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

Paper PS-WeM3
Surface Chemical Changes of Aluminum During NF3-Based In-Situ Chamber Cleaning: Critical Discharge Parameters

Wednesday, November 6, 2002, 9:00 am, Room C-105

Session: Conductor Etch II
Presenter: X. Li, University of Maryland
Authors: X. Li, University of Maryland
G.S. Oehrlein, University of Maryland
X. Hua, University of Maryland
L. Ling, University of Maryland
E. Karwacki, Air Products
B. Ji, Air Products
Correspondent: Click to Email
During plasma-based in-situ chamber cleaning of deposited dielectric films using NF3, a significant transformation of aluminum into AlF3 can occur. We studied the roles of fluorine atoms and ion bombardment in this process by employing NF3 discharges mixed with He, Ne or Ar. Polished Al 6061 alloy coupons and sputter-deposited Al films were used. Typical process conditions were a pressure of 1 Torr, a total flow rate of 300 sccm, and power levels up to 300 W RF bias power for a 125 mm diam wafer. Aluminum erosion rates and surface chemistry changes, and information on the species that evolve from the surfaces during the process were obtained by real-time ellipsometry and mass spectrometry, respectively. X-ray photoemission spectroscopy characterization of processed Al surfaces was also performed. We find that a complex Al-fluoride layer is produced by the plasma processes. For RF-based discharges employing NF3 a threshold RF power exists below which a thicker reacted Al-fluoride layer is not produced (about 2 W/cm2 for our reactor). When Al is exposed to an NF3 RF discharge above this power level, a thick reacted Al fluoride layer is produced. If instead a He/NF3 discharge is used, the Al surface modifications are minimized at high RF power as long as the NF3 concentration is less than 40%, and an increasingly thicker Al fluoride layer is produced with a greater proportion of NF3 in He/NF3. In addition, we will report RF electrical characterization of NF3/He discharges under these processing conditions, and results of comparative studies using Ne/NF3 and Ar/NF3 discharges, and microwave remote plasma production.