JP3071657B2 - Thin film forming apparatus and thin film forming method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and a method for forming a thin film by a plasma CVD method.

[0002]

2. Description of the Related Art Conventionally, in the process of manufacturing electronic devices such as liquid crystal display elements, solar cells, and integrated circuits, thin films of semiconductors, insulators, and metals have been formed. As a method of forming such a thin film, a chemical vapor deposition method (CVD method) or a physical vapor deposition method (PVD method) is roughly adopted.

In the CVD method, a raw material gas is decomposed by energy such as heat or plasma and chemically reacted on a growth surface of a substrate to form a thin film. A high melting point material is formed at a low temperature. And a high-purity thin film can be formed. Among the CVD methods, the plasma CVD method in which a source gas is decomposed by using plasma can grow a thin film at a low temperature, form a thin film on a non-heat-resistant substrate,
In addition, it becomes possible to synthesize an amorphous thin film and the like.

The plasma used in such a plasma CVD method includes a direct current (DC) plasma, a high frequency (R)
F) Plasma, microwave plasma and the like are known. FIG. 6 is a schematic configuration diagram showing an example of a conventional RF plasma CVD apparatus. Referring to FIG. 6, counter electrode 2 is provided in reaction vessel 10 so as to face substrate 1. The substrate 1 is placed on the ground electrode 4. A high frequency power supply 3 is connected to the counter electrode 2. The ground electrode 4 is grounded.

The high frequency power from the high frequency power supply 3
Is generated between the counter electrode 2 and the ground electrode 4, and the raw material gas introduced into the reaction vessel 10 is decomposed by the plasma, and a thin film is formed on the substrate 1.

[0006] In the device shown in FIG. 6, a connection portion located at the center of the counter electrode 2 is connected to the high frequency power supply 3. FIG.
FIG. 2 is a schematic configuration diagram showing another example of a conventional RF plasma CVD apparatus. In the apparatus shown in FIG. 7, the counter electrode 2 is placed on the connection plate 5 and the protruding frame portions 5a and 5b around the connection plate 5
Is in contact with and is supported. Therefore, the opposing electrodes 2 are in contact with each other at the four sides on the outer periphery of the connection plate 5. The high frequency power supply 3 is electrically connected to the connection plate 5 at a connection portion located at the center of the connection plate 5.

[0007]

However, when a thin film is formed by using these conventional CVD apparatuses, the thickness of the formed thin film may not be uniform.

The inventors of the present invention have conducted various studies on the causes of the non-uniform film thickness distribution. As a result, the thin film tends to be formed thicker at a portion corresponding to a connection portion to which power is supplied in the counter electrode. I found something. That is, in the device in which the connecting portion is provided at the center of the counter electrode 2 as shown in FIG. 6, the film thickness tends to be thick at the center of the thin film.

Further, in an apparatus as shown in FIG. 7 in which the peripheral portion of the counter electrode 2 serves as a connection portion, the thickness of the peripheral portion of the thin film tends to increase. The present invention is based on the above findings of the present inventors, and has an object to provide a thin film forming apparatus and a thin film forming method capable of forming a thin film having a uniform film thickness distribution by a plasma CVD method. .

[0010]

The thin film forming apparatus of the present invention is an apparatus for forming a thin film on a substrate by a plasma CVD method, and includes a counter electrode provided at a position facing the substrate, and a plasma formed on the counter electrode. Arbitrarily change the power supply that supplies power for generation and the position that supplies power from the power supply
And a plurality of switching means provided corresponding to the plurality of connection portions for switching power supply from a power supply to the plurality of connection portions. .

A thin film forming method according to the present invention is a method for forming a thin film on a substrate using the above-described thin film forming apparatus according to the present invention. And the thickness distribution of the thin film is controlled.

The present invention is generally applied to a plasma CVD method, and is particularly useful in an RF plasma CVD method generally used in the production of hydrogenated amorphous silicon and the like. However, R
The present invention can be applied to a plasma CVD method other than the F plasma CVD method, and can be applied to, for example, a DC plasma CVD method.

[0013]

According to the thin film forming apparatus of the present invention, a plurality of connecting portions are provided on the counter electrode , and a plurality of switching means for switching the plurality of connecting portions are provided. . Therefore, by switching with this switching means, the position of the connection part for supplying the power from the power supply can be arbitrarily changed. According to the findings of the present inventors, the thickness of the thin film tends to increase in a region corresponding to the connection portion. Can be.

In the method of forming a thin film according to the present invention, such a change of the connection portion is performed during the formation of the thin film, thereby controlling the thickness distribution of the thin film. Therefore, during the formation of the thin film, the thickness distribution of the thin film being formed is measured, and by reflecting the measurement result, the connection portion is changed so that the film thickness distribution becomes uniform or a desired distribution. The thickness distribution can be made uniform.

Further, it is also possible to control the film thickness distribution of the thin film, for example, in lot units by using the thin film forming apparatus of the present invention. For example, a thin film is formed on a trial basis under predetermined conditions, the thickness of the thin film produced on a trial basis is measured, and from the obtained thickness distribution data, a more uniform or desired thickness distribution is obtained. In this manner, by determining the connection portion to be connected to the power supply and forming a subsequent thin film in the connected state, a thin film having a uniform or desired film thickness distribution can be formed.

[0016]

FIG. 1 is a schematic diagram showing an RF plasma CVD apparatus according to an embodiment of the present invention. Referring to FIG.
A counter electrode 2 to which high-frequency power is supplied is provided in the reaction vessel 10 so as to face the substrate 1. The substrate 1 is placed on the ground electrode 4. Counter electrode 2 and ground electrode 4
Are provided in parallel to constitute a plasma CVD apparatus having parallel plate type electrodes. A plurality of connection portions 11 are provided on a surface of the opposite electrode 2 opposite to the substrate 1. In the present embodiment, five in the vertical direction and five in the horizontal direction, a total of 2
Five connecting portions 11 are arranged in a matrix. A switch 12 for switching power supply to the connection unit 11 is connected to each connection unit 11. The high frequency power supply 3 is connected to these switches 12.

In the apparatus shown in FIG. 1, power can be supplied from the high frequency power supply 3 at a desired connection portion 11 by switching of a switch 12. Therefore, by supplying power at the connection portion 11 at a position corresponding to the portion where the film thickness is to be increased, the thickness of the thin film formed in that region can be increased. The setting of the ON state and the OFF state of the switch 12 may be performed manually, or may be automatically controlled by a controller or the like.

Using an apparatus as shown in FIG. 1, a thin film of hydrogenated amorphous silicon was formed. The formation conditions were as follows: SiH ₄ gas flow rate: 10 sccm, reaction pressure: 0.
5 torr, RF power: 20 W, forming temperature: 200
C., formation time: 60 minutes. The connection state at the connection unit 11 shown in FIG. 1 was as shown in FIG. FIG.
A region where the counter electrode is divided into five sections in the vertical direction and five sections in the horizontal direction, that is, a total of 25 sections is shown. Further, in FIG. 2, a mark “○” indicates a state in which the connection portion is connected so as to introduce power from a power supply. Therefore, the connection portion corresponding to the region indicated by the mark is turned on by the switch, and the connection portion corresponding to the region not marked by the mark is turned off by the switch.

After forming a thin film in the connection state shown in FIG.
The substrate was taken out, and the thickness distribution of the formed thin film was measured. FIG. 3 is a diagram showing the measurement results of the film thickness distribution. FIG.
Numerical values shown in indicate the average film thickness in each region, and the unit is Δ. As shown in FIG. 3, the average film thickness is 3000 ° or more in the peripheral region where the connection portion is brought into the connection state. On the other hand, in the central region where the connection portion is not connected, 2000Å to 24２４
The average film thickness is 00 °.

In order to obtain a uniform film thickness distribution, the connection state of the connection portion 11 shown in FIG. 1 was changed to a state shown in FIG. That is, the switch is turned off in the peripheral region, and the switch is turned on in the central region, so that a connection state in which power is supplied to each region in the central portion is established.

The connection state was set as shown in FIG. 4, and a thin film of hydrogenated amorphous silicon was formed under the same forming conditions as described above. FIG. 5 is a diagram showing a film thickness distribution of the formed thin film. The unit is Å as in FIG. As shown in FIG. 5, a thin film having a substantially uniform film thickness distribution as a whole is formed by setting the connection state in which power is supplied at the center as shown in FIG.

As described above, according to the present invention, it is possible to arbitrarily set a connection portion to be connected to a power supply, thereby forming a thin film having a desired film thickness distribution. In the above embodiment, the connection state is changed every time the thin film is formed. However, the connection state of the connection portion may be changed during the formation of the thin film. For example, after a thin film is formed in a connection state as shown in FIG. 2 for a predetermined time, the thin film may be formed by changing the connection state as shown in FIG. When the thin film was formed by changing the connection state during the formation of the thin film as shown in FIG.
The non-uniform film thickness distribution shown in FIG. 1 was improved, and a film having a substantially uniform film thickness distribution was obtained.

In the above embodiment, the formation of a thin film of hydrogenated amorphous silicon has been described as an example, but the present invention is also applicable to the formation of other semiconductor films, insulating films, metal films, and the like.

[0024]

According to the present invention, a plurality of connecting portions are provided on the counter electrode , and a switching means is provided for each of the plurality of connecting portions. Therefore, the connection part connected to the power supply can be changed by switching of the switching means. Therefore, it is possible to control the film thickness distribution of the thin film by connecting at the connection portion corresponding to the region where the film thickness is to be increased.

Therefore, according to the present invention, it is possible to form a thin film having a uniform film thickness distribution.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram showing a thin film forming apparatus of an embodiment according to the present invention.

FIG. 2 is a diagram showing a connection state of a connection portion of a counter electrode.

FIG. 3 is a view showing a film thickness distribution when a thin film is formed in the connection state shown in FIG. 2;

FIG. 4 is a diagram showing a connection state of a connection portion of a counter electrode.

FIG. 5 is a view showing a film thickness distribution when a thin film is formed in the connection state shown in FIG. 4;

FIG. 6 is a schematic configuration diagram showing an example of a conventional RF plasma CVD apparatus.

FIG. 7 is a schematic configuration diagram showing another example of a conventional RF plasma CVD apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Substrate 2 ... Counter electrode 3 ... High frequency power supply 4 ... Grounding electrode 5 ... Connection plate 5a, 5b ... Frame part of connection plate 10 ... Reaction vessel 11 ... Connection part 12 ... Switch

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-62-130277 (JP, A) JP-A-6-302588 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C23C 16/505 H01L 21/205 H01L 21/3065 H05H 1/46

Claims (2)

(57) [Claims] 1. An apparatus for forming a thin film on a substrate by a plasma CVD method, comprising: a counter electrode provided at a position facing the substrate; and a power supply for supplying power to the counter electrode for generating plasma. And arbitrarily changing the position for supplying power from the power source .
And a plurality of switching means provided corresponding to the plurality of connection parts for switching the power supply from the power supply to the plurality of connection parts. Thin film forming equipment. 2. A method for forming a thin film on a substrate using the thin film forming apparatus according to claim 1, wherein the connection portion connected to the power supply is changed by switching of the switching means during the formation of the thin film. And controlling the thickness distribution of the thin film.