Tetramethylammonium hydroxide (TMAH) aqueous solutions has been used as a developer for chemically amplified resists (CARs), dissolving polymer with polar groups generated by exposure. Although the dissolution kinetics of CARs has been widely studied, it is necessary to understand molecular-level information such as interaction between polymer chains, to consider the dissolution of thin and minute resist films that are used nowadays. In this study, we used dynamic light scattering (DLS) to study the state of PHS chains in TMAH aqueous solution. The effect of the concentration of each ionic species on dispersion of PHS chains was investigated using solutions whose base concentrations were changed by two methods: dilution with pure water and neutralization with acid. PHS chains were well dispersed as the base concentration and ionic strength of the solution increased, while they aggregated as these two factors decreased. We also studied the dissolution behavior of PHS films under nearly identical conditions using quartz crystal microbalance (QCM). The dissolution of the films was also affected by the two factors described above. In addition to this, with the decrease in the above two factors, we observed formation of large swollen layer as we have reported in the past. We assumed these effects on dissolution of films were mainly due to the acid-base equilibrium at the solid-liquid interface.
Photoresists have been widely used as patterning materials for electric devices such as displays and semiconductor. Understanding pattern formation mechanism is essential for the efficient development of resist materials. In this study, we investigated the dissolution kinetics of poly(4-hydroxystyrene) (PHS) with weight-average molecular weights (Mw) of 9000-30000 and molecular weight distribution (Mw/Mn) of 1.07-1.20. The dissolution kinetics of PHS films was observed in tetramethylammonium hydroxide (TMAH) aqueous developers using a quartz crystal microbalance (QCM) method. The TMAH concentration was changed from 0 to 2.38 wt%. The obtained data were analyzed using polynomial regression to clarify the effects of Mw and Mw/Mn on the dissolution kinetics of PHS films. From the results of analysis, both dissolving and swelling behavior largely depended on Mw/Mn. Mw had a little effect on the dissolving, and however, had a large effect on the swelling in dilute TMAH aqueous solution.
In the development of highly resolving and highly sensitive resist materials, stochastic phenomena (LER and stochastic defect generation) are a critical issue. In this study, the dependence of the transient swelling layer formation of resist backbone polymer on its molecular weight and dispersion was investigated for the development of highly resolving resist materials. The dissolution kinetics was measured for different molecular weights and dispersions using quartz crystal microbalance (QCM) method. The relationship between transient swelling layer and stochastic defect formation is discussed.
We investigated the dissolution kinetics of poly(4-hydroxystyrene) (PHS) in an alkali developer with tetramethylammoniumhydroxide (TMAH). Experiments using PHS with different molecular weights and molecular weight dispersions and developer with different concentrations of TMAH led to the clarification of the dissolution behavior. Not only a change in the dissolution time but also a change in the dissolution behavior was observed upon changing the concentration of the developer. The dissolution behavior depends on an index calculated from values indicating the effects of swelling and dissolving. The dissolution occurred through the swelling of the polymer bulk and the subsequent diffusion of polymer chains into the solution bulk. The development using the alkali aqueous solution system was complex. The swelling rate should not be much larger than the dissolving rate for the development of high-resolution resists because a high swelling rate causes the generation of defects during the fabrication of fine structures.
Extreme Ultra Violet (EUV) lithography is one of the most promising candidate technologies for the high-volume manufacturing (HVM) of semiconductor devices at the sub-14 nm half pitch lines and spaces (LS) pattern for 7 nm node and beyond. EUV resists is strongly required high resolution (R) with high sensitivity (S) and low line edge/ width roughness (L) for HVM application. Experimental results on chemically amplified (CA) resist will be shown to study the influence of proton source, photo acid generator (PAG) cation and the other materials on lithographic performance, and then resist formulation designed for improving RLS trade-off will be discussed.
Extreme Ultra Violet (EUV) Lithography is being thought to be one of the most promising candidate technologies to replace current optical lithography for the high-volume manufacturing of semiconductor devices at the 10 nm node and below. Through-put still seems to be under the target, so EUV resist materials are strongly required high resolution (R) with high sensitivity (S) and low line edge/width roughness (L). However, the chemically amplified resists should overcome RLS-trade-off. We focused on the development of EUV resist by the combination of the low activation energy protecting group (PG) and high quantum yield PAG for overcoming RLS trade-off.
Multi-layer stack application will be established at manufacturing process beyond 65nm node. Multi-layer stack
application means laminated layer like a Photoresist, Si contained hard mask, and Carbon hard mask on substrate. Multilayer
stack application can be solved anti-reflection at hyper NA (that means more than 1 numerical aperture) and less
etching resistance in thinner film resist, so Multi-layer stack application is required for 193nm immersion lithography
process. And criteria of our material in Multi-stack application are spin-on and drain compatible type. In this report, we
will discuss about Spin-on Si-contained hard mask and spin-on carbon hard mask criteria, our experiment and results to
solve issue.
Spin-on Si-contained hard mask is required 3-factors that is unti-reflection from substrate at hyper NA conditions, resist
matching, and higher etching resistance. It is general that higher Si-content ratio in based polymer can't be matched with
current 193nm photoresist. But Lower Si-contained Hard Mask can't be resisted by dry etching. In this report, we will
discuss about our material approach for good resist matching (no footing issue) without reduction of Si-content ratio,
pattern transfer ability by dry etching, and reflectivity simulation results at Hyper-NA condition.
LWR issue after dry etching is key factor of Multi-layer stack application. We estimate that composition of based
polymer in carbon hard mask material and film density in carbon Hard Mask is relative to LWR issue after dry etching.
In this report, we will discus about our material approach for less LWR issue after dry etching.
In this study, we have demonstrated a resist process to fabricate sub 45-nm lines and spaces (L&S) patterns (1:1) by using electron projection lithography (EPL) for a back-end-of-line (BEOL) process for 45-nm technology node. As a starting point we tried to fabricate sub 45-nm L&S (1:1) patterns using a conventional EPL single-layer resist process. There, the resolution of the EPL resist patterns turned out to be limited to 70 nm L&S (1:1) with aspect ratio (AR) of 3.3 which was caused by pattern collapse during the drying step in resist develop process. It has been common knowledge that pattern collapse of this type could be prevented by reducing the surface tension of the rinse-liquid and by decreasing the AR of the resist patterns. Therefore, we first applied a surfactant rinse to a single-layer resist process that could control the pattern collapse by its reduced surface tension. In this experiment, we used the ArF resist instead of the EPL resist because the surfactant that we were able to obtain was the one optimized to the ArF resist materials. From the results of ArF resist experiments, it was guessed that it was difficult for the EPL resist to obtain the L&S patterns with AR of 3.5 or more even if we used the surfactant optimized to the EPL resist. And we found that it was considerably difficult to form 45-nm L&S patterns with AR of 5.1 that was our target. Next, we evaluated a EPL tri-layer resist process to prevent pattern collapse by decreasing the AR of the resist patterns. Because in a tri-layer resist process the purpose of the top-layer resist is to transfer pattern to the middle-layer, a thinner top-layer resist was selected. By using the tri-layer resist process we were able to control the resist pattern collapse and thus were successful in achieving 40-nm L/S (1:1) top-layer resist patterns with AR of 2.3. The process also gave us 40-nm L&S (1:1) patterns after low-k film etching. And moreover, using our tri-layer resist process we were able to fabricate a wiring device with Cu/low-k. Although it was our first attempt, the process resulted in a high yield of 70 % for a 60-nm (1:1) wiring device. As a part of our study we conducted failure analysis of the results of our experiment. We found that the failures were located at the edge of the wafer and might originate in the bottom-layer pattern collapse. We thought that the wiring yield could be increased by control the bottom-layer pattern collapse. These findings indicated that our tri-layer resist process had a high applicability for device fabrication in BEOL.
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