Flare impact on the intrafield CD control for sub-0.25-μm patterning

AttPSM CD control: mask bias and flare effects

“…I wafer for dipole illumination is larger than that for annular illumination because dipole can capture a greater fraction of 1 st order beams. (equation 14), and 15)) This explains why dipole illumination shows smaller MEEF. As to the mask bias, the bias dependency can be explained with the duty ratio, s/p.…”

Measuring and modeling flare in optical lithography

“…The y-intercept of the linear portion of the curve can be thought of as the short range contribution to the total flare. Flare is also a function of field position, with points in the center of the field often experiencing flare levels 50% higher than points near the edge of the field [3]. This phenomenon may be thought of as a side effect of the long range versus short range scattering discussed above.…”

“…Luce performed a test varying the pad size [3], showing flare increasing from 6.8% for a 400µm pad, to 7% for a 10µm pad, to about 7.5% for a 5µm pad, and finally to 8% for a 2µm pad (corresponding to k 1 = 4.5 on the stepper used). Since the last data point should show some diffraction effects confounding the flare measurements, one could conclude that flare contributed from an area farther away than ±200µm amounted to 6.8%, while the shorter range flare coming from an area of 400X400µm 2 around the feature contributed another 1% approximately ( Figure 4).…”

“…In this section, we'll review a number of proposals for measuring this short range flare [2][3][4][5][6][7]. Besides the framing blade test described above, one obvious approach would be to vary the size of the flare pad and to look for any variation of the measured flare.…”

“…Varying measured flare with pad size shows the presence of some amount of short range flare (from Ref[3]). …”