In order to manufacture a semiconductor device on a target substrate, such as a semiconductor wafer or an LCD substrate, film formation by deposition, such as CVD, or film formation by diffusion, such as thermal oxidation is utilized. In such semiconductor processes, a process gas is supplied while the target substrate is heated, so that a predetermined process is performed.
For example, a conventional CVD apparatus for processing semiconductor wafers one by one employs a heating body, such as a ceramic heater, incorporated in a worktable arranged in a process chamber. A plurality of lifter pins are also incorporated in the worktable, for moving each wafer up and down relative to the worktable. A shower head is disposed above the worktable, for supplying a process gas.
One wafer is transferred onto the lifter pins by a transfer arm, and mounted on the worktable by the lifter pins moving down. Then, the wafer mounted on the worktable is heated by the heating body to a predetermined process temperature. In this state, the process gas is supplied while the process chamber is exhausted, so that a thin film is formed on the wafer by deposition.
However, in the above described conventional apparatus, a certain temperature distribution is generated on the mount surface of the worktable such that it corresponds to the wiring pattern of a resistance heating wire in the ceramic heater used as the heating body. The wafer copies the temperature distribution pattern formed on the mount surface, thereby causing an unevenness in its temperature. As a result, a decrease is brought about in planar uniformity of the thickness and quality of the formed thin film.
Further, in the above described conventional apparatus, the thin film is formed continuously from the peripheral edge of the wafer to the surface of the worktable. When the wafer is pushed up from the worktable after the thin film is formed, the thin film is peeled off between the wafer W and the worktable, and generates particles.
Jpn. U.M. Appln. KOKAI Publication No. 5-33535 discloses a CVD apparatus having a susceptor provided with a plurality of pins, on which a wafer is mounted while a thin film is formed. This apparatus entails a decrease in processing efficiency and a decrease in utility efficiency of processing energy, because the wafer is indirectly heated.