TiWN Thin Film Resistor Process Control

J.W.Crites and M.J.Drinkwine

Cobham DES, Roanoke, 5310 Valley Park Drive, Roanoke, VA 24019 Phone: (540) 563-8600, E-mail: james.crites@cobhamdes.com

Keywords: TiWN, TFR, Metal, Sputter, Deposition

ABSTRACT

Thin film properties and temperature stability of titanium-tungsten nitride (TiWN) sputter-deposited films have been investigated as they apply to the manufacture of both thin film resistors (TFR) and Schottky contacts to GaAs for MSAGTM MMICs [1,2]. The TiWN film is reactively sputtered [3] from a Ti10W90 (by weight) target in a nitrogen atmosphere with argon as a diluent gas. The partial pressure of nitrogen, the deposition time and the deposition power are used as the key control parameters to maintain the target sheet resistance (Rsh) and other film characteristics. One critical aspect of the process is that the final TFR Rsh value is not obtained until after a high temperature implant-activation anneal that occurs with the TiWN in place.

This paper examines difficulties experienced with process control as a consequence of the process constraints and the equipment set in use. Of particular note, throttle-valve control in the sputter system was found to be deficient and therefore it was upgraded to achieve the desired process control. The paper includes data relating the partial pressure of nitrogen to both the as-deposited and the post-annealed TFR Rsh values. A discussion of the influence of deposition pressure on film stress and a summary of process control methods and considerations relating to process targeting and film stability is also presented.

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