JP2977170B2 - Glow discharge film forming 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 glow discharge film forming apparatus used for manufacturing an amorphous silicon (a-Si) photosensitive drum and the like, and more particularly, to improvement in uniformity of film forming.

[0002]

2. Description of the Related Art In the manufacture of an amorphous silicon (a-Si) photosensitive drum or the like, a silane compound or the like as a raw material gas is decomposed by glow discharge to form a film on a film forming substrate. A film forming apparatus utilizing decomposition of a source gas by glow discharge is a plasma C
It is also called a VD device and is widely used for forming films of various compounds.

FIG. 7 shows an example of such an apparatus. In the figure, reference numeral 2 denotes a reaction chamber, 4 denotes a reaction chamber container, 6 denotes an Al pipe, which is used as a substrate for a-Si film formation. 8 is a dummy ring, 10 is a support rod, 12 is a motor, and an Al pipe 6
Is to rotate. 14 is the center electrode and 1
Reference numerals 6 and 18 denote supporting rods, reference numerals 20 and 22 denote insulating rings made of ceramic or the like, and reference numerals 24 and 26 denote metal plates for the lid. In this device, a high frequency power of 13.56 MHz or the like is applied from a high frequency power supply 30 and high frequency power is supplied through an impedance matching circuit including variable capacitors CM and CT and a water-cooled high-voltage coil L.

Since the Al pipe 6 is rotated by the motor 12, a uniform film can be formed in the circumferential direction of the Al pipe 6. However, the Al pipe 6 has a high-frequency inductance that cannot be ignored, and it is difficult to form a uniform film in the longitudinal direction of the pipe 6. The high-frequency electric field between the pipe 6 and the electrode 14 is changed to E1 to E3.
Then, the electric fields E1 to E3 differ depending on the position due to the high frequency inductance of the pipe 6. The non-uniformity of the electric fields E1 to E3 is increased by adding positive feedback by the glow discharge, and makes the film forming conditions on the pipe 6 non-uniform. In FIG.
8 shows film forming characteristics of an a-Si photosensitive drum formed by the apparatus shown in FIG. Characteristics such as film forming speed, charging ability, and photosensitivity differ depending on the longitudinal position of the substrate 6, and the characteristics are significantly non-uniform.

The fact that the film forming conditions differ depending on the position not only makes it impossible to obtain a uniform film, but also makes it difficult to form a film on a long substrate.

[0006]

An object of the present invention is to improve the uniformity of film formation. If the uniformity of the film formation is improved, not only the characteristics of the photosensitive drum and the like are improved, but also the film formation on a long substrate becomes easy, and the film can be formed by stacking a plurality of substrates in the axial direction. Become like

[0007]

According to the glow discharge film forming apparatus of the present invention, a film forming base serving as one electrode and the other electrode are provided inside a reaction chamber, and a high frequency power supply and an impedance matching circuit connected to the power supply are provided. And one output of the impedance matching circuit is connected to one end of the substrate for film formation, and the other output of the impedance matching circuit is connected to one end of the other electrode, and the film is formed by glow discharge. In an apparatus configured to form a film on the substrate for use, the other end of one of the one electrode and the other electrode is connected to an output portion to an opposite electrode of an impedance matching circuit via an impedance element. It is characterized by conducting.

[0008]

According to the present invention, the other end of one of the electrodes is connected to the output of the impedance matching circuit to the other electrode through the impedance element. As an impedance element, a variable capacitor, a fixed capacitor, an inductance, or the like is used. In this way, the effect of the high-frequency inductance of the film-forming substrate is compensated, a uniform electric field is generated over the entire surface of the substrate, and the film-forming conditions are made uniform.

[0009]

FIG. 1 is a circuit diagram of an embodiment. The parts denoted by the same reference numerals as those in the conventional example in FIG. 7 represent the same parts. In the figure, C1 and C2 are variable capacitors for adjustment. If the optimum values of the capacitors C1 and C2 are known, fixed capacitors may be used. Further, an inductance element such as a high voltage coil may be used instead of the capacitor. Most preferred among these are variable capacitors that are easy to adjust and do not require cooling. The capacitor connected to the impedance matching circuit side of the center electrode 14 is C
1. The capacitor connected to the other end of the center electrode 14 is designated as C2. The function of the capacitors C1 and C2 is to eliminate the non-uniformity of the discharge electric field due to the high-frequency inductance and the like of the base 6 as the partner electrode. That is, the capacitors C1,
In C2, uniform discharge can be performed except for a change in discharge impedance due to high-frequency inductance or the like of the base Al pipe. Of the capacitors C1 and C2, particularly important is the capacitor C2, and the capacitor C1 may not be provided. In the figure, the coil L side of the impedance matching circuit is connected to the center electrode 14, but the connection of the impedance matching circuit may be changed and the capacitor CM side may be connected to the center electrode 14.

FIGS. 2 and 3 show the structure of the embodiment. FIG.
In the figure, reference numeral 32 denotes an insulating ring made of ceramic or the like, in which a capacitor C2 for adjustment is accommodated. This causes the other end of the center electrode 14 as seen from the impedance matching circuit to conduct to the grounded container 4 by the capacitor C2. The container 4 and the Al pipe 6 are connected to the ground side output of the impedance matching circuit. As shown in FIG. 3, the Al pipe 6 surrounds the center electrode 14 in a ring shape, and a heater 34 and a temperature sensor (not shown) are provided inside the Al pipe 6. Heat to temperature. Also, the inside 36 of the center electrode 14
Is in communication with the atmosphere.

FIG. 4 shows an embodiment in which glow discharge is caused between the Al pipe 6 and the reaction vessel 4. In this case, a capacitor C2 was connected between the metal plate 24 electrically connected to the Al pipe 6 and the ground, and a capacitor C1 was connected between the metal plate 26 and the ground. Since the pipe 6 is thermally expanded by the heater 34 during film formation, a bellows 40 is used to absorb the thermal expansion. Change to bellows 40 and pipe 6
Any mechanism can be used as long as the mechanism prevents the vacuum from being broken by the thermal expansion.

FIG. 5 shows an embodiment using only the capacitor C2 without using the capacitor C1. In this example,
Each Al pipe 6 is connected to both ends of the container 4 and the Al pipe 6
To alleviate the problem of high-frequency inductance of the pipe 6. In order to connect the pipes 6 to both ends of the container 4, bellows 40 are connected to each pipe 6 to absorb thermal expansion. By doing so, the Al pipe 6 is symmetrical in the axial direction with respect to the reaction vessel 4, but the asymmetry of the center electrode 14 remains only by connecting one end of the center electrode 14 to the coil L. Therefore, the center electrode 14
Is connected to a capacitor C2. By the capacitor C2, the discharge conditions are made uniform along the axial direction of the center electrode 14, and the film formation conditions are made uniform.

FIG. 6 shows a comparative example manufactured in the development process of the embodiment of FIG. The difference from the embodiment of FIG. 5 is that the film forming conditions are made uniform only by arranging the Al pipe 6 symmetrically with respect to the axial direction of the reaction vessel 4 without using the adjusting capacitor C2. It is in.

An a-Si photosensitive drum was manufactured using each apparatus shown in FIGS. A raw material gas such as a monosilane gas is introduced into the reaction vessel 4, and a frequency of 13.5 is used as the high frequency power supply 30.
A 6 MHz output impedance of 50Ω is used. In the impedance matching circuit, the matching capacitor CM is about 1000 pF and the tuning capacitor CT is 10
At about 0 pF, the source gas was decomposed by glow discharge between the center electrode 14 and the base pipe 6 (FIGS. 2, 5 to 7), and a film was formed on the base pipe 6. In the embodiment of FIG.
Glow discharge was performed between the pipe 6 and the container 4 to form a film. In each case, the values of the adjustment capacitors C1 and C2 were adjusted using a variable capacitor so that a uniform film could be formed. In the embodiment of FIG. 2, capacitor C1 is about 100 pF and capacitor C2 is about 20 pF. The diameter of the Al pipe 6 as a substrate of the photosensitive drum used is 30 m.
m and a length of 400 mm. 8 to 11 show the results. Table 1 shows the main results. In the embodiment shown in FIG. 4, the film forming conditions were remarkably uniformed in the same manner as in the embodiment shown in FIG. 2, as compared with the embodiment without the capacitors C1 and C2.

[0015]

Table 1 Results Variation Range Film Formation Rate in FIGS. 8 to 11 Charging Ability Sensitivity FIG. 8 Results in Example in FIG. 2 3.3% 3.4% 7.4% FIG. 9 Example in FIG. Result 6.5% 4.5% 7.4% FIG. 10 Result of Comparative Example in FIG. 6 19% 17% 14% FIG. 11 Result of Conventional Example in FIG. 7 50% 37% 34% * The variation width is as follows. The ratio of the difference between the maximum value and the minimum value to the average value is shown.

The results of the examples show that:
In the case of the embodiment of FIG. 2, the discharge impedance between the center electrode 14 and the pipe 6 as viewed from the impedance matching circuit is adjusted by the adjustment capacitors C1 and C2 and made uniform. For this reason, the discharge electric field became uniform, and a uniform a-Si film could be obtained. In the comparative example of FIG. 6, the Al pipe 6 is symmetrical with respect to the upper and lower sides of the reaction vessel 4 to improve the uniformity of the film. FIG.
5 is different from the embodiment of FIG. 5 in that a capacitor C2 is provided. In the embodiment of FIG.
The remaining nonuniformity was eliminated, and a uniform a-Si film was obtained.

[0017]

According to the present invention, a film having uniform characteristics can be formed. As a result, not only the film characteristics are made uniform, but also a uniform film can be formed on a long substrate.
In addition, a large number of substrates can be stacked to form a film, and mass productivity of film formation can be improved.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of an embodiment.

FIG. 2 is a sectional view of an embodiment.

FIG. 3 is a sectional view taken along the line 3-3 of the embodiment.

FIG. 4 is a sectional view of another embodiment.

FIG. 5 is a sectional view of still another embodiment.

FIG. 6 is a sectional view of a conventional example.

FIG. 7 is a sectional view of a conventional example.

FIG. 8 is a characteristic diagram of the embodiment.

FIG. 9 is a characteristic diagram of the embodiment.

FIG. 10 is a characteristic diagram of a conventional example.

FIG. 11 is a characteristic diagram of a conventional example.

[Explanation of symbols]

 2 Reaction chamber 4 Reaction chamber vessel 6 Al pipe 8 Dummy ring 12 Motor 14 Center electrode 20, 22 Insulation ring 24, 26 Metal plate 30 High frequency power supply CM, CT Variable capacitor L Water-cooled high voltage coil C1, C2 Adjustment capacitor 40 Bellows

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁶ , DB name) C23C 16/00-16/52

Claims (1)

(57) [Claims] 1. A reaction chamber having a film forming substrate serving as one electrode and the other electrode, a high-frequency power supply and an impedance matching circuit connected to the power supply, and one output of the impedance matching circuit provided. Is connected to one end of the film-forming substrate, the other output of the impedance matching circuit is connected to one end of the other electrode, and a film is formed on the film-forming substrate by glow discharge. In the apparatus, the other end of any one of the one electrode or the other electrode is, through an impedance element, electrically connected to an output unit to the other electrode of the impedance matching circuit, Glow discharge film forming equipment.