International Business Machines Corporation

Robert B Renbeck

S Noor Mohammad

Keith M Walter

Shaikh N Mohammad

Chakrapani G Jambotkar

Karanam Balasubramanyam

Robert R Joseph

A superheterojunction Field Effect Transistor (FET) with a multi-region channel on a Silicon (Si) substrate. The FET is a Metal Semiconductor FET (MESFET) or, alternatively, a Junction FET (JFET). The multi-region channel has: A first region of Si extending from the FET's source to a point under the FET's gate, beyond the gate's midpoint; a second region extending from the first region to the FET's drain, comprised of a superlattice of alternating Si and SiGe layers; and, a third region of Si extending under the first two regions from the source to the drain. The first region has a laterally graded dopant that creates an accelerating electric field. The superlattice structure increases electron mobility and transit velocity.

Method of making a high performance MESFET with multiple quantum wells

A Conductor Insulator Semiconductor (CIS) heterojunction transistor. The CIS transistor is on silicon (Si) substrate. A layer of n type Si is deposited on the substrate. A trench is formed through the n type Si layer, and may extend slightly into the substrate. The trench is filled with an insulator, preferably SiO.sub.2. A layer of p type Si.sub.1-z Ge.sub.z (where z is the mole fraction of Ge and 0.1.ltoreq.z.ltoreq.0.9) is deposited on the n type Si layer. A p.sup.+ base contact region is defined in the p type Si.sub.1-z Ge.sub.z region above the oxide filled trench. A n type dopant is ion implanted into both the Si.sub.1-z Ge.sub.z and n Si layers and may extend slightly into the substrate, forming a collector region. A thin oxide layer is deposited on the Si.sub.1-z Ge.sub.z layer and a low work function metal such as Al, Mg, Mn, or Ti is selectively deposited on the thin oxide and to define an emitter. Alternatively, the emitter may be p.sup.+ polysilicon. Next, the thin oxide is opened to define collector and base contacts. A suitable metal, such as Al is deposited in the base and collector contacts.

Method of making carrier conduction conductor-insulator semiconductor

Carrier conduction conductor-insulator semiconductor (CIS) transistor

High performance MESFET with multiple quantum wells

Disclosed is a process fo fabrication of a MESFET in which starting with a GaAs substrate having a shallow N- layer covered with nitride, a submicron-wide dummy gate mask consisting of upper and lower portions made of dissimilar materials is formed. Multilayer organic and sidewall image transfer techniques are employed for forming the mask. The nitride is etched using the gate mask. N+ source/drain are formed by ion implantation. The lower portion of the gate mask is etched to expose the periphery of the nitride. Refractory metal for source/drain contacts is deposited. An oxide laeyr is deposited to passivate the source/drain contacts and to fully cover the exposed nitride periphery. The gate mask is removed. High temperature anneal is accomplished to simultaneously activate the N+ regions and anneal the contact metal. By RIE the exposed nitride removed leaving submicron spacers thereof. Gate metal is deposited in the gate region. Excess gate metal is removed to obtain a gate which has a planar top and has little lapping over the source/drain contacts.

High speed GaAs MESFET having refractory contacts and a self-aligned

Disclosed is a process for forming a high-speed, self-aligned GaAs-gate field effect transistor with submicron channel length. Starting with a semi-insulating GaAs substrate having a thin gate insulator layer of undoped AlGaAs and a comparatively thick highly doped GaAs layer, a metal contacting the doped GaAs layer is controllably formed by sidewall image transfer and planarization etchback technique. The thickness and width of the metal strip are in the low submicron range. Using the metal strip as a mask, the doped GaAs is patterned into a GaAs gate for the FET having the characteristics of submicron width (i.e., the dimension of the gate measured along the source-drain), substantially vertical walls and contacted on the top thereof in a self-aligned relationship by the metal strip. Next, a submicron wide insulator sidewall is formed on the vertical walls of the gate. By ion implanation across the AlGaAs layer using the gate structure and a patterned photoresist as a mask, source and drain are formed in the substrate in self-aligned relation with the gate. Contact metallization is formed to electrically contact the source, drain and the gate.

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Staatsburg, NY, United States of America

Robert B Renbeck