| 摘要 |
PURPOSE:To prevent the occurrence of steps in a waveguide layer to improve a semiconductor device in performance by a method wherein a negative photoresist and a positive photoresist forming a periodic stripe-like pattern are exposed to light and developed, and a semiconductor substrate is etched using both residual resist films as mask. CONSTITUTION:A positive photoresist film 2 is applied onto a semiconductor substrate 1, which is exposed to laser rays to form a periodic stripe-like pattern of the resist film 2. Next, a negative photoresist film 3 is applied to fill the gap of the stripe-like pattern of the film 2. Then, the resist films 2 and 3 are exposed to light through a mask 4. In this process, the mask 4 is so arranged as to make its ends parallel with the stripes. Next, the resist films 2 and 3 are developed respectively to remove the exposed resist film 2 and the non- exposed resist film 3. And, the substrate 1 is etched using the resist films 2 and 3 left unremoved as a mask, and a waveguide layer 5, an active layer 6, and a clad layer 7 are formed, consequently a phase shift distributed feedback type laser can be improved in performance. |
