Method for etching tapered vias

Details Method for etching tapered vias Method for etching tapered vias

H - Electricity

01

L

356/151

H01L 21/311 (2006.01) H01L 21/768 (2006.01)

Patent

CA 1315022

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 non- tapered 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 sloping via portion without significantly increasing the diameter of a lower portion of the non-tapered via. This second step is a tapered resist plasma etch operation employing a mixture of oxygen (O2) and CF4. The slope of the upper sloping via portion may be controlled by varying the ratio of oxygen to CF4. In an alternative embodiment, the method produces a "stepped" via having an upper non-tapered portion which extends through the resist and has an opening diameter substantially greater than CD, and a lower non-tapered portion which extends through the oxide and has diameter substantially equal to CD. This embodiment includes an isotropic resist plasma etch operation which enlarges the diameter of the upper via portion extending through the resist, but does not significantly enlarge the lower via portion extending into the oxide layer, followed by an anisotropic oxide plasma etch operation which vertically erodes the lower via portion extending into the oxide layer, and which may also increase the via depth to the desired total depth. Preferably, the PATENT plasma used in the isotropic resist plasma etch step consists primarily of O2 and the plasma used in the subsequent anisotropic oxide plasma etch step consists primarily of CF4.

615413

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