| 摘要 |
PURPOSE:To suppress the warpage of a wafer as well as to improve the mask- patterning accuracy in a photolithographic process by a method wherein a polycrystalline silicon layer is formed on the back side of a silicon substrate of a high impurity density. CONSTITUTION:A silicon epitaxial layer 22 of low impurity density is formed on the surface of a silicon substrate 21 of high impurity density, and a polycrystalline silicon layer 23 is formed on the back side. As a result, the stress generating between the substrate 21 and the silicon epitaxial layer 22, and the substrate 21 and the polycrystalline silicon layer 23 works each other in the direction wherein the wafer is warped in the reverse direction, thereby enabling to lessen the wafer warpage. The impurity density is to be brought within the range of 1X 10<-18>cm<+3>-1X10<20>cm<-3> for the silicon substrate 21, and 1X10<14>cm<-3>-1X 10<16>cm<-3> for the silicon epitaxial layer 22, for example. |
