JPH02111023A - Formation of film and plasma cvd apparatus - Google Patents

Abstract

PURPOSE:To enhance a film-thickness distribution and a film quality of a film to be formed by a method wherein an electric current whose value is changed intermittently is supplied to a sub-coil. CONSTITUTION:An electric current whose value is changed intermittently is supplied to a sub-coil 9 installed near a wafer stand 5 in a deposition chamber 8. That is to say, an electric current which generates a magnetic flux used to make a film-thickness distribution best by making a face distribution of a plasma density uniform and an electric current which generates a magnetic flux used to make a film quality and its distribution best by setting a magnetic- potential distribution to a desired value uniformly are alternately supplied to the sub-coil 9; a film is then formed. Thereby, these act jointly; the film- thickness distribution is enhanced; the film quality and its distribution can be enhanced at the same time.

Description

[Detailed Description of the Invention] C4El Required] Regarding a film forming method using a plasma CVD device and an improvement of the plasma CVD device, a method for forming a semiconductor layer, etc.
The purpose is to provide 12 methods for forming semiconductor layers, etc. that improve not only the film thickness distribution but also the film quality and its distribution, and the plasma CVD equipment used therein. and a gas supply port, and a plasma generation chamber around which a coil is wound, and a wafer stage that communicates with the plasma generation chamber and is provided downstream of the plasma flowing from the plasma generation chamber. A plasma C comprising a deposition chamber having a supply port and a gas exhaust port, and a subcoil provided near the wafer table in the deposition chamber.
In a method for forming a film such as a semiconductor layer using a VD device, the subcoil is configured to be supplied with a current whose value changes intermittently.

[Industrial application field]

The present invention relates to a method of forming a film such as a semiconductor layer using a plasma CVD apparatus, and to an improvement of the plasma CVD apparatus. In particular, the present invention relates to improvements that not only improve the film thickness distribution of formed films such as semiconductor layers, but also improve the film quality and its distribution.

[Conventional technology]

Referring to FIG. 3, there is shown a configuration diagram of an ECR type plasma CVD apparatus shown as an example of a plasma CVD apparatus. The ECR of the ECR type plasma CVD equipment shown as an example is El
ectron Cyclotron Re5onanc
It is an abbreviation of e, which accelerates electrons using the resonance effect between the microwave introduced from the microwave introduction port 1 and the magnetic field generated by the ECR coil 3, and then uses the kinetic energy of the electrons to generate the gas from the gas supply port 2. The supplied gas such as nitrogen is turned into plasma in the plasma generation chamber 4. The wafer 1] is placed on the wafer stand 5 of the deposition chamber 8 which communicates with the plasma generation chamber 4, and a reactive gas such as silane (SiH4) is supplied from the reactive gas supply port 6, and this reactive gas is used for the plasma generation described above. Activated by plasma flowing in from chamber 4,
] A silicon nitride film or the like is deposited thereon.

The diagram shown in FIG. 4 shows the film thickness distribution along the diameter of the wafer. When a silicon nitride film or the like is formed using the plasma CVD apparatus described above, the film thickness varies between the periphery and center of the wafer. 8
% difference occurs. Furthermore, when the above silicon nitride film is etched using hydrofluoric acid diluted 10 times with water, the average etching rate is 250 people/mi.
However, there is a variation of about ±8% within the wafer.

Therefore, the following method was developed to improve the film thickness distribution.

Refer to FIG. 5. A subcoil 9 is provided near the wafer table 5, for example, on the bottom surface of the wafer table 5 as shown in the figure, and a constant DC current is supplied to this subcoil 9 to generate a magnetic field along the plasma flow. Wafer 1 by uniformizing the in-plane distribution of plasma density]
This improves the film thickness distribution of the silicon nitride film deposited thereon. Note that the configuration other than the above is the same as the configuration shown in FIG. 3.

The diagram shown in FIG. 6 shows the film thickness distribution within the wafer of the silicon nitride film formed by the above method. The difference in film thickness between the periphery and center of the wafer was about 2%, and the film thickness distribution was improved.

[Problem to be solved by the invention]

By the way, when direct current was passed through the subcoil 9, the film thickness distribution was improved as shown in FIG. As high as 400 people/sin,
It was confirmed that the film quality had deteriorated considerably, and it was also confirmed that the variation in film quality within the wafer was as large as about ±5 to 8%.

The purpose of the present invention is to eliminate this drawback, and to provide a method for forming a film that not only improves the film thickness distribution of a film formed such as a semiconductor layer but also improves the film quality and its distribution, and a plasma CVD method used therein. The purpose is to provide equipment.

[Means to solve the problem]

The first purpose of the above two purposes is to have a microwave introduction port (1) and a gas supply port (2), and a coil (3).
a plasma generation chamber (4) in which the plasma is wound, and a wafer stand (5) that communicates with this plasma generation chamber (4) and is provided downstream of the plasma flowing from this plasma generation chamber (4).
), a deposition chamber (8) having a reactive gas supply port (6) and a gas exhaust port (7), and a subcoil (9) provided near the wafer table (5) of this deposition chamber (8). ), the method is achieved by supplying a current whose value changes intermittently to the subcoil (9).

The second purpose of the above two purposes is to have a microwave introduction port (1) and a gas supply port (2), and a coil (
3) is connected to the plasma generation chamber (4) in which the plasma generation chamber (4) is wound.
) has a wafer stand (5) provided downstream of the plasma flowing in from the reactor gas supply port (6) and the gas exhaust port (7).
), and a subcoil (9) provided near the wafer table (5) of the deposition chamber (8).
This is achieved by a plasma CVD apparatus having a variable current supply means (10) for supplying a variable current to the subcoil (9).

[Effect]

When a direct current is passed through the subcoil 9 to generate magnetic flux along the plasma flow, the in-plane distribution of plasma density becomes uniform and the thickness distribution of the formed film improves. Moreover, the in-plane distribution of magnetic potential becomes non-uniform, the distribution of electron temperature becomes non-uniform, the quality of the formed film deteriorates, and the distribution of film quality becomes non-uniform. In addition, what is desired for the film quality is, physically, low internal stress and sufficiently high hardness (chemically, low etching rate with hydrofluoric acid, etc., and low hydrogen concentration in the film, etc.).
That is what makes it difficult to leave.

Method for forming a film such as a semiconductor layer according to the present invention and plasma C
In the VD apparatus, a variable current generating means 10 that generates a variable current by superimposing a pulse current, a sine wave current, etc. on a direct current is added to a conventional plasma CVD apparatus,
The subcoil 9 is supplied with a current that generates a magnetic flux that uniformizes the in-plane distribution of plasma density and provides the best film thickness distribution, and a current that uniformizes the magnetic potential distribution to a desired value! By alternately supplying ff and a current that generates a magnetic flux with the best distribution, it is possible to simultaneously improve the film quality and its distribution in addition to improving the film thickness distribution.

(Example) Hereinafter, with reference to the drawings, a method of forming a silicon nitride film according to an example of the present invention and a plasma CVD apparatus directly used in this film forming method will be described.

The period referred to in FIG. 1a shows the plasma CV used in the film forming method according to the present invention.
It is a block diagram of D apparatus. 4 is a plasma generation chamber, which has a microwave introduction port 1 and a gas supply port 2, and an E
A CR coil 3 is wound around it. 8 is plasma generation chamber 4
A wafer table 5 is provided in the vicinity of the wafer table 5, and is provided with a reaction gas supply port 6, a gas exhaust lower, and a wafer table 5 facing the plasma flow flowing in from the plasma generation chamber 4.
For example, a subcoil 9 is provided on the lower surface of the wafer table 5. Reference numeral 10 denotes variable current supply means for supplying variable current to the subcoil 9.

For example, nitrogen gas is supplied from the gas supply port 2, and one person applies a 2.45 GHz microwave from the microwave introduction port 1.
When the CR coil 3 is turned off, nitrogen plasma is generated in the plasma generation chamber 4 due to the electron cyclotron resonance effect, and the plasma flows into the deposition chamber 8. When, for example, silane (SiH) gas is supplied to the deposition chamber 8 from the reaction gas supply port 6, the silane gas is activated by the nitrogen plasma flowing into the deposition chamber 8, and nitriding is performed on the wafer 1 placed on the wafer table 5. Deposit a silicon film.

1b and 2, from the variable current supply means 10 - for example, direct /
When a current having the waveform shown in Fig. 1b generated by superimposing a pulse current on the it current is supplied to the subcoil 9, during a time period of 500 m5 in which a large current of, for example, 12A flows, the magnetic flux generated by the subcoil 9 will cause the plasma density to increase. The in-plane distribution is made uniform, the thickness distribution of the deposited silicon nitride film is improved, and a small current, for example 100
*During the time period s, the magnetic flux generated by the subcoil 9 uniformizes the magnetic potential distribution to a desired value, the electron temperature distribution becomes uniform, and the quality and distribution of the deposited silicon nitride film improves. As a result of these actions, the difference in film thickness between the peripheral and central areas is within 3%, as shown in Figure 2, and the etching rate with hydrofluoric acid is 250 people/re i. n, the film quality was improved, and the in-plane variation in film quality was also improved to about ±2 to 3%.

〔Effect of the invention〕

As explained above, the plasma CVD apparatus according to the present invention is provided with variable current supply means for supplying a variable current to the subcoil provided near the wafer stand, and the film forming method according to the present invention includes: A current is applied to the above-mentioned added sub-coils to generate a magnetic flux that uniformizes the in-plane distribution of plasma density and achieves the best film thickness distribution, and a current that uniformizes the magnetic potential distribution to a desired value to improve film quality and its distribution. Since the current that generates the best magnetic flux is alternately supplied to form the film, these two effects work together to improve not only the film thickness distribution but also the film quality and its distribution. It is possible to improve at the same time.

[Brief explanation of the drawing]

FIG. 1a is a block diagram of a plasma CVD apparatus according to the present invention. FIG. tb shows a variable current waveform used in a film forming method according to an embodiment of the present invention. FIG. 2 is a film thickness distribution diagram of a film such as a semiconductor layer formed using a film forming method according to an embodiment of the present invention. 3 and 5 are configuration diagrams of a plasma CVD apparatus according to the prior art. FIGS. 4 and 6 are film thickness distribution diagrams of films such as semiconductor layers formed using a plasma CVD apparatus according to the prior art. 1 ・ ・ 2 ・ ・ 3 ・ ・ 4 ・ ・ 5 ・ ・ 6 ・ 7 ・ ・ 8 ・ ・ 9 ・ ・ 10 ・ 1] ・ ・ Microwave introduction port, gas supply port, ECR coil, plasma generation chamber, wafer Table, reaction gas supply port, gas exhaust port, deposition chamber, subcoil, variable current supply means, wafer. Plasma CVO A1 (present invention) Figure 1a

Claims (1)

[Scope of Claims] [1] A plasma generation chamber (
4), which communicates with the plasma generation chamber (4) and connects the plasma generation chamber (4) with the plasma generation chamber (4).
It has a wafer stand (5) provided downstream of the plasma flowing in from the reactor gas supply port (6) and the gas exhaust port (4).
7); and a sub-coil (9) provided in the vicinity of the wafer stage (5) of the deposition chamber (8). A film forming method characterized in that a current whose value changes intermittently is supplied to the subcoil (9). [2] A plasma generation chamber (
4), which communicates with the plasma generation chamber (4) and connects the plasma generation chamber (4) with the plasma generation chamber (4).
It has a wafer stand (5) provided downstream of the plasma flowing in from the reactor gas supply port (6) and the gas exhaust port (4).
7); a subcoil (9) provided near the wafer stand (5) of the deposition chamber (8); and variable current supply means for supplying a variable current to the subcoil (9). (10) A plasma CVD apparatus comprising: