Low temperature coefficient of resistance, GaPt/PtAs/sub 2/ integrated circuit resistor

Abstract

A gallium platinum/platinum arsenide (GaPt/PtAs/sub 2/) resistor structure is described that is well suited to gallium arsenide (GaAs) monolithic microwave integrated circuits (MMICs). Its advantages are: a near-zero temperature coefficient of resistance (TCR), ease of manufacture, and mechanical and electrical stability during later high-temperature integrated circuit processing steps and during lifetests. This resistor process consistently achieves 0.015%/ degrees C TCR (2.1% total change for -55 to +85 degrees C). This is 20 times smaller than the TCR from a typical metal film or active GaAs resistor. This resistor is fabricated by alloying an evaporated Pt film of critical thickness. The TCR is in fact adjustable from -0.12%/ degrees C to +0.18%/ degrees C by adjusting the initial Pt film thickness. A reliable, low resistance contact is achieved by depositing a contact metallurgy before alloying to avoid having to make electrical contact through the insulating GaO layer that forms during the alloying process. The resistor is stable to high process temperatures and has long-term reliability because of the high alloying temperature of 525 degrees C. >