JP3472227B2 - Carbon thin film forming method - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to the hard carbon thin film, or diamond-like carbon film (hereinafter these is referred to as "carbon film") relates to a thin film forming method that form a. In the present specification, a carbon thin film having a good film quality means high hardness, good adhesion to a substrate or a base, chemically stable, high smoothness, and high insulation. Having, having high wear resistance, etc.

[0002]

2. Description of the Related Art Conventionally, a parallel plate type plasma CVD apparatus as shown in FIG. 2 has been widely known. In FIG. 2, it has a pair of electrodes, a high frequency power supply electrode (2) and a counter ground electrode (3), and the high frequency power supply electrode (2) is connected to a high frequency power supply system (7) via a blocking capacitor (11). Has been done. Further, one of the outputs of the high frequency power supply system (7) is grounded (actually grounded in the vacuum container (1)) and is electrically at the same potential as the counter ground electrode (3). The distance (9) between the high-frequency power supply electrode (2) and the counter ground electrode (3) is 20
It is usually about 60 mm. In the following specification, high frequency means a frequency of 13.56 MHz.

A raw material gas containing a material to be formed is supplied from a raw material supply system (6), and the pressure during the plasma gas phase reaction is measured by a pressure measuring system (5). When the plasma reaction is performed, the high frequency power supply electrode (2) side has a negative potential with respect to the counter ground electrode (3). This is because the difference in mobility (ease of movement) between electrons and ions in plasma causes electric charge to be accumulated in the electrode to which a high frequency is applied.
This phenomenon can be understood as if a negative bias voltage was applied to the high frequency power supply electrode (2) side.
This potential is called self-bias. This potential is also measured using the self-bias monitor terminal (12).
Further, unnecessary gas is exhausted from the exhaust system (8).

The parallel plate type plasma CVD apparatus shown in FIG. 2 uses a high frequency power supplied from a high frequency power supply system (7) to cause a plasma gas phase reaction between the high frequency power supply electrode (2) and the counter ground electrode (3). Then, the film is formed.

Generally, when forming a semiconductor thin film or an insulating film, the substrate is placed on the side of the counter ground electrode (3) to form a film. This is because when the substrate is placed on the side of the high-frequency power supply electrode (2), positive ions are accelerated and plunge into the substrate placed on the side of the high-frequency power supply electrode due to the action of the self-bias described above. This is to prevent damage.

On the other hand, as a method of forming a carbon thin film, which is applied as a surface protective film or wear resistant film of various members, there is a film forming method which effectively utilizes the above-mentioned sputtering effect.

This is because when a hydrocarbon gas, which is a raw material of a carbon thin film, specifically, methane, ethane, propane, alcohol, ethylene, etc. is mixed with hydrogen gas and a film is formed by a plasma CVD method, the above-mentioned sputtering is performed. By utilizing the effect, a film is formed while etching a brittle carbon component such as a graphite component, and as a result, a carbon film having high hardness and high adhesion is formed.

In this case, as shown in FIG. 2, the substrate (4) is placed on the side of the high frequency power supply electrode (2) and film formation is performed. In the case of the device shown in FIG. 2, since the opposing ground electrode (3) and the vacuum vessel (1) have the same potential, the electrode area that acts as the opposing ground electrode also includes the portion including the inner wall of the vacuum vessel. Must be put in. It is known that the self-bias value can be increased as the area of the counter ground electrode (3) is larger than that of the high frequency power supply electrode (2). Generally, as mentioned above, the inner wall of the reaction vessel (1) also works as the opposite ground electrode, so by decreasing the area of the high-frequency power feeding electrode (2), the value of the self-bias applied to the high-frequency power feeding electrode (2) is Can be higher. That is, the value of the self-bias can be controlled by changing the area of the high frequency power supply electrode (2).

[0009]

When a carbon thin film having conditions such as high hardness and good adhesion is to be formed by using the structure shown in FIG. 2, the following problems occur. Become. (A) The film quality of the carbon thin film to be formed can be controlled by the operating pressure, the value of the applied high frequency power, etc. when forming the carbon thin film, but the optimum range of these parameters is not clear. . (B) It has not been possible to obtain a carbon thin film of a certain level or more after practically satisfying the film forming rate which is an element other than the film quality. (C) Not only the pursuit of the quality of the carbon thin film, but also the reduction of damage to the substrate (base) during film formation must be considered. Generally speaking, if too high a hardness is pursued, damage to the base becomes a problem. Therefore, the present invention relates to the above (A) to
It is an object of the invention to solve the problem (C).

<Background of the Invention> The focus of the present invention is that the self-bias is a parameter that plays an important role in realizing the physical properties of a carbon thin film having properties such as high hardness and excellent adhesion to a substrate. It focuses on the value. That is, as a method of evaluating the film quality of the carbon film, there is a method of measuring the hardness of the film itself, but instead of directly measuring the physical properties thereof, various parameters at the time of film formation (for example, operating pressure, Among the applied power, self-bias value, film formation temperature, etc.), which parameter has a large effect on the film quality, in other words, if the parameter value is known, the film quality can be evaluated from that value. Based on the recognition that it is possible, we focused on the value of self-bias as such a parameter.

From the above viewpoints, the present invention experimentally finds various conditions that can realize the required self-bias value, and clarifies the correlation between them to obtain a good film quality. The production conditions are such that a carbon thin film can be stably obtained at a high film formation rate. In the following (1) to (4), optimum values and correlations of various parameters obtained experimentally are briefly summarized. (1) The pressure during film formation should be as high as possible with the upper limit being about 100 Pa. (2) The optimum value of the self-bias that does not damage the base is in the range of -350V to -450V. (3) The value of high frequency power to obtain good film quality is 2W / cm
A range of about ^{2 to 3} W / cm ² is preferable. (4) The ratio of the distance between electrodes and the electrode area (distance between electrodes / electrode area) that simultaneously satisfy the above conditions (1) to (3) is:
It is in the range of about 1/1963 to 1/314. Therefore, this (4)
By realizing the film forming conditions that satisfy the conditions shown in, a carbon thin film that satisfies the necessary conditions can be obtained.

The optimum conditions of the various parameters shown in (1) to (4) above and the basis of the correlation satisfying the optimum conditions will be described below.

[Regarding (1)] The pressure during film formation should be as high as possible. because,
The high pressure of the film forming atmosphere means that the raw material gas contains a large number of molecules and active species per unit volume, which greatly contributes to the improvement of the film forming rate. In fact, the higher the film formation pressure, the higher the film formation rate, and the higher the productivity.

However, the self-bias value, which is considered to play a major role in forming a high-quality carbon thin film, does not stably occur at a pressure of about 100 Pa or more, and even if the film is formed, the quality is low. It has been experimentally confirmed that only the above film can be obtained.

Therefore, it is concluded that in order to form a carbon film with good reproducibility while maintaining a high film forming rate, it is preferable to form the film in a pressure atmosphere as high as possible within a pressure range of about 100 Pa or less.

[Regarding (2)] FIG. 3 shows the relationship between the value of the self-bias and the Vickers hardness which is a parameter for evaluating the film quality of the carbon film formed on the substrate. The data shown in FIG. 3 was obtained by the apparatus shown in FIG. The device shown in FIG. 1 has basically the same structure as the device shown in FIG. 2, and the structure and role of each part are also the same as the device shown in FIG. The plasma CVD apparatus shown in FIG. 1 is different from the apparatus shown in FIG.
(9) is as narrow as 9 mm or less.

The value of the self-bias shown in FIG. 3 is measured at the self-bias monitor terminal (12) as to how many volts the potential of the high frequency power supply electrode (2) is with respect to the ground potential. The Vickers hardness is a parameter indicating the hardness of the carbon film, and was used here as a parameter for evaluating the film quality of the carbon thin film. Of course, the film quality of the carbon thin film cannot be evaluated only by Vickers hardness, but it is effective to use it as one index.

The data shown in FIG. 3 are obtained by using the apparatus shown in FIG. It is a graph showing the relationship between the value of the self-bias and the Vickers hardness of the formed carbon thin film at that time. The film forming conditions are shown below. Reaction gas: Ethylene 200sccm: Hydrogen 50sccm Distance between electrodes: 8mm Substrate: Si wafer with 6 inch diameter Substrate temperature: Unheated

As is clear from FIG. 3, there is a clear correlation between the Vickers hardness and the value of self-bias. If a carbon thin film having a Vickers hardness of 3000 (Kg / mm ² ) or more is defined as significant, the self-bias during film formation is constant if the film is formed in the range of about -350V to about -500V. It is concluded that a carbon thin film above the standard can be obtained.

However, when the self-bias exceeds -450 V, there is a problem that the etching mode becomes more dominant than the deposition mode and the film forming rate is extremely lowered. As described above, the film formation method that positively uses the self-bias is a method of forming a film while etching unnecessary components having a low hardness. Therefore, if the etching degree is too high, a carbon component having a high hardness required. This also hinders the film formation, and as a result, the film formation speed is reduced.
Therefore, considering the factor of the film formation rate, it is effective to set the upper limit of the self-bias shown in FIG. 3 to about -450V.

Furthermore, considering that a carbon thin film is generally used as a surface coating film, it is of course necessary to consider an ion bombardment of a resin or the like or a base which is weak against heat generation due to the ion bombardment, and ion bombardment is necessary. It is also necessary to keep it to a minimum. Therefore, also from this, it is concluded that the film formation in which the etching mode is too dominant is not preferable.

From the above, if a carbon thin film having a hardness of 3000 (Kg / mm ² ) or more as measured by Vickers hardness is to be obtained, the value of the self-bias during film formation is -350 to -500.
It is concluded that V is suitable, and -350 to -450 V is suitable when the film forming speed and damage to the base are taken into consideration.

[Regarding (3)] In the present specification, the gas phase reaction is obtained by dividing the electric power (W) supplied from the high frequency power supply system (7) by the area (cm ² ) of the high frequency power supply electrode (2). It is defined as the electric power (W / cm ² ) input for

One of the problems to be solved by the present invention is to form a carbon thin film having a film quality of a certain level or higher at a high film forming rate. To get a high deposition rate,
It is preferable to form a film at an operating pressure as high as possible as shown in (1). On the other hand, it has been empirically proved that when the operating pressure is increased, the required high frequency power value may be low. For example, it has been known that when the operating pressure is 110 Pa, a carbon thin film having a Vickers hardness of 3000 Kg / mm ² or more can be obtained with an input power of 1.0 to 2.7 W / cm ² . However, the carbon thin film obtained in this case contains a cluster component in the film and is not necessarily preferable as the film quality. Moreover, it is not preferable to set the operating pressure to 100 Pa or more, because there are problems such as instability of self-bias and peeling of the formed thin film from the substrate.

On the other hand, when the operating pressure is low, 3 W / cm ²
The above input power is required, and problems such as damage to the substrate and a decrease in film formation rate due to low operating pressure are problems, which is also not preferable.

Therefore, within the operating pressure range of 50 Pa to 100 Pa where a high film formation rate can be expected and a good film quality can be expected due to stable self-bias, damage to the substrate is reduced and peeling from the substrate is prevented. It is concluded that an input power of about ² to 3 W / cm ² is suitable for realizing the conditions such as prevention and formation of a carbon thin film having a Vickers hardness of a certain level or more.

[Regarding (4)] According to an experiment conducted by the present inventors using the apparatus shown in FIG. 1, the value of the self-bias applied to the high-frequency power feeding electrode (2) is changed by changing the inter-electrode distance (9). It has been found that can be changed. On the other hand, it is conventionally known that the value of the self-bias applied to the high frequency power supply electrode (2) can be changed by changing the area of the high frequency power supply electrode (2).

Therefore, the present inventors have proposed the high frequency power supply electrode (2).
Film formation was performed under various film formation conditions using the and the ground electrode (3) as a circular electrode, and the results were organized and examined. As a result, it was found that there is a correlation between the diameter of the circular electrodes and the ratio between the electrodes (9) when a carbon film having good film quality is obtained.

Therefore, FIG. 4 shows the data arranged by plotting (distance between electrodes) / (diameter of circular electrode) on the horizontal axis and the value of self-bias applied to the high-frequency power supply electrode (2) on the vertical axis.
Is. The same electrode was used for the high frequency power supply electrode (2) and the counter ground electrode (3), and the self bias was measured at the self bias monitor terminal (12).

The reaction conditions are shown below. These reaction conditions are desirable film formation conditions such as an operating pressure capable of obtaining the required film formation rate, and an input power that does not damage the film quality or the underlying substrate. .

Therefore, if a carbon thin film having a sufficient film quality can be obtained under the following film forming conditions, the problem to be solved by the present invention will be solved. Reactive gas: Ethylene 200sccm: Hydrogen 50sccm Operating pressure: 70Pa High frequency power: 2.0 W / cm ²

Referring to FIG. 4, by setting the value of (distance between electrodes) / (diameter of circular electrode) to about 1/50 to 1/20,
It can be seen that a self-bias value of -350 to -500V during film formation, which is an index for determining that the carbon thin film is at a certain level or higher, is obtained.

Here, the area of the circular electrode having a diameter r is πr ²
Therefore, if the above relationship is rewritten as the relationship between the distance between electrodes and the electrode area, the range of the value of (distance between electrodes) / (electrode area) should be about 1/1963 to 1/314. Become. By using this relationship, it is possible to calculate the relationship between the electrode interval and the electrode size that can obtain a desired self-bias even when using an electrode having a shape other than a circular shape.

[0034] For example, when using a rectangular electrode diagonal L (square), the area of the square electrode is L ^2/2 So, the value a schematic of (area of the electrode) (distance between electrodes) / 1/1963 ~ 1/314
To ^{The, L 2/2 = 1963∴L ≒} 63, L 2/2 = 314
Since ∴L≈25 is calculated, the value of (distance between electrodes) / (diagonal dimension of square electrode) should be approximately 1/63 to 1/25. When using a rectangular electrode, etc.,
The relationship between the area and the inter-electrode distance may be calculated in accordance with the above relationship, but if not extreme rectangle, to estimate the area from the diagonal length L and L ^2/2, the distance between the electrodes and the electrode area The relationship of can be used.

As described above, the self-bias value required to obtain a carbon film having a film quality of a certain level or more is set at an operating pressure of 50 Pa or more at which a high film forming rate is obtained, and the underlying substrate is less damaged. To obtain a power value of about ² W / cm ^2, the value of (distance between electrodes) / (diameter of circular electrode) is 1/50
It is concluded that the reaction should be performed by setting it to about 1/20.

[0036]

The present invention has been made based on the background of the invention described above, and has the following contents.

[First Invention] A first invention has a first prismatic electrode connected to a high frequency supplying means and a second prismatic electrode kept at a ground potential,
The distance between the first rectangular electrode and the second rectangular electrode is 9 mm or less and the minimum value is 5 mm, and the distance between the electrodes is a pair of the first rectangular electrode and the second rectangular electrode. Using a plasma CVD apparatus having an angular distance of 1/63 to 1/25, plasma is generated by supplying high-frequency power from the high-frequency supplying means to the first rectangular electrode to decompose the hydrocarbon gas, thereby decomposing the first gas. a carbon thin film forming method of forming a carbon thin film arranged substrates 1 of rectangular electrodes, operating pressure
The power is 50 Pa or more and 100 Pa or less, and the high frequency power is
Is 2 W / cm 2 or more and 3 W / cm 2 or less, and the potential of the first rectangular electrode is −500 V or more −3 with respect to the ground potential.
The gist is a method for forming a carbon thin film, which comprises forming a carbon thin film at 50 V or less. This first
According to the invention of (1), when the carbon thin film is formed, the potential (self-bias value) with respect to the ground potential of the electrode on which the substrate is arranged is set to −350 to −500 V to form a film.
It is based on the experimental finding that a carbon thin film having a significant film quality can be obtained.

[ Second Invention] In the second invention, the first invention connected to the high frequency supplying means
And the second rectangular electrode kept at ground potential.
The first rectangular electrode and the second rectangular electrode.
The distance between the electrodes is 9 mm or less, the minimum value is 5 mm, and
The distance between the electrodes is the first rectangular electrode and the second rectangular electrode.
Plasma C which is 1/63 to 1/25 of the diagonal distance of the electrodes
A hydrocarbon gas is used in the plasma CVD device using a VD device.
Gas and hydrogen gas are supplied to the first rectangular electrode to
Plasma is generated by supplying high frequency power from the frequency supply means.
And decompose the hydrocarbon gas to decompose the first rectangular electrode.
Method for forming carbon thin film on carbon substrate
The operating pressure is 50 Pa or more and 100 Pa or less.
And, the high frequency power 2W / cm ² or more 3W / cm ² or more
Below, the potential of the first rectangular electrode is set to the ground potential.
A carbon thin film forming method is characterized in that a carbon thin film is formed at −500 V or more and −350 V or less . In the second invention, the value of the self-bias is
To form a significant carbon thin film at -350 to -500V,
This is based on experimental confirmation that it is effective to use a hydrocarbon gas and a hydrogen gas as the reaction gas and set the film forming conditions to the above conditions.

As the hydrocarbon gas, ethylene, methane, butane, ethane, alcohol or the like can be used. It is also effective to introduce another reactive gas in addition to the hydrocarbon gas and the hydrogen gas during film formation in order to add impurities into the carbon thin film.

By setting the electrode size and the electrode interval within the range of a specific numerical value, it is possible to obtain a carbon thin film satisfying the conditions of high film forming rate, film quality above a certain level, and reduction of damage to the underlayer. it can.

[0041]

EXAMPLES In the following, the plasma CV shown in FIG.
An example in which a carbon thin film is formed under the film forming conditions of the present invention by using a D device will be shown.

[Plasma CVD Apparatus] FIG. 1 shows a plasma CVD apparatus used in the following examples. The basic structure of this apparatus is the same as that of the conventional plasma CVD apparatus shown in FIG. 2, but is characterized in that the interelectrode distance (9) is set as narrow as 9 mm or less.

In FIG. 1, a plasma region (10) is formed by a vacuum container (1) for performing a plasma reaction inside and a high frequency (13,56 MHz) supplied from a high frequency power supply system through a blocking capacitor (11). A pair of electrodes for
(2), (3), raw material supply system (6) for supplying reaction gas and raw material gas, further carrier gas and dilution gas, exhaust system (8) for exhausting unnecessary gas, film formation The substrate or substrate to be performed (4), the pressure measurement system (5) for measuring the pressure inside the reaction vessel, and the self-bias monitor terminal (1 for measuring the self-bias applied to the electrode (2) during the plasma reaction.
2) is equipped. In addition, the electrode (2) is
(3) is called a counter ground electrode. One of the outputs of the high frequency power supply system (7) and the opposing ground electrode (3) are grounded to the vacuum container (1).

Example 1 In this example, the electrodes (2) and (3) having the same size and shape were used, and the relationship between the diagonal size L and the distance d between the electrodes was calculated.
This is an example when d / L = 1/30 . The carbon thin film was formed under the following conditions. Reaction gas: Ethylene purity 99.99% 200SCCM Hydrogen purity 99.999% 50SCCM High frequency power: 2.2W / cm ² (13.56MHz) Electrode dimensions: 180mm × 180mm (diagonal 255mm square) Distance between electrodes: 8.5mm Operating pressure: 75Pa Substrate: 0.5mm thick, 6 inch diameter Si wafer Substrate temperature: No heating Reaction time: 2min Self-bias: -380V Formation rate: 1.7μm / min Vickers hardness : 3900Kg / mm ²

At this time, since the reaction time was set to 2 min, Si
A diamond-like carbon thin film of about 3.4 μm was formed on the wafer. This diamond-like carbon thin film was not peeled off from the substrate at all, and was uniformly formed on the entire surface. Furthermore, when the Vickers hardness was measured, a very clear indentation was produced, and it was found from the formula that the hardness was 3900 kg / mm ² .

Under the above film forming conditions, only hydrogen gas was introduced at 200 sccm and plasma reaction was performed at a high frequency power of ² W / cm ² , and the operating pressure value and the self-bias monitor terminal (12) were measured. Figure 5 shows the relationship with the bias value.
Indicated by a black circle. From this figure, the desired self-bias value
It can be seen that -350 to -450V is obtained at about 50Pa or more.

COMPARATIVE EXAMPLE 1 In the comparative example, the conventional apparatus shown in FIG.
In the condition shown in, introducing only 200 sccm of hydrogen gas,
The relationship between the value of the operating pressure and the value of the self-bias measured at the self-bias monitor terminal (12) when the gas phase reaction was performed at a high frequency power of ² W / cm ² (13.56 MHz) was investigated.
The electrode spacing (9) was 30 mm.

The data obtained in this comparative example are shown by white circles in FIG. In this case, if the operating pressure is set to 75 Pa, which is the same as in Example 1, the self-bias decreases to -230 V, and it can be seen that effective film formation cannot be performed. In fact, the carbon thin film obtained under the operating pressure of 75 Pa and the reaction time of 2 min had a film thickness of about 0.6 μm, but the Vickers hardness was 2100 kg / mm ²
Therefore, neither the film forming rate nor the hardness is satisfactory.

Comparative Example 2 Under the reaction conditions of Example 1, when the operating pressure was set to 20 Pa, the self-bias became −520V. The formed thin film was remarkably peeled, and the film thickness and Vickers hardness could not be evaluated due to an increase in the residual internal stress of the film itself. It is considered that this is because the self-bias is too high, the etching mode is dominant over the deposition mode, and the ion impact due to the action of the self-bias is large.

Example 2 Under the film forming conditions shown in Example 1, the mixing ratio of the reaction gas,
An example in which the film formation is performed under the condition that the value of the high frequency power, the value of the operating pressure, and the distance between the electrodes are independently changed is shown as [Examples 2 to 6] below. The film forming apparatus shown in FIG. 1 was used, and the electrode structure and electrode spacing were the same as in Example 1.

The film forming conditions are shown below. Reaction gas: Ethylene purity 99.99% 200SCCM Hydrogen purity 99.999% 5SCCM High frequency power: 2.2W / cm ² (13.56MHz) Electrode dimensions: 180mm × 180mm (diagonal 255mm square) Distance between electrodes: 8.5mm Operation Pressure: 75Pa Substrate: 0.5mm thickness, 6 inch diameter Si wafer Substrate temperature: No heating Reaction time: 2min Self-bias: -355V Deposition rate: 2.1 μm / min

The Vickers hardness of the obtained carbon thin film is 33.
It was 50 Kg / mm ² . The film forming conditions are different from those in Example 1
The reason is that the amount of hydrogen added to ethylene was reduced from 25% to 2.5%. As a result, the self-bias value was slightly lowered, the film formation rate was increased, and the Vickers hardness was decreased.

[Embodiment 3] This embodiment is an example of forming a film under the film forming conditions of Embodiment 1 while setting only the high frequency power value to 2.8 W / cm ² . The various parameters are listed below. High frequency power: 2.8 W / cm ² Self-bias: -430 V Deposition rate: 1.95 μm / min Vickers hardness: 4600 Kg / min In this example, the value of high frequency power was 2.2 W / cm ^{2 of} Example 1.
By making it higher, the film formation rate can be increased,
The Vickers hardness could be considerably increased to 4600 Kg / cm ² .

[Embodiment 4] In this embodiment, under the film forming conditions of Embodiment 1, the operating pressure is
This is an example when it is set to 55Pa. Various parameters are listed below. Operating pressure: 55Pa Self-bias: -420V Deposition rate: 1.45μm / min Vickers hardness: 4250Kg / mm ^{2 In} this example, the operating pressure was changed from 75Pa in Example 1 to 55Pa.
By lowering the Pa, the film formation rate will increase from 1.7 μm to 1.45 μm.
However, the Vickers hardness of the obtained carbon thin film could be increased to 4250 Kg / mm ² .

[Embodiment 5] In this embodiment, the operating pressure is changed under the manufacturing conditions of Embodiment 1.
It is as high as 95Pa. Various parameters are listed below. Operating pressure: 95 Pa Self-bias: -350 V Deposition rate: 2.3 μm / min Vickers hardness: 3050 Kg / mm ^{2 In} the case of this example, the deposition rate could be increased by increasing the operation pressure. The Vickers hardness, which is a parameter for evaluating the film quality, was lower than that in Example 1.

[Embodiment 6] In this embodiment, the distance between the electrodes is changed under the film forming conditions of Embodiment 1.
This is an example with 5 mm. That is, this is an example in which the value of (distance between electrodes ) / (diagonal distance of square electrodes) is about 1/51 . Distance between electrodes: 5mm Self-bias: -480V Deposition rate: 1.2μm / min Vickers hardness : 3400Kg / mm ²

By reducing the distance between the electrodes to 5 mm, a carbon thin film of a certain level or more could be obtained. However, it was technically difficult to further reduce the electrode interval (9). This is because: • The distance between the electrodes (9) is shortened, so that the surface of the substrate is affected by the brittle carbon component formed on the side of the counter ground electrode.・ When the distance between electrodes (9) is less than 5 mm, the parallelism of the electrodes,
Since the flatness, the arrangement accuracy of the substrate, and the like influence the way of discharge, stable plasma cannot be generated, and the reproducibility of film formation becomes difficult. -It becomes difficult to arrange the board and work. -Since it becomes difficult to uniformly supply the source gas between the electrodes, the reproducibility of film formation cannot be obtained. This is because there are problems such as

Therefore, it is concluded that the minimum value of the inter- electrode distance in actual use is about 5 mm.

[0059]

EFFECT OF THE INVENTION Self-bias during plasma reaction is -350 to
By forming the film within the range of -500V, a carbon thin film having a film quality of a certain level or higher can be obtained.
Further, by setting the ratio between the dimension of the pair of electrodes and the distance between the electrodes to a specific value, a film quality of a certain level or higher can be obtained while satisfying conditions such as high film formation rate and reduction of plasma damage. be able to.

[Brief description of drawings]

FIG. 1 is a high-frequency plasma C used in this embodiment.
It is sectional drawing which shows the internal structure of a VD apparatus.

FIG. 2 Conventionally used high-frequency plasma CVD
It is sectional drawing which shows the internal structure of an apparatus.

FIG. 3 shows the relationship between the value of the self-bias during film formation and the Vickers hardness of the formed carbon thin film.

FIG. 4 shows the relationship between the value of (electrode interval) / (diameter of circular electrode) and the value of self-bias during plasma reaction when a circular electrode is used as an electrode.

FIG. 5 shows the relationship between operating pressure and self-bias in Examples and Comparative Examples.

[Explanation of symbols]

1 vacuum container 2 High frequency power supply electrode 3 Opposite ground electrode 4 substrates 5 Pressure measurement system 6 Raw material supply system 7 High frequency power supply system 8 exhaust system 9 Distance between electrodes 10 plasma region 11 Blocking condenser 12 Self-bias monitor terminal

Claims (3)

(57) [Claims] 1. A first prismatic electrode connected to a high-frequency supply means, and a second prismatic electrode kept at a ground potential, wherein the first prismatic electrode and the second prismatic electrode are connected to each other. A plasma CVD apparatus in which the distance between electrodes is 9 mm or less and the minimum value is 5 mm, and the distance between the electrodes is 1/63 to 1/25 of the diagonal distance between the first rectangular electrode and the second rectangular electrode. Using the above, the high frequency power is supplied from the high frequency supply means to the first rectangular electrode to generate plasma, and the hydrocarbon gas is decomposed to form a carbon thin film on the substrate arranged on the first rectangular electrode. A method for forming a carbon thin film, the operating pressure being 50 Pa or more and 100 Pa or less,
A method for forming a carbon thin film, characterized in that the wave power is set to 2 W / cm 2 or more and 3 W / cm 2 or less and the potential of the first rectangular electrode is set to -500 V or more and -350 V or less with respect to the ground potential. 2. A first prismatic electrode connected to a high-frequency supplying means, and a second prismatic electrode kept at a ground potential, wherein the first prismatic electrode and the second prismatic electrode are connected to each other. A plasma CVD apparatus in which the distance between electrodes is 9 mm or less and the minimum value is 5 mm, and the distance between the electrodes is 1/63 to 1/25 of the diagonal distance between the first rectangular electrode and the second rectangular electrode. By supplying a hydrocarbon gas and a hydrogen gas to the plasma CVD apparatus, by supplying high-frequency power from the high-frequency supply means to the first rectangular electrode to generate plasma, and decompose the hydrocarbon gas. A carbon thin film forming method for forming a carbon thin film on a substrate arranged on the first rectangular electrode, wherein an operating pressure is 50 Pa or more and 100 Pa or less, and the high frequency power is 2 W / cm ² or more and 3 W / cm ² or less, The first prism A method for forming a carbon thin film, comprising forming a carbon thin film by setting an electrode potential to -500 V or more and -350 V or less with respect to a ground potential. 3. The method for forming a carbon thin film according to claim 1 or 2, wherein the hydrocarbon gas is ethylene, methane, butane, ethane or alcohol.