| 摘要 |
A system of at least three alignment key paterns (10, 12) and (14) located within the scribe lines of a semiconductor chip which allow more accurate placement of wafer probes and more accurate location of fuses for the purposes of blowing selected ones of those fuses by means of laser energy. A particular alignment key pattern (12) comprises pairs of lines located symmetrically about a horizontal axis (Yb) and a vertical axis (Xb) in such a way as to generate dual reflection signals (24) when scanned perpendicularly (26) with the laser. The accuracy determination based on the dual signal laser pattern as typified by pattern (24) is insensitive to skewing of the laser scan path (28), (28A) and to variations in the resultant amplitudes (27) of the laser reflection signals due to drift in electronic amplifiers, variation in reflection signals due to drift in electronic amplifiers, variation in reflection coefficients and variation in laser intensity and threshold levels (30), (30a) of sensitivity. |
