AVS 45th International Symposium
    Plasma Science and Technology Division Monday Sessions
       Session PS-MoP

Paper PS-MoP3
Plasma Damage in Metal Etch Processes Using an Oxide Hardmask

Monday, November 2, 1998, 5:30 pm, Room Hall A

Session: Plasma Science and Technology Poster Session
Presenter: J.I. Colonell, Bell Laboratories, Lucent Technologies
Authors: J.I. Colonell, Bell Laboratories, Lucent Technologies
N.A. Ciampa, Bell Laboratories, Lucent Technologies
M.V. Malyshev, Princeton University
V.M. Donnelly, Bell Laboratories, Lucent Technologies
J.T.C. Lee, Bell Laboratories, Lucent Technologies
C.P. Chang, Bell Laboratories, Lucent Technologies
K.P. Cheung, Bell Laboratories, Lucent Technologies
W.Y.C. Lai, Bell Laboratories, Lucent Technologies
C.T. Liu, Bell Laboratories, Lucent Technologies
C.S. Pai, Bell Laboratories, Lucent Technologies
H.M. Vaidya, Bell Laboratories, Lucent Technologies
Correspondent: Click to Email
Plasma damage in metal etch remains a serious problem in ULSI fabrication, and is expected to become more severe as gate oxide thickness is scaled. One proposed solution is to use an oxide hardmask, rather than a photoresist mask, to pattern the metal. Metal to oxide etch selectivities of 8:1 are achievable, so the mask thickness can be reduced from 1 µm to 1500 Å, thus reducing the aspect ratio for 0.4 µm spaces from ~4 to ~2 or lower. This change should reduce damage by reducing electron shading and aspect ratio dependent etching. However, metal etch processes using hardmask generally require low pressure conditions (2 to 5 mTorr, compared to 10 to 20 mTorr for a typical photoresist process) which lead to higher plasma densities and electron temperatures. We have measured plasma damage due to metal etch in a commercial, high density, inductively coupled reactor on 0.25 µm technology CMOS capacitor and transistor testers, with oxide thicknesses from 50 Å down to 25 Å. The effect of source power (from 300 W to 600W) and process pressure (3 mTorr to 7 mTorr) on the damage will also be discussed.