We have prepared and analyzed neutralization layer material to perform perpendicular morphology of Poly
(styrene-block-methyl methacrylate) (PS-b-PMMA) as Block-Co-Polymers (BCPs). Neutralization layer surface
property is optimized by changing hydrophilicity. We have evaluated two types of neutralization layer material. First
one is graft type polymer which makes chemical bonding to substrate. The other is crosslink type polymer which
becomes insoluble to organic solvent by thermal crosslink reaction. We checked neutralization function by changing
film thickness of the neutralization layer under PS-b-PMMA. Regarding to graft type, it was found that when the film thickness of neutralization layer is over 2.3 nm, PS-b-PMMA forms perpendicular morphology on appropriate
neutralization layer. Similarly, regarding to crosslink type, it was found that when the film thickness of neutralization
layer is over 1.9 nm, PS-b-PMMA forms perpendicular morphology on appropriate neutralization layer. Finally, we will show lamella and cylinder patterns changing L0 of PS-b-PMMA on neutralization layer.
We have designed and synthesized molecular resist material, which has just only two part protecting groups in
one molecule (Prot-Mad-2). The resist can resolve below 30 nm hp pattern. We analyzed decomposition reaction using
Prot-Mad-2 at the un-exposed and exposed area quantitatively by taking advantage of its property of high purity and
simple structure. From the HPLC results, it was found that main decomposition reaction was deprotection of Prot-Mad-2.
The ratio of one part de-protected material (Deprot-1-prot-Mad-1) and fully de-protected material (Deprot-2) changed
with exposure dose. It was found that exposure dose of surface roughness maximum coincided with the exposure dose
where materials of two-part protection, one part de-protection and fully de-protection existed equally in the resist film.
Furthermore, dissolution rates of Prot-Mad-2, Deprot-1-prot-Mad-1 and Deprot-2 were totally different. It is considered
that surface roughness was generated by different dissolution rates in the presence of Prot-Mad-2, Deprot-1-prot-Mad-1
and Deprot-2. Our result suggests that reducing a variety of dissolution rates at exposed and un-exposed boundary is a
key to improve line edge roughness (LER).
We have designed and synthesized a molecular resist material, which has no distribution of the protecting
groups and have evaluated its performance as a molecular resist with EB and EUV exposure tool. The molecular resist
attained a resolution of sub-45 nm patterning at an exposure dose of 12 mJ/cm2. It was found that controlling the
distribution of the protecting groups in a molecular resist material has a great impact on improving Line Edge
Roughness (LER). Low LER values of 3.1 nm (inspection length: L = 620 nm) and 3.6 nm (L = 2000 nm) were
achieved with this molecular resist using Extreme UltraViolet (EUV) lithography tool.
In order to enable design of a negative-tone polyphenol resist using polarity-change reaction, five resist
compounds (3M6C-MBSA-BLs) with different number of functional group of &ggr;-hydroxycarboxyl acid were prepared
and evaluated by EB lithography. The resist using mono-protected compound (3M6C-MBSA-BL1a) showed 40-nm hp
resolution at an improved dose of 52 &mgr;C/cm2 probably due to removal of a non-protected polyphenol while the
sensitivity of the resist using a compound of protected ratio of 1.1 on average with distribution of different protected
ratio was 72 &mgr;C/cm2. For evaluation of the di-protected compound based resist, a di-protected polyphenol was
synthesized by a newly developed synthetic route of 3-steps reaction, which is well-suited for mass production. The
resist using di-protected compound (3M6C-MBSA-BL2b) also showed 40-nm hp resolution at a dose of 40 &mgr;C/cm2,
which was faster than that of mono-protected resist. Fundamental EUV lithographic evaluation of the resist using
3M6C-MBSA-BL2b by an EUV open frame exposure tool (EUVES-7000) gave its estimated optimum sensitivity of 7
mJ/cm2 and a proof of fine development behavior without any swelling.
Polymers with methyl acetal ester moiety in the side chain as acid labile protecting group were synthesized and their thermal property, plasma stability and chemical amplification (CA) positive-tone resist characteristics were investigated. 2-Admantyloxymethyl (AdOM) groups in the copolymer indicated lower glass transition temperatures and higher thermal decomposition temperatures than those of 2-methyl-2-admantyl (MAd) groups in the copolymer. AdOM polymer film showed smooth surface roughness after Ar plasma exposure compared with MAd polymer film due to the high thermal stability. The activation energies (Ea) of these deprotection reactions were calculated from Arrhenius plots of these deprotection reaction rate constants. In the low post exposure bake (PEB) temperature region, the Ea of these resists decreased in the order MAd > AdOM. The low Ea methyl acetal resists displayed good thermal flow resist characteristics for contact holes printing. In addition, the low Ea methyl acetal resist achieved a wide exposure latitude of 8.1 % and depth of focus of 400 nm for printing 80 nm 1:1 dense line pattern using NSR-306C (NA 0.78, 2/3 annular). Furthermore, the 65 nm 1:1 dense lines using ASML XT1400 (NA 0.93, C-Quad) for low Ea methyl acetal resist pattern showed no tapered and no footing profiles and small roughness on the lines pattern sidewall was observed.
We have designed and synthesized cholate derivatives (1,4-Bis(methyloxymethylcholate)cyclohexane: C2ChDM and 1,2-Bis(oxymethylcholate)ethane: C2E) to investigate the properties as a chemically amplified (CA) positive-tone Electron-beam (EB) resist material. C2ChDM and C2E which were easily obtained by one-step esterification from cholic acid and dichloride showed glass transition temperatures (Tgs), 85 and 84oC, respectively. These compounds were dissolved in propylene glycol monomethyl ether acetate (PGMEA) and formed amorphous thin films onto silicon wafers by using a spin-coat method. The etch rates of C2ChDM and C2E, which were measured under CF4/CHF3/Ar mixed gas process, were almost the same as poly (p-hydroxystyrene) (PHS). The model resist samples were formulated with C2ChDM and C2E as base matrix and photo-acid generator (PAG) originated from sulfonium-salt (resist-A and B, respectively). These resists showed good sensitivities with EB exposure. Furthermore, the FT-IR spectra of resist-A and B films unexposed and exposed by the EB lithography tool were measured. From the spectral changes of resist-A and B films, we confirmed that a cleavage reaction of ester bond occurred by EB irradiation and bake treatment, and these resists worked as common CA positive-tone resist. The evaluation results with the resist-A and B by using EB exposure tool indicated the resolution of 120 nm lines and spaces pattern.
We designed a novel chemically-amplified negative-tone molecular-resist compound of 3M6C-MBSA-BL, which is a γ-hydroxycarboxylated polyphenol (4,4'-methylenebis[2-[di(2-methyl-4-hydroxy-5-cyclohexylphenyl)] methyl]phenol (3M6C-MBSA)) for EB and EUV lithographies to be used in hp 45 and beyond technology nodes. After selection of photo acid generators (PAGs) and optimization of the concentration of PAG in the resist, we could demonstrate 40-nm line and space patterns resolution by EB exposure. Also dry-etching durability and 1-month shelf life at -20oC were confirmed. Small line-edge roughness (LER) values of 4.5 nm (inspection length: L = 620 nm) and 6.2 nm (L = 1800 nm) were achieved using the 3M6C-MBSA-BL resist.
We have investigated the possibility of amorphous low molecular weight polyphenols as a chemically amplified positive-tone electron-beam (EB) resist. Low molecular weight polyphenol, 4'4-methylenebis{2-[di(2-methyl-4-hydroxy-5-cyclohexylphenyl)]methyl} phenol (3M6C-MBSA) as a base matrix, was protected by 1-ethoxyethyl (EE) groups to control the dissolution rate in 0.26 N tetramethylammonium hydroxide aq. developer. The film distribution in the depth direction for resist components with a Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS) and the Fourier amplitude spectra of line-edge roughness (LER) have been investigated to understand the relationship between them for the resists formulated with 3M6C-MBSA and two types of photo acid generator (PAG), triphenylsulfonium perfluoro-1-butanesulfonate (TPS-PFBS) and triphenylsulfonium n-octanesulfonate (TPS-nOS). From these results, it was found that the resist film consisting of TPS-nOS showed more homogeneous in the depth film distribution than that with TPS-PFBS, and the resist with TPS-nOS also indicated the suppressed LER value of 5.1 nm in the wide frequency range. Therefore, the homogeneity of the resist film may affect the pattern LER.
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