JPH02106922A - Selective epitaxial growth method - Google Patents

Abstract

PURPOSE:To epitaxially grow a single crystalline Si film on an exposed single crystalline Si substrate by vapor growth under reduced pressure at SiH4 gas partial pressure at a substrate temperature of a range of higher temperature from a predetermined boundary line by means of thermal decomposition of SiH4. CONSTITUTION:A reduced pressure vapor growth is conducted by means of thermal decomposition of SiH4 at a substrate temperature and SiH4 gas partial pressure of a range of higher temperature from a boundary line set at a line passing two points of a point of 20mTorr of SiH4 gas partial pressure at 890 deg.C of substrate temperature and a point of 20mTorr of SiH4 gas partial pressure at 950 deg.C of substrate temperature in which the substrate temperature is at an abscissa axis and the SiH4 gas partial pressure is at an ordinate axis. The substrate temperature and the SiH4 gas partial pressure are set in such a range. Thus, an Si film 8 is not grown on an insulating film 2, and a single crystalline Si film 3 is epitaxially grown only on the single crystalline Si substrate exposed through an opening 2a.

Description

DETAILED DESCRIPTION OF THE INVENTION A) Industrial Application Field The present invention is applied to a single crystal Si substrate on which a 5IOz film is selectively formed, only on the exposed part of the 84 substrate surface where the 5IOz film is not formed. A selective epitaxial growth method for selectively growing a single crystal Si film is used.

Conventional technology The one in which a single-crystal Si layer is formed on an insulator R (including an insulator substrate) is SOI (Silicon on In).
5 ulat.

r) structure, and is known as a structure that allows easy isolation of elements in a narrow area and allows for higher integration and higher speed.

As compared to conventional semiconductor integrated circuits (FC) in which elements are fabricated on a Si substrate, research and development are being actively conducted on this because it offers improved characteristics.

There is an in-phase epitaxial growth method to form a single crystal Si film on the absolute R layer, and this method is used to form a single crystal Si film on the single crystal 81 substrate. A part of the substrate surface is exposed as a seed to form an insulating film, an amorphous S, I (hereinafter referred to as a-94) film is deposited on the seed and the insulating film, and annealed at a low temperature of about 600°C. By doing so, the in-phase growth in the lateral direction results in a-8
This is to crystallize the i-film.

However, in this in-phase growth, crystallization of the a-3T film preferentially progresses in the lateral direction in the <100> direction, so vertical growth from the seed upwards is required before lateral growth. In solid phase epitaxial growth, a-5ill on the seed
Therefore, it is not possible to make the step between the seed and the surface of the insulating film very large.

However, if the a-3i film is thin and the step difference between the 5 seed and the insulating film surface is large (the insulating film is thick), the deposited a
In the -5i film, a step break occurs at the boundary between the insulating film and the seed, or even if a step break does not occur, internal stress increases at the step part, so lateral in-phase growth hardly occurs.
Even if it occurs, the lateral growth distance will be small.

For this reason, it is necessary to make the level difference between the seed and the surface of the insulating film as small as possible, that is, to make the insulating film thinner.
Formed below Å.

However, when configuring a three-dimensional circuit element with a stacked Sol structure, the device is formed under an insulating film layer, so when considering protection to stabilize the device structure, wiring, and electrical characteristics, it is necessary to The film needs to have a thickness of IAIa or more.

For example, '5ELECTIVE EPITAX
IAL GROWTtlOF 5ILICON B
Y CVD AND ITS DING HERMOD
YNAMICC0N5IDERATIONJ (PRO
CEEDINGS OF THE TENTHINTE
RNATIONAL CONFERENCE ON
CHEMICAL VAPORDEPO5ITI
ON 1987. Procedurein @ Vol, 8
7-8. PP, 379-388>, 5iHxC12-HCj! -H5(') Normal pressure CVD
By using the low-ff CVD method, a single crystal Si film can be grown only on the exposed Sl substrate surface at a substrate temperature of 950°C to 1050°C under normal pressure and 850°C to 950°C under reduced pressure! ! Selective epitaxial growth (Selec)
tive Epitaxial Gr.

wth (hereinafter referred to as 5EG) method is being considered.

This SEG method using chlorine-based gas involves depositing a single crystal Si film on the exposed substrate surface and a polycrystalline Si film on SfOglI by thermal decomposition of chlorine-based gas, and depositing these formed Si films. At the same time, etching by HCffi occurs simultaneously with polycrystalline Si film, and the etching speed is higher than that of single crystal Si film. Using the fact that l is larger, 5iov
This eliminates the deposition of a Si film on the X.

c) Problems to be solved by the invention However, in the SEG method using the above-mentioned chlorine-based gas, CI! which is considered to be an etchant! Etching is performed by radicals attacking and cutting 5i-st pounds or 5i-0 pounds, and as a result of this etching, many defects are generated near the surface of the crystalline Si film and the polycrystalline Sl film in the deposited layer. Furthermore, by further depositing an a-8i film on the Si film formed by this SEG method, this a-81
When growing the film by solid phase epitaxial growth, a-5i
CP atoms remaining in the film will be mixed in and will inhibit crystallization. Then, the lateral growth distance becomes short, and as a result, a substrate with a large area Sol structure cannot be obtained.

Furthermore, the life of the CVD device (particularly the low pressure CVD device) is also shortened.

The present invention has been made in view of these points, and provides an SEG method for epitaxially growing a single-crystal Si film only on the exposed single-crystal St substrate without using chlorine gas. .

2) Means for Solving the Problems The present invention forms an insulating film on a single-crystal Si base, forms an opening in the insulating film to expose the surface of the single-crystal Si base, and A single-crystal Si film is formed using SiH only on the single-crystal Si base portion exposed in the opening formed in the
4, which is a selective epitaxial growth method that selectively grows epitaxially by low-pressure vapor phase growth using thermal decomposition, where the horizontal axis is the substrate temperature and the vertical axis is the SiH* gas partial pressure, the substrate temperature is 890°C, 5i ) i4 gas partial pressure Om
The boundary line is a line passing through the point Torr and the point where the substrate temperature is 950°C and the SiHm gas partial pressure is 20mTorr. This method performs low-pressure vapor phase growth by decomposition.

e) Effect Originally, the 5ho2 surface, which is an insulating film, has fewer dangling bonds of St than the single crystal 81 surface.
The number of kink sites to which surface adsorbed species (Si) bind during reaction is small, and crystalline Si nuclei are difficult to form on the surface of the 5i film 2. Therefore, if the base temperature is raised sufficiently, the surface adsorbed species The migration becomes more intense, making it difficult for surface adsorbed species to adsorb to kink sites. In addition, 5 (by setting the H4 gas partial pressure to a sufficiently high degree of vacuum, surface absorption during surface migration!
It is more likely that the species will be exhausted before being adsorbed to kingsite.

By keeping the base temperature and SiH4 gas partial pressure within the ranges mentioned above, no Si film will grow on the insulating film.
A single crystal Si film is epitaxially grown only on the single crystal St base exposed through the opening.

Embodiment 1 Figures A to G show a schematic process diagram of an embodiment of the present invention.
In this embodiment, a single crystal 51 substrate is used as the single crystal Si base, but a single crystal S (film) formed on the substrate may also be used.

(1) is a single crystal 81 substrate as a single crystal 81 base with the (100) plane as the main surface, and a film thickness of I as an insulating film on the surface.
A 5ift film (2) of about N4 is formed by hot change (
In FIG. 1A), this 5102 film (2) is then selectively formed with openings (2a) that expose the surface of the Si substrate as a seed using a well-known photolithography technique ( Figure 1B).

Next, the substrate having the patterned 5I02 film (2) was heated to 940°C with an infrared lamp in a vacuum below IX10-@taTorr, and after keeping the temperature constant, a flow rate of 150cc/ ++ Introduce Ar gas at 65 mTorr, perform Ar sputtering, and clean the substrate surface for 5 minutes (first
Figure C), at this time, for example, the RF frequency is 13.56MH
21 output of 50 W and a DC bias of -toov was applied to the substrate.

After cleaning the surface, increase the substrate temperature to 940°C.
While keeping the temperature at
A partial pressure of >13 mTorr is supplied to selectively epitaxially grow a single crystal S (film (3)) only on the surface of the Sl substrate (seed part (1a)) exposed through the opening (28). The crystalline Si film (3) is grown to the same thickness as the 5i02 film (2) (FIG. 1D).

Then, the supply of SiH4 gas was stopped and the substrate temperature was lowered to 550°C in a vacuum of less than I x 101 mTorr while the substrate was placed in the reaction chamber of the vapor phase growth apparatus that performed selective epitaxial growth. Flow the gas t5
00 cc/ml, Ar partial pressure of 200 mTorr was applied, 13.56 MHz RF was applied at output cuff 0 W, a DC bias of -60 V was applied to the substrate, and the substrate surface was cleaned by Ar sputtering for 10 minutes. 1
Figure E).

After cleaning the surface, lower the substrate temperature to 5.
While maintaining the temperature at 50°C, the supply of Ar gas was stopped and the RF
After turning off the DC bias, 5fH4 gas was supplied into the reaction chamber at a flow rate of 200 sccm and a partial pressure of 6 to 7 Torr to form a 1-8i film (4) on the substrate surface at a growth rate of 6,000 layers (growth rate of 200 tons and 7 sins). ) (Fig. 1F).

After that, Ar gas is introduced into the reaction chamber to remove the remaining SiH
After exhausting the a gas, perform vacuuming and lower the substrate temperature to room temperature. Then, using an annealing device, atmospheric pressure N
A 5i-8i film (4) was solid-phase epitaxially grown by annealing at a temperature of 600°C for 12 hours in a chamber atmosphere, and a single-crystal Si film ( 4') to obtain the first mG).

Now, SEG is performed in the step shown in the first diagram, and the single crystal Si film (
3) If there are many defects on the surface, the delay time from the start of annealing of the A-51 film to the occurrence of in-phase growth will be longer, *
The epitaxial growth distance in the lateral direction of the -9i film becomes shorter.Also, if polycrystalline S (nuclei) is generated on the 5ift film (2), polycrystalline nuclei that inhibit epitaxial growth are generated quickly. The epitaxial growth distance in the lateral direction of the 8i film becomes short.Therefore, it is necessary to perform SEG well in the step of the first diagram.

FIG. 2 is a diagram showing the relationship between substrate temperature and SiH4 gas partial pressure when SEG occurs and when SEG does not occur. The white circle is S
+ When the RLvJ crystal Si pattern is epitaxially grown only on the substrate and no Si film is deposited on the 5iOz film (i.e., S
EG occurs〉, black circles indicate Tokyu crystal Si on the 51 substrate.
The film is epitaxially grown and shows S (when the film is deposited, ie, SEG does not occur) even on the 5iOz film.

As is clear from Fig. 2, with the base temperature on the horizontal axis, S i
The Ha gas partial pressure is taken on the t# axis, the substrate temperature is 890°C, and the Si
H4 gas partial pressure O1! Torr point a and substrate temperature 950
℃, SiH4 gas partial pressure 20 mTorr, and the line passing through the two points is taken as a boundary line, and when the substrate temperature and SiH4 gas partial pressure are set in the higher temperature range from this boundary line, low pressure vapor phase growth is performed. SEG is realized only in

This is because if the base temperature is raised sufficiently, the surface migration of the surface adsorbed species will be intense, making it difficult for the surface adsorbed species to adsorb to the kink site, and if the SiH4 gas partial pressure is raised to a sufficiently high degree of vacuum. Therefore, there is a high possibility that the surface-adsorbed species during surface migration will be exhausted before being adsorbed to kingsite.

By setting the base temperature and SiH<gas partial pressure in the range shown by diagonal lines in FIG. 2, Sh.

No Si film is deposited on the two films, and a Si film is deposited only on the single crystal Si substrate, that is, SEG is performed.

g) Effects of the Invention As is clear from the above description, the present invention has a substrate temperature of 5iH.
h By controlling the gas partial pressure, SE can be performed without using chlorine gas.
G can be done. Therefore, it is possible to suppress the occurrence of defects in the single crystal Si film that serves as a seed for solid phase epitaxial growth, and to reduce the chance of impurities being mixed into the a-5i film. As a result, when growing the a-5l film by in-phase epitaxial growth, the lateral growth distance can be extended, and it is possible to provide a substrate with a large area SOI structure.

Furthermore, since chlorine gas is not used, it can contribute to extending the life of growth equipment such as low pressure CVD equipment.

[Brief explanation of the drawing]

1A to 1G are process explanatory diagrams of an embodiment of the present invention, and FIG. 2 is a diagram showing conditions for realizing SEG. (1)...Single crystal Si substrate, (la)...Seed,
(2)...5i02 film (insulating film), (2a)...opening part, (3>...single crystal S eye L(4)...a-Sl
Film, (4')...Single crystal S (film. Figure 1

Claims (1)

[Claims] 1) An insulating film is formed on a single-crystal Si base, and the single-crystal S
i forming an opening in the insulating film that exposes the surface of the base;
In a selective epitaxial growth method, a single crystal Si film is selectively epitaxially grown only on the single crystal Si base portion exposed in the opening formed in the insulating film by low pressure vapor phase growth using thermal decomposition of SiH_4, When the horizontal axis is the base temperature and the vertical axis is the SiH_4 gas partial pressure, the substrate temperature is 890°C and the SiH_4 gas partial pressure is 0 mT.
The boundary line is a line passing through the point of orr and the point where the substrate temperature is 950°C and the SiH_4 gas partial pressure is 20 mTorr. A selective epitaxial growth method characterized by performing low pressure vapor phase growth by decomposition.