Photochemical vapor phase reaction apparatus and method of causing a photochemical vapor phase reaction

A photochemical vapor phase reaction apparatus comprising:

• a reaction space;
• a gas feeding system for supplying a reactive gas to said reaction space;
• a light source for emitting light rays, said light source being provided in a light source room separated from said reaction space by a light window in an air-tight manner;
• a substrate holder for holding a substrate in said reaction space;
• means for condensing and projecting the light rays emitted from said light source onto said substrate on said holder in order to cause a photochemical vapor phase reaction to said reactive gas in said reaction space, and
• a mechanism for adjusting the distance between said light ray condensing means and said substrate by changing the location of said light ray condensing means to vary its distance from the substrate holder and thereby changing the extent to which the light rays are condensed as they travel from the light ray condensing means, through the light window, onto said substrate.