METHOD FOR FORMING TRENCH MOSFET DEVICE WITH LOW PARASITIC RESISTANCE

摘要

A method is provided for forming shallow and deep dopant implants adjacent source regions of a first conductivity type within an upper portion of an epitaxial layer in a trench MOSFET device. The method comprises: (a) forming a patterned implantation mask over the epitaxial layer, wherein the patterned implantation mask comprises a patterned insulating region and covers at least a portion of the source regions, and wherein the patterned implantation mask has apertures over at least portions of the epitaxial layer adjacent the source regions; (b) forming shallow dopant regions by a process comprising: (1) implanting a first dopant of a second conductivity type at a first energy level within an upper portion of the epitaxial layer through the apertures and (2) diffusing the first dopant at elevated temperatures to a first depth from an upper surface of the epitaxial layer; (c) forming deep dopant regions by a process comprising: (1) implanting a second dopant of the second conductivity type at a second energy level within an upper portion of the epitaxial layer through the apertures and (2) diffusing the second dopant at elevated temperatures to a second depth from the upper surface of the epitaxial layer; and (d) enlarging apertures in the patterned insulating region. In this method, the second energy level is greater than the first energy level, the second depth is greater than the first depth, and the first and second dopants can be the same or different. The method of the present invention can be used, for example, to form a device that comprises a plurality of trench MOSFET cells.