Accession Number : ADA616096


Title :   Subtractive Plasma-Assisted-Etch Process for Developing High Performance Nanocrystalline Zinc-Oxide Thin-Film-Transistors


Descriptive Note : Master's thesis


Corporate Author : AIR FORCE INSTITUTE OF TECHNOLOGY WRIGHT-PATTERSON AFB OH GRADUATE SCHOOL OF ENGINEERING AND MANAGEMENT


Personal Author(s) : Donigan, Thomas M


Full Text : https://apps.dtic.mil/dtic/tr/fulltext/u2/a616096.pdf


Report Date : 26 Mar 2015


Pagination or Media Count : 151


Abstract : Thin-Film-Transistors (TFTs) employing undoped zinc-oxide (ZnO) thin-films are currently being investigated by the Air Force for microwave switching applications. Since the on-resistance (R(on)) of the device scales with channel length (LC), ZnO TFT optimization should be focused on reducing LC, therefore minimizing the associated insertion losses. In this research, deep sub-micron scaling of ZnO TFTs was undertaken using a subtractive reactive-ion-etch (RIE) process. Under optimum processing conditions, ZnO TFTs with LC as small as 155 nm were successfully demonstrated. The active ZnO channels of the TFTs were patterned by selective SF6-RIE of a tungsten ohmic film through electron-beam defined openings in a polymethyl-methacrylate (PMMA) based resist. Through electrical testing, the width normalized R(on) of ZnO TFTs with 155 nm channels was extracted as 3.6 omega dot mm and the devices were found to operate at drain current densities and transconductance values of 830 mA/mm and 121 mS/mm, respectively. Additionally, a total width-normalized source and drain parasitic resistance of 2.1 omega dot mm was observed using a gated transfer length method (TLM), indicating the tungsten-ZnO interface is low resistance. This demonstration of high performance and low R(on) suggests the potential for ZnO TFTs in switching and microwave power applications.


Descriptors :   *THIN FILMS , *TRANSISTORS , *ZINC OXIDES , AIR FORCE RESEARCH , ELECTRON BEAMS , INSERTION LOSS , NANOCRYSTALS , RADIOFREQUENCY POWER , THESES , TRANSCONDUCTANCE


Subject Categories : Electrical and Electronic Equipment


Distribution Statement : APPROVED FOR PUBLIC RELEASE