Pattern Transfer Using The Etching Technique

• The layer is first blanket deposited; then the patterned resist is formed and the layer is etched using the resist as a mask.

• If the etching process attacks the layer surface equally in all directions, the etch is said to be isotropic.

• For feature line widths and line spaces significantly larger than the feature height, isotropic etching presents only a minor problem.

• For VLSI devices, in which feature heights have comparable dimensions to feature line widths and spaces, mask compensation to account for isotropic etching is impossible. For this reason plasma etch techniques, which are capable of anisotropic etching, are so important to VLSI. [5]

• The degree of anisotropy of an etch process can be expressed as

A = 1 – V_h/V_v

Where A is the degree of anisotropy, V_h is the horizontal etch rate and V_v is the vertical etch rate. [2]

• Isotropic etching is represented by A=0 and anisotropic etching by A=1. [2]

Fig. 5 Shows the deposit/resist/etch/strip sequence of etching. [2]