JPH03237093A - Method for selectively growing si crystal - Google Patents

Abstract

PURPOSE:To selectively grow an Si crystal only on Si at a low temp. by diluting gaseous silicon hydride with a carrier gas in a prescribed ratio. CONSTITUTION:When Si is selectively crystallized only on the Si part of the surface of a substrate by a chemical vapor growth method, gaseous silicon hydride is diluted with H2 as a carrier gas in <=5X10<-5> volume ratio of the silicon hydride to the carrier gas at the time of carrying with the carrier gas. Since an etching reaction for removing Si on SiO2 is not utilized, selective crystal growth is performed at <=800 deg.C.

Description

[Detailed description of the invention] [Field of industrial use]

The present invention relates to 5ol (Silicon) constituting a three-dimensional circuit element.
Regarding seed crystal embedding technology in con-on-in-5ulators and element isolation technology in integrated circuits, in particular, Si is grown only on Sl, and Si such as 5i02 is grown.
This invention relates to selective growth of S1 crystals that does not cause Si growth on other surfaces.

[Conventional technology]

In selective crystal growth of Si by chemical vapor deposition (CVD) under reduced pressure and normal pressure, in order to improve the selectivity of growth on Sl and SiO2, J(C is introduced or
A method using a raw material gas containing (For example, Nature, 195485
(1962)) This means that if C1 is introduced, S i
h), l', it is difficult to be touched. This Sl etching and growth occur in competition, and 51
02, because the etching reaction rate is higher than the growth rate (crystal nucleation rate), the growth of S does not proceed, but on S1, the growth rate is faster and Si crystal growth progresses. I will do it. In this way, the most common method is the selective crystal growth method in which the crystal of Sl is grown only on Sl without growing Si on 5i02. There are also reports on the possibility of selective crystal growth in molecular beam crystal growth (MBE) (for example, J.
, Appl, Phys, 21534 (1982)
), the principle is as follows. Also in selective growth in MBE, S i O2-, l
It is considered that the adsorption S1 of = is removed by etching. The reaction is as follows. S 1 → Si
(1) (Gas) (Adsorption) Si +5i02 → 2SiO (2) Adsorption) (Solid) (Gas) The reaction rate of (2) is determined by the equilibrium vapor pressure of SiO. In other words, it is a function of temperature; the higher the temperature, the faster the reaction rate. In addition, the number of adsorbed Si is S1 supplied per unit time.
Determined by the number of atoms and substrate temperature. Therefore, when the supply amount of Si is fixed, when the substrate temperature Tc exceeds a certain temperature, the number of adsorbed atoms in the equilibrium state becomes smaller than the critical value for generating crystal nuclei due to the reaction (2), and the Si No growth occurs and etching of 5102 occurs. In addition, by reducing the amount of Si supplied,
It is possible to lower Tc. Therefore, in the case of MBE, it is easier to lower the temperature than in CVD, and selective crystal growth is said to be possible at about 3QO''C.

[Problem to be solved by the invention]

However, in the chemical vapor deposition method using the above-mentioned HCI, CI-containing source + 1 phase, etc., the above-mentioned etching reaction can only be performed at a sufficient rate at temperatures above 1000° C. This causes the crystal growth to occur at low temperatures. In addition, in the above molecular beam crystal growth method, 11 of selective crystal growth (although it has the FiJ ability to measure temperature F),
(Substrates that can be selectively grown using this method are limited to small and small numbers of substrates that can be implanted with molecular beams, and throughputs that can process a large number of substrates at once, such as with the CVD method, are not expected, and it is difficult to reduce costs.) I'm having a problem with this.

[Means for Solving the Problems] In order to solve the above-mentioned conventional problems, the present invention provides a chemical vapor deposition method in which a silicon hydride gas is transported on a hydrogen carrier gas (thereby, a partial Si In the method of selectively growing SI crystals, dilution of silicon hydride-based gas with carrier gas (silicon hydride-based gas/112
volume ratio) is set to 5 x 10-5 or less. According to the present invention, in high-throughput CVD,
Selective crystal growth that does not require the introduction of HCI gas, which was previously considered impossible, is now possible in CVD. When using S i H4 as the raw material gas, this dilution ratio (volume ratio: S i I(4/I(2) is 5X10
If it is -5 or less, selective crystal growth is possible, but in terms of growth rate, lXl0-5 or more is preferable. In particular, from the viewpoint of growth rate and completeness of selectivity, about 2×10″5 is particularly preferable. In addition to 5il14, silicon hydride gas such as Si2H6 can be used as the raw material gas. Dilution ratio of the raw material gas is thought to vary depending on the decomposition rate of each gas. For example, in the case of 5i2116, the decomposition rate is 81) (4
Since the decomposition rate is faster than the decomposition rate and the S1 content in the same volume is large, at the same dilution ratio as S i l-]4, the amount of S1 leather supplied per unit time is larger than that of S1+4. Therefore, the dilution ratio of Si2H6 must be lower than 5x105. When 5i2HG is used as the original 41 gas, the dilution ratio (volume ratio: S i 2 H6 / 112) is 5 × 10 ~
It is preferable to set it to 2×105. The feed rate of the source gas can be adjusted depending on the amount of substrates being processed simultaneously and the growth rate required. Further, when carrying out the selective growth, it is preferable that the substrate be in a heated state, and according to the present invention, selective growth can be carried out even if the temperature of the substrate is below 800°C. In particular, it is preferable to set the temperature of the substrate to 700 to 850°C, since the effect of the selective growth method of the present invention will be significant. Furthermore, the addition of an etching gas (eg HCI) or a diluent gas other than H2 essentially does not have a significant effect. Therefore, if the raw material gas is diluted to a certain extent by the carrier gas H2, it is thought that the same effect will appear regardless of whether or not Q) other gases are added. [Operation] CV I) ζ Go 0 Furu S i 02 j The growth of Si is thought to proceed through the following process. The supplied raw material gas (for example, S i H4) is adsorbed on the surface of the substrate, decomposed, and while diffusing on the 5102 substrate, several adatoms collide repeatedly, producing crystal nuclei of a certain size or more. They are consumed by things or become detached from them. At this time, it is known that the rate of formation of crystal nuclei, Lif, largely depends on the number of adatoms, the surface diffusion coefficient of the adatoms, and the interaction between the growth species and the substrate. If the lifetime of the adsorbed atoms until they are desorbed is shorter than the lifetime expressed as the reciprocal of the probability of crystal nucleus generation, it is expected that no crystal nuclei will be generated. It has been reported that H2 as a carrier gas inactivates the surface of S i 02, reduces the number of adsorbed atoms on the surface, increases the surface diffusion coefficient, and reduces the probability of crystal nucleation. ing. The mechanism is that +12 introduced as a carrier gas covers the surface of t[I] atoms or 5i02. In this case, 11 covering the surface is inferior if it exists in the form of O-1 (.The number of O-H bonds decreases as the substrate temperature increases, and almost ceases to exist at about 900°C. , is reported to be expected from the negative dependence of crystal nucleus density on temperature j.And, due to this O-H, S i 02
Since the a surface is coated, the growing species Sl
It is thought that chemical adsorption becomes less of an adsorption form on the 5i02 surface, and physical adsorption becomes predominant. Therefore, it can be assumed that the adsorption energy of adsorbed atoms (0) is low, diffusion and desorption are easy, the adsorbent j'-depletion is reduced, and the crystal nucleation density is reduced. According to the present invention, carrier gas H2 for original gas
By increasing the dilution ratio of ζ, the inactivation of the 5i02 surface is more complete than in conventional growth, reducing the number of adatoms and increasing the diffusion coefficient at the surface. ° Then, the lifetime of the adatom due to desorption is made shorter than the lifetime due to the formation of crystal nuclei + 4゜ (this makes it possible to reduce the till rate of crystal nucleus generation to 0 on the 5102 surface. Note that the 81 surface The 11 atoms above do not exist stably because the bond energy of 5l-1l is small, and S
I am encouraged that the growth of l will not be hindered.

[Example] 80()℃ using normal pressure CVD equipment using high frequency heating method
Si was grown on the substrate held in stripes on the S1 surface and the 5102 surface. At this time, the flow rate of H2 was fixed at 8000 sec, and the
Varying the 7M amount of iH4 from 0.05 to 1 sec, (dilution ratio = 6.3X10-6 to 1.3XIO =)
S i 02 after holding for 1 hour under the conditions of each) q
The density of crystal nuclei on the surface was measured. The measurement results are shown in Figure 1. (For the dilution ratio where the crystal nucleus density is indicated as O, the growth for 10 hours is (j becomes 51
02 surface 1. It was confirmed that no crystal nuclei were observed. ) As can be seen from this figure, the formation of crystal nuclei on the surface of 5i02 is hardly observed when the dilution is 1 or more than 5 x 10, and it cannot be completely removed when the dilution is 2 x 10-5. This may be due to the complete coverage of S i 0214 by H, which reduces the number of adatoms on the surface, decreases desorption j, decreases Nerky, etc., and reduces the lifetime due to desorption of adatoms.
It is thought that the probability of crystal nucleation generation became 0 because the lifespan due to crystal nucleation was relatively short. Further, on the Si surface of the substrate (7), a flow rate of i(2) of 800
0scru1, S i I (4 no ura, value 0.16 s
ecm (dilution ratio S i l+4/ll2=2
Xl 0-5), the Si crystal grows at a rate of about 2nrn/min, and a complete CV that was previously impossible.
Selective viscous crystal growth at 800°C using the D method has become possible. Q Effects of the Invention In the present invention, since the etching reaction for removing Si on 5i02 is not used, selective crystal growth is reduced to 80%.
This is possible at low temperatures below 0°C. This can be seen from the fact that, as shown in the Examples, no crystal nuclei were observed to form on 5i02 even at 800°C. Furthermore, it has already been reported that crystal growth on the S1 substrate is possible at 800°C, and the present invention enables selective crystal growth at a low temperature of about 800°C using CVD, which was previously impossible. Furthermore, the present invention is not expected to be effective only in normal pressure CVD, but also in low pressure CVD, plasma CVD, optical CVD.
A similar effect is expected in VD and all CVD methods in which H2 gas can be introduced.

[Brief explanation of drawings]

Figure 1 shows the dilution ratio (Si114/H
2) and the density of crystal nuclei generated on the surface of 5i02. 1

Claims (1)

[Claims] (1) Using a chemical vapor deposition method that transports silicon hydride gas on a hydrogen carrier gas, selectively grows Si crystals only on the Si surface of a substrate that partially has a Si surface. The selective growth of Si crystals is characterized in that the dilution ratio of the silicon hydride gas by the carrier gas (volume ratio of silicon hydride gas/H2) is set to 5×10^-^5 or less. Law.