A study of the ultra-short T-shaped gate profile controlled by the sensitivity difference in bilayer resists

• Published in: Microelectronic engineering Vol. 226; p. 111283
• Main Authors: Xie, Yuying, Zhu, Mingsai, Deng, Jianan, Chen, Yifang
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier B.V 01.04.2020; Elsevier BV
• Subjects: High electron mobility transistor; High electron mobility transistors; Indium gallium arsenides; Minimum foot width; Mobility; Parameter sensitivity; Proximity effect (electricity); Semiconductor devices; Sensitivity; Sensitivity difference; Sensors; Shrinkage; T shape; T-shaped profile; Transistors; Sensitivity difference; High electron mobility transistor; T-shaped profile; Minimum foot width
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2020.111283

InP based InGaAs/InAlAs high electron mobility transistors (HEMTs) are advancing toward upper terahertz (THz) frequency beyond 500 GHz, driven by the constant shrinkage of the foot width in T-shaped gates. However, when the foot width is reduced to 30 nm, the dc and/or rf performance of HEMTs is strongly related to the foot profile of the T-shaped gates. Conventional method is to utilize proximity effect correction (PEC) to control the gate profile within a specific bilayer. To obtain the optimized bilayer for the desired T-shaped profiles, another parameter, that is the sensitivity ratio of the top layer over the bottom one should play the decisive role, which has never been addressed so far. This work focuses on the control of T-shaped gate profile by utilizing the difference in the sensitivities between the bottom and the top layer both theoretically and experimentally. The minimum foot width achievable for a particular bilayer is worked out in almost the whole range of the sensitivity ratio from 3:1 to 37:1. By accurately controlling the influence of sensitivity ratio on the profile of T-shaped gate and the minimum foot width, the specific gate structure desired can be precisely prepared to meet the performance requirements of the device. [Display omitted] •The results show that the bilayer resist profile and the minimum foot width can be effectively influenced by the ratio.•This work is very important to enable us to achieve the desired T-shaped profile for reducing the parasitic capacitance.•Indicate the minimum foot width that can be achieved due to different sensitivity ratios in the bilayer resist system.