Conventionally, in a manufacturing process of a semiconductor element that requires a crystal film having a relatively large film thickness, like a power device such as an IGBT (Insulated Gate Bipolar Transistor), an epitaxial growth technique of performing vapor phase growth of a single-crystal thin film on a substrate such as a wafer for film formation is employed.
In a film formation apparatus used for the epitaxial growth technique, for example, a wafer is placed in a film formation chamber that is kept at an ordinary pressure or a reduced pressure. While this wafer is heated, a gas serving as a source for film formation (hereinafter, also simply “source gas”) is supplied to the film formation chamber. Subsequently, a thermal decomposition reaction and a hydrogen reduction reaction of the source gas occur on a surface of the wafer, thereby forming an epitaxial film on the wafer.
To manufacture an epitaxial wafer having a large film thickness with a high yield, it is necessary for a surface of a wafer to successively contact new source gases to increase the vapor-phase growth rate. Therefore, epitaxial growth is performed while a wafer is rotated at a high speed (see, for example, Patent Document 1).
In conventional film formation apparatus, a gas supply unit that supplies a source gas is provided at the top of a film formation chamber. A shower plate having a large number of source gas ejection holes formed thereon is connected to the gas supply unit. By using this shower plate, the source gas flow in the film formation chamber is uniformized and the source gas is uniformly supplied onto a wafer.
Because high-temperature heating at 1600° C. or more is required in SiC epitaxial growth and the like, a film formation apparatus including an auxiliary heater that heats a wafer from above has been used in addition to a heater that heats a wafer from below. This type of film formation apparatuss performing high-temperature heating have a problem that a supplied source gas contacts an inner wall surface of a film formation chamber, a film is deposited on the inner wall surface, and the film deposited on the inner wall surface is peeled off, so that particles are generated. There is another problem that, when an etching gas is supplied from a gas supply unit to clean a deposited material, an inner wall member of the film formation chamber is corroded, so that particles are generated. Furthermore, there is still another problem that it takes a long time to increase the temperature within the film formation chamber or to cool the film formation chamber.
An object of the present invention is to provide a film formation apparatus and a film formation method that can suppress generation of particles and can reduce a temperature-increasing time and a cooling time.