Patent ID: 8822294
Filing Date: 2014-09-02
Classification: H01L

Abstract:
1. A method for improving the write margins of the SRAM cells comprising: before etching a polysilicon layer to form the polysilicon gates, performing a pre-implantation process to the polysilicon layer; wherein the polysilicon layer defines SRAM NMOSFETs regions, non-SRAM NMOSFETs regions, SRAM PMOSFETs regions and non-SRAM PMOSFETs regions; the pre-implantation process comprises pre-implanting the fifth-group elements to the SRAM NMOSFETs regions as well as the non-SRAM NMOSFETs regions in the polysilicon layer, and pre-implanting the third-group elements to the non-SRAM PMOSFETs regions in the polysilicon layer; wherein the process of pre-implanting the third-group elements comprises forming a pre-implantation photo mask capable of covering the SRAM PMOSFETs regions and using the pre-implantation photo mask to pre-implanting the third-group elements.