A GaAs HEMT MMIC chip set for automotive radar systems fabricated by optical stepper lithography

Abstract

A 77-GHz automotive radar system for collision avoidance and intelligent cruise control has recently gained interest because of its huge market potential. The questions of the optimum technological and system approaches leading to both low cost and high performance have not yet been finally answered. The approach to this problem reported here differs mainly in two aspects from the GaAs monolithic microwave integrated circuit (MMIC) solutions described earlier: 1) 0.12-mu m gatelength pseudormorphic high electron mobility transistors (PHEMT's) are fabricated by optical stepper lithography, 2) a coplanar design is used. A fully passivated PHEMT MMIC fabrication process is reported with current-gain and power-gain cutoff frequencies exceeding 115 and 220 GHz, respectively. The design and performance of a chip set consisting of four different MMIC's [voltage controlled oscillator (VCO), harmonic mixer, transmitter, receiver] are described. The great potential of this MMIC approach to meet all system requirements of an automotive radar sensor in a cost-effective and production-oriented way is shown. To our knowledge, this is the first demonstration of W-band coplanar multifunctional MMIC's fabricated by optical stepper lithography

Over 10W/mm High Power Density AlGaN/GaN HEMTs With Small Gate Length by the Stepper Lithography for Ka-Band Applications

“…Over the past few decades, Steppers, also known as the Step-and-Repeat Lithography System, have been widely adopted for large scale commercial application of III-V semiconductor integrated circuits for its' simple and direct process steps and capability to utilize a fine reticle with less particles [9], [10], [11]. However, for the conventional stepper process, it is difficult to achieve submicron gate lengths to reduce gate resistance, increase cut-off frequency, and switching speed for high frequency applications.…”

Nonlinear electronic transport and device performance of HEMTs

“…Many questions have been raised regarding HEMT performance [1]- [3], and can be answered by our simulations. We base our investigation on the achievements of HEMT performance reported by various foundries, e.g., [4]- [7].…”