Among the variety of dual damascene (DD) processes, the via- first approach has drawn much attention because of its reduced process steps and improved photolithography process window. The via-first process requires a layer of via-fill material to be applied beneath the photoresist layer. The primary function of this via-fill materials is to act as an etch-block at the base of the vias to prevent over-etching and punch-through of the bottom barrier layer during the trench-etch process. However, such materials also help to planarize the substrate and may limit back reflection from the substrate as well, helping to control the critical dimension (CD) of the printed features. Based on this understanding, our research efforts have been focused on the advancement of DD-applicable bottom antireflective coatings (BARCs). A series of novel planarizing DUV BARCs with full- via-fill properties and enhanced etching selectivity to resists have been developed. They showed good full-fill, void-free performance in 0.20micrometers vias having an aspect ratio of five, also sufficient top coverage i.e., enough coating thickness, low surface variation, and little thickness bias of isolated-via (1:10) area versus dense-via (1:1) area. The resist sidewall profiles with features sizes less than 0.20micrometers indicated that there was good compatibility of the BARCs with the resists. The thin film etching selectivity to commercial resists was about 1.2:1 under an Hbr/O2 atmosphere. A study of the BARCs described in this report allows further discussion of the impact of pattern density, feature size, and processing conditions on BARC coating performance.
The list of desired properties for a spin-on 193-nm BARC steadily increases. In response, crosslinkable polymers from different chemical families than the conventional acrylics and vinyls are being studied for applicability in preparing improved thermosetting BARCs. Alternate polymer platforms discussed in this paper include polyethers, polyesters, polyurethanes, and polysaccharides. A BARC that uses a blend or mixture of commercially-available polymers for the binder is highlighted and the product's performance is described. The BARC parameters that are discussed include film properties, flash point, optical data and reflectivity, solution and spin-bowl compatibility, plasma etching rate, resist profile, conformality, and metals content. Based on the test results outlined in this paper, the polymer blend BARC JM2218-56 is expected to advance towards commercialization.
Two organic, spin-on BARCs are in the small scale manufacturing phase -- with the goal being a 193-nm product optimized for commercialization. Chemistries of the BARCs are shown in this paper and performance of the two products relative to industry accepted needs is discussed. The thermoset BARCs, EXP98090B and EXP99001D, are prepared from hydroxy-functional, dye-attached acrylic polymers by adding an aminoplast and sulfonic acid catalyst. With select 193-nm resists, the BARCs give resolution of L/S pairs down to 0.12 micrometer. Plasma etch rates of both BARCs are comparable to those of 193-nm photoresists. Other BARC performance parameters that are discussed for the two products include: film and optical properties, conformality, simulated reflectance curves, spin-bowl compatibility, metals content, and defects.
Dual Damascene (DD) process has been implemented in manufacturing semiconductor devices with smaller feature sizes (<EQ 0.20 micrometer), due to increased use of copper as a metal of choice for interconnects. Copper is preferred over aluminum due to its lower resistance which helps to minimize the effects of interconnect delays. Via first DD process is the most commonly used process for manufacturing semiconductor devices since it requires less number of processing steps and also it can make use of a via fill material to minimize the resist thickness variations in the trench patterning photolithography step. Absence of via fill material results in non-uniform fill of vias (in isolated and dense via regions) thus leading to non-uniform focus and dose for exposure of the resist in the deep vias. This results in poor resolution and poor critical dimension (CD) control in the trench-patterning step. When a via fill organic material such as a bottom anti- reflective coating (BARC) is used, then the resist thickness variations are minimized thus enhancing the resolution and CD control in trench patterning. Via fill organic BARC materials can also act as etch blocks at the base of the via to protect the substrate from over etch. In this paper we review the important role of via fill organic BARCs in improving the efficiency of via first DD process now being implemented in semiconductor manufacturing.
A fast-etching broad band bottom anti-reflective coating (BARC) for photoresist applications at the wavelength of 365nm, 248nm and 193nm was developed. The new BARC formulated in safe solvents such as ethyl lactate and PGME exhibits wide spin bowl compatibility with various photoresists, and can be processed with common edge bead removal solvents. The optical properties of the new BARC are tailored for high contrast resist systems, with film optical density exceeding 4.2 micrometers at 365 nm, 7.5 micrometers at 248 nm and 8.5 micrometers at 193 nm. Most importantly, we have demonstrated plasma etch rates of the new coating in excess of 1.5-2.0 times that of conventional i-line and DUV photoresist. The compatibility of this material with multi resists at all three wavelengths will be discussed as well as trade-offs versus dedicated single wavelength BARC systems.
This paper presents the chemistries and properties of organic, spin-on, bottom antireflective coatings (BARCs) that are designed for 193 nm lithography. All of the BARCs are thermosetting and use dye-attached/incorporated polymers. A first generation product, NEXT, will soon be commercialized. NEXT is built form i-line and deep-UV chemistries with the polymeric constituent being a substitute novolac. This product provide outstanding resolution of 0.16 micrometers L/S with several 193 nm photoresists. Second generation chemical platforms under study include acrylics, polyesters, and polyethers with the 193 nm absorbing chromophore being an aromatic function. The performance of selected BARCs from the four platforms is described, including: optical properties, 193 nm litho, plasma etch rates, Prolith modeling data, spin-bowl and waste line compatibility, and ambient stability.
We report here the development of a fast-etching i-line bottom anti-reflective coating (BARC): EXP97002B. The new BARC is applied from a safe solvent system, exhibits wide spin bowl compatibility with photoresists, and may be processed with common edge bead removal solvents. The optical density of the new BARC is 6.15/micrometer at 365 nm (n equals 1.71, k equals 0.39). We have demonstrated plasma etch rates for the new coating in excess of 1.5 - 2.0 times that of conventional i- line photoresists. The coating system planarizes substrate topography, reducing resist film thickness variations and, thereby, resist swing. Feature coverage is still excellent, as evidenced by the ability of the new BARC to coat 0.7 micrometer vertical topography. The practical issues for implementing the new BARC in a manufacturing environment is also discussed.
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