DC to 85GHz TWA and Ka-band 4.9W Power Amplifier Using an Optical Lithography Based Low Cost PHEMT Process

Abstract

An optical photo lithography based 0.15μm GaAs PHEMT process and 2mil-substrate technology that enables high production throughput and low cost is described. The developed process achieved Imax=575mA/mm, BVgd=14V, and 753mW/mm of output power density at P-1 condition at 18GHz. Design and test results for DC to 85GHz traveling wave amplifier (TWA) and 29-30.5GHz 4.9W power amplifier (PA) are also described as process capability verification. TWA shows 8dB of small-signal gain and 12dBm of output power up to 85GHz frequency. PA shows 20dB of small-signal gain and 36.9dBm of output power at 3dB gain compression condition in between 29 and 30.5GHz frequencies. These results verify the process capability to manufacture MMIC devices for applications up to 90GHz.

Low-cost, high performance mm-wave MMICs are crucial to the development of mm-wave radio links, automotive radars, and test equipments, as the market for these applications mature. For mm-wave MMIC device production with gate length of 0.15μm or shorter, the industry standard technology is direct-write electron-beam lithography. However, the direct e-beam process has a technical bottleneck to reduce wafer cost due to the slow wafer processing time. To solve this problem, Avago developed a 248 nm deep-UV optical stepper based, high throughput 6” 0.15μm pHEMT process. Except for the gate processing, this process is similar to Avago’s 6”, 0.5μm gate pHEMT process that has shipped 6000-wafers/year primarily for cell phone and wireless LAN applications. The goal is to reduce the mm-wave MMIC wafer cost for emerging consumer mmwave applications.

In this paper, Avago’s newly developed 0.15μm low cost 6” GaAs MMIC production process will be described. To evaluate the process capability for mm-wave applications, a DC to 85GHz traveling amplifier (TWA), and a 28-30.5GHz 4.9W power amplifier (PA) were designed, fabricated, and tested. The TWA shows 8dB of minimum gain and 14dBm output power up to 85GHz frequency range. 4.9W PA shows 20dB of small-signal gain and 36.9dBm of output power in between 29GHz and 30.5GHz frequencies.