METHOD and APPARATUS for EFFICIENT ENCODING of START/STOP or START/DURATION NUMERICAL CONTROL DATA
Original Publication Date: 1989-Feb-01
Included in the Prior Art Database: 2005-Jan-27
This article suggests a means to reduce the number of bits required to transmit X start/stop or X start/displacement data for numerically controlled (N/C) tools. It is proposed to code X start and W X values needed to specify a rectangle in such a way that one less bit is needed per (X,W X) pair. The extra bit is helpful in keeping N/C data on fixed data boundaries. In N/C tools used in semiconductor operations, such as an E-beam lithography tool, it may be necessary to specify in some coordinate system a start and stop point, or a start point and displacement in one or more dimensions. For instance, a rectangle to be exposed (Fig. 1) will be expressed in terms of X,W X and Y,W Y. Each coordinate axis will generally be addressed by an n-bit code, providing 2n addressable points along the axis (0, 1, 2, ....2n -1).