Patent ID: 6312557
Filing Date: 2001-11-06
Classification: H01L

Abstract:
An apparatus for determining the endpoint of a dry etch process when the dry etch process is acting on a substrate comprising a layer of a first material overlying a second material, said apparatus comprising:(a) a source of light of a predetermined wavelength, wherein said wavelength corresponds to a photon energy that is greater than the work function of one of said first and second materials, and less than the work function of the other material, such that only one of said first and second materials photoemits,(b) optical elements that direct, focus, or disperse the light onto the substrate,(c) an electron collector for collecting the photoelectrons emitted by the material that is photoemitting, said stream of electrons constituting a photocurrent,(d) a photocurrent amplifier, and(e) a signal processor for monitoring a temporal series of amplified photocurrent measurements for a change in the amplified photocurrent measurements known to correspond to an endpoint of the dry etch process.