Browse Prior Art Database

MESFETs with Self Aligned Refractory Contacts

IP.com Disclosure Number: IPCOM000109261D
Original Publication Date: 1992-Aug-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 2 page(s) / 92K

Publishing Venue

IBM

Related People

Lustig, N: AUTHOR [+3]

Abstract

A novel method to fabricate MESFETs with self-aligned contacts is described. The method utilizes a tri-density photoresist (PR) mask in conjunction with two oblique implants.

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MESFETs with Self Aligned Refractory Contacts

       A novel method to fabricate MESFETs with self-aligned
contacts is described.  The method utilizes a tri-density photoresist
(PR) mask in conjunction with two oblique implants.

      Self-aligned contacts are utilized in Si MOSFET technology to
create high density ICs.  Fabrication of the contacts in Si is
possible because refractory metals (W, Mo, Ti) react selectively with
Si when both Si and SiO2 are present.  Therefore, when the sidewalls
of a gate in a MOSFET are covered with SiO2, self-aligned contacts
can be achieved by both the CVD of W and deposition of a thin layer
of Ti followed by a heat treatment.  The processes of MOSFET
technology cannot be easily extended to compound semiconductors
because unlike Si, the native oxide on these semiconductors is
neither chemically inert nor thermally stable, and have poor
electrical qualities.  Furthermore, there is no known selective
contact reaction in compound semiconductors.  Consequently,
fabrication of ohmic contacts to a device, such as a MESFET on these
semiconductors requires a lift-off process which results in
non-self-aligned contacts.  A minimum distance between the gate and
source/drain of the order of the  photolithography alignment
tolerance ( >N 0.2 mm) has to be maintained to avoid a short in the
device.  This is obviously an impediment to achieve high density ICs
on compound semiconductors.

      The present disclosure utilizes two no...