JPH0797690A - Plasma cvd device - Google Patents

Abstract

PURPOSE:To improve the uniformity of a film thickness even for a wafer having a large diameter by providing at least one of a pair of discharge electrodes with a gas introducing port consisting of a metallic porous body in the plasma CVD device with which the feed gas for forming the film is subjected to plasma decomposition in the vicinity of the substrate. CONSTITUTION:A pair of the parallel disk type discharge electrodes 31 and 3 are placed opposite each other perpendicularly in the vacuum vessel 1 and the discharge electrode 31 is grounded and the electrode 3 is connected to the high frequency power source 4. Then feed gas consisting of Ar and methanol 6 is introduced into the vacuum vessel 1 and a plasma is generated between the electrodes 31 and 3 to activate the feed gas and to deposit a diamond-like carbon film on the silicon wafer 35a. In this device, the gas introducing part of the electrode 31 is fitted with a stainless steel sintered filter consisting of a metallic porous body through which the feed gas is introduced. Thus, the feed gas can be finely and uniformly introduced into the plasma atmosphere and the uniformity of the film thickness distribution even for a wafer having a large diameter up to about 5in. can be remarkably improved.

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 for plasma-decomposing a raw material gas of a film in the vicinity of a base material to deposit a thin film on the base material, and particularly introducing the raw material gas through a porous metal electrode. Thus, the present invention relates to a plasma CVD apparatus capable of significantly improving the uniformity of film thickness distribution.

[0002]

2. Description of the Related Art Generally, the surface of a high-performance material is treated. For example, functions such as decorativeness, corrosion resistance, and abrasion resistance are exhibited depending on the surface state of the material, and the bulk is often a simple structure. Therefore, in recent years, a technique for forming a thin film by a vapor phase method has become more and more important as a method of surface-treating a material to increase its utility value.

This type of thin film forming technology is roughly classified into physical vapor deposition (PVD) and chemical vapor deposition (CVD).
For example, each method is appropriately selected in accordance with a wide variety of requirements such as abrasion resistance, heat resistance, and photoelectric conversion. In particular, the CVD method has been widely used since 1963 as a surface treatment method for semiconductors, which are high value-added materials.

In this CVD method, some energy is added to the raw material gas supplied into the vacuum vessel to decompose and activate it.
It is a technique for forming a thin film on the surface of a clean base material placed in a vacuum container, and various methods have been developed.

First, the thermal CVD method is a technique that was initially developed and is widely used, for example, for forming a hard coating film of TiN. In addition, MOCVD (Metal organic CVD)
Method and photo CVD method are widely used as a compound semiconductor device development technology. These CVD methods are techniques for activating a raw material gas for a thin film with thermal energy.

However, in this type of CVD method, the process temperature sometimes exceeds 1000 ° C., which makes it difficult to use a substrate having no heat resistance.

Therefore, in order to lower the temperature of the process, a plasma CVD method for activating a raw material gas with electric energy has been developed and studied. For example, plasma under low pressure
Although the electron temperature is as high as several thousand degrees, decomposition and activation of the raw material gas are promoted, but the atmospheric temperature is kept low because the electron mass is extremely small. Therefore, the plasma CVD method enables film formation over a wide range at low temperature regardless of whether it is a solid or a flat surface, as compared with the above-described CVD method.

FIG. 3 is a schematic view showing the structure of this type of plasma CVD apparatus.

In this plasma CVD apparatus, a pair of parallel plate type discharge electrodes 2 and 3 are arranged vertically opposite to each other in a vacuum container 1 capable of evacuating to 10 ^-4 Pa.
Each of the discharge electrodes 2 and 3 has a diameter of 130 mm and a thickness of 8 mm.
The upper discharge electrode 2 is made of stainless steel and has a disk shape, and the upper discharge electrode 2 arranged above is grounded. In addition, the lower discharge electrode 3 arranged below is at 13.56 MHz, 200
A substrate (base material) 5 which is connected to a high frequency power source 4 for inputting a high frequency power of W and which deposits a film is placed.

On the other hand, the vacuum container 1 is communicated with the raw material gas container 7 containing the methanol 6 through the raw material gas introduction pipe 8, and the raw material gas container 7 receives Ar gas from the Ar gas introduction pipe 9. Methanol and Ar are mixed at a ratio of 9: 1 to generate a raw material gas, and the raw material gas is introduced into the vacuum container 1 through the raw material gas introduction pipe 8. The source gas introduction pipe 8 is a 1/4 inch stainless steel pipe, and the gas introduction port at the tip end faces between the discharge electrodes 2 and 3.

Therefore, between the discharge electrodes 2 and 3, the source gas containing methanol (CH ₃ OH) is decomposed and activated to generate plasma, and a thin film of diamond-like carbon is formed on the substrate 5.

Here, for example, the substrate 5 has a thickness of 0.3.
Film formation is performed using a silicon wafer 5a having a diameter of 5 mm and a diameter of 5 inches. The silicon wafer 5a has a high flatness as a result of observation that interference fringes formed by laser irradiation before film formation are observed, and the interference fringes show a concentric pattern and the intervals of the stripes are uniform. It has been confirmed.

Next, this silicon wafer 5 is placed on the lower discharge electrode 3, 10 Pa of the above-mentioned raw material gas is introduced, and high-frequency power of 200 W is applied to each discharge electrode 2, 3 to form plasma. , On the silicon wafer 5a
A diamond-like carbon film is formed only for 0 minutes.

After the film formation, the interference fringes are observed on the silicon wafer 5a in the same manner as described above, and the observation result that the pattern of the interference fringes is distorted and disturbed is obtained. As a result of measuring the film thickness on the silicon wafer 5a, the film thickness is 0.2.
μm is obtained.

Subsequently, a glass wafer 5b having a thickness of 1 mm and a diameter of 5 inches is used to form a film as described above.

After the film formation, the glass wafer 5b was measured for visible light transmittance at 20 points within a diameter of 5 inches, and the film pressure distribution was calculated by the following equation (1).

[0017]

[Equation 1] As a result of measurement and calculation, the obtained film thickness is 0.2 μm and the film thickness distribution is ± 23%. In addition, fine powder that is considered to have been generated by a gas phase reaction adheres to the inner wall of the vacuum container.

Therefore, in such a plasma CVD apparatus, it is necessary to improve at least the uniformity of the film thickness distribution.

Therefore, the structure shown in Japanese Patent Publication No. 59-48138 is considered. FIG. 4 is a schematic diagram showing the configuration of such a plasma CVD apparatus.

This plasma CVD apparatus includes a vacuum container 11
A pair of parallel-plate type discharge electrodes 12 and 13 are vertically arranged inside each other, and high-frequency power can be supplied to each discharge electrode 12 and 13. Here, the upper discharge electrode 12 arranged above holds the substrate 14. Further, the lower discharge electrode 13 arranged below is provided with the gas discharge hole 1
5 has two electrode surfaces 13a and 13b, and each of the electrode surfaces 13a and 13b is formed by stacking with a space therebetween.

As a result, the source gas is supplied from a gas supply source (not shown) into the lower discharge electrode 13 through the gas introduction pipe 16, and the gas discharge holes 15 of the electrode surfaces 13a and 13b are provided.
Is introduced into the space between the discharge electrodes 12 and 13 in the vacuum chamber 11 and plasma is formed between the electrodes 12 and 13 to form the substrate 1.
4 to produce a thin film. In the plasma CVD apparatus, the diameter of the gas release hole 15 is about 3 mmΦ, the surface density of the holes 15 is 4 / cm ² , and the glass substrate 14 of 50 mm × 50 mm is used.
A thin film having a film thickness unevenness of ± 4% is obtained above.

Further, there is a structure shown in Japanese Patent Publication No. 5-27494. FIG. 5 shows such plasma CVD
It is a block diagram which fractures | ruptures and shows a part of apparatus.

In this plasma CVD apparatus, a substrate holder 21 for holding a substrate and a discharge electrode 23 composed of a pair of electrode surfaces 23a and 23b having a gas discharge hole 22 are vertically arranged in a vacuum container 24. There is. Discharge electrode 23
Is capable of supplying high-frequency power to the electrode surfaces 23a and 23b, and is supplied from a gas supply source (not shown) through the gas introduction pipe 26 filled with the stainless mesh 25.
The raw material gas can be supplied to a and 23b.

As a result, the raw material gas passes through the stainless mesh 25 in the gas introduction pipe 26 and the respective electrode surfaces 23a, 2a.
It is supplied to the plasma space in 3b and activated in the plasma space to form a thin film on the substrate.

[0025]

However, in the plasma CVD apparatus as described above, the film thickness within a 5 inch diameter fluctuates by ± 23%, so that there is a problem that the uniformity of the film thickness distribution is low.

On the other hand, the plasma CVD shown in Japanese Patent Publication No. 59-48138 and Japanese Patent Publication No. 5-27494.
In the apparatus, since the thin film formation region is very narrow, about 2 inches in diameter, there is a problem that it does not contribute to improving the uniformity of the film thickness distribution on a large diameter wafer of about 5 inches.
That is, since it is difficult to improve the uniformity of the film thickness distribution in accordance with the increase of the film formation region, the Japanese Patent Publication No. 59-48.
The uniformity of ± 4% at the diameter of 2 inches shown in Japanese Patent No. 138 is, even at the best evaluation, ± 10 at the diameter of 5 inches.
Only% uniformity is supported.

Further, in the plasma CVD apparatus shown in each publication, when the source gas is introduced, the gas introduction pipe 16,
In the vicinity of the central portion of the electrode surfaces 13a-b and 23a-b facing the electrode 26, gas easily escapes, and the electrode surfaces 13a-b, 23a-b
Since the gas is relatively hard to escape near the edge of the wafer, the film thickness at the center of the wafer tends to be thick and the film thickness at the edge of the wafer tends to be thin. This tendency is obtained regardless of the presence or absence of the stainless mesh 25 in the gas introduction pipes 16 and 26.
This is an essential problem resulting from the introduction of gas through the gas release holes 15,22 facing 6,26. Further, along with this, since the density of the raw material gas becomes uneven in the plasma, there is a problem that a part of the raw material gas reacts in the gas phase to generate fine powder.

Further, since one discharge electrode 13, 23 has two electrode surfaces 13a-b, 23a-b, it has a complicated structure for a narrow area of about 2 inches in diameter. There is.

As described above, the current technology has a problem that the film thickness distribution is only ± 10%, or at most ± 5%, in the area of less than 3 inches in diameter.

The non-uniformity of the film thickness distribution indicates the non-uniformity of the plasma atmosphere at the film forming site, and the non-uniformity of the plasma atmosphere indicates the non-uniformity of the film characteristics.

On the other hand, the uniformity of film characteristics is highly required especially in the field of electronic materials. For example, in the case of an X-ray transparent film for an X-ray mask for producing a highly precise fine pattern, the film thickness distribution is ± 3% or less. In some cases, a strict value of about ± 1% is required.

However, since a technique for arbitrarily controlling the plasma atmosphere has not been established, the range of 3 inches or more is ± 3.
There is not yet a device for producing a thin film with a film thickness distribution of less than%.

The present invention has been made in consideration of the above situation, and by uniformly introducing a source gas into a plasma atmosphere through a porous metal electrode, even in a large-diameter wafer, a uniform film thickness distribution is obtained. Plasma C that can significantly improve the properties
An object is to provide a VD device.

[0034]

In order to achieve the above object, the present invention provides a pair of discharge electrodes opposed to each other in a vacuum vessel, introducing a raw material gas into the vacuum vessel, and A plasma CVD apparatus for forming a thin film on a predetermined substrate in the vacuum container by supplying electric power to at least one of the discharge electrodes to generate plasma between the discharge electrodes to activate the source gas, This is a plasma CVD apparatus in which at least one of the discharge electrodes is provided with a gas introduction port made of a porous metal body.

[0035]

Therefore, according to the present invention, by taking the above-mentioned means, since at least one of the discharge electrodes is provided with the gas inlet port made of the metal porous body, the source gas is porous. Uniformity of the film thickness distribution can be remarkably improved by uniformly introducing it into the plasma atmosphere through the metal electrode of the solid body.

[0036]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows a plasma C according to an embodiment of the present invention.
FIG. 2 is a schematic diagram showing the configuration of a VD apparatus, FIG. 2 is a sectional view showing the configuration of a gas inlet and one discharge electrode applied to this plasma CVD apparatus, and the same parts as those in FIG. The detailed description thereof will be omitted and only different parts will be described here.

That is, the apparatus of this embodiment is intended to make the plasma atmosphere uniform in order to improve the uniformity of the film thickness distribution. Specifically, in comparison with the apparatus shown in FIG. The source gas introduction pipe 8 communicating with 7 is connected to the vacuum container 1
Is arranged toward the lower discharge electrode 3 below through the upper outer wall, and the gas introduction electrode portion 31 shown in FIG. 2 is attached to the tip portion 8a of the source gas introduction pipe 8 in place of the upper discharge electrode 2. ing.

Here, the gas introducing electrode portion 31 is formed into a paraboloid of revolution having a maximum diameter of 130 mm, and a gas diffusion member 32 having a 1/4 inch diameter through hole 32a formed in the upper center portion. And a diameter of 130 m attached so as to close the 130 mm opening 32b of the gas diffusion member 32.
m-shaped and 2 mm-thick disc-shaped stainless sintered filter 33
And the stainless sintered filter 33 is attached to the gas diffusion member 3
And a cover 34 for fixing to the second opening 32b.

The gas diffusion member 32 is provided with respect to the source gas introduction pipe 8 which is a 1/4 inch diameter stainless pipe so that the tip 8a of the introduction pipe 8 is passed through the through hole 32a.
It has a function of diffusing the raw material gas, which is brazed to and introduced from the raw material gas introduction pipe 8, according to the expansion of the diameter and supplying it to the stainless sintered filter 33.

The stainless sintered filter 33 is a grounded conductive metal porous body and has a function of uniformly introducing the raw material gas supplied from the gas diffusion member 32 into the vacuum container 1. It is also possible to substitute the metal porous body of. As another metal porous body, for example, a laminate of metal meshes of various sizes can be used.

Further, the stainless sintered filter 33 is set to have an opening of 40 μm. In addition, this opening is
If it is small, the gas introduction amount is reduced and the film formation efficiency is reduced.
If it is large, it hinders the uniform diffusion of the raw material gas.
It is set in the range of 5 μm to 150 μm, and among them, 20
The range of μm to 40 μm is a more preferable setting. Further, the stainless sintered filter 33 has an opening of 40.
Since it is as small as μm, it does not affect the potential distribution, and therefore has a function of making the potential distribution uniform at zero potential when used as a ground electrode.

Next, the operation of such a plasma CVD apparatus will be described.

As described above, the silicon wafers 35a and 35b having a thickness of 0.3 mm and a diameter of 5 inches are placed on the lower discharge electrode 3. It is confirmed that the silicon wafer 35a has a high flatness by observation of interference fringes by laser irradiation.

Subsequently, the vacuum container 1 is depressurized to a predetermined vacuum degree of 10 ^-4 Pa.

When the vacuum degree of the vacuum container 1 reaches 10 ⁻⁴ Pa, Ar gas is introduced into the raw material gas container 7 through the Ar gas introduction pipe 9 and is mixed with the methanol 6 in the raw material gas container 7 to produce methanol. A raw material gas having a ratio of Ar to 9: 1 is generated.

The raw material gas is introduced into the gas introducing electrode portion 31 through the raw material gas introducing pipe 8, diffused by the gas diffusion member 32 of the gas introducing electrode portion 31, and 40 μm in the stainless sintered filter 33. As a result, fine gas particles are formed through the openings of (1) and are uniformly introduced into the vacuum container 1.

Here, when the source gas is introduced at 10 Pa, a high frequency power of 200 W is applied to the discharge electrodes 31, 3 and plasma is formed between the discharge electrodes 31, 3 and the stainless sintered filter 33.

In this plasma, the raw material gas is introduced finely and uniformly from the stainless sintered filter 33, and
Since the potential distribution of the stainless sintered filter 33 is uniform,
It is formed uniformly over a range of 130 mm which is the diameter of the stainless sintered filter 33.

Therefore, Ar and methanol (CH ₃ O
The source gas consisting of H) is uniformly decomposed and activated by the plasma, and carbon (C) contained in the source gas is uniformly reacted on the silicon wafer 35a to form a diamond-like carbon film. It

When 10 minutes have passed from the application of the high frequency power, the application of the high frequency power is stopped and the introduction of the raw material gas is stopped to complete the film formation of diamond-like carbon.

After the film formation is completed, interference fringes are observed on the silicon wafer 35a as described above. The interference fringes of this embodiment are
Both before and after film formation have concentric patterns.
Therefore, a diamond-like carbon film having high internal stress uniformity can be formed. The film thickness at this time is 1.5 μm, which is thicker than the conventional 0.2 μm,
Along with this, the film forming efficiency is improved more than ever before.

Next, a glass wafer 35b having a thickness of 1 mm and a diameter of 5 inches is used in the apparatus of this embodiment, and as described above, diamond-like carbon is deposited on the glass wafer 35b.

After the film formation is completed, as in the above, 2 within the 5 inch diameter is used.
The visible light transmittance at 0 points is measured and converted into a film thickness, and the distribution of this film thickness is calculated using the above-mentioned formula (1).

As a result of calculation, the film thickness distribution is ± 1% within a diameter of 5 inches. Therefore, it is possible to form a diamond-like carbon film having extremely excellent uniformity of film thickness distribution.

As described above, according to the present embodiment, one of the discharge electrodes, which is one of the discharge electrodes, is the gas introducing electrode portion 31.
Since the stainless sintered filter 33 made of a metal porous body is provided in the above, by uniformly introducing the source gas into the plasma atmosphere through the discharge electrode of the porous body,
Even with a large diameter wafer of 5 inches, the uniformity of the film thickness distribution can be significantly improved.

For example, in this embodiment, ± 1 within a diameter of 5 inches
We obtained the film thickness distribution within%, but the value of ± 1% is
Compared to the conventional film thickness distribution of about ± 5% within a diameter of less than 3 inches, the uniformity is far superior.

Further, according to the present embodiment, it is possible to realize an apparatus which does not exist in the past, which forms a thin film with a film thickness distribution of ± 3% or less in a range of 3 inch diameter or more.

Further, along with this, for example, the film thickness distribution required in the X-ray transparent film for X-ray masks, which is a strict value of ± 3% or less or ± 1%, can be satisfied. It can be widely used as an X-ray transparent support film for a line mask.

Further, according to the present embodiment, various substances can be formed on an arbitrary substrate by changing the source gas, the substrate, and the film forming conditions. Therefore, it can be used as a semiconductor device or a mask material, for example. As a result, various thin films with high functionality and high added value can be applied.

Further, according to the present embodiment, the film forming environment is adjusted by supplying the uniform and fine raw material gas through the stainless sintered filter 33 over the entire plasma atmosphere. A diamond-like carbon film can be formed with uniform stress. Moreover, the quality of the film can be improved by adjusting the film forming environment. Further, by changing the source gas, the substrate, and the film forming conditions in the same manner as described above, various substances can be formed on any substrate with uniform internal stress, so that various thin films can be made highly functional. You can

Further, according to the present embodiment, it is possible to form a diamond-like carbon film having a thickness of 1.3 μm thicker than the conventional one within a film forming time of 10 minutes.

That is, conventionally, the raw material gas corresponding to the volume of 1.3 μm thickness × 5 inch diameter became fine powder and adhered to the inside of the vacuum container 1, whereas this embodiment corresponds to the conventional fine powder. Since the raw material gas to be formed is deposited as diamond-like carbon, the maintainability can be improved without contaminating the vacuum container.

Further, according to the present embodiment, since the generation of fine powder is prevented, the fine powder may drop on the substrate during the installation of the substrate or the deposition of the thin film and deteriorate the film quality of the dropped portion. The reliability can be improved because there is no.

Further, according to the present embodiment, the gas diffusion member 32 is interposed between the gas introduction pipe 8 and the stainless sintered filter 33 to supply the source gas almost uniformly to the entire surface of the stainless sintered filter 33. As a result, even if the flow rate of the source gas is changed, unevenness in film thickness is less likely to occur between the central portion and the end portion of the wafer, and thus reliability can be further improved.

Further, according to the present embodiment, since the stainless sintered filter 33 having a large number of fine holes of 40 μm is used, the mechanical strength is enhanced, the processing is facilitated, the raw material gas and the high frequency power are used. It is possible to realize uniform supply in the same time.

Further, according to the present embodiment, the above effects can be realized with a simple structure in which one of the discharge electrodes is provided with a gas introduction port made of a porous metal body.
Moreover, since the structure is simple, the maintainability of the device can be further improved.

In the above embodiment, the case where the substrate is placed on the lower discharge electrode and the gas is introduced from the upper discharge electrode has been described, but the present invention is not limited to this, and the substrate is placed on the upper discharge electrode. The present invention can be implemented in the same manner and the same effect can be obtained even if the gas is introduced from the lower discharge electrode by mounting.

Further, the present invention can be implemented in the same manner and the same effect can be obtained even with a structure in which the substrate is arranged outside the two electrodes with respect to the pair of discharge electrodes arranged to face each other. You can In this case, it becomes possible to form the thin film by introducing the raw material gas from both discharge electrodes.

Further, in the above embodiment, the case where the stainless sintered filter 33 having a thickness of 2 mm is used has been described. With the configuration used, the same effects can be obtained by implementing the present invention in the same manner.

Besides, the present invention can be variously modified and implemented without departing from the scope of the invention.

[0072]

As described above, according to the present invention, at least one of the discharge electrodes is provided with a gas inlet port made of a porous metal material, so that the raw material gas is supplied to the porous material. By uniformly introducing into the plasma atmosphere through the metal electrode, it is possible to provide a plasma CVD apparatus capable of significantly improving the uniformity of film thickness distribution.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing the configuration of a plasma CVD apparatus according to an embodiment of the present invention.

FIG. 2 is a sectional view showing the configuration of a gas inlet and one discharge electrode in the same embodiment.

FIG. 3 is a schematic diagram showing the configuration of a conventional plasma CVD apparatus.

FIG. 4 is a schematic diagram showing the configuration of a conventional plasma CVD apparatus.

FIG. 5 is a block diagram showing a conventional plasma CVD apparatus partially broken away.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Vacuum container, 3 ... Lower discharge electrode, 4 ... High frequency power supply, 6
... Methanol, 7 ... Raw material gas container, 8 ... Raw material gas introduction pipe, 9 ... Ar gas introduction pipe, 31 ... Gas introduction electrode part, 3
2 ... Gas diffusion member, 33 ... Stainless sintered filter, 3
4 ... Cover.

Claims (1)

[Claims] 1. A pair of discharge electrodes are arranged to face each other in a vacuum container, a raw material gas is introduced into the vacuum container, and electric power is supplied to at least one of the discharge electrodes so that plasma is generated between the discharge electrodes. In a plasma CVD apparatus for forming a thin film on a predetermined substrate in the vacuum container by activating the raw material gas to generate a metal porous metal on at least one of the discharge electrodes. A plasma CVD apparatus having a gas introduction port formed of a body.