Profile

• One of the most important characteristics of etch is the etch profile, which affects the next deposition process.

• Etch profile normally is measured by a scanning electron microscope (SEM).

• A perfect vertical profile is the preferred profile, since it can transfer the mask images from the photoresist to the underneath film without loss of critical dimension.

• An isotropic tapered profile is good for contact or via etch because the tapered contact and via hole has a larger arriving angle and is easier for the next tungsten chemical vapor deposition process to fill the via without any voids.

• Undercut profiles are caused by too many chemical etch components in the Reactive Ion Etch process or excessive ion scattering to the sidewall.

Fig. 2 Etch profiles (a) purely isotropic etch. (b) Isotropic etch with a compensated mask, (c) anisotropic etch with no horizontal components, (d) isotropic etch with overetch and, (e) isotropic etch with isotropic etching of the mask. [2]