Browse Prior Art Database

Method for Correcting Elastic Distortions in Membrane Masks

IP.com Disclosure Number: IPCOM000106152D
Original Publication Date: 1993-Oct-01
Included in the Prior Art Database: 2005-Mar-20
Document File: 2 page(s) / 54K

Publishing Venue

IBM

Related People

Guhman, GF: AUTHOR [+2]

Abstract

A method is described for correcting mask distortions caused by pattern- dependent tensile stress in the membrane. The total membrane area is subdivided into small cells and the distorting influence of neighboring cells is numerically predicted by iterative calculation for each cell. Pattern data for a given chip is modified according to the calculations so that mask fabrication includes compensation for the predicted distortion. The result enhances both placement accuracy and overlay accuracy. The method can be applied to materials other than silicon by using the corresponding Young's modulus for all calculations.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 61% of the total text.

Method for Correcting Elastic Distortions in Membrane Masks

      A method is described for correcting mask distortions caused by
pattern- dependent tensile stress in the membrane.  The total
membrane area is subdivided into small cells and the distorting
influence of neighboring cells is numerically predicted by iterative
calculation for each cell.  Pattern data for a given chip is modified
according to the calculations so that mask fabrication includes
compensation for the predicted distortion.  The result enhances both
placement accuracy and overlay accuracy.  The method can be applied
to materials other than silicon by using the corresponding Young's
modulus for all calculations.

      The total membrane area is subdivided into cells no larger than
one square millimeter in area.  Cells may be square, rectangular or
hexagonal.  Each cell is identified by the two indices i and j
according to its location in the patterned area of the mask.  The
array of cells includes a row around the outside edge of the membrane
where the material is thicker.

      For cell (i,j), the fraction f(i,j) of its area that is clear
is determined from the pattern data.  The Young's modulus of the
opaque mask membrane material is denoted by E. Note that the opaque
material may be a composite or layered material such as X-ray masks
made with coatings of polymer and metal on a silicon membrane.  The
effective local modulus is defined as e(i,j) = k*f(i,j)*E.  For
perforated m...