JP2009224430A - Method of manufacturing thin film semiconductor substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a thin film semiconductor substrate comprising an epitaxial layer using single crystal silicon or polycrystal silicon, at a low cost with less cracking. <P>SOLUTION: The method of manufacturing a thin film semiconductor substrate includes: a step in which at least either one of hydrogen ion and rare gas ion is implanted in such manner as an ion implantation layer is not formed at least at part in the plane of a semiconductor substrate; a step of forming an epitaxial layer on the surface of such side of the semiconductor substrate as ion is implanted; and a step of separating a thin film, where the epitaxial layer is formed, from the semiconductor substrate. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a thin film semiconductor substrate for a solar battery cell, for example.

  In recent years, the practical application of solar cells has been spreading. In order for this solar cell to be used more seriously, it is particularly important to save resources and reduce costs, such as improving energy conversion (photo-electric conversion) efficiency and shortening the energy recovery period. When considered, a thin film solar cell is preferable to a thick film solar cell. In addition, when a solar cell is formed of a thin film, it can be bent to some extent.For this reason, for example, it can be mounted on a curved surface portion of an automobile body or an external curved surface portion of a portable electrical product, so that power generation can be performed. Will spread.

  In order to popularize such a solar cell, it is necessary to further reduce the cost of the solar cell, particularly to further reduce the energy required for its production. For this purpose, it is necessary to manufacture a solar cell by a simple process.

Conventionally, as such a thin film solar cell, there is an amorphous silicon solar cell formed on a plastic substrate. However, this amorphous silicon solar cell has a problem that the conversion efficiency of photoelectric conversion is low and the conversion efficiency is lowered during use. For this reason, realization of a low-cost and simple manufacturing method of a thin film solar cell using single crystal silicon or polycrystalline silicon having higher conversion efficiency than amorphous silicon has been desired.
However, since the process temperature for forming single crystal silicon or polycrystalline silicon is considerably high, it has been difficult to form it on a plastic substrate or a glass substrate.

  In addition, as a method for producing a thin film used in such a solar cell, Patent Document 1 describes that a thin film is obtained by ion implantation into a silicon wafer and heat treatment thereof to obtain a thin film. Was so thin that it often broke in subsequent steps.

JP 2003-17723 A

  Therefore, the present invention has been made in view of the above problems, and a method of manufacturing a thin film semiconductor substrate capable of manufacturing a thin film semiconductor substrate having an epitaxial layer using single crystal silicon at a low cost with few cracks. The purpose is to provide.

  In order to achieve the above object, the present invention provides a method for manufacturing a thin film semiconductor substrate, wherein at least part of the semiconductor substrate is not formed with an ion implantation layer, and at least hydrogen ions or rare gas ions are formed. Performing a step of ion-implanting one, a step of forming an epitaxial layer on the ion-implanted surface of the semiconductor substrate, and a step of separating the thin film formed with the epitaxial layer from the semiconductor substrate. A thin-film semiconductor substrate manufacturing method is provided.

  In this way, by forming the epitaxial layer on the surface of the semiconductor substrate that has been ion-implanted so as not to form the ion-implanted layer in a part of the surface, the ion-implanted layer is formed by the heat during the formation of the epitaxial layer. The part where the ion implantation layer is formed is thermally peeled, and the epitaxial layer is formed on the thin film connected to the substrate in the part where the ion implantation layer is not formed. A normal thin film is easily broken when it is transported or when an epitaxial layer is formed without reinforcement. However, in the present invention, since the semiconductor substrate and the thin film are connected in one part, the semiconductor substrate serves as a substitute for reinforcement, and the thin film is effective. Can be prevented.

In addition, since most of the thin film is peeled off at the same time as the epitaxial growth due to the heat during the formation of the epitaxial layer, the thin film on which the epitaxial layer is formed and the semiconductor substrate are separated from only one part where the ion implantation layer is not formed. The thin film semiconductor substrate in which the epitaxial layer is easily formed can be manufactured by reducing the number of processes and the number of processes. In addition, since the peeling is performed at the ion implantation layer and only a very thin thin film on the surface layer portion of the semiconductor substrate is separated, the semiconductor substrate from which the thin film has been separated once is used again as the semiconductor substrate to be ion-implanted in the present invention. Therefore, the manufacturing cost can be reduced as compared with the conventional thinning by grinding or the like with a large machining allowance.
Since such an epitaxial layer can be easily formed on the thin film, a thin solar cell made of a single crystal silicon layer can be easily manufactured at low cost. In addition, since the solar cell layer can be formed on the thin film by the epitaxial method, the lifetime reduction phenomenon seen in the solar cell made of the single crystal produced by the Czochralski method does not occur, and it has high performance and high conversion rate. The thin film solar cell can be obtained.

At this time, it is preferable to form two or more epitaxial layers in the step of forming the epitaxial layer.
In the manufacturing method of the present invention, during the epitaxial growth, the thin film is in a state of being connected to a part of the semiconductor substrate. Therefore, it is easy to epitaxially grow a plurality of layers for manufacturing a solar cell without cracking. . Further, by forming two or more epitaxial layers, a thin film semiconductor substrate having a desired thickness and characteristics can be obtained with an extremely thin film.

At this time, the two or more epitaxial layers to be formed can be a solar cell layer obtained by epitaxially growing at least a p-type layer and an n-type layer.
Thus, according to the manufacturing method of the present invention, a thin solar cell having a solar cell layer formed of single crystal silicon by an epitaxial method is subjected to partial peeling and epitaxial layer formation at the same time, and then separated thin films. Since the solar cell layer is already formed on the semiconductor substrate, the steps for manufacturing the solar cell can be reduced, and the semiconductor substrate can be manufactured at low cost.

Further, in the ion implantation step, an ion implantation layer is not formed in a portion where the mask is formed by forming a mask in at least a part of the surface of the semiconductor substrate and then performing ion implantation. (Claim 4).
As described above, by forming a mask in a part of the surface of the semiconductor substrate and performing ion implantation, it is possible to ensure that the portion where the mask is formed is not ion-implanted.

In the ion implantation step, a groove is provided on the surface of the semiconductor substrate on which ions are implanted along the outer periphery of the substrate, and at least a portion having no groove is left as a bridge portion, and an ion implantation layer is formed on the bridge portion. It is preferable to perform ion implantation so as not to form (Claim 5).
Thus, by providing a groove having a bridge portion, an ion implantation layer is formed at a position shallower than the depth of the groove other than the bridge portion, and then forming an epitaxial layer, thereby forming a surface layer portion along the inner periphery of the groove. As a result, the bridge portion that has not been ion-implanted can be kept connected to the semiconductor substrate, and the separation step can be performed simply by cutting the bridge portion in the separation step. For this reason, the crack in the case of a isolation | separation process can be prevented more reliably. Since the thin film semiconductor substrate thus manufactured has a shape of the inner peripheral portion of the formed groove, the thin film semiconductor substrate having a desired shape can be easily manufactured.

Further, in the step of separating, the remaining semiconductor substrate from which the thin film on which the epitaxial layer has been formed has been separated is hydrogenated so as not to form an ion-implanted layer in at least a part of the surface in the step of ion-implanting. Preferably, at least one of ions or rare gas ions is used again as a semiconductor substrate into which ions are implanted.
As described above, in the method for manufacturing a thin film semiconductor substrate according to the present invention, since a thin film having a very thin ion implantation depth is only separated from the prepared semiconductor substrate, the semiconductor substrate after separation is used again. It can be used as a semiconductor substrate into which ions are implanted. As a result, the manufacturing cost of the thin film semiconductor substrate, which has conventionally required a large cutting allowance for thinning by grinding or the like, can be effectively reduced by the manufacturing method of the present invention.

The shape of the semiconductor substrate into which the ions are implanted is preferably rectangular or square.
If it is a manufacturing method of the thin film semiconductor substrate of the present invention, it is not limited to a cylindrical crystal produced by a commonly used Czochralski method, but by forming an epitaxial layer on a rectangular or square semiconductor substrate, A square thin film semiconductor substrate can be manufactured. By producing solar cells using such a rectangular or square thin film semiconductor substrate, gaps can be reduced when they are placed on a panel, and they can be arranged with a high filling rate.

Moreover, the photovoltaic cell manufactured using the thin film semiconductor substrate manufactured by the manufacturing method of the thin film semiconductor substrate of this invention is provided (Claim 8).
Thus, if the thin film semiconductor substrate manufactured by the manufacturing method of this invention is used for manufacture of a photovoltaic cell, a thin photovoltaic cell with a high filling rate can be manufactured at low cost.

  As described above, according to the method for manufacturing a thin film semiconductor substrate of the present invention, since the thin film can be formed and the epitaxial layer can be formed at the same time, the number of steps can be reduced, and the film can be thinned by ion implantation. Therefore, only a very small part of the surface layer portion can be used, and the separated semiconductor substrate can be used as a substrate to be ion-implanted again, so that a thin film semiconductor substrate can be manufactured at low cost. Further, in the manufacture of a thin film semiconductor substrate that is prone to cracking, if the manufacturing method of the present invention is used, the peeled thin film is connected to the semiconductor substrate while the epitaxial layer is formed, and the semiconductor substrate is reinforced. Therefore, cracking is effectively prevented during the epitaxial growth for forming the solar cell layer, and then the thin film on which the epitaxial layer is formed can be easily formed by cutting only a part connected to the semiconductor substrate. Can be separated.

  If the thin film semiconductor substrate manufactured in this way is used for manufacturing a solar cell, a thin solar cell made of a single crystal can be manufactured at a low cost, and its shape and thickness are relatively free, so it is highly efficient. Therefore, it can be arranged at a low cost and at a high filling rate when it is arranged on the panel.

Development of a method for manufacturing a thin film semiconductor substrate having a single crystal silicon layer for solar cells at low cost and easily has been awaited.
The inventor performs ion implantation so as not to form an ion implantation layer in at least a part of the surface of the semiconductor substrate (ion implantation is performed while leaving a part of the surface), and on the surface where the ion implantation is performed. By forming the epitaxial layer on the part, the part where the ion implantation layer is formed by the heat during epitaxial growth is peeled off and the part where it is not formed is connected to the semiconductor substrate, which can effectively prevent cracking of the thin film, and then the semiconductor The inventors have found that a thin film semiconductor substrate on which an epitaxial layer is formed can be easily manufactured by separating a portion connected to the substrate, and the present invention has been completed.

Hereinafter, although the manufacturing method of the thin film semiconductor substrate of this invention is demonstrated in detail, referring to FIG.1, 2,3 as an example of an embodiment, this invention is not limited to this.
FIG. 1 is a flow chart as an example of steps of a method for manufacturing a thin film semiconductor substrate according to the present invention. FIG. 2 is a flowchart showing an example of specific steps of the method for manufacturing a thin film semiconductor substrate of the present invention. FIG. 3 is a perspective view of a semiconductor substrate that can be used in the manufacturing method of the present invention. Further, the semiconductor substrate shown in FIG. 2A is a cross-sectional view taken along the lines AA ′ and BB ′ of the semiconductor substrate shown in FIG.

  In the manufacturing method of the present invention, as shown in FIGS. 1, 2A, and 3, a groove 11 having a bridge portion 12 can be provided along the outer periphery of the semiconductor substrate 10, but this groove is not provided. Even if it does not exist, the manufacturing method of this invention can be implemented. Further, as the groove, it is sufficient if there are one or more bridge portions, but it is also possible to form, for example, four places as shown in FIG. For example, a groove having a depth of about several hundred μm may be provided by cutting with a dicer or the like, or may be provided by a chemical method such as an etching method.

  As the semiconductor substrate prepared at this time, for example, a single crystal silicon wafer can be prepared, and for example, a rectangular or square substrate is preferable. If it is a semiconductor substrate of such a shape, a rectangular or square thin film semiconductor substrate can be easily manufactured, and if a solar cell is produced using the thin film semiconductor substrate, a high filling rate when placed on a panel Can be arranged, and the gap can be reduced.

  Next, as shown in FIGS. 1 and 2B, at least one of hydrogen ions or rare gas ions is ion-implanted without forming the ion-implanted layer 13 in at least a part of the surface of the semiconductor substrate 10. .

At this time, the ion implantation conditions can be set such that, for example, the implantation energy is 20 to 100 keV, the implantation dose is 1 × 10 ¹⁶ to 1 × 10 ¹⁷ / cm ² , and the implantation temperature is 25 to 450 ° C. It can select suitably so that a thin film can be obtained, but it is not restricted to these. In the manufacturing method of the present invention, since the epitaxial layer is formed on the thin film and separated from the substrate, the ion implantation depth may be reduced to make the thickness of the thin film extremely thin. Considering that the semiconductor substrate is used again in the manufacturing method of the present invention, the thinner the thin film can be repeatedly used, the manufacturing cost can be further reduced.

In FIG. 2, the ion implantation layer 13 is not formed on the outer peripheral portion of the groove 11 and the surface of the bridge portion 12, and the ion implantation layer 13 is formed on the other portion in the surface. However, in the case where no groove is provided, it is sufficient that a part of the thin film is connected to the semiconductor substrate even if the ion-implanted layer is peeled off when the epitaxial layer is formed. Alternatively, the ion implantation layer may not be formed on the outer periphery.
At this time, as a method for preventing the ion implantation layer from being partially formed, it is preferable to perform ion implantation by forming a mask in a portion where the ion implantation layer is not formed. As the mask, for example, by forming a protective tape or a protective film, it is possible to reliably prevent the ion implantation layer from being formed on that portion. In addition, any pattern can be used in principle if a mask is used. Therefore, a mask pattern may be selected as appropriate so that it can be easily separated in a subsequent separation step.

  Next, in the manufacturing method of the present invention, as shown in FIGS. 1 and 2C, the epitaxial layer 14 is formed on the surface of the semiconductor substrate 10 on the ion-implanted side. At this time, as shown in FIG. 2C, the portion where the ion-implanted layer 13 is formed is peeled off by heat at the time of forming the epitaxial layer, and only the portion where the ion-implanted layer is not formed is connected to the semiconductor substrate 10. It becomes. For this reason, the semiconductor substrate serves to reinforce the thin film, and an epitaxial layer is formed on the thin film, so that the thin film can be efficiently prevented from cracking, and most of the peeling and epitaxial layer formation can be performed simultaneously. Therefore, the number of processes can be reduced.

  As a method for forming the epitaxial layer at this time, for example, a PVD (Physical Vapor Deposition) method or a CVD (Chemical Vapor Deposition) method using a silane chloride / hydrogen system or the like can be used. For these, an appropriate method may be selected according to the purpose. Since the formed epitaxial layer is partially connected to the substrate, a step of forming a solar cell such as PN junction formation can be performed as it is.

At this time, in the manufacturing method of the present invention, two or more epitaxial layers can be formed. For example, a solar cell layer obtained by epitaxially growing a p-type layer and an n-type layer can be formed.
In the manufacturing method of the present invention, since a thin film can be made very thin, a thin-film semiconductor substrate having a sufficient thickness can be manufactured even if a plurality of epitaxial layers are formed to form a solar cell layer. Plays the role of reinforcing, so that the thin film is prevented from cracking.

As an epitaxial layer to be formed, for example, a p + type Si layer, a p type Si layer, and an n type Si layer are sequentially formed on the surface of the semiconductor substrate on which ions are implanted at a temperature of 1000 to 1200 ° C. After forming the battery layer, a protective film can be formed by forming at least one of a SiO ₂ film and a SiN film on the n-type Si layer by, for example, a CVD method. Thus, by forming the epitaxial layer, a thin film semiconductor substrate having a thickness of, for example, about 10 to 100 μm is obtained together with the thin film.

Next, in the manufacturing method of the present invention, the thin film semiconductor substrate 17 is manufactured by separating the thin film 15 on which the epitaxial layer 14 is formed from the semiconductor substrate 10 as shown in FIGS. Can do.
The separation method is not particularly limited. For example, when the groove 11 is provided in advance as shown in FIGS. 2 and 3, the bridge portion 12 of the groove is provided, and when the groove is not provided, the semiconductor is provided. The portion connected to the substrate can be separated by removing it with a dicer or chemical etching.

  On the other hand, the remaining semiconductor substrate 16 from which the thin film semiconductor substrate 17 has been separated is preferably used again as a semiconductor substrate into which ions are implanted according to the present invention. As described above, according to the manufacturing method of the present invention, only the surface layer portion of the semiconductor substrate is peeled and separated, so that the separated semiconductor substrate can be used again in the manufacturing method of the present invention, and the manufacturing cost is further reduced. can do. In this case, the remaining surface of the semiconductor substrate 16 may be polished and washed and then used repeatedly.

  If the thin-film semiconductor substrate 17 manufactured in this way is used for manufacturing a solar cell, a high-performance, high-conversion thin solar cell using single crystal silicon can be manufactured at low cost. Moreover, if it is the manufacturing method of this invention, since the thin film semiconductor substrate for solar cells can be manufactured in various shapes, such as a rectangle and a square, by an epitaxial method, it is a useless gap when arrange | positioning in the panel of a solar cell. Can be arranged at a high filling rate.

  EXAMPLES Hereinafter, although an Example is shown and this invention is demonstrated more concretely, this invention is not limited to these.

First, a 10 × 10 cm square, p-type single crystal silicon substrate was prepared, and a 100 μm deep groove having four bridge portions as shown in FIG. 2 was provided by a dicer.
Next, a protective tape is applied to the bridge portion of the groove, hydrogen ions are implanted at an implantation energy of 80 keV, an implantation dose of 1 × 10 ¹⁶ / cm ² , an implantation temperature of 350 ° C., and an ion implantation layer is formed outside the bridge portion and the groove. Formed.

Next, an epitaxial layer is formed on the substrate in the order of a p + type Si layer, a p type Si layer, and an n type Si layer at a temperature of 1100 ° C. by an epitaxial growth method. It became the state connected with the single crystal silicon substrate only by the part.
Next, the bridge portion of the single crystal silicon substrate was cut with a dicer to obtain a 50 μm-thick thin film semiconductor substrate on which a solar cell layer was formed.
When a solar cell was produced using the thin film semiconductor substrate thus manufactured, a solar cell with low cost, high efficiency, and high filling rate was obtained.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has substantially the same configuration as the technical idea described in the claims of the present invention, and any device that exhibits the same function and effect is the present invention. It is included in the technical scope of the invention.

It is a flowchart which shows an example of the embodiment of the manufacturing method of this invention. It is a flowchart which shows a specific example of the embodiment of the manufacturing method of this invention. It is a perspective view of the semiconductor substrate which can be used for the manufacturing method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10, 16 ... Semiconductor substrate, 11 ... Groove, 12 ... Bridge part, 13 ... Ion implantation layer,
14 ... an epitaxial layer, 15 ... a thin film, 17 ... a thin film semiconductor substrate.

Claims (8)

  A method of manufacturing a thin film semiconductor substrate, the step of ion implanting at least one of hydrogen ions or rare gas ions without forming an ion implantation layer in at least a part of the surface of the semiconductor substrate; A method for producing a thin film semiconductor substrate, comprising: forming an epitaxial layer on a surface on which ions are implanted; and separating the thin film on which the epitaxial layer is formed from the semiconductor substrate.   2. The method of manufacturing a thin film semiconductor substrate according to claim 1, wherein two or more epitaxial layers are formed in the step of forming the epitaxial layer.   3. The method of manufacturing a thin film semiconductor substrate according to claim 2, wherein the two or more epitaxial layers to be formed are solar cell layers obtained by epitaxially growing at least a p-type layer and an n-type layer.   In the ion implantation step, a mask is formed on at least a part of the surface of the semiconductor substrate, and then ion implantation is performed so that an ion implantation layer is not formed on a portion where the mask is formed. The method for manufacturing a thin film semiconductor substrate according to claim 1, wherein:   In the ion implantation step, a groove is provided on the surface of the semiconductor substrate to be ion-implanted along the outer periphery of the substrate, and at least a portion without the groove is left as a bridge portion, and an ion implantation layer is formed on the bridge portion. 5. The method of manufacturing a thin film semiconductor substrate according to claim 1, wherein the ion implantation is performed so that the ion implantation is not performed.   In the step of separating, the remaining semiconductor substrate from which the thin film on which the epitaxial layer has been formed is separated from the hydrogen ions or the ion implantation layer so as not to form an ion implantation layer in at least part of the surface in the step of ion implantation. 6. The method of manufacturing a thin film semiconductor substrate according to claim 1, wherein at least one of rare gas ions is used again as a semiconductor substrate into which ions are implanted.   The method of manufacturing a thin film semiconductor substrate according to claim 1, wherein a shape of the semiconductor substrate into which the ions are implanted is a rectangle or a square.   A solar cell manufactured using the thin film semiconductor substrate manufactured by the method for manufacturing a thin film semiconductor substrate according to any one of claims 1 to 7.

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