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Browse Prior Art Database

Pellicle Ring (or Frame) Mounted Mask Shields

IP.com Disclosure Number: IPCOM000113581D
Original Publication Date: 1994-Sep-01
Included in the Prior Art Database: 2005-Mar-27
Document File: 4 page(s) / 103K

Publishing Venue

IBM

Related People

Flanders, SD: AUTHOR [+3]

Abstract

Methods for adding light shields to photomasks are described which prevent the imaging of defects in chrome border areas of the photomasks. Shields may be added in four general locations, or in combinations of those locations: 1. Internal to the pellicle ring frame. 2. External to the pellicle ring frame. 3. On the top surface of the photomask. 4. On the backside of the mask substrate.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Pellicle Ring (or Frame) Mounted Mask Shields

      Methods for adding light shields to photomasks are described
which prevent the imaging of defects in chrome border areas of the
photomasks.  Shields may be added in four general locations, or in
combinations of those locations:
  1.  Internal to the pellicle ring frame.
  2.  External to the pellicle ring frame.
  3.  On the top surface of the photomask.
  4.  On the backside of the mask substrate.

Several forms are proposed for the shields which are held in place by
a mounting adhesive.

      Shield Materials - The light shields are made of materials
which are opaque to ultraviolet (UV) exposure energy, stable under
cleaning processes, non-shedding, and free of outgassing.  Typical
shield materials are: metal shim stock, metal foils, and UV-stable
plastic sheets.  The mounting adhesive material is the material
commonly used to mount photomasks.

      Internal Shield Placement - Fig. 1 shows an example of a
pellicle ring frame that has been modified to hold shields internal
to the frame.  A recess in the pellicle ring frame accommodates the
shield and the mounting adhesive used to hold the shield in place.
The shield may be either flat or folded as shown in Fig. 1.  Note
that the shield may be bonded directly to the surface of the mask by
the same type of adhesive that is used to bond the shield to the
pellicle ring frame.  In Fig. 2, a groove, shoulder or shelf can
serve as an alternative to the recess.  Another alternative is t...