1. Field of the Invention
The invention relates to a manufacturing apparatus for a semiconductor device and a manufacturing method for a semiconductor device that form a film, for example, on a semiconductor wafer by supplying a reactive gas while heating the semiconductor wafer from a back side.
2. Description of the Related Art
In recent years, with a semiconductor device having an increasingly finer structure, better uniformity in film thickness of a film formation process has been required. In a CVD (Chemical Vapor Deposition) apparatus such as an epitaxial growth apparatus, a backside heating method in which there is no heating source from above is used. Since a reactive gas can be supplied in a vertical direction from above when the backside heating method is used, a uniform film can be formed. To achieve still better uniformity in film thickness by the backside heating method, the in-plane temperature of a wafer must be controlled to be uniform. Various techniques so as to heat a wafer uniformly are described in Japanese Patent Application Laid-Open No. 2000-306850 or the like.
In recent years, there is a trend of using a larger-diameter wafer to reduce costs of devices and a requirement for an increase in an effective area of a wafer is growing. Also, with devices having an increasingly finer structure, a requirement for more accurate film thickness is rising. Thus, the film must be formed uniformly up to an edge near area of a wafer, which has hitherto been cut off. However, if the in-plane temperature of a wafer is controlled by output of the heater being controlled, the temperature of a holder holding the wafer will also vary. The temperature of an outermost circumference of a wafer depends on the temperature of a holder. Therefore, it is difficult to stabilize the temperature only by controlling output of the heater.
For example, when forming a film, the temperature rises only in edges of a wafer, causing a temperature difference between the center of a wafer and its edges of ±5-6° C. Due to this temperature difference, the thickness of a formed film (epitaxial film) varies by 1% or so. In addition, temperature variations cause slippage in the wafer. Particularly due to change of the process gas from a mono-silane gas to trichlorosilane gas, which is superior in productivity, the processing temperature has risen from 1050° C. to 1100° C. With a rising temperature of processes, the problem of slippage is becoming evident.