JPH0684538B2 - Method and apparatus for forming carbon thin film - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A. Field of Industrial Application The present invention relates to an improved method for forming a diamond and amorphous diamond carbon thin film on a substrate by a chemical sputtering method and an apparatus therefor, and more particularly, to a plasma generated by the method. The present invention relates to a method and an apparatus for forming a good quality carbon thin film by shielding ultraviolet rays from a substrate on which a carbon thin film is to be formed.

B. Outline of the Invention The first aspect of the present invention is to apply a DC voltage between a carbon target and a counter electrode in a vacuum chamber of a low-pressure excited gas atmosphere to generate a plasma, and to generate a plasma on a substrate placed in the vacuum chamber. In the sputtering method for forming a carbon thin film, by carrying out the state where the ultraviolet rays of the plasma are shielded from the substrate, it has a wide optical gap, and the band tail calculated from the ultraviolet-visible absorption spectrum is steep, and it is used as a semiconductor material. And a carbon target and a counter electrode are provided in a vacuum chamber of a low-pressure excited gas atmosphere, and a DC voltage is applied between them to generate plasma. In the sputter device in which the substrate on which the carbon thin film is to be formed is placed in the vacuum chamber, the holders of the substrates are paired. A simple structure for carrying out the method for forming an amorphous carbon film as described above is provided on the side opposite to the carbon target of the counter electrode, and the sputtering device is configured to shield the ultraviolet rays generated from the plasma from the substrate by the counter electrode. The present invention provides a simple sputter device.

C. Conventional Technology Conventionally, glow discharge decomposition method of hydrocarbon (hydrogen dilution), microwave discharge decomposition method, chemical sputtering method of carbon with hydrogen, etc. are known as methods for forming diamond and amorphous diamond-like carbon film. There is.

D. Problems to be Solved by the Invention In any of the conventional methods described above, ultraviolet rays are generated because plasma is generated. It is considered that the ultraviolet rays act to accelerate the decomposition of hydrocarbon species that are partially decomposed by the discharge. Therefore, while a substrate that is exposed to ultraviolet rays is dark brown, a substrate that is exposed to less ultraviolet light is light yellow to colorless and transparent. However, no change is observed in the growth rate of the carbon film depending on whether or not it is exposed to ultraviolet rays. Under such circumstances, when a film is formed under one condition, a carbon film having different characteristics will be formed depending on the installation position of the substrate in the sputtering device. Therefore, it is conceivable to rotate the substrate holding part in the sputtering device to eliminate the difference in the characteristics of the carbon film due to the difference in the installation position of the substrate. There is a problem that a carbon film having a plurality of layers having different characteristics from the carbon film formed when it is not in contact with the film is formed.

Therefore, in order to eliminate the difference in film quality due to the change in the position of the substrate, it is necessary to prevent the substrate from being exposed to ultraviolet rays as much as possible. Is to solve.

E. Means for Solving Problems In the present invention, in order to solve the above conventional problems,
In a sputtering method in which a DC voltage is applied between a carbon target and a counter electrode in a vacuum chamber of a low-pressure excited gas atmosphere to generate plasma, and a carbon thin film is formed on a substrate placed in the vacuum chamber, ultraviolet rays of the plasma are used. Was carried out in a state of being shielded from the substrate.

Further, in order to carry out the above method, a carbon target and a counter electrode are provided in a vacuum chamber of a low-pressure excited gas atmosphere, a DC voltage is applied between them to generate plasma, and a carbon thin film is provided in the vacuum chamber. In the sputtering apparatus in which the substrate to be formed is placed, the holding portion of the substrate is provided on the side 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.

F. Action In the present invention, the vacuum chamber is a low-pressure excited gas atmosphere, a direct current voltage is applied between the carbon target and the counter electrode provided in this vacuum chamber to generate plasma, and the carbon target is decomposed. A carbon thin film is formed on the substrate placed behind the counter electrode. During this time, ultraviolet rays are emitted from the plasma, but the ultraviolet rays are blocked by the counter electrode and are not irradiated onto the substrate. Therefore, an amorphous carbon thin film having a uniform, transparent and wide optical energy gap can be formed.

G. Example An example of the present invention will be described with reference to the drawings.

FIG. 1 shows a sputter device used in this embodiment. In the figure, 1 is a vacuum chamber, and this vacuum chamber 1 includes an exhaust valve 2 and an inlet valve 3 for introducing hydrogen gas as an atmospheric gas.
Is equipped with. A magnetron-equipped target holder electrode 4 is provided in the center of the vacuum chamber 1, and a circular target 5 is held above the target holder electrode 4. Reference numeral 6 is an insulating member, and 7 is a shield member. The circular counter electrode 8 is the target 5
Is installed concentrically with this and a DC voltage is applied between them. Substrate holding unit 9
Is located on the side opposite (to the rear of) the target electrode 5 of the counter electrode 8 and has an annular shape concentric with the counter electrode 8. And
The substrate 10 on which the carbon film is to be formed is mounted on the substrate holder 9.

Then, a specific example in which a carbon thin film is formed on the substrate 10 by using the above sputtering device will be described below.

Sputtered apparatus used in this embodiment, the diameter of the vacuum chamber 1 300 mm, the outer diameter of the substrate holder 9 and 250 mm, Tagetsuto 5, 30 mm dimensions 1 ₁ between the counter electrode 8, the counter electrode 8, between the substrate 10 The dimensions 1 and ₂ are 150 mm. Then, eight quartz glass substrates 10 are set on the substrate holder 9,
2.67 × 10 ^-5 Pa (2 × 10 ^-7 Torr) using a diffusion pump
After exhausting the inside of the vacuum chamber 1, adjust the gas introduction valve 3 to introduce hydrogen gas at a flow rate of 5 cc / min (controlled by the mass production controller) and adjust the exhaust valve 2.
It was maintained at 26.7 Pa (0.2 Torr), and a DC voltage was applied between the target 5 and the counter electrode 8 to discharge at 400V-1.2A. Carbon target 5 (Φ75) is sputtered with hydrogen plasma. At this time, the substrate holder 9 is kept at 120 ° C.
Then, under the above conditions, the diameter of the counter electrode 8 was changed, the ratio of the counter electrode 8 diameter / the target 5 diameter was set to 7 kinds from 0 to 2, and each was sputtered for 5 hours. As a result, it was formed on the quartz glass substrate 10. The thickness of the carbon film was about 500 nm regardless of the change in the diameter of the counter electrode 8. The results of calculating the optical energy gap (E ₀ ) from the UV-visible absorption spectra of the carbon films respectively generated are shown in FIG. In the figure, the circles are the actual measurement points, and the solid line is the connection of the measurement points. As is clear from this chart, the counter electrode 8 diameter / target 5
When the ratio of the diameter (Φ75) is small, there is a variation of 30% between the central portion and the peripheral portion of the substrate holding portion 9, but when it is 0.7 or more, this variation is within 5% and E ₀ is a large value. Will be taken.

Note that 1 ₁ is changed from ₂₀ mm to 50 mm, and 1 ₂ is changed from 100 mm to 1 mm.
No change was observed in the above results even when the length was changed to 70 mm.

H. Effect of the Invention As described above, in the invention described in claim (1), the DC voltage is applied between the carbon target and the counter electrode in the vacuum chamber of the low-pressure excited gas atmosphere. In the sputtering method in which plasma is generated and a carbon thin film is formed on a substrate placed in a vacuum chamber, the ultraviolet rays of the plasma are shielded from the substrate, so that the formed carbon film is affected by the ultraviolet rays. Therefore, it has an effect that an amorphous carbon film suitable for use as a semiconductor material can be obtained because it has a transparent and wide optical gear and has a steep band tail calculated from the UV-visible absorption spectrum.

Further, in the invention described in claim (3), there is an effect that it is possible to provide a sputtering device having a simple structure for obtaining the amorphous carbon film as described above.

[Brief description of drawings]

The drawings show the embodiments of the present invention. FIG. 1 is a schematic sectional view of a sputtering device, and FIG. 2 is a result of calculating an optical energy gap (E ₀ ) from an ultraviolet-visible absorption spectrum of a carbon film. FIG. 1 ... Vacuum chamber, 5 ... Target, 8 ... Counter electrode, 9
…… Board holder, 10 …… Board.

Claims (4)

[Claims] 1. A sputtering method for forming a carbon thin film on a substrate placed in a vacuum chamber by applying a DC voltage between a carbon target and a counter electrode in the vacuum chamber of a low pressure gas atmosphere to generate a plasma. A method for forming a carbon thin film, which is performed in a state where the ultraviolet rays of the plasma are shielded from the substrate. 2. The method for forming a carbon thin film according to claim 1, wherein hydrogen is used as the low-pressure excitation gas. 3. A carbon target and a counter electrode are provided in a vacuum chamber of a low pressure gas atmosphere, a DC voltage is applied between them to generate plasma, and a carbon thin film should be formed in the vacuum chamber. A sputtering apparatus in which a substrate is arranged, wherein a 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. A carbon thin film forming apparatus according to claim 3, wherein the ratio of the diameter of said counter electrode to the diameter of the carbon target is 0.7 or more.