As critical dimensions continue to shrink in lithography, new materials will be needed to meet the new demands
imposed by this shrinkage. Recently, there are needs for novel materials with various substrates and immersing process,
including double patterning process, a high resolution implant process, and so on. Among such materials, Developable
Bottom Anti-reflective Coating material (DBARC) is a good candidate for high resolution implant application as well as
double patterning. DBARC should have reflectivity control function as an ordinary BARC, as well as an appropriate
solubility in TMAH-based conventional developer after exposure and bake process. The most distinguished advantage of
DBARC is to skip BARC etch process that is required in normal BARC process. In spite of this advantage, the
photoresist profile on DBARC could be influenced by components and process conditions of DBARC. Several groups
have tried to solve this issue to implement DBARC to new process.
We have studied material-related factors affecting photoresist profiles, such as a polymer, photo-acid generators
(PAGs), and additives. And we explored the effect of process condition for photoresist and DBARC. In case of polymer,
we studied the effect of dissolution rate in developer and crosslinking functionality. For PAGs and additives, the effect
of acid diffusivity and cross-linking degree according to their bulkiness were examined. We also evaluated coated film
stability in a photoresist solvent after BARC bake process and compared lithographic performance of various DBARC
formulations. In addition, the effect of photoresist profile with bake condition of photoresist and DBARC were
investigated. In this paper, we will demonstrate the most influential factors of DBARC to photoresist profile and
suggest the optimum formulation and process condition for DBARC application.
Most semiconductor companies are using Bottom Anti-Reflective Coating (BARC) on their lithography process to
reduce bottom reflectivity, which is cause of standing wave, pattern collapse, and bad pattern profile, and to improve
lithographic performance. BARC has been diversified to adapt to the wavelength of exposure light and refractive indices
of photoresists and substrates. Recently, many semiconductor companies introduce new process, such as immersion
process and double patterning process, to get high resolution for next generation semiconductor and they are trying to
apply these processes to their mass production. Among those process solutions, a strong candidate for high resolution is
introduction of hyper NA(Numerical Aperture) exposure tool, using immersion process. There is one thing to solve for
BARC material when immersion process is applied. It is reflectivity. As NA of exposure tool increases, reflectivity from
a substrate also increases, simultaneously. We simulated the difference of reflectivity with increasing NA and we found a
proper way how to control reflectivity on immersion process with refractive indices of BARC. We will report simulation
data for immersion process and introduce our new developed BARC for hyper NA process in this paper.
As the feature size becomes smaller, it is difficult for the lithography progress to
keep pace with the acceleration of design rule shrinkage and high integration of memory device.
Extreme Ultra Violet Lithography (EUVL) is a preferred solution for the 32nm node. In this
paper, we have synthesized two types of polymers. One is based on hydroxy phenol, the other
is based on hydrocarbon acrylate type polymer. We have diversified each polymer type
according to different activation energies for deprotection reaction. In this experiment, we have
observed on the resist lithographic performance such as resolution, LER (Line Edge
Roughness), photo-sensitivity, and out-gassing during exposure. Different properties according
to activation energy were well explained by acid diffusion and polymer free-volume.
Recently, KrF lithography has extended to 100nm technical node using various techniques and pushed ArF lithography to sub-100nm application. To enhance resolution, there are many problems to be solved, like dark erosion (dark film loss), sloped profile, line edge roughness (LER), and so on. Also, thin resist film must be used to prevent pattern collapse. In general, the aspect ratio is less than 2.5 for sub 100nm. For this reason, chemically amplified resist has to get high etch resistance, low dark film loss and vertical profile shape at maximum resolution. Many efforts have been made to solve these problems and to improve resist performance. In this study, we tried to resolve some of these problems using various acid-quenching systems. We estimated the quencher ability using acid diffusion depth in resist film by sandwich method and pKb values of amines. The changes of lithographic properties according to the application of different amines were investigated. It was found that acid-quenching ability of an amine was not related to its basicity from sandwich experiment results. In fact, quenching efficiency was more closely related to the amine molecular structure and bulkiness of a substituent attached to nitrogen atom. We observed that pattern shape and process margin were not directly related to the basicity of an amine, but more related to quenching efficiency. The amines having higher quenching ability show wider process margin. However, other lithographic properties such as LER and dark erosion were not affected by acid-quenching ability. It is believed that they are determined by other components including polymer, protection groups, and PAGs.
Various derivatives of modified poly(4-hydoxystyrene-co-4-(1-ethylethoxystyrene))(M-EEPHS) were synthesized by insertion of third monomer unit such as styrene, 4-acetoxystyrene, 4-methoxycarbonyloxystyrene, tertbutoxycarbonyloxystyrene, tert-butyl acrylate, and 4-(1-cyclohexylethoxy)styrene. Their dissolution rate behavior was investigated with different blocking level. From the average dissolution rate of M-EEPHS in a 2.38wt% TMAH solution as a function of the total protection%, hydrophobicity was proven as more influential factor for the dissolution inhibition rather than hydrogen bonding by ester or carbonate functionality in a blocking group. To study structural effect on KRF lithographic performance, resists containing M-EEPHS were formulated and testified. Defects that are found in EEPHS based resist, such as LER (Line Edge Roughness) and top surface erosion at defocus can be solved by incorporation of carbornate, bulky acetal functionality or dissolution inhibition group. When hybrid system, which contained both M-EEPHS and poly[4-hydroxystyrene-co-tert-butyl acrylate-co-4-(3-cyano-1,5-di-tert-butyl carbonyl pentyl styrene)](P(HS-TBA-CBPS)) as an annealing type resin, were compared with the lithographic results of single polymeric system (M-EEPHS only), their performances were directly projected to those of blends of high activation type and low activation type resin.
We prepared ter-polymer of hydroxystyrene, tert-butyl acrylate and 4-(3-cyano-1,5-di-tert-butyl carbonyl pentyl styrene) (P(HS-TBA-CBPS)) and discussed a characteristic of prepared polymer. As TBA, newly introduced monomer increases, contrast of resist is improved. And the prepared polymer was blended with poly(4-hydroxystyrene-co-4-(1-ethylethoxystyrene)) (EE-PHS). The synergic effect on a resist performance in KrF lithography by the combination of high and low activation energy system was shown. A resist using blending polymer was shown a good performance on resolution and LER(Line Edge Roughness) than resist using polymer separately. Based on the results, it was found that high performance KrF resist could be obtained by optimization of polymer blending.
Dissolution rate of polymer has known as one of the most profound factors to determine profiles of DUV resists. A novel copolymer, poly[4-hydroxystyrene-co-4-(3-cyano-1,5-di-tert-butyl carbonyl pentyl styrene)] (PHSCBPS), was prepared and blended with poly(4-hydroxystyrene-co-4-(1-ethylethoxystyrene)) (EEPHS) to study the effect of dissolution rate on the KrF resist profile. The dissolution rates of the blends in aqueous alkaline solution were measured by dissolution rate monitor (DRM). Molecular weight and polydispersity were measured by GPC. Without altering other components of the resist, the profile was clearly affected by the dissolution rates of the polymer blends. In this paper we will describe resist profile change according to dissolution rate, molecular weight and polydispersity of polymer blend. For given blends, the best and optimum resist profile was found in the range of 200~300 Angstroms/min dissolution rate, 12,000 of molecular weight and 1.2~1.3 of polydispersity. In case of PAG, profile of KrF resist is also influenced by counter ion of PAG. Based on the results, high performance KrF resist composition was found by incorporating appropriate photo acid generator (PAG) and other additives. Optimized resist produced rectangular profile without losing process margin and resolution.
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