Plasma etching process considerations

C. Parameter Control At present, the most serious impediment to routine use of plasma etching is the large number of parameters that affect the process. As noted, both gas phase considerations and plasma-surface interactions must be controlled. The problem is illustrated in Figure 7 32). Naturally, if the basic plasma parameters (A, /(e), r) could be con-... 

As an example of the latter point, several process and tool innovations have contributed to both the generation of smaller device patterns and the ability to maintain the integrity of those dimensions through the subsequent process steps. Thus, improved exposure tools (e.g., optical step and repeat, E-Beam) and masking materials (resist) allow considerably smaller pattern definitions than was previously possible. Once generated, these patterns can now be maintained with improved pattern etching techniques (reactive ion or plasma etching). 

One important area of resist research in recent years is the development of plasma-developable resist systems. The aim of plasma developable resists is to use nonsolvent, all dry development methods to avoid the problems of swelling and consequent resolution limitation associated with conventional resists. Much of the semiconductor fabrication process now utilizes plasma techniques as they are capable of providing high resolution images. An important consideration in this is that the plasma-developable resist images should stand up well to the plasma etching treatments. 

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