JP2762103B2 - Method for forming SOI film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention forms an insulating film on a single crystal silicon substrate,
Further, a single crystal silicon film is grown on this insulating film to
The present invention relates to a method for forming an SOI film for forming an I [Silicon On Insulator] film.

[Conventional technology]

In general, SOI films have characteristics such as easy isolation of elements, prevention of latch-up, and high mobility obtained by thinning, so that substrate materials for high-speed and highly integrated devices can be used. In particular, it has attracted attention as a three-dimensional circuit element material having a laminated structure, and has been actively researched and developed in recent years.

Incidentally, as one of the techniques for forming such an SOI film, there is known a method of depositing polycrystalline silicon on an amorphous substrate or an amorphous film and melting and recrystallizing the same using a laser beam or an electron beam. However, there are problems such as low throughput and difficulty in controlling the crystal orientation of the recrystallized layer.

Another method is the solid phase epitaxial growth method (hereinafter referred to as the SPE method), in which an amorphous insulating film is formed on a Si substrate, and a part of the insulating film is removed to expose an exposed surface on the Si substrate. After forming an amorphous Si (hereinafter referred to as a-Si) film on the exposed surface and the insulating film, the film is formed in an N ₂ atmosphere.
Annealing is performed at 0 ° C. for several tens of hours, and vertical solid phase epitaxial growth (hereinafter referred to as V-SPE) and lateral solid phase epitaxial growth (hereinafter referred to as L-SP) using the exposed surface as a seed.
(Referred to as E) to make the a-Si film single crystallize.

However, in the case of the SPE method, when the V-SPE proceeds with the exposed surface of the Si substrate as a seed, if the step between the insulating film and the exposed surface is large, stress occurs at the step, and the insulating film and the Si Strain is generated at the interface, and the progress of the L-SPE is hindered, so that there is a disadvantage that a sufficient L-SPE distance cannot be obtained.

In order to solve such inconveniences, a recess structure in which the step between the insulating film and the exposed surface of the Si substrate is made as small as possible has been adopted. In order to further increase the L-SPE distance, phosphorus [P] has been used. Annealing is performed after ions are implanted into the a-Si film. For example, Applied Ph
As reported in ysics Letters 48 (12), 24 March, 1986, pp. 778-775, an L-SPE distance of about 45 μm can be obtained by implanting p ⁺ in a recess structure with a step of about 1000 °. ing.

By the way, when creating a three-dimensional circuit element, when a device is built in a lower layer, a step between an exposed surface of a Si substrate as a seed and an insulating film as a passivation film may be 1 μm or more. Since the step hinders the progress of the L-SPE, it is difficult to eliminate this in the recess structure described above.

Therefore, it has been considered to embed a seed portion of single-crystal silicon in advance on the exposed surface of the Si substrate.
-It has the advantage that the deposition of a-Si and the embedding of the seed portion by -SPE can be performed continuously, and it is attracting attention as a promising technology in the future.

The SPE method using the seed part filling technique by the selective epitaxial growth method will be described with reference to FIG. 3, as shown in FIG.
The i substrate (1) thermal oxidation method on such to form a SiO ₂ film having a thickness of 1 [mu] m (2), a part of the SiO ₂ film (2) is removed by etching <100> direction in a stripe pattern About 2μ in width
The exposed surface (3) of the m-Si substrate (1) is formed, and the substrate temperature is 940 ° C. by the reduced pressure CVD method using the thermal decomposition method of SiH ₄ gas.
When Si is epitaxially grown under the condition of a SiH ₄ gas flow rate of ₄ SCCM, single crystal Si (hereinafter referred to as c-Si) is selectively grown only on the exposed surface (3) as shown in FIG. A seed part (4) is formed on the exposed surface (3).

At this time, (111) is formed on the side surface of the seed portion (4) of c-Si.
A facet surface (5) is formed.

Further, since the growth rate under the above-mentioned conditions is about 200 ° / min, the step between the SiO ₂ film (2) and the exposed surface (3) is 1 μm.
When it is m, selective epitaxial growth may be performed for about 1 hour to fill this.

Next, after the formation of the seed portion (4), the substrate temperature was lowered to 550 ° C., and the partial pressure of SiH ₄ was about 10 Torr and the deposition rate was 200 ° C./mi by the reduced pressure CVD method using the thermal decomposition method of SiH ₄ gas.
The reaction was carried out for 15 minutes under the condition of n, and as shown in FIG. 3 (c), a film thickness of 3000 に was formed on the SiO ₂ film (2) and the seed portion (3).
A-Si film (6) is formed.

Then, (180 KeV, 7 × 10 ¹⁵ cm ^-2 ), (100 KeV, 3 × 10 ¹⁵
cm ⁻² ) and (50 KeV, 2 × 10 ¹⁵ cm ⁻² ), as shown in FIG. 3D, three times over the a-Si film (6).
P ⁺ is implanted, and 3 × 10 ²⁰ is almost uniformly formed on the a-Si film (6).
After implanting P ⁺ to an ion concentration of cm ⁻³ , an a-Si film (6)
Is annealed at 590 ° C. for 15 hours in an N ₂ atmosphere to form an L-SPE layer (7) as shown in FIG.

At this time, the a-Si film in a region where L-SPE does not occur (6)
Is polycrystallized to form a polycrystalline Si film (8).

By the way, a scanning electron microscope (SEM) photograph of the cross section of the SOI film thus formed is as shown in FIG. 4, in which SEG is selective epitaxial growth and corresponds to the seed portion (4) in FIG. The Si Substrate corresponds to the Si substrate (1). As can be seen from FIG. 4, a recess is formed at the boundary between the seed portion (4) of the SEG and the L-SPE layer (7). Seed section by SEG as described above (4)
The facet surface (5) formed during the growth of
It is considered that this occurred because the progression of SPE was inhibited.

[Problems to be solved by the invention]

In the conventional case, since the progression of L-SPE is hindered by the facet surface formed when the seed portion (4) is buried by the SEG, the L-SPE distance is limited to about 10 μm.
-There is a problem that the SPE distance cannot be increased.

The present invention has been made in consideration of the above points, and has as its object to increase the L-SPE distance so that a large-area SOI film can be formed.

[Means for solving the problem]

In order to achieve the above object, in the method for forming an SOI film of the present invention, an amorphous insulating film is formed on a single crystal silicon substrate, and a part of the insulating film is removed to form an exposed surface on the substrate. Forming a seed portion of single crystal silicon on the exposed surface by selective epitaxial growth, forming a single crystal silicon film and a polycrystalline silicon film on the seed portion and the insulating film, respectively, Implanting silicon ions into the surface of the film and the polycrystalline silicon film, amorphizing the surface layer portion of the single crystal silicon film and the entire polycrystalline silicon film to form an amorphous silicon layer; After injecting phosphorus into the porous silicon layer, the amorphous silicon layer is monocrystallized by a solid phase epitaxial growth method.

[Action]

In the above configuration, when a single crystal silicon film is formed on the seed portion formed by the selective epitaxial growth method and a polycrystalline silicon film is formed on the amorphous insulating film, the seed portion is formed at the stage where the seed portion is formed. A facet surface is formed on the side surface of the portion, but in the subsequent formation process of the single crystal silicon film and the polycrystalline silicon film, no facet surface is formed at the boundary between the single crystal silicon film and the polycrystalline silicon film. , The step between the exposed surface and the insulating film is 1
Even in the case where the length is not less than μm, the formation of the facet surface can be prevented and the L-SPE distance can be increased.

〔Example〕

An embodiment will be described with reference to FIG. 1 and FIG.

First, as shown in FIG. 1 (a), similarly to the case of FIG. 3, SiO ₂ as an amorphous insulating film having a thickness of 1 μm is formed on a (100) Si substrate (9) by a thermal oxidation method or the like. Forming a membrane (10),
A part of the SiO ₂ film (10) is removed by etching.
Si substrate with a width of about 2 μm in stripes in the 100> direction (9)
The exposed surface (11) is formed.

Next, by a reduced pressure CVD method using a thermal decomposition method of SiH ₄ gas, a substrate temperature of 940 ° C. and a SiH ₄ gas flow rate of ₄ SCCM were used for about 1 hour.
Time, c- on the exposed surface (11) as shown in FIG.
The Si seed portion (12) is selectively epitaxially grown.

As in the case of FIG. 3, a (111) facet surface (13) is formed on the side surface of the seed portion (12).

After that, the substrate temperature was lowered to 800 ° C and the SiH ₄ gas flow rate was 20S.
Epitaxial growth is performed at a growth rate of about 500Å / min under the conditions of CCM, SiH ₄ gas partial pressure of 100 mTorr, and a c-Si film (14) is grown on the seed portion (12) and on the SiO ₂ film (10). A polycrystalline Si film (hereinafter referred to as a p-Si film) (15) is grown.

At this time, growth is performed for 5 to 6 minutes so that the p-Si film (15) has a thickness of about 3000 °.

Furthermore, (180 KeV, 2 × 10 ¹⁶ cm ⁻² ), (100 KeV, 2 × 10 ¹⁶
cm ⁻² ) and (50 KeV, 2 × 10 ¹⁶ cm ⁻² ), as shown in FIG. 1D, the c-Si film (14) and the p-Si film (1
5) Inject Si ⁺ three times to amorphize the entire surface layer of the c-Si film (14) and the p-Si film (14) to form an a-Si layer (16). .

And (180 KeV, 7 × 10 ¹⁵ cm ^-2 ), (100 KeV, 3 × 10 ¹⁵
cm ⁻² ) and (50 KeV, 2 × 10 ¹⁵ cm ⁻² ), P ⁺ was implanted into the a-Si layer (16) three times, and then implanted at 600 ° C. in an N ₂ atmosphere at 10 ° C. After annealing for more than an hour, as shown in FIG. 1 (e), the a-Si layer (16) is monocrystallized by the SPE method to form a c-Si layer (17), thereby forming an SOI film.

At this time, the a-Si layer (17) on the seed portion (12) is
Single crystallized by SPE, a-Si layer (1) on SiO ₂ film (10)
7) is single-crystallized by L-SPE.

By the way, at the stage where the seed portion (12) is formed, a facet surface (13) is formed on the side surface of the seed portion (12). Thereafter, the c-Si film (14) and the p-Si film (15) are epitaxially grown. When this is done, no facet is formed at the boundary between the c-Si film (14) and the p-Si film (15). As a result, the exposed surface (11) and the SiO ₂ film (10) Step is 1
Even in the case where the thickness is not less than μm, the formation of the facet surface as in the related art can be prevented, and the L-SPE distance can be greatly increased.

FIG. 2 shows an electron micrograph when the surface of the SOI film thus obtained was revealed using a light etching solution having a composition of chromium oxide-hydrofluoric acid-copper nitrate-acetic acid-water. SEED is the seed part (1
L) from the boundary between SEED and L-SPE in FIG.
It can be seen that the width of -SPE is about 20 [mu] m, and an L-SPE distance of about 20 [mu] m can be obtained by the method described above.

〔The invention's effect〕

Since the present invention is configured as described above,
The following effects are obtained.

Since a monocrystalline silicon film was formed on the seed portion formed by the selective epitaxial growth method and a polycrystalline silicon film was formed on the amorphous insulating film, a facet surface was formed on the side surface of the seed portion at the stage of forming the seed portion. However, due to the subsequent steps, no facet surface is formed at the boundary between the single crystal silicon film and the polycrystalline silicon film, and even if the step between the exposed surface and the insulating film is 1 μm or more. Therefore, it is possible to prevent the formation of the facet surface as in the prior art, and to increase the L-SPE distance,
This makes it possible to obtain a large-area SOI film, which is extremely effective as a technique for producing a three-dimensional circuit element.

[Brief description of the drawings]

1 and 2 show one embodiment of a method for forming an SOI film according to the present invention. FIGS. 1 (a) to 1 (e) are cross-sectional views showing a forming process, and FIG. 3 (a) to 3 (e) are cross-sectional views showing the forming steps of the conventional example, and FIG. 4 is an electron micrograph of the cross section of the SOI film formed by the steps of FIG. It is. (9) ... Si substrate, (10) .... SiO ₂ film, (11) ... exposed surface (12) ... seed unit, (14) .... c-Si film, (15)
... p-Si film, (16) ... a-Si layer, (17) ... c-Si
layer.

Claims (1)

(57) [Claims] An amorphous insulating film is formed on a single crystal silicon substrate, an exposed surface is formed on the substrate by removing a part of the insulating film, and a single crystal is formed on the exposed surface by a selective epitaxial growth method. After forming a silicon seed portion, a single-crystal silicon film and a polycrystalline silicon film are formed on the seed portion and the insulating film, respectively, and silicon ions are formed on the surfaces of the single-crystal silicon film and the polycrystalline silicon film. Implanting, amorphizing the surface layer portion of the single crystal silicon film and the entire polycrystalline silicon film to form an amorphous silicon layer, implanting phosphorus into the amorphous silicon layer, A method for forming an SOI film, comprising monocrystallizing a porous silicon layer by a solid phase epitaxial growth method.