AVS 49th International Symposium
    Plasma Science Wednesday Sessions
       Session PS-WeM

Paper PS-WeM7
Advanced Metal Gate Etch with 193nm Lithography in a Silicon Decoupled Plasma Source Etcher (DPSII)

Wednesday, November 6, 2002, 10:20 am, Room C-105

Session: Conductor Etch II
Presenter: D. Yan, Applied Materials
Authors: D. Yan, Applied Materials
M. Shen, Applied Materials
D. Shashank, Applied Materials
T. Chowdhury, Cypress Semiconductor
C. Yang, Cypress Semiconductor
Correspondent: Click to Email
193nm lithography is becoming increasingly important as the critical dimensions of semiconductor devices continue to scale down towards sub-0.10um. From dry etching perspective, however, 193nm resist brings new challenges due to its poorer plasma etch resistance, line edge roughness and lower thickness compared to 248nm DUV resist. Consequently, issues such as line edge roughness and poor profile control were observed after dry etch processing using etch processes developed for 248nm resist. This paper presents a successful development of advanced 0.1mm metal gate application using 193nm lithography on Applied Materials’ decoupled plasma etcher (DPSII). The integrated process involves a hard mask open with ex-situ resist strip followed by metal/poly dual gate etching. Process chemistry and process parameters for nitride mask step were thoroughly investigated. With CF4/CHF3 based chemistry, the process achieved high nitride to resist selectivity with straight nitride profile and smooth sidewall. Less than 7nm 3-sigma of CD bias uniformity was obtained across the wafer with edge exclusion up to 4mm on a 200mm substrate. Process parameters such as pressure, gas ratio and the total fluorine-containing flow were shown to be the most influential on resist selectivity, profile and CD control. A careful balance of these parameters needs to be maintained in order to deliver an overall process. The subsequent W/WN/poly gate etch features a three-step approach that has produced straight profiles, excellent CD control and excellent gate oxide integrity. Post-etch measurement of line edge roughness shows comparable performance to that obtained on 248nm resist. Bright field ultra sensitive defect monitoring on product wafers showed comparable performance to previous 248nm resist poly gate process. Process trends and proposed mechanisms are addressed in detail in the paper.