Lithographic evaluation of recent 193-nm photoresists

Several 193 nm photoresists from various vendors were investigated using a Micrascan 193 in a cluster configuration. The critical dimensions (CD) investigated were 180 nm and below for dense lines and isolated lines. Contact holes were also evaluated. The photoresist process performance was quantified using a CD SEM, cross section SEM and electrical probe. Photoresist processes were controlled so that the effects of process on CD variations were minimized. Different photoresists process latitude were compared and evaluated for CD uniformity, depth of focus and exposure latitude. The photoresists evaluated were Resist A, Resist B, Resist C, Resist D, Resist E and Resist F. The spin curve and swing curve of these photoresists were studied at different thickness range. Standard and off-axis illumination modes were studied. Focus auto calibration and illumination uniformity were run before the actual exposure of the wafers to ensure the tool was within specification. Send ahead wafers were exposed to choose the nominal exposure. The optimized conditions of the process were chosen based on the availability of resist quantity. E-probe wafers were exposed and analyzed. Wafers for Cross Section SEM were exposed and broken to evaluate line width on different resists for dense, isolated lines and contact holes.