μThe emergence of adaptive and compact optical and optoelectronic devices, including flexible electronics, wearable displays, and solar panels, has necessitated the use of flexible and fracture-resistant substrates. High refractive index (HRI) polymeric coatings are being explored as promising alternatives to traditional inorganic thin films. In this study, three pure organic platforms were developed that offer tunable refractive indices (1.6 to 1.8 at 550 nm) and high light transmission (>98% at 400 nm for a 2-μm film). These HRI polymers demonstrate excellent compatibility with common processing solvents such as PGMEA, PGME, and acetone, as well as high thermal resistance with a Td of 300-370°C. Furthermore, an extended high-temperature baking study revealed the thermal and optical stability of our HRI polymer coatings, with less than 5% film thickness loss and less than 1% changes in optical properties. Additionally, we have developed photo-imageable formulations based on these HRI polymers, which can yield well-defined small features (<5 Θm) through i-line exposure.
Multilayer lithography is used for advanced semiconductor processes to pattern complex structures. As more and more procedures incorporate a high-temperature process, such as chemical vapor deposition (CVD), the need for thermally stable materials increases. For certain applications, a spin-on carbon (SOC) layer under the CVD layer is required to survive through a high-temperature process. Additionally, these materials are sometimes desired to planarize the underlying topography. Designing organic films that have high-temperature stability while also allowing for good planarization is a challenge. Rigid polymers are typically very stable, but planarizing materials are normally highly flexible, so the trade-off between properties has to be carefully designed. The materials presented in this paper are stable up to 500°C, soluble in the solvents commonly used in the semiconductor industry, provide void-free fill in high-aspect trenches, and have excellent planarization properties. The coated film has very low shrinkage through the bake temperature and is stable at high-temperature conditions. The planarization on topography in the range from local distance (a few microns), to global distance (a few hundred microns) is equivalent to our best low-temperature SOC.
In this study, we have developed a new set of cyan, magenta and yellow (CMY) dyed color filter materials to meet the need of digital photography applications. These new color filter materials consist of a dye, a photo sensitive polymer binder, photo initiators, and acrylic monomers in addition to safe solvents such as propylene glycol methyl ether (PGME) which allow deposition of thin film layers by standard spin-on coating techniques. CMY materials share many desirable properties with standard photoresists, e.g., excellent coating quality, thin film uniformity, and good adhesion to semiconductor substrates. They work as negative resists and are sensitive to i-line UV light with photo speed of 300 mJ/cm2 and below. We have shown, for example, that a 1 micrometers film exposed and developed will exhibit high- resolution feature sizes of 3 micrometers pixels and below. These CMY materials have excellent thermal and light stability and good color characteristics.
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.
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.
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.
A new bottom antireflective coating (BARC) for 248 nm lithography is described. The new coating has an optical density of approximately 10/micrometers (k equals 0.41 and n equals 1.482) and plasma etches at rates higher than that of DUV resists depending on the etch conditions. Coating conformality is superior to older generation BARCs, also contributing to improved etch dynamics. Excellent 0.25 micrometers features have been obtained with ESCAP, Acetal and t-BOC type photoresists. The new BARC is spin coated from safe solvents and is spin bowl compatible with EBR and photoresist solvents.
New bottom antireflective coatings (BARCs) for 193 nm lithography have been recently developed by Brewer Science Inc. Copolymers of benzyl methacrylate (or benzyl acrylate) and hydroxypropyl methacrylate have been synthesized and used as a main component in 193 nm BARCs. The acrylic copolymers have strong absorbance at 193 nm UV light wavelength. The 193 nm BARCs were formulated in safe solvents such as ethyl lactate and formed by spin-on coating process. Thermosetting of the 193 nm BARCs limited their intermixing with photoresists. These 193 nm BARCs had optical density of about 10 micrometers -1, k equals 0.35, and n equals 1.81. Preliminary oxygen plasma etch rates were > 1.5 times DUV resists. Good profiles at small feature sizes (< 0.20 micrometers ) were achieved with tested photoresists.
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