JPH0964025A - Manufacturing method for semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device having a silicon oxide film whose film quality in the depth direction is uniform and which is superior in coverage as an inter-layer insulation film, by film-forming until the temperature of a substrate in a chamber becomes set temperature, while flow rate of raw material gas is gradually increased. SOLUTION: A silicon oxide film is formed an a semiconductor substrate in a chamber in a plasma CVD method using organic system raw material gas, for manufacturing a semiconductor device. At this time, film formation is done until the temperature of the substrate in the chamber becomes set temperature, while flow rate of the raw material gas is gradually increased. For example, first, He acting as diluting gas and O2 acting as auxiliary material gas are introduced into the chamber, and the inside of chamber is adjusted at a specified pressure. Then TEOS introduction and RF discharge are started at the same time, the TEOS flow rate is adjusted until reaches set flow rate with the use of lamp up method. The gradient of the lamp up is about TEOS set flow rate × 0.1per second, and lamp up time is about 10 seconds.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor device, and more particularly to plasma CVD using an organic source gas.
The present invention relates to a method for forming a silicon oxide film by the method.

[0002]

2. Description of the Related Art Various insulating films are used in the manufacturing process of semiconductor devices. Along with the shrinking of wiring intervals and the progress of multi-layering due to the high integration of semiconductor devices, an interlayer insulating film that can be formed at a low temperature and has excellent coverage has been required to flatten the step portion. . As an insulating film satisfying this condition, silicon oxide (SiO ₂ ) formed by a plasma CVD method using an organic source gas such as TEOS (tetraethyl orthosilicate)
There is a membrane.

In this method of forming a SiO ₂ film, a raw material gas (TEOS and O ₂ ) is introduced into the chamber to obtain about 350
This is a method of depositing a SiO ₂ film on the substrate by heating the substrate to a film forming temperature of ° C and making the source gas into a plasma state by RF discharge while keeping the pressure in the chamber at a predetermined pressure. Further description will be given below with reference to the drawings.

FIG. 4 is a timing chart of gas introduction and RF discharge when forming a SiO ₂ film using TEOS.
In forming the SiO ₂ film, first, O ₂ as a sub-source gas and He as a diluting gas are introduced into the chamber, and then the pressure in the chamber is adjusted to a predetermined pressure. After the pressure in the chamber becomes stable, TEOS is introduced into the chamber and RF discharge is started at the same time. The time required for adjusting the pressure in the chamber and stabilizing it varies depending on the type of the CVD apparatus, but it takes about 5 seconds for a single-wafer type apparatus, so TE
The introduction of the OS and the RF discharge are started about 5 seconds after the introduction of O ₂ and He. During the film formation of SiO ₂ , gas introduction and RF discharge are continuously performed, and when the film formation time has elapsed, RF discharge and all gas introduction are stopped at the same time.

[0005]

SiO formed by the plasma CVD method using the above-mentioned conventional organic source gas.
_{The two} films did not have uniform film quality in the depth direction, and the film formed especially in the initial stage of growth had a rough film quality. Therefore, if a through hole is formed by using this SiO ₂ film as an interlayer insulating film between wirings, there is a problem that a good through hole shape cannot be obtained. Further, when the SiO _{2 layer} is thinly formed, defects such as pinholes and weak spots occur due to nonuniform film quality, and the breakdown voltage is deteriorated.

[0006] The reason why the quality of the SiO ₂ film at the initial stage of growth is rough as described above is that the initial stage of growth (at the start of RF discharge) is in the transition period in which the reaction temperature rises.
_It is considered that the oxidation by ₂ was insufficient. At the initial stage of film growth, the flow rate of TEOS to be introduced overshoots the set flow rate, so that the SiO ₂ film becomes a rough film.

When a silicon-based thin film (silicon oxide, silicon nitride, hydrogenated amorphous silicon) is formed by the CVD method using SiH ₄ as a main source gas, the difference in the film quality of the lower layer is eliminated and the overall film quality is made uniform. In order to
JP-A-4-123424 discloses a method in which a diluting gas is first introduced into a chamber, the substrate temperature and pressure are adjusted, RF discharge is started, and then a source gas is introduced into the chamber.

However, when this method was tried by a CVD method using an organic source gas, a sufficiently uniform SiO ₂ film could not be obtained. Moreover, this method has a drawback that the throughput is lowered because the film cannot be grown until the substrate temperature becomes constant. Further, a SiO ₂ film using SiH ₄ as a main raw material gas has poor coverage and is not suitable as an interlayer insulating film.

An object of the present invention is to provide a method of manufacturing a semiconductor device having a silicon oxide film having uniform film quality in the depth direction and excellent coverage as an interlayer insulating film.

[0010]

A method of manufacturing a semiconductor device according to the present invention is a method of manufacturing a semiconductor device, wherein a silicon oxide film is formed on a semiconductor substrate in a chamber by a plasma CVD method using an organic source gas. It is characterized in that the film is formed while gradually increasing the flow rate of the source gas until the temperature of the substrate in the chamber reaches a set temperature.

[0011]

In the conventional film forming method, first, in the chamber,
After introducing O _{2 as} a sub-source gas and He as a diluting gas to stabilize the pressure, TEOS is introduced, and at the same time R
Since the F discharge is performed, the wafer surface temperature (reaction temperature) rises with the start of plasma discharge and becomes saturated at a certain temperature. Since film formation is performed even while the wafer surface temperature rises, the film quality of the SiO ₂ film differs between the wafer temperature rise region at the initial stage of growth and the wafer temperature saturation region thereafter. That is, since the growth temperature is low, the film in the initial stage of growth becomes a rough film, and when a through hole is formed in this SiO ₂ film, its shape is deteriorated, and defects such as pinholes and weak spots are generated, resulting in the characteristics of the semiconductor device. Becomes unstable.

In the present invention, first, O _{2 as} a sub-source gas and He as a diluting gas are introduced into the chamber to adjust the pressure. Then, at the same time as the RF discharge, TE which is the main raw material
By introducing while gradually increasing (ramping up) the OS flow rate, the film quality change due to the temperature rise in the chamber occurring at the initial stage of growth is corrected.

As shown in FIG. 3, the higher the flow rate of TEOS during film formation, the coarser the quality of the deposited SiO ₂ film becomes, and the higher the etching rate becomes. That is, as for the flow rate of TEOS to be introduced, the lower flow rate is SiO 2.
_{Since the} film quality of the _two films can be made dense, the roughness of the film quality due to low temperature can be corrected. Therefore, until the wafer temperature rises and becomes constant, T
By gradually increasing the flow rate of EOS, the film quality of the SiO ₂ film at the initial stage of film formation can be made almost the same as that of the SiO ₂ film when the wafer temperature is constant. It is possible to prevent overshoot by gradually increasing the flow rate of TEOS, which is the main raw material.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described with reference to the drawings. FIG. 1 is a timing diagram of gas introduction and RF discharge for explaining an embodiment of the present invention, and FIG. 2 is a configuration diagram of a plasma CVD apparatus used in the present embodiment. The configuration of the device will be described below.

Inside the chamber 1, there are provided a susceptor 3 with a heater for placing a wafer 11 and a shower plate 2 facing the susceptor 3 for introducing a raw material gas. The inside of the chamber 1 is maintained in a vacuum state (3 to 4 Torr) by the vacuum pump 4. TEOS which is the main raw material gas is TE heated to about 80 ° C by a heater.
The mass flow controller 6 controls the flow rate from the OS supplier 7 and supplies the shower plate 2 with the flow rate. TEO
Similar to S, O ₂ as a sub-source gas and He as a carrier (diluting) gas are simultaneously introduced into the chamber 1. The valves 8 and 9, the mass flow controller 6 and the pipe 10 to the chamber 1 connected to them are TEO.
It is heated by a heater to prevent S liquefaction. Again 5
Is an RF oscillator, the shower plate 2 and the susceptor 3
Plasma is generated between them.

When a SiO ₂ film is formed on the wafer 11 by using the CVD apparatus having the above-described structure, first, as shown in FIG.
Introducing e and O ₂ which is the auxiliary material gas, the inside of the chamber 1 is adjusted to a predetermined pressure. The time from the introduction of He and O ₂ until the pressure becomes stable depends on the type of the apparatus, but in the case of the single wafer plasma CVD apparatus of the present embodiment, it takes about 5 seconds. Therefore, the introduction of TEOS and the RF discharge are started 5 seconds after the introduction of O ₂ and He gas.

Introduction of TEOS and RF discharge are started at the same time, or TEOS is introduced after the start of RF discharge. TE
The OS flow rate is adjusted using a ramp-up method until the set flow rate is reached. For example, the slope of this ramp up is
A TEOS setting flow rate of about 0.1 per second is sufficient,
The ramp-up time at this time requires about 10 seconds.
This time is almost the same as the time until the temperature of the wafer in the initial stage of growth reaches the saturation temperature.

During the SiO ₂ film formation by TEOS, gas introduction and RF discharge are continuously performed, and when a predetermined film formation time elapses, first, the TEOS flow rate as the main raw material gas is adjusted by the air operation valve 9. It is desirable to stop and discharge the residual TEOS in the pipe 10 and then simultaneously stop O ₂ , He and RF discharge. TEO, the main source gas
The time from the stop of the S flow rate to the stop of the RF discharge varies depending on the pipe length, but about 5 seconds is sufficient.

By using the above-described film forming method, the SiO ₂ film in the initial stage of growth is hardened, and the roughness of the film quality due to the low temperature in the initial stage of growth can be corrected, and the film quality in the depth direction becomes uniform. Therefore, even if this SiO ₂ is used as an interlayer insulating film, a good through hole shape can be obtained. Further, it is possible to form an oxide film having a sufficient breakdown voltage without causing defects such as pinholes and weak spots. Moreover, since the film can be formed from the low temperature state, the throughput is improved.

In the above embodiment, the case where TEOS is used as the organic source gas has been described.
TS (octamethyl cyclo tetra siloxane:
Si ₄ C ₈ H ₂₄ O ₄ ) can be used as well as TEOS. Although O ₂ was used as the auxiliary material gas, the same effect can be obtained by using O ₃ .

[0021]

As described above, according to the present invention, when the silicon oxide film is formed by the plasma CVD method using the organic source gas, the flow rate of the source gas is gradually increased until the substrate temperature reaches the set temperature. Since the film quality can be made dense at the initial stage of film formation by performing the film formation in this way, there is an effect that the film quality in the depth direction can be made uniform without lowering the throughput. Therefore, when this silicon oxide film is used as an interlayer insulating film, excellent coverage can be obtained and a good shape can be obtained even when a through hole is formed.

[Brief description of drawings]

FIG. 1 is a timing chart of gas introduction and RF discharge for explaining an embodiment of the present invention.

FIG. 2 is a configuration diagram of a CVD apparatus used in the embodiment of the present invention.

FIG. 3 is a diagram showing the TEOS flow rate dependence of the etching rate of a SiO ₂ film.

FIG. 4 is a timing chart of gas introduction and RF discharge in the case of forming a conventional organic silicon oxide film.

[Explanation of symbols]

 1 Chamber 2 Shower Plate 3 Susceptor 4 Vacuum Pump 5 RF Oscillator 6 Mass Flow Controller 7 TEOS Supplyer 8 Air Operation Valve 9 Air Operation Valve 10 Piping 11 Wafer

Claims (3)

[Claims] 1. Plasma CVD using an organic source gas
In a method of manufacturing a semiconductor device in which a silicon oxide film is formed on a semiconductor substrate in a chamber by a method, film formation is performed while gradually increasing the flow rate of the source gas until the temperature of the substrate in the chamber reaches a set temperature. A method of manufacturing a semiconductor device, comprising: 2. The method of manufacturing a semiconductor device according to claim 1, wherein the organic source gas is introduced at the same time as the start of the RF discharge or after the start of the RF discharge. 3. The organic source gas is tetraethyl orthosilicate or octamethylcyclotetra
The method for manufacturing a semiconductor device according to claim 1, which is siloxane.