Polysilicon resistor formation in a gate-last process
First Claim
Patent Images
1. A method comprising:
- forming a polysilicon layer over a substrate;
forming a hard mask over the polysilicon layer;
doping a first portion of the hard mask with a dopant to form a doped hard mask region, wherein a second portion of the hard mask is not doped with the dopant;
performing an etching step to etch the first and the second portions of the hard mask, wherein the second portion of the hard mask is removed, and wherein at least a bottom portion of the doped hard mask region is not removed;
after the etching step, removing the bottom portion of the doped hard mask region; and
forming electrical connections to connect to a portion of the polysilicon layer in order to form a resistor.
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Abstract
A method includes forming a polysilicon layer over a substrate, forming a hard mask over the polysilicon layer, and doping a first portion of the hard mask with a dopant to form a doped hard mask region, wherein a second portion of the hard mask is not doped with the dopant. An etching step is performed to etch the first and the second portions of the hard mask, wherein the second portion of the hard mask is removed, and wherein at least a bottom portion of the doped hard mask region is not removed. After the etching step, the bottom portion of the doped hard mask region is removed. Electrical connections are formed to connect to a portion of the polysilicon layer in order to form a resistor.
13 Citations
20 Claims
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1. A method comprising:
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forming a polysilicon layer over a substrate; forming a hard mask over the polysilicon layer; doping a first portion of the hard mask with a dopant to form a doped hard mask region, wherein a second portion of the hard mask is not doped with the dopant; performing an etching step to etch the first and the second portions of the hard mask, wherein the second portion of the hard mask is removed, and wherein at least a bottom portion of the doped hard mask region is not removed; after the etching step, removing the bottom portion of the doped hard mask region; and forming electrical connections to connect to a portion of the polysilicon layer in order to form a resistor. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A method comprising:
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forming a polysilicon layer over a substrate; forming a hard mask layer over the polysilicon layer; forming a photo resist over the hard mask layer and patterning the photo resist; implanting the polysilicon layer with a first dopant to form a doped polysilicon region in the polysilicon layer; implanting the hard mask layer with a second dopant to form a doped hard mask region in the hard mask layer, wherein the steps of implanting the polysilicon layer and the hard mask layer are performed using the photo resist as an implantation mask; etching the hard mask layer, wherein portions of the hard mask layer not doped with the second dopant are substantially fully removed after the step of etching, and wherein the doped hard mask region has at least a bottom portion not removed after the step of etching; and replacing a portion of the polysilicon layer not covered by the doped hard mask region with a gate stack of a transistor. - View Dependent Claims (8, 9, 10, 11, 12, 13)
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14. A method comprising:
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forming a polysilicon layer over a substrate; forming a first photo resist over the polysilicon layer and patterning the first photo resist; implanting the polysilicon layer with a first dopant to form a doped polysilicon region in the polysilicon layer, wherein the polysilicon layer is implanted using the first photo resist as a mask; after the step of implanting the polysilicon layer, forming a hard mask layer over the polysilicon layer; etching the hard mask layer and the polysilicon layer to form a first opening over a well region in the substrate; forming a second photo resist into the first opening and over the hard mask layer; patterning the second photo resist to form a second opening in the second photo resist, wherein the second opening is over and overlapping the doped polysilicon region; implanting the hard mask layer with a second dopant to form a doped hard mask region in the hard mask layer, wherein the step of implanting the hard mask layer is performed using the second photo resist as an implantation mask; etching the hard mask layer, wherein portions of the hard mask layer not doped with the second dopant are etched through, and wherein the doped hard mask region has at least a bottom portion not removed; and replacing a portion of the polysilicon layer with a gate stack of a transistor. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification