Characterization in Silicon Processing

Optical

Scatterometry*

15

Optical scatterometry involves illuminating a sample with light and measuring the

angular

distribution of light which is scattered. The technique is useful for charac-

terizing the topology of two general categories of surfaces. First, surfaces

that

are

nominally

smooth

can be examined to

yield

the root-mean-squared (rms) rough-

ness and

other

surface statistics. Second, the shapes of structure

(lines)

of peri-

odically

patterned surfaces can be characterized. The intensity of light diffracted

into the various diffraction orders from the periodic structure is indicative of the

shape of the

lines.

If the line shape is