As geometries of the electronic devices shrink, lithography and patterning for electronic device designs become more challenging. Typically, a deep ultraviolet (DUV) immersion lithography is used to enhance the photolithography resolution to manufacture integrated circuits (ICs). Typically, DUV lithography uses laser light with wavelengths of 248 and 193 nm. Generally, the immersion lithography is a technique that replaces the usual air gap between the final lens and the wafer surface with a liquid medium that has a refractive index greater than one.
Generally, multiple patterning refers to a class of technologies for manufacturing integrated circuits (ICs), developed for photolithography to enhance the feature density. An example of multiple patterning is double patterning, where a conventional lithography process is enhanced to double the existing number of features. Typically, a spacer is used in the double patterning technique. The spacer refers to a film formed on the sidewall of a pre-patterned feature. By removing the original pre-patterned feature, only the spacer is left. Because there are two spacers for every line, the line density has now doubled.
Typically, existing multiple patterning techniques generate spacers having the profiles that have a shoulder recess (faceting), a tapered bottom (footing), and width non-uniformity due to pattern loading effect. The faceting, footing, and width non-uniformity cause difficulties in maintaining the spacer profile to transfer the pattern to underlying layers. Additionally, the faceting and footing of the spacer profile and the pattern loading effect causes difficulties in controlling critical dimension (CD) and critical dimension uniformity (CDU) of the patterned features. This causes significant design rule limitation on patterns which can be printed, and leads to high manufacturing cost.