JPS61269307A - Cvd device - Google Patents

Abstract

PURPOSE:To control the thickness of films on plural substrates with higher accuracy by providing a means to preheat reaction gas entering into a nozzle tube so as to make the distributed amount of flow at each hole of nozzles suitable. CONSTITUTION:A multi-porous nozzle tube 8 and a construction of multiple-unit tubes through which reaction gas and cooling gas are flown. A preheating means 10 is provided to preheat the reaction gas to be supplied to the nozzle tube 8. Then, the reaction gas is injected into a substrate reaction chamber on each stage with the nozzle tube 8 through piping. The reaction gas is discharged through a suction pipe 9. Cooling gas is supplied through piping 6. The preheating temperature is controlled at a constant value with the preheating means 10, thereby providing suitable distribution amount of flow at each holes of the nozzle, with highly accurately controlled thickness of films on plural substrates.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention comprises a double-pipe gas-cooled porous nozzle pipe for uniformly distributing reaction gas of a CVD apparatus including epitaxy,
The present invention relates to a CVD apparatus including epitaxy that performs suitable gas flow distribution when a reaction gas has a temperature gradient within a nozzle pipe.

[Background of the invention]

CVD equipment including epitaxy is required to have high throughput and high precision film thickness performance against the backdrop of mass production of semiconductor products in recent years. When processing multiple boards at the same time,
In order to control the film thickness on each substrate, it is necessary to keep the flow rate and concentration of the reaction gas supplied onto the substrate constant. When dispersing reactive gas using a porous nozzle pipe, it is necessary to make the flow rate uniform from the porous holes ejected from the nozzle pipe, and to suppress precipitation within the nozzle pipe to avoid concentration changes. In particular, when the reactant gas supplied at room temperature is in the temperature run-up region where it is gradually heated to a high temperature in the reactor, the flow rate ejected from the nozzle tube porous hole is likely to become uneven due to the influence of temperature changes. There is a technical problem in equalizing the flow rate of each hole ejected from a multi-hole nozzle pipe with a temperature distribution.

There are several possible ways to solve the above problems. For example, one method is to vary the nozzle pore diameter in the gas flow direction so as to obtain a uniform flow rate from each nozzle hole.
It is important to accurately process the quartz material for the nozzle. This type of device will be explained in more detail below.

Generally, CVD (chemical vapor deposition) including epitaxy is performed by heating a reaction gas to a high temperature. In principle, it is explained by the chemical equilibrium of reactive gases, and there are many papers on this subject, but the earliest paper was published by R.F. Lever in IBM. Research of Development (IBMRes, Develop) Volume 8 46
There is a paper on silicon epitaxy on page 0 (1972). This can be expressed schematically as shown in Figure 3. Below the temperature at which the supply concentration intersects the supersaturation curve, no reaction gas is deposited on the solid surface, but above that temperature, reactions occur not only on the silicon substrate but also on the solid surface. Precipitation on solid surfaces such as containers and gas phase thermal decomposition occur. If deposition occurs on a surface other than the substrate, the concentration of the reaction gas changes, resulting in deterioration of the CVD film thickness distribution on the substrate or clogging of the gas flow path.

B-E-Deal (B, E, Deal) uses a double structure of the nozzle tube and cools it with N2 gas to avoid high-temperature precipitation of the reaction gas inside the nozzle tube when the reaction gas is supplied through the nozzle. (Journal・
of Electrochemical Society (J,
Electro chew, Soc.

) 109, No. 6, p. 514 (1962)). Furthermore, in Japanese Patent Application Laid-open No. 55-24424, Endo et al. proposed gas cooling of the reaction gas flowing in the nozzle tube, similar to Diehl, using a nozzle with a composite tube structure extending to the vicinity of multiple substrates. However, all of these nozzles are single-hole nozzles.

In recent years, high-throughput epitaxy equipment has been devised for the purpose of processing a large number of substrates simultaneously (Journal by V.N.S. Ban).
Of Crystal Growth (J, Crystal
Growth) Vol. 45, p. 97 (1978)).

Here, a porous nozzle is used to spray fresh reactive gas onto each substrate. In addition, in an electric furnace type hot wall epitaxy apparatus that processes multiple substrates simultaneously, the present inventors also conducted a source gas flow through the main stream of the reaction tube to avoid the precipitation of reaction gas in the nozzle tube, and doping was carried out from the porous nozzle. Only gas is distributed (Japanese Patent Application Laid-open No. 19316/1983).

However, with multi-hole nozzles, there is a pressure loss in the gas flow direction, and the flow rate of the nozzle ejected from the hole tends to be uneven. One of the basic technologies is to uniformly eject it from a multi-hole nozzle.

There have already been experiments and theoretical studies on flow distribution from multi-hole nozzles, and there is also a description in the handbook (Chemical Engineering Handbook).
(Revised 4th edition) 129 pages Maruzen (1978)). To quote for later discussion, the pressure drop is also when there is a one-layer flow. Nozzle flow rate, where D = nozzle pipe diameter, u = flow rate of fluid in the nozzle pipe, n = nozzle hole interval, μ = viscosity coefficient, gc = gravity conversion coefficient, ζb = branching loss coefficient of refraction, ζS = branching of straight section Loss factor, n = number of nozzle holes, Qi = mini nozzle body fluid flow rate rl = nozzle hole diameter, un = nozzle hole fluid flow rate, P =
Nozzle pipe internal pressure, P0 = fluid pressure at nozzle hole exit, C =
is the flow coefficient.

Generally, there is a pressure loss in the gas flow direction within the nozzle pipe, so the amount of ejection decreases downstream. However, depending on the nozzle pipe diameter, nozzle hole diameter, and type of fluid, the opposite phenomenon may occur, that is, the ejection amount increases toward the downstream. However, if the nozzle pipe diameter is made as large as possible and the nozzle hole diameter is made as small as possible, the pressure loss will be small compared to the total pressure, and uniform distribution can be expected in an isothermal system.

However, in a CVD apparatus or the like, a reaction gas at room temperature is supplied to a reactor, so the temperature of the reaction gas changes within the nozzle pipe, and a so-called temperature run-up region occurs. As shown in equation (2), the nozzle hole flow rate is a function of the gas density ρ, so even under conditions where the pressure inside the nozzle pipe is nearly uniform, an uneven distribution state due to temperature distribution is likely to occur. In fact, when a source gas of 5 to 20 Q/ff1 inch was passed through a nozzle pipe with a nozzle diameter of 8 mm, nozzle holes 211I11, and nozzle holes number 19, the distributed flow rate was obtained with an accuracy of 5% at room temperature, but the nozzle When the tube was heated from room temperature to 500° C., the distribution accuracy deteriorated to 30%.

On the other hand, in the case of a gas-cooled double-tube structure, the temperature distribution of the cooling gas and reaction gas changes depending on the wall temperature, flow rate, etc. Basically, the heat transfer form is similar to that of a double tube air heat exchanger, but
A multi-hole nozzle like the one in question is different in that the mass velocity of the fluid is different within the nozzle pipe. Expressed theoretically, the basic equation for heat balance is as follows.

Cooling Gas Reactant Gas where W' = Mass velocity of the cooling gas, W n = Gas mass velocity in the nozzle tube, T' = Cooling gas temperature, T = Opposite gas temperature, T, = Wall temperature of the double outer tube. , r'=inner diameter of outer tube,
r=inner diameter of inner tube, h'=heat transfer coefficient in outer tube annular path, U=
This is the overall heat transfer coefficient between the inside and outside of the inner tube.

The total heat balance in and out is expressed as the amount of heat transferred from the wall = the amount of heat removed by the cooling gas + the sensible heat removed by the gas ejected from the nozzle orifices.

The temperature distribution is formed while satisfying the above relationship, and the key to solving the problem is to form a temperature distribution as uniform as possible using the cooling gas.

In addition, the upper limit of the gas temperature in the nozzle tube must not exceed the deposition temperature, and if the gas temperature in the nozzle tube is lowered too much, the reaction rate on the substrate surface may become uneven, so there is a lower limit, and the nozzle ejected gas The problem is the flow rate conditions for the cooling gas that will appropriately adjust the temperature of the cooling gas.

[Purpose of the invention]

The object of the present invention is to process a large number of substrates simultaneously in a CVD apparatus including epitaxy, in which a room temperature reactant gas is distributed into the reactor by a multi-hole nozzle.

It is an object of the present invention to provide an apparatus capable of ejecting a uniform amount of reaction gas from each nozzle hole, thereby making the thickness of each film uniform on a large number of substrates.

[Summary of the invention]

When the reaction gas is gradually heated in the nozzle pipe and there is a temperature gradient, the amount of ejection from each nozzle hole will be uniformly distributed even if the nozzle pipe diameter or nozzle hole diameter is sequentially changed in the gas flow direction and the pressure inside the pipe is kept constant. Not done. Furthermore, even if the gas cooling flow rate is changed in a multi-hole nozzle of the double-pipe air cooling type, a uniform temperature distribution of the reactant gas within the nozzle tube is not formed, and the distribution ratio of the nozzle flow rate is poor as shown in FIG. If you look closely at the diagram, you can see that the distribution ratio decreases in the part where the gas at room temperature is heated.1 The inventors have found that one method is to preheat the gas and raise its temperature before the reaction gas enters the nozzle pipe. I predicted that. Therefore, it has been found that by varying the temperature at the nozzle pipe inlet as shown in FIG. 5, the distribution flow rate of the nozzle hole can be improved. The higher the preheating temperature, the better, but the upper limit is the precipitation temperature. Furthermore, as shown in FIG. 6, it has been found that when the cooling gas flow rate is increased, favorable conditions tend toward the larger nozzle hole diameter. The larger the nozzle hole is, the better, considering the machining accuracy. In addition, if the nozzle hole is small, the pressure inside the nozzle pipe increases, and when using a low vapor pressure reaction gas such as 5iH2CEL, which is filled in a liquid state, there is a limit to the nozzle pipe pressure. Therefore, in this case as well, a larger nozzle hole diameter is desirable.

As the cooling gas, for example, N2. N2 etc. are used.

As shown in FIG. 7, it is preferable to use N2, which has good cooling efficiency, but in this case, a sufficient leak test is required to suppress leakage from the quartz nozzle tube to the reaction system as much as possible.

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a diagram showing the reactor structure of a multi-stage wafer rotating atmospheric pressure hot wall type silicon epitaxial apparatus according to an embodiment of the present invention, and FIG. 2 is a system diagram of the apparatus shown in FIG.

1 is a quartz bell jar, in which a heating susceptor 2 is placed to create a uniform temperature atmosphere at a reaction temperature of 1100° C. for a large number of substrates 4. 6. A film with a uniform thickness is also formed on the substrates 4. In order to
The structure is such that it is housed in a reactor and rotates within the reactor. Silicon source gas 5iCn4 or Si
Reactive gases such as HZ CO2, carrier gas H2 and doping gas PH pass through the piping and enter the porous nozzle pipe 8.
The liquid is ejected into the substrate reaction chambers of each stage. The reaction gas is discharged via suction pipe 9. The porous nozzle pipe 8 has a double-pipe gas cooling nozzle structure, and cooling N2 is supplied through the pipe 6. There is a preheater 10 before the reaction gas reaches the nozzle pipe, and the preheating temperature of 600° C. is measured with a precision thermometer and controlled to a constant high temperature. Depending on the flow rate of the reaction gas, the cooling gas may also be heated by the preheating heater 11.

12 is a reaction gas introduction pipe, 13 is a high frequency oscillator, 14 is a wandering gas scrubber, and 15 is a thermometer with a regulator. The reaction time was 20 minutes, and silicon films with a film thickness of 10 μIn were simultaneously formed on multiple substrates.

According to this example, S x H2Cnz =0.2 Q
/win, H2=2011 /win, P H,
=0. When the reaction gas at OOI Q/min was distributed to each stage where a large number of substrates were set through a double-pipe gas cooling nozzle with 20 nozzle holes, the reaction gas at room temperature was supplied without preheating. When the total film thickness accuracy is ±1
5%, but when preheated to 600℃, ±3%
A film thickness accuracy of . Further, even in the case of preheating, no precipitation was observed inside the nozzle pipe, and since there was no blockage inside the nozzle pipe, there was no need to take it out for cleaning, and continuous operation was possible.

It goes without saying that the present invention is not limited to the above embodiments, and that various modifications may be made within the scope of the claims.

〔Effect of the invention〕

As explained above, the present invention provides a means for preheating the reaction gas entering the nozzle pipe, thereby improving the distribution flow rate of the nozzle hole and controlling the film thickness on a large number of substrates with high precision. It has the effect of

[Brief explanation of drawings]

FIG. 1 is a diagram showing the structure of a multi-stage wafer rotation type silicon epitaxial device according to an embodiment of the present invention, and FIG.
Figure 3 is a schematic diagram of the temperature-concentration curve showing the chemical equilibrium concentration and supersaturation concentration showing precipitation on Sio2, Figure 4 shows the gas temperature distribution in the double tube nozzle, Figure 3 shows the precipitation situation in the nozzle pipe from the deposition temperature determined by the precipitation temperature, Figure 5 shows the distribution flow ratio of the nozzle hole and the temperature distribution of the reactant gas with the preheating temperature as a parameter, and Figure 6 the nozzle hole diameter as a parameter. FIG. 7 is a diagram showing an example in which the nozzle distribution flow rate ratio is improved by preheating. 1... Quartz bell jar of the reactor 2... Susceptor for high frequency heating 3... High frequency coil 4... Wafer 5... Rotating wafer support stand 6... Cooling gas introduction pipe 7... Outer tube 8 of double tube nozzle... Inner tube of double tube nozzle, nozzle tube 9 for reaction gas
... Reaction gas discharge pipe 10 ... Reaction gas preheating heater 11 ... Cooling gas preheating heater 12 ... Reaction gas introduction pipe 13 ... High frequency oscillator 14 ... Exhaust gas cleaning device

Claims (1)

[Claims] In a CVD apparatus including an epitaxy system that is equipped with a porous nozzle pipe that allows a reaction gas to flow over each substrate and forms thin films on multiple substrates at the same time, the nozzle pipe allows the reaction gas to flow through the reaction gas and a cooling gas for the reaction gas. A CVD apparatus characterized in that it has a composite pipe structure for flowing, and is equipped with preheating means for preheating the reaction gas entering the nozzle pipe.