ApplicationNo. 576912 filed on 05/12/1975
US Classes:438/144, Charge transfer device (e.g., CCD, etc.)257/249, Electrode structures or materials257/E21.346, Using mask (EPO)257/E29.058, Of charge coupled devices (EPO)257/E29.229, With field effect produced by insulated gate (EPO)438/526, Forming buried region438/587, Forming array of gate electrodes438/770, Oxidation438/911DIFFERENTIAL OXIDATION AND ETCHING
ExaminersPrimary: Rutledge, L. Dewayne
Assistant: Davis, J.
Attorney, Agent or Firm
AbstractA semiconductor substrate is coated with an insulating film followed by a layer of polysilicon. The polysilicon layer is coated with a non-oxidizable mask, such as silicon nitride, and then oxidized to convert the exposed regions to silicon oxide and add further thickness to the converted oxide regions. When the mask is removed, the thicker silicon oxide regions serve as an in situ mask for selectively implanting impurity ions through the thinner polysilicon regions and into the semiconductor substrate. When the silicon oxide regions are etched away, the remaining polysilicon regions serve as an ion implantation mask for permitting selective ion implantation through the voids left by etching the silicon oxide regions.