METHOD FOR FORMING n-TYPE SILICON GERMANIUM LAYER

Abstract

To provide a method for safely and easily forming an n-type silicon germanium layer.SOLUTION: A method for forming an n-type silicon germanium layer includes a firing step of preparing a paste composition containing a compound containing aluminum, germanium, and an n-type dopant element, a resin, and a solvent, applying the paste composition to a silicon-containing substrate, and heating the paste composition at a temperature of 600°C to 1400°C to form an alloy between the silicon component of the silicon-containing substrate and the aluminum, germanium, and n-type dopant element in the paste composition, the paste composition contains 1 mass% to 80 mass% of aluminum as a solid content in the paste composition, and contains more than 1 part by mass and 5000 parts by mass or less of germanium per 100 parts by mass of aluminum. The compound containing the n-type dopant element contains one element selected from phosphorus, antimony, arsenic, and bismuth.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a method for forming an n-type silicon germanium layer. [Background technology]

[0002] Silicon germanium (Si-Ge), a mixed crystal material of silicon and germanium, has been used as a semiconductor material. This semiconductor material is formed as a silicon germanium layer on a substrate such as silicon, and is used as part of a transistor or diode.

[0003] Methods under consideration for forming a silicon germanium layer include epitaxial growth by chemical vapor deposition (CVD) (see Patent Document 1), epitaxial growth by molecular beam epitaxy (MBE) (see Patent Document 2), film formation by sputtering using a Si-Ge alloy target (see Patent Document 3), and a method of forming a silicon germanium layer on silicon by applying a paste containing aluminum and germanium to a silicon layer and firing it (see Patent Document 4). Silicon germanium layers formed by these methods are used as part of transistors and diodes.

[0004] However, the methods disclosed in Patent Documents 1 and 2 have a problem in that they require the use of highly dangerous gases such as SiH4 and GeH4.

[0005] Furthermore, the methods disclosed in Patent Documents 1 to 3 require vacuum equipment in the epitaxial growth step and the film formation step by sputtering, which poses the problem of requiring a long time for these steps.

[0006] Furthermore, in the method disclosed in Patent Document 4, the germanium layer formed on the silicon substrate is doped with aluminum as a dopant to form a p-type silicon germanium semiconductor layer, which poses a problem that it cannot be used when an n-type semiconductor layer is required.

[0007] Therefore, there is a need for a method for forming a silicon germanium layer that does not require chemical vapor deposition or sputtering and that can safely and easily form an n-type silicon germanium layer. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Japanese Patent Application Laid-Open No. 2011-146684 [Patent Document 2] Japanese Patent Application Laid-Open No. 2004-172276 [Patent Document 3] Japanese Patent Application Laid-Open No. 2004-018946 [Patent Document 4] International Publication No. 2017 / 051775 Summary of the Invention [Problem to be solved by the invention]

[0009] An object of the present invention is to provide a method for forming a silicon germanium layer that can safely and easily form an n-type silicon germanium layer without requiring chemical vapor deposition or sputtering film formation. [Means for solving the problem]

[0010] As a result of extensive research into achieving the above object, the present inventors have found that the above object can be achieved by a method for forming an n-type silicon germanium layer, the method including, in this order, a preparation step of preparing a paste composition containing (i) a compound containing aluminum, germanium, and an n-type dopant element, (ii) a resin, and (iii) a solvent, a coating step, and a firing step, and have thereby completed the present invention.

[0011] That is, the present invention relates to the following method for forming an n-type silicon germanium layer. 1. A method for forming an n-type silicon germanium layer, comprising: A preparation step of preparing a paste composition containing (i) a compound containing aluminum, germanium, and an n-type dopant element, (ii) a resin, and (iii) a solvent; a coating step of coating the paste composition onto a silicon-containing substrate; and a firing step of heating at a temperature of 600°C or higher and 1400°C or lower to form an alloy between the silicon component of the silicon-containing substrate and the aluminum, germanium, and n-type dopant element in the paste composition, in this order; The paste composition contains the aluminum in an amount of 1% by mass or more and 80% by mass or less as a solid content in the paste composition, and the germanium in an amount of more than 1 part by mass and 5,000 parts by mass or less per 100 parts by mass of the aluminum, the compound containing an n-type dopant element contains at least one element selected from the group consisting of phosphorus, antimony, arsenic, and bismuth; the content of the compound containing the n-type dopant element is 1.5 parts by mass or more and 1000 parts by mass or less with respect to 100 parts by mass of the total content of the aluminum and the germanium, A forming method characterized by: 2. The method according to item 1, wherein the aluminum is aluminum powder and / or aluminum alloy powder having an average particle size of 1 μm or more and 20 μm or less. 3. In the applying step, the paste composition is applied to the silicon-containing substrate in an amount of 4 mg / cm on a dry basis. 2 More than 12mg / cm 2 Item 3. The method for forming an n-type silicon germanium layer according to item 1 or 2, characterized in that it is a step of applying in the following range. 4. The method according to any one of items 1 to 3, wherein the content of the resin in the paste composition is 0.1 to 10 parts by mass per 100 parts by mass of the aluminum. 5. The method according to any one of items 1 to 4, wherein the paste composition further contains a glass component. 6. The method according to item 5, wherein the content of the glass component in the paste composition is 0.1 to 3 parts by mass with respect to 100 parts by mass of the total of the aluminum and the germanium. 7. The method according to any one of items 1 to 6, further comprising a cooling step after the firing step. [Effects of the Invention]

[0012] The method for producing n-type silicon germanium of the present invention does not require chemical vapor deposition or sputtering film formation, and can safely and easily form an n-type silicon germanium layer. [Brief explanation of the drawings]

[0013] [Figure 1] 10 is a diagram showing a cross-sectional photograph (SEM image, 2000x magnification) of a measurement sample after a firing step in Example 2. FIG. [Figure 2] 10 is a diagram showing a cross-sectional photograph (SEM image, 3000x magnification) of a measurement sample after a firing step in Comparative Example 3. FIG. [Figure 3] FIG. 10 is a diagram showing a cross-sectional photograph (SEM image, 3000x magnification) of a measurement sample after a firing step in Comparative Example 7. DETAILED DESCRIPTION OF THE INVENTION

[0014] The method for forming an n-type silicon germanium layer of the present invention (hereinafter also simply referred to as "forming method") comprises, in this order, a preparation step of preparing a paste composition containing (i) a compound containing aluminum, germanium, and an n-type dopant element, (ii) a resin, and (iii) a solvent; a coating step of applying the paste composition onto a silicon-containing substrate; and a firing step of heating at a temperature of 600°C or higher and 1400°C or lower to form an alloy between the silicon component of the silicon-containing substrate and the aluminum, germanium, and n-type dopant element in the paste composition. The product is characterized in that the paste composition contains 1% by mass or more and 80% by mass or less of the aluminum as a solid content, and contains more than 1 part by mass and 5000 parts by mass or less of the germanium per 100 parts by mass of the aluminum, the compound containing the n-type dopant element contains at least one element selected from the group consisting of phosphorus, antimony, arsenic, and bismuth, and the content of the compound containing the n-type dopant element is 1.5 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of the total content of the aluminum and the germanium.

[0015] The forming method of the present invention has the above-mentioned configuration, and by applying the paste composition prepared in the preparation step to a silicon-containing substrate such as a silicon wafer and heating it, the silicon contained in the silicon-containing substrate and the compound containing aluminum, germanium, and an n-type dopant element in the paste composition form an alloy, and when the temperature drops after heating, the alloy recrystallizes and a silicon-germanium layer is formed on the silicon-containing substrate. Therefore, since the silicon-germanium layer can be formed by applying the paste composition to the silicon-containing substrate and heating it, there is no need to use highly dangerous gases such as SiH4 or GeH4, and there is no need to use equipment such as a vacuum device, so the silicon-germanium layer can be formed safely and easily without requiring a long time.

[0016] Each step of the method for forming an n-type silicon germanium layer of the present invention will be described in detail below.

[0017] The following description of the components may be based on representative embodiments and specific examples, but the present invention is not limited to such embodiments.

[0018] In the numerical ranges described in stages in this specification, the upper or lower limit of a certain numerical range can be arbitrarily combined with the upper or lower limit of another numerical range. Furthermore, in the numerical ranges described in this specification, the upper or lower limit of the numerical range may be replaced with a value shown in an example or a value that can be unambiguously derived from an example. Furthermore, in this specification, a numerical value connected with "to" means a numerical range that includes the numbers before and after "to" as the upper and lower limits.

[0019] In this specification, the expressions "contain" and "comprise" include the concepts of "contain," "include," "consist essentially of," and "consist only of."

[0020] In this specification, "A and / or B" and "at least one of A and B" mean either one of A and B, or both A and B.

[0021] 1. Preparation process The preparation step is a step of preparing a paste composition containing (i) a compound containing aluminum, germanium, and an n-type dopant element, (ii) a resin, and (iii) a solvent.

[0022] The paste composition used in the preparation step contains (i) a compound containing aluminum, germanium, and an n-type dopant element, (ii) a resin, and (iii) a solvent.

[0023] (aluminum) The aluminum is not particularly limited as long as it is in a form that can be contained in the paste composition, and examples thereof include aluminum powder and / or aluminum alloy powder.

[0024] The aluminum powder preferably has an aluminum content of 99.0% by mass or more, more preferably 99.9% by mass or more. The aluminum powder may be an aluminum alloy powder containing other metals in addition to aluminum. Examples of aluminum alloy powder include powders of alloys containing at least one element selected from the group consisting of iron, copper, manganese, magnesium, chromium, zinc, titanium, vanadium, gallium, nickel, boron, and zirconium. The content of each of these elements is preferably 1000 ppm or less, particularly 300 ppm or less, based on the total amount of the aluminum alloy powder.

[0025] The shape of the aluminum powder and / or aluminum alloy powder is not particularly limited, and may be any of spherical, elliptical, irregular, scaly, fibrous, etc. Among these, spherical shapes are preferred in terms of good printability and excellent reactivity with silicon.

[0026] The average particle size (D 50 ) is preferably 1 μm or more and 20 μm or less, more preferably 1 μm or more and 10 μm or less, and even more preferably 1 μm or more and 5 μm or less. When the average particle size of the aluminum powder is within the above range, the aluminum powder and / or aluminum alloy powder has excellent reactivity with silicon, and the printability of the paste composition is improved.

[0027] In this specification, the average particle size (D 50 ) indicates a value measured by a laser diffraction method, and specifically indicates the particle size of particles that correspond to 50% of the total number of particles on a particle size distribution curve obtained by calculating the particle size and the number of particles corresponding to this particle size.

[0028] The paste composition contains 1% by mass or more and 80% by mass or less of the aluminum as a solid content, assuming the paste composition to be 100% by mass. If the aluminum content is less than 1% by mass, an n-type silicon germanium layer cannot be formed satisfactorily. If the aluminum content exceeds 80% by mass, the reactivity of aluminum with silicon decreases, which in turn decreases the reactivity of germanium with silicon, making it impossible to form a silicon germanium layer. In addition, the viscosity of the paste composition increases, making uniform printing impossible. The lower limit of the aluminum content is preferably 1.5% by mass or more, more preferably 3% by mass or more, even more preferably 4% by mass or more, and particularly preferably 8% by mass or more. The upper limit of the aluminum content is preferably 70% by mass or less, more preferably 65% ​​by mass or less, even more preferably 60% by mass or less, and particularly preferably 50% by mass or less.

[0029] (germanium) The germanium is not particularly limited as long as it is in a form that can be contained in the paste composition, and examples thereof include germanium powder and / or germanium alloy powder.

[0030] The germanium powder preferably has a germanium purity of 98.0% by mass or more, more preferably 99.0% by mass or more. The germanium powder may be a germanium alloy powder containing other metals in addition to germanium. Examples of germanium alloy powders include alloy powders containing at least one element selected from the group consisting of iron, copper, manganese, magnesium, chromium, zinc, titanium, vanadium, gallium, nickel, boron, and zirconium. The content of each of these elements is preferably 1000 ppm by mass or less, particularly 300 ppm by mass or less, based on the total amount of the germanium alloy powder.

[0031] The shape of the germanium powder is not particularly limited, and may be any of spherical, elliptical, irregular, scaly, fibrous, etc. Among these, the spherical shape is preferred in terms of good printability and excellent reactivity with silicon.

[0032] In addition, the average particle diameter of the germanium powder (D 50 ) is preferably 1 to 20 μm, more preferably 1 to 10 μm, and even more preferably 1 to 5 μm. When the average particle size of the germanium powder is within the above range, the germanium powder has better reactivity with silicon, and the printability of the paste composition is improved.

[0033] The germanium content is more than 1 part by mass and not more than 5000 parts by mass per 100 parts by mass of aluminum. If the germanium content is 1 part by mass or less, the silicon germanium layer is not sufficiently formed. If the germanium content is more than 5000 parts by mass, the reaction of aluminum, which has a lower melting point than germanium, with silicon is hindered, the reactivity is reduced, and the silicon germanium layer is not formed. The germanium content is preferably 50 parts by mass or more, more preferably 100 parts by mass or more, even more preferably 200 parts by mass or more, and particularly preferably 500 parts by mass or more. Furthermore, the germanium content is preferably 4000 parts by mass or less, more preferably 3000 parts by mass or less, even more preferably 2500 parts by mass or less, and particularly preferably 2000 parts by mass or less.

[0034] (Compounds containing n-type dopant elements) The paste composition contains a compound containing an n-type dopant element.

[0035] The compound containing an n-type dopant element used in the present invention is a compound containing phosphorus, antimony, arsenic, or bismuth. If a compound other than the above-mentioned compound containing an n-type dopant element is used, the formation of an n-type silicon germanium layer is insufficient. Among these, a compound containing phosphorus is preferred because it can form an n-type silicon germanium layer more satisfactorily.

[0036] Specific examples of compounds containing the n-type dopant element include phosphorus oxide, phosphorus-containing glass, calcium phosphate, calcium hydrogen phosphate, phosphate ester, aluminum phosphorus alloy, phosphorus-doped silicon, antimony oxide, bismuth oxide, and bismuth glass.

[0037] The compound containing the n-type dopant element may be used alone or in combination of two or more.

[0038] The content of the compound containing an n-type dopant element is 1.5 parts by mass or more and 1000 parts by mass or less per 100 parts by mass of the total content of aluminum and germanium. If the content of the compound containing an n-type dopant element is less than 1.5 parts by mass, the silicon germanium layer is not sufficiently formed. If the content of the compound containing an n-type dopant element exceeds 1000 parts by mass, the reaction of aluminum, which has a lower melting point than germanium, with silicon is hindered, the reactivity is reduced, and the silicon germanium layer is not formed. The content of the compound containing the n-type dopant element is preferably 5 parts by mass or more, more preferably 10 parts by mass or more, and even more preferably 15 parts by mass or more. The content of the compound containing the n-type dopant element is preferably 500 parts by mass or less, more preferably 300 parts by mass or less, even more preferably 200 parts by mass or less, particularly preferably 100 parts by mass or less, and most preferably 50 parts by mass or less.

[0039] (resin) The paste composition contains a resin. If the paste composition does not contain a resin, the stability and printability of the paste composition will be reduced.

[0040] The resin is not particularly limited, and conventionally known resins can be used. Examples of such resins include thermosetting resins such as ethyl cellulose, nitrocellulose, polyvinyl butyral, phenolic resins, melamine resins, urea resins, xylene resins, alkyd resins, unsaturated polyester resins, acrylic resins, polyimide resins, furan resins, urethane resins, isocyanate compounds, and cyanate compounds, as well as polyethylene, polypropylene, polystyrene, ABS resins, polymethyl methacrylate, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, polyvinyl alcohol, polyacetal, polycarbonate, polyethylene terephthalate, polybutylene terephthalate, polyphenylene oxide, polysulfone, polyimide, polyethersulfone, polyarylate, polyether ether ketone, polytetrafluoroethylene, and silicone resins. Among these, ethyl cellulose is preferred because it provides superior paste composition stability and printability. These resins may be used alone or in combination of two or more.

[0041] The melting point of the resin is preferably 100 to 300° C., more preferably 150 to 300° C. When the melting point of the resin is within the above range, the reaction of aluminum with silicon is further accelerated, thereby improving the reactivity of germanium with silicon and making it easier to form a silicon germanium layer.

[0042] The resin content is not particularly limited, but is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 5 parts by mass, and even more preferably 0.7 to 2 parts by mass, relative to 100 parts by mass of aluminum. By keeping the resin content within the above range, the stability and printability of the paste composition can be further improved.

[0043] (solvent) The paste composition may contain a dispersion medium. When the paste composition contains a dispersion medium, the printability of the paste composition can be improved.

[0044] The dispersion medium is not particularly limited as long as it can disperse aluminum and germanium, and can be water, a solvent, etc. The paste composition may be in a form in which aluminum and germanium are dispersed in water and / or a solvent, or may be in a form containing aluminum, germanium, and an organic vehicle in which the resin component is dissolved in a solvent.

[0045] Known solvents can be used, and specific examples include butyl diglycol, diethylene glycol monobutyl ether, diethylene glycol monobutyl ether acetate, dipropylene glycol monomethyl ether, terpineol, etc. Among these, butyl diglycol, diethylene glycol monobutyl ether, and terpineol are preferred in terms of dispersibility and printability.

[0046] These dispersion media may be used alone or in combination of two or more.

[0047] The content of the dispersion medium is not particularly limited, but is preferably 1 to 30% by mass, and more preferably 5 to 20% by mass, relative to 100% by mass of the paste composition. By keeping the content of the dispersion medium within the above range, the stability and printability of the paste composition are further improved.

[0048] (glass component) The paste composition may contain a glass component other than the compound containing the n-type dopant element. When the paste composition contains a glass component, the reactivity between aluminum and silicon is improved, thereby improving the reactivity of germanium with silicon, making it easier to form a silicon germanium layer.

[0049] The glass components are not particularly limited as long as they are glass components other than the compound used as the compound containing the n-type dopant element. Preferably, they contain at least one of alkali metals and alkaline earth metals. Specifically, they preferably contain an oxide of at least one of the alkali metals: lithium, sodium, and potassium; and the alkaline earth metals: calcium, magnesium, strontium, and barium. The glass components may also contain one or more elements selected from the group consisting of Pb, V, B, Si, Sn, and Zn. Furthermore, lead-containing glass components or lead-free glass components such as vanadium-based, tin-phosphorus-based, zinc borosilicate-based, and alkali borosilicate-based glass components may be used. Considering the effects on the human body, the use of lead-free glass components is particularly desirable.

[0050] The softening point of the glass component is preferably 300 to 700° C., more preferably 400 to 600° C. When the softening point of the glass component is within the above range, the reaction between aluminum and silicon is further accelerated, thereby improving the reactivity of germanium with silicon and making it easier to form an n-type silicon germanium layer.

[0051] The glass component is not particularly limited as long as it can be contained in the paste composition, and examples thereof include glass powder. The average particle size of the glass powder is preferably 1 to 8 μm, more preferably 2 to 4 μm. If the average particle size of the glass powder is too small, the glass powder may aggregate during dispersion in the paste, while if it is too large, the formation of an n-type silicon germanium layer may be hindered.

[0052] The content of the glass component is not particularly limited, but is preferably 0.1 to 3 parts by mass, more preferably 0.1 to 1 part by mass, per 100 parts by mass of aluminum and germanium combined. When the content of the glass component is within the above range, the reactivity of aluminum with silicon is superior, thereby improving the reactivity of germanium with silicon, and making it easier to form an n-type silicon germanium layer.

[0053] (Other additives) The paste composition may contain other additives in addition to the aluminum, germanium, and n-type dopant element-containing compound, resin, solvent, and optional glass component. The additives are not particularly limited as long as they do not impair the effects of the present invention, and examples include antioxidants, corrosion inhibitors, antifoaming agents, thickeners (tackifiers), coupling agents, electrostatic agents, polymerization inhibitors, thixotropic agents, and anti-settling agents. Specifically, polyethylene glycol ester compounds, polyoxyethylene sorbitan ester compounds, sorbitan alkyl ester compounds, aliphatic polycarboxylic acid compounds, phosphate ester compounds, amide amine salts of polyester acids, polyethylene oxide compounds, and fatty acid amide waxes can be used.

[0054] The content of the other additives is not particularly limited, and is preferably about 0.01 to 2 parts by mass each relative to 100 parts by mass of aluminum.

[0055] The viscosity of the paste composition is preferably 5 to 100 Pa·s, and more preferably 10 to 40 Pa·s. When the viscosity of the paste composition is in the above range, the paste composition has excellent printability. In this specification, the viscosity is a value measured using a rotational viscometer (Brookfield: DV2T) with a spindle CP-51 at a rotation speed of 2.5 rpm.

[0056] The method for preparing the paste composition is not particularly limited, and the components may be mixed by stirring using a conventionally known method. For example, the paste composition can be produced by adding a compound containing aluminum, germanium, and an n-type dopant element, and a resin to the solvent, and optionally adding a glass component and other additives, followed by stirring and mixing at room temperature.

[0057] The paste composition used in the forming method of the present invention can be prepared by the preparation steps described above.

[0058] 2.Coating process The application step is a step of applying the paste composition to a silicon-containing substrate.

[0059] As the paste composition, the paste composition prepared in the above preparation step is used.

[0060] The silicon-containing substrate is not particularly limited as long as it contains silicon, and examples thereof include silicon substrates (silicon wafers). As the silicon substrate, a substrate obtained by slicing a silicon ingot can be used. The silicon substrate preferably has a silicon content of 99.0% by mass or more, more preferably 99.99% by mass or more.

[0061] The silicon substrate may contain elements other than silicon as impurities or additives. Such elements include boron, phosphorus, gallium, and aluminum, which are dopants for semiconductors, and oxygen, nitrogen, carbon, and iron, which are contained in the silicon ingot manufacturing process. The concentration of each of the other elements is preferably 100 ppm or less.

[0062] The thickness of the silicon-containing substrate is preferably 10 to 1000 μm, more preferably 100 to 800 μm, and even more preferably 300 to 600 μm.

[0063] The coating method for applying the paste composition to the silicon-containing substrate is not particularly limited, and examples thereof include spin coating, inkjet printing, and other coating methods. Examples of the coating method include dip coating and known roll coating methods, and specific examples include air doctor coating, blade coating, rod coating, extrusion coating, air knife coating, squeeze coating, impregnation coating, reverse roll coating, transfer roll coating, gravure coating, kiss coating, cast coating, and spray coating. Examples of the coating method include printing methods such as intaglio printing, which have an optimum viscosity range in a relatively low viscosity range, and printing methods such as screen printing, which have an optimum viscosity range in a relatively high viscosity range, and specific examples include stencil printing, intaglio printing, and lithographic printing.

[0064] The amount of paste composition applied to the silicon-containing substrate was 4 mg / cm2 in dry weight. 2 More than 12mg / cm 2 The following is preferred: 6 to 8 mg / cm 2 is more preferred.

[0065] By the coating step described above, the paste composition is coated onto the silicon-containing substrate.

[0066] 3. Firing process The firing step is a step in which the silicon-containing substrate onto which the paste composition has been applied in the above-mentioned application step is heated at a temperature of 600°C or higher and 1400°C or lower, thereby forming an alloy between the silicon component of the silicon-containing substrate and the aluminum, germanium, and n-type dopant element in the paste composition.

[0067] The firing atmosphere is not limited, but firing can be carried out in an air atmosphere or an inert gas atmosphere such as nitrogen.

[0068] The firing temperature is 600°C or higher and 1400°C or lower. If the firing temperature is lower than 600°C, the n-type silicon germanium layer cannot be formed sufficiently. If the firing temperature exceeds 1400°C, the silicon-containing substrate melts and the crystallinity decreases. The lower limit of the firing temperature is preferably 700°C or higher, more preferably 800°C or higher. The upper limit of the firing temperature is preferably 1300°C or lower, more preferably 1200°C or lower.

[0069] The baking time is preferably 3 to 600 seconds, more preferably 5 to 300 seconds. By setting the baking time within the above range, an n-type silicon germanium layer is more sufficiently formed. Note that the baking time may be adjusted depending on the baking temperature, but a high baking temperature and a short baking time are preferred in terms of excellent production efficiency.

[0070] Conventional CVD growth and sputtering techniques require a vacuum device, which requires at least 5 minutes for the evacuation process, and further require a deposition process of several minutes to several hours depending on the thickness of the n-type silicon germanium layer to be deposited. However, the method for forming an n-type silicon germanium layer of the present invention does not require a vacuum device, and an n-type silicon germanium layer can be formed within the firing time range described above.

[0071] The firing process described above causes the silicon component of the silicon-containing substrate to form an alloy with the aluminum, germanium, and n-type dopant element in the paste composition. After the firing process, the temperature is lowered, and the alloy recrystallizes to form an n-type silicon germanium layer on the silicon-containing substrate. This recrystallization also forms an Al-Ge-n-type dopant layer on the n-type silicon germanium layer, which can be removed by the removal process described below.

[0072] 4. Cooling process In the formation method of the present invention, after firing in the firing step, the temperature is lowered by allowing the alloy to cool to room temperature, and the alloy is recrystallized to form an n-type silicon germanium layer on the silicon-containing substrate. However, a cooling step may be included after the firing step.

[0073] The cooling method is not particularly limited, and cooling may be performed by a known cooling method such as air cooling.

[0074] The cooling rate during cooling is preferably 1 to 30°C / s, more preferably 10 to 20°C / s.

[0075] (Preheating process) The forming method of the present invention may include a preheating step between the coating step and the baking step to remove resin and the like from the paste composition coated on the silicon-containing substrate. By including the preheating step, the resin present in the paste composition can be removed, and the remaining solvent can also be removed, so that the n-type silicon germanium layer can be formed more satisfactorily.

[0076] The preheating conditions are not particularly limited, but it is preferable to preheat the material by heating in an air atmosphere or an inert gas atmosphere such as nitrogen by a conventionally known method.

[0077] The preheating temperature is preferably 300 to 500° C., more preferably 400 to 500° C. The preheating time is preferably 20 to 600 seconds, more preferably 20 to 60 seconds.

[0078] (drying process) The forming method of the present invention may include a drying step of drying the paste composition applied to the silicon-containing substrate before the preheating step, which allows the solvent present in the paste composition to be removed to some extent in advance, thereby allowing the n-type silicon germanium layer to be formed more satisfactorily.

[0079] The drying conditions are not particularly limited, but it is preferable to dry the film by heating in an air atmosphere or an inert gas atmosphere such as nitrogen, using a conventionally known method.

[0080] The drying temperature is preferably 100 to 400° C., more preferably 100 to 200° C. The drying time is preferably 20 to 600 seconds, more preferably 60 to 300 seconds.

[0081] The method of the present invention forms a silicon germanium layer on a silicon-containing substrate, as shown in FIG.

[0082] 1 is a cross-sectional photograph (SEM image, magnification 2000 times) of a measurement sample after the preparation step, coating step, and firing step in Example 2 described below. In FIG. 1, a silicon germanium layer (SiGe) is formed on a silicon-containing substrate (Si substrate). In FIG. 1, an aluminum-germanium layer-n-dopant layer (AlGe+n-dopant) is formed on the silicon germanium layer as an unnecessary layer.

[0083] (Removal process) The forming method of the present invention may include, after the baking step, a step of removing unnecessary layers, such as the aluminum-germanium layer-n-type dopant layer (AlGe+n-type dopant) formed on the silicon germanium layer in the baking step.

[0084] The method for removing the unnecessary layer is not particularly limited, and may be any conventionally known method, such as etching with an acid or alkali, polishing with an abrasive cloth or paper, or polishing with silicon oxide abrasive grains, aluminum oxide abrasive grains, diamond abrasive grains, or the like. [Example]

[0085] The present invention will be specifically described below with reference to examples and comparative examples, but the present invention is not limited to these examples.

[0086] In the examples and comparative examples, the following raw materials were used. Aluminum powder: manufactured by Toyo Aluminum Co., Ltd.; spherical powder with an aluminum content of 99.9% by mass; average particle size of 4 μm Germanium powder: Ge Powder (Furuuchi Chemical Co., Ltd.; non-spherical powder with a germanium content of 99.999% by mass; average particle size of 10 μm) Phosphorus compound: A mixture of glass containing P2O5 (P2O5-SnO glass frit) and phosphate ester (manufactured by Croda, product name O3A) Resin: Ethyl cellulose resin (Dow)

[0087] Example 1 To 100 parts by mass of aluminum powder, 30 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0088] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0089] Example 2 To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0090] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0091] Example 3 To 100 parts by mass of aluminum powder, 269 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0092] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and a size of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 1000°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0093] Example 4 To 100 parts by mass of aluminum powder, 269 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0094] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and a size of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 1100°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0095] Example 5 To 100 parts by mass of aluminum powder, 2423 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0096] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 1200°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0097] Example 6 To 100 parts by mass of aluminum powder, 1.5 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0098] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0099] Example 7 To 100 parts by mass of aluminum powder, 5,000 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0100] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and a size of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 1400°C for 10 seconds, and then allowed to cool to room temperature to obtain a test piece.

[0101] Example 8 To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 1,000 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0102] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0103] Example 9 To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 1.5 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0104] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0105] Example 10 To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0106] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and a size of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 600°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0107] (Comparative Example 1) To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder and 1 part by mass of ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0108] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0109] (Comparative Example 2) To 100 parts by mass of aluminum powder, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0110] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0111] (Comparative Example 3) To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0112] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 580°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0113] Comparative Example 4 To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 1.0 part by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0114] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0115] (Comparative Example 5) To 100 parts by mass of aluminum powder, 115 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 1,100 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0116] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0117] (Comparative Example 6) To 100 parts by mass of aluminum powder, 0.5 parts by mass of germanium powder was added, and to 100 parts by mass of the total of aluminum and germanium, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0118] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0119] (Comparative Example 7) To 100 parts by mass of aluminum powder, 5,500 parts by mass of germanium powder was added, and to 100 parts by mass of aluminum and germanium in total, 21.7 parts by mass of a phosphorus compound and 1 part by mass of an ethyl cellulose resin were added. In addition, butyl diglycol was added as a solvent so that its content was 15% by mass relative to 100% by mass of the paste composition, thereby preparing a paste composition.

[0120] The prepared paste composition was dried to a weight of 7 mg / cm 2 The coating was applied by screen printing to a silicon wafer with a thickness of 500 μm and dimensions of 2 cm × 2 cm so that the amount was 1. The wafer was then preheated for 30 seconds or less, baked at 900°C for 10 seconds, and then allowed to cool to room temperature to obtain a test specimen.

[0121] (Evaluation method) The following evaluations were carried out for the Examples and Comparative Examples.

[0122] Confirmation of n layer formation (SunsVoc measurement) The prepared test pieces were measured for n-layer formation using a SunsVoc measuring device (manufactured by Sinton Instruments, model number Suns-Voc), and evaluated according to the following evaluation criteria. ○: Formation of n layer was confirmed. ×: Formation of n layer was not confirmed.

[0123] Confirmation of SiGe layer formation (SEM, EDX observation) The prepared test piece was broken to prepare a cross section, and the cross section was photographed using a scanning electron microscope (SEM) and an energy dispersive X-ray analyzer (EDS) (manufactured by JEOL Ltd., model number: JSM-6510) and an SEM (manufactured by Keyence Corporation, model number: D 510) to confirm the formation of the SiGe layer, and evaluated according to the following evaluation criteria. ◯: Formation of a SiGe layer was confirmed. ×: Formation of a SiGe layer was not confirmed.

[0124] The results are shown in Table 1.

[0125] [Table 1]

[0126] The results in Table 1 show that the method for forming n-type silicon germanium of the present invention does not require the conventional chemical vapor deposition method and sputtering film formation, and can safely and easily form an n-type silicon germanium layer.

[0127] In contrast to this, in the comparative example, it was found that no n-layer and / or no SiGe layer was formed, and therefore an n-type silicon germanium layer could not be formed.

Claims

1. 1. A method for forming an n-type silicon germanium layer, comprising: A preparation step of preparing a paste composition containing (i) a compound containing aluminum, germanium, and an n-type dopant element, (ii) a resin, and (iii) a solvent; a coating step of coating the paste composition onto a silicon-containing substrate; and a firing step of heating at a temperature of 600°C or higher and 1400°C or lower to form an alloy between the silicon component of the silicon-containing substrate and the aluminum, germanium, and n-type dopant element in the paste composition, in this order; The paste composition contains the aluminum in an amount of 1% by mass or more and 80% by mass or less as a solid content in the paste composition, and contains the germanium in an amount of more than 1 part by mass and 5,000 parts by mass or less per 100 parts by mass of the aluminum, the compound containing an n-type dopant element contains at least one element selected from the group consisting of phosphorus, antimony, arsenic, and bismuth; the content of the compound containing the n-type dopant element is 1.5 parts by mass or more and 1,000 parts by mass or less with respect to 100 parts by mass of the total content of the aluminum and the germanium; A forming method characterized by:

2. 2. The method according to claim 1, wherein the aluminum is aluminum powder and / or aluminum alloy powder having an average particle size of 1 μm or more and 20 μm or less.

3. The applying step applies the paste composition to the silicon-containing substrate in a dry weight ratio of 4 mg / cm. ２ 12mg / cm or more ２ 2. The method according to claim 1, wherein the coating step is carried out in the following range:

4. 2. The method according to claim 1, wherein the content of the resin in the paste composition is 0.1 to 10 parts by mass per 100 parts by mass of the aluminum.

5. The method of claim 1 , wherein the paste composition further comprises a glass component.

6. 6. The method according to claim 5, wherein the content of the glass component in the paste composition is 0.1 to 3 parts by mass with respect to 100 parts by mass of the total of the aluminum and the germanium.

7. The method of claim 1 , further comprising a cooling step after the firing step.

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