Microelectronic Engineering 67–68 (2003) 104–108 www.elsevier.com / locate / mee Bilayer process for T-gates and G-gates using 100-kV e-beam lithography a ,1 b, a * L.E. Ocola , D.M. Tennant , P.D. Ye a Agere Systems, Murray Hill, NJ 07974, USA b Lucent Technologies, Murray Hill, NJ 07974, USA Abstract This paper describes the use of a unique combination of an environmentally stable chemically amplified photoresist (UV113, Shipley) and a copolymer of methyl styrene and chloromethyl acrylate P(MS / CMA) resist (ZEP520, Zeon), without any additional intermediate layers, in the fabrication of high-resolution T-gates and G-gates. The two resists used are innocuous to each other during the designed process flow, providing flexibility, high resolution, greater throughput and ease of use.  2003 Elsevier Science B.V. All rights reserved. Keywords: T-gate; Bilayer; Resist; E-beam lithography 1. Introduction The needs for faster and higher performance transistors are the driving force behind the development of special geometry compound semiconductor field effect transistors (FETs) and high electron mobility transistors (HEMTs). It is well known that short gate length and low gate resistance are essential for the high frequency operation of these transistors. One common method to reduce the parasitic gate resistance is to increase the cross-sectional area of the gate by adding material on the top of the gate while maintaining a short foot region that defines the gate length. This leads to a ‘T’- or ‘G’-gate geometry. Various multi-layer resists have been used in the past for the e-beam lithographic formation of T-gate structures to enhance transistor performance. A common difficulty in designing these schemes is that the polymers share similar polymer structure and are therefore affected by the casting solvents, that may cause intermixing, or by the developers which cause unwanted erosion. These effects make it *Corresponding author. E-mail address: dmt@lucent.com (D.M. Tennant). 1 Present address: Argonne National Laboratory, Argonne, IL 60439, USA. 0167-9317 / 03 / $ – see front matter  2003 Elsevier Science B.V. All rights reserved. doi:10.1016 / S0167-9317(03)00168-0