초록 ▼

The specification describes methods for making T-shaped metal gates for Schottky gate devices such as MESFETs and HEMTs. The method uses a bi-level photoresist technique to create a T-shaped feature for the gate structure. The metal gate is evaporated into the photoresist T-shaped feature and a lift

The specification describes methods for making T-shaped metal gates for Schottky gate devices such as MESFETs and HEMTs. The method uses a bi-level photoresist technique to create a T-shaped feature for the gate structure. The metal gate is evaporated into the photoresist T-shaped feature and a lift-off process is used to remove unwanted metal. The photoresist is the dissolved away leaving the T-shaped gate. An important aspect of the process is the use of a plasma treatment of the first patterned resist level to harden it so that it is unaffected by the subsequent deposition and patterning of the second level resist.

대표청구항 ▼

[ We claim:] [1.] A method for the manufacture of a Schottky gate transistor comprising the steps of:forming a source and drain in a III-V semiconductor substrate, andforming a Schottky gate on the surface of said III-V semiconductor between said source and drainthe invention characterized in that s

[ We claim:] [1.] A method for the manufacture of a Schottky gate transistor comprising the steps of:forming a source and drain in a III-V semiconductor substrate, andforming a Schottky gate on the surface of said III-V semiconductor between said source and drainthe invention characterized in that said Schottky gate is formed by the steps comprising:a. depositing a first level of photoresist on the surface of said substrate, said first level of photoresist having a thickness t.sub.1,b. lithographically forming an opening in said first level of photoresist, said opening having a rectangular shape with width w.sub.1, and length l.sub.1, with the length dimension extending along the direction separating the source and drain,c. exposing said first level of photoresist to a plasma to form a surface layer on said first level of photoresist to harden said surface layer and render it lithographically passive,d. depositing a second level of photoresist on said first level of photoresist, said second level of photoresist having a thickness t.sub.2,e. lithographically forming an opening in said second level of photoresist, said opening coinciding with said opening in said first level of photoresist and having a rectangular shape with width w.sub.2 and length l.sub.2, and further where length l.sub.2 is greater than length l.sub.1,f. depositing a metal layer to fill said first opening and to fill a portion of said second opening, said metal layer having a thickness h.sub.1 +h.sub.2, where h.sub.1 is essentially equal to t.sub.1 and h.sub.2 is substantially less than t.sub.2,g. and dissolving away said first and second level of photoresist leaving a T-shaped Schottky gate.