The use of organosilicon polymers in multilayer plasma resist processing

Abstract

The unique resistance of organosilicon polymers to oxygen plasmas has led to their widespread use in multilayer resist processing. A study of their etching properties shows a correlation between their structure and etching characteristics. Often, these characteristics are obtained by means of laser interferometric techniques. Using a model of this laser signal we have identified various processes which combine to form an oxygen plasma resistant layer atop these organosilicon polymers. In particular, we have discovered that the etching characteristics of these polymers is relatively independent of the specific structure. Rather, the silicon content of these polymers plays the dominant role in providing resistance to these plasmas. For polymers having a high silicon content, the laser signal is regular and sinusoidal; for lower concentrations (<10%), the laser signal shows irregularities which can be explained by means of the model. From an analysis of these laser traces and a comparison to the model, we show that the process of formation of a resistant “oxide” layer is dependent upon the temperature during etching and that other organometallic polymers show a similar behaviour.