METHOD OF SELECTIVELY ETCHING OPENINGS IN A MATERIAL OF VARIABLE THICKNESS

摘要

The method includes a first etch step in which a material (14) having variable thickness and being deposited on a substrate of a different material (12) is isotropically etched through a mask having at least one opening (18, 20), the detection of the initial end point at which a portion of said material (14) is completely eched away at some location, and a second etch step in which the remainder of said given material (14) is anisotropically etched until it has been completely removed from all etch locations.
Preferably the etching is by dry plasma etching and the first end point is detected by monitoring the change in concentration of a reactive species. The change is sharply defined by taking a second derivative of the curve of the change in intensity of the peak of the sensed species.
The openings etched into said material (14) by using the inventive method have curved walls and the bottom part of the walls is exactly in vertical alignment with the corresponding openings (18, 20) in the etch mask.