a standardized sample for scatterometry includes four quadrants each including an inner block surrounded by four outer blocks . a pattern of gratings is repeated within each of the blocks using different resolutions and orientations . each grating within an outer block has a matching grating within the block &# 39 ; s pair . a grating and its matching grating are negative images of each other — the pitch and line - size of a grating are equal , respectively to the line size and pitch of the matching grating . the inner block also includes a series of background patterns positioned behind the gratings . these patterns include repeating patterns of hole and repeating line structures . this series of structures cover a large die area , helping to simulate the conditions faced by real - world scatterometers . the various structures feature a high - degree of alignment , allowing rapid verification using sem or other techniques .