Prev: 3.1.6 Oxidation

3.2 Basic Etching and Deposition Processes

In contrast to complex PVD or CVD processes where the local deposition rates strongly vary and have to be calculated separately for each surface cell, isotropic, anisotropic, and unidirectional deposition processes work with uniform deposition rates. Similarly, the rates for the corresponding etching processes only depend on the etchant-material combination and are homogeneous for each material. For this reason the processes can be modeled by applying a structuring element with fixed shape and orientation, keeping the basic operation of moving the element along the surface and marking the cells hit by the structuring element (see Section 2.2). For deposition processes even the size of the structuring element can be kept constant, whereas it has to be adapted to the different materials for etching processes.

The morphological operations used to model these different etching and deposition steps are not any longer pure geometrical emulations but a phenomenological representation of the underlying physical principles. If the etching rate is uniform for all directions, a spherical structuring element is appropriate.

This section shows how the morphological principle of the structuring element (see Fig. 2.1 in Section 2.2) is extended to varying shapes of the elements in order to model isotropic (Section 3.2.1), anisotropic (Section 3.2.2), and unidirectional (Section 3.2.3) etching and deposition processes. The basic etching and deposition steps introduced in this section complete the set of solid modeling tools which allow the generation of a variety of device and interconnect structures. Complex examples will be shown later, when solid modeling is finally completed with the functionality for the inclusion of layout information.

Prev: 3.1.6 Oxidation