Directed self-assembly (DSA) of block copolymer (BCP) thin films has been extensively researched as an alternative lithographic technology to enhance the resolution beyond the limitation of current lithography techniques. One of the most critical factors need to be addressed for DSA process to be accepted at high volume manufacturing (HVM) is defect density of DSA pattern. The defects of thermodynamically driven DSA process, such as the dislocation defects in LiNe flow, are known as kinetically trapped metastable structures. Therefore, a key to eliminate those defects is to find out the effective kinetic pathway of assembly that enables BCP to reach to defect-free structure more easily. In addition to defect annihilation, easy pathway will also allow faster assembly, consequently reducing the cost of ownership of DSA process. The obvious approach for faster assembly in DSA process is to increase annealing temperature. In this study, we address the impact of annealing temperature on DSA process. First, increasing annealing temperature makes the free surface of a PS-b-PMMA film more PMMA preferential. Because of altered boundary condition at the top surface, more careful optimization of backfilling brush was required to maintain preferred orientation of BCP films. Second, the dimension of BCP is also affected by annealing temperature. Temperature dependency of BCP dimension was quantitatively investigated by CD-SEM and DSA-APPS Offline CD Measurement Software (Figure 1a). Based on the measured values, the dimension of chemical pattern is accordingly modified to achieve aligned DSA pattern (Figure 1b). We anticipate our finding from this study can be generally applied for other BCP systems.
 Ruiz, Ricardo, Huiman Kang, François A. Detcheverry, Elizabeth Dobisz, Dan S. Kercher, Thomas R. Albrecht, Juan J. de Pablo, and Paul F. Nealey. "Density multiplication and improved lithography by directed block copolymer assembly." Science 321, no. 5891 (2008): 936-939.
 Gronheid, Roel, Paulina Rincon Delgadillo, Hari Pathangi, Dieter Van den Heuvel, Doni Parnell, Boon Teik Chan, Yu-Tsung Lee et al. "Defect reduction and defect stability in IMEC's 14nm half-pitch chemo-epitaxy DSA flow." In SPIE Advanced Lithography, pp. 904905-904905. International Society for Optics and Photonics, 2014.
 Hur, Su-Mi, Vikram Thapar, Abelardo Ramírez-Hernández, Gurdaman Khaira, Tamar Segal-Peretz, Paulina A. Rincon-Delgadillo, Weihua Li, Marcus Müller, Paul F. Nealey, and Juan J. de Pablo. "Molecular pathways for defect annihilation in directed self-assembly." Proceedings of the National Academy of Sciences 112, no. 46 (2015): 14144-14149.
Previous studies of contact-hole photoresist-performance1 with various filter membranes demonstrated that UPE (ultra
high molecular weight polyethylene) membranes are effective in reducing defectivity with minimal changes in the
resist's imaging properties. In the same study, nylon membrane filters, known to have absorptive properties, altered the
lithographic imaging performance of the photoresist and produced higher overall defectivity.
This study more closely examines the absorption effects of nylon membrane on contact hole photoresist and attempts to
quantify changes to the photoresist by measuring the change in lithographic performance, and its' effect on defectivity.
Additionally, this study provides recommendations on the filtration parameters which take advantage of the absorptive
capability of the nylon membrane, while minimizing the changes to the lithographic performance of the photoresist.
The effect of filtration on defectivity has been studied extensively with line-space patterns. However, the ability to have
defect free contacts is equally as important. Resist materials are specifically designed for contact holes, and therefore it
is important to also study their varied sources of defectivity.
In this study, unpatterned and patterned wafer defectivities have been studied as a function of point of use filter. The
filter retention rating was held constant at 10 nm while the filter membrane material was varied, including ultra-high
molecular weight polyethylene (UPE), Nylon and composite filters. A recommendation will be made as to which point-of-use filter performed best with the contact hole specific resists tested.
Image reversal trilayer (IRT) combines three lithographic patterning enhancement approaches: image reversal, spin on
hard masks, and shrink for recess types of features. With IRT, photoresist imaging is done directly on top of the carbon
underlayer. Thick IRT-Carbon Hard Masks (CHM) films provide effective antireflection with high NA lithography and
are more etch resistant than common photoresist. IRT-Silicon Hard Masks (SiHM) can be coated over the resist patterns
in the lithography track. IRT etching reverses the resist pattern into the IRT-SiHM and transfers this image to the IRTCHM.
The recessed patterns in the IRT-CHM are smaller than the CD of the photoresist feature from an inherent
shrinking capability of the IRT-SiHM.
Continuous improvements to both IRT-SiHM and IRT-CHM have been made. Silicon contents in IRT-SiHM have been
pushed as high as possible while not impacting other important properties such as stability, coating quality and resist
compatibility. Newer polysiloxane IRT-SiHM no longer require resist freezing prior to coating. Carbon contents in IRTCHM
have been pushed as high as possible while maintaining solubility and a low absorption which is important when
resist imaging is done directly on top of the IRT-CHM.
Feasibility of this image reversal trilayer process was previously demonstrated on L/S and pillar gratings. Recent work
focused on nonsymmetrical 2D gratings and simultaneous patterning of L/S gratings at different pattern densities.
Particular emphasis is given to pattern density effects which are applicable to any top-coating image reversal process.
This paper describes the lithography, pattern transfer process and 2nd generation hard mask materials developed for IRT