JPH04366901A - Element having carbon film - Google Patents

Abstract

PURPOSE:To substantially prevent the peeling and cracking of the multi-layered films of the element constituted by forming the multi-layered films having at least either of carbon films of hydrogenated amorphous carbon films and diamond-like carbon films on a base body. CONSTITUTION:The multi-layered films laminated with the hydrogenated amorphous carbon films (a-C:H) and dielectric films (SiO2, ZrO2, KgF2) are formed on the base body (PMMA). The one dielectric film (ZrO2, MgF2) has the tensile stress within a 1X10<3> to 1(X)10<10>dyn/cm<2> range. The hydrogenated amorphous carbon films and the other dielectric film (SiO2) have the compressive stress within a 1X10<8> to 1X10<10>dyn/cm<2> range. The average stress of the multi-layered films is set relatively low in this way.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an element having a carbon film, for example, an element in which a multilayer film including a hydrogenated amorphous carbon film, a diamond-like carbon film, etc. is formed on a plastic substrate.

0002

[Prior Art] Elements are known in which a relatively hard carbon film is coated on a soft base such as plastic to protect the base, and in this element, the adhesion of the carbon film to the base is improved. Therefore, it is also known to coat a substrate with a soft carbon film and a carbon film in order from the substrate side to form a multilayer film. Furthermore, optical elements using carbon films as constituent materials of antireflection films (multilayer films) are also known.

0003

[Problems to be Solved by the Invention] In these conventional elements, the internal stress of the multilayer film is large, and as a result, defects such as cracks in the multilayer film or peeling of the multilayer film from the substrate are likely to occur.

0004

Means for Solving the Problems The present invention provides an element in which a multilayer film having at least one of a hydrogenated amorphous carbon film and a diamond-like carbon film is formed on a substrate. 108dyn/cm2~1x
The above problem is solved by having a compressive stress within the range of 1010 dyn/cm2.

[0005] The present invention also provides an element in which a multilayer film in which at least one of a hydrogenated amorphous carbon film and a diamond-like carbon film and a dielectric film are laminated is formed on a substrate, the average of the multilayer film being In order to substantially reduce stress, the carbon film 1×108 dyn/cm2 to 1×10
The above problem is solved by having a compressive stress within the range of 10 dyn/cm2.

In one embodiment of the present invention, the multilayer film includes, in order from the substrate side, a relatively soft hydrogenated amorphous carbon film and a hard second hydrogenated amorphous carbon film.

Further, in one embodiment of the present invention, the multilayer film includes, in order from the substrate side, a relatively soft first diamond-like carbon film and a hard second diamond-like carbon film.

[0008] In one aspect of the present invention, the multilayer film includes at least one layer each of a hydrogenated amorphous carbon film and a diamond-like carbon film.

[0009] In one embodiment of the present invention, the multilayer film forms an interference film.

The present invention also includes the base body made of plastic, the base body made of metal, and the base body made of glass.

[0011] Furthermore, in one embodiment of the present invention, the film closest to the substrate of the multilayer film is made of metal.

[0012] Furthermore, in one embodiment of the present invention, at least one of the dielectric films has a density of 1×108 dyn/cm2 to 1×1 dyn/cm2.
with a tensile stress in the range of 0.10 dyn/cm2.

[0013] In one aspect of the present invention, the multilayer film includes alternating layers of the carbon film and the dielectric film.

The present invention also includes the base body made of plastic, the base body made of metal, and the base body made of glass. Further, the element of the present invention includes optical elements such as lenses, mirrors, prisms, and gratings.

Further, in a preferred embodiment of the present invention, the internal stress of the multilayer film is set to approximately 1×10 9 dyn/cm 2 or less in absolute value.

[0016]

[Example] In the example shown below, by providing a hydrogenated amorphous carbon film or a diamond-like carbon film on a certain surface of the plastic, the drawbacks of conventional plastic materials are solved and the performance is equivalent to or better than that of glass. A plastic optical element is provided.

For example, at least one layer of an optical thin film such as an antireflection film, a reflective film, an interference filter, a polarizing film, etc. provided on the surface of a plastic is made of a hydrogenated amorphous carbon film or a diamond-like carbon film.

Methods for forming a hydrogenated amorphous carbon film or a diamond-like carbon film on the surface of a plastic optical element include plasma CVD method and ECR-PCV method.
There are D method, ion beam evaporation method, and ion beam sputtering method.

FIG. 2 shows ECR-PC for forming a hydrogenated amorphous carbon film, a diamond-like carbon film, and a dielectric film.
A schematic diagram of a VD device is shown. In the figure, numeral 1 is a plastic base for lenses, prisms, fibers, optical waveguides, gratings, etc. Polyacrylic acid ester resin,
It is made of transparent plastic materials such as polycarbonate resin, vinyl chloride resin, polystyrene resin, CR-39, etc. 2 is a plasma generation chamber, 3 is a reaction chamber, 4 is a gas supply system,
5 is a microwave oscillator such as a microwave waveguide, 6 is an exhaust system, 7 is an external magnetic field generating coil, 8 is an electron gun, 9 is a film thickness monitoring device for controlling the film thickness, and 10 is a vapor deposition material.

[0020] When forming a hydrogenated amorphous carbon film or a diamond-like carbon film by various film forming methods, raw material gases include carbon-containing hydrocarbons such as methane, ethane, propane, ethylene, benzene, and acetylene;
Examples include halogenated hydrocarbons such as carbon tetrafluoride, methylene chloride, carbon tetrachloride, chloroform, and trichloroethane, and gases such as carbon dioxide and carbon monoxide. Further, a gas obtained by mixing these gases with an inert gas such as N2, H2, O2, H2O, etc. may be used.

With the apparatus shown in FIG. 2, a hydrogenated amorphous carbon film with a Vickers hardness of 500 kg/mm2 or more can be formed, and by changing the film forming conditions, hydrogen content in the film can be reduced as shown in FIG. rate (concentration) of 5 to 50a
It can be changed within a range of tom%. By adjusting this hydrogen content, the hardness of the hydrogenated amorphous carbon film can be increased to 500 kg/mm2 to 20 in terms of Vickers hardness.
It can be controlled within a range of 00 kg/mm2. or,
By adjusting this hydrogen content, the internal stress of the hydrogenated amorphous carbon film can be reduced to 108 dyn/c in compressive stress.
It is possible to control within the range of m2 to 1×10 10 dyn/cm 2 . In addition, the hydrogen content is 5 to 50 atom%
The refractive index of hydrogenated amorphous carbon film in the range of 1
．． 48 to 1.60, and as the hydrogen concentration increases, the refractive index of the film decreases. Furthermore, this hydrogenated amorphous carbon film has a smooth surface roughness of 100 Å or less in RMS, and can have a very smooth friction coefficient of 0.2.

On the other hand, the diamond-like carbon film obtained with the apparatus shown in FIG. 2 is not a complete diamond crystal but an amorphous film containing diamond microcrystals, and the refractive index of this carbon film is 1.8 to 2.4. be. In addition, the mechanical properties of this carbon film have a hardness of 3000 to 600 on the Vickers scale.
0kg/mm2, stress 109~1011dyn/cm
It has a compressive stress of 2.

This hydrogenated amorphous carbon film (hereinafter referred to as "a-C:H film") and the diamond-like carbon film (
Hereinafter, it will be referred to as "DLC film". ) is formed on the substrate of a plastic optical element, firstly, both films have high gas and moisture impermeability, so the problem of swelling due to water absorption of plastic can be solved. Second, because the film has high hardness, it has a hardness that is equal to or higher than the surface hardness of glass, and it does not get scratched even when handled like a normal glass optical element. Thirdly, when forming optical thin films such as antireflection films, reflective films, and filters on plastic substrates, the substrate is extremely soft, and cracks may occur in the dielectric multilayer film due to swelling due to water absorption of the substrate. , causing film peeling.

Generally speaking, most of the stress in dielectric thin films is tensile stress, and the magnitude of this stress is 108
It is in the range of ~1010 dyn/cm2.

The average stress of the multilayer film is

[0026]

It is expressed as [Example 1]. Here, Si represents the internal stress of the i-th layer, and ti represents the geometric thickness of the i-th layer. From this equation, it can be seen that in order to reduce the average stress of the multilayer film, the multilayer film should be formed by appropriately combining materials having tensile stress and materials having compressive stress. Therefore, in this example,
a with a compressive stress of 108 to 1010 dyn/cm2
-C: By combining H film, DLC film, and dielectric film,
A multilayer film with low internal stress was realized. As a result, a multilayer film that does not or is unlikely to cause peeling or cracking can be obtained. The refractive index and stress of each of the a-C:H film and the DLC film should be adjusted in relation to other dielectric films so that the optical element achieves the desired optical performance and the stress of the entire film is small. It is determined by the relationship and the relationship between the two.

[0027] The substrate is not limited to plastic, and may be made of optical glass, metal, or the like.

[0028]

[Example] After installing a polyacrylic acid ester substrate in the apparatus shown in Fig. 2, 1 x 10-6 to
The atmosphere was evacuated to rr, and an antireflection film was formed on the PMMA substrate with the configuration shown in Table 1. Conventional dielectrics were deposited by vacuum deposition using an electron gun. FIG. 6 shows a schematic diagram of the element of this example. The hydrogenated amorphous carbon film was supplied with CH425sccm and H225sccm by the gas supply system.
The pressure inside the apparatus is set to 1×10 −3 torr. Here 2.
A 45 GHz microwave is introduced, an external magnetic field is set to 2000 Gauss at the microwave introduction position, and an ECR plasma is formed as a diverging magnetic field having a magnetic field distribution whose magnetic field strength gradually decreases toward the reaction chamber side. 875 Gauss, which satisfies the ECR conditions, was set almost at the boundary between the plasma generation chamber and the reaction chamber. The hydrogenated amorphous carbon film thus obtained has a surface hardness of 1000 on Vickers hardness.
kg/mm2, high transmittance and absorption in the visible region of 400
It is a film with a refractive index of 1.54 and 1% or less in nm.

The spectral characteristics of the antireflection film thus obtained are shown in FIG. Next, SiO2 film, MgF2 film, Zr
When the internal stress of the O2 film and the a-C:H film was measured by the disk method, the compressive stress of the SiO2 film and the a-C:H film was 1 x 108 and 5 x 109 dyn/cm2, respectively. MgF2 and ZrO2 each have a tensile stress of 4 x 109
, 1×109 dyn/cm2. From the above formula,
The average stress of this anti-reflection film was evaluated as 1.8×108
This results in a compressive stress of dyn/cm2, which can be reduced to a very small stress. When the abrasion resistance and weather resistance of this plastic optical element (lens) were evaluated according to the MIL standard, there were no scratches on the surface of the plastic optical element, and no peeling of the film or deformation of the optical element due to water absorption was observed. There wasn't.

[0030]

[Table 1]

(Example 2) Using the apparatus shown in FIG. 2, after forming an Ag film of 2000 Å on a plastic substrate using an electron gun, a hydrogenated amorphous carbon film of 250 Å was formed on the Ag film under the same conditions as in Example 1. did. When the internal stress of a 2000 Å Ag film was evaluated, it was 4 x 108 dyn/cm2.
The internal stress of the a-C:H film formed thereon was a compressive stress of 2×10 9 dyn/cm 2 . As a result, the average stress of the entire film is 1.3×108
It was possible to achieve a tensile stress of dyn/cm2. When this plastic mirror was evaluated for wear resistance, weather resistance, etc. in the same manner as in Example 1, results equivalent to those in Example 1 were obtained. A schematic diagram of this plastic mirror is shown in FIG.

(Example 3) An antireflection film was formed on a synthetic resin with the structure shown in Table 2. The fourth layer of diamond-like carbon film is deposited with graphite using an electron gun, and at the same time
It was formed by forming H plasma using a CR plasma source and assisting irradiation onto the substrate. At this time, 25 sccm of H2 was flowed into the ECR plasma chamber, and the pressure was increased to 1 x 10-4.
After setting the torr, 2.45 GHz microwave was introduced and the chamber outlet was set to 875 Gauss using an external magnetic field.
R plasma was formed. At this time, although not shown in this embodiment, the ion beam may be extracted and used by providing an extraction electrode at the exit of the plasma chamber. The film obtained under these conditions was a so-called diamond-like carbon film, with a refractive index of 2.0 and a hardness of 3000 kg/mm2. The spectral characteristics of the obtained antireflection film are shown in FIG.

[0033]

[Table 2]

The a-C:H film was formed under the same film forming conditions as in Example 1, except that the substrate position was moved 100 mm farther from the outlet of the cavity resonator (plasma outlet) than in Example 1. The film was formed using the following method. Here, a-C:H
When the stress of the film and the DLC film were evaluated individually, the compressive stress was 3×10 9 and 1×10 10 dyn/cm 2 , respectively. Therefore, the stress of the entire film is 3.8×108dyn/
It was possible to reduce the compressive stress to cm2. When this plastic optical element (lens) was evaluated for wear resistance and weather resistance in the same manner as in Example 1, results equivalent to those in Example 1 were obtained. A schematic diagram of this element is shown in FIG.

(Examples 4 and 5) With the configuration shown in Table 3, 2
Types of filters A and B were formed. Table 3 shows Filter A using an a-C:H film as a low refractive index material, Filter B using a DLC film as a high refractive index material, and a comparative filter. a- of each filter A, B
The C:H film and the DLC film were each formed under the same conditions as in Example 3. Further, the ZrO2 film and the MgF2 film were formed by vacuum evaporation using an electron gun. When the stress of each film was evaluated independently, the stress of ZrO2 film and MgF2 film was 1×109dy.
tensile stress of n/cm2, 4 x 109 dyn/cm2, and the a-C:H film and DLC film each have a tensile stress of 3 x 109 dyn/cm2.
The compressive stress was dyn/cm2, 1×1010 dyn/cm2. From this, the average stress of the multilayer films of filters A and B is found to be 6.9 x 108 dyn/c.
Compressive stress in m2, 6.9 x 108 dyn/cm2, 1.
The tensile stress was 5 x 109 dyn/cm2. For the filter of Comparative Example 1, film peeling occurred after film formation, but for Samples A and B, there was no film peeling or cracking, and the same abrasion resistance and weather resistance as in Example 1 were obtained. Ta.

A schematic diagram of filters A and B is shown in FIG. In the figure, H indicates a high refractive index film, and L indicates a low refractive index film.

[0037]

[Table 3] As already mentioned, by changing the hydrogen content (concentration) of the hydrogenated amorphous carbon film, the internal stress of the film can be reduced by 1.
The compressive stress can be varied within the range of 08 dyn/cm2 to 1010 dyn/cm2. Furthermore, optically, the refractive index can be changed within the range of 1.48 to 1.60. Generally, as the hydrogen (concentration) content increases, the refractive index decreases. The surface roughness of this film is smooth with an RMS of 100 Å or less, and the coefficient of friction is 0.2, which is very smooth.

This hydrogenated amorphous carbon film (hereinafter referred to as aC:H film) has high impermeability to gases and moisture, so it not only solves the problem of swelling due to the water absorption of plastics, but also has a high hardness and smooth surface. Therefore, plastic has high abrasion resistance and does not cause problems such as scratches or peeling of the film even when handled in a manner that can cause scratches. However, a soft plastic substrate with high hardness
If a C:H film is directly formed, the adhesion to the substrate may not always be strong because a hard film has a large internal stress. Therefore, this problem can be solved by making the hydrogen content of the aC:H film have a gradient in the film thickness direction. That is, the plastic substrate side is an a-C:H film with high hydrogen content, film hardness or low hardness, and low internal stress, and the film surface side is a high-hardness a-C:H film with low hydrogen content. By doing so, the mechanical strength of the film can be improved by absorbing and relaxing distortion and deformation between the substrate and the film by the a-C:H film having a high hydrogen content. Furthermore, by changing the hydrogen content in one layer of the multilayer film, the refractive index distribution can be intentionally changed, and the optical properties can be improved as a so-called heterogeneous film. Note that the substrate is not limited to plastic, and the same applies even if it is optical glass, metal, or the like.

(Example 6) After installing a polyacrylic acid ester substrate in the apparatus shown in FIG.
The system was evacuated to x10-6 torr, and then CH410 sccm and H240 sccm were flowed through the gas supply system to bring the internal pressure to 5 x10-2 torr. 2.45G here
A microwave of Hz is introduced, and an external magnetic field is set to 1800 Gauss at the microwave introduction position, and a diverging magnetic field is made to decrease the magnetic field toward the reaction chamber side. 875 Gauss that satisfies ECR (microwave electron cyclotron resonance) conditions
is approximately the boundary between the plasma generation chamber and the reaction chamber.

[0040] The substrate temperature was set to room temperature, and a first aC:H film was formed with a film thickness of 2000 Å without applying a bias to the substrate. Then CH410sccm, pressure 5x10-
4 torr, substrate bias -500V, total film thickness 2
A second aC:H film was formed to a thickness of 500 Å.

In this case, a-C deposited directly on the substrate:
Since the H film has a high hydrogen content, the a-
It is softer than the C:H film and functions to reduce the adhesion between the less hard PMMA substrate and the more hard aC:H film and the internal stress of the film. Using a glass substrate or Si substrate,
When the stress of the film was measured under each film formation condition using the disk method, it was found that 1a-C without applying substrate bias:
The H film has a compressive stress of 7×108 dyn/cm2, and the second a-C:H film formed by applying a bias has a compressive stress of 2×10 dyn/cm2.
The compressive stress was 9 dyn/cm2. Also, the average stress is 9
．． It was 6×108 dyn/cm2. Furthermore, when the obtained plastic optical element (lens) was evaluated, it was found to have a Vickers hardness of 1500 kg/mm2, a very low water absorption rate, and excellent mechanical and chemical stability. A schematic diagram of this element is shown in FIG.

(Example 7) Using the same apparatus as in Example 6, a first α-C:H film similar to that in Example 6 was formed on a PMMA substrate. Thereafter, a diamond-like carbon film of 100 Å was formed on this α-C:H film.

The diamond-like carbon film was formed by forming hydrogen plasma using an ECR plasma source and irradiating the substrate with the hydrogen plasma in the same manner as graphite is deposited using an electron gun. At this time, 25 liters of H2 was added to the ECR plasma chamber.
After flowing sccm and setting the pressure to 1 x 10-4 torr,
A microwave of 2.45 GHz was introduced, and an ECR-plasma was formed using an external magnetic field with the plasma chamber outlet set to 875 Gauss.

The plastic optical element thus obtained (
The surface hardness of the lens is Vickers hardness, which is 200.
Performance equivalent to that of Example 6 was obtained except for 0 kg/mm2. In addition, the a-C:H film and the diamond-like carbon film of this example also have a density of 1 x 108 dyn/cm2 to 1 x 1010 dy.
Indicates compressive stress in the range n/cm2. The internal stress of the a-C:H film is 7×109 dyn/cm2 as in Example 6.
The compressive stress was The internal stress of the diamond-like carbon film was a compressive stress of 7×10 9 dyn/cm 2 . The average stress at this time was 1×10 9 dyn/cm 2 . A schematic diagram of this element is shown in FIG.

(Example 8) An antireflection film was formed on a PMMA substrate with the film configuration shown in Table 4. A PMM was installed in the apparatus shown in FIG.
After installing the A board, 1×10-6 tor is generated by the exhaust system.
The atmosphere was evacuated to r, and a film was formed with the configuration shown in Table 4. The usual dielectric material was formed by vacuum evaporation using an electron gun. a-C:H film is CH425sccm, H225sccm depending on the gas supply system
After setting the pressure inside the device to 1 x 10-3 torr,
A microwave of 2.45 GHz was introduced, an external magnetic field was set to 2000 Gauss at the microwave introduction position, and an ECR plasma was formed as a divergent magnetic field having a magnetic field distribution whose magnetic field intensity gradually decreased toward the reaction chamber side. 875 Gauss, which satisfies the ECR conditions, was placed almost at the boundary between the plasma generation chamber and the reaction chamber. At this time, film formation was started with a substrate bias of 0 V, and as the film thickness decreased, the bias was increased and finally -200 V was applied. As a result, the refractive index is 1.54~
It was possible to form a heterogeneous film with a value of 1.60. The spectral characteristics of the reflectance of the antireflection film thus obtained are shown in FIG. In addition, similar results were obtained by simultaneous evaluation with Example 6. Also, the a-C:H film of this example was also
/cm2 to 1 x 1010 kg/cm2.

FIG. 12 shows a schematic diagram of the device of this example.

[0047]

[Table 4]

The internal stress of each film in this example is as in Example 1.
Similarly, SiO2 and a-C:H films have compressive stress of 1 x 108 dyn/cm2 and 2 x 109 dyn/cm2, respectively.
, and the MgF2 and ZrO2ma films each have a thickness of 4×10
It had a tensile stress of 9 dyn/cm2 and 1 x 109 dyn/cm2. The average stress of this anti-reflection film is 8.
The tensile capacity was 1 x 108 dyn/cm2.

[0049]

As described above, according to the present invention, it is possible to reduce the average internal stress of the multilayer film, so that it is possible to provide an element having a carbon film in which the multilayer film is less likely to crack or peel. In addition, in the present invention, the average internal stress of the multilayer film is 1×109d.
This effect is enhanced by setting it to yn/cm2 or less.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between hydrogen content and Vickers hardness of a hydrogenated amorphous carbon film.

FIG. 2 is a schematic diagram of an ECR-PCVD apparatus for film formation.

FIG. 3 is a diagram showing the spectral characteristics of the reflectance of the antireflection film of the element of the first example of the present invention.

FIG. 4 is a diagram showing the spectral characteristics of the reflectance of the antireflection film of the device according to the second example of the present invention.

FIG. 5 is a schematic diagram of a device according to a first embodiment of the present invention.

FIG. 6 is a schematic diagram of a device according to a second embodiment of the present invention.

FIG. 7 is a schematic diagram of a device according to a third embodiment of the present invention.

FIG. 8 is a schematic diagram of elements of fourth and fifth embodiments of the present invention.

FIG. 9 is a diagram showing the spectral characteristics of the reflectance of the antireflection film of the element of the eighth example of the present invention.

FIG. 10 is a schematic diagram of a device according to a sixth embodiment of the present invention.

FIG. 11 is a schematic diagram of a device according to a seventh embodiment of the present invention.

FIG. 12 is a schematic diagram of a device according to an eighth embodiment of the present invention.

[Explanation of symbols]

1 Board 2 Plasma generation chamber 3 Reaction chamber 4 Gas supply room 5 Microwave waveguide 6 Exhaust system 7 External magnetic field applicator 8 Electron gun 9 Optical film thickness monitoring device 10 Vapor deposition material H High refractive index layer L Low refractive index layer DLC Diamond-like carbon film

Claims (14)

[Claims] 1. An element in which a multilayer film having at least one of a hydrogenated amorphous carbon film and a diamond-like carbon film is formed on a substrate, wherein the carbon film is
×108dyn/cm2~1×1010dyn/cm2
An element having a carbon film characterized by having a compressive stress within the range of . 2. The element having a carbon film according to claim 1, wherein the multilayer film includes a relatively soft hydrogenated amorphous carbon film and a hard second hydrogenated amorphous carbon film in order from the substrate side. 3. The internal stress of the multilayer film is 1× in absolute value.
2. An element having a carbon film according to claim 1, wherein the carbon film is set to 109 dyn/cm2 or less. 4. The element having a carbon film according to claim 1, wherein the multilayer film includes at least one layer each of a hydrogenated amorphous carbon film and a diamond-like carbon film. 5. The element having a carbon film according to claim 1, wherein the multilayer film forms an interference film. 6. The element having a carbon film according to claim 1, wherein the base body is made of plastic. 7. The element having a carbon film according to claim 1, wherein the base body is made of metal. 8. The element having a carbon film according to claim 1, wherein the substrate is made of glass. 9. The element having a carbon film according to claim 1, wherein the film closest to the substrate in the multilayer film is made of metal. 10. An element in which a multilayer film consisting of at least one of a hydrogenated amorphous carbon film and a diamond-like carbon film and a dielectric film is formed on a substrate,
In order to substantially reduce the average stress of the multilayer film, the carbon film has a thickness of 1 x 108 dyn/cm2 to 1 x 1010 d.
An element having a carbon film characterized by having a compressive stress within the range of yn/cm2. 11. The element having a carbon film according to claim 10, wherein the substrate is made of plastic. 12. The element having a carbon film according to claim 11, wherein the film closest to the substrate in the multilayer film is made of metal. 13. The dielectric film has a thickness of 1×108 dyn.
13. The element having a carbon film according to claim 12, characterized in that the element has a tensile stress within the range of /cm2 to 1 x 1010 dyn/cm2. 14. A device having a carbon film according to claim 13, wherein said multilayer film comprises alternating layers of said carbon film and said dielectric film.