Directed self-assembly (DSA) and nanoimprint lithography (NIL) have been widely developed for low-cost nanoscale patterning. Although they are currently regarded as "alternative lithography," some papers show their potential to be candidates for next-generation lithography (NGL). To actualize the potential, the contribution of metrology engineers is necessary. Since the characteristics of the lithography techniques are different from those of conventional lithography, new metrology schemes correlated with each characteristic are required. In DSA of block copolymer (BCP), a guide is needed to control the direction and position of BCP. Therefore, it is necessary to monitor the relationship between the guide and the BCP pattern. Since the depth of guide or the coating thickness variation of BCP over guide influences the behavior of phase separation of BCP, 3D metrology becomes increasingly important. In NIL, residual resist thickness (RLT) underneath the pattern should be measured because its variation affects the CD variation of transferred pattern. 3D metrology is also important in NIL. Optical critical dimension (OCD) metrology will be a powerful tool for 3D metrology. In this work, some applications of OCD for alternative lithography have been studied. For DSA, we have tried to simultaneously monitor the guide and BCP pattern in a DSA-based contact hole shrinking process. Sufficient measurement accuracy for CD and shapes for guide and BCP patterns was achievable. For NIL, sufficient sensitivity to RLT measurement was obtained.
Directed Self Assembly (DSA) for contact layers is a challenging process in need of reliable metrology for tight process control. Key parameters of interest are guide CD, polymer CD, and residual polymer thickness at the bottom of the guide cavity. We show that Optical CD (OCD) provides the needed performance for DSA contact metrology. The measurement, done with a multi-channel spectroscopic reflectometry (SR) system, is enhanced through elements of a Holistic Metrology approach such as Injection and Hybrid Metrology.
As design rules shrink, hotspot management is becoming increasingly important. In this paper, an automatic system of
hotspot monitoring that is the final step in the hotspot management flow is proposed. The key technology for the
automatic hotspot monitoring is contour-based metrology. It is an effective method of evaluating complex patterns, such
as hotspots, whose efficiency has been proved in the field of optical proximity correction (OPC) calibration. The
contour-based metrology is utilized in our system as a process control tool available on mass-production lines.
The pattern evaluation methodology has been developed in order to achieve high sensitivity. Lithography simulation
decides a hotspot to be monitored and furthermore indicates the most sensitive points in the field of view (FOV) of a
hotspot image. And quantification of the most sensitive points is consistent with an engineer's visual check of a shape of
a hotspot. Its validity has been demonstrated in process window determination. This system has the potential to
substantially shorten turnaround time (TAT) for hotspot monitoring.