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New End-Point Technique for Reactive Ion Etching of Silicon Trench

IP.com Disclosure Number: IPCOM000100064D
Original Publication Date: 1990-Mar-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 1 page(s) / 60K

Publishing Venue

IBM

Related People

Lee, YH: AUTHOR [+2]

Abstract

This article discloses a technique to monitor reactive ion etching process by counting total positive ions accumulated at a miniature Faraday cup. A large negative bias voltage at the cup ensures counting only a positive charge and repelling all the negative charges. This is essential to make the new technique reliable due to the ambipolar diffusion in plasmas.

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New End-Point Technique for Reactive Ion Etching of Silicon Trench

       This article discloses a technique to monitor reactive
ion etching process by counting total positive ions accumulated at a
miniature Faraday cup.  A large negative bias voltage at the cup
ensures counting only a positive charge and repelling all the
negative charges.  This is essential to make the new technique
reliable due to the ambipolar diffusion in plasmas.

      Etch rates are generally proportional to a positive ion current
in reactive ion etching and an etch depth has one-to-one
correspondence to total number of ions irradiated on the film being
etched, regardless of any variation in plasma parameters.  Thus, a
charge counting can be used as a reliable process monitor,
particularly when an etch rate varies with time and a simple timing
often yields a large fluctuation in thickness of etched films.  One
specific application is a reactive ion etching process for silicon
deep trench which requires that etching stop in the middle of the
silicon substrate.  There is no viable technique to monitor a trench
depth in any non-destructive mean and the ion fluence measurement
will increase the repeatability, especially in the manufacturing
environment.  One minor drawback of total ion counting is the fact
that reactive ion etching also involves the isotropic etching of a
chemical nature which has no direct relation to the ion current.
Fortunately, most etch processes for a sub-micron fea...