Coating apparatus – Gas or vapor deposition – Work support
Reexamination Certificate
2000-02-08
2001-04-03
Bueker, Richard (Department: 1763)
Coating apparatus
Gas or vapor deposition
Work support
C118S500000, C118S715000
Reexamination Certificate
active
06210486
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a CVD film forming method and apparatus for forming a film or layer by CVD on an object to be processed, such as a semiconductor wafer.
In the process of manufacturing a semiconductor device, a metal or metallic compound film is formed on a semiconductor wafer made of, for example, silicon, by CVD (Chemical Vapor Deposition), so that an integrated circuits can be formed on the wafer. For example, an Al film is formed on the main surface of the semiconductor wafer as follows. First, the semiconductor wafer is placed on a susceptor with an electrostatic chuck in a process chamber. The susceptor has a ceramic base member in which a heating member is embedded. While the semiconductor wafer is being heated by electricity supplied to the heating member, a process gas, e.g., dimethylaluminumhydride (DMAH) is introduced at a predetermined flow rate into the process chamber through a shower head provided above the susceptor. As a result, an Al film is formed on the surface of the semiconductor wafer.
To form an Al film, an electrostatic chuck having a diameter slightly smaller than that of the semiconductor wafer is used. The semiconductor wafer is held on the susceptor such that the circumferential edge of the semiconductor wafer is slightly projected from the electrostatic chuck, thereby preventing film formation on the electrostatic chuck.
However, in this case, the process gas flows to the rear surface of the projected portion of the semiconductor wafer and a film is formed thereon. If a film is formed on the rear surface of the semiconductor wafer, the film may be removed during a transfer or other processes, resulting in particles.
BRIEF SUMMARY OF THE INVENTION
An object of the present invention is to provide a CVD film forming method and apparatus, for forming a film on a main surface of an object to be process, while effectively preventing a film from being formed on a rear surface of the object.
According to a first aspect of the present invention, there is provided a CVD film forming apparatus comprising:
a process chamber;
a susceptor, provided in the process chamber, having a surface of an area at least the substantially same as that of an object to be processed, the surface being entirely covered by a first surface of the object to be processed mounted on the susceptor;
process gas supplying means for supplying a process gas to a second surface of the object to be processed mounted on the susceptor, thereby forming a film on the second surface; and
film formation preventing gas supplying means for supplying film formation preventing gas in a direction from the first surface of the object to be processed toward a peripheral edge thereof at a flow rate which can prevent the process gas from flowing to the first surface of the object to be processed.
According to a second aspect of the present invention, there is provided a CVD film forming method, wherein an object to be processed is mounted on a susceptor provided in a process chamber and a process gas is supplied to a main surface of the object to be processed, thereby forming a film on the object to be processed, the method comprising a step of supplying film formation preventing gas in a direction from a rear surface of the object to be processed toward a peripheral edge thereof, the film formation preventing gas having a flow rate which prevents the process gas from flowing to the rear surface of the object to be processed at the peripheral edge of the object to be processed.
With the above apparatus and method, when the film formation preventing gas is supplied from the rear surface of the object to be processed toward the peripheral edge thereof, the flow rate of the gas is set to a value which can prevent the process gas from flowing to the rear surface of the object to be processed at the peripheral edge of the object. Therefore, film formation on the rear surface of the object by the process gas is prevented.
It is preferable that the surface of the susceptor has an area smaller than that of the object to be processed, so that the object to be processed is mounted on the susceptor so as to have a projected portion in a peripheral portion of the object to be processed, which is projected from the susceptor; and the film formation preventing gas supplying means have a ring-shaped member constituting a passage through which the film formation preventing gas flows toward the peripheral edge of the object to be processed on a side of the first surface in the projected portion of the object to be processed. As a result of this structure, when the object to be processed is mounted on the susceptor such that the peripheral portion thereof is projected from the susceptor, a passage is formed so that the film formation preventing gas flows to the peripheral edge of the object through the rear surface of the projected portion of the object. Thus, the film formation preventing gas effectively prevents the process gas from flowing to the rear surface of the object to be processed.
It is preferable that the ring-shaped member has an inner flange portion on an inner circumferential surface thereof, the inner flange portion having a surface opposing with a predetermined gap to the first surface of the object to be processed mounted on the susceptor in the projected portion, thus defining a first part of the passage between the surface of the inner flange portion and the first surface of the object to be processed. It is also preferable that, where the first portion of the passage has a length L (m), a process gas has a diffusion constant D (m
2
/s) and the film formation preventing gas flows at a flow rate v (m/s), the length L and the flow rate v are set to satisfy a condition of Lv/D>1. Thus, the film formation preventing gas effectively prevents the process gas from flowing to the rear surface of the object to be processed.
The ring-shaped member is preferably made of non-metallic material. In this case, since non-metallic material has a lower thermal conductivity than metal, thermal reaction on the ring-shaped member is suppressed. Consequently, film formation on the ring-shaped member can be prevented.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter.
REFERENCES:
patent: 5133284 (1992-07-01), Thomas
patent: 5326725 (1994-07-01), Sherstinsky et al.
patent: 5447570 (1995-09-01), Schmitz et al.
patent: 5624499 (1997-04-01), Mizuno
patent: 5882417 (1999-03-01), van de Ven
patent: 5882419 (1999-03-01), Sinha
patent: 5-190471 (1993-07-01), None
Kawano Yumiko
Mizukami Masami
Mochizuki Takashi
Bueker Richard
Oblon & Spivak, McClelland, Maier & Neustadt P.C.
Tokyo Electron Limited
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