TOSHIBA
在獲得美國版權後開始推出focus
measurement technology 2004年1月8日
TOSHIBA
在獲得美國版權後開始推出focus
measurement technology，據稱準確度可達百份之九十。這個美國版權的編號是United
States Patent 6,674,511，簡介如下：
An evaluation mask for evaluating a projection-type exposure
apparatus, the mask including at least one diffraction grating
pattern for producing a diffracted light of the positive
first-order and a diffracted light of negative first-order,
diffraction efficiencies of the diffracted lights being
different respectively, one of the diffracted lights having a
magnitude that is zero, and an image of the at least one
diffraction grating pattern being projected onto a test
substrate by the projection-type exposure apparatus, and a
reference pattern for obtaining a reference image to measure a
displacement of the image of the diffraction grating pattern,
and an image of the reference pattern being projected onto the
test substrate or the image detector by the projection-type
exposure apparatus, wherein the images of the diffraction
grating pattern and the reference pattern projected onto the
test substrate or the image detector are used for evaluating the
projection-type exposure apparatus.
United States Patent 6,674,511的詳情可參閱：
http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=/netahtml/search-adv.htm&r=2&p=1&f=G&l=50&d=ptxt&S1=photomask&OS=photomask&RS=photomask
