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3.1.5 Stripping

Stripping of a material is again a process step with a strong physical background. It emulates an etching step with such a high selectivity that only one specific material is removed and corresponds to the chemical etching of resist, oxide, and nitride masks. For oxide and nitride hard masks and most recently developed complex polymer resists for high resolution lithography, selective removing of the masks without attack of the underlying layers requires complex chemistries, dry etch processes or combinations thereof. However, within the framework of geometry editing, all these complications are neglected. The final result, namely, that the selected mask material is stripped without modifying the other layers can be achieved with a simple and fast procedure.

Figure 3.6: Stripping of a selected material.

Fig. 3.6 shows how the material represented by the light grey color in Fig. 3.5 has been selectively removed. In principle and comparable with wafer processing in manufacturing, stripping works for complete material layers. Optionally, the solid modeling tool allows ``patterned'' stripping with the same geometric primitives as introduced for the mask operations in Section 3.1.2. In this way, the structure from Fig. 3.6 could be obtained without inversion of the pattern from Fig. 3.3 by applying a blanket layer of the second material and locally selective stripping of four circles and one rectangle.

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