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
Bottom Anti-Reflective Coatings (BARCs) have been widely used in the lithography process for decades. BARCs play
important roles in controlling reflections and therefore improving swing ratios, CD variations, reflective notching, and
standing waves. The implementation of BARC processes in 193nm dry and immersion lithography has been
accompanied by defect reduction challenges on fine patterns. Point-of-Use filters are well known among the most
critical components on a track tool ensuring low wafer defects by providing particle-free coatings on wafers. The filters
must have very good particle retention to remove defect-causing particulate and gels while not altering the delicate
chemical formulation of photochemical materials.
This paper describes a comparative study of the efficiency and performance of various Point-of-Use filters in reducing
defects observed in BARC materials. Multiple filter types with a variety of pore sizes, membrane materials, and filter
designs were installed on an Entegris Intelligent(R) Mini dispense pump which is integrated in the coating module of a
clean track. An AZ(R) 193nm organic BARC material was spin-coated on wafers through various filter media.
Lithographic performance of filtered BARCs was examined and wafer defect analysis was performed. By this study, the
effect of filter properties on BARC process related defects can be learned and optimum filter media and design can be
selected for BARC material to yield the lowest defects on a coated wafer.
This paper introduces high performing contact hole resist targeting 65 nm node and below IC applications. Both 80 nm and 100 nm contact hole performance are evaluated under optimized condition by Prolith<sup>TM</sup> simulations and the advantage of the shrinking technique (RELACS<sup>TM</sup>) is discussed for 65 nm node. The functionality of 193 nm polymers and the influence of resist components on lithographic performance are described with experimental design. The optimized resist, AZ<sup>®</sup> AX2050P is versatile in lithographic performance with large process window, excellent resist profile, good contact circularity and sidewall roughness. Its unusual PEB sensitivity property, resist pattern thermal flow behavior and performance with RELACS<sup>TM</sup> material are also reported. AZ<sup>®</sup> AX<sup>TM</sup>2050P has a high resolution combined with a large depth of focus and an iso-dense overlap window with RELACS<sup>TM</sup> R602 [85 nm CD (NA 0.85) DOF 0.30 μm @ Exposure latitude 8%].
Line-edge roughness (LER) continues to be one of the biggest challenges as the CD size shrinks down to sub 100 nm. It is shown that resist components as well as illumination conditions play a big role. Influence of resist components in both 248 and 193nm chemically amplified resist formulations has been reported but the root cause is not fully understood and may be platform or even specific formulation dependent. This paper attempts to tackle the issue from the processing side. Effects of a simple hard bake process on the LER were studied. In the hard bake process, a given resist pattern was typically baked close to the glass-transition temperature after the development process. LER improved dramatically due to melting down of the rough surface. However, the wall angle of the edge lines also started to degrade at the optimum hard bake temperature. Studies on the effects of polymer Tg, hard bake temperature and time and the issues of the process are discussed.
The lithographic performance of a new class of onium type photo acid generators (PAGs) developed by 3M Company has been evaluated using standard hybrid/acetal and ESCAP type DUV (248 nm) photoresist formulations. The new PAGs produce perfluoroalkyl sulfonylimides or sulfonylmethides with superacidic properties matching or exceeding the acid strength of commonly known perfluoroalkyl sulfonic acids, such as trifluoromethane sulfonic acid. The direct comparison of near commercial photoresist formulations containing onium perfluoroalkyl sulfonates with identical materials using equimolar amounts of the new PAGs revealed that the new 3M PAGs give rise to almost identical lithographic properties, such as resolution, DOF, and exposure latitude. In addition, secondary properties such as photoresist stability, delay stability, or line edge roughness are almost equivalent, and thus the new PAGs are considered as suitable candidates used for the manufacturing of high volume production photoresists.
The present paper examines the applicability of three basic resist types (acetal, hybrid, t-butylester) to print sub-0.2 micrometer contact holes (C/H) using state-of-the-art illumination and processing techniques. In terms of ultimate resolution and DOF the acetal-based material showed the best performance under standard processing conditions, but exhibited serious limitations upon application of a half-tone phase-shift mask (HT-PSM) due to side-lobe formation. The hybrid material showed significantly better HT-PSM compatibility and -- due to an enhanced adaptability to practical thermal flow processes -- the best results upon application of a postbake to trigger thermally induced shrinkage. The t-butylester material usually performed second to the best under any selected illumination condition, and may be considered as top performer from a general point of view as no real show-stopper was observed. Thermal flow results of the hybrid material are discussed in more detail and briefly compared with alternate shrinking technologies, such as RELACS<SUP>TM</SUP> or CARL<SUP>TM</SUP>.