High performance sub-micron P-channel transistor with germanium implant

Abstract

Implantation of germanium (45) into a PMOS buried channel to permits the enhancement implant profile (to 45) to be made more shallow. The shallow profile will reduce or eventually solve P-channel buried channel-induced short channel effects and enable further decrease in device length to deep submicron range.Benefits include better short channel characteristics, i.e., higher punch through voltage BVDSS, less VT sensitivity to the drain voltage (defined as curl) and better subthreshold leakage characteristics.

Description

FIELD OF THE INVENTIONThis invention is related to semiconductor devices. Specifically it is related to high-performance sub-micron channel length P-channel MOS (metal-oxide-semiconductor) transistor (PMOS for short) for the Very Large Scale Integrated (VLSI) or the Ultra Large Scale Integrated (ULSI) circuits. It employs the use of Germanium implant into the channel regions of transistors to both pre-amorphize the channel surface to alleviate the channelling of subsequent enhancement implant required by threshold voltage Vt adjustment and to retard the diffusion of the boron dopants (from enhancement implant) in the region to form a very shallow enhancement implant profile.BACKGROUND OF THE INVENTIONThe invention uses various materials which are electrically either conductive, insulating or semiconducting, although the completed semiconductor circuit device itself is usually referred to as a "semiconductor". One of the materials used is silicon, which is used as either single cryst...

AI Technical Summary

Benefits of technology

The present invention deals directly with PMOS buried channel characteristics by making the buried channel enhancement implant profile more shallow. The shallow implant profile results in the P-CH device will have less or no buried channel characteristics. This avoids undesirable short channel effects, and therefore permits further reduction in the transistor channel length.

The shallow profile causes surface channel characteristics to be dominant. Surface channel devices will have better short channel characteristics, i.e., higher punch through voltage BVDSS, less V.sub.T sensitivity to the drain voltage (defined as curl) and better subthreshold leakage characteristics.

Implantation of germanium into the channel to permit the enhancement implant profile to be made shallower will reduce or event solve P-channel buried channel-induced short channel effects and enable further decrease in device length to deep sub-micron range.

Problems solved by technology

The former deals with device isolation and an improvement in electrical encroachment; yet it does not improve transistor performance; the later deals with device performance by means of achieving shallower source drain junction depths so that the reduction in charge-sharing effect would improve transistor short channel characteristics.

It however does not solve or reduce P-channel transistor short channel effects caused by the very nature of buried channel behaviour.

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