Browse Prior Art Database

One Device Storage Cell Method

IP.com Disclosure Number: IPCOM000079718D
Original Publication Date: 1973-Aug-01
Included in the Prior Art Database: 2005-Feb-26
Document File: 2 page(s) / 28K

Publishing Venue

IBM

Related People

LeBlanc, AR: AUTHOR

Abstract

This is a method of making a one-device storage cell 10 which includes a field-effect transistor 12 and a storage capacitor 14, as described in U. S. Patent 3,387,286 granted to R. H. Dennard. This cell employs a heavy concentration of ion implanted acceptors 16 in a P-type epitaxial layer 18 of a silicon semiconductor wafer, beneath a thick thermal silicon dioxide layer 20 and a concentration of ion donors forming source and drain regions 22 and 24, implanted through thin oxide layer 26. The acceptors 16, which may be boron, are concentrated at the Si-SiO(2) interface to provide a heavily doped P-surface, which prevents inversion when transistor 12 is an N-channel transistor.

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One Device Storage Cell Method

This is a method of making a one-device storage cell 10 which includes a field-effect transistor 12 and a storage capacitor 14, as described in U. S. Patent 3,387,286 granted to R. H. Dennard. This cell employs a heavy concentration of ion implanted acceptors 16 in a P-type epitaxial layer 18 of a silicon semiconductor wafer, beneath a thick thermal silicon dioxide layer 20 and a concentration of ion donors forming source and drain regions 22 and 24, implanted through thin oxide layer 26. The acceptors 16, which may be boron, are concentrated at the Si-SiO(2) interface to provide a heavily doped P-surface, which prevents inversion when transistor 12 is an N-channel transistor. Some of the acceptors 16 which pass through thin oxide layer 26 are implanted deeper into semiconductor layer 18, so as not to affect source and drain regions 22 and
24.

Prior to implanting ions into semiconductor layer 18, electrodes 28 and 30, which may be made of polysilicon or refractory metals, are disposed on thin oxide layer 26. These electrodes 28 and 30, electrode 28 being used as a gate electrode for transistor 12 and electrode 30 being used as a capacitor electrode for storage capacitor 14, act as shields which prevent contamination of the portion of thin oxide layer 26 under the electrodes. Thick oxide layer 20 and electrode 28 and 30 act as shields, when source and drain regions 22 and 24 are being formed by ion implantation.

Fabrication steps inc...