R·I·T
Title: ASML Stepper
Semiconductor & Microsystems
Fabrication Laboratory
Revision: B Rev Date: 12/21/2010
RIT SMFL
Page 2 of 11
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Reticle Pre-Alignment Marks
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Reticle Barcode
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Reticle Alignment Marks
4.2
Reticle Bar Code – The reticle barcode is read as the reticle is removed from the reticle
carrier. Reticle bar code information is specified in the stepper job.
4.3
Reticle Pre-Alignment Marks – Two Pre-alignment Marks are located 135.5mm apart near
the corners of the reticle. They are used to pre-align the reticle to the reticle table.
4.4
Reticle Alignment Marks - Two Reticle Alignment Marks, M1 and M2, are located 139mm
apart near the left and right edges of the reticle. After the reticle is pre-aligned on the reticle
table, the Reticle Alignment Marks are aligned to the permanent fiducial marks F1 and F2,
located on the fiducial plate on the wafer table.
4.5
Wafer Zero Level – The ASML Stepper utilizes zero level marks that are patterned and
etched into the wafer before any other steps. An etch depth of 1200A +/- 10% allows the
stepper to recognize the marks. It is possible to pattern the zero level at the same time as the
first level, but overlay accuracy will be reduced since the first level is not aligned to the zero
level. This is because the zero level is defined by a separate reticle.
4.6
Wafer Global Alignment - The wafer alignment marks W1, W2, etc, are exposed on the
zero layer and etched into the wafer. Two of these marks are sufficient but up to 25 may be
used on a single wafer. If more than two marks are used, the stepper will find a best
alignment and expose all die using the same settings. The stepper uses through the lens
alignment of the wafer and the reticle.
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