Measurement and Identification of Distortion, Alignment, and Mask Errors in IC Processing

Abstract

Measurement and identification of misregistration between patterns in integrated circuits is becoming increasingly important as finer geometry processes are being developed for VLSI. Various forms of the Stickman resistor pattern are described. These enable measurement of the alignment errors, mask errors, and distortions that occur when using any alignment apparatus. The properties of the different forms of Stickman resistors are compared and examples of applications to studying mask making errors, slice/mask distortions, projection distortions, and process induced slice distortions are described. It is shown that misregistrations of 0.1 micron or even less can be measured and identified. Direct measurements on simple apparatus are shown to be reproducible to ±0.003 micron and accuracy is estimated at 5% of the misregistration with simple apparatus and 2% for a one micron misregistration if on chip measurement of sheet resistance is made.

An NMOS test chip for a course in semiconductor parameter measurements

“…A third misregistration test structure designed to measure misregistration between the same two photomask levels as the previous two structures is the Stickman-type structure seen in figure 6c, The structure is a modification of that of Nicholas et at. [15,18] in which the current taps and voltage taps are separated in order to provide a four-terminal or Kelvin measurement of resistance. For this design, a long blocking bar on a second photomask is aligned with a larger rectangle on the first photomask level to form two parallel and narrow resistors of equal size for no misregistration.…”

The Electrical Measurement of Pattern Placement Errors of Mask Makers

“…Rotation can be measured on two devices above each other in the triple stack or adjacent stack. Equation [3] then becomes ~xy = y sin ~ [5]…”