| 摘要 |
PROBLEM TO BE SOLVED: To form a quartz film as a lower clad layer having a high purity and high density in a short time by changing an upper surface part of a base board to a porous film by an anodic oxidation method, and forming a lower clad layer by changing the porous film to an oxide film. SOLUTION: An Si wafer 28 is used as a base board, and an Al electrode 30 is formed on one side surface of the Si wafer 28. A structure body is formed by covering a side surface of the Si wafer 28 and a surface of the Al electrode 30 with a resist film. Anodic oxidation is performed by using this structure body as an anode, an a surface of the Si wafer 28 contacting with electrolyte is changed to a porous Si film 48. The Si wafer 28 on which the porous Si film 48 is formed is cleaned by pure water, and the Al electrode 30 on the reverse is removed by etching. The porous Si film 48 is oxidized by heat treatment. An obtained oxidized porous Si film 50 is melted, and an SiO2 film 52 as a lower clad layer is formed on a surface of an Si layer 28a. |
