JP6615564B2 - Manufacturing method of semiconductor substrate on which n-type semiconductor layer is formed - Google Patents

Description

  The present invention relates to a method for manufacturing a semiconductor substrate on which an n-type semiconductor layer is formed.

  Conventionally, as a means for forming an n layer on an intrinsic semiconductor substrate or a p-type semiconductor substrate and an n + layer on an n-type semiconductor substrate, a method using phosphorus as an n-type dopant has been proposed. Specifically, a method of performing treatment for several tens of minutes at, for example, 800 to 900 ° C. under a mixed gas atmosphere of phosphorus oxychloride, nitrogen, and oxygen, or phosphorus such as phosphorus pentoxide. A method of forming an n-type diffusion layer with a solution containing an acid salt (see, for example, Patent Document 2) is known.

International Publication No. 2014/024297 JP 2002-75894 A

  However, in the method disclosed in the patent document as described above, a long-time heat treatment is required for forming the n layer, and since it is a batch process, productivity is poor and excessive energy is required. There was a problem. In addition to such production problems, with the techniques disclosed in the above-mentioned patent documents, it is difficult to form a layer having a particularly high phosphorus concentration among n layers, that is, an n + layer. It was difficult to form a layer.

  The present invention has been made in view of the above, and provides a method for manufacturing a semiconductor substrate by which a diffusion layer (so-called n-type semiconductor layer) having a high n-type dopant element concentration can be easily formed on a semiconductor substrate. The purpose is to provide.

  As a result of intensive research to achieve the above object, the present inventor has found that the above object can be achieved by using an aluminum paste containing a specific n-type dopant element in a specific amount. It came to be completed.

That is, the present invention includes, for example, the subject matters described in the following sections.
Item 1.
Applying a first aluminum paste containing aluminum powder on a semiconductor substrate;
Firing the semiconductor substrate coated with the first aluminum paste to form an aluminum layer and an aluminum alloy layer on the semiconductor substrate;
Removing the aluminum layer and the aluminum alloy layer;
With
In the first aluminum paste, an n-type semiconductor layer is formed in which an n-type dopant element is contained in an amount of 1 part by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of aluminum contained in the first aluminum paste. A method for manufacturing a semiconductor substrate.
Item 2. Item 2. The method for manufacturing a semiconductor substrate according to Item 1, wherein the n-type dopant element is one or more elements selected from the group consisting of phosphorus, antimony, arsenic, and bismuth.
Item 3. The said baking is a manufacturing method of the semiconductor substrate of Claim 1 or 2 performed in 570 degreeC or more and 1200 degrees C or less.
Item 4. Before baking, further comprising a step of applying a second aluminum paste containing aluminum powder to a region different from the region where the first aluminum paste is applied on the semiconductor substrate;
The said 2nd aluminum paste contains the said n-type dopant element in any one of said claim | item 1-3 which contains less than 1 mass part with respect to 100 mass parts of aluminum contained in the said 2nd aluminum paste. Semiconductor substrate manufacturing method.

  According to the method for manufacturing a semiconductor substrate having an n-type semiconductor layer according to the present invention, a diffusion layer having a high concentration of an n-type dopant element, a so-called n-type semiconductor layer, is formed on the semiconductor substrate in a simple process, and Can be formed in a short time.

It is explanatory drawing which shows an example of the manufacturing method of this invention, and is a schematic diagram which shows an example of the process which forms a diffused layer on a semiconductor substrate. It is explanatory drawing which shows the other example of the manufacturing method of this invention, and is a schematic diagram which shows the process of forming a diffused layer on a semiconductor substrate. It is explanatory drawing which shows the other example of the manufacturing method of this invention, and is a schematic diagram which shows the process of forming a diffused layer on a semiconductor substrate. It is explanatory drawing which shows the other example of the manufacturing method of this invention, and is a schematic diagram which shows the process of forming a diffused layer on a semiconductor substrate. It is a graph which shows a Suns-Voc measurement result (IV curve). It is a graph which shows the result of having performed the element distribution analysis of the surface layer by the secondary ion mass spectrometry (SIMS) about the substrate sample obtained by the comparative example 1, Example 2, and Example 5. FIG.

  Hereinafter, embodiments of the present invention will be described in detail.

  In the method of manufacturing a semiconductor substrate on which an n-type semiconductor layer according to the present embodiment is formed, a step of applying a first aluminum paste containing aluminum powder on a semiconductor substrate and the first aluminum paste are applied A step of firing a semiconductor substrate to form an aluminum layer and an aluminum alloy layer on the semiconductor substrate; and a step of removing the aluminum layer and the aluminum alloy layer. The first aluminum paste contains an n-type dopant element in an amount of 1 part by mass to 1000 parts by mass with respect to 100 parts by mass of aluminum contained in the first aluminum paste.

  According to the above manufacturing method, a diffusion layer having a high concentration of the n-type dopant element, a so-called n-type semiconductor layer, can be formed on the semiconductor substrate in a simple process and in a short time.

  The type of the semiconductor substrate is not particularly limited, and examples thereof include a single crystal silicon substrate, a crystalline silicon (Si) substrate such as a polycrystalline silicon substrate, and a germanium substrate. The semiconductor substrate may be formed of silicon having a purity of 99% or more or germanium having a purity of 99% or more. Alternatively, the semiconductor substrate may be formed by mixing silicon and germanium in an arbitrary ratio. Note that the semiconductor substrate may contain an element other than silicon or germanium as an impurity or an additive.

  The semiconductor substrate as described above can be formed into a desired shape by being sliced from an ingot, for example. The thickness of the semiconductor substrate is not particularly limited, and can be formed to a desired thickness according to the intended use. For example, the thickness of the semiconductor substrate can be 150 μm or more and 550 μm or less, and particularly preferably 150 μm or more and 250 μm or less when applied to a solar cell.

  The semiconductor substrate may be formed of a p-type semiconductor, an n-type semiconductor, or an intrinsic semiconductor. For example, if the purpose is to form an n + layer on a semiconductor substrate, if a p-type silicon substrate is used as the semiconductor substrate, whether or not the diffusion layer formed on the silicon substrate is formed as an n + layer. There is an advantage that it is easy to judge.

  The first aluminum paste used in the present embodiment contains aluminum powder and an n-type dopant element as essential components, and is a material that can be applied to a semiconductor substrate to form a coating film. is there.

  More specifically, the first aluminum paste can contain aluminum powder, a compound containing an n-type dopant element, a resin, and a solvent. That is, the n-type dopant element is included in the first aluminum paste as a compound containing the n-type dopant element.

  Aluminum powder is the main component of the first aluminum paste. For example, if the first aluminum paste is used as a raw material for producing a crystalline silicon solar cell, the aluminum powder becomes a raw material for forming an electrode. obtain. In addition, if a first aluminum paste containing aluminum powder is applied onto a silicon semiconductor substrate and baked to form a coating, an Al—Si alloy layer and a diffusion layer are formed on the surface of the silicon semiconductor substrate. The powder can be a raw material for forming the alloy layer and the diffusion layer.

  The aluminum powder is mainly composed of an aluminum element. The purity of aluminum in the aluminum powder is not limited, and is preferably 99.7% or more, and more preferably 99.9% or more, for example. The aluminum powder may contain impurities other than aluminum, for example, other metal elements inevitably included. The aluminum powder may contain an alloy of aluminum and another metal element, an oxide of aluminum, or the like.

  Examples of the shape of the aluminum powder include a spherical shape and an elliptical spherical shape, but are not limited thereto. From the viewpoint of good printability and good reaction with the semiconductor substrate, the shape of the aluminum powder is preferably spherical.

The average particle diameter (D ₅₀ ) of the aluminum powder is not particularly limited, but if the average particle diameter is 1 μm or more and 20 μm or less, the printability of the paste composition is improved and the reactivity with the semiconductor substrate is also improved. This is preferable. A more preferable average particle diameter of the aluminum powder is 2 to 4 μm.

  A compound containing an n-type dopant element is a raw material for forming a diffusion layer such as an n layer or an n + layer on a semiconductor substrate. Hereinafter, the compound containing the n-type dopant element may be simply abbreviated as “n-type dopant compound”.

  Specifically, the n-type dopant element is one or more elements selected from the group consisting of phosphorus (P), antimony (Sb), arsenic (As), and bismuth (Bi). preferable. In this case, a diffusion layer having a high n-type dopant element concentration, that is, an n-type semiconductor layer can be formed on the semiconductor substrate in a simple process in a short time, and the semiconductor substrate is made of group 4 silicon. It is especially effective in cases.

  Here, the diffusion layer refers to a layer formed including an element constituting a semiconductor substrate and an n-type dopant element, and may also be referred to as an impurity layer. The diffusion layer may contain aluminum to such an extent that it does not become a p layer or a p + layer. Such a diffusion layer can be an n-type layer (n layer) or a p-type layer (p layer) depending on the type and amount of impurities contained in the layer. For example, the n layer is formed when the atomic concentration of the n-type dopant element (such as phosphorus) that is an n-type dopant is higher than the atomic concentration of aluminum that is a p-type dopant. The n layer when the concentration of the n-type dopant element is particularly high is referred to as an n + layer.

  The n-type dopant compound may be either an inorganic compound or an organic compound. Moreover, the compound containing an n-type dopant element may be comprised with 2 or more types of compounds, and may further contain both the inorganic compound and the organic compound.

Examples of n-type dopant compounds include, but are not limited to, oxides and organic compounds of the above elements. More specific n-type dopant compounds include P ₂ O ₅ , aluminum phosphate, calcium phosphate, potassium phosphate, phosphate ester and the like. The kind of phosphate ester is not specifically limited, For example, although a well-known phosphate ester is mentioned, It is preferable that polyoxyethylene oleyl ether phosphate is included especially. Moreover, as an n-type dopant compound, the glass containing the oxide of the said n-type dopant element, what is called a glass frit may be contained.

  The content of the n-type dopant element in the n-type dopant compound is 1 part by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of aluminum contained in the aluminum powder. In this case, the atomic concentration of the n-type dopant element (phosphorus or the like) in the diffusion layer is likely to increase, and an n layer or an n + layer, that is, an n-type semiconductor layer can be easily formed. Moreover, since the upper limit of the content of the n-type dopant element in the n-type dopant compound is 1000 parts by mass, the proportion of aluminum in the aluminum paste is unlikely to decrease, thereby preventing deterioration of reactivity with the semiconductor substrate. The diffusion layer can be formed efficiently.

  The content of the n-type dopant element in the n-type dopant compound is more preferably 1.5 parts by mass or more with respect to 100 parts by mass of aluminum contained in the aluminum powder, and is 2 parts by mass or more. Is particularly preferred. Further, the content of the n-type dopant element in the n-type dopant compound is more preferably 10 parts by mass or less, and more preferably 5 parts by mass or less with respect to 100 parts by mass of aluminum contained in the aluminum powder. Is particularly preferred.

  If the first aluminum paste containing the n-type dopant compound is used, a diffusion layer (n-type semiconductor layer) such as an n + layer can be formed on the semiconductor substrate. When such a semiconductor substrate on which an n + layer is formed is applied to a substrate such as a solar cell module, there is an advantage that the power generation efficiency of the solar cell can be increased. Further, when the content of the n-type dopant element is in the above range, there is an advantage that the diffusion layer can be formed on the semiconductor substrate in a short time.

  Examples of the solvent include diethylene glycol monobutyl ether, terpineol, diethylene glycol monobutyl ether acetate, and dipropylene glycol monomethyl ether. However, the solvent is not limited to these, and other known organic solvents can be used.

  The resin is a material that serves as a binder in the paste composition. Examples of resins include celluloses such as ethyl cellulose and nitrocellulose, polyvinyl butyral, phenol resin, melanin resin, urea resin, xylene resin, alkyd resin, unsaturated polyester resin, acrylic resin, polyimide resin, furan resin, urethane resin, polyethylene , Polypropylene, polystyrene, ABS resin, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyimide, polyethersulfone , Polyarylate, polyetheretherketone, polytetrafluoroethylene, silicone resin, thermosetting resin (isocyanate DOO compound, cyanate compound, etc.) is exemplified, but not limited thereto. The first aluminum paste may contain only one kind of resin, or may contain two or more kinds of resins.

  The resin content is 0.2% by mass or more and 3.0% by mass or less with respect to the paste composition, and the solvent content is 1.0% by mass or more and 25% by mass or less with respect to the paste composition. It can be a range.

  The first aluminum paste may further contain glass powder in addition to the n-type dopant compound. This glass powder has an action of assisting the reaction between the aluminum powder and the semiconductor substrate and the sintering of the aluminum powder itself. Examples of such glass powder include glass powder containing one or more elements other than the n-type dopant element. The average particle diameter of the glass particles constituting the glass powder is preferably 1 μm or more and 3 μm or less. Although content of the glass powder contained in a 1st aluminum paste is not specifically limited, It is preferable that they are 0.1 mass part or more and 15 mass parts or less with respect to 100 mass parts of aluminum powder. In this case, the film formed by applying the paste composition to the semiconductor substrate and sintering it is excellent in adhesion to the semiconductor substrate, and further, the electrical resistance is hardly increased.

  The first aluminum paste may contain other various types of additives as long as the effects of the present invention are not hindered. Examples of the various additives include antioxidants, corrosion inhibitors, antifoaming agents, thickeners, coupling agents, electrostatic imparting agents, polymerization inhibitors, thixotropic agents, and antisettling agents.

  The first aluminum paste can be prepared by any method, and the method is not particularly limited. For example, by preparing aluminum powder, a compound containing an n-type dopant element, a resin, a solvent, and the glass powder added as necessary, and other additives in predetermined amounts, and mixing them. The paste composition of this embodiment can be prepared.

  The resin and the solvent may be mixed in advance to prepare a so-called organic vehicle, and the first aluminum paste may be prepared using this organic vehicle. The organic vehicle may contain the glass powder and additives. However, the organic vehicle does not necessarily contain a solvent, and the resin itself may be used as the organic vehicle without being dissolved in the solvent. Although content of the organic vehicle contained in a 1st aluminum paste is not specifically limited, It can be 30 mass parts or more and 100 mass parts or less with respect to 100 mass parts of aluminum powder. In this case, it is easy to prevent a decrease in printability of the first aluminum paste.

  In preparing the first aluminum paste, a known mixer or disperser can be used.

  FIG. 1 schematically shows a method of forming a film on a semiconductor substrate using the first aluminum paste. In FIG. 1, a p-type silicon substrate (may be abbreviated as p-Si) is used as the semiconductor substrate 1 (FIG. 1A), and a phosphorus element (P) is used as the n-type dopant element. Is used.

  FIGS. 1A and 1B schematically show a step of applying a first aluminum paste containing aluminum powder on a semiconductor substrate.

The method for applying the first aluminum paste to the surface of the semiconductor substrate is not particularly limited. For example, screen printing, spin coating, or the like can be used, but the method is not limited to these, and other methods are used. It may be adopted. The amount of the first aluminum paste applied to the semiconductor substrate can be, for example, 4 mg / cm ² or more and 12 mg / cm ² or less.

  After the application, the volatile matter in the first aluminum paste is removed by drying. The temperature of the drying treatment can be performed, for example, at 100 ° C. or higher and 300 ° C. or lower. Although the time of a drying process changes with kinds of paste composition, if it is 1 minute or more and 10 minutes or less, for example, it can fully dry.

  By passing through the said process, as shown in FIG.1 (b), the coating film 2 formed by drying the 1st aluminum paste on the semiconductor substrate p-Si is formed.

  FIGS. 1B and 1C schematically show a process of baking the semiconductor substrate coated with the first aluminum paste to form an aluminum layer and an aluminum alloy layer on the semiconductor substrate.

  By performing the firing, an aluminum layer 3a and an alloy layer 3b containing aluminum are formed as shown in FIG. In the embodiment of FIG. 1, the alloy layer 3b containing aluminum is an alloy layer of aluminum and silicon (Al—Si alloy layer). The aluminum layer 3a is a layer formed of an aluminum sintered body (Al sintered layer).

  Further, by performing a cooling process after firing, a part of aluminum and the n-type dopant element (P) diffuses into the silicon substrate, and this is formed as an impurity layer, that is, a diffusion layer 3c. In the formed diffusion layer 3c, the n-type dopant element (P) has a higher concentration than silicon. As a result, the diffusion layer 3c is formed as an n + layer, a so-called n-type semiconductor layer, and an n-type silicon substrate as shown in FIG. 1C is formed. Specifically, as shown in FIG. 1C, a diffusion layer 3c, an alloy layer 3b containing aluminum (alloy layer of aluminum and silicon), and an aluminum layer 3a are formed on the semiconductor substrate 1 (p-Si). It is formed by stacking in this order from the semiconductor substrate 1 side.

  Firing can be performed, for example, in the range of 570 ° C. or more and 1200 ° C. or less. With the firing temperature in this range, the aluminum layer 3a, the alloy layer 3b containing aluminum, and the diffusion layer 3c are efficiently formed in a short time. be able to. The firing temperature is more preferably 600 ° C. or more and 1000 ° C. or less, further preferably 800 ° C. or more and 950 ° C. or less, and particularly preferably 850 ° C. or more and 950 ° C. or less.

  The firing time can be set to, for example, 3 seconds or more and 300 seconds or less, and within this range, a desired film can be formed, and the entire process does not become too long. A diffusion layer can be formed on the substrate. The firing time is particularly preferably 3 seconds or more and 60 seconds or less.

  The firing may be performed in either an air atmosphere or a nitrogen atmosphere.

  In the cooling treatment after firing, the cooling rate and the atmospheric temperature during cooling are not limited, and cooling can be performed under appropriate conditions. For example, natural cooling can be performed in an atmosphere of room temperature, for example, 25 ° C.

  1C and 1D schematically show a process for removing the aluminum layer 3a and the aluminum alloy layer 3b.

  In this step, the aluminum layer 3a and the alloy layer 3b containing aluminum formed on the semiconductor substrate 1 (p-Si) are removed by etching, for example. Thereby, as shown in FIG.3 (d), the semiconductor substrate 1 provided with the diffusion layer 3c on the surface is formed. The conditions for the etching treatment are not particularly limited, and for example, known etching treatment conditions can be employed in this step. For example, etching can be performed using an etchant containing KCl, HCl, or the like.

  In the manufacturing method as shown in FIG. 1, the diffusion layer can be easily formed on the semiconductor substrate. In particular, the conventional method for forming a diffusion layer such as the “impurity thermal diffusion method” requires a long-time heat treatment, and is also a batch process, so that productivity is poor and excessive energy is required. However, if the first aluminum paste is used, a diffusion layer (n-type semiconductor layer) formed containing an n-type dopant element can be easily formed in a short time. .

  In general, when a diffusion layer is formed by heat treatment, even when heating at about 800 ° C., the solid phase silicon remains in the solid phase, and the thermal diffusion rate of the n-type dopant element into the solid phase silicon depends on the type and temperature of the element. Although it depends, it is about 1 μm / hour. On the other hand, when the paste composition is used, for example, solid phase silicon and aluminum react once at about 600 ° C. to form a liquid phase silicon aluminum alloy, and the n-type dopant element immediately enters the liquid phase silicon aluminum alloy. It can diffuse (for example, diffuse to 5 μm by heating at 800 ° C. for about 10 seconds). In the subsequent cooling process, the silicon is recrystallized and becomes a solid, but a diffusion layer is formed by a part of the n-type dopant element remaining in the silicon. Therefore, when the paste composition is used, the formation process of the diffusion layer is different from the conventional method, and silicon is once converted into a liquid phase, so that diffusion in a short time is possible.

  Further, the first aluminum paste contains an n-type dopant element in an amount of 1 to 1000 parts by mass with respect to 100 parts by mass of aluminum contained in the first aluminum paste. A layer having a high concentration (for example, phosphorus), a so-called n + layer, can be formed by a simpler method. Therefore, the semiconductor substrate having such a formed diffusion layer can be applied to a crystalline silicon solar cell, thereby further improving the power generation efficiency of the crystalline silicon solar cell. In addition, the semiconductor substrate having the diffusion layer as described above can be applied to various fields. For example, the semiconductor substrate can also be applied to a semiconductor diode and a semiconductor transistor that require formation of a pn junction.

  In the manufacturing method of this embodiment, in addition to the manufacturing method as described above, as another example, before the firing, the semiconductor substrate is placed in a region different from the region where the first aluminum paste is applied. A step of applying a second aluminum paste containing aluminum powder can be further provided. In this case, the second aluminum paste may contain less than 1 part by mass of the n-type dopant element with respect to 100 parts by mass of aluminum contained in the second aluminum paste.

  FIG. 2 shows another example of a method for forming an n-type diffusion layer using the paste composition of the present embodiment. As shown in the figure, in the manufacturing method of the present embodiment, before the firing, aluminum powder is contained in a region different from the region where the first aluminum paste is applied on the semiconductor substrate. And a step of applying a second aluminum paste. Specifically, a step of applying a second aluminum paste containing aluminum powder onto the semiconductor substrate on the surface opposite to the surface on which the first aluminum paste is applied before the firing is further performed. Prepare. In the second aluminum paste, the content of the n-type dopant element may be less than 1 part by mass with respect to 100 parts by mass of aluminum contained in the second aluminum paste.

  First, as shown in FIG. 2A, a semiconductor substrate 1 (p-Si) is prepared, and a first aluminum paste is applied onto the semiconductor substrate 1 and dried to apply as shown in FIG. 2B. Forming the film 2 is the same as in the embodiment of FIG.

  In the embodiment of FIG. 2, as shown in FIG. 2C, a second aluminum paste is further applied to the surface opposite to the surface on which the coating film 2 of the semiconductor substrate 1 is formed and dried. The aluminum coating film 4 is formed. The conditions for forming the aluminum coating film 4 can be performed, for example, under the same conditions as the method for forming the coating film 2 from the first aluminum paste, but are not limited thereto.

  The second aluminum paste is a paste different from the first aluminum paste. The second aluminum paste usually does not contain the n-type dopant compound, or the content of the n-type dopant element is 1 part by mass with respect to 100 parts by mass of aluminum contained in the second aluminum paste. Less than n-type dopant elements may be included. The other components of the second aluminum paste can be the same as those of the second aluminum paste.

  As shown in FIG. 2C, after the coating film 2 is formed on one surface of the semiconductor substrate 1 and the aluminum coating film 4 is formed on the other surface, the semiconductor substrate 1 on which these coating films are formed is baked. Cool down. 2D, the diffusion layer 3c, the alloy layer 3b containing aluminum, and the aluminum layer 3a are laminated in this order from the semiconductor substrate 1 side on the surface of the semiconductor substrate 1 on the coating film 2 side. It is formed in the same manner as the embodiment of FIG. On the other hand, a diffusion layer 5c, an alloy layer 5b containing aluminum, and an aluminum layer 5a are formed on the surface of the semiconductor substrate 1 on the aluminum coating film 4 side in this order from the semiconductor substrate 1 side. The firing and cooling treatment can be performed under the same conditions as in the embodiment of FIG.

  The diffusion layer 5 c is a layer formed by diffusing aluminum in the semiconductor substrate 1. The diffusion layer 5c does not contain an n-type dopant element like the diffusion layer 3c, or even if it is contained, its content is so small that no n-layer or n + layer is formed. It is different from the layer 3c.

  If the semiconductor substrate 1 is a silicon substrate, the alloy layer 5b containing aluminum is formed as an alloy layer of aluminum and silicon.

  Thereafter, by removing the aluminum layers (3a, 5a) and the aluminum alloy layers (3b, 5b), the semiconductor substrate 1 having diffusion layers (diffusion layers 3c and 5c) formed on both sides can be obtained. (FIG. 2 (e)). The etching conditions can be the same as those in the embodiment of FIG. In the etching process in step 3, only one of the surfaces may be etched.

  The diffusion layer 3c formed as described above can be an n-type semiconductor layer such as an n + layer, as in the embodiment of FIG. On the other hand, the diffusion layer 5c does not contain an n-type dopant element, or even if it is contained, its content is so small that an n-layer or an n + layer is not formed. This is a so-called p-type semiconductor layer.

  If the diffusion layer is formed as shown in FIG. 2 through the above steps, the n-type semiconductor layer and the p-type semiconductor layer can be simultaneously formed on one semiconductor substrate by one baking step. For example, a semiconductor substrate in which an n-type semiconductor layer is formed on one surface and a p-type semiconductor layer is formed on the back surface thereof is effective for applications such as solar cells and semiconductor diode elements.

  In FIG. 3, the further modification of the manufacturing method which concerns on embodiment of FIG. 1 is shown typically.

  In the embodiment of FIG. 3, the first aluminum paste and the second aluminum paste are applied to the same surface of the semiconductor substrate 1. Also in this embodiment, before firing, a step of applying a second aluminum paste containing aluminum powder to a region different from the region where the first aluminum paste is applied on the semiconductor substrate. Further prepare.

  Specifically, in this embodiment, the first aluminum paste and the second aluminum paste are partially applied to the same side surface of the semiconductor substrate 1 on the semiconductor substrate 1. In particular, the first aluminum paste and the second aluminum paste are applied so that the coating films formed from the respective pastes have a predetermined interval. The application method can be performed in the same manner as described above.

  As shown in FIG. 3A, in the present embodiment, for example, the coating film 2 formed of the first aluminum paste and the aluminum coating film 4 formed of the second aluminum paste are spaced apart from each other by a predetermined distance. Each of them can be formed over the entire length in one direction of the semiconductor substrate 1.

  The semiconductor substrate on which the respective coating films are thus formed is baked and cooled in the same procedure as in the embodiment of FIGS. As a result, as shown in FIG. 3B, the coating film 2 formed of the first aluminum paste has the diffusion layer 3c, the alloy layer 3b containing aluminum, and the aluminum layer 3a laminated in this order from the semiconductor substrate 1 side. To form a laminate. On the other hand, the aluminum coating film 4 formed by the second aluminum paste is a laminate formed by laminating the diffusion layer 5c, the alloy layer 5b containing aluminum, and the aluminum layer 5a in this order from the semiconductor substrate 1 side. In this case, as in FIGS. 1 and 2, the diffusion layer 3c is an n-type semiconductor layer and the diffusion layer 5c is a p-type semiconductor layer.

  Next, as shown in FIG. 3C, the diffusion layer 3c and the diffusion layer 5c are removed by a process of removing the aluminum layers (3a, 5a) and the aluminum alloy layers (3b, 5b) in the same manner as in FIGS. The semiconductor substrate 1 formed with a predetermined interval can be obtained.

  Since the semiconductor substrate 1 as shown in FIG. 3C has a structure in which an n-type semiconductor layer as the diffusion layer 3c and a p-type semiconductor layer as the diffusion layer 5c are formed at a predetermined interval. It can be applied as a back contact type solar cell in which no electrode is required on the light receiving surface.

  As described above, if the first aluminum paste and the second aluminum paste are partially applied to the same surface of the semiconductor substrate 1 so as to be spaced apart from each other by the semiconductor substrate 1, no electrode is required on the light receiving surface. The back contact type solar cell member can be manufactured by a simple method.

  FIG. 4 also schematically shows a modification of the manufacturing method according to the embodiment of FIG. Also in this embodiment, before firing, a step of applying a second aluminum paste containing aluminum powder to a region different from the region where the first aluminum paste is applied on the semiconductor substrate. Further prepare. In the embodiment of FIG. 4, the first aluminum paste is partially applied to one side surface of the semiconductor substrate 1, and the coating films formed from the first aluminum paste are spaced at a predetermined interval. To have. The application method can be performed in the same manner as described above.

  Specifically, as shown in FIG. 4A, first, the first aluminum paste is applied to the vicinity of opposite side edges of the semiconductor substrate 1 to form the coating film 2.

  Next, the semiconductor substrate on which the respective coating films are formed in this way is fired and cooled in the same procedure as in the embodiment of FIG. As a result, as shown in FIG. 4B, the coating film 2 formed of the first aluminum paste has the diffusion layer 3c, the alloy layer 3b containing aluminum, and the aluminum layer 3a laminated in this order from the semiconductor substrate 1 side. To form a laminate. As in the case of FIG. 1, the diffusion layer 3c is an n-type semiconductor layer.

  Next, the semiconductor substrate in which the diffusion layers 3c are formed at both end portions of the semiconductor substrate 1 as shown in FIG. 4C by the process of removing the aluminum layer 3a and the aluminum alloy layer 3b by the same method as FIG. 1 can be obtained.

  Since the diffusion layer 3c is formed at both end portions of the semiconductor substrate 1, such a semiconductor substrate 1 can have a transistor structure, and can be applied to a transistor element or an integrated circuit (IC) element. .

  EXAMPLES Hereinafter, although an Example demonstrates this invention more concretely, this invention is not limited to the aspect of these Examples.

Example 1
Glass containing P ₂ O ₅ and P ₂ O ₅ as a compound containing 40 parts by mass of an organic vehicle as a binder and an n-type dopant element with respect to 100 parts by mass of spherical aluminum powder (P ₂ O ₅ —SnO-based glass) 20 parts by weight of a frit mixture was mixed. Thus, a first aluminum paste containing phosphorus as an n-type dopant element was prepared. The organic vehicle was a mixture of 1 part by mass of ethyl cellulose (manufactured by Dow) and 39 parts by mass of a glycol ether organic solvent.

  In the paste composition, the amount of phosphorus with respect to 100 parts by mass of aluminum was 1.52 parts by mass.

On the other hand, 100 parts by mass of spherical aluminum powder was mixed with 40 parts by mass of the organic vehicle as a binder and 2 parts by mass of B ₂ O ₃ glass frit, which is glass containing no phosphorus. As a result, a second aluminum paste containing a non-n-type dopant element was prepared.

  Next, the above-described first aluminum paste was applied to one surface of a p-type silicon substrate sliced to a thickness of 200 μm and dried at 100 ° C. to 300 ° C. On the other hand, on the opposite surface of the p-type silicon substrate, the second aluminum paste containing the above-mentioned non-n-type dopant element is applied to the surface opposite to the surface on which the first aluminum paste is applied. A heat treatment for 60 seconds including heating and cooling was performed at a firing peak of 900 ° C. Further, a substrate sample was obtained by removing the aluminum layer and the aluminum alloy layer on both surfaces of the p-type silicon substrate produced by firing with hydrochloric acid.

(Example 2)
In the same manner as in Example 1 except that the paste composition was prepared by changing to 28 parts by mass of a mixture of glass containing P ₂ O ₅ and P ₂ O ₅ (P ₂ O ₅ —SnO glass frit). A substrate sample was obtained. In the paste composition, the amount of phosphorus with respect to 100 parts by mass of aluminum was 2.21 parts by mass.

(Example 3)
A mixture of glass containing P ₂ O ₅ and P ₂ O ₅ (P ₂ O ₅ —SnO glass frit) is changed to polyoxyethylene oleyl ether phosphoric acid, which is an organic phosphorus compound, and 100 parts by mass of aluminum powder. A substrate sample was obtained in the same manner as in Example 1 except that the paste composition was prepared by changing the organophosphorus compound to 20 parts by mass. In the paste composition, the amount of phosphorus with respect to 100 parts by mass of aluminum was 1.58 parts by mass.

Example 4
A mixture of glass containing P ₂ O ₅ and P ₂ O ₅ (P ₂ O ₅ —SnO glass frit) is changed to polyoxyethylene oleyl ether phosphoric acid, which is an organic phosphorus compound, and 100 parts by mass of aluminum powder. A substrate sample was obtained in the same manner as in Example 1 except that the paste composition was prepared by changing the organophosphorus compound to 40 parts by mass. In the paste composition, the amount of phosphorus with respect to 100 parts by mass of aluminum was 3.16 parts by mass.

(Example 5)
A mixture of glass containing P ₂ O ₅ and P ₂ O ₅ (P ₂ O ₅ —SnO glass frit) is changed to a mixture of an inorganic phosphorus compound and an organic phosphorus compound, and the mixture is added to 100 parts by mass of aluminum powder. A substrate sample was obtained in the same manner as in Example 1 except that the paste composition was prepared by changing to 15 parts by mass. The inorganic phosphorus compound was a mixture of P and P 2 O 5 and aluminum phosphate, and the organic phosphorus compound was polyoxyethylene oleyl ether phosphoric acid. In the paste composition, the amount of phosphorus with respect to 100 parts by mass of aluminum was 2.77 parts by mass.

(Comparative Example 1)
A non-phosphorus-containing aluminum paste was prepared by mixing 40 parts by mass of an organic vehicle as a binder and ₂ parts by mass of phosphorus-free glass (B ₂ O ₃ -based glass frit) with 100 parts by mass of spherical aluminum powder.

  Next, a non-phosphorus-containing aluminum paste was applied to both sides of the p-type silicon substrate sliced to a thickness of 200 μm, and heat treatment was performed for 60 seconds including heating and cooling at a firing peak of 900 ° C. in a continuous furnace. Furthermore, a substrate sample was obtained by removing the aluminum layers on both surfaces of the p-type silicon substrate produced by firing with hydrochloric acid.

(Diffusion layer check)
Each of the substrate samples obtained in the above Examples and Comparative Examples was subjected to n layer formation determination using a SunsVoc measuring apparatus (manufactured by Sinton Instruments, model number Suns-Voc). Specifically, by irradiating the substrate sample with flash light (light that decays with time), the electrons in the semiconductor are excited, and the light intensity of the flash light that decays and the voltage change due to electron excitation are measured as needed. Thus, n layer formation was determined. Table 1 shows the results.

From Table 1, it can be seen that n layers are formed for all the substrate samples of Examples 2 to 5. That is, the paste composition in which the content of the n-type dopant element in the compound containing the n-type dopant element is 1 part by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of aluminum contained in the aluminum powder. Thus, it can be seen that an n layer is formed on the semiconductor substrate. It was also confirmed that an n-type layer was formed regardless of the type of phosphorus compound.

  On the other hand, in Comparative Example 1 in which the content of the n-type dopant element is out of the above range, formation of the n layer was not confirmed.

(Measurement of solar cell characteristics)
The substrate sample obtained in Example 1 was measured for solar cell characteristics using a SunsVoc measuring device (manufactured by Sinton Instruments, model number Suns-Voc).

  FIG. 5 shows the Suns-Voc measurement result (IV curve). From this result, it has confirmed that the board | substrate sample obtained in Example 1 has the characteristic as a solar cell. This result suggests that an n-type Si layer is formed by the manufacturing method of Example 1, and a pn junction is formed on the semiconductor substrate.

  6A to 6C, the substrate samples obtained in Comparative Example 1, Example 2 and Example 5 were subjected to element distribution analysis of the surface layer by SIMS (secondary ion mass spectrometry), respectively. The results are shown.

  The SIMS measurement results in FIG. 6 show the relationship between depth and atomic concentration. The depth here is expressed as 0 on the surface of the semiconductor substrate on which the paste composition or the aluminum paste is applied. The atomic concentration indicates the concentration of the n-type dopant element doped in the semiconductor substrate, and specifically indicates the atomic concentration of aluminum and the atomic concentration of phosphorus. Here, the n layer is formed when the atomic concentration of phosphorus, which is an n-type dopant, is higher than the atomic concentration of aluminum, which is a p-type dopant.

  As shown in FIG. 6A, in the substrate sample of Comparative Example 1, phosphorus, which is an n-type dopant element, is not detected but only aluminum is detected.

  On the other hand, in FIGS. 6B and 6C, the phosphorus concentration as the n-type dopant is higher than the concentration of aluminum as the p-type dopant, and the n-type layer has a depth of 5.0 to 6.0 μm. It was confirmed that it was formed.

  The results of the above examples show that the formation of the n-type Si layer and the p + -type Si layer necessary for forming the solar cell can be formed by a single baking process.

  When performing n-type layer formation and p + type layer formation by a conventional impurity thermal diffusion method, separate steps are required for the n type layer formation step and the p + type layer formation step, and each step is performed at 800 ° C. or higher. More than a minute heat treatment was required. On the other hand, by using a predetermined aluminum paste as in the example, a solar cell structure in which an n-type layer formation and a p + type layer are simultaneously formed by a heat treatment at 800 ° C. or more and 1 minute or less can be produced. did it.

  Similar to the above embodiment, the same effect as in the above-described embodiment can be obtained by using arsenic, antimony, and bismuth, which are group 5 elements, which are n-type dopants for a semiconductor substrate such as silicon or germanium as in the case of phosphorus. It is expected to be.

1 Semiconductor substrate 2 Coating film 2
3a Aluminum layer 3b Alloy layer containing aluminum 3c Diffusion layer 4 Aluminum coating 5a Aluminum layer 5b Alloy layer containing aluminum 5c Diffusion layer

Claims (3)

Applying a first aluminum paste containing aluminum powder and an n-type dopant element on a silicon substrate;
The silicon substrate coated with the first aluminum paste is baked, the silicon contained in the silicon substrate is reacted with the aluminum powder to form a liquid phase alloy, and the liquid phase alloy a step of diffusing an n-type dopant element to form an n-type semiconductor layer, an Al—Si alloy layer, and an aluminum layer on the silicon substrate;
Removing the aluminum layer and the Al-Si alloy layer;
With
The first aluminum paste contains the n-type dopant element in an amount of 1 part by mass to 1000 parts by mass with respect to 100 parts by mass of aluminum contained in the first aluminum paste .
The n-type dopant element is phosphorus;
A method for manufacturing a silicon substrate on which an n-type semiconductor layer is formed. The calcination, 577 ° C. or higher, 1200 ° C. is performed in the following range, method for manufacturing a silicon substrate according to claim 1. Before the firing, further comprising a step of applying a second aluminum paste containing aluminum powder to a region on the silicon substrate different from the region where the first aluminum paste is applied;
The silicon substrate according to claim 1 or 2 , wherein the second aluminum paste contains less than 1 part by mass of the n-type dopant element with respect to 100 parts by mass of aluminum contained in the second aluminum paste. Manufacturing method.