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Combined Shallow and Deep Junction Self Aligned MOSFET Process

IP.com Disclosure Number: IPCOM000048322D
Original Publication Date: 1982-Jan-01
Included in the Prior Art Database: 2005-Feb-08
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Adler, E: AUTHOR

Abstract

This MOSFET process provides a self-aligned polysilicon gate device having reduced short-channel effect, higher snap-back and sustaining voltage and lower gate to diffusion overlap capacitance by combining a multi-thickness gate etching technique with a double source-drain ion implantation technique.

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Combined Shallow and Deep Junction Self Aligned MOSFET Process

This MOSFET process provides a self-aligned polysilicon gate device having reduced short-channel effect, higher snap-back and sustaining voltage and lower gate to diffusion overlap capacitance by combining a multi-thickness gate etching technique with a double source-drain ion implantation technique.

Referring to Fig. 1, a conventional polysilicon gate process is used to up through formation of the gate oxide 12 on semiconductor substrate 10. The polysilicon gate is deposited as two sublayers. A first layer 14 of intrinsic polysilicon is deposited having a thickness of about 1000 angstroms. This is followed by an in-situ phosphorus doped polysilicon layer 16 of greater thickness. Layer 16 may also be formed of a refractory metal, such as an evaporated silicide.

Gate electrode layers 14 and 16 are patterned by a conventional photoresist layer 18, followed by a dry, plasma etching process. The etching process is selected to provide selective isotropic etching of the doped polysilicon layer 14 in order to achieve an etch bias of about 0.2 - 0.3 micron, as shown in Fig. 2.

The etching conditions are then charged to provide directional etching of the undoped polysilicon layer 14 so that etching only occurs outside of the shadowing effect provided by photoresist layer
18. The photoresist is removed, and the source-drain regions are ion-implanted in two ion-implantation steps. One step includes a low dose, h...