JP3194612B2 - Method for manufacturing semiconductor element and bonded substrate - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device on an insulating substrate, and more particularly, to a high-performance semiconductor device formed on a single-crystal semiconductor layer on a light-transmitting insulating substrate such as glass.
Performance electronic devices, in which relates to a manufacturing method and a bonded substrate of a semiconductor device suitable for use in an integrated circuit.

[0002]

2. Description of the Related Art The formation of a single-crystal silicon semiconductor layer on an insulator substrate is widely known as Silicon on Insulator (SOI) technology, and involves a number of processes that cannot be achieved with a bulk silicon substrate for fabricating a normal silicon integrated circuit. Due to the advantages of this substrate, much research has been done. That is, by using the SOI technology, 1. Easy dielectric separation and high integration. 2. Excellent radiation resistance.
3. Higher speed due to reduced stray capacitance. 4. Well step can be omitted. 5. Latch-up can be prevented. Advantages such as the possibility of a fully depleted field-effect transistor by thinning can be obtained. In order to realize many of the above advantages in device characteristics, various studies have been made on a method of forming an SOI structure in recent decades. This content is, for example, Special Issue: “Single-crystal sil
icon on non-single-crystal insulators ”; edited by
GWCullen, Journal of Crystal Growth, volume 63, no
3, pp. 429-590 (1983).

[0003] Among many SOI technologies, as an example in which a silicon layer is a single crystal and research has been advanced to a level where a certain degree of integrated circuit can be formed, a single crystal sapphire has been used in the past to deposit a silicon film on a substrate by CVD. (Silicon on Sapp) formed by heteroepitaxy using (chemical vapor deposition)
hire) is known and has achieved some success as the most mature SOI technology. However, in this technique, a large amount of crystal defects are generated due to lattice mismatch between the silicon layer and the underlying sapphire substrate interface, aluminum is mixed into the silicon layer from the sapphire substrate, and above all, the substrate is expensive and large The spread of its applications has been hindered, for example, due to delays in responding to the development of the technology.

In recent years, attempts have been made to realize an SOI structure based on a silicon substrate without using a sapphire substrate. For example, ZMR, SIMO
X, bonded SOI, and the like.

[0005] ZMR (Zone Melting Recrystallization)
An opening is formed in a part of a single-crystal silicon substrate covered with a SiO ₂ film, and an amorphous or polycrystalline silicon layer deposited thereon is focused and irradiated with an energy beam such as an electron beam or a laser beam. Then, a single-crystal silicon layer is grown on SiO ₂ by melt recrystallization using the single-crystal substrate surface of the opening as a seed, or the molten region is scanned in a strip shape by a rod-shaped heater. In this method, although a relatively large-scale integrated circuit is prototyped, a large number of crystal defects such as sub-grain boundaries still remain, and a small number of carrier devices have not been produced. In addition, there are many problems in terms of controllability, productivity, and the like.

On the other hand, SIMOX (Seperation by Ion Impla)
nted Oxygen) is a method of forming a SiO ₂ layer by ion implantation of oxygen into a silicon single crystal substrate. This technology is currently the most mature method due to its good compatibility with silicon processes. However, in order to form a SiO ₂ layer, oxygen ions must be implanted at 10 ¹⁸ ions / cm ² or more, but the implantation time is long, productivity cannot be said to be high, and wafer cost is high. . Furthermore, many crystal defects remain, and industrially, minority carriers
Insufficient quality to produce devices.

[0007] A bonded SOI means that two substrates having an insulating film such as SiO ₂ on at least one of them are bonded to each other with mirror surfaces, and after heat treatment, one of the substrates is polished to form a film on the insulating film. Is to leave a thin film.
In this case, the precision of polishing is particularly problematic. In general, a single crystal substrate having a thickness of several hundreds of μm can be uniformly formed in a plane by several μm.
Alternatively, it is extremely difficult to polish to 1 μm or less. Also, the two substrates to be bonded may be silicon substrates, but if one of them is a substrate of a different material such as glass, the substrate may be broken or peeled off due to a difference in thermal expansion coefficient between the two when heat-treated. Will happen.

The SOI structure described above is a technique developed for the purpose of manufacturing a high-performance device as described above. On the other hand, a single-crystal silicon thin film is formed on a transparent insulator substrate. Attempts have been made to make the device itself functional in addition to increasing its performance by fabricating the device above.

It is impossible to form a silicon single crystal thin film on a transparent insulating substrate such as glass by SIMOX or ZMR which depends on the silicon substrate itself as described above (impossible by ZMR without seed). However, it is difficult to control the orientation and single crystal fiber), but the only possibility is the bonded SOI. However, as described above, the thickness of the bonded SOI is several hundred μm.
It is extremely difficult to bond two different dissimilar material substrates to each other due to a difference in thermal expansion coefficient between the substrates. Therefore, from the viewpoint that there is no problem unless heat treatment is performed even if the coefficient of thermal expansion is different, after forming an element on a silicon substrate by a normal process, the substrate itself is polished from the back surface of the silicon substrate to form the element. A technique has been published in which only the surface layer is left, and this thin film is attached to a transparent substrate using a transparent resinous adhesive (K. Sumiyoshi et.al, 1989).
IEDM attended paper: technical digest pl65).

However, in this method, when thinning, selective polishing using a silicon oxide film as a stopper is used. As described above, the polishing technique has a problem in accuracy, and as described in the above-mentioned paper, the polishing rate ratio between silicon and a silicon oxide film is only about 100 times. Therefore, it can be said that it is very difficult to produce a uniform thin film by polishing without a thickness distribution. Similarly, in the case of selective etching utilizing the impurity concentration difference in the silicon substrate instead of polishing, a sufficient selection ratio cannot be obtained.

[0011]

As described above, a technique capable of providing an SOI substrate sufficient for producing a high-performance electronic device with high productivity by the conventional method has not yet been achieved. Further, there is a problem that the SOI structure is formed on a transparent substrate and the substrate itself is provided with functionality, such that the technical development is further delayed.

(Object of the Invention) In order to solve the above-mentioned problems, the present invention provides a method for manufacturing a semiconductor device on an insulating substrate such as a transparent insulating substrate.
By forming a silicon single crystal thin film having a significantly different coefficient of thermal expansion from a substrate by a bonding method, it is possible to manufacture a high-performance SOI substrate, and when manufacturing a large-scale integrated circuit, an expensive SOS, It is an object of the present invention to provide a high-performance semiconductor substrate that can be used as a substitute for SIMOX, and a method for manufacturing a semiconductor element that can simultaneously manufacture the same.

[0013]

According to the method of manufacturing a semiconductor device of the present invention, as a means for solving the above-mentioned problems,
A step of making the entire silicon single crystal substrate porous by anodizing, a step of epitaxially growing a silicon single crystal thin film on one surface of the porous layer, a step of forming an element on the epitaxial layer, and a step of forming the element Bonding a surface to an arbitrary supporting substrate via wax or a thermoplastic resin, removing a porous silicon portion, and forming an epitaxial layer on which the element is formed on a transparent insulating substrate containing SiO ₂ as a main component. And a step of separating the support substrate and the epitaxial layer on which the element is formed by melting or softening the wax or the thermoplastic resin.

Further, a method for manufacturing a semiconductor device according to the present invention comprises:
A step of making the surface layer on one surface of the silicon single crystal substrate porous by anodizing, a step of epitaxially growing a silicon single crystal thin film on the porous surface, and a step of forming an element on the epitaxial layer, a step of bonding through a the element forming surface optional support substrate and the wax or thermoplastic resin, and removing the porous silicon portion after removing by polishing the silicon single crystal substrate portion, wherein the element is formed The grown epitaxial layer is made of SiO ₂
Bonding a transparent insulating substrate having a main component with an adhesive, and a step of melting or softening the wax or thermoplastic resin to separate the support substrate and the epitaxial layer on which the element is formed. , As the means.

Further, a method for manufacturing a semiconductor device according to the present invention
A step of providing a barrier layer for preventing diffusion of mobile ions between the epitaxial layer on which the element is formed and the adhesive.

Further, a method for manufacturing a semiconductor device according to the present invention comprises:
The removal of the porous silicon portion, have rows hydrofluoric acid, hydrogen peroxide, a mixed etching solution of alcohol, further
In addition, the method for manufacturing a semiconductor element of the present invention includes the steps of:
Silicon single crystal thin film on porous substrate with porous silicon layer
Providing a substrate having a film;
A step of forming an element on the film, and optionally supporting the element formation surface
Laminated with substrate via wax or thermoplastic resin
And removing the porous silicon layer.
The silicon single crystal thin film with the element
Bonding the board with an adhesive, and the wax or heat
The above-mentioned support is achieved by melting or softening a plastic resin.
Separates the substrate and the silicon single crystal thin film on which the device is formed
And the step of performing
Between the formed silicon single crystal thin film and the adhesive,
Including the step of providing a barrier layer to prevent diffusion of mobile ions.
Mukoto is also a method for manufacturing a semiconductor device characterized, or
Further, the other insulating substrate is made of a transparent material mainly composed of SiO _2.
Method for manufacturing semiconductor element characterized by being an insulating substrate
Method, and a silicon single bond on which the element is formed.
Crystal thin film and another insulating substrate without the adhesive
In the method of manufacturing a semiconductor element characterized by
There, the present invention also silicon porous silicon layer
A substrate having a single crystal thin film is prepared, and the silicon single crystal thin film is prepared.
Forming an element on the film, the element forming surface with any support substrate,
Make sure that they are bonded together via wax or thermoplastic resin.
It is also a characteristic bonded substrate.

[0017]

The present invention utilizes two important physical properties of porous silicon. One of them is the etching characteristics of porous silicon. Normally, silicon is hardly etched by hydrofluoric acid, but it can be etched by making it porous. In addition, as shown in FIG. 4, when a mixed etching solution of hydrofluoric acid, hydrogen peroxide solution, and alcohol is used, an etching rate ratio of about 10 times as high as that of nonporous and porous can be obtained. Therefore, even with a thin film of about 1 μm, selective etching can be uniformly performed with good controllability.

Another characteristic is an epitaxial growth characteristic. Porous silicon has a single crystal structure as a crystal structure, and has pores of several tens to several hundreds of angstroms at high density from the surface to the inside. The epitaxial layer grown on this surface has the property that the same crystallinity as the epitaxial layer on the non-porous single crystal substrate can be obtained. Therefore, since a single crystal thin film equivalent to an epitaxial layer on a single crystal silicon substrate having high reliability is used as an active layer, an SOI substrate having better crystallinity than a conventional SOI substrate can be provided.

According to the present invention, an element is formed on a single crystal layer epitaxially grown on porous silicon, the single crystal layer on which the element is formed is held on a supporting substrate with wax or the like, and the porous portion is selectively etched. The single crystal layer on which the element was formed was formed into a single thin film (membrane), and this was bonded to a transparent insulating substrate using an adhesive, and the supporting substrate was separated with wax or the like. A high-performance and highly functional electronic device can be easily manufactured.

Further, since the thickness distribution of the epitaxial growth layer can be easily controlled, an extremely uniform thickness distribution of the SOI layer using this growth layer as it is can be obtained.

Further, since the etching rate ratio between porous silicon and non-porous silicon is extremely large, the controllability of etching is dramatically improved as compared with the conventional selective polishing or removal by selective etching utilizing a difference in impurity concentration. I do.

Further, a silicon single crystal thin film device on a transparent insulating substrate, which has been extremely difficult to realize due to a difference in thermal expansion coefficient, can be easily manufactured.

Further, by providing a barrier layer for preventing diffusion of mobile ions between the epitaxial layer on which the element is formed and the adhesive, the epitaxial layer is formed by mobile ions from the adhesive for bonding the transparent insulating substrate. It is possible to prevent the layer from adversely affecting the element formation layer.

(Embodiments) Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic cross-sectional view for explaining the process flow of the method for manufacturing a semiconductor device of the present invention.

First, as shown in FIG. 1-1, a single crystal silicon substrate 100 is anodized to form porous silicon 101. At this time, the region to be made porous may be only one surface layer of the substrate as shown in FIG. 1-1a or the whole substrate as shown in FIG. 1-1b. When only one surface layer is made porous, the region may have a thickness of 10 to 100 μm.

Here, the method for forming porous silicon will be briefly described with reference to FIG. 2 which is an explanatory view of an apparatus for making a silicon substrate porous.

First, a P-type single crystal silicon substrate 200 is prepared as a substrate. Although it is not impossible even with an N-type, in that case, the substrate is limited to a low-resistance substrate. The substrate 200 is shown in FIG.
Set in the device as shown. That is, one side of the substrate is in contact with the hydrofluoric acid-based solution 204, the negative electrode 206 is provided on the solution side, and the other side is in contact with the positive metal electrode 205.

FIG. 2-2 is a view showing an apparatus having another configuration example. As shown in FIG.
An electric potential may be taken via 04 '. In any case, porosity occurs from the negative electrode side in contact with the hydrofluoric acid-based solution.

As the hydrofluoric acid solution 204, concentrated hydrofluoric acid (49% HF) is generally used. It is not preferable to dilute with pure water (H ₂ O), since etching occurs at a certain concentration, depending on the value of the flowing current.

In addition, bubbles are generated from the surface of the substrate 200 during anodization, and alcohol may be added as a surfactant for the purpose of efficiently removing the bubbles. As the alcohol, methanol, ethanol, propanol, isopropanol and the like are used. Alternatively, anodizing may be performed while stirring the solution using a stirrer instead of the surfactant.

For the negative electrode 206, a material that is not eroded by a hydrofluoric acid solution, for example, gold (Au), platinum (Pt), or the like is used.

The material of the positive electrode 205 may be a commonly used metal material, but when the anodization is performed on all the substrates 200, the hydrofluoric acid-based solution 204 is
Therefore, the surface of the positive electrode 205 may be coated with a hydrofluoric acid solution-resistant metal film.

The current value for performing anodization is a maximum of several hundred mA /
cm ² and the minimum value must be zero. This value is determined within a range where good quality epitaxial growth can be performed on the surface of the porous silicon. Usually, when the current value is large, the rate of anodization increases, and at the same time, the density of the porous silicon layer decreases. That is, the volume occupied by the holes increases.
This changes the conditions for epitaxial growth.

Next, in the step shown in FIG. 1-2, a non-porous single-crystal silicon layer 10 is formed on the porous silicon substrate or porous layer 101 formed as described above.
2 is epitaxially grown.

Porous silicon has a single crystal structure as its crystal structure, and tens to hundreds of angstroms of pores are present at high density from the surface to the inside. The epitaxial layer grown on the surface has the property of obtaining highly reliable crystallinity equivalent to that of an epitaxial layer on a non-porous single crystal substrate. This is performed by CVD, molecular beam epitaxy, sputtering, or the like. The growing film thickness is S
The value may be the same as the design value of the OI layer, but is preferably 1 μm.
m or less is good. This is because visible light does not pass through single crystal silicon having a thickness of 1 μm or more. However, the thickness is not particularly limited in the case where a portion other than the element formation region is etched after the SOI substrate is manufactured, or in the case of a device in which light transmittance is not emphasized.

Next, in a step shown in FIG. 1-3, an element 109 is formed on the epitaxial layer 102 by a normal device process. There is no limitation on the type, form, etc. of the element.

Next, in the step shown in FIG. 1-4, the element formation surface 109 is heated while heating the substrate to an appropriate temperature.
A wax or a thermoplastic resin 103 on the support substrate 1
11 is adhered.

The wax is solidified at room temperature,
It is preferable to use a material that softens when heated back and forth. The thermoplastic resin may be applied in a liquid state and polymerized on a wafer, but a sheet-like resin is also convenient. Preferably, these are dissolved in an organic solvent such as acetone and toluene. For example, as wax, electron wax, etc., and as resin materials, phenol-based, melamine-based, polyfluorinated ethylene-based materials, etc. are mentioned as high softening point materials,
Examples of low softening point materials include a mixture of vinyl chloride and vinyl acetate and a polystyrene. The support substrate 111 may be of any shape, size (thickness), material, and the like. For example, when silicon (which may be single crystal or polycrystal) is used as a support substrate material, one support substrate can be used semipermanently.

Next, in the step shown in FIG. 1-5, the porous silicon side is selectively etched except for the support substrate 111 and the element formation layer. In this case, as a characteristic of porous silicon, silicon is usually hardly etched by hydrofluoric acid, but it can be etched by making it porous.

Further, as shown in the graph of FIG. 4 showing the etching rate ratio between porous silicon and non-porous silicon, when a mixed etching solution of hydrofluoric acid, aqueous hydrogen peroxide and alcohol is used, non-porous and porous With high quality silicon, an etching rate ratio as high as 10 5 times can be obtained. Therefore, even when the single crystal layer is as thin as about 1 μm, selective etching can be performed uniformly and with good controllability.

If the portion to be etched at this time is entirely porous, the whole of the porous portion 101 is selectively etched by dipping the bonded substrate together with a hydrofluoric acid-based solution. In the case where the portion to be etched includes a region where the single crystal silicon substrate 100 remains, it is preferable to remove only the region of the silicon substrate 100 by polishing. Polishing is finished when the porous portion 101 is exposed, and thereafter, selective etching can be performed in a hydrofluoric acid-based solution. In any case, the non-porous single crystal epitaxially grown portion 102 hardly reacts with hydrofluoric acid and remains as a thin film.

As a matter of course, the supporting substrate 111
It is preferable to use a material that does not easily react with the hydrofluoric acid-based solution. At this time, the hydrofluoric acid-based solution is a mixture of hydrogen peroxide (H ₂ O ₂ ) and alcohols in addition to hydrofluoric acid. Selective etching of porous silicon is possible with hydrofluoric acid and nitric acid, or a mixed solution of acetic acid and acetic acid, but in this case, the remaining single crystal silicon thin film is also etched somewhat, so it is necessary to precisely control the time etc. There is.

Next, in the step shown in FIG. 1-6, the element formation layer and the transparent substrate are then bonded using an adhesive. At this time, mobile ions from the adhesive adversely affect the element formation layer. May have an effect. Therefore, when the back surface of the element formation layer is exposed, the barrier layer 107 such as a silicon nitride film is preferably deposited on the back surface of the element formation layer. The silicon nitride film is usually deposited by LPCVD, plasma CVD, or the like. However, the temperature must be high enough to withstand the wax or thermoplastic resin bonded to the supporting substrate.
It is preferable to deposit in the range of 300 ° C. The thickness of the barrier layer 107 is preferably thinner in consideration of light transmittance. The barrier layer 107 is not necessarily required,
It may be omitted if the content of impurities that adversely affect the element is small.

Next, in the step shown in FIG. 1-7, the back surface of the exposed element formation surface 109 or the barrier formed on the exposed surface is formed by using an adhesive 108 which becomes transparent when solidified. The surface of the layer 107 is brought into close contact with a transparent insulating substrate 110 containing SiO ₂ as a main component. The transparent insulating substrate 110 is selected from fused quartz, synthetic quartz, glass, synthetic resin, and the like. The adhesive 108 is preferably a resin-based adhesive having a small content of mobile ions as much as possible.

After the contact, the entire substrate is heated to soften the wax or the thermoplastic resin 103 and separate the support substrate 111. After separating the support substrate 111, the element forming surface 1
09 is sufficiently washed with an organic solvent such as acetone, dichloromethane, toluene, or the like, or if it cannot be completely removed only by washing, plasma ashing or the like is performed to remove SOI on the transparent insulating substrate. Obtain an element with a structure.

In the present invention, the element forming layer 102 is
Although the substrate is bonded to the transparent substrate 110 in step 8, it is not impossible to bond the substrate and the element formation layer without using an adhesive. In other words, the interface between the back surface of the element forming layer 102 (the side on which no element is formed) and the transparent insulating substrate 110 is handled in the same manner as a normal silicon substrate, even if they are simply brought into close contact, unless an external stress is applied. Is possible. This is due to hydrogen bonding at the interface between the substrate 110 and the thin film 102. Since the hydrogen bond is an intermolecular bond, it becomes stronger as the adhesion at the interface is higher, that is, as the flatness between the substrate and the thin film is higher.
Therefore, in order to enhance the adhesion between the substrate and the thin film, it is also effective to apply a uniform pressure with a weight or the like from above the substrate.

Since the hydrogen bond is an attractive force between a hydrogen atom (-H) and an oxygen atom (-O-) at an interface where the device is formed, the cleaning is performed before the device forming layer 102 and the transparent insulating substrate 110 are brought into close contact with each other. By applying a surface treatment so that hydrogen bonding can be easily performed in the final step, the bonding strength can be considerably increased. However, the hydrogen bond is not so strong, so that when a stress is applied, the element formation layer is immediately separated.
Therefore, it is also conceivable to heat-treat those that are in close contact by hydrogen bonding to increase the bonding force.

In general, the higher the temperature of the heat treatment, the stronger the bonding force at the interface. When the temperature rises to about 200 ° C. or higher, both hydrogen and oxygen atoms that have undergone hydrogen bonding are dehydrated in the form of H ₂ O, and then condensed silanol bonds (Si
-O-Si). However, in the process of the present invention, since the element is formed first, it is difficult to finally perform the heat treatment at 400 ° C. or more, because the element is destroyed. Therefore, heat treatment up to about 300 ° C. is permitted. When the heat treatment is performed at about 300 ° C., the bonding force is slightly increased compared to the hydrogen bonding, so that the method is limited to a method in which no external stress is applied when no adhesive is used.

[0050]

Embodiment 1 (Embodiment 1) Details of a specific first embodiment of the present invention will be described in the order of steps in the drawings with reference to FIGS.

In the step shown in FIG.
A 4-inch P-type (100) single-crystal silicon substrate (0.1-0.2 Ωcm) 100 having a thickness of microns is prepared, and set in an apparatus as shown in FIG. 2-1 to perform anodization. , Porous silicon 10 as shown in FIG.
1 was obtained. The solution 204 used at this time was a 49% HF solution, and the current density was 100 mA / cm ² . At this time, the rate of making porous is 8.4 μm / min. And 2
The entire P-type (100) silicon substrate having a thickness of 00 μm was made porous in 24 minutes.

Next, in the step shown in FIG.
A single-crystal silicon layer 102 was epitaxially grown on the mold (100) porous silicon substrate 101 by 0.5 μm by CVD. The deposition conditions are as follows.

Gas used: SiH ₄ / H ₂ gas flow rate: 0.62 / 140 (1 / min) Temperature: 750 ° C. Pressure: 80 Torr Growth rate: 0.12 μm / min. Next, in the step shown in FIG. 1-3, a switching transistor for a liquid crystal display device was formed in the epitaxial layer, and a pixel driving circuit was formed around the switching transistor using a normal semiconductor process.

Next, in a step shown in FIG. 1-4, while heating the substrate on which the elements are formed on a hot plate, electron wax 103 is applied on the element forming surface 109, and a 4-inch silicon support substrate 111 is formed. Was bonded to the element formation surface 109.

Next, in the step shown in FIG. 1-5, the bonded substrate was immersed in a selective etching solution, and only the porous portion 101 was selectively etched. At this time, the composition of the etching solution and the etching rate for the porous silicon were as follows: HF: H ₂ O ₂ : C ₂ H ₅ OH = 5: 25: 6 1.6 μm / min. Met. Thus, a 200 μm porous section is about 125
Everything was etched in minutes. Incidentally, the etching rate of the single crystal silicon layer 102 at this time is 0.0006 μm.
m / hour and remained almost without being etched.

Next, in the step shown in FIG. 1-7, the sample obtained in the above step was washed with a mixed solution of hydrochloric acid / hydrogen peroxide / water (1: 1: 5) for 10 minutes, and further purified. After rinsing with water and drying, a 4 inch glass substrate (thickness: 400 μm) 110 which had been subjected to the same cleaning and the single crystal silicon layer 102 were bonded to each other using a polyimide resin adhesive 108. Place the bonded substrate on a hot plate for approx.
When the wax 103 was heated to 50 ° C. and the wax 103 was softened, the support substrate 111 was removed.

In order to completely remove the wax remaining on the surface of the element forming surface 109, the above substrate was washed with toluene, and an SOI substrate having an element formed on a single crystal silicon thin film on a transparent insulating substrate was used. I got

Further, a liquid crystal was sealed in the completed circuit and packaged to produce a light transmission type liquid crystal display device.

Embodiment 2 FIG. 3 is a schematic sectional view showing a flow of steps in a method of manufacturing a semiconductor device according to a second embodiment of the present invention. The details of a specific second embodiment of the present invention will be described in the order of steps in the drawing with reference to FIG.

In the step shown in FIG.
P-type (1 μm thick and 0.01 Ω · cm resistivity)
00) A silicon substrate 300 was prepared, and a porous layer 301 having a thickness of 30 μm was formed on the surface thereof in the same manner as in the first embodiment.

Next, in the step shown in FIG. 3B, an epitaxial layer 302 was formed to a thickness of 0.5 μm on the porous surface of the obtained substrate in the same manner as in the first embodiment.

Next, in the step shown in FIG. 3C, the same elements and electronic circuits as in the first embodiment were formed on the epitaxial layer 302.

Next, in a step shown in FIG. 3-4, while heating the substrate on which the elements are formed on a hot plate, an electron wax 303 is applied on the element forming surface 309, and a 4-inch silicon support substrate 311 is formed. Was bonded to the element formation surface 309.

Next, in the step shown in FIG. 3-5, the single crystal substrate 300 side was polished by about 280 μm by mechanical polishing to expose the porous region 301. Subsequently, this substrate was immersed in a hydrofluoric acid-based etching solution similar to that of the first embodiment, and only the porous region 301 was selectively etched.

Next, in the process shown in FIG. 3-6, a liquid crystal display device was fabricated on a transparent substrate in exactly the same manner as in the first embodiment.

(Embodiment 3) Details of a third embodiment of the present invention will be described with reference to FIG.

FIGS. 1-1 to 1-3 show the same steps as in the first embodiment.

Next, in the step shown in FIG. 1-4, while heating the substrate on which the elements are formed on a hot plate, the sheet-like phenolic resin 103 is applied to the element forming surface 1.
09 and then a 4-inch silicon support substrate 111
Were pasted together.

Next, in the step shown in FIG. 1-5, the bonded substrate was immersed in a selective etching solution, and only the porous portion 101 was selectively etched.

Next, in the step shown in FIG. 1-6, a 0.05 μm thick silicon nitride film 107 was deposited by plasma CVD on the back surface of the element formation surface 109 exposed by etching the porous silicon 101. The deposition temperature was 220 ° C.

Next, in the step shown in FIG. 1-7, the sample obtained by the above step was
10 and the surface of the silicon nitride film 107 were bonded using a polyimide resin adhesive 108. 350 ° C for bonded substrate
While heating the support substrate 111 from the element forming surface 109.
Was removed.

The phenolic resin 103 remaining on the element forming surface 109 was washed in dichloromethane, and the remaining phenolic resin was ashed with oxygen plasma to form an element on a single-crystal silicon thin film on a transparent insulating substrate. Got something.

Further, liquid crystal is sealed on the completed circuit,
Packaging was performed to produce a light transmitting substrate type liquid crystal display device.

In each of the embodiments described above, the light-transmitting insulating substrate is used. However, it is obvious that the present invention is not limited to the light-transmitting substrate.

[0075]

As described in detail above, an element is formed on a single crystal layer epitaxially grown on porous silicon, and the single crystal layer on which the element is formed is held on a single supporting substrate by wax or the like. Is selectively etched to form a single crystal layer on which an element is formed into a single thin film (membrane), which is bonded to a transparent insulating substrate using an adhesive, and the supporting substrate is separated with wax or the like. On top of that, a high-performance and high-performance electronic device can be easily manufactured.

The main effects of the present invention are that the film thickness distribution of the epitaxially grown layer is easy to control, the film thickness distribution of the SOI layer using this grown layer as it is is extremely uniform, Since the etching rate ratio in porous silicon is extremely large, the controllability of etching is greatly improved compared to the selective etching of the conventional selective polishing, so that the productivity is improved, and the thermal expansion coefficient is conventionally large. Another object of the present invention is to easily fabricate a silicon single crystal thin film device on a transparent insulating substrate, which has been extremely difficult to realize due to the difference.

Further, since the SOI substrate obtained by the present method is light-transmitting, it is possible to design a functional device utilizing this property, and to produce a large-scale integrated circuit having an SOI structure. Expensive SOS
In addition, a semiconductor substrate that can be substituted for SIMOX can be provided.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view for explaining steps of a method for manufacturing a semiconductor device according to first and third embodiments of the present invention.

FIG. 2 is an explanatory view of an apparatus when a silicon substrate is made porous.

FIG. 3 is a schematic cross-sectional view for explaining steps of a method for manufacturing a semiconductor device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an etching rate ratio between porous silicon and non-porous silicon.

[Explanation of symbols]

100, 200, 300 Single-crystal silicon substrate 101, 301 Porous silicon substrate or porous layer 102, 302 Epitaxial growth layer 103, 303 Wax or thermoplastic resin 107 Barrier layer 108, 308 Adhesive 109, 309 Device, or Element forming surface 110, 310 Transparent insulating substrate 111, 311 Supporting substrate 204, 204 'Etching solution 205, 205' Positive electrode 206, 206 'Negative electrode

Claims (12)

(57) [Claims] 1. a step of making the entire silicon single crystal substrate porous, a step of epitaxially growing a silicon single crystal thin film on one surface of the porous layer, and a step of forming an element on the epitaxial layer. and optional support substrate the element formation surface, the step of bonding via the wax or thermoplastic resin, a step of divided porous silicon portion of the bonded substrates, the epitaxial layer in which the element is formed, Bonding the insulating substrate to another insulating substrate with an adhesive, and separating the wax or the thermoplastic resin from the epitaxial layer on which the element is formed by melting or softening the supporting substrate. A method for manufacturing a semiconductor element. 2. A step of making a surface layer on one surface of a silicon single crystal substrate porous, a step of epitaxially growing a silicon single crystal thin film on the porous surface, and a step of forming an element on the epitaxial layer. When the optional support substrate the element formation surface, the step of bonding via the wax or thermoplastic resin, after removing by polishing the silicon single crystal substrate portion, the step of divided the porous silicon portion Bonding an epitaxial layer on which the element is formed to another insulating substrate with an adhesive; and melting or softening the wax or thermoplastic resin to form the epitaxial layer on which the support substrate and the element are formed. A method for manufacturing a semiconductor element, comprising: separating a layer. 3. The semiconductor according to claim 1, further comprising a step of providing a barrier layer for preventing diffusion of mobile ions between the epitaxial layer on which the element is formed and the adhesive. Method for manufacturing element. 4. The method for manufacturing a semiconductor device according to claim 1, wherein the removal of the porous silicon portion is performed by using a mixed etching solution of hydrofluoric acid, hydrogen peroxide solution, and alcohol. 5. The method for manufacturing a semiconductor device according to claim 1, wherein the step of forming a porous body is anodization. 6. The method according to claim 1, wherein the other insulating substrate is a transparent insulating substrate containing SiO ₂ as a main component.
Or a method for manufacturing a semiconductor device according to 2. 7. The method for manufacturing a semiconductor device according to claim 1, wherein the epitaxial layer on which the device is formed is bonded to another insulating substrate without using the adhesive. 8. Porous silicon on a silicon single crystal substrate
Prepare a substrate with a silicon single crystal thin film through the layer
Process and Forming an element on the silicon single crystal thin film; The element forming surface may be formed with any supporting substrate, wax or thermoplastic.
Laminating through a conductive resin, Removing the porous silicon layer; The silicon single crystal thin film on which the element is formed is
Bonding the substrate with an adhesive, Melting or softening the wax or thermoplastic resin
The silicon on which the support substrate and the element are formed
Separating a single crystal thin film, A method for manufacturing a semiconductor device, comprising: 9. A silicon single crystal thin film on which said element is formed.
Prevents mobile ions from diffusing between the membrane and the adhesive
9. The method according to claim 8, further comprising the step of providing a barrier layer.
3. The method for manufacturing a semiconductor device according to item 1. 10. The method according to claim 10, wherein the other insulating substrate is made of SiO. _Two  The main
Claims: It is a transparent insulating substrate.
9. The method for manufacturing a semiconductor device according to item 8. 11. A silicon single crystal on which said element is formed
Paste the thin film with another insulating substrate without using the adhesive
9. The semiconductor device according to claim 8, wherein the semiconductor device is aligned.
Method of manufacturing. 12. A silicon single crystal on a porous silicon layer
A substrate having a thin film is prepared, and the silicon single crystal thin film is
A device is formed, and the element forming surface is formed on
It is characterized in that it is bonded via
Bonded substrate.