JPH02255593A - Graphite susceptor for plasma cvd - Google Patents

Abstract

PURPOSE:To lower the content of foreign matter in a formed film and to uniformize the film thickness by making the surface roughness of a wafer contact surface smaller than that of the other surface and covering the entire surface with vitreous carbon. CONSTITUTION:The susceptor main body 1 is machined to 2-5mu surface roughness Ra and 15-30mu Rmax. The wafer contact surface 2 of the main body 1 alone is lapped to <=1mu Ra and <=10mu Rmax. A soln. of a pitchy carbon precursor obtained by thermally decomposing an org. polymer such as PVC in an inert atmosphere is applied on the main body 1 and calcined in a vacuum, etc., to coat the surface of the main body 1 with vitreous carbon in 2-5mu film thickness. Consequently, a graphite susceptor for CVD with the roughness of the surface 2 made smaller than that of the other surface 3 is obtained. When the susceptor is used, the electrical resistivity and uniformity of the formed film are improved, and the yield of the film formation is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a graphite susceptor used in plasma CVD.

(Prior art) Conventionally, susceptors for plasma CVD have been made by simply machining graphite, or by performing purification treatment after machining to achieve surface processing accuracy of ~ (Ra2~5μm, 'Bxax 15
~3Qpy@) and those whose surfaces are coated with glassy carbon to give a mirror finish are known (for example, JP-A-64-47019).

(Problem to be solved by the invention) However, in such a graphite susceptor,
When a silicon oxide film or silicon nitride film is formed on Ueno by plasma CVD, the dust generated from the susceptor is incorporated into the film, making it possible to stably form an excellent film that does not contain foreign matter. ＜＜However, in normal processing of the surface of the susceptor, the heat applied to the susceptor by external heating is not uniformly transmitted to the wafer 1 due to the scattering of the surface, making it difficult to form a uniform film within the wafer or between wafers. There were drawbacks such as.

However, when forming a silicon oxide film or silicon nitride film on a glassy carbon-coated susceptor, the silicon oxide film or silicon nitride film deposited on the susceptor tends to peel off because the susceptor surface is mirror-finished. It had drawbacks such as being incorporated into the membrane.

The present invention aims to solve the above-mentioned drawbacks.

(Means for Solving the Problems) That is, the present invention is characterized in that the surface roughness of the wafer contact surface is made smaller than that of other surfaces, and the entire surface is coated with glassy carbon. This is a graphite susceptor for plasma CVD.

Hereinafter, the present invention will be described in more detail. In a preferred embodiment of the present invention, the surface roughness of the wafer contact surface is Ra 1am or less, Rmax 10μm or less, preferably Ra O,5
μm or less, Rxnax 7 μm or less, and the surface roughness of the other surface is Ra 2-5 Jim, Rxnax 1
5 to 40 μm, and the entire surface of the susceptor has a film thickness of 2 to 5 μm.
This is a graphite susceptor for plasma CVD coated with μm glassy carbon.

By setting the surface roughness of the wafer contact surface as described above, the heat applied to the susceptor from the external heater is uniformly transmitted to the wafer, thereby improving the uniformity of the formed film. In addition, by adjusting the surface roughness of the other side that does not contact the wafer as described above and coating the entire surface of the susceptor with glassy carbon with a thickness of 2 to 5 μm, the susceptor surface does not become a mirror surface, so that deposits can be deposited on the susceptor surface. No peeling of the silicon oxide film or silicon nitride film occurs. In addition, since the surface is coated with glassy carbon, graphite dust is not generated, making it possible to stably produce an excellent film that does not contain foreign substances. If glassy carbon is coated with a thickness exceeding 5 μm, the surface of the susceptor becomes mirror-like, making it difficult to peel off, and it is not preferable because the peeled off material is likely to be incorporated into the silicon oxide film or silicon nitride film formed on the wafer. .

Examples of specific manufacturing methods of the present invention will be shown below.

First, a susceptor for plasma CVD as illustrated in FIG. 1 is machined according to a conventional method to a surface accuracy of .about. The shape of the susceptor is not limited to this, and may be, for example, a pancake shape or a leaflet shape. At this time, the surface roughness is Ra 2 to 5 μm, Rm
Since ax 15-3 Q p@, only the wafer contacting surface of the susceptor base material is then surface-layered using an abrasive material such as sandpaper or an industrial bat. or,
Sand the entire surface of the susceptor using an abrasive material such as an industrial bat to achieve a surface roughness Ra of 1 μm or less, Rma
After polishing to x 1 Q μm or less, preferably Ra Q, 5 μm or less, and Rmax 7 fim or less, only the wafer contact surface is masked with tape, paper, etc., and other surfaces are sandblasted, etc. to Ra of 2 μm or more, Rmax
The thickness may be 15 μm or more.

The surface of the susceptor substrate obtained as described above is coated with glassy carbon having a thickness of 2 to 5 μm using the method described in Japanese Patent Publication No. 52-39684. The coating method will be briefly explained below. An organic polymer such as polyvinyl chloride, which is the raw material for glassy carbon, is coated in an inert atmosphere.

Pyrolysis is performed at 350 to 450°C to obtain a pitch-like carbon precursor. This carbon precursor is dissolved in an organic solvent such as trichlene, applied to the surface of the susceptor substrate, and then fired at 1000° C. or higher in vacuum or in an inert atmosphere.

This coating-firing step is repeated to coat the surface of the susceptor substrate with glassy carbon. For applications requiring high purity, a high purity susceptor can be obtained by introducing a halodef gas such as chlorine or fluorine at a temperature of 1600° C. or higher, if necessary.

(Example) Hereinafter, the present invention will be explained in more detail by giving Examples and Comparative Examples.

Example 1 Plasma CVD susceptor (800x1
50x4) was machined (surface accuracy Ra3.2μ@,
Rmax 22μWL) The contact surface of the wafer was covered with an industrial bat (Sumitomo 3M Scotch Silite 7448).
(Ra015μm 'Rmax 6
．． 5 Am). On the surface of this susceptor, polyvinyl chloride was thermally decomposed at 390°C in a nitrogen atmosphere to obtain a tar-like carbon precursor. This carbon precursor was dissolved in trichlene at a concentration of 15% by weight, and the solution was used as a susceptor substrate. and baked at 1200°C in a vacuum atmosphere. This coating-baking process was repeated four times, resulting in a film thickness of 6.5 μm.
Glassy carbon was coated on the surface of the base susceptor.

As a result, the surface roughness after coating with glassy carbon was as follows: Ra[] on the wafer contact surface, 3μ7FL, Rmax 6.0μr
The other surface other than rL1 is Ra 3.0 μm, R
A graphite susceptor for Zolaz WCVD with a maximum diameter of 21 μm was obtained.

Comparative Example 1 Example 1 except that the surface was not coated with glassy carbon.
A graphite susceptor for plasma CVD was manufactured in the same manner.

Comparative Example 2 A graphite susceptor for plasma CVD was manufactured in the same manner as in Example 1, except that the Ueno contact surface of the susceptor base material was not mirror-finished and the glassy carbon coating was not applied.

Comparative Example 6 The entire surface of the susceptor base material was coated with Scotch Prite 74 without changing the surface roughness of the wafer contact surface and other surfaces.
After mirror finishing with 48, glassy carbon film thickness 3.5μ
A graphite susceptor for plasma CVD was obtained in the same manner as in Example 1 except that it was coated with m.

In order to evaluate the above four examples of susceptors, using a diffusion furnace type plasma CVD system, five 4-inch S1 wafers were set in a Pelger, and heated three times by external heating.
Heated to 00℃ and applied high frequency 13.56 MH between the susceptors.
Multiply by z81)1. and NH5 were introduced into a Pelger as raw material gases, high-frequency plasma was generated at a vacuum degree of 1 torr, and a silicon nitride film of 1.2 μm was formed on the S1 vines. The variation in film thickness and the amount of foreign matter were examined using a microscope.

The results are shown in Table 1.

(Effects of the Invention) When the graphite susceptor for plasma CVD of the present invention is used, the electrical resistivity and uniformity of the produced film are improved.

This improves the yield of K film formation and reduces production costs.

[Brief explanation of drawings]

FIG. 1 is a schematic front view showing an example of a graphite susceptor for plasma CVD according to the present invention. 1... Susceptor main body, 2... Wafer contact surface, 3.
,. Other than that, 4...bin patent applicant Denki Kagaku Kogyo Co., Ltd.

Claims (1)

[Claims] 1. A graphite susceptor for plasma CVD, characterized in that the surface roughness of the wafer contact surface is smaller than that of other surfaces, and the entire surface is coated with glassy carbon.