AVS 45th International Symposium
    Thin Films Division Wednesday Sessions
       Session TF-WeM

Paper TF-WeM9
The Effect of Sputter Process and Target Pass-Through Flux on Sputter Deposition of Co Thin Film for Cobalt Silicide Metallization

Wednesday, November 4, 1998, 11:00 am, Room 310

Session: ULSI Metalization and Interconnects
Presenter: H. Zhang, Tosoh SMD, Inc.
Authors: H. Zhang, Tosoh SMD, Inc.
J. Poole, Tosoh SMD, Inc.
R. Eller, Tosoh SMD, Inc.
M. Keefe, Tosoh SMD, Inc.
Correspondent: Click to Email
CoSi@sub 2@ is considered an alternative to TiSi@sub 2@ for use as a contact in ULSI due to its low resistivity, excellent chemical stability and lower formation temperature. Sputter deposition of Co thin film is one of the crucial steps in salicide (self-aligned silicide) process. One major problem with sputter deposition of Co thin film, however, is that Co is a ferromagnetic material, which can be difficult to sputter. Magnetic field strength has been found to be the key parameter in sputtering magnetic films. In magnetron sputtering of Co, high magnetic field strength can be obtained by using a high pass-through flux (PTF) target that allows maximum magnetic flux from the magnets to permeate through the magnets. A high PTF target also allows efficient sputtering and uniform target erosion. The effects of target PTF and sputtering process parameters such as Ar pressure, sputtering power, target to substrate spacing and substrate temperature on the sputter process and film properties were studied. Co targets with PTF of 65% (high PTF), 55% (medium PFT) and 35% (low PTF) were sputtered. Co thin films ranging from 16 nm to 500 nm in thickness were deposited on 200 mm (100) Si wafers. Sputter deposition rate, I-V characteristics, film sheet resistance and film uniformity was measured under various sputter conditions. It is indicated that the I-V characteristics of different PFT targets followed the normal I=KV* relationship of DC planar magnetron sputtering. The exponents in the equation, n, increased with increasing target PTF, indicating the higher the PTF, the lower the impedance. The target having the highest PFT demonstrated the best film uniformity. Rapid thermal processing was carried out to form cobalt silicides at temperatures between 300°C to 850°C in Ar ambient for various times. The sheet resistance of the Co and cobalt silicide films was monitored by four-point probe before and after the RTP. Phases and microstructure of the films were characterized using XRD, SEM and SIMS. The sheet resistance decreased significantly after annealing at 600°C and 700°C due to formation of CoSi@sub 2@, which has lower resistivity. The significant increase in sheet resistance after annealing at 400°C and 500°C was attributed to formation of CoSi phase. For the 16 nm thick Co film, sheet resistance of 3.2 @OMEGA@/sq was obtained after RTP at 600°C and 700°C.