is prepared.

In FIG. 16, both principal surfaces of a substrate 1 are converted into a textured surface 2 including fine pyramid-shaped irregularities by anisotropic etching. This texture surface 2
Acts to confine the light incident on the substrate 1 within the substrate 1.

In FIG. 17, a dopant agent 3 including a diffusion source such as phosphorus and an antireflection film source such as titanium is applied to a substrate 1.
Is applied from the light-receiving surface side by a spin coating method. In this spin coating method, first, as shown in FIG. 21, a certain amount of the dopant agent 3 is discharged from the dopant nozzle 5 to the center of the stationary substrate 1. And FIG.
As shown by 2, after retracting the dopant nozzle 5, the substrate 1 is rotated at a high speed of about 5000 rpm to uniformly spread the dopant agent 3 over the entire light receiving surface of the substrate 1 on which the surface texture 2 is formed. The solvent component is dried.
At this time, as shown in FIG. 23, the excess dopant agent instantaneously collects in the periphery 7 of the substrate 1, and especially around the corner 7a, the dopant agent wrapped around the back surface of the substrate by high-speed rotation. Part 6 occurs.

As shown in FIG. 24, the plurality of semiconductor substrates on which the dopant agent has been applied are arranged in a predetermined direction on the quartz boat 16 so that about 90
Heat treatment is performed in a furnace at a high temperature of 0 ° C. for several tens minutes. At this time,
Atmosphere gases such as N ₂ and O ₂ are flowing in the furnace as indicated by arrows 15. For example, the light receiving surface 19 of the first substrate is close to the back surface 20 of the second substrate. ing. In a high-temperature furnace, the diffusion source also diffuses into the atmosphere and reaches the back surface 20 of the adjacent cell as indicated by arrow 18 or is included in the gas flow as indicated by arrow 17 And flow between the substrates.

As a result, as shown in FIG.
An n ⁺ diffusion layer 1 is formed on the light receiving surface of the semiconductor substrate 1 after the heat treatment.
In addition to the formation of the anti-reflection film 12 containing titanium and titanium, the n ⁺ diffusion layer portion 11a and the back surface of the dopant material diffused in the atmosphere in the heat treatment furnace are formed on the periphery of the back surface of the substrate 1 due to the wraparound of the dopant material. The n-type diffusion layer 14 having a small thickness is formed.

In FIG. 19, an aluminum electrode 21 and a silver electrode 22 are formed on the back surface of the substrate 1 by a printing method.
The silver electrode 23 is formed on the light receiving surface of the. At this time, the n ⁺ diffusion layer portion 11a and the n-type diffusion layer 14 on the back surface of the substrate 1 are in contact with the aluminum electrode 21 on the back surface of the substrate 1.

Thereafter, as shown in FIG. 20, the metal electrodes 21, 22 and 23 and S
An electrical contact with the i-substrate 1 is formed. That is, during this heat treatment, the silver electrode 23 on the light receiving surface becomes an electrode that penetrates the antireflection film 12 and is bonded to the n ⁺ diffusion layer 11. On the other hand, Al atoms diffuse from the aluminum electrode on the back surface into the Si substrate to form ap ⁺ diffusion layer 25. At this time, the n ⁺ layer region 11a on the back surface, the n type diffusion layer 14 and the p ⁺ diffusion layer 25 are formed. P / n short part 2 at the part where
6 results.

As can be seen from FIG. 23, a pseudo-quadrilateral single crystal Si substrate cut from a round ingot (for example, about 12 mm cut from a round ingot having a diameter of about 150 mm).
Although a small arc portion 7a remains at the peripheral portion 7 of the quadrilateral substrate having one side of 5 mm), the wraparound 6 of the dopant agent exists near the peripheral portion 7a and comes into contact with the aluminum electrode 21.

Finally, as shown in FIG. 20, the solar cells are completed by applying solder coatings 22a and 23a to silver electrodes 22 and 23, respectively.

[0012]

In the solar cell according to the conventional manufacturing method as described above, the dark current of the solar cell increases due to the p / n short portion on the back surface of the cell, and the fill factor deteriorates. There is a problem that the maximum output is slightly lower.

When the light has a low illuminance, the open-circuit voltage V _OC is further affected by the parallel resistance due to the dark current, and the amount of power generation at a low illuminance in a solar cell having a large dark current is slightly reduced.

Further, for the p / n short portion on the back surface of the cell, for example, after the diffusion process, the light receiving surface is covered with a resist or an acid-resistant tape or the like, and then the back surface Si is etched with a mixed acid of nitric acid and hydrofluoric acid. After that, if a step of peeling off the cover on the light receiving surface side is adopted, p / n is quite completely achieved.
The junctions can be separated, but such additional steps are not suitable for mass production of today's residential solar cells,
Manufacturing costs also increase.

In view of such problems in the prior art,
An object of the present invention is to provide a method capable of manufacturing a solar battery cell having sufficient photoelectric conversion characteristics relatively easily and at low cost.

[0016]

According to one aspect of the present invention, a method for manufacturing a solar cell including a crystalline semiconductor substrate is provided.
A dopant agent is applied on the light receiving surface of the semiconductor substrate by a spin coating method, and the back surfaces of the two semiconductor substrates coated with the dopant agent are overlapped and heat-treated to prevent the dopant agent from diffusing to the back surface. The method includes a step of forming a diffusion layer only on the light receiving surface, whereby the dark current of the solar cell can be reduced and the photoelectric conversion efficiency can be improved.

In a still further preferred method of manufacturing a solar cell according to the present invention, the method further comprises a step of spraying a dopant rinsing liquid on the back surface after the dopant agent is applied to the light-receiving surface of the semiconductor substrate. The method is characterized in that the dopant agent that has reached the back surface of the substrate is removed.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, various embodiments of a method for manufacturing a solar cell according to the present invention will be described with reference to the drawings.

First, in FIG. 1, a semiconductor substrate 1 having a (100) main surface is prepared as in the prior art, and a texture structure 2 is formed on both main surfaces. Then, a dopant agent 3 including a diffusion source such as phosphorus and an anti-reflection film source such as titanium is applied on the light receiving surface of the substrate 1 by a spin method. At this time, a predetermined amount of the dopant agent is discharged from the dopant nozzle to the center of the light receiving surface of the stationary substrate as in the case of FIG. 21, and after the dopant nozzle is retracted, about 5000 rpm as in the case of FIG.
The substrate 1 is rotated at a rotation speed of m, the dopant agent 3 is spread uniformly and thinly on the light receiving surface of the substrate 1, and the solvent component is dried.

Thereafter, the number of rotations of the substrate 1 is about 1000 rpm
m, as shown in FIG.
, The dopant rinse liquid 30 is sprayed on the back surface of the substrate, and the wraparound of the dopant agent generated on the back surface is removed. Then, the substrate 1 is again rotated at a high speed of about 5000 rpm, and the dopant rinse liquid is dried. Since the dopant rinsing liquid 30 is sprayed after the dopant on the light-receiving surface is dried, the dopant such as solidification of the dopant on the light-receiving surface does not deteriorate. Further, since the dopant rinsing liquid 30 is sprayed from the position 29 which is about 1 cm inside from the periphery of the substrate, the dopant rinsing liquid does not adversely affect the dopant agent on the light receiving surface, and the dopant rinsing liquid 30 An effect capable of removing the agent can be exerted.

As shown in FIG. 6, the semiconductor substrate having the light-receiving surface coated with the dopant agent is arranged such that the back surfaces 20 of the substrate are superimposed on the quartz boat 16 at a high temperature of about 900.degree. Heat treatment is performed for several tens minutes in the furnace.
In this case, it is possible to prevent the dopant agent on the light receiving surface 19 of the adjacent semiconductor substrate from being diffused in the atmosphere toward the rear surface.

Therefore, as shown in FIG. 2, in the semiconductor substrate subjected to the heat treatment, n ⁺ diffusion layer 11 and antireflection film 12 containing titanium or the like are formed only on the light receiving surface.

In FIG. 3, an aluminum electrode 21 and a silver electrode 22 are formed on the back surface of the substrate by a printing method, and a silver electrode 23 is formed on the light receiving surface. At this time, since there is no n ⁺ diffusion layer portion on the back surface of the substrate due to the wraparound of the dopant agent and the n-type diffusion layer on the back surface diffused in the atmosphere in the heat treatment furnace, as shown in FIG. It can be formed so as to be spread close to the peripheral edge 7 of the semiconductor substrate up to the limit 28 of the process accuracy within 0.5 mm.

In FIG. 4, metal electrodes 21, 22 and 23 are brought into electrical contact with Si substrate 1 by heat treatment at a high temperature. At this time, Al atoms diffuse from the aluminum electrode on the back surface of the substrate 1 into the Si substrate, and the p ⁺ diffusion layer 25 is formed. This p ⁺ diffusion layer 25
Acts to produce a BSF (Back Surface Field) effect. Thereafter, as shown in FIG. 4, the solder coatings 22a and 23 are applied to the silver electrodes 22 and 23, respectively.
is applied to complete the solar cell.

FIG. 8 shows the open-circuit voltage characteristics of the solar cell of FIG. 4 according to the present invention manufactured as described above and the solar cell of FIG. 20 manufactured by the conventional method. The horizontal axis in the graph of FIG. 8 represents the irradiance (W / m ² ) of the light applied to the solar cell, and the vertical axis represents the open-circuit voltage when the irradiance is 500 W / m ² by 100%.
Represents the irradiance dependence of the open-circuit voltage when Solid line curve 8A and broken line curve 8B represent the open-circuit voltage of the solar cell according to the manufacturing method of the present invention and the solar cell according to the conventional manufacturing method, respectively. As is clear from this graph, the solar cell manufactured by the method of the present invention has better open-circuit voltage characteristics in the low illuminance region than the solar cell manufactured by the conventional method.

As described above, according to the solar cell manufacturing method of the present invention, the diffusion of the dopant agent from the light-receiving surface side of the semiconductor substrate to the back surface is prevented by a simple process, and the p / n short-circuit on the back surface is achieved. Part formation can be prevented.
As a result, the dark current can be reduced, and the conversion efficiency and low illuminance characteristics of the solar cell can be improved.

Further, since the n ⁺ diffusion layer portion due to the wraparound of the dopant agent and the n-type diffusion layer due to the atmosphere diffusion in the heat treatment furnace are not formed on the back surface of the semiconductor substrate, the aluminum electrode is placed on the periphery of the semiconductor substrate due to the limit of the process accuracy. It can be spread out and formed. As a result, the BSF effect can be increased without increasing the dark current, and in particular, a solar cell with improved short-circuit current and improved conversion efficiency can be provided.

Further, according to the method for manufacturing a solar cell of the present invention, even when a substantially rectangular semiconductor substrate is used, a dark current is reduced, and a solar cell having low illuminance characteristics and improved conversion efficiency is obtained. Can be provided.

Further, by using a diluent of the dopant agent, preferably isopropyl alcohol, as the dopant rinsing liquid, the dopant agent wrapped around the back surface of the semiconductor substrate can be effectively removed.

Next, with reference to FIG. 9, a method of setting a semiconductor substrate having a light-receiving surface coated with a dopant agent on a diffusion boat will be described. First, the back surface of the semiconductor substrate 29 on which the dopant agent has been applied on the final stage 34 is sucked by the first transfer arm 30 and lifted upward as indicated by an arrow A1. Thereafter, the transfer arm 30 is moved to the arrow A2.
Is moved horizontally as shown in (1), and the arm is lowered by 90 ° from horizontal as shown by arrow A3. After the horizontal movement of the arm 30 as indicated by arrows A4 and A5, the semiconductor substrate 29 is set in the groove of the boat 16 by the downward movement of the arm as indicated by arrow A7. At this time, the boat 16
Is tilted by, for example, a wedge 31, so that the semiconductor substrate 29 is tilted so that its light receiving surface faces slightly downward.

Next, the second semiconductor substrate 32 to which the dopant agent has been applied is sucked by the second transfer arm 33, and the arrow A
The light receiving surface and the back surface of the second semiconductor substrate are inverted by rotating the tip of the arm by 180 ° as shown by 8, and then the second arm as shown by arrows A9 and A10 The second semiconductor substrate 32 is placed on the stage 34 by the horizontal movement and the vertical movement. afterwards,
As in the case where the first semiconductor substrate 29 is set in the boat 16, the second semiconductor substrate 32 is moved by the first transfer arm 30 in the same groove as the first semiconductor substrate 29 is set on the boat 16. Inserted into However, the back surface of the second semiconductor substrate 32 is turned rightward by the rotation A6 of the arm.

At this time, since the light receiving surface of the first semiconductor substrate 29 already set in the boat is slightly inclined downward, the end surfaces of the first and second semiconductor substrates may abut each other. Without the second semiconductor substrate 32
Can be inserted into the same groove in which the first semiconductor substrate 29 is inserted. As a result, the back surfaces of the first and second semiconductor substrates are overlapped and set in one groove of the boat 16. By repeating such an operation, a pair of semiconductor substrates whose back surfaces are overlaid on each of all the grooves of the diffusion boat can be set.

Referring to FIG. 10, another method of setting the semiconductor substrate for a solar cell in the diffusion boat 16 will be described. The light receiving surface of the first semiconductor substrate 29 on which the dopant agent is applied on the final stage 34 is moved to the first transfer arm 3.
At 0, it is conveyed upward as shown by arrow B1. Then, after the arm 30 is moved horizontally as indicated by an arrow B2, the arm is moved downward by 90 ° from the horizontal as indicated by an arrow B3. Then, as shown by arrows B4 and B5, the arm 30
After the horizontal movement, the first semiconductor substrate 29 is set in the groove of the boat 16 by vertical movement as indicated by an arrow B7. At this time, the boat 16 is placed slightly inclined with respect to the horizontal plane by the wedge 31 as in the case of FIG. Therefore, the light receiving surface of the first semiconductor substrate 29 set on the boat 16 is slightly inclined downward.

Next, after the second semiconductor substrate 32 on which the dopant agent is applied is transported onto the final stage 34,
As in the case of the first semiconductor substrate, the transfer is performed by the transfer arm 30 as indicated by arrows B1, B2, B3, B4, and B5. Then, the second semiconductor substrate 32 is rotated by the rotation of the arm as shown by the arrow B6.
Of the second semiconductor substrate 32 by vertical movement as shown by arrow B7.
Is inserted into the same groove in which the first semiconductor substrate 29 is set in the boat 16.

At this time, since the first semiconductor substrate 29 is inclined so that the light receiving surface is slightly downward, the end surfaces of the first and second semiconductor layers do not abut each other, and the second semiconductor substrate 29 is easily formed. The substrate can be set in the same groove so as to overlap the first semiconductor substrate. Thus, FIG.
As in the case of (1), the back surfaces of the first and second semiconductor substrates 29 and 32 are overlapped and set in one groove of the boat 16. By repeating such operations,
In each of the grooves of the diffusion boat 16, a pair of semiconductor substrates whose back surfaces are overlapped can be set.

Next, a method for removing a semiconductor substrate from the boat 16 will be described with reference to FIGS. First, the light is sucked by the first transfer arm 37 so as to sandwich the light receiving surfaces of the first semiconductor substrate 35 and the second semiconductor substrate 36, which are set with their back surfaces superposed in the same groove of the boat 16. , The two semiconductor substrates are simultaneously transferred to the boat 16.
Is pulled up as shown by the arrow C1. And
The axis of the arm 37 is made horizontal as indicated by an arrow C2, and is horizontally moved as indicated by arrows C3 and C4. Then, as shown by arrow C5,
The direction of the arm is rotated by 180 ° in the horizontal plane, and after the horizontal movement as shown by arrow C6, the two semiconductor substrates 35 and 36 are moved by the vertical movement as shown by arrow C7. 38.

The second semiconductor substrate 36 in contact with the stage 38 is fixed by suction as shown in FIG. 12, and is moved by the second transfer arm 39 to the second semiconductor substrate 36 as shown by an arrow C8 in FIG. The first semiconductor substrate 35 is slid to separate the two semiconductor substrates from each other.
5 to the next processing station. Thereafter, the second semiconductor substrate is sucked by the third arm 40 and lifted as shown by the arrow C9, and the light receiving surface and the back surface of the second semiconductor substrate 36 are further drawn as shown by the arrow C10. After inversion, the second semiconductor substrate 36 is sent to the next processing station.

As described above, by the method as shown in FIGS. 10 to 13, a pair of semiconductor substrates whose back surfaces are overlapped and set in each groove of the diffusion boat are freely taken out. After being separated from each other, each can be sent to the next processing station.

Finally, referring to FIG. 14, even if each semiconductor substrate is set in an individual groove without overlapping the back surfaces of the two semiconductor substrates, the back surface is contaminated by the dopant agent on the light receiving surface. Spread boats are shown that do not. The diffusion boat 16a has a partition wall 41 of a size that can cover the entire back surface of the semiconductor substrate for each groove. That is, by setting the back surface of the solar cell semiconductor substrate in the groove of the boat so as to be in contact with the partition wall 41, the semiconductor substrate can be prevented from being contaminated by the dopant on the light receiving surface of the semiconductor substrate. Heat treatment of the substrate can be performed.

[0040]

As described above, according to the present invention, it is possible to provide a solar cell with reduced dark current, improved illuminance characteristics and improved photoelectric conversion efficiency in a simple process and at low cost. .

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining a manufacturing process of a solar cell according to the present invention.

FIG. 2 is a schematic cross-sectional view for explaining a manufacturing process of a solar cell according to the present invention.

FIG. 3 is a schematic cross-sectional view for explaining a manufacturing process of a solar cell according to the present invention.

FIG. 4 is a schematic cross-sectional view for explaining a manufacturing process of a solar cell according to the present invention.

FIG. 5 is a schematic diagram for explaining a method of applying a dopant rinsing liquid to the back surface of the semiconductor substrate.

FIG. 6 is a schematic diagram for explaining a diffusion process in the method for manufacturing a solar cell according to the present invention.

FIG. 7 is a schematic plan partial view showing that a back electrode is formed up to near the periphery of the back surface of the semiconductor substrate in the method for manufacturing a solar cell according to the present invention.

FIG. 8 is a graph showing an open-circuit voltage characteristic of a solar cell manufactured by a manufacturing method according to the present invention, in comparison with a solar cell manufactured by a conventional manufacturing method.

FIG. 9 is a diagram for explaining an example of a method of setting the back surfaces of two semiconductor substrates so as to be superimposed on each other and set in each groove of a diffusion boat.

FIG. 10 is a view for explaining another example of a method of superposing the back surfaces of two semiconductor substrates on each other and setting them in each groove of the diffusion boat.

FIG. 11 is a view for explaining an example of a method of taking out a pair of semiconductor substrates set with their back surfaces superimposed on each other in each groove of the diffusion boat, separating each substrate, and sending the separated substrate to the next processing station; FIG.

FIG. 12 is a view for explaining an example of a method of taking out a pair of semiconductor substrates set with their back surfaces superimposed on each other in each groove of the diffusion boat, separating each substrate, and sending the separated substrate to the next processing station; FIG.

FIG. 13 is a view for explaining an example of a method of taking out a pair of semiconductor substrates set with their back surfaces superimposed on each other in each groove of the diffusion boat, separating each substrate, and sending the separated substrate to the next processing station. FIG.

FIG. 14 is a schematic perspective view of a diffusion boat provided with a partition plate covering the back surface of the semiconductor substrate for each groove.

FIG. 15 is a schematic cross-sectional view for explaining a conventional method for manufacturing a solar cell.

FIG. 16 is a schematic cross-sectional view for explaining a conventional method for manufacturing a solar cell.

FIG. 17 is a schematic cross-sectional view for explaining a conventional method for manufacturing a solar cell.

FIG. 18 is a schematic cross-sectional view for explaining a conventional method for manufacturing a solar cell.

FIG. 19 is a schematic cross-sectional view for explaining a conventional method for manufacturing a solar cell.

FIG. 20 is a schematic cross-sectional view for explaining a conventional method for manufacturing a solar cell.

FIG. 21 is a perspective view for explaining a method of applying a dopant agent on a light receiving surface of a semiconductor substrate by a spin coating method.

FIG. 22 is a schematic perspective view showing a step subsequent to FIG. 21 in the spin coating method.

FIG. 23 is a schematic plan partial view showing the wraparound of the dopant agent from the light receiving surface side to the back surface at the periphery of the semiconductor substrate.

FIG. 24 is a schematic diagram for explaining a conventional method of heat-treating a semiconductor substrate.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 semiconductor substrate 2 surface texture structure 3 dopant agent 11 n ⁺ -type diffusion layer 11b on light receiving surface of semiconductor substrate 11b n ⁺ -type region formed on back surface of semiconductor substrate 12 antireflection film 21 back surface aluminum electrode 22 back surface silver electrode 22a Solder coating layer 23 Light receiving surface silver electrode 23a Solder coating layer 25 p ⁺ type diffusion layer 30 Dopant rinse liquid 31 Nozzle 16, 16a Diffusion boat 19 Light receiving surface of semiconductor substrate 20 Back surface of semiconductor substrate

Claims (10)

[Claims] 1. A method for manufacturing a solar cell including a crystalline semiconductor substrate, comprising: applying a dopant to a light receiving surface of the semiconductor substrate by a spin coating method; and applying the dopant to the two semiconductor substrates. By performing heat treatment with the back surfaces of the photovoltaic cells overlapped with each other, a step of forming a diffusion layer only on the light receiving surface while preventing the dopant agent from diffusing to the back surface is performed, whereby the dark current of the solar cell is reduced. A method for producing a solar cell, wherein the photoelectric conversion efficiency can be reduced and the photoelectric conversion efficiency can be improved. 2. The method according to claim 1, further comprising the step of spraying a dopant rinsing liquid on the back surface of the semiconductor substrate after the dopant agent is applied, thereby removing the dopant agent wrapped around the back surface of the substrate in the spin coating method. The method for manufacturing a solar cell according to claim 1, wherein: 3. After the diffusion layer is formed on the light receiving surface, a 0.5 m
The method according to claim 2, further comprising the step of forming the back electrode widely until the distance is within about m, thereby improving the short-circuit current of the solar cell. 4. The method according to claim 1, wherein the semiconductor substrate has a substantially rectangular shape. 5. The method for manufacturing a solar cell according to claim 1, wherein a diluent of a dopant agent is used as the dopant rinsing liquid. 6. The method according to claim 5, wherein isopropyl alcohol is used as the dopant rinsing liquid. 7. A method of setting a semiconductor substrate for a solar cell on a diffusion boat, comprising: a groove of the diffusion boat placed at a slight angle with respect to a horizontal direction; (B) adsorbing and transporting the first semiconductor substrate coated with the dopant agent on the stage using a first transport arm and placing it on a stage; and (b) adsorbing and transporting the first semiconductor substrate with a second transport arm, (C) setting the first semiconductor substrate in the groove of the diffusion boat so that the first main surface is slightly inclined downward; (1) the first and second main surfaces of the second semiconductor substrate are inverted and placed on the stage by suction-transporting the first transport arm and rotating the distal end of the arm by 180 °; A second semiconductor substrate is sucked by the second transfer arm. Conveyed, since the first semiconductor substrate is set to be inclined, the first and the second without end faces of the semiconductor substrate abuts the second of said first and second semiconductor substrates
Setting the second semiconductor substrate in the groove of the diffusion boat so that the main surfaces of the diffusion boat are adjacent to each other, and repeating the steps (a) to (d) for each of the sequential grooves of the diffusion boat. A semiconductor substrate to be set in a diffusion boat. 8. A method for setting a semiconductor substrate for a solar cell in a diffusion boat, comprising: a groove of the diffusion boat placed at a slight angle to a horizontal direction; The first semiconductor substrate coated with the dopant agent is suctioned and transferred by a transfer arm, and the first semiconductor substrate is set in the groove of the diffusion boat by inclining so that the first main surface is slightly downward, (B) a second semiconductor substrate having a first main surface coated with a dopant agent is sucked and transferred by the transfer arm;
By rotating the tip of the arm, the first main surface of the second semiconductor substrate is oriented in a direction opposite to the first main surface of the first semiconductor substrate in the boat, and thereafter, the first semiconductor substrate is tilted. So that the end faces of the first and second semiconductor substrates do not abut each other,
Setting the second semiconductor substrate in the groove of the diffusion boat so that the second main surfaces of the semiconductor substrate are adjacent to each other and overlap with each other; A method of setting a semiconductor substrate for a solar cell in a diffusion boat, wherein the method is repeated. 9. A method of transferring a semiconductor substrate for a solar cell from a diffusion boat, comprising: receiving light of first and second semiconductor substrates set such that their back surfaces are in contact with each other and overlap each other in one groove of the diffusion boat; The first and second semiconductor substrates are simultaneously taken out of the boat by suction with the first transfer arm so as to sandwich the surface, placed on a stage, and the second semiconductor substrate in contact with the stage is suction-fixed. Then, the first semiconductor substrate is sucked and slid by the second transfer arm to be separated from the second semiconductor substrate and sent to the next processing station, and the third transfer arm sucks the second semiconductor substrate. A method of transferring a semiconductor substrate for a solar cell, wherein the light receiving surface and the back surface are inverted and sent to the next processing station. 10. A diffusion boat for heat-treating a semiconductor substrate for a solar cell, comprising: a plurality of grooves each for receiving one semiconductor substrate; and an entire back surface of the semiconductor set in each of the grooves. A shield plate in contact with the solar cell substrate, wherein the shield plate acts to prevent the dopant from being diffused to the back surface while the light receiving surface of the semiconductor substrate is subjected to diffusion processing. Spread boat.