JP3394351B2 - Plasma CVD equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a plasma CVD apparatus, and more particularly to a plasma CVD apparatus capable of high speed cleaning during plasma cleaning after film formation.

[0002]

2. Description of the Related Art Conventionally, plasma CVD apparatuses are roughly classified into a tray system represented by an in-line system and a trayless system represented by a multi-chamber system.

In the case of the tray system, when the amorphous silicon film is formed on a glass substrate, the distance between the cathode electrode and the substrate mounted on the tray, that is, the distance between the electrodes is usually 20.
It is about 30 mm. Then, when film formation is completed, plasma discharge is performed between the electrodes in order to remove films, powders, and the like adhering to members inside the apparatus other than the substrate (for example, the electrode peripheral portion, shower plate), and the inside of the vacuum chamber. Plasma cleaning is performed by introducing an etching gas into.

As described above, it is known that the etching rate when performing plasma cleaning largely depends on the distance between the electrodes, and the etching rate is improved by increasing the distance between the electrodes. For example, the film to be removed by etching is amorphous silicon, the etching gas is NF ₃ , the pressure in the device during cleaning is 40 Pa (0.3 Torr), and the RF power during plasma discharge is 2
FIG. 2 shows the relationship between the etching rate and the distance between the electrodes in the case of W / cm ² .

As is apparent from FIG. 2, the distance between the electrodes is 60
It can be seen that by setting the thickness to 70 mm, the etching rate is remarkably improved and the maximum value is exhibited.

Therefore, as a means for improving the etching rate in order to shorten the plasma cleaning time, the applicant of the present invention has previously disclosed the plasma CV in Japanese Patent Laid-Open No. 6-77143.
A device was proposed in which an inter-electrode distance adjusting device was provided to set the mutual distance between the opposing electrodes during the cleaning operation of the D device to a distance different from that during film formation, and to increase the etching rate by the etching gas.

According to this, the cathode electrode is made movable by an inter-electrode distance adjusting device, and after the film formation, the cathode electrode is moved to make the mutual distance between the opposed electrodes different from that at the film formation, and then plasma cleaning is performed. Is what
In case of a-Si: H film and SiNx: H film, the distance between electrodes is 4
By increasing it to 0 to 100 mm, the etching rate at the time of plasma cleaning is improved. By improving the etching rate, the plasma cleaning time can be shortened.

[0008]

In recent years, with the demand for a larger effective film-forming area, the film-forming apparatus also becomes larger, and at the same time, the cathode electrode also becomes larger. It became complicated and practically inconvenient.

In particular, since the flatness of the surface of the cathode electrode is very important, the cathode electrode is once moved to another position to change the distance between the electrodes, and plasma cleaning is performed. When returned to a predetermined position, it becomes difficult to reproduce the flatness of the cathode electrode surface.

For example, the effective film-forming area is 1000 mm (1 m) × 1000
In the case of mm (1 m), the size of the cathode electrode is 1200 mm (1.2 m) ×
About 1200mm (1.2m) is required. On the other hand, the 10 mm thick stainless steel cathode electrode is 1200 mm (1.2 m) x 1200 in size.
When it becomes mm (1.2 m), even if one side is fixed and the other side is pressed with a finger, a deflection of about 5 mm occurs.

Further, if the uniformity of the film thickness distribution is taken into consideration during the film formation, the accuracy of the flatness of the cathode electrode surface must be ± 1 mm or less. Therefore, the size of the cathode electrode is 1000
In the case of mm (1 m) × 1000 m (1 m) or more, the cathode electrode is not a rigid body and must be treated as something that deforms to some extent. After moving the deforming cathode electrode, it is necessary to maintain the flatness of the cathode electrode surface within ± 1 mm or less / 1200 mm (1.2 m) × 1200 mm (1.2 m) after returning to its original position. The problem is that the current technology is quite large and requires a complicated mechanism.

Therefore, there is a demand for development of means capable of high-speed cleaning while the cathode electrode is fixed during plasma cleaning.

An object of the present invention is to solve the conventional problems and to provide a plasma CVD apparatus capable of high-speed cleaning while the cathode electrode is fixed during plasma cleaning in the apparatus after film formation. .

[0014]

Means for Solving the Problems Plasma CVD of the present invention
The apparatus heats a substrate, a cathode electrode for applying a high frequency to a vacuum chamber having an exhaust system, a tray on which a substrate is mounted and conveyed, a gas introduction system of a film forming gas for forming a film on the substrate, and a substrate. In a tray transfer type plasma CVD apparatus having a heater for heating, when an etching gas is introduced instead of a film forming gas to perform plasma cleaning, the tray is moved to a position different from that at the time of film forming and the cathode electrode It is characterized in that plasma discharge is performed between the heaters.

The heater may be made of a corrosion resistant material. Since the heater for heating is exposed to etching gas during plasma cleaning, it is optimal to use a corrosion-resistant material. As a corrosion-resistant material, it is corrosion-resistant and excels in heat generation, and also has heat resistance. carbon,
Ceramics, metal materials (eg Hastelloy, Inconel)
Etc.

The etching gas is NF ₃ , CF ₄ , CH
It may be either a fluorine-based gas such as F ₃ or SF ₆ .

[0017]

[Function] After film formation, by moving the tray on which the substrate is mounted to a position different from that during film formation, the electrode for plasma discharge becomes the cathode electrode and heater for heating, and the distance between both electrodes is the optimum distance for cleaning. Can be set to
Thereby, the etching rate can be increased and high-speed plasma cleaning can be performed.

Further, since the cathode electrode can be cleaned in a fixed state, it is not necessary to consider the reproducibility of the flatness of the cathode electrode surface when the film is formed again after the plasma cleaning, and the long-term stability during the film formation is improved. To be kept.

[0019]

FIG. 1 shows an embodiment of the plasma CVD apparatus of the present invention. The illustrated example is a tray type plasma C for vertical transfer.
A VD device, in which 1 is a gas introduction system 2 connected to a reactive gas source such as a gas cylinder or an etching gas source
And a vacuum chamber having a vacuum exhaust system 3 connected to a vacuum pump or the like.

In the vacuum chamber 1, a substrate 5 mounted on a tray 4 has a transfer system 8 including a tray rail 6 and transfer wheels 7.
To be transported in.

Further, a cathode electrode 9 was arranged facing the substrate 5, and an external high frequency power source 10 was connected to the cathode electrode 9.

The cathode electrode 9 is composed of a hollow electrode having a shower plate 11 on the front surface thereof, and the gas introduction system 2 is connected to the hollow portion of the cathode electrode 9 to provide a large number of gas ejection ports provided on the shower plate 11. From 12, the reactive gas is ejected uniformly during the film formation in the vacuum chamber 1, and the etching gas is ejected during the plasma cleaning. Then, a heater 13 for heating the substrate 5 was provided on the back side of the tray 4.

During the film formation, the tray 4 is maintained at the ground potential by the ground 14 connected to the tray 4, and the heating heater 13 is grounded by the ground 15 connected to the heating heater 13 during cleaning. The potential was maintained.

In the figure, reference numeral 16 indicates a deposition preventive plate.

To quantify the cleaning speed, the method of measuring the etching rate on the substrate is usually simple, but the tray is moved to a position different from that during film formation as in the present invention. When performing cleaning on the above, during plasma discharge during plasma cleaning, the discharge time until the film formed on the cathode electrode surface disappears is measured visually, and the film thickness formed before cleaning is measured by the discharge time. It was decided to obtain the cleaning rate by dividing.

Example 1 In this example, the cathode electrode 9 has a thickness of 30 mm and a length of 1200 mm.
(1.2m) x 1200mm (1.2m) horizontal stainless steel electrode, substrate 5 thickness 1.1mm x length 450mm (0.45m) x width 450mm (0.45m)
m) using 4 glass substrates and heating heater 1
As No. 3, a carbon case heater having a thickness of 30 mm × length 1200 mm (1.2 m) × width 1200 mm (1.2 m) and a sheath heater built therein was used.

Further, the distance between the substrate 5 and the cathode electrode 9 is usually 20 mm when the a-Si: H film is formed,
The distance between the back surface of the tray 4 and the front surface of the heater 13 for heating is 40 mm.

Therefore, in this embodiment, the tray 4 (thickness 7 m
m) and the substrate 5 (thickness 1.1 mm) have a total thickness of about 8 mm,
The distance between the surface of the cathode electrode 9 and the surface of the heater 13 without the tray 4 was set to 68 mm.

First, the film-forming gas (SiH ₄ ) introduced from the gas introduction system 2 into the vacuum chamber 1 is plasma decomposed to produce the substrate 5
An a-Si: H film having a film thickness of 5 μm (50000Å) was formed on the upper surface.

Next, after the film formation, the tray 4 is moved to the tray rail 6
After moving from the film formation position to the outside of the vacuum chamber 1 by the transfer system 8 including the transfer wheels 7, the inside of the vacuum chamber 1 is set to a pressure of 40 Pa (0.3 Torr) by the vacuum exhaust system 3, and then the inside of the vacuum chamber 1 is set. From the gas introduction system 2 to the gas ejection port 12 of the shower plate 11
Tetrafluoromethane (C
While introducing 1000 sccm of F ₄ ) gas and 100 sccm of oxygen (O ₂ ) gas, RF power of 2 kW was applied between the cathode electrode 9 and the heater 13 for heating from the high frequency power source 10 to perform plasma discharge to perform plasma cleaning.

When the etching rate during plasma cleaning was examined, it was 0.18 μm (1800 Å) / min.

Comparative Example 1 After film formation, plasma cleaning was performed under the same conditions as in Example 1 except that the plasma discharge was performed between the cathode electrode 9 and the tray 4 without moving the tray 4. . Therefore, the distance between the electrodes (cathode electrode 9 and substrate 5) is 20 mm.

When the etching rate during plasma cleaning was examined, it was 0.02 μm (200 Å) / min.

Example 2 Nitrogen trifluoride (NF ₃ ) gas 1000s as etching gas
Plasma cleaning was performed in the same manner as in Example 1 except that ccm and 500 sccm of trifluoromethane (CHF ₃ ) gas were used.

When the etching rate during plasma cleaning was examined, it was 0.38 μm (3800Å) / min.

Comparative Example 2 After film formation, plasma discharge was performed between the cathode electrode 9 and the tray 4 without moving the tray 4, and nitrogen trifluoride (NF ₃ ) gas of 1000 sccm was used as an etching gas. Plasma cleaning was performed in the same manner as in Example 1 except that 500 sccm of fluorinated methane (CHF ₃ ) gas was used.

When the etching rate during plasma cleaning was examined, it was 0.07 μm (700 Å) / min.

Example 3 A film forming gas (Si
H ₄ and NH ₃ and N ₂ ) are plasma decomposed, and a film of 5 μm (50000Å) SiNx: H film is formed on the substrate 5.
Plasma cleaning was performed in the same manner as in Example 1.

When the etching rate during plasma cleaning was examined, it was 0.14 μm (1400Å) / min.

Comparative Example 3 A film forming gas (Si
H ₄ and NH ₃ and N ₂ ) are decomposed by plasma to form a film on the substrate 5 with a film thickness of 5 μm (50000Å) as SiNx: H film, and after the film formation, the plasma is generated without moving the tray 4. Plasma cleaning was performed in the same manner as in Example 1 except that discharge was performed between the cathode electrode 9 and the tray 4.

When the etching rate during plasma cleaning was examined, it was 0.017 μm (170 Å) / min.

Example 4 The film forming gas (Si) introduced from the gas introduction system 2 into the vacuum chamber 1
H ₄ and NH ₃ and N ₂ ) are plasma decomposed to form a film on the substrate 5 as a SiNx: H film having a film thickness of 5 μm (50000Å), and nitrogen trifluoride (NF ₃ ) gas is 1000 sccm as an etching gas. Plasma cleaning was performed in the same manner as in Example 1 except that 500 sccm of trifluoromethane (CHF ₃ ) gas was used.

When the etching rate during plasma cleaning was examined, it was 0.27 μm (2700Å) / min.

Comparative Example 4 A film forming gas (Si
H ₄ and NH ₃ and N ₂ ) are decomposed by plasma to form a film on the substrate 5 as a SiNx: H film having a film thickness of 5 μm (50000Å).
Plasma discharge is performed between the cathode electrode 9 and the tray 4 without moving the tray 4, and nitrogen trifluoride (NF ₃ ) gas 1000 sccm and methane trifluoride (CHF ₃ ) gas 500 sccm are used as etching gas. Plasma cleaning was performed in the same manner as in Example 1 except that the above was used.

When the etching rate during plasma cleaning was examined, it was 0.053 μm (530Å) / min.

Example 5 Sulfur hexafluoride (SF ₆ ) gas 100 was used as an etching gas.
Plasma cleaning was performed in the same manner as in Example 1 except that 0 sccm and 200 sccm of oxygen (O ₂ ) gas were used.

When the etching rate during plasma cleaning was examined, it was 0.28 μm (2800Å) / min.

Comparative Example 5 After film formation, plasma discharge was performed between the cathode electrode 9 and the tray 4 without moving the tray 4, and sulfur hexafluoride (SF ₆ ) gas of 1000 sccm and oxygen were used as etching gas. Plasma cleaning was performed in the same manner as in Example 1 except that 200 sccm of (O ₂ ) gas was used.

When the etching rate during plasma cleaning was examined, it was 0.05 μm (500Å) / min.

As is clear from the results of Examples 1, 2, 3, 4, and 5 and Comparative Examples 1, 2, 3, 4, and 5, each example of the present invention was applied to the tray during the plasma cleaning. It was confirmed that the etching rate was improved by performing the plasma discharge between the cathode electrode and the heating heater by moving it to a position different from that, and high-speed cleaning could be performed.

Although the vertical tray type plasma CVD apparatus is used in the above embodiment, the horizontal tray type plasma CV is used.
Even if the D device is used, the etching rate is similarly improved,
High-speed cleaning can be performed.

[0052]

According to the plasma CVD apparatus of the present invention, the tray is moved to a position different from that during film formation during plasma cleaning after film formation. Therefore, the distance between electrodes is set to an optimum distance for cleaning. Therefore, there is an effect of providing a plasma CVD apparatus capable of increasing the etching rate and performing high-speed plasma cleaning.

Further, since the cathode electrode can be cleaned in a fixed state, it is not necessary to consider the reproducibility of the flatness of the cathode electrode surface when the film is formed again after the plasma cleaning. Is maintained and productivity is improved.

When the heater is made of a corrosion resistant material such as carbon or ceramics, even if a corrosive gas is used as an etching gas during plasma cleaning, stable plasma cleaning can be performed for a long period of time. is there.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of an example of a plasma CVD apparatus of the present invention,

FIG. 2 is a characteristic diagram showing a relationship between an electrode distance and an etching rate.

[Explanation of symbols]

1 vacuum tank, 2 gas introduction system, 3 vacuum exhaust system, 4 trays, 5 substrates, 6 tray rails, 8 transfer system, 9 cathode electrode, 10 high frequency power supply, 11
Shower plate, 13 heating heater,
14 Tray ground, 15 Heating heater ground.

─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masanori Hashimoto 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute for Supermaterials (72) Atsushi Togawa 523 Yokota Yokota, San-bu, Chiba Prefecture Chiba Institute of Supermaterials (72) Inventor Noriaki Tani 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Japan Vacuum Technology Co., Ltd. Chiba Institute of Supermaterials (72) Inventor Hisami Nakamura 523 Yokota, Yamatake-cho, Sanmu-gun, Chiba Chiba Institute of Super Materials (56) References JP-A-5-155684 (JP, A) JP-A-6-41757 (JP, A) JP-A-5-251365 (JP, A) Actual Kaihei 5 -38868 (JP, U) (58) Fields surveyed (Int.Cl. ⁷ , DB name) H01L 21/205 C23C 16/50 C23F 4/00

Claims (3)

(57) [Claims] 1. A cathode electrode for applying a high frequency to a vacuum chamber having an exhaust system, a tray on which a substrate is mounted and conveyed, a gas introduction system of a film forming gas for forming a film on the substrate, and a substrate. In a tray transfer type plasma CVD apparatus having a heating heater for heating, when an etching gas is introduced instead of a film forming gas to perform plasma cleaning, the tray is moved to a position different from that at the time of film forming and the cathode is moved. A plasma CVD apparatus characterized in that plasma discharge is performed between an electrode and a heater. 2. The plasma CVD apparatus according to claim 1, wherein the heater is made of a corrosion resistant material. 3. The etching gas is NF ₃ , CF ₄ , C
The plasma CVD apparatus according to claim 1, wherein the plasma CVD apparatus is at least one kind of fluorine-based gas such as HF ₃ and SF ₆ .