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Multiple Fin Polysilicon Storage Node Over a Transistor Switch Cell

IP.com Disclosure Number: IPCOM000036803D
Original Publication Date: 1989-Oct-01
Included in the Prior Art Database: 2005-Jan-29
Document File: 3 page(s) / 36K

Publishing Venue

IBM

Related People

Davis, A: AUTHOR

Abstract

This article describes a multiple fin polysilicon storage node placed over a transistor switch cell, resulting in a dense and high signal capacity DRAM semiconductor cell configuration.

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Multiple Fin Polysilicon Storage Node Over a Transistor Switch Cell

This article describes a multiple fin polysilicon storage node placed over a transistor switch cell, resulting in a dense and high signal capacity DRAM semiconductor cell configuration.

As spacing between devices narrows, moving the storage node either above or below the transfer device allows the space between transistors to shrink and still maintain a reasonable storage node area. This memory cell design does not use the currently popular trench and strapping process to structure a storage node; rather a multiple fin storage means is utilized.

The following describes the sequence of steps required to make a high density DRAM cell with a finned capacitive storage node located over the transistor switch:

MASK #1:

Define recessed oxide (ROX) regions. Any isolation

may be used.

Implant, grow ROX and tailor.

Grow gate oxides.

Deposit polysilicon or silicides, if used.

Deposit Pyro cap layer. (1,000 - 2,000 angstroms is

sufficient.)

Deposit 500 - 1,000 angstroms of nitride.

MASK #2:

Define polysilicon gates and interconnects and then

etch.

Deposit Pyro and etch to form spacers.

Deposit nitride to increase spacer thickness and etch.

Implant source/drain (S/D) and reoxidize.

Deposit 10,000 angstroms of intrinsic polysilicon.

Deposit 1,500 angstroms of nitride as an etch stop.

Deposit 1,000 angstroms of Pyro as an etch mask.

MASK #3:

Define node areas and open nitride and Pyro.

Selective etch down to S/D oxide. Cap protects

polysilicon regions.

Oxidize intrinsic polysilicon fill to form sidewall

isolation.

Etch bottom to open diffused node region.

Deposit approximately 1,000 angstroms of polysilicon.

Deposit approximately 1,000 ang...