Browse Prior Art Database

Charged Beam Deflection Algorithm that Eliminates Thermal Cycling

IP.com Disclosure Number: IPCOM000107825D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 3 page(s) / 107K

Publishing Venue

IBM

Related People

Ho, CT: AUTHOR

Abstract

This article describes a deflection algorithm for charged beam field coverage that provides equi-thermal self-heating of the deflection elements, preventing thermal cycling errors.

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

Charged Beam Deflection Algorithm that Eliminates Thermal Cycling

       This article describes a deflection algorithm for charged
beam field coverage that provides equi-thermal self-heating of the
deflection elements, preventing thermal cycling errors.

      E-beam lithography systems field coverage with stitched
subfield deflection generally have a subfield path in a raster
fashion in which the Y axis increments by one line after an X axis
deflection covers from one side to another. Consequently, the Y axis
experiences a slow thermal cycle in the deflection coil and also in
sensitive elements in the deflection amplifier such as the current
sensing resistor. The thermal cycling of that resistor, which has a
finite thermal coefficient of resistance, causes errors in the
positioning of the charged beam on its target.

      This problem is solved by having unit distance subfield
stepping in both the X and the Y axis simultaneously.  The following
set of rules governs the locus of the deflection so that all
subfields in a rectangular field are covered using unit distance
steps (in either or both axes) without any subfield being omitted or
duplicated.

      Rule 1:  Start from one corner and make unit distance diagonal
steps across the field until one side is reached. Make the next step
along the side that was reached in the same direction as before.  The
next step is to make another 45-degree turn so that the path moves in
the same direction in the axis which is longer, but in the reversed
direction in the axis which is shorter (see Fig. 1).

      Rule 2:  In the case when a corner is reached, as shown in Fig.
2, follow the path as shown.  This is a double application of Rule 1
in mid-sequence.

      By repeatedly applying rules 1 and 2, the entire field can be
covered without omission or duplication as long as the field is
rectangula...