Method for etching tapered vias

Abstract From the Canadian patent

PATENT, Abstract of the Disclosure, A multi-step plasma etch method for etching a tapered via having uniform bottom diameter ("CD") and extending through the resist and into the oxide layer of a coated semiconductor substrate, and a coated semiconductor substrate whose coating has been plasma etched to define such a tapered via. The first step of the inventive method is an anisotropic oxide plasma etch operation, preferably employing a plasma consisting primarily of CF4, which produces a nontapered via having diameter substantially equal to CD and extending through the resist and into the oxide layer. A preferred embodiment of the inventive method includes a second step defining an upper …