JPS6362866A - Method and device for forming thin carbon film - Google Patents

Abstract

PURPOSE:To form a good-quality thin carbon film on a base plate by shielding ultraviolet rays of plasma from the base plate in case of causing plasma between a carbon target and a counter electrode in a vacuum chamber having the gaseous atmosphere exhausted at low pressure. CONSTITUTION:Plural pieces of circular base plates 10 made of quartz glass are set on an annular holding part 9 of the base plates in a vacuum chamber 1 and heated. Simultaneously the inside of the vacuum chamber 1 is exhausted and held at the prescribed pressure by regulating a valve 3 and introducing gaseous H2. Then electrical discharge is performed by impressing DC voltage between a circular carbon target 5 and a similarly shaped counter electrode 8 to sputter the carbon target 5 with hydrogen plasma. The ratio of the diameter of the counter electrode 8 to the diameter of the target 5 is regulated to about >=0.75 and such a state that hydrogen plasma and ultraviolet rays are shielded from the base plate 10 is formed. Thereby an amorphous thin carbon film which is homogeneous and transparent and has a broad optical energy gap is formed on the base plate 10.

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to a method for forming diamond and amorphous diamond carbon thin films on a substrate by chemical sputtering, and an improvement in the apparatus thereof, and in particular to an improvement in the method and apparatus for forming diamond and amorphous diamond carbon thin films on substrates by chemical sputtering. A method and apparatus for forming a high quality carbon thin film by shielding the carbon thin film from a substrate on which it is to be formed.

B0 Summary of the Invention The present invention firstly involves applying a DC voltage between a carbon target and a counter electrode in a vacuum chamber with a low-pressure excitation gas atmosphere to generate plasma, and depositing carbon onto a substrate placed in the vacuum chamber. In the sputtering method for forming thin films, by shielding the ultraviolet rays of the plasma from the substrate, a wide range of optical gears can be achieved. In addition, it is possible to obtain an amorphous carbon film that has a sharp band tail calculated from an ultraviolet-visible absorption spectrum and is suitable for use as a semiconductor material. In the above-mentioned sputtering apparatus, a carbon target and a counter electrode are provided, a DC voltage is applied between them to generate plasma, and a substrate on which a carbon thin film is to be formed is placed within a vacuum. The method for forming an amorphous carbon film as described above can be achieved by configuring the sputtering apparatus so that the holding part of the substrate is provided with a side pressure opposite to the carbon target of the counter electrode, and the ultraviolet rays generated from the plasma are shielded from the substrate by the counter electrode. A sputtering apparatus with a simple structure is provided.

C0 Prior Art Conventionally, methods for forming diamond and amorphous diamond-like carbon films include glow discharge decomposition of hydrocarbons (hydrogen dilution), microwave discharge decomposition, and chemical sputtering of carbon using hydrogen.

D1 Problems to be Solved by the Invention In the conventional methods described above, ultraviolet rays are generated because plasma is generated. It is believed that this ultraviolet light acts to promote the decomposition of hydrocarbon species that have been partially decomposed by the discharge. Therefore, a substrate that is well exposed to ultraviolet rays has a brownish color, whereas a substrate that is less exposed to ultraviolet rays is pale yellow or colorless and transparent. However, no change was observed in the growth rate of the carbon film depending on whether or not it was exposed to ultraviolet rays. Under these circumstances, if a film is formed under one condition, a carbon film with different characteristics will be formed depending on the installation position of the substrate in the sputtering apparatus. Therefore, it is conceivable to rotate the substrate holder in the sputtering device once to eliminate differences in the characteristics of the carbon film due to differences in the installation position of the substrate. There is a problem that when the carbon film is formed at a position where it does not contact the carbon film, the carbon film has multiple layers having different characteristics.

Therefore, in order to eliminate the difference in film quality due to changes in the position of the substrate, it is necessary to prevent the substrate from being exposed to ultraviolet rays as much as possible.The present invention solves the above-mentioned conventional problem by shielding the substrate from ultraviolet rays. This is an attempt to solve point l.

Friendly means for solving E0 problems In the present invention, in order to solve the above conventional problems,
Plasma is generated by applying a DC voltage between the carbon target and the counter electrode in a vacuum chamber with a low-pressure excited gas atmosphere.
In the sputtering method in which a carbon film g is formed on a substrate placed in a vacuum chamber, the ultraviolet rays of the plasma are shielded from the substrate and the sputtering is carried out in the t state.

To carry out the above method, a carbon target and a counter electrode are provided in a vacuum chamber with a low-pressure excitation gas atmosphere, and a DC voltage is applied between them to generate plasma.
At the same time, in the KL, 7t sputtering apparatus, a substrate on which a carbon thin film is to be formed is placed in the vacuum chamber, and a holding portion for the substrate is provided on the side opposite to the carbon target of the counter electrode,
The ultraviolet rays generated from the plasma were shielded from the substrate by the counter electrode.

20 Effects In the present invention, a vacuum chamber is made into a low-pressure excitation gas atmosphere, and a DC voltage is applied between a carbon target provided in the vacuum chamber and a counter electrode to generate plasma,
The carbon target is decomposed to form a carbon thin film on the substrate placed behind the counter electrode. During this time, ultraviolet rays are emitted from the plasma, but these ultraviolet rays are blocked by the opposing electrode and are not irradiated onto the substrate. Therefore, it is possible to form an amorphous carbon thin film that is homogeneous, transparent, and has a wide optical energy gap.

G. Example DESCRIPTION OF THE DRAWINGS The invention will now be described in detail with reference to the figures.

FIG. 1 shows a sputtering apparatus used in this example. In the figure, 1 is a vacuum chamber, and this vacuum chamber 1 is equipped with an exhaust pulp 2 and a pulp 3 into which hydrogen gas, which is an atmospheric gas, is introduced. A target holder electrode 4 with a magnetron is provided at the center of the vacuum chamber 1, and a circular target 5 is held on top of the target holder electrode 4. 6 is an insulating member, and 7 is a shielding member. A circular counter electrode 8 is placed facing and concentrically with the target 5, and the pressure between them is such that a DC voltage is applied. The substrate holding part 9 is located on the side opposite to the target 5 (backward) of the counter electrode 8,
It has an annular shape concentric with the counter electrode 8. The substrate 10 on which a carbon film is to be formed is mounted on the substrate holder 9.

A specific example in which a carbon thin film was formed on the substrate IO using the sputtering apparatus rR1 will be described below.

In the sputtering apparatus used in this example, the diameter of the vacuum chamber 1 is 300 m, the outer diameter of the substrate holding part 9 is 250 m,
The dimension 11 between the target 5 and the counter electrode 8 is 30 vaas.
The dimension 12 between the counter electrode 8 and the substrate 10 is 1508. Then, eight quartz glass substrates 10 were set on the substrate holder 9, and first 2.6
After evacuating the vacuum chamber 1 to 7X11j'Pa (2X16'Torr), the gas introduction pulp 31 was adjusted to introduce hydrogen gas at a flow rate of 5cc/mtn (controlled by the mass pro controller), and the exhaust pulp 2 was adjusted to 26 Maintain .7Pa (0.2Torr) K, and
A DC voltage was applied between the target 5 and the counter electrode 8, and 40
Perform one discharge at 0V-1, 2A. Carbon target 5 (
Φ75) Sputter with hydrogen plasma. At this time, the substrate holding part 9 is maintained at 120'C. And under the above conditions,
Opposing! The diameter of the FF 18 was changed and the ratio of the diameter of the counter electrode 8 to the diameter of the target 5 was set to 7 types from 0 to 2, and sputtering was performed for 5 hours each. As a result, the thickness of the nine carbon film formed on the quartz glass substrate 10 was as follows. , approximately 500 regardless of the change in the diameter of the counter electrode 8.
It's nm. Then, the optical energy gap was calculated from the ultraviolet-visible absorption spectra of the respective produced carbon films, and the results are shown in FIG. In the figure, the ○ marks are actual measurement points, and the solid lines connect the measurement points. As is clear from this diagram, the counter electrode 8 diameter/target 5 diameter (Φ75
) is small, there will be a 30% variation between the center and peripheral parts of the substrate holding part 9, but if it is 0.7 or more, this variation will be within sts, and Eo will take a large value. Danaru.

In addition, it can be changed from hY20■ to 50kaku, and 1zkl
No change was observed in the above results even when the temperature was varied from OOw to 170.

As described above, the effects of the H0 invention are as follows! In the invention described in item (1), plasma I is generated by applying a DC voltage between a carbon target and a counter electrode in a vacuum chamber with a low-pressure excitation gas atmosphere, and a plasma I is generated on a substrate placed under pressure in the vacuum chamber. In the sputtering method for forming a carbon thin film, it is determined that the ultraviolet rays of the plasma are shielded from the substrate, so that the formed carbon film is not affected by the shadow 9 of the ultraviolet rays, and is therefore transparent and has a wide optical gap. , the 72 band tail calculated from the UV-visible absorption spectrum is steep, and an amorphous carbon film suitable for use as a semiconductor material can be obtained.

Seriously, the scope of the patent claims! The invention described in item (3) has the advantage that it is possible to provide a sputtering apparatus with a simple structure capable of producing an amorphous carbon film as described above.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a schematic cross-sectional view of a sputtering apparatus, I! Figure 2 is a chart showing the results of calculating the optical energy gap (Eo) from the ultraviolet-visible absorption spectrum of the carbon film. DESCRIPTION OF SYMBOLS 1... Vacuum chamber, 5... Target, 8... Counter electrode, 9... Substrate holding part, 10... Substrate. Figure 1: Return to prefecture, Hirobukuro Kashi section, Figure 2

Claims (4)

[Claims] (1) In the sputtering method described above, a plasma is generated by applying a DC voltage between a carbon target and a counter electrode in a vacuum chamber with a low-pressure excited gas atmosphere to form a carbon thin film on a substrate placed in the vacuum chamber. 1. A method for forming a carbon thin film, the method being carried out in a state where ultraviolet rays of plasma are shielded from the substrate. (2) The method for forming a carbon thin film according to claim (1), characterized in that hydrogen is used as the low-pressure excitation gas. (3) A carbon target and a counter electrode are provided in a vacuum chamber with a low-pressure excitation gas atmosphere, and a DC voltage is applied between them to generate plasma, and a substrate on which a carbon thin film is to be formed is placed in the vacuum chamber. A sputtering apparatus for forming a carbon thin film, characterized in that the holding portion of the substrate is provided on the side opposite to the carbon target of the counter electrode, and ultraviolet rays generated from plasma are shielded from the substrate by the counter electrode. (4) The carbon thin film forming apparatus according to claim (3), wherein the ratio of the diameter of the counter electrode to the diameter of the carbon target is 0.7 or more.