JP2000228390A - Etching method, semiconductor device, and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an etching method which can uniformly remove the entire face of a layer which comes into contact with a semiconductor layer on a substrate, and can also adjust the etching amount, and can restrict an excess etching on the semiconductor layer. SOLUTION: A epitaxial layer 13 grown on a semiconductor substrate via an isolated layer 12c' is released from the semiconductor substrate in the isolated layer, and is transferred to a plastic film substrate 21. Next, a film substrate 21 is fixed to a fixing stand 32, which is rotated, while an etchant is supplied to the isolated layer 12c' through a pipe 34. Since the etchant is uniformly supplied to the entire exposed face of the isolated layer 12c' due to the centrifugal force caused by the rotation of the film substrate 21, the isolated layer is etched uniformly to start. When the isolated layer is etched by a prescribed amount, the etchant is stopped supplying, and pure water is supplied onto a face to be etched through a pipe 35. Thus, the face to be etched is cleaned, and chemical reaction is stopped by the etchant.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an etching method for removing a layer to be etched existing in contact with a semiconductor layer for forming an element, and a method for manufacturing a semiconductor device such as a solar cell by using the etching method. And a semiconductor device manufactured thereby.

[0002]

2. Description of the Related Art In recent years, some solar cells have been put to practical use. In order for this solar cell to be used in earnest, it is important to save resources and reduce costs, and consider energy conversion (light-to-electric conversion) efficiency and shortening the energy recovery period. In this case, a thin-film solar cell is preferable to a thick-film solar cell. Furthermore, a thin-film solar cell can be bent to some extent, and can be mounted on, for example, a curved surface of an automobile body or a curved external portion of a portable electric product to generate power. It has the advantage of spreading.

[0003] As a method of manufacturing a thin film solar cell,
For example, Japanese Patent Application Laid-Open Nos.
There is a method disclosed in JP-A-135500. In this method, a porous layer is formed as a separation layer on a single-crystal silicon substrate, a semiconductor layer serving as an active region of a solar cell is grown on the porous layer, and then an adhesive is used on the semiconductor layer. Then, the semiconductor layer is peeled off from the single crystal silicon substrate together with the plastic plate by using a porous layer as a peeling means.

As another method, there is a method disclosed in Japanese Patent Application Laid-Open No. Hei 10-79524 by the same applicant as the present applicant. In this method, after the semiconductor layer is separated from the single crystal silicon substrate by the above-described method and transferred to a transparent substrate made of resin, glass, or the like, an etching process is performed on the separated surfaces on the transparent substrate side and the single crystal silicon substrate side, respectively. Then, the remaining portions of the separation layer adhered to the respective substrate sides are removed together. When a thin-film solar cell is manufactured using this method, it is possible to avoid a decrease in the electromotive force of the solar cell due to the presence of the remaining portion of the porous layer. In addition, by forming irregularities (so-called texture) on the back surface of the semiconductor layer (the surface opposite to the surface facing the transparent substrate), light is effectively confined in the semiconductor layer and the efficiency of the battery is improved. Can be planned.

[0005]

However, the method disclosed in Japanese Patent Application Laid-Open No. H10-79524 is realized by directly immersing the porous layer in an etching solution in a chemical solution tank. There is a problem that etching is likely to be uneven. There is also a problem that there is a risk that the active region of the solar cell is over-etched. Furthermore, when a resin substrate that is currently frequently used as a transparent substrate is used, the resin may corrode when the resin substrate and the etchant come into contact with each other in the chemical solution tank. It was necessary to select and use a resin having good corrosion resistance to the liquid.

The present invention has been made in view of the above problems, and a first object of the present invention is to enable a layer to be etched existing in contact with a semiconductor layer for forming an element to be uniformly removed over the whole. An object of the present invention is to provide an etching method capable of adjusting the amount of etching and suppressing the occurrence of over-etching in a semiconductor layer.

A second object of the present invention is to provide a method of manufacturing a thin film device such as a solar cell through a transfer step, and to uniformly remove a remaining portion of a separation layer attached to the thin film device. It is an object of the present invention to provide a method of manufacturing a semiconductor device capable of adjusting the amount of etching and suppressing the occurrence of overetching of a thin film element, and a semiconductor device manufactured by the method.

[0008]

An etching method according to the present invention is a method for selectively removing a layer to be etched which is present in contact with a semiconductor layer provided on a substrate. The etching amount is adjusted by supplying the etching solution to the layer to be etched while rotating the substrate and fixing the chemical reaction by the etching solution at a predetermined timing. .

A method of manufacturing a semiconductor device according to the present invention comprises the steps of forming a semiconductor layer on a first substrate via a separation layer;
Transferring the semiconductor layer to the second substrate by peeling the semiconductor layer from the first substrate at the separation layer;
Removing the remaining portion of the separation layer by supplying an etchant to the surface of the separation layer attached to the semiconductor layer transferred to the substrate side.

In the semiconductor device according to the present invention, after the semiconductor layer is transferred from the first substrate to the second substrate, an etching solution is selectively supplied to the surface of the separation layer attached to the second substrate. And at least a part of the remaining portion of the separation layer is removed.

In the etching method according to the present invention, the layer to be etched rotates together with the substrate, and an etching solution is supplied to the surface thereof. Therefore, the etching liquid is uniformly supplied over the entire surface of the layer to be etched by the centrifugal force generated with the rotation of the layer to be etched, and the etching is performed uniformly. Thereafter, the chemical reaction by the etchant is stopped at a predetermined timing, and the etching amount of the layer to be etched is adjusted.

In the method for manufacturing a semiconductor device according to the present invention,
The semiconductor layer formed over the first substrate is separated from the first substrate at the separation layer and transferred to the second substrate. After that, the etchant is supplied only to the surface of the separation layer attached to the transferred semiconductor layer, and unnecessary portions of the separation layer are uniformly removed. Thereby, the semiconductor device of the present invention is obtained.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings. Here, a case where a solar cell is manufactured as an example of a semiconductor device will be described.

(First Embodiment) First, a method of manufacturing a solar cell according to a first embodiment of the present invention will be described with reference to FIGS. Note that the etching method according to the present embodiment is embodied by the method according to the present embodiment, and will be also described below.

In the manufacturing method according to this embodiment, first,
As shown in FIG. 1A, a semiconductor substrate 11 made of, for example, single crystal silicon having a normal (100) crystal plane is prepared. As single crystal silicon, for example, a p-type impurity such as boron is added at about 10 ¹⁹ atoms / cm ³ ,
Those having a specific resistance of about 0.02 Ω · cm are preferable. Note that the semiconductor substrate 11 corresponds to the "first substrate" of the present invention.

As the semiconductor substrate 11, from the viewpoint of forming a porous layer 12 (see FIG. 1D) thereon by anodization as described later, a substrate made of p-type single crystal silicon is used. However, depending on the condition setting, a material made of n-type single crystal silicon may be used.

Next, as shown in FIG. 1B, for example, an electrolytic solution (anodizing solution) is formed on the surface of the semiconductor substrate 11.
HF (hydrogen fluoride): C ₂ H ₅ OH (ethanol) = 1: 1 (volume ratio of 49% HF solution and 95% C ₂ H ₅ OH solution) 3m
By performing the first stage of anodization at a current density of about A / cm ² (eg, 1 mA / cm ² ) for several minutes to several tens minutes (eg, 8 minutes), for example, a porosity of about 1.7 μm is obtained. Low (for example, about 16%) low porosity porous layer 1
2a is formed. Thereafter, when the low-porosity porous layer 12a has a desired thickness, the energization is stopped.

The anodization method is a method in which a current is passed in a hydrofluoric acid solution using the semiconductor substrate 11 as an anode.
For example, Ito et al., "Surface Technology Vol.46.No.5.p8 ~ 13,199
5 [Anodic formation of porous silicon] ”. In this method, a semiconductor substrate 11 on which a porous layer is to be formed is arranged between two electrolytic solution tanks, and a platinum electrode connected to a DC power supply is installed in both electrolytic solution tanks. Then, the electrolytic solution is put into both the electrolytic solution tanks, and a DC voltage is applied to the platinum electrode to make the semiconductor substrate 11 an anode and the platinum electrode a cathode. Thereby, the semiconductor substrate 11
Is eroded and becomes porous. This anodization is preferably performed in a dark place. This is because when light is irradiated, a large number of random irregularities are formed on the surface of the porous layer, and the crystallinity of the epitaxial layer 13 described later deteriorates.

Next, as shown in FIG. 1 (C), for example, 3 to 20 mA / cm ² (eg, 7
The second anodization is performed at a current density of (mA / cm ² ) for several minutes to several tens minutes (for example, 8 minutes), and the thickness is about 6.3 μm and the porosity is medium (for example, about 26%).
The medium porosity porous layer 12b is formed. At this time, the medium porosity porous layer 12b is formed inside (lower side of the figure) the low porosity porous layer 12a, and the surface low porosity porous layer 12a formed by the first anodization is The porosity is kept as it is. After this, the medium porosity porous layer 12b
Is stopped when the desired thickness is reached.

Next, as shown in FIG. 1D, for example, 40 to 300 mA / cm ² (for example, 200 mA / cm 2)
² ) By performing the third step of anodization at a current density of several seconds (for example, 3 seconds), for example, a high porosity porous material having a thickness of about 0.05 μm and a large porosity (eg, about 60 to 70%) The layer 12c is formed. At this time, 90 mA / c
When anodization is performed at a current density of about m ² or more, the high porosity porous layer 12c is formed in the middle part in the thickness direction of the medium porosity porous layer 12b. Thereby, with a thickness of about 8 μm,
A porous layer 12 composed of three layers having different porosity is formed.

Next, hydrogen annealing is performed at a temperature (annealing temperature) in the range of, for example, 950 to 1150 ° C. (for example, 1030 ° C.) to close the holes existing on the surface of the porous layer 12. This hydrogen annealing is performed in a hydrogen (H ₂ ) atmosphere by, for example, raising the temperature from room temperature to an annealing temperature in about 20 minutes and then annealing for about 6 minutes. Thereby, the porous layer 12 is recrystallized, and the surface thereof has a smooth uneven shape. Further, also at the interface between the porous layer 12 and the semiconductor substrate 11, the fine holes in the porous layer 12 are recrystallized by thermal energy, and a plurality of holes are formed.

Next, as shown in FIG. 2A, for example, SiH ₄ (silane), B ₂ H ₆ (diborane) and PH are placed in a normal pressure epitaxial growth apparatus in a hydrogen gas atmosphere.
₃ Supplying a gas such as (phosphine)
The epitaxial layer 13 is grown on the low porosity porous layer 12a by epitaxial growth at a temperature of 0 ° C.
To form The thickness of this epitaxial layer 13 is about 1 to 50 μm when formed on a single crystal silicon substrate. The epitaxial layer 13 has a high concentration of p-type impurity such as boron (B) (1 × 10 ¹⁹ atom).
The p ⁺ -type layer 13a including the s / cm ³ or so) for about 3 minutes 1
After the growth of μm, a p-type impurity such as boron is added on the p ⁺ -type layer 13a by 1 × 10 ¹⁵ to 1 × 10 ¹⁸ atom.
s / cm ^{3 of} p ^- type layer 13b in about 10 minutes
The n ⁺ -type layer 13c containing a high concentration (about 1 × 10 ¹⁹ atoms / cm ³ ) of an n-type impurity such as phosphorus (P) is further formed on the p ⁻ -type layer 13b by 1.2 μm in about 4 minutes. Grow to a degree. With such a configuration, for electrons generated in the p-type layer 13b by the light is reflected at the p ⁺ -type layer 13a, recombination of electrons and holes in the p ⁺ -type layer 13a is reduced, energy conversion Become a highly efficient solar cell.
In addition, the epitaxial layer 13 is the “semiconductor layer” of the present invention.
It corresponds to.

In this embodiment, during the hydrogen annealing and the epitaxial growth, the silicon atoms in the porous layer 12 are moved and rearranged, so that the porosity of the high porosity porous layer 12c is further increased. As a result, the high porosity porous layer 12c becomes more brittle. Further, since the difference in porosity between the high porosity porous layer 12c and the medium porosity porous layer 12b is greatly different, a large strain is generated at these interfaces and near the interfaces, and the strength in the vicinity is extremely weakened. Thereby, the high porosity porous layer 12c becomes a layer having the lowest tensile strength, that is, a separation layer 12c '. However, separation layer 1
2c 'has a sufficient tensile strength that the epitaxial layer 13 does not peel off from the semiconductor substrate 11 partially or entirely during the formation of the solar cell element on the porous layer 12. I have. Further, the smooth irregularities on the surface of the porous layer 12 described above result in a plurality of round holes. Therefore, when the porous layer 12 is removed as described later, the boundary surface between the epitaxial layer 13 and the porous layer 12 has a texture structure. Note that the separation layer 12c '
Is the “separation layer” of the present invention and corresponds to the “layer to be etched”.

Next, as shown in FIG. 2B, for example, thermal oxidation is performed to form an oxide film 14 made of, for example, silicon oxide (SiO ₂ ) on the epitaxial layer 13. This oxide film 14 makes it possible to minimize the generation of electrons and holes (carriers) on the surface of the epitaxial layer 13 (that is, the surface of the n ⁺ -type layer 13c) and the recombination of electrons and holes. Things.

Subsequently, an opening for forming an electrode is formed in the oxide film 14, and a titanium (Ti) film having a thickness of 30 nm and a palladium (Pd) film having a thickness of 50 nm are formed on the oxide film 14 including the opening. After a silver (Ag) film having a thickness of 100 nm is sequentially formed by a vapor deposition method, a silver film having a thickness of 8 μm is formed by a plating method. Further, for example, thermal annealing is performed at 400 ° C. for 20 to 30 minutes to form a metal electrode (light receiving surface electrode) 15 made of a TiPdAg alloy. After that, the metal electrode 15 is etched so as to have a desired pattern.

After the solar cell element is formed in this way, as shown in FIG. 2C, a thickness of, for example, 4 μm is formed on each of the patterned metal electrodes 15 along the metal electrodes 15.
The conductive wires 16 made of 00 μm copper (Cu) are bonded respectively.

Next, as shown in FIG. 3A, a circular plastic film substrate 21 made of, for example, fluororesin, polycarbonate or polyethylene terephthalate is prepared.
The conductive wire 1 is placed on the front side (upper side of the figure) of the solar element.
6 and the adhesive layer 22. As a material forming the adhesive layer 22, for example, a material having high tensile strength such as ethylene vinyl acetate (EVA) is used. Note that the plastic film substrate 21 corresponds to the “second substrate” of the present invention.

Next, as shown in FIG. 3B, the solar cell element is separated from the semiconductor substrate 11 at the separation layer 12c 'together with the plastic film substrate 21, and the solar cell element is transferred to the plastic film substrate 21. At the time of peeling, for example, a method of applying a tensile stress between the plastic film substrate 21 and the semiconductor substrate 11, a method of immersing the semiconductor substrate 11 in a solution such as water or ethanol, and irradiating ultrasonic waves to separate the separation layer 12c ' Of the separation layer 12c 'by applying a centrifugal force to decrease the strength of the separation layer 12c', or a combination of the above three methods.

The semiconductor substrate 11 from which the solar cell element has been peeled off has a porous layer 12 remaining on the surface.
Is removed by a normal polishing method, electrolytic polishing, or silicon etching, it can be reused in the next manufacturing process of the solar cell element.

Next, as shown in FIG. 4A, the separation layer 12c 'attached to the epitaxial layer 13 side of the solar cell element is removed by using the etching apparatus 30. As shown in FIG. 5, the etching apparatus 30 is used for fixing an object to be etched such as the plastic film substrate 21 in a reaction vessel 31 made of a material having excellent durability against chemicals, for example, a fluororesin. A table 32 is provided. The fixed base 32 is provided at the upper end of the rotating shaft 33, and its surface is a horizontal plane. Rotating shaft 33
Is rotatably supported by a cylindrical bearing 31a provided at the bottom of the reaction vessel 31, and is connected to a rotation mechanism (not shown). That is, the rotating mechanism allows the fixed base 32 to be horizontally rotated at a predetermined speed together with the rotating shaft 33.

The fixing table 32 and the rotating shaft 33 are made of a material having excellent durability against chemicals, for example, a fluorine resin or vinyl chloride. These fixed bases 3
2 and the rotating shaft 33 are provided with hollow portions 32a communicating with each other. The cavity 32a communicates with a vacuum pump (not shown), and after the object to be etched is placed on the fixed base 32, the cavity 32a is moved by the vacuum pump.
The object to be etched is adsorbed on the fixed base 32 by evacuating the vacuum chamber a. That is, the object to be etched is horizontally rotated at a predetermined speed with the rotation of the fixed base 32. An opening 31 b is provided on the ceiling surface of the reaction vessel 31 so as to face the fixing table 32. A pipe 34 for supplying an etchant and a pipe 35 for supplying pure water are introduced into the reaction vessel 31 through the opening 31b, and the surface of the object to be etched adsorbed to the fixing table 32 from these pipes 34, 35. , An etching solution or pure water is supplied. The bottom surface of the reaction vessel 31 is provided with an opening 31c for guiding the liquid discharged from the pipes 34 and 35 to a recovery unit (not shown).

In this embodiment, the plastic film substrate 21 is placed on the fixing table 32, and the cavity 32a is evacuated to evacuate the plastic film substrate 21 to the fixing table 32.
To be absorbed. Thereafter, while the fixing table 32 is rotated at a speed of, for example, about 200 revolutions / minute, a mixed solution (etching solution) of hydrogen fluoride and nitric acid (HNO ₃ ) is dropped, for example, by two to three drops through the pipe 34. Thus, the liquid is supplied to the exposed surface of the porous layer 12. At this time, the etching solution is uniformly supplied to the entire exposed surface of the porous layer 12 by the centrifugal force generated by the rotation of the fixing table 32, and the porous layer 1
The second isolation layer 12c 'begins to be etched. If the rotation speed of the fixed base 32 is about 10 rotations / minute, the etchant on the porous layer 12 is discharged from the opening 31c,
The etchant does not flow to the plastic film substrate 21 side. As the etching solution, another acidic solution such as hydrogen fluoride or acetic acid (CH ₃ COOH) can be used instead of the above-mentioned mixed solution of hydrogen fluoride and nitric acid.

Next, after the separation layer 12c 'has begun to be etched and has been etched by a predetermined amount, FIG.
As shown in (B), the supply of the etchant is stopped, and pure water is supplied to the surface to be etched through the pipe 35. As a result, the surface to be etched is cleaned, and the chemical reaction by the etchant is stopped.

Here, the amount of etching can be adjusted by supplying pure water at a predetermined timing, so that etching is performed while leaving a part of the porous layer 12 (for example, one or two porous layers). It is possible to stop,
It is also possible to stop etching after removing part of the epitaxial layer 13. When the etching is stopped while leaving a part of the porous layer 12, the back surface of the solar cell element has a texture structure, which greatly contributes to light scattering. If the etching is stopped after removing part of the epitaxial layer 13, the porous layer 12 not directly involved in power generation is completely removed, and the energy conversion efficiency is increased.

Next, as shown in FIG. 6 (A), a silver paste is applied to the back side (lower side of the figure) of the epitaxial layer 13 so as to obtain an ohmic contact on the back side of the solar cell element. The layer 17 is formed. Subsequently, a back electrode 18 made of aluminum is formed on the ohmic contact layer 17 by, for example, a printing method. This back electrode 18
Has a function of protecting the back side of the solar cell element in addition to the function as an electrode.

Finally, as shown in FIG. 6B, a reflecting plate 23 made of, for example, metal or plastic and having an uneven surface is bonded to the back electrode 18 via an adhesive layer 24 made of, for example, ethylene vinyl acetate. Let it.

As described above, according to the present embodiment, the plastic film substrate 2
Since an appropriate amount of etchant is supplied while rotating 1 to etch the separation layer 12c 'of the porous layer 12, the etchant is uniformly supplied to the surface to be etched. Therefore, the separation layer 12c 'can be uniformly etched over the entire surface.

Further, since there is no possibility that the etching solution flows around the plastic film substrate 21, the contact between the plastic film substrate 21 and the etching solution can be effectively prevented. Therefore, it is not necessary to change the material of the transfer substrate (the plastic film substrate 21 in the present embodiment) according to the etchant. Further, it is possible to prevent the etchant from seeping into the inside from the porous layer 12 side.

Further, since the supply of the etchant is stopped and the supply of pure water is simultaneously stopped to stop the etching, the amount of etching of the porous layer 12 can be adjusted. Accordingly, there is no possibility that the active region of the solar cell is over-etched.

(Second Embodiment) The manufacturing method according to this embodiment is different from the manufacturing method according to the first embodiment in that an alkaline etching solution is used instead of the etching solution (acid solution). The other processes are the same as those in the first embodiment. Therefore, a detailed description thereof will be omitted here, and only different points will be described.

In this embodiment, when etching the porous layer 12, for example, a potassium hydroxide (KOH) solution at 70 ° C. is supplied as an etching solution through the pipe 34 of the etching device 30. In addition, instead of potassium hydroxide, sodium hydroxide (N
Other alkaline solutions such as an (aOH) solution and a 60% hydrazine (N ₂ H ₄ ) solution can also be used.

When the potassium hydroxide solution is supplied to the exposed surface of the porous layer 12, the convex part of the porous layer 12 keeps its shape, becomes flat in some places, and becomes (100) crystal. The exposed part is (11
1) Anisotropic etching is performed so that a crystal plane appears. This is because the (100) crystal plane and the (111) crystal plane have different etching rates. Thereby, irregularities having a V-shaped cross section are formed on the entire surface to be etched.

Also in this embodiment, the separation layer 12c '
After the etching of a predetermined amount has been started after the start of the etching, the supply of the etching liquid is stopped and the piping 3 is stopped.
For example, pure water is supplied to the surface to be etched through 5.

As described above, according to the present embodiment, since the potassium hydroxide solution is used as the etching solution, it is possible to perform etching without using an etching mask so that the surface to be etched has some irregularities. Can be.
That is, a texture is formed on the back surface side of the solar cell element, and light transmitted through the solar cell element can be irregularly reflected. Therefore, the amount of light incident on the solar cell element can be increased.

(Third Embodiment) In the manufacturing method according to the present embodiment, when etching the porous layer 12, first, for example, a mixed solution of hydrogen fluoride and nitric acid or hydrogen fluoride is etched. As a liquid, 80 to 90% of the thickness of the porous layer 12 is etched from the upper side. Thereafter, the supply of the etching liquid is stopped, and pure water is supplied onto the surface to be etched. Next, after etching to a desired portion described above using, for example, a potassium hydroxide solution as an etchant, the supply of the etchant is similarly stopped and, for example, pure water is supplied onto the surface to be etched. Other processes are the same as those of the first embodiment.

According to the present embodiment, etching is performed at a relatively high speed by using a mixed solution of hydrogen fluoride and nitric acid or hydrogen fluoride as an etching solution, and then etched using a potassium hydroxide solution as an etching solution. Finish etching for making the surface a texture structure can be performed. Further, as described above, the etching apparatus 3 shown in FIG.
Since the porous layer 12 is etched by supplying an appropriate amount of an etching solution while rotating while using 0, there is no possibility that the etching solution goes around the plastic film substrate 21 side. Therefore, even if both the acidic solution and the alkaline solution are used as the etching solution, the plastic film substrate 21 does not corrode.

Although the present invention has been described with reference to the embodiment, the present invention is not limited to the above embodiment, and can be variously modified. For example, in the above-described embodiment, a method in which the plastic film substrate 21 is fixed to the fixing table 32 by vacuum suction is described as the etching apparatus 30. However, the etching apparatus 30 may be fixed by another method other than vacuum suction. For example, as shown in FIG. 7, a plurality of fixing parts 42 a may be arranged on the fixing stand 42 so as to be separated from each other, and the plastic film substrate 21 may be fixed to the fixing stand 42 by these fixing parts 42 a.

In the above-described embodiment, the case of epitaxial growth on a silicon substrate has been described. At least one and arsenic (A
s) or a semiconductor substrate 11 made of a group III-V compound semiconductor containing at least one of nitrogen (N) and the like.
The epitaxial layer 13 is epitaxially grown on the
Can also be formed.

In the above-described embodiment, the circular plastic film substrate 21 has been described as an example. However, the shape of the plastic film substrate 21 may be polygonal or polygonal with rounded corners. .

In the case of manufacturing an integrated solar cell having a plurality of solar cell elements, after forming the plurality of solar cell elements, before the porous layer 12 of each of the above embodiments is etched, the separation is performed. A groove may be formed to separate each solar cell element, and a damaged portion generated during the formation of the separation groove may be etched simultaneously with the porous layer 12 by the above method.

In the above embodiment, the case where the reflector 23 is provided on the back surface side of the solar cell element has been described. However, instead of the reflector 23, a plastic film having a reflective film is provided. You may.

In the above embodiment, 3 to 20 mA
/ Cm ^{2 at} a current density of several minutes to several tens of minutes to form the middle porosity porous layer 12b by performing the second-stage anodization. The medium porosity porous layer 12b has a high current density. It may be formed by performing anodization stepwise or gradually. Thereby, the medium porosity porous layer 12b
Has a gradual or gradient increase from the upper surface side to the lower surface side. Therefore, the strain between the separation layer 12c 'and the low porosity porous layer 12a is further alleviated, and the epitaxial layer 13 having excellent crystallinity can be formed.

Further, in the above embodiment, 40 to 300
The high-porosity porous layer 12c was formed by performing the third-stage anodization at a current density of mA / cm ² for several seconds, but the high-porosity porous layer 12c was intermittently formed under appropriate conditions. It may be formed by performing anodization while passing a current. In that case, the high porosity porous layer 12c is
2 is formed on the lowermost surface. That is, the high porosity porous layer 12c and the low porosity porous layer 12a are formed with maximum separation. Thereby, the buffer effect by the medium porosity porous layer 12b is maximized, and the epitaxial layer 13 having excellent crystallinity can be formed. Further, since the medium porosity porous layer 12b is formed only between the high porosity porous layer 12c and the low porosity porous layer 12a, the overall thickness of the porous layer 12 is reduced. Accordingly, the consumption thickness of the semiconductor substrate 11 for forming the porous layer 12 can be reduced. Therefore, the semiconductor substrate 11
Can be increased repeatedly.

In the above embodiments, a solar cell has been described as an example of a semiconductor device. However, the present invention relates to a semiconductor device having other elements such as a light receiving element or a light emitting element, a liquid crystal display element, and an integrated circuit element. It is also widely applied to devices. Further, the semiconductor layer (epitaxial layer 13 in each of the above embodiments) is not limited to a single crystal, but may be made of any of polycrystal and amorphous, or a composite film thereof.

[0055]

As described above, according to the etching method of the first aspect, the etching liquid is supplied to the surface of the layer to be etched while rotating the layer to be etched together with the substrate. Etching is performed uniformly over the entire surface.

Further, the amount of etching of the layer to be etched is adjusted by stopping the chemical reaction by the etchant at a predetermined timing, so that the occurrence of overetching on the semiconductor layer underlying the layer to be etched is suppressed. can do.

Further, according to the method of manufacturing a semiconductor device according to any one of claims 2 to 13, the separation as a layer to be etched, which adheres to the semiconductor layer transferred to the second substrate side. Since the etching solution is supplied only to the layer, the second substrate does not come into contact with the etching solution, and the necessity of changing the material of the second substrate according to the etching solution is eliminated.

In particular, according to the method of manufacturing a semiconductor device according to the third aspect of the present invention, after the etching solution is supplied to the surface of the remaining portion of the separation layer, the chemical reaction by the etching solution is stopped at a predetermined timing. Since the amount is adjusted, occurrence of over-etching in the semiconductor layer can be suppressed.

Further, claim 4, claim 8, or claim 9
According to the method for manufacturing a semiconductor device according to any one of the above, while rotating the second substrate to which the semiconductor layer has been transferred,
Since the etching liquid is supplied to the surface of the remaining separation layer, the etching liquid is uniformly supplied to the entire surface of the separation layer by centrifugal force. Therefore, the separation layer can be uniformly etched.

In addition, according to the semiconductor device of the fourteenth aspect, since the semiconductor device is manufactured by the manufacturing method of the present invention, unnecessary portions of the separation layer are uniformly removed.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a manufacturing process of a solar cell according to a first embodiment of the present invention.

FIG. 2 is a cross-sectional view for explaining a manufacturing step following FIG. 1;

FIG. 3 is a cross-sectional view for explaining a manufacturing step following FIG. 2;

FIG. 4 is a cross-sectional view for explaining a manufacturing step following FIG. 3;

FIG. 5 is a perspective view showing a partially sectioned etching apparatus used in the manufacturing process of FIG. 4;

FIG. 6 is a cross-sectional view for explaining a manufacturing step following FIG. 4;

FIG. 7 is a perspective view for explaining another configuration of the etching apparatus used in the manufacturing process of FIG. 4;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 11 ... Semiconductor substrate, 12 ... Porous layer, 12c '... Separation layer, 13 ... Epitaxial layer, 14 ... Oxide film, 15 ... Metal electrode, 16 ... Conductive wire, 17 ... Ohmic contact layer, 18 ... Back electrode, 21 ... Plastic film substrates, 22, 24 ... Adhesive layers, 23 ... Reflectors, 30 ... Etching equipment, 31 ... Reaction vessels, 32,42 ... Fixed tables, 32
a ... hollow part, 33 ... rotating shaft, 34, 35 ... piping, 42a
…Fixed part

Claims (14)

[Claims] An etching method for selectively removing a layer to be etched present in contact with a semiconductor layer provided on a substrate, wherein the substrate is fixed to rotatable substrate fixing means, and An etching method comprising: supplying an etching solution to the layer to be etched while rotating the substrate; and stopping a chemical reaction by the etching solution at a predetermined timing, thereby adjusting an etching amount of the layer to be etched. A step of forming a semiconductor layer on a first substrate via a separation layer; and a step of peeling the semiconductor layer from the first substrate at the separation layer to form the semiconductor layer on a second substrate. Transferring, and removing the remaining portion of the separation layer by supplying an etchant to the surface of the separation layer attached to the semiconductor layer transferred to the second substrate side. A method for manufacturing a semiconductor device. 3. An etching solution is supplied to the surface of the remaining portion of the separation layer, and after stopping the chemical reaction by the etching solution at a predetermined timing, the amount of etching of the remaining portion of the separation layer is adjusted. 3. The method for manufacturing a semiconductor device according to claim 2, wherein: 4. The method according to claim 2, wherein said second substrate is fixed to a rotatable substrate fixing means, and an etchant is supplied to a surface of said separation layer while rotating said second substrate. The manufacturing method of the semiconductor device described in the above. 5. The method according to claim 2, wherein a porous layer is formed as the separation layer. 6. An etching solution comprising hydrogen fluoride (HF), a mixed solution of hydrogen fluoride and nitric acid (HNO ₃ ),
Acetic acid (CH ₃ COOH), potassium hydroxide (KOH),
Sodium hydroxide (NaOH) or hydrazine (N ₂
3. The method according to claim 2, wherein at least one of H ₄ ) is used. 7. The method according to claim 2, wherein a solar cell element, an integrated circuit element, or a light emitting element is formed in the semiconductor layer. 8. The method of manufacturing a semiconductor device according to claim 4, wherein said substrate fixing means vacuum-adsorbs the second substrate on which the semiconductor layer has been transferred onto a mounting table. 9. The apparatus according to claim 4, wherein said substrate fixing means fixes the second substrate to which the semiconductor layer has been transferred by the fixing part on a mounting table having a fixing part. The manufacturing method of the semiconductor device described in the above. 10. The method according to claim 1, wherein the first substrate is silicon (S).
i) a semiconductor containing at least one of germanium (Ge), or at least one of gallium (Ga) and indium (In) and arsenic (As)
Or II containing at least one of nitrogen (N)
3. The method according to claim 2, wherein an IV group compound semiconductor is used. 11. The method according to claim 1, wherein the semiconductor layer is silicon (S).
i) a semiconductor containing at least one of germanium (Ge), or at least one of gallium (Ga) or indium (In) and arsenic (As)
Or II containing at least one of nitrogen (N)
The method for manufacturing a semiconductor device according to claim 10, wherein an IV group compound semiconductor is formed. 12. The method according to claim 2, wherein the first substrate has a polygonal shape, a polygonal shape having rounded corners, or a circular shape. 13. The method for manufacturing a semiconductor device according to claim 7, further comprising a step of disposing a reflector on the side of said semiconductor layer opposite to said second substrate. 14. A semiconductor device manufactured by forming a semiconductor layer on a first substrate via a separation layer, and peeling the semiconductor layer from the first substrate in the separation layer and transferring the semiconductor layer to a second substrate. A semiconductor device, wherein after the semiconductor layer is transferred to a second substrate, an etchant is selectively supplied to a surface of the separation layer attached to the second substrate, and the remaining separation layer is removed. A semiconductor device, wherein at least a part of a part is removed.