JPS6218708A - Growing method for silicon carbide layer - Google Patents

Abstract

PURPOSE:To grow an SiC layer having good bondability by CVD-reacting with H2 gas as carrier while regulating the ratio of SiHCl2 to SiCH3Cl3 or Si(CH3)3 Cl of reaction gas. CONSTITUTION:The flow rate of SiCH3Cl3 or Si(CH3)3Cl is initially set to zero on an Si substrate 1, and only SiHCl3 is epitaxially grown as reaction gas to grown an Si layer 2. Then, the flow rate of the SiCH3Cl3 or Si(CH3)3Cl is raised as time goes, thereby eventually growing an SiC layer 3. Thus, a transferring layer which gradually transfers from the layer 2 to the layer 3 is formed to epitaxially grow the layer 3 having good bondability. Thus, the mass-production of SiC growth can be performed.

Description

[Detailed Description of the Invention] [Summary] A chemical reaction is performed on a silicon substrate by sequentially changing the composition ratio so that trichlorosilane is used as a reaction gas at first, and monomethyltrichlorosilane or trimethylmonochlorosilane is used as a reaction gas at the end. A method of epitaxially growing a semiconductor layer that gradually transitions from silicon to silicon carbide on a silicon substrate using vapor phase growth.

[Industrial application field]

The present invention relates to a method for growing a silicon carbide layer with good adhesion on a silicon substrate.

Silicon carbide (hereinafter abbreviated as SiC) is a much higher insulator than silicon (hereinafter abbreviated as Si) with a melting point of 2700°C or higher, and the width of the forbidden band is 2.20eV, which is 167e compared to that of Si.
It is warmer and larger than V, and chemical vapor deposition (CVD)
Since semiconductors with p-type and n-type conductivity can be obtained by methods such as the method (method), they are attracting attention as future semiconductor materials.

That is, by using such a SiC single crystal, it becomes possible to develop lasers that emit light in the visible region, bipolar transistors that can operate at high temperatures, and the like.

Here, like Si, SiC single crystal can be grown by the pulling method or vapor phase epitaxial growth method, but (1) the cost is high because the processing temperature is high.

■It is difficult to obtain a high-quality single-crystal substrate.

■Large diameter substrates are currently not available.

There are problems such as.

Therefore, as a method to solve these problems, the practical use of a manufacturing method of heteroepitaxial growth on a Si substrate is being promoted.

[Conventional technology]

There are two types of SiC: cubic and macrogonal, and the former has a β
-3iC, and although the latter is distinguished from α-5tC,
β-5iC has an electron mobility of 1000 at 300K.
cm2/ Vsec and α-5iC 460cm2/
Since it is superior to Vsec, β is suitable for semiconductor devices.
-5iC is used exclusively.

Now, conventionally, β-5iC (hereinafter abbreviated as 5iC) is
) is used as a method of growing carbonization.

This method uses a chemical vapor deposition device (CVD device),
Supplying a hydrocarbon such as propane (C3H8) at normal pressure while heating the i-substrate to a high temperature of 1340 to 1360°C,
This is a method of growing SiC on a Si substrate by thermal decomposition.

This growth mechanism is that S1 atoms diffuse to the substrate surface through lattice defects in the SiC film, and carbon (C) decomposes on the surface.
) It has been confirmed that SiC grows by bonding with atoms.

Although this method allows crystal growth up to a thickness of several micrometers, as the thickness of the film increases, the crystallinity deteriorates, and good crystallinity is limited to a thickness of about 1 micrometer.

Another problem with this method is that it is not suitable for mass production.

In other words, when the CVD temperature reaches a high temperature of 1,300°C or higher, the furnace material and heating element are limited, resulting in poor workability, and the quality and yield are reduced because high-precision temperature control is no longer possible. .

Also, CV of flammable hydrocarbons such as C31 (8) at normal pressure.
A large exhaust system is required to supply equipment D.
There is also a risk of explosion.

Furthermore, a problem with the SiC film obtained by heteroepitaxial growth in this manner is that it is easily peeled off from the substrate.

In other words, the lattice constant of both is 25°C and Si is 5.4306
Man.

Since SiC has a mismatch of 4.349 and approximately 20%, peeling is likely to occur, and improvements were needed.

[Problem that the invention seeks to solve]

As described above, the conventional carbonization method is not suitable for mass production processes, and there is a problem in that peeling easily occurs between the carbonization method and the Si substrate.

[Means for solving problems]

The above problem can be solved by attaching a Si substrate to a chemical vapor deposition apparatus, using hydrogen gas as a carrier while reducing the pressure inside the apparatus, and initially using a reaction gas consisting of trichlorosilane and monomethyltrichlorosilane or trimethylmonochlorosilane to A chemical vapor phase reaction is carried out by supplying the reaction gas onto a heated Si substrate while changing the composition ratio of the reaction gas such that chlorosilane is used as the component gas and monomethyltrichlorosilane or trimethylmonochlorosilane becomes the final component gas. was carried out, and the composition was changed from Si to SiC on the Si substrate.
This problem can be solved by a method of growing a semi-dedicated layer, which is characterized by forming an epitaxially grown layer that gradually changes.

[Effect]

The present invention uses monomethyltrichlorosilane (SiCH3CH) or trimethylmonochlorosilane (Si( In addition to using CH3)3C1), trichlorosilane (SiHClx) is used to improve adhesion to the Si substrate.

That is, the present invention uses hydrogen (H2) as a carrier and reactant gases 5illC13 and 5iCH3C13 or Si
(CH] ) 3 CVD without adjusting the ratio with C1
By performing the reaction, only St was initially placed on the St substrate,
Finally, the above objective formula is shown by epitaxially growing the composition ratio so that only SiC grows.

That is, the flow rate of 5iCH3C13 or 5i(CH3) 3 C1 is initially set to zero on the Si substrate 1, and 5iHC1
By performing epitaxial growth using only 3 as a reaction gas, 5iFJ2 shown by the diagonal line downward to the right in FIG.

Therefore, in this intermediate region, Si and SIC coexist depending on the flow rate ratio.

Figure 2 shows the transition of the composition ratio of both during CVD growth, showing that 5iCIl 3C1 at the CVD starting point
The flow rate of 3 is zero, but as the processing time passes, the flow rate of 5iC1
The flow rate of 13C10 or 5i(CI+3)3C1 increases, and after a certain period of time, the SiC layer 3 is filled with only 5iCH3C13 or 5i(CH3)C1 as a reaction gas.
growth will take place.

By creating a transition layer that gradually changes from the Si layer 2 to the SiC layer 3 in this manner, it is possible to epitaxially grow the SiC layer 3 with good adhesion.

〔Example〕

The reaction gas for 5illC1 was prepared by passing H2 gas through (bubbling) liquid 5iHCh to saturate it, and the flow rate was adjusted to a range of 10 to Occ/min.

Also 5iCH3Cl or 5i(CI+3) 3
Similarly, the reaction gas of C1 is bubbled with H2 gas to generate 0
It was changed in the range of ~1.0β/min.

In addition, H2 was used as the carrier gas, and the flow rate was 61
Fixed at /min.

Next, we used a Si substrate with a diameter of 4 inches and a thickness of 500 μI, and after performing the same surface treatment and cleaning treatment as conventional methods, we placed it in a CVD device and reduced the pressure, and while flowing a carrier gas, we Initially, 5iHCI3 was heated to IQcc/min and 5iCH3 was heated while maintaining the substrate temperature at 1000℃.
Cl or 5i (Cll), the flow rate of CI is zero,
Air pressure was maintained at 2 torr.

Thereafter, as shown in Fig. 2, the flow rate of 5iHC13 is reduced and 5iC)13 C13 or 5i(Cl3)3
CvD growth was performed alternately for 20 minutes by increasing the flow rate of C1, and a film with a thickness of approximately 8000 was grown.

Note that 5iHC after 20 minutes from the start of CVD growth.
The flow rate of No. 13 was adjusted to zero.

Figure 3 shows the infrared absorption characteristics of the CVD film obtained in this way, with admittance (relative absorption sensitivity) on the vertical axis and 1/wavelength (Kaiser) on the horizontal axis. .

As can be seen from the figure, significant absorption is shown at 800 cm-', which indicates that 5i-C bonds are formed on the substrate surface.

By epitaxially growing the Si substrate 1 to the SiC layer 3 while sequentially changing the composition, one of the grown layers is grown.
AIJ ZM is gone, and 5iHc is used as a reaction gas.
13 and 5i CII 3 , C13 or 5i (CH:l
) 3 C1, it becomes possible to grow SiC at a temperature of about 1000° C. with good workability.

〔Effect of the invention〕

As mentioned above, conventional SiC growth is 1340~136
This method was not suitable for mass production because it was carried out at a high temperature of 0° C., which is difficult to work with, and at normal pressure of the reaction gas, but by carrying out the present invention, mass production of SiC growth becomes possible.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing the structure of a grown layer according to the present invention, FIG. 2 is a schematic diagram showing the composition ratio of reactive gases, and FIG. 3 is an infrared absorption sensitivity diagram of the grown layer. In the figure, 1 is a Si substrate, 2 is SiN, 3 is 5iC
Jiii. It is.

Claims (1)

[Claims] The silicon substrate is mounted in a chemical vapor deposition apparatus, and hydrogen gas is used as a carrier while reducing the pressure inside the apparatus, and the partial pressure of monomethyltrichlorosilane or trimethylmonochlorosilane increases with time compared to the partial pressure of trichlorosilane. Controlling the reactive gas in such a manner, supplying the reactive gas onto a heated silicon substrate to perform a chemical vapor phase reaction, and forming an epitaxial growth layer on the silicon substrate whose composition gradually changes from silicon to silicon carbide. A method for growing a silicon carbide layer characterized by: