Maskless process for forming refractory metal layer in via holes

Details Maskless process for forming refractory metal layer in via holes Maskless process for forming refractory metal layer in via holes

1994-01-13

1994-09-27

McCamish, Marion E.

Radiation imagery chemistry: process, composition, or product th

Imaging affecting physical property of radiation sensitive...

Making electrical device

430311, 430318, 430329, 156656, 1566591, 427512, G03F 720

Patent

active

053506626

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).

REFERENCES:
patent: 4268537 (1981-05-01), Goodman
patent: 4983252 (1991-01-01), Masui

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