Comparison of Single-Step and Two-Step EBL T-Gates Fabrication Techniques for InP-Based HEMT

• Published in: Chinese Journal of Electronics 2016-03, Vol.25 (2), p.199-202
• Main Authors: Zhong, Yinghui, Zang, Huaping, Sun, Shuxiang, Wang, Haili, Li, Kaikai, Li, Xinjian, Ding, Peng, Jin, Zhi
• Format: Article
• Language: English
• Subjects: EBL technique; gate‐foot; gate‐head; geometry path; HEMT; HEMTs; high electron mobility transistors; III‐V semiconductors; indium compounds; InP; Polymethylmethacrylate (PMMA); single‐step electron beam lithography methods; size 196 nm; Twostep EBL technique; two‐step EBL T‐gates fabrication techniques; T‐Gate; wide band gap semiconductors
• ISSN: 1022-4653; 2075-5597
• DOI: 10.1049/cje.2016.03.001

T-Gate fabrication processes for InP-based High electron mobility transistors (HEMTs) are described using PMMA/Al/UVIII. The single-step and two-step Electron beam lithography (EBL) methods are proposed contrastively without dielectric support layer. The optimal gate-foot length is 196nm for 50nm geometry path by single-step EBL technique. Since the gate-foot and gate-head are defined independently, the two-step EBL process minimizes forward scattering and enables smaller gate-foot length, which improves to be 141nm for 50nm geometry path and also 88nm for 30nm geometry path. Both EBL methods have been incorporated into InPbased HEMTs fabrication. With the gate-foot length decreases from 196nm to 141nm, the current-gain cutoff frequency ( fT) is improved from 125GHz to 164GHz, and also the maximum oscillation frequency (fmax) increases from 305GHz to 375GHz.