1 August 1989 Electron-Beam Written Multilevel Resist Process Applied To GaAs FET Gate Fabrication
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Abstract
Quarter-micron GaAs FET gate lithography is feasible with high throughput using a 0.25 micron electron beam system and a high sensitivity negative e-beam resist recently introduced by Shipley. The multilevel resist process described here has been used to fabricate microwave MODFETs with 280 mW/mm output power and 6 dB gain at 40 GHz, and microwave ICs with typical MESFET performance of 420 mW/mm output power and 6 dB gain at 18 GHz. Advantages of the described process are: 1) Good linewidth control with a 0.25 micron beam; 0.25 +/- 0.05 microns is routinely achieved based upon SEM photos and electrical measurements. 2) Only one evaporation step is required prior to gate metal deposition; a thin layer of evaporated gold eliminates charging during the e-beam writing and also serves as a plating base for a plated transfer layer. 3) The transfer layer is made of low stress plated nickel, which has very low dry etch rates in chlorine and fluorine based plasmas. This provides good linewidth control throughout gate processing. 4) The material used for the planarizing layer can be selected depending upon the application; PMGI, PMMA and cured novolac resist have been evaluated.
© (1989) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Lawrence G. Studebaker, "Electron-Beam Written Multilevel Resist Process Applied To GaAs FET Gate Fabrication", Proc. SPIE 1089, Electron-Beam, X-Ray, and Ion-Beam Technology: Submicrometer Lithographies VIII, (1 August 1989); doi: 10.1117/12.968520; https://doi.org/10.1117/12.968520
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