JP2011525296A - Method for forming semiconductor pn junction layer using phosphoric acid aqueous solution and phosphoric acid aqueous solution coating apparatus - Google Patents

Abstract

In the present invention, when a pn junction layer is formed on a P-type surface of a semiconductor silicon substrate, the aqueous solution of phosphoric acid is atomized with a specially devised spray device under conditions of normal temperature and atmospheric pressure to make it uniform on the silicon surface. A method of forming a pn junction layer on a P-type surface of a semiconductor silicon substrate by applying a heat treatment to form a phosphoric acid film with a thickness of 0.2 mm to 0.8 mm and then thermally diffusing. It is about. A phosphoric acid aqueous solution coating apparatus for forming a semiconductor pn junction layer according to the present invention includes a plate 2 for fixing the silicon substrate 1, a transfer device 10 for transporting the plate 2 to the stage 3, and the stage 3. A pair of liquid spraying heads 20 that are positioned in the vertical upper part and arranged to face each other while maintaining a constant angle (θ), and the heads 20 are mounted on the scanning device 4 to reciprocate in a certain section. However, the phosphoric acid aqueous solution is sprayed on the surface of the silicon substrate 1.
[Selection] Figure 1

Description

  In the present invention, when a pn junction layer is formed on a P-type surface such as a semiconductor silicon, a polycrystalline or single crystal silicon substrate for a solar cell, or a flexible substrate outside thereof, a phosphorus device is specially devised. It is a system in which an acid aqueous solution is micronized at room temperature and atmospheric pressure and uniformly applied to the silicon surface, and a phosphoric acid film is formed with a thickness of 0.2 mm to 0.8 mm and then thermally diffused. Not only can the existing high-cost deposition process be replaced and the capital investment cost is low, but also a more precise p by forming a uniform thin film on the surface with fine irregularities and the surface with a hemispherical pattern. The present invention relates to a method for forming a semiconductor pn junction layer using a phosphoric acid aqueous solution so as to form an -n junction layer and a phosphoric acid aqueous solution coating apparatus.

Generally, a diffusion material such as phosphorus oxychloride (POCl ₃ ) containing phosphorus as an impurity or a PSG solution is applied to the surface of a P-type semiconductor substrate of a polycrystalline silicon solar cell that is currently in practical use, and a pn junction. A layer is formed.
Usually, the pn junction layer is formed with a thickness of 0.3 mm, and such an ultrathin pn junction layer is formed through a special method known as a thermal diffusion method. However, according to the thermal diffusion method, in the brazier at 800 ° C. to 1,200 ° C., the step of adding phosphorus oxychloride, PSG solution, etc. containing phosphorus as impurities on the surface of P-type silicon simultaneously with oxygen Since it is always performed, post-treatment such as protection or reduction against chlorine gas and hydrochloric acid generated in this process is essential, and excessive costs are spent on environmental measures and treatment measures. Therefore, recently, a method of using an aqueous phosphoric acid solution that does not require post-treatment as described above as a diffusion material has been studied.

There is no need to treat it in a special atmosphere as in the diffusion process described above, the chemical solution is easy to handle, and a safe water-soluble phosphoric acid solution is used as a coating material to atomize at room temperature and atmospheric pressure. As an alternative, a method in which a phosphoric acid thin film is formed on the semiconductor surface with a thickness of 0.2 mm to 0.8 mm and then thermally diffused with a heating brazier is considered as an alternative.
However, when the phosphoric acid aqueous solution is used as the diffusion material, the following problems occur in the process of applying the phosphoric acid aqueous solution to the silicon substrate. In other words, when applying a phosphoric acid aqueous solution by spin coating or dip coating, which is often used for conventional thin film coating, the phosphoric acid solution splashes on the silicon surface due to the surface tension of water contained in the phosphoric acid aqueous solution, resulting in an ultra-thin film. It was difficult to form a uniform film in the region, and it was not practical. Moreover, even if the phosphoric acid aqueous solution is applied by the conventional spray method, the particle diameter of the phosphoric acid aqueous solution atomized through the spray is usually around 10 mm to 20 mm. Of course, it is difficult to form a uniform film due to the influence of the surface tension of water, as in the case of spin coating or dip coating.

  The present invention has been made in consideration of the above-described problems, and an aqueous phosphoric acid solution capable of forming a 0.3-mm uniform pn junction layer on a silicon substrate using an aqueous phosphoric acid solution. It is an object of the present invention to provide a method for forming a semiconductor pn junction layer using a phosphor and an apparatus for applying a phosphoric acid aqueous solution to a P-type surface of a substrate.

  In order to achieve the above object, a method for forming a semiconductor pn junction layer using a phosphoric acid aqueous solution according to the present invention uses a spray coating apparatus to apply a 1-7% phosphoric acid aqueous solution on the surface of a silicon substrate. It is characterized by forming a thin film of 0.2 mm to 0.8 mm by fine atomization.

  A phosphoric acid aqueous solution coating apparatus for forming a semiconductor pn junction layer according to the present invention includes a substrate adsorption plate for fixing a silicon substrate on an upper portion, a transfer device for transporting the plate to a stage where a coating operation is performed, A pair of liquid spraying heads 20 positioned in the vertical upper part of the stage 3 and arranged so as to face each other while maintaining a constant angle (θ), and the heads are mounted on a scanning device and have a predetermined section. A phosphoric acid aqueous solution coating apparatus for forming a semiconductor pn junction layer in which a phosphoric acid aqueous solution is sprayed on a silicon substrate while reciprocating, wherein the head 20 is a liquid automatic whose inner diameter is smaller than 0.5 mm. A spray nozzle is provided, and the spray atomized portion can be collided at a point separated from the nozzle tip by a certain distance (A) from 10 ° to 45 °. Phosphoric acid aqueous solution sprayed are arranged so as to face each other within a range is characterized in that so as to be uniformly applied to a thickness of 0.2mm~0.8mm the silicon substrate.

In this case, the head preferably collides with the spray atomized portion at a point 10 mm to 20 mm away from the tip of the nozzle, and the concentration of the phosphoric acid aqueous solution is in the range of 1% to 7%. The spray pressure of the aqueous solution is preferably 0.3 MPa, and the surface temperature of the silicon substrate 1 is preferably 60 ° C. to 80 ° C.
In addition, a heater that can further increase the surface temperature of the silicon substrate by heating the plate may be provided below the transfer device.
The silicon substrate is preferably a polycrystalline or single crystal silicon substrate targeted for solar cells.
On the other hand, if necessary, the plate can be rotated.

The present invention has the following effects.
An ultra-thin pn junction layer of 0.3 mm can be uniformly formed on the surface of the silicon substrate.

  The following drawings attached to the present specification illustrate preferred embodiments of the present invention and serve to further understand the technical idea of the present invention together with the detailed description of the invention. Should not be construed as being limited to the matter described in such drawings.

It is the top view and front view of the phosphoric acid aqueous solution coating device by this invention. It is the front view and side view which show the arrangement | positioning state of the head which comprises the phosphoric acid aqueous solution coating device by this invention. It is the phosphoric acid aqueous solution supply system diagram and compressed air circuit diagram of the phosphoric acid aqueous solution spray coating apparatus by this invention. This is an application example in which a silicon substrate is rotated.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, the terms and words used in the present specification and claims should not be construed to be limited to meanings commonly used or meanings used in a dictionary. In order to explain the present invention in the best way, the concept of terms can be appropriately defined and should be interpreted as meaning and concept consistent with the technical idea of the present invention.

FIG. 1 is a plan view and a front view of a phosphoric acid aqueous solution coating apparatus according to the present invention, and FIG. 2 is a front view and a side view showing an arrangement state of heads constituting the phosphoric acid aqueous solution coating apparatus according to the present invention.
As shown in FIGS. 1 and 2, the present invention includes a substrate suction plate 2 for fixing a silicon substrate 1 on the upper side, a transfer device 10 for transporting the plate 2 to a stage 3 on which a coating operation is performed, and the stage 3. And a pair of liquid spraying heads 20 which are arranged so as to face each other while maintaining a constant angle (θ), and the heads 20 are mounted on the scanning device 4 and are fixed. The present invention is applied to a phosphoric acid aqueous solution coating apparatus designed to spray a phosphoric acid aqueous solution on the silicon substrate 1 while reciprocating the section.

  A head bracket 5 for supporting the head 20 at a constant angle (θ) is fixed to the scanning device 4. In the head bracket 5, a slot 5 a for fitting and coupling with the body of the head 20 is formed in a symmetrical arc shape, and a protrusion to be inserted into the slot 5 a is formed in the head 20. The operator can insert the pair of heads 20 on both sides of the slot 5a and connect them, and then adjust the head 20 to an appropriate angle while moving the head 20 along the slot 5a.

  According to the present invention, the head 20 has an atomized pattern of a phosphoric acid aqueous solution sprayed so that the sprayed phosphoric acid aqueous solution can be uniformly applied to the silicon substrate 1 with a thickness of 0.2 mm to 0.8 mm. The liquid automatic spray nozzle 21 has an inner diameter smaller than 0.5 mm so that the width is narrow at around 5 mm and the discharge amount is 5 cc / min or less and fine particles of 10 mm or less can be formed. This is because, if the inner diameter of the nozzle 21 is larger than 0.5 mm, the particle diameter of the sprayed phosphoric acid aqueous solution is too large and the thickness of the coating layer increases, so that the required thickness of the silicon substrate 1 is 0.2 mm to 0. This is because it is difficult to uniformly apply a thin film of 8 mm.

  In addition, according to the present invention, the head 20 includes the nozzle 21 so that the sprayed phosphoric acid aqueous solution can be applied to the silicon substrate 1 with a thickness of 0.2 mm to 0.8 mm through micronization. The spray atomizing portions are arranged so as to face each other within an angle range of 10 ° to 45 ° so that the spray atomizing portions can collide with each other at a certain distance of about 10 mm to 20 mm from the tip of the nozzle.

  If the spray atomization collision distance is less than 10 mm from the tip of the nozzle 21, the collision distance is too short and sufficient atomization has not yet been formed, so the atomization cannot proceed, and if it exceeds 20 mm. Since the collision distance is too far and the collision pressure is small, not only the atomization progresses only slightly, but also the application area becomes narrow, and eventually too much phosphoric acid aqueous solution is applied to the narrow space, and the coating layer Since the thickness increases, it is difficult to obtain a uniform thin film of 0.2 mm to 0.8 mm on the silicon substrate 1.

  Further, if the angle formed by the head 20 is less than 10 °, the coating angle is small and the width of the atomization pattern after the collision is narrowed, so that too much phosphoric acid aqueous solution is jetted into a narrow space and the thickness of the coating layer is increased. Therefore, it is difficult to obtain a uniform thin film of 0.2 mm to 0.8 mm on the silicon substrate 1. If the angle formed by the head 20 exceeds 45 °, the width of the atomized pattern after the collision is large and the application area is widened, so that the phosphoric acid aqueous solution is applied to a space that is too wide and the adhesion efficiency is increased. Will be reduced.

FIG. 3 is a diagram of a phosphoric acid aqueous solution supply system of a phosphoric acid aqueous solution coating apparatus according to a preferred embodiment of the present invention and a corresponding compressed air circuit diagram.
As shown in FIG. 3, each of the pair of heads 20 has a normal pipe 40 for supplying a fixed amount of an aqueous phosphoric acid solution stored in a tank to a pump (P). Further, when the pair of heads 20 do not operate, a reverse pipe 50 for returning the phosphoric acid aqueous solution to the liquid tank is further provided. Further, a first electronic valve 41 and a second electronic valve 51 are provided in the normal pipe 40 and the reverse pipe 50, respectively, and a compressor 70 for supplying compressed air to the reverse pipe 50 is provided in the second electronic valve 51. It is done.

Therefore, when the phosphoric acid aqueous solution is normally supplied, the first electronic valve 41 is opened and the second electronic valve 51 is closed. When the head 20 does not operate, the pump (P) is activated. Simultaneously with the stop, the external air compressed while the second electronic valve 51 is opened is supplied to the pair of heads 20 through the reverse pipe 50. As a result, the phosphoric acid aqueous solution supplied to the head 20 returns to the liquid tank.
On the other hand, the pair of heads 20 is further provided with another compressed air supply pipe 60 and a compressed air supply electronic valve 61 so that the spray spray pressure provided to the head 20 side can be adjusted. The compressed air supply pipe 60 is connected to the compressor 70.

  Thus, if the sprayed phosphoric acid aqueous solution is applied to the silicon substrate 1 with a thickness of 0.2 mm to 0.8 mm, it is dried after one or several application processes depending on the application thickness. A pn junction layer having a thickness of 0.3 mm can be obtained in a state where moisture is removed through the process.

According to the present invention, the concentration of the phosphoric acid aqueous solution is 1% to 7%, and the spraying pressure of the phosphoric acid aqueous solution sprayed from the head 20 is such that a coating layer having a uniform and precise thickness can be obtained. It is desirable that the surface temperature of the silicon substrate 1 is preheated to 60 ° C. to 80 ° C. at 0.3 Mpa.
Here, the reason for preheating the silicon substrate 1 is to increase the concentration of the sprayed phosphoric acid aqueous solution to a level that can be satisfied in a short time. Therefore, a heater 30 that can heat the plate 2 to increase the surface temperature of the silicon substrate 1 may be further provided below the transfer device 10.

If the plate 2 is preheated to an appropriate temperature by the heater 30, the transfer device 10 operates to transfer the plate 2 to the stage 3, and a pair of liquid sprays mounted on the scan device 4 are operated. When reaching the lower center of the head 20, the phosphoric acid aqueous solution is sprayed from the automatic spray nozzle 21. The remaining excess that is not applied to the silicon substrate 1 in the sprayed phosphoric acid aqueous solution is discharged to the outside through the exhaust port 40 below the heater 30 device.
On the other hand, as shown in FIG. 4, the plate 2 is preferably configured to be rotatable so that the aqueous phosphoric acid solution is uniformly applied.

前記表１から分かるように、リン酸水溶液の濃度が１％〜７％であるときに、シリコン基板１の温度を６０℃〜８０℃に予熱した場合、最も精密度が良いｐ−ｎ接合層を得ることができる。 Table 1 shows the results of measuring the precision of the pn junction layer obtained by varying the temperature of the silicon substrate and the concentration of the phosphoric acid aqueous solution. Under these experimental conditions, the spray pressure was 0.3 Mpa, the coating room temperature / relative humidity was 20 ° C., 50%, and the silicon substrate 1 was tested using a polycrystalline silicon substrate. The moving speed of the nozzle 21 was 300 mm / min, and the vertical distance between the nozzle 21 and the silicon substrate 1 was 180 mm. The discharge amount at this time was 11 cc / min / dual spray gun (5.5 cc / min / single spray gun), and the number of coatings was one. The completed pn junction layer was observed using a 200 × optical microscope.

As can be seen from Table 1, when the concentration of the phosphoric acid aqueous solution is 1% to 7%, when the temperature of the silicon substrate 1 is preheated to 60 ° C. to 80 ° C., the highest precision pn junction layer Can be obtained.

前記表２から分かるように、リン酸水溶液の濃度が１％〜７％であるときに、シリコン基板１の温度を６０℃〜８０℃に予熱した場合、噴霧圧力が０．３Ｍｐａであるとき、最も精密度が良いｐ−ｎ接合層を得ることができる。
これは、前述した条件で噴霧圧力が０．３Ｍｐａより小さいかあるいは大きい場合には、霧化粒径が小さすぎるかあるいは大きすぎるようになってしまうので、塗布層の厚さが厚すぎるかあるいは薄すぎるようになって、完成したｐ−ｎ接合層の精密度を低下させるからである。 Table 2 below shows the atomized particle size and p obtained by varying the spray pressure when the concentration of the phosphoric acid aqueous solution is 1% to 7% and the temperature of the silicon substrate 1 is 60 ° C to 80 ° C. -N is the result of measuring the precision of the junction layer together.

As can be seen from Table 2, when the temperature of the silicon substrate 1 is preheated to 60 ° C. to 80 ° C. when the concentration of the phosphoric acid aqueous solution is 1% to 7%, when the spray pressure is 0.3 Mpa, A pn junction layer with the highest precision can be obtained.
This is because when the spray pressure is less than or greater than 0.3 Mpa under the above-described conditions, the atomized particle size is too small or too large, so that the coating layer is too thick or This is because it becomes too thin and the precision of the completed pn junction layer is lowered.

  As described above, the present invention has been described with reference to the limited embodiments and drawings. However, the present invention is not limited thereto, and those skilled in the art to which the present invention belongs have ordinary knowledge. It goes without saying that various modifications and variations can be made within the equivalent scope of the technical idea and claims.

Claims (7)

  A semiconductor using a phosphoric acid aqueous solution characterized in that a thin film of 0.2 mm to 0.8 mm is formed by finely atomizing a 1 to 7% phosphoric acid aqueous solution on the surface of a silicon substrate using a spray coating apparatus. A method of forming a pn junction layer. A plate 2 for fixing the silicon substrate 1 to the top;
A transfer device 10 for transporting the plate 2 to a stage 3 on which a coating operation is performed;
A pair of liquid spraying heads 20 positioned in the vertical upper part of the stage 3 and arranged to face each other while maintaining a constant angle (θ),
A phosphoric acid aqueous solution coating apparatus for forming a semiconductor pn junction layer in which the head 20 is mounted on the scanning device 4 and sprays a phosphoric acid aqueous solution on the surface of the silicon substrate 1 while reciprocating in a predetermined section. Because
The head 20 has an automatic liquid spray nozzle 21 having an inner diameter smaller than 0.5 mm, and the spray atomized portion can collide with the spray atomized portion at a certain distance (A) from the tip of the nozzle 21. A semiconductor p-, characterized in that the phosphoric acid aqueous solutions arranged and sprayed so as to face each other within a range of ° are uniformly applied to the silicon substrate 1 at a thickness of 0.2 mm to 0.8 mm. A phosphoric acid aqueous solution coating apparatus for forming an n-junction layer. In the phosphoric acid aqueous solution coating device for forming the semiconductor pn junction layer according to claim 2,
The said head 20 is a phosphoric acid aqueous solution coating device for forming the semiconductor pn junction layer characterized by making a spray atomization part collide at the point 10 mm-20 mm away from the front-end | tip of the nozzle 21. FIG. In the phosphoric acid aqueous solution coating device for forming the semiconductor pn junction layer according to claim 2,
The application concentration of the phosphoric acid aqueous solution is 1% to 7%, the spraying pressure of the phosphoric acid aqueous solution sprayed from the head 20 is 0.3 Mpa, and the appropriate surface preheating temperature of the silicon substrate 1 is 60 ° C. to 80 ° C. A phosphoric acid aqueous solution coating apparatus for forming a semiconductor pn junction layer. In the phosphoric acid aqueous solution coating device for forming the semiconductor pn junction layer according to claim 2,
Phosphoric acid for forming a semiconductor pn junction layer is provided at the lower part of the transfer device 10 and provided with a heater 30 capable of heating the plate 2 to raise the surface temperature of the silicon substrate 1. Aqueous solution applicator. In the phosphoric acid aqueous solution coating device for forming the semiconductor pn junction layer according to claim 2,
The phosphoric acid aqueous solution coating apparatus for forming a semiconductor pn junction layer, wherein the silicon substrate is one of a polycrystalline or single-crystal silicon substrate for a solar cell. In the phosphoric acid aqueous solution coating device for forming the semiconductor pn junction layer according to claim 2,
The said plate 2 board | substrate rotates, The phosphoric acid aqueous solution coating device for forming the semiconductor pn junction layer characterized by the above-mentioned.

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