Interactions between the silicon hardmask and the photoresist have received considerable attention for
utilization of these materials in a trilayer scheme. In contrast, the interactions between the carbon layer and
the silicon hardmask have received little or no consideration. In this paper, we present the effects of these
interactions on the performance of the silicon hardmask. Poor interactions were observed to result in a more
hydrophilic surface and poor lithographic performance of the silicon hardmask. However, beneficial
interactions between the carbon layer and the silicon hardmask resulted in a silicon film that was denser with
a hydrophobic surface. The resulting denser film had a slower CF4 etch rate and produced square, clean profiles.
A comparison of bake temperature effects on two hardmask materials was performed. The first hardmask
was a silicon-based material, BSI.M06092K, and the second was a titanium-based material, BSI.S07051.
The materials have inherently different chemistries that performed differently as bake temperature was
varied. BSI.M06092K undergoes condensation of silanols on the wafer during baking and BSI.S07051
undergoes removal of the ligand followed by condensation during baking. In general, the performance of
BSI.M06092K showed little or no dependency on bake temperature. BSI.S07051 showed an increase in
contact angle with water, slower etch rates, and square profiles as bake temperature increased.
The 45-nm node will require the use of thinner photoresists, which necessitates the use of multilayer pattern transfer
schemes. One common multilayer approach is the use of a silicon-rich anti-reflective hardmask (Si BARC) with a
carbon-rich pattern transfer underlayer (spin-on carbon, or SOC). The combination of the two layers provides a highly
planar platform for a thin resist, and provides a route to etch substrates due to the alternating plasma etch selectivities of
the organic resist, inorganic Si BARC, and organic SOC. Yet such schemes will need to be optimized both for pattern
transfer and optics. Optimizing optics under hyper-NA immersion conditions is more complicated than with standard
(that is, NA<1) lithography. A rigorous calculation technique is used to evaluate and compare standard lithography to a
hyper-NA case using a multilayer stack. An example of such a stack is shown to have reasonable lithographic
A novel polyamic acid-based, 248-nm wet-developable BARC has been prepared to improve structure clear-out
and lessen post-development residue. This material showed an excellent process window and controllable
development rates that can be achieved by simply changing the formulation. It is a highly absorbing BARC
with n and k values equal to 1.73 and 0.49, respectively. Lithography with this material has shown 180-nm
dense profiles with P338 and M230Y. These profiles exhibited minimal undercutting with good clearing
between the lines. Clear-out has been demonstrated for 120-nm trenches. Post-development residue of the
material was tested at various temperatures and was determined to be 6 Å or less. In addition, sublimation
Multi-layer lithography processes have been introduced to fabricate very fine structures over a topographic surface for advanced semiconductor device production. The first layer formed on the topographic surface is the planarization layer to provide surface planarity for additional thin layer(s) of material. Such materials could be a photoresist, a hardmask, or both with uniform film thickness for the lithography step to image the structures. However, the large size and distribution variation of the topography structures across the substrate surface have a major impact on the performance of the lithography processes. A new planarization process, contact planarization (CP), has been introduced to improve thickness uniformity and to provide global surface planarity for multi-layer lithography applications. This study focuses on planarizing an experimental organic 193-nm BARC layer on via wafers to minimize iso-dense film thickness bias and provide improved global surface planarity for the bilayer photolithography process. In addition, minimum thickness bias improves control of downstream processes such as plasma etching. This paper will discuss this unique planarization process and its performance with various thicknesses of the experimental 193-nm BARC on via wafers. The photolithography performance of the material and process will be discussed.
New fast-etching bottom anti-reflective coatings have been prepared at Brewer Science, Inc., for 193-nm lithography. These materials, EXP03087B and EXP03066, were targeted for first and second reflectivity minima thickness, respectively. The optical constants (n and k) of these materials were 1.70 and 0.50, respectively, for EXP03087B and 1.71 and 0.31, respectively, for EXP03066. After thermosetting, these materials were immiscible with photoresists and were not affected by base developer. Profiles utilizing these BARCs with JSR's AR1221J photoresist have shown 90-nm (l:l line space) dense lines and 100-nm lines with FFA’s GAR8105G1 resist.
New materials prepared at Brewer Science, Inc., have been targeted for first (30 to 35 nm) and second (80 to 90 nm) reflectivity minima thickness, have less than 0.1% reflectivity, and were fast etching compared to commercially available photoresists. The optical constants of these materials were measured with a variable angle spectroscopic ellipsometer (VASE) and ranged from 1.6 to 1.8 for the real refractive index and from 0.31 to 0.65 for the imaginary refractive index. Etching of these materials gave a selectivity of 1.6:1 with CF4 gas, and a selectivity of 1.3:1 with HBr/O2 compared to photoresist. After thermosetting, these materials were immiscible with photoresists and were not affected by base developer. Profiles utilizing the second reflectivity minimum BARC with JSR’s AR414J photoresist have shown 90-nm (1:1 line space) dense lines and 70-nm (1:2 line space) semi-dense lines. Profiles with first reflectivity minimum BARCs showed 110-nm dense lines with JSR’s AR414J resist and 90-nm lines with FFA’s GAR8105G resist.
A novel spin-bowl-compatible bottom anti-reflective coating (BARC) for i-line applications is presented in this study. The BARCs were prepared from a titanate sol-gel material, which exhibits excellent spin-bowl compatibility with a wide variety of solvents. A variable angle spectroscopic ellipsometer measurement on the titanate BARC gives an n (real refractive index) value of 1.71 and a k (imaginary refractive index) value of 0.40. The titanate BARC shows good compatibility with resist solvents and excellent photolithography performance with resolution down to 0.35 μm. No metal contamination was observed with this BARC when gate oxide integrity (GOI) testing was performed on different size capacitors.