Patent ID: 8057971

Claim:
A method of forming a three-dimensional latent image with good depth and shape control in a resist layer applied over a workpiece surface, the method including: using in the resist layer a positive resist with an effective absorption characteristic that produces a log-linear relationship between exposure energy (E) and the depth of exposure (D), approximated to a first order by D=c 1 ln(E)+c 2 , wherein c 1 and c 2 are curve fitting constants for the positive resist, rather than a linear relationship; converting a relief map that represents a three-dimensional surface into point-by-point exposure doses calculated to reach an exposure threshold of the positive resist at a plurality of controlled depths within the resist layer, taking into account the log-linear relationship, producing an exposure map; and patterning the resist layer to form a three-dimensional latent image using a pattern generator that varies effective exposure doses on a point-by-point basis using the exposure map.