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CARL ALMGREN, JIM EVANS & RANDY HECKMAN, Advanced Energy Industries, Inc., Fort Collins, CO, USA

ABSTRACT

Plasma-based processes are critical to the fabrication of semiconductor device structures and to the integrity of CDs. PVD, HD-PCVD, PECVD, dry etch, and strip all rely on dc and RF sources to ignite and maintain the energy of the plasma to do work. To date, control of power has been regulated on the output of the generator (i.e. forward power), rather than the input of the plasma (i.e. delivered power). There are numerous historical and technical reasons why this has been the case, but the net effect is that the power output of the generators (sources) is never the power input to the plasma. Most power losses are accounted for in the match network between the generator and the plasma. Additionally, dynamic changes in the impedance of the plasma contribute to variations in delivered power. There are multiple methodologies available to deliver power to the plasma, using fixed match, switch match, auto-selectable switch match, and sweep frequency. Further, these methods are very amenable to point-of-use delivered power control. This paper focuses on the benefits to be derived from two of these methods: fixed match and closed-loop delivered power control.