With extreme UV not ready for HVM for the 20nm and 14nm nodes, double patterning options that extend the use of 193nm immersion lithography beyond the optical resolution limits, such as LELE (Litho-Etch-Litho-Etch) and SADP (Self Aligned Double Patterning), are being used for critical layers for these nodes. LELE requires very stringent overlay capability of the optical exposure tool. The spacer scheme of SADP starts with a conformal film of material around the mandrels and etched along the mandrel sidewalls to form patterns with doubled frequency. SADP, while having the advantage of being a self-aligned process, adds a number of process steps and strict control of the mandrel profile is required. In this paper, we will demonstrate a novel technique - ASDP (Anti-Spacer Double Patterning), which uses only spin-on materials to achieve self-aligned double patterning. After initial resist patterning, an Anti-Spacer Generator (ASG) material is coated on the resist pattern to create the developable spacer region. Another layer of material is then coated and processed to generate the second pattern in between the first resist pattern. We were able to define 37.5nm half pitch pattern features using this technique as well as sub-resolution features for an asymmetric pattern. In this paper we will review the capability of the process in terms of CD control and LWR (line width roughness) and discuss the limitations of the process.
This work discusses the requirements and performance of Honeywell's middle layer material, UVAS, for tri-layer
patterning. UVAS is a high Si content polymer synthesized directly from Si containing starting monomer components.
The monomers are selected to produce a film that meets the requirements as a middle layer for tri-layer patterning (TLP)
and gives us a level of flexibility to adjust the properties of the film to meet the customer's specific photoresist and
patterning requirements. Results of simulations of the substrate reflectance versus numerical aperture, UVAS thickness,
and under layer film are presented. ArF photoresist line profiles and process latitude versus UVAS bake at temperatures
as low as 150ºC are presented and discussed. Immersion lithographic patterning of ArF photoresist line space and contact
hole features will be presented. A sequence of SEM images detailing the plasma etch transfer of line space photoresist
features through the middle and under layer films comprising the TLP film stack will be presented. Excellent etch
selectivity between the UVAS and the organic under layer film exists as no edge erosion or faceting is observed as a
result of the etch process. A detailed study of the impact of a PGMEA solvent photoresist rework process on the
lithographic process window of a TLP film stack was performed with the results indicating that no degradation to the
UVAS film occurs.
High-refractive-index fluids (HIFs) are being considered to replace water as the immersion fluid in
next generation 193nm immersion scanner. We have demonstrated the attractive optical properties for our HIF
candidates, HIL-001, HIL-203 and HIL-204. Especially, HIL-203 and HIL-204 have higher transmittance
compared to water. In this paper, we describe our latest results on the comparative evaluations including
photo-degradation behavior and lens contamination phenomenon in a flow system. For laser induced fluid
degradation behavior, it was shown the higher initial transmittance resulted in the higher laser durability.
However, the complicated phenomenon was observed for the lens contamination test. That is, HIL-204 with
higher initial transmittance showed higher lens contamination rate than HIL-203. From several analyses, the
complicated behaviors among HILs were speculated to be caused by the different nature of photo-degraded
impurities. In order to control the fluid transmittance change and suppress the lens contamination during
exposure, the refining process was definitely necessary for HIL reuse system. Based on the refining mechanism
and the refining material design, we have developed an appropriate refinement unit named Refine B. This
approach provided us with the result that Refine B could control the change of fluid transmittance and suppress
the lens contamination rate.
The combination of immersion lithography and reticle enhancement techniques (RETs) has extended 193nm
lithography into the 45nm node and possibly beyond. In order to fulfill the tight pitch and small critical dimension
requirements of these future technology nodes, the performance of 193nm resist materials needs to further improve. In
this paper, a high performance 193nm photoresist system based on fluorosulfonamide (FSM) is designed and
developed. The FSM group has good transparency at 193nm. Compared to the commonly used hexafluoroalcohol
(HFA) group, the trifluoromethyl sulfonamide (TFSM) functionality has a lower pKa value and contains less fluorine
atoms. Polymers containing the TFSM functionality have exhibited improved dissolution properties and better etch
resistance than their HFA counterparts. Resists based on the FSM-containing polymers have shown superior
lithographic performance for line, trench and contact hole levels under the 45nm node exposure conditions. In
addition, FSM resists have also demonstrated excellent bright field and dark field compatibility and thereby make it
possible to use one resist for both bright field and dark field level applications. The structure, property and lithographic
performance of the FSM resist system are reported.
The focus of this paper is to utilize the acidity of hexafluoroalcohol (HFA) in addressing performance deficiencies associated with current 193nm methacrylate resist materials. In this study, we have designed and developed a variety of HFA pendant methacrylate monomers and the corresponding imaging polymers for ArF lithography. It was shown that typical swelling behavior observed in methacrylate resists can be substantially reduced or eliminated by replacing commonly used multicylcic lactone polar functionalities with acidic HFA side chains. The incorporation of aliphatic spacers between HFA and polymer backbone were found to be more effective than cyclic hindered moieties, in achieving linear dissolution characteristics. The typical poor etch stability associated with fluorine atoms in HFA can be substantially minimized by designing side chains with a combination of appropriate cyclic and aliphatic moieties and fine-tuning the corresponding polymer compositions. PEB sensitivity of high activation energy protecting group (e.g., methyladamentyl group) based methacrylate resists can be substantially improved through the incorporation of acidic HFA side chains (6nm/C to <1 nm/C). The key application space for HFA-methacrylate resists appears to be trench level lithography. It was also demonstrated that these HFA materials are compatible with immersion lithography and result in dramatically improved process windows for iso trench features, in addition to other lines/space features.
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