Stable plasma process for etching of films

Abstract

In accordance with the present invention, process parameters are controlled to provide a stable etch plasma. We have discovered that it is possible to operate a stable plasma with a portion of the power deposited to the plasma being a capacitive contribution and a portion of the power deposited being an inductive contribution. In particular, a stable plasma may be obtained within two process regions. In the first region, the gradient of the capacitive power to the power applied to the inductively coupled source for plasma generation &lsqb;&part;P /&part;P &rsqb; is greater than 0. In the second region, plasma stability is controlled so that &lsqb;&part;P /&part;P &rsqb; is less than 0 and so that P <<P . Typically, the magnitude of P is less than about 10% of the magnitude of P . In addition, in a plasma processing apparatus having a dual power control, at a given application of power to the plasma generation source, the stability of the plasma is extended by increasing the pressure in the etch process chamber. This enables operation of the etch process using lower power application for plasma generation. The stable plasma operating regime is overlaid upon other process parameters to obtain the desired etch results, to provide a reliable manufacturing process. Operation of the etch process in a stable plasma region enables use of a timed etch end point. For example, during etching of a silicon-containing layer, it is possible to use an etchant plasma which provides rapid etching and etch selectivity relative to adjacent layers during a first, timed etch portion of the etch process, and a different etchant plasma during a final emissions monitored etching to an underlying substrate interface. In addition, the stable plasma assists in the etching of doped and undoped silicon and polysilicon substrates at substantially the same rate, while providing for a clean etch process.