JP3079355B2 - Method of fabricating silicon membrane with controlled residual stress - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a silicon membrane having residual stress. As the properties of micromachines become more and more sophisticated, there is a strong demand for adjusting the residual stress of a membrane frequently used in such a structure with a proper value. For example, a membrane that constitutes a pressure sensing part of a micro pressure gauge that must sense an extremely small pressure must react by elastic deformation even at an extremely small pressure.
A material having almost no residual stress is required.

If the residual stress of the membrane is a tensile stress, the elastic deformation of the membrane becomes smaller at an external pressure lower than the stress, making it difficult to sense the pressure. If the residual stress of the membrane is a thickness contraction stress, the membrane will not be seated. This is because the mechanical structure of the micro pressure gauge collapses due to bending. On the other hand, the membrane used for the substrate of the X-ray mask must have an appropriate magnitude of residual tensile stress without being too large. X
X-ray mask damage due to X-rays decreases as the membrane tensile stress increases, but if the tensile stress is too high,
The membrane is easily broken by an external impact.

[0003]

2. Description of the Related Art Sometimes, depending on the type of a micro machine, an accurate residual stress of a membrane is required, or it is necessary to design a uniform distribution of the residual stress of the membrane in a plane direction or a thickness direction. .

[0004]

However, most materials exist in a bulk state without stress, but in thin film or membrane states exhibit uncontrollable stress. For example, silicon nitride films, silicon oxide films, and silicon carbide films deposited by plasma enhanced chemical vapor deposition have an extremely large residual stress that changes with very large compressive and tensile stresses even when the deposition conditions change slightly. There are many difficulties associated with using them in stressed micromachines. In addition, a thermally grown silicon oxide film always shows only a constant value of compressive stress regardless of the growth conditions, and a chemical vapor deposited silicon nitride film has only an extremely large tensile stress. There are many problems that are extremely difficult to use in micro machines where the stress must be designed.

[0005]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a silicon membrane having a low impurity doping concentration and no stress.
It is an object of the present invention to provide a method of manufacturing a silicon membrane that can obtain a designed residual stress by doping an appropriate amount of impurities into the membrane.

One embodiment of the present invention for achieving the above object is to form a ring-shaped pattern on a substrate with a blocking film for blocking boron implantation; by implanting boron on the substrate, Forming a high-density boron-doped layer having a mismatch potential surrounded by a substrate in which the ring-shaped boron implantation formed by the barrier film pattern is blocked; and etching a local region of the substrate from a lower surface. Forming a membrane made of the boron-doped layer.

According to another embodiment of the present invention, there is provided a method of forming a blocking film pattern for blocking implantation of ring-shaped boron on a substrate; forming the blocking film pattern by implanting boron on the substrate. Forming a high-density boron-doped layer with no mismatch potential surrounded by a substrate region in which ring-shaped boron implantation is blocked; low-density doped silicon on the boron-doped layer on the substrate; Growing a layer; forming a protective layer on the epi silicon layer to protect the epi silicon layer from the substrate etching solution; etching a local region of the substrate from below to form the boron doped layer and the epi layer. Forming a membrane comprising a silicon layer and a protective film; removing the boron-doped layer from the membrane; Specific area by etching, characterized in that it comprises a step of heat-treating the impurity implantation to.

According to another embodiment of the present invention, there is provided a method of forming a first blocking film pattern on a substrate for blocking implantation of boron in a ring form; (1) forming a high-density boron-doped layer without a mismatch potential surrounded by a ring-shaped boron-implanted substrate region formed by a barrier film pattern; doping with a low-density impurity on the boron-doped layer; Growing an epi silicon layer; forming a second barrier layer on the substrate, locally etching to form a window, and forming an impurity doped layer; and depositing the epi silicon layer from a substrate etching solution. Forming a protective film on the impurity-doped layer for protecting the substrate; etching a local region from the lower surface of the substrate to form the boron-doped layer and the epi-silicon layer; The step of forming a membrane comprising a protective film; characterized in that the and the boron-doped layer comprises the step of heat treatment is removed from the membrane.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail with reference to the attached drawings. The principle of adjusting the residual stress of the silicon membrane by implanting impurities is as follows. When a substitutional impurity having a smaller atomic diameter than silicon is doped into silicon, the distance between silicon atoms becomes longer than in the original state, but this eventually appears as a pulling force between silicon atoms. As a result, tensile stress is generated in the silicon layer doped with impurities. Similarly, when a substitutional impurity having a larger atomic diameter than silicon is doped into silicon, the distance between the silicon atom and the atom becomes short, and a balance force is generated between the silicon atom and the impurity. Compressive stress is generated in the silicon layer doped with. Therefore, a tensile stress is generated in a silicon layer doped with boron or phosphorus having an atomic diameter smaller than silicon, and a compressive stress is generated in a silicon layer doped with gallium or antimony having an atomic diameter larger than silicon. .

The stress of a silicon layer doped with such impurities in a substitutional manner is theoretically directly proportional to the doping density of the impurities as shown in the following equation. Stress = proportional constant × doping density (1) Here, the magnitude and sign of the proportional constant are determined by the type of impurity. That is, when the size of the impurity atom is smaller than the silicon atom, the proportional constant has a positive sign and the stress becomes a tensile stress, and when the size of the impurity atom is larger than the silicon atom, the proportional constant is negative. And the stress becomes a compressive stress. Further, the larger the difference between the size of the impurity atom and the size of the silicon atom, the larger the absolute value of the proportional constant.

There are roughly two methods for fabricating a small low-density impurity-doped silicon membrane whose residual stress should be adjusted according to the principles described above.
First, a membrane is manufactured by etching a silicon substrate doped with impurities at a low density from a potassium hydroxide solution, leaving only a few microns thick. The silicon membrane manufactured by this method has the advantage that there is no residual stress, but the etching rate of silicon is very sensitive to the concentration and temperature of the potassium hydroxide solution, and the thickness of the obtained silicon substrate is on the order of microns. However, there is a disadvantage that it is very difficult to obtain a membrane having an accurate thickness because it cannot be ensured that the membrane is uniform.

Second, after forming silicon doped with boron at high density on the surface of the silicon substrate, an epi silicon layer doped with impurities at low density is grown thereon, and ethylene diamond Catechol-
The silicon substrate doped with impurities at a low density is obtained by sequentially etching the silicon substrate and the boron-doped layer serving as an etching stop layer with an EPW solution using a mixed solution of water (hereinafter referred to as an EPW solution). Is the way. In this method, since the thickness of the ep silicon layer becomes the thickness of the final silicon membrane, there is an advantage that a silicon membrane of a desired thickness can be easily obtained by adjusting the thickness of the ep silicon layer. It is not widely used for two reasons.

The first reason is that a mismatch potential and a compressive stress are inevitably generated in the epi silicon layer. In order for the boron-doped layer 2 to be used as an etching stop layer in an EPW solution, the boron-doping density must be 7 × 10 ¹⁹ / cm ³ or more. The tensile stress becomes very large, and a mismatch potential 7 is generated between the substrate and the boron-doped layer as shown in FIG. Such residual stress reduces the residual tensile stress of the boron-doped layer and at the same time reduces the lattice size 5 of the boron-doped layer on a plane compared to the lattice size 4 on the plane of the substrate.

Therefore, when the epi silicon layer 3 having a larger planar lattice size (that is, the same as the lattice size of the substrate) is formed by the boron doping having the reduced lattice size, the epi silicon Layer 3 becomes subject to compressive stress. If the generated compressive stress is very large, a mismatch potential 8 is generated in the epi silicon layer while a part of the stress is buffered.

As described above, a silicon membrane made of epi silicon having a mismatching potential with a compressive stress not only buckles but also deteriorates mechanical properties such as breaking strength. The unexplained reference numeral 6 in FIG. 1 indicates the size of the planar lattice of the epi silicon layer grown on the high-density boron-doped layer where the mismatch potential has been generated.

However, if the boron-doped layer can be formed without a mismatch potential as shown in FIG. 1 (on the right-hand side), the lattice size 9 in the plane of the boron-doped layer is maintained as in the substrate. Therefore, the lattice size 10 on the plane of the epi silicon layer grown thereon matches the boron doping layer, and no stress and mismatch potential are generated in the epi silicon layer.

Second, in an actual case, it is difficult to adjust the residual stress by doping selected impurities into a low-density doped silicon membrane because the above equation (1) does not hold well. The reason why the formula 1 does not hold well is that, as described above, a mismatched potential always occurs in a layer doped with a high density of impurities. Therefore, the residual stress generated by the impurity implantation is buffered by the mismatch potential, so that the residual stress of the impurity-doped layer is actually smaller than the value expected from the relationship of Equation 1. In general, the position of the mismatch potential in terms of the planar density and the depth in the impurity-doped layer cannot be predicted due to the heat treatment of the substrate, the type and amount of the doped impurity, and the like. The residual stress of the impurity-doped layer also becomes unpredictable.

However, in the present invention, a high-concentration boron-doped layer having no mismatch potential is formed thereon, and a low-density impurity-doped EP silicon layer having no stress and mismatch potential is formed thereon. After growing
Produce a stress-free, low-density impurity-doped silicon membrane that has a temporarily accurate thickness and is stress-free, and the desired amount of impurities selected to prevent secondary mismatch potential in this membrane By doping,
A silicon membrane having a designed residual stress can be manufactured.

An embodiment according to the present invention will be described in detail as follows. First, as shown in FIG. 2, a silicon substrate 1 having an impurity doping density of 1 × 10 ¹⁸ / cm ³ or less.
1 has a density of 5 × 10 5 surrounded by a boron-doped substrate portion 12 in the form of a ring having a width of 100 μm or more using the method described in FIGS.
A boron-doped layer 13 having a depth of not less than ¹⁹ / cm ^{3 and not} less than 1 micron is formed in an area of about 2 cm × 2 cm. The boron-doped layer surrounded by the ring pattern is surrounded by a substrate region in which ring-shaped boron is not doped, so that a mismatch potential does not occur in this region, and the crystallinity of the boron-doped layer is maintained. .

Next, the area of the lower surface of the substrate, which serves to block the implantation of boron during the boron doping, is 1 cm × 1.
After removing the blocking film 14 contained in the boron-doped layer on the upper surface of the substrate in a planar manner, the substrate is etched with an EPW solution. As shown in FIG. 3, a silicon membrane 15 doped with boron at a high concentration is obtained. Is produced. Since the silicon membrane manufactured by such a method does not include a mismatch potential, the residual stress is determined by the relationship of Equation 1. In addition, a silicon membrane doped with boron manufactured by a general method has striped irregularities due to a mismatch potential on its surface, so that the mechanical properties of the membrane are deteriorated. Since the silicon membrane does not include a mismatch potential, it has a very uniform surface state without any pattern.

FIGS. 4 and 5 show an embodiment for manufacturing a silicon membrane having a desired residual stress distribution by implanting selected impurities according to the present invention. As shown in FIG. 4, the impurity doping density at which boron is not doped is 1 × 10 ¹⁸ using the method described with reference to FIGS.
/ Cm ³ or less on the upper surface of the silicon substrate 18.
A ring-shaped region 19 of 0 μm or more is formed, and a boron-doped layer 20 having a density of 5 × 10 ¹⁹ / cm ³ or more and a depth of 1 μm or more is formed in an area of about 2 cm × 2 cm. Also, an area of 1 cm × 1 cm is formed on the lower surface of the substrate.
In FIG. 5, a region 21 in which boron doping is cut off and which is planarly included in the boron doping layer on the upper surface of the substrate is formed.
As shown in FIG.
An epi silicon layer 22 doped at ¹⁸ / cm ³ or less is grown to a thickness of 1 micron or more at 1100 ° C. using SiHCl ₃ gas.

Next, as shown in FIG. 6, a silicon oxide film 23 formed by chemical vapor deposition as a protective film for protecting the epi silicon layer 3 with an EPW solution is deposited on the epi silicon layer 22. 7 is etched with an EPW solution, as shown in FIG. 7, a boron-doped layer, an epi silicon 22 layer, and a membrane 24 formed of a silicon oxide film 23 formed by chemical vapor deposition are formed. Is done. When this membrane is immersed in a mixed solution of hydrofluoric acid + nitric acid + acetic acid, as shown in FIG. 8, the boron doping layer 20 is etched so that only the silicon oxide film 23 and the epi silicon layer 22 remain.

Next, as shown in FIG. 9, the silicon oxide film 23 deposited by chemical vapor deposition is locally etched to a thickness of 1.5 c.
A window 26 having an area of mx 1.5 cm is formed, and a desired amount of ions of a selected impurity are implanted. That is, when the residual stress of the membrane is used as the tensile stress according to the relationship given in the equation 1, when boron or phosphorus is used as the compressive stress, gallium or antimony is injected in an amount proportional to the magnitude of the stress.

Since the impurity-implanted layer 27 is surrounded by the region 28 in which the impurity implantation is interrupted by the silicon oxide film 23 deposited by chemical vapor deposition, no mismatch potential is generated in this region. , The stress of the membrane can be adjusted using the relationship of equation (1). then,
When heat treatment is performed in a nitrogen atmosphere at 900 ° C. for 30 minutes, the implanted impurities are activated, and a desired stress is generated in the membrane. If the heat treatment is performed at a higher temperature for a longer time, the implanted impurities are redistributed uniformly according to the thickness of the membrane, as shown in FIG. 10, so that the stress is uniformly distributed according to the thickness of the silicon membrane 29. Is obtained. When the silicon oxide film deposited by chemical vapor deposition in FIG. 8 is located in a local region of the silicon membrane, a silicon membrane having a different residual stress distribution according to a planar position can be manufactured.

FIGS. 11-14 show another embodiment for fabricating a silicon membrane having the desired residual stress distribution provided by the present invention. A silicon substrate 21 having a low impurity doping concentration is provided with a boron-doped layer 20 having a high density of boron, and a low-density impurity-doped epi silicon layer 22 is grown thereon. As shown in FIG.
A window 35 having an area of 1.5 cm is formed, and a doping layer 36 in which a desired amount of the selected impurity is implanted is formed.

In the present invention, a chemical vapor deposited silicon oxide film having a thickness of 1 micron was used as the barrier film. Then, a heat treatment is performed for 30 minutes in a nitrogen atmosphere at 900 ° C. for 30 minutes to activate the implanted impurities. As shown in FIG. Oxide film 37 is deposited and this substrate is
When etched with W solution, as shown in FIG. 13, about 1 cm × 1 cm
A boron-doped layer, an epi silicon layer 22 having a selected impurity implanted on the surface thereof, and a membrane 38 formed of an oxide film are manufactured. then,
This membrane is immersed in a mixed solution of hydrofluoric acid + nitric acid + acetic acid to etch and remove the boron-doped layer 20,
When the oxide film 37 is removed from the hydrofluoric acid solution, as shown in FIG. 14, a silicon membrane 39 having a desired current stress is obtained. In order to obtain a membrane having a uniform residual stress in the thickness direction, a long time is required at a high temperature. Heat treatment is performed for a time.

As in the embodiment of FIGS. 4 to 10, FIG.
When the barrier film window is located in a local region of the final membrane, it is possible to manufacture a silicon membrane having a different residual stress distribution according to a planar position. FIGS. 15 to 18 show various methods for forming a high-density boron-doped silicon layer having no mismatch potential on a low-density impurity-doped silicon substrate used in the above embodiments. Is shown.

FIG. 15 shows a structure in which a ring pattern 52 is formed of a silicon oxide film deposited by chemical vapor deposition on the silicon substrate 51, and then a boron doping layer 53 is formed.
FIG. 16 shows that about 2000 .ANG.
The ring pattern 54 is formed of the silicon nitride film of FIG. FIG. 17 shows a double ring pattern 56 formed of a silicon oxide film or a mixed layer of a silicon oxide film and a silicon nitride film formed by chemical vapor deposition, and a groove 57 formed by etching a substrate between the rings. .

FIG. 18 shows a groove 59 in which the substrate is etched in the form of a ring, and a ring pattern 60 formed of a silicon oxide film or a mixed layer of a silicon oxide film and a silicon nitride film formed by chemical vapor deposition. It was formed so as to cover the groove of the form. Further, the blocking film for blocking boron doping in the above embodiment is made of a photosensitive agent, a chemical vapor deposition silicon oxide film, or a mixed layer of a silicon oxide film and a silicon nitride film. , At least carbon, oxygen, nitrogen, argon, silicon,
It is composed of any one of phosphorus, boron, arsenic, antimony, aluminum and gallium.

[0030]

As described in the above embodiments, fabricating a silicon membrane by the method provided in the present invention provides a membrane having the exact value of residual stress required in very sophisticated micromachines. In addition to this, it is possible to adjust the desired stress distribution in the plane direction and the thickness direction of the membrane.

[Brief description of the drawings]

FIG. 1 is an illustration of an epi-silicon lattice grown on a boron-doped silicon layer.

FIG. 2 is a cross-sectional view of a substrate showing a sequence of manufacturing steps of a high-concentration boron-doped silicon membrane having a tensile stress as a residual stress.

FIG. 3 is a cross-sectional view of the manufactured silicon membrane.

FIG. 4 is a cross-sectional view of a substrate showing a process sequence of manufacturing a silicon membrane having a residual stress adjusted by doping an impurity having a residual stress adjusted by doping a selected impurity after etching the substrate; .

FIG. 5 is a cross-sectional view of the substrate in the same process.

FIG. 6 is a sectional view of the substrate in the same process.

FIG. 7 is a sectional view of the substrate in the same process.

FIG. 8 is a sectional view of the substrate in the same process.

FIG. 9 is a cross-sectional view of the substrate in the same process.

FIG. 10 is a sectional view of the substrate in the above-described step.

FIG. 11 is a cross-sectional view of a substrate showing a process sequence of manufacturing a silicon membrane in which a residual stress is adjusted by doping a selected impurity and etching the substrate.

FIG. 12 is a cross-sectional view of the substrate in the above step.

FIG. 13 is a cross-sectional view of the substrate in the above step.

FIG. 14 is a cross-sectional view of the substrate in the above step.

FIG. 15 is a cross-sectional view of a substrate showing various methods for forming a high-concentration boron doping layer having no mismatch potential.

FIG. 16 is a sectional view of the same substrate.

FIG. 17 is a cross-sectional view of the same substrate.

FIG. 18 is a sectional view of the same substrate.

[Explanation of symbols]

1,18,51 silicon substrate 2,13,20,53,55,58,61 high-concentration boron doping layer 3,22 ep-silicon layer 7,15,26,35 window 16,27,36 impurity-doped layer 17, 29, 38, 39 Membrane 23, 27 Protective film 34 Blocking film 56, 60 Ring pattern 57, 59 Groove

────────────────────────────────────────────────── ─── Continuing from the front page (72) Inventor Han Chul Hee 1-Block, Hanul Apartment 1-Sin-Song, Yusong-gu, Daejeon, Republic of Korea 103-502 (72) Inventor Soo Du Wan, Chamsi Lubon Dong, 301, Songpa-gu, Seoul, South Korea. -15 (56) References JP-A-62-26771 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01L 29/84 H01L 21/027 H01L 21/306 H01L 49/00

Claims (32)

(57) [Claims] 1. A method of fabricating a silicon membrane having an adjusted residual stress, comprising: forming a ring-shaped pattern on a substrate with a blocking film for blocking boron implantation; implanting boron on the substrate; Forming a high-concentration boron-doped layer 13 having no mismatch potential surrounded by the substrate 12 in which the ring-shaped boron implantation formed by the barrier film pattern is blocked; and etching a local region of the substrate from below. The boron doping layer 13
Forming a membrane 15 comprising: 2. The method according to claim 1, wherein the substrate is a silicon substrate. 3. The method according to claim 1, wherein the blocking film is a photosensitive agent,
A method for manufacturing a silicon membrane, wherein the method is a chemical vapor deposition silicon oxide film or a mixed layer of a silicon oxide film and a silicon nitride film. 4. The method for manufacturing a silicon membrane according to claim 2, wherein the impurity doping density of the silicon substrate is 1 × 10 ¹⁸ / cm ³ or less. 5. The method according to claim 1, wherein said boron doping method is ion implantation or diffusion. 6. The method for manufacturing a silicon membrane according to claim 1, wherein the boron doping density of the boron doping layer is 5 × 10 ¹⁹ / cm ³ or less. 7. The method according to claim 1, wherein the substrate etching solution is a mixed solution of ethylene diamond-pyrocatechol-water (EP
W solution). 8. A method of manufacturing a silicon membrane having a controlled residual stress, comprising: forming a blocking film pattern on a substrate for blocking implantation of boron in a ring form; Forming a high-concentration boron-doped layer 20 without a mismatching potential surrounded by a substrate region 17 in which ring-shaped boron implantation formed by the blocking film pattern is blocked; and on the boron-doped layer 20 on the substrate. Growing an epi-silicon layer 22 doped with impurities at a low concentration; forming a protective film 23 on the epi-silicon layer to protect the epi-silicon layer from a substrate etching solution; Etching to form a membrane 24 comprising the boron-doped layer 20, the epi silicon layer 22 and the protective film 23; Step to remove fine the boron doped layer 20 from the membrane; etching the localized region of the protective film 23, manufacturing method of a silicon membrane, which comprises a step of heat treating the impurity implantation to. 9. The method according to claim 8, wherein the substrate is a silicon substrate. 10. The method for manufacturing a silicon membrane according to claim 8, wherein the blocking film is a photosensitive agent, a silicon oxide film deposited by chemical vapor deposition, or a mixed layer of a silicon oxide film and a silicon nitride film. . 11. The method for manufacturing a silicon membrane according to claim 9, wherein the doping concentration of the silicon substrate is 1 × 10 ¹⁸ / cm ³ or less. 12. The method according to claim 8, wherein the doping concentration of the boron-implanted layer is 5 × 10 ¹⁹ / cm ³ or less. 13. The method of manufacturing a silicon membrane according to claim 8, wherein said boron doping method is ion implantation or diffusion. 14. The method of manufacturing a silicon membrane according to claim 8, wherein the doping concentration of the epi silicon layer 22 is 1 × 10 ¹⁸ / cm ³ or less. 15. The fabrication of a silicon membrane according to claim 8, wherein the protective film is a photosensitive agent, a chemical vapor deposited silicon oxide film, or a mixed layer of a silicon oxide film and a silicon nitride film. Method. 16. The method for manufacturing a silicon membrane according to claim 8, wherein the substrate etching solution is a mixed solution (EPW solution) of ethylene diamine-pyrocatechol-water. 17. The method for manufacturing a silicon membrane according to claim 8, wherein the layer into which boron is implanted at a high concentration is removed from a mixed solution of hydrofluoric acid + nitric acid + acetic acid. 18. The silicon membrane according to claim 8, wherein the impurity is any one of carbon, oxygen, nitrogen, argon, silicon, a phosphate compound, boron, arsenic, antimony, aluminum, and gallium. Production method. 19. The method of manufacturing a silicon membrane according to claim 8, wherein said impurity doping method is ion implantation or diffusion. 20. A method of fabricating a silicon membrane having a controlled residual stress, comprising: forming a first blocking film pattern on a substrate to block implantation of ring-shaped boron; implanting boron on the substrate. As a result, the first
Forming a high-concentration boron-doped layer 20 having no mismatch potential surrounded by a ring-shaped boron-implanted substrate region formed by a blocking film pattern; and a low-concentration impurity on the boron-doped layer 20. Growing a doped epi-silicon layer 22; forming a second barrier layer on the substrate, locally etching to form a window 35, and then forming an impurity doped layer 36; Forming a protective layer 37 for protecting the epi silicon layer 22 on the impurity doped layer 36; etching a local region of the substrate from below to form the boron doped layer, the epi silicon layer, and the protective layer; Forming the membrane 38; and removing the boron-doped layer from the membrane and heat-treating the same. Silicon membrane production method. 21. The method according to claim 20, wherein the substrate is a silicon substrate. 22. The silicon membrane according to claim 20, wherein the first blocking film is a photosensitive agent, a silicon oxide film deposited by chemical vapor deposition, or a mixed layer of a silicon oxide film and a silicon nitride film. Production method. 23. The method for manufacturing a silicon membrane according to claim 21, wherein a doping density of the silicon substrate is 1 × 10 ¹⁸ / cm ³ or less. 24. The method according to claim 20, wherein the boron-implanted layer has a doping density of 5 × 10 ¹⁹ / cm ³ or more. 25. The method for manufacturing a silicon membrane according to claim 20, wherein said boron doping method is ion implantation or diffusion. 26. The method for manufacturing a silicon membrane according to claim 20, wherein the doping density of the epi silicon layer is 1 × 10 ¹⁸ / cm ³ or less. 27. The method for manufacturing a silicon membrane according to claim 20, wherein the second barrier film is a photosensitive agent, a silicon oxide film deposited by chemical vapor deposition, or a mixed layer of a silicon oxide film and a silicon nitride film. . 28. The silicon membrane according to claim 20, wherein the impurity is any one of carbon, oxygen, nitrogen, argon, phosphorus, boron, arsenic, antimony, aluminum and gallium. Production method. 29. The method for manufacturing a silicon membrane according to claim 20, wherein said impurity doping method is ion implantation or diffusion. 30. The method of manufacturing a silicon membrane according to claim 20, wherein the protective film is a photosensitive agent, a silicon oxide film deposited by chemical vapor deposition, or a mixed layer of a silicon oxide film and a silicon nitride film. Method. 31. The substrate etching solution according to claim 20, wherein
A method for producing a silicon membrane, which is a mixed solution (EPW solution) of ethylenediamin-pyrocatechol-water. 32. The method for manufacturing a silicon membrane according to claim 20, wherein the layer into which boron is implanted at a high density is removed with a hydrofluoric acid + nitric acid + acetic acid solution.