JPH10150030A - Film forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make the actual flow rate of TEOS gas supplied into a reaction chamber constant by providing a gas confluence part where the TEOS gas and O2 gas are confluent immediately before the reaction chamber in the film forming device, wherein the TEOS gas and O2 gas are supplied into the reaction chamber and a film is formed on a substrate. SOLUTION: A gas confluence part 16, wherein a TEOS-gas supply pipe 5 and an O2 -gas supply pipe 5 are connected and the TEOS gas and the O2 gas are confluent, is provided immediately before a reaction chamber 1, that is to say, immediately before an upper electrode 3. Thus, the gas confluence part 16 is made to approach the upper electrode 3, and the TEOS gas is mixed with the O2 gas at the direct upper part of the upper electrode 3, which is kept at about 80-100 deg.C. Then, as the gas approaches the reaction chamber 1, the pressure in the TEOS supply pipe 5 is decreased. The lower the pressure at the mixing point, the harder the condensation of the TEOS gas becomes to occurr. Thus, the condensation and the formation of a fog state of the TEOS gas at the mixing point and its vicinity with the O2 gas are prevented. The actual flow rate of the TEOS gas supplied between the electrodes 2 and 3 can be controlled at the constant value by an MFC 13.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a film forming apparatus for forming a film on a substrate, and more particularly to an apparatus for stabilizing an actual flow rate of a TEOS gas supplied to a reaction chamber.

[0002]

2. Description of the Related Art One of the semiconductor manufacturing processes is a plasma CVD (Chemica1 Va) for forming a predetermined film on a substrate.
(por Deposition) film forming process. In this method, a substrate is loaded into an airtight reaction chamber, and high-frequency power is applied while supplying a mixed gas between a pair of electrodes provided in the reaction chamber to generate plasma, and gas molecules in the mixed gas are generated. It is decomposed by the plasma to cause a chemical reaction to form a thin film on the substrate surface. Usually, film formation is performed while maintaining the reaction chamber at a constant pressure.

One of the apparatuses for performing such a plasma CVD film forming process is TEOS (tetraethoxysilane Si (O
There are _{C 2 H 5) 4) -SiO} 2 film forming plasma CVD apparatus, a mixed gas of TEOS and O ₂ (oxygen) is used as the mixed gas. At room temperature, O ₂ is in the gas phase, while TEOS is in the liquid phase. For this reason, the liquid TEOS is used as TEOS gas by vapor pressure after heating.

A conventional plasma CVD apparatus shown in FIG.
An upper electrode 3 and a lower electrode 2 are provided in a reaction chamber 1 as a pair of electrodes, and a substrate 4 is arranged on the lower electrode 2. The TEOS gas and the O ₂ gas are merged on the way to form a mixed gas. The mixed gas is supplied to the upper electrode 3 through the gas supply pipe 15, and the mixed gas is supplied from the gas dispersion hole 8 provided in the upper electrode 3. Is introduced to the third room. The upper electrode 3 and the lower electrode 2 are connected to a high-frequency power source 14 to apply a high frequency to the mixed gas introduced between the electrodes 2 and 3 to generate a plasma 10 and form a SiO ₂ film on the substrate 4. Is what you do.

However, in the current TEOS-SiO ₂ film formation, there is a problem that reproducibility of the film thickness is generally difficult to obtain in continuous film formation. This is because, in a conventional apparatus, when several tens of substrates are continuously formed under the same conditions, each for a fixed time, the TEOS-S
This is a problem that the thickness of the iO ₂ film varies. This variation is caused by the T supplied between the electrodes during film formation.
This indicates that the actual flow rate of the EOS gas is not constant.
The reason is that while the pressure of TEOS gas is high, O ₂
When mixed with the gas, the TEOS gas condenses or
It is considered that the OS gas becomes mist-like liquid TEOS and is processed without being reacted on the substrate, or a part of the mixed gas is thermally decomposed and deteriorated inside the gas supply pipe.
In any case, TEOS supplied between the electrodes
The flow rate is not constant, indicating that the gas composition (dilution ratio: O ₂ gas flow rate / TEOS gas flow rate) in the portion of the mixed gas between the electrodes is not constant.

Therefore, in order to solve the above-mentioned problem,
The methods described in JP-A-8-64541 and JP-A-4-35031 have been proposed.

Japanese Unexamined Patent Publication No. Hei 8-64541 discloses an outer tube for discharging TEOS gas to a reaction chamber,
_{(2) A} double tube with an inner tube coaxially disposed in the outer tube for discharging the gas to the reaction chamber side, and TEOS gas discharged through the outer tube is discharged through the inner tube. _This is intended to stabilize the actual flow rate of the TEOS gas by preventing the O ₂ gas from flowing back to the vaporizer through the outer tube, induced by the viscosity of the _two gases.

[0008] Further, Japanese Patent Application Laid-Open No. 4-35031 discloses a technique for stabilizing the actual flow rate of TEOS gas by further defining the optimum dimensional relationship between the outer tube and the inner tube. It was done.

[0009]

However, in any of the methods described in the above two publications, the actual flow rate of TEOS supplied between the electrodes during film formation is not constant, and the actual flow rate of TEOS on the substrate is not fixed. However, the problem that the thickness of the TEOS-SiO ₂ film formed in the above-mentioned method varies is not solved. Because, at the moment when the mixing of the TEOS gas and the O ₂ gas is started, the temperature or the pressure is in a state where the TEOS gas is easily condensed. For this reason, if the TEOS gas and the O ₂ gas are mixed and then guided to the reaction chamber through the gas supply pipe 15, the mixing point becomes far from the processing chamber.
This is because the condensation of the EOS gas is promoted, and the condensed TEOS adheres to the inside of the gas supply pipe.

In order to prevent this, a method of further heating the TEOS gas to increase the vapor pressure by increasing the temperature may be considered. In this case, thermal decomposition of TEOS is easily caused inside the gas supply pipe. Can not.

An object of the present invention is to solve the above-mentioned problems of the prior art by making the mixing point of TEOS gas and O ₂ gas as close as possible to the reaction chamber, and to solve the above-mentioned problems of the prior art. An object of the present invention is to provide a film forming apparatus capable of keeping the actual flow rate of gas constant. Another object of the present invention is to provide a film forming apparatus capable of controlling the composition of a mixed gas in a reaction chamber more constant.

[0012]

According to the present invention, a reaction chamber is provided with a TE.
In a film forming apparatus for supplying an OS gas and an O ₂ gas to form a film on a substrate, a gas converging section for converging a TEOS gas and an O ₂ gas is provided immediately before a reaction chamber. Here, the term "immediately before the reaction chamber" includes not only the area immediately before the reaction chamber serving as the housing but also the area immediately before the space where the film formation reaction occurs substantially in the reaction chamber. The TEOS gas is supplied to the reaction chamber through the TEOS gas supply pipe, and the pressure decreases as approaching the reaction chamber. Therefore, if a gas merging portion for merging the TEOS gas and the O ₂ gas is provided immediately before the reaction chamber, the TEOS pressure at the gas merging portion is low, so that TEOS is less likely to be condensed and TEO
Since the S gas is supplied to the reaction chamber as it is, the actual flow rate of TEOS supplied to the reaction chamber is stabilized.

In the present invention, a turbulence generating means for generating a turbulent flow may be provided downstream of the gas merging portion where the TEOS gas and the O ₂ gas merge. If a gas merging section is provided immediately before the reaction chamber, it becomes difficult to secure a pipe length for making the composition of the mixed gas uniform, but if a turbulence generating means is provided downstream of the gas merging section, TEOS gas and O ₂ Since the mixing with the gas is sufficiently performed, the gas composition can be made uniform without securing the pipe length.

Further, the TEOS gas supply pipe immediately before the gas merging portion where the TEOS gas and the O ₂ gas merge with each other is provided with a TEOS gas.
A mass flow controller for controlling the gas flow rate may be provided. By providing the mass flow controller near the reaction chamber, a pressure difference required for controlling the flow rate of the mass flow controller can be secured, and a larger flow rate of O ₂ can be supplied.

Further, it is preferable to provide a heating means for heating the O ₂ gas in the O ₂ gas supply pipe. TEO is getting hot
When the room temperature O ₂ gas is mixed with the S gas, the TEOS gas is easily condensed and adheres to the inside of the gas supply pipe.
When the heating means for heating the O ₂ gas is provided to heat the O ₂ gas, the TEOS gas is hardly condensed and TEOS does not adhere to the gas supply pipe.

Then, at the gas junction where the TEOS gas and the O ₂ gas merge, the flow of the TEOS gas is
_Two gases should be introduced at right angles. When the O ₂ gas is introduced at right angles to the flow of the TEOS gas, a necessary and sufficient mixed state is obtained.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the film forming apparatus of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic explanatory view of a plasma CVD apparatus according to the present embodiment.

In FIG. 1, since the configuration of the reaction chamber 1 is the same as that of FIG. 4, parts corresponding to those of FIG. 4 are denoted by the same reference numerals. T for supplying TEOS gas to the reaction chamber 1
The EOS gas supply pipe 5, separately disposed and O ₂ gas supply pipe 6 for supplying an O ₂ gas.

The liquid TEOS 12 is heated by the vaporizer 11 to form a TEOS gas. The vaporizer 11 has a temperature of 80-100.
° C and the TEOS vapor pressure are set at 30 to 90 Torr. The flow rate of the TEOS gas generated in the vaporizer 11 is controlled by a mass flow controller (MFC) 13, and is supplied to the reaction chamber 1 through a TEOS gas supply pipe 5 kept at 80 to 100 ° C.

On the other hand, the O ₂ gas is kept at 80 to 100 ° C. by a heat exchanger 7 as a heating means provided on the way.
₂ It is supplied to the reaction chamber 1 through the gas supply pipe 6. The O ₂ gas supplied to the reaction chamber is heated by the heat exchanger 7 because when the O ₂ gas at room temperature is mixed with the TEOS gas kept at 80 to 100 ° C, the TEOS gas is condensed into a mist and the gas is supplied. The reason is that the O ₂ gas supplied to the reaction chamber is adhered to the inner wall of the tube, but such TEOS disappears when the O ₂ gas supplied to the reaction chamber is heated.

Immediately before the reaction chamber 1, specifically, immediately before the upper electrode 3, the above-mentioned TEOS gas supply pipe 5 and O ₂ gas supply pipe 6 are connected to join the TEOS gas and the O ₂ gas. A part 16 is provided. In this way, the gas merging portion 16 is brought close to the upper electrode 3, and the TEOS gas is mixed with O ₂ immediately above the upper electrode 3 kept at 80 to 100 ° C. The reason that the TEOS gas is mixed with O ₂ immediately above the upper electrode 3 is that the pressure in the TEOS gas supply pipe 5 decreases as approaching the reaction chamber 1,
This is because the lower the pressure at the mixing point, the less the TEOS gas is condensed. This prevents the TEOS gas from condensing or becoming mist at and around the mixing point with the O ₂ gas, and the MFC 13 can control the actual flow rate of the TEOS gas supplied between the electrodes 2 and 3 to be constant. Becomes

By the way, when the mixing point of the TEOS gas and the O ₂ gas is brought closer to the upper electrode 3, it becomes difficult to secure a pipe length for making the composition of the mixed gas uniform and stabilizing the supply amount of the TEOS gas. For this reason, in the present embodiment, turbulence is generated at the mixing point to prevent the condensation and to sufficiently perform the mixing. That is, the turbulence generating means 9 for generating a turbulent flow is provided downstream of the gas confluence section 16 of the TEOS gas and the O ₂ gas. The turbulence generating means 9 is connected directly above the upper electrode 3, and the TEOS gas supply pipe 5 and the O ₂ gas supply pipe 6 are vertically connected to the turbulence generation means 9 and the upper electrode 3. The turbulence generating means 9 is constituted by a spiral or meandering gas pipe as shown in the illustrated example, and the mixed gas passes through the gas pipe in a spiral or meandering manner. As a result, a turbulent flow of the mixed gas is generated at the mixing point, and the gas composition in the portion of the mixed gas is equalized.
The size of the spiral or meandering gas pipe and the degree of mixing are not directly related, and the size of the spiral or meandering pipe may be any size that is equal to or larger than a normal 3/8 inch pipe.

The following experiment was conducted in order to confirm the effect of the heat exchanger 7 provided on the O ₂ gas supply pipe 6. Using a device equivalent to FIG. 1, a TEOS-SiO ₂ film was formed under the same film forming conditions at O ₂ gas temperature of 20 ° C. at normal temperature and 100 ° C. at high temperature, and a Vpp waveform representing a plasma state. Were compared. The result is shown in FIG.
As shown in FIG. 3A, Vpp at O ₂ temperature of 20 ° C.
In the waveform, the gas mixing point and T
TEOS gas is condensed in the EOS gas supply pipe 5 and TOS
EOS gas hardly flows. After that, since the TEOS gas supply pipe 5 is kept warm, the condensed TEOS has begun to be re-vaporized and supplied. In this state, the electrodes 2, 3
It can be seen that the actual flow rate of the TEOS gas during the period fluctuates, and the plasma becomes unstable. The pulsation of the Vpp waveform is because the gas composition in the portion of the mixed gas introduced between the electrodes 2 and 3 changes with time.
On the other hand, as shown in FIG. 3B, at an O ₂ temperature of 100 ° C., there is no change in the Vpp waveform from the start of the film formation, and it is understood that the plasma state is very stable.

Next, a modification of the film forming apparatus shown in FIG. 2 will be described. In the film forming apparatus shown in FIG. 1, since the MFC 13 is in the vaporizer 11 away from the upper electrode 3, the flow rate of the TEOS gas cannot be controlled more effectively, and the supply of the O ₂ gas at a larger flow rate cannot be supported. . Therefore, improvements have been made to cope with the supply of a larger flow rate of O ₂ gas. In FIG. 2, M
By moving the FC 13 to a position immediately above the upper electrode 3 to more effectively control the flow rate of the TEOS gas, the gas mixing in the gas junction 16 is optimized, and the O.sub.
It is possible to supply _two . This is bringing the MFC13 to the reaction chamber 1, when a large flow rate of O ₂ gas, T
This is because a pressure difference required for controlling the flow rate of the EOS gas can be secured, and the pressure regulation time until the flow rates of the TEOS gas and the O ₂ gas are stabilized at a predetermined pressure can be further improved.

As shown in FIG. 2, an O ₂ gas supply pipe 6 is connected to the TEOS gas supply pipe 5 at a right angle,
O ₂ gas is introduced at right angles to the TEOS gas that has passed through the FC 13. If O ₂ is introduced at right angles to the TEOS gas in this manner, the turbulence generating means 9 as shown in FIG. 1 does not need to be provided, and a necessary and sufficient mixing state can be obtained, so that the configuration can be simplified. There are advantages. Note that FIG.
The introduction angle θ of the O ₂ gas with respect to the TEOS gas shown in (b) is not limited to a right angle. The introduction angle θ is preferably 30
An angle of ~ 90 °, more preferably 45-90 °
And most preferably 90 °.

In the embodiment shown in FIG. 1 in which the turbulence generating means 9 is provided immediately above the upper electrode 3, the MFC 13 is
However, the MFC 13 can be moved toward the reaction chamber 1 with the turbulence generating means 9 remaining as in the embodiment of FIG. In addition, the present invention is not limited to a plasma CVD apparatus, but includes a decompression CVD apparatus and a normal pressure C
It can also be applied to VD devices.

[0027]

According to the present invention, the TEOS gas and the O ₂ gas are merged immediately before the reaction chamber so that the TEOS gas is hardly condensed.
The actual flow rate of gas can be controlled constantly. Further, by mixing the TEOS gas and the O ₂ gas by the turbulence generating means,
The composition of the mixed gas in the reaction chamber can be controlled more constantly.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view of a plasma CVD apparatus according to an embodiment of a film forming apparatus of the present invention.

FIGS. 2A and 2B are schematic explanatory views of a plasma CVD apparatus showing a modification, in which FIG. 2A is an overall view and FIG. 2B is a partial view of a gas supply pipe.

[Figure 3] is a diagram showing the relationship between O ₂ gas temperature and Vpp waveform, (a) shows the case of O ₂ gas temperature 20 ℃, (b) the O ₂
The case where the gas temperature is 100 ° C. is shown.

FIG. 4 is a schematic explanatory view of a conventional plasma CVD apparatus.

[Explanation of symbols]

1 reaction chamber 2 lower electrode 3 upper electrode 4 substrate 5 TEOS gas supply pipe 6 O ₂ gas supply pipe 7 the heat exchanger 9 the turbulence generating means 10 plasma 11 vaporizer 12 the liquid TEOS 13 MFC 16 gas meeting portion

Claims (5)

[Claims] In a film forming apparatus for supplying a TEOS gas and an O ₂ gas to a reaction chamber to form an SiO ₂ film on a substrate, a gas in which the TEOS gas and the O ₂ gas are combined immediately before the reaction chamber. A film forming apparatus comprising a junction. 2. The film forming apparatus according to claim 1, further comprising a turbulence generating means for generating a turbulent flow downstream of a gas merging portion for merging the TEOS gas and the O ₂ gas. 3. The film forming apparatus according to claim 1, wherein a mass flow controller for controlling a flow rate of the TEOS gas is provided in a TEOS gas supply pipe immediately before a gas junction where the TEOS gas and the O ₂ gas are merged. . Film forming apparatus according to any one of claims 4] O ₂ a heating means for heating the gas claims 1 provided in the O ₂ gas supply pipe 3. 5. The film formation according to claim 1, wherein the O ₂ gas is introduced at a right angle to the flow of the TEOS gas in the gas junction where the TEOS gas and the O ₂ gas merge. apparatus.