Maskless process for forming refractory metal layer in via holes of GaAs chips

U.S. Patent Number: 5350662

Abstract: A "maskless" process is provided for the formation of a refractory metal layer (22b), such as titanium, in via holes (18) through GaAs wafers (12) to contact microwave monolithic integrated circuit (MMIC) devices (10) formed on the front surface (12a) thereof. The process of the invention, which prevents AuSn solder (28) from filling up the holes during a subsequent eutectic AuSn bonding of the device to a metal carrier (30), such as molybdenum, utilizes the difference of resist thickness on the GaAs backside surface (12b) and in the via holes, so that the resist (24b) remaining in the via holes after removing the resist (24a) over the GaAs back surface serves as a mask in etching the refractory metal layer (22a) over the GaAs back surface. The process of the invention does not require any masks, and results in self-alignment of the refractory metal to the via hole. The process is simple and results in high yield of the MMIC devices on GaAs chips (26).

Inventors: Chi; Tom Y. (San Gabriel, CA)

Assignee: Hughes Aircraft Company (Los Angeles, CA)

Application Number: 08/181,371

Issued: 1994-09-27

Expired: 2006-09-27

Classes: 430/313 ; 216/39; 216/48; 257/E21.027; 257/E23.011; 427/512; 430/311; 430/318; 430/329

Field of search: 430/311,313,314,318,319,323,327,329 156/643,656,659.1 427/508,512

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