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Double Diffused Metal Oxide Silicon FET

IP.com Disclosure Number: IPCOM000086395D
Original Publication Date: 1976-Sep-01
Included in the Prior Art Database: 2005-Mar-03
Document File: 2 page(s) / 45K

Publishing Venue

IBM

Related People

Chakravarti, SN: AUTHOR [+4]

Abstract

The double-diffusion technique has a drawback of excessive capacitance associated with the double-diffused source diffusion. This process significantly reduces such capacitance by utilizing a reactive ion etching technique with approximately zero etch bias and directionality of ion implantation.

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Double Diffused Metal Oxide Silicon FET

The double-diffusion technique has a drawback of excessive capacitance associated with the double-diffused source diffusion. This process significantly reduces such capacitance by utilizing a reactive ion etching technique with approximately zero etch bias and directionality of ion implantation.

Referring to Fig. 1, a semiconductor wafer 1 is cleaned and prepared in the usual manner and a reoxidization isolation area 2 is formed. A gate oxide 3 is formed after a channel implant and a layer of amorphous silicon 4 is deposited followed by a cap of silicon dioxide 5 and a layer of silicon nitride 6 and pyrolytic silicon dioxide 7. The recessed oxide is grown after the field implant for threshold adjustment and surface tailoring.

The polysilicon is etched to form the polysilicon gate structure shown in Fig.
2. The silicon dioxide 8 is grown on the exposed silicon and masked from subsequent etching and ion implantation steps using photoresist 9. Implantation of boron, shown by arrows 18 in Fig. 2, removal of the photoresist layer 9, and subsequent drive-in of the implanted boron are undertaken to form the P region 19 (fig. 3).

Using reactive ion etching, the source region 10 is formed and the silicon dioxide 8 removed, followed by an n+ source and drain region implant 11 and 12, as shown in Fig. 4. High dose and energy is utilized for ultimate deep n+ junction (Fig. 5) after subsequent oxidization steps.

As shown in Fig. 5, the...