Extending the resolution capability of 193nm lithography through the implementation of immersion has created new challenges for ArF B.A.R.C.s. The biggest of which will be controlling reflectivity over a wider range of incident angles of the incoming imaging rays. An optimum B.A.R.C. thickness will depend on the angle of incidence of the light in the B.A.R.C. and will increase as the angle increases. At high angles different polarization have different optimum thicknesses. These confounding effects will make it increasingly difficult to control reflectivity over a range of angles through interference effects within a single homogenous B.A.R.C. Unlike single layer B.A.R.C.s, multilayer B.A.R.C.s are capable of suppressing reflectivity through a wide range of incident angles. In fact, remarkable improvements in antireflective properties can be achieved with respect to CD control and through angle performance with the simplest form of a multilayer B.A.R.C., a dual layer. Here we discuss the attributes of an all organic dual layer B.A.R.C. through simulations and preliminary experiments. One attribute of an organic over inorganic B.A.R.C. in high-NA lithography is its ability to planarize topography. ArF scanners designed to meet the needs of the 45nm node will have a very small depth-of-focus (DOF) which will require planar surfaces.
So far the IC industry is using dyed resist and TARC for the implant layer lithography. However, this approach cannot provide the necessary CD control for the 65nm node and below. One could use organic BARC to improve CD control but the dry etching process can cause substrate damage and also add considerable expense to the process. Cox et al at Brewer Science have reported some wet developable BARCs with TMAH soluble polymers. However the development is isotropic for these materials and it is difficult to control the development process for profile shape and across wafer uniformity. In this paper we describe new developable KrF and ArF photosensitive developable BARCs (DBARCs) that use the concepts of positive chemical amplified resist concept. These DBARCs have significant advantages over the conventional BARCs and also over processes using TARC. These new DBARC provide a large pattern collapse margin and a good process window.
We will report in this study on the process evaluation of the combination of Clariant KrF and ArF resists and DBARCs. As the DBARC itself is also photosensitive the matching of the sensitivity with resist is important. The KrF DBARC and resist combination gives 180nm lines and spaces with a good process window. This meets the requirements of 65nm implant processes.
As the semiconductor industry sails into the 100nm node and beyond, enabled by the integration of ArF lithography, new Bottom Antireflective Coatings (B.A.R.C.s) are required to address challenges associated with this new technology. Of these challenges, higher etch rates and better compatibility with the over coated resist are of central importance. New polymer platforms and additives in B.A.R.C. formulations will be required to overcome these challenges. The intent of this publication is to introduce our newly developed B.A.R.C.s designed to addresses the challenges of ArF lithography. All are currently available for integration into mass production of sub 100nm integrated circuit devices.
Due to miniaturization of semiconductor devices, ArF (193nm) lithography is likely expected to be used for sub 100nm regime. For sub 100nm devices, high NA (>=0.70) exposure tools and various strong off-axis illumination (OAI) conditions should be used. But unlike KrF (248nm) lithography, resist pattern collapse becomes one of the most serious problems in ArF lithography. In order to solve pattern collapse problem, thin resist process is generally introduced but its poor etch resistance is an obstacle for being applied in real production process. Due to this reason, new kinds of organic BARC materials are investigated and optimized to avoid pattern collapse. As mentioned, the most important issue in ArF organic BARC is believed to be the pattern collapse problem. A number of organic BARCs were made by varying polymer, cross-linker, thermal acid generator, and additive. We tried to analyze the key factor in terms of pattern collapse. This paper is to compare the various elements of the organic BARC formulation and to discuss what brings and causes pattern collapse.
To have excellent compatibility with ArF resists is the goal in development of bottom antireflective coatings (B.A.R.C.) for 193nm lithographic application. We need to be able to adjust chemical compatibility and optical properties of ArF B.A.R.C. to accommodate various film stacks. We need to deliver ArF B.A.R.C. materials with excellent coating uniformity, long shelf life and ultra-low defect level. In the meantime, we also need to improve etch rate of the ArF B.A.R.C.s for shorter etch time. In this paper, we will focus on our recent efforts to optimize the organic ArF B.A.R.C.s' compatibility with ArF resists in the areas mentioned above.
Full and/or partial filling of 193 nm antireflective materials in contact holes is required for dual damascene applications. One of the major challenges for via filling is to minimize various fill bias associated with via size, via pitches and wafer size to an acceptable level. Toward this aim, various formulations were prepared and tested on different types of wafers using different processing conditions. It has been found that both the properties of the filling materials (e.g., molecular weights, glass transition temperatures, etc.) and processing conditions (e.g., spinning speed, dispense modes, baking temperatures, etc.) affect the filling behaviors. This paper presents our recent progress in the development of 193 nm B.A.R.C. materials designed for the dual damascene process. Through screening of the B.A.R.C. materials and optimization of the processing parameters, we have successfully developed two types of B.A.R.C. materials, namely, AZ EXP ArF-2P1 and AZ EXP ArF-2P5A, both of which show good filling performance.
The 'via first-trench second' dual damascene technology is currently being explored by several major semiconductor manufacturers due to lithography constraints of printing small contacts on extremely non-planar topology (trench first technology). Typical via holes are 0.30 - 0.50 micrometer and 0.18 - 0.25 micrometer with aspect ratios of 3 to 6 for i-line and DUV exposures, respectively. The novel approach utilizes an organic material to fill via holes to a desired level with some planarization of the topographic pattern. Numbers of novel polymers have been synthesized and evaluated to fulfill the requirements for the dual damascene process. These polymers showed good coating and planarizing properties. By modifying the formulations such as polymer molecular weight, viscosity, solvents, and cross linker and thermal acid generator additives, as well as dispense and casting process conditions, the polymers were able to fill the via holes in 20 to 80% with good fill profile. Further, these polymers were incorporated with chromophores, which are highly absorptive at 365 nm and 248 nm wavelength. Similar to the bottom antireflective coating, these polymer coatings can effectively reduce or eliminate substrate reflection, swing effect and other problems caused by thin film interference. Our progress in this study has led us to the development of AZR EXP HERBTM B.A.R.C. for 365 nm exposure and the commercialization of AZR EXP KrF 17B 80 B.A.R.C. for 248 nm exposure. This paper will focus on development and process modification of these novel materials.
The present paper discusses theory, design and properties of bottom anti-reflective coatings (BARCs) for deep UV and i- line applications. All BARCs are interference devices, and as such their optical constants are optimal only for certain combinations of thickness and the real and imaginary parts of the refractive index. Maps of the optimality conditions in the parameter space will be provided. The design of BARCs for various exposure wavelengths involves choosing the right dye molecules capable of highly absorbing at the particular wavelengths and optimizing the etch rates of the resulting film sand fine tuning the formations for best lithographic performance. At an exposure wavelength of 365 nm, dye compounds such as amino aromatic or azo type compounds can be used, for 248 nm it is necessary to use fused rings such as anthracene to have sufficient absorption, and in the case of 193 nm exposures simple benzene or phenolic compounds exhibit the required d absorbance. Since the dye molecules are invariably aromatic or fused rings, it is necessary to balance the absorption property versus the etch rate by incorporating non-aromatic moieties. Further, the BARC formulations need to be free from intermixing, formation of foot or undercut in order to obtain fine resist patterns. Our development efforts on BARCs have led to the AZ EXP ArF, KrF and BARLi series of BARCs designed for 193, 248 and 365 nm wavelength exposures, respectively. Lithographic data of some of these products will also be presented with the emphasis on the AZ EXP ArF-1 material designed for 193 nm exposure.
Dye compounds are commonly used in photoresists as a low cost and effective way to control swing and/or standing wave effect caused by thin film interference as well as reflective notching by reflective light from highly reflective substrate and topography. Convention dyes are typically a monomeric compound with high absorptivity at the wavelength of exposure light and compatible with the resist system selected. Because of the monomeric nature, conventional dyes are relatively low in molecular weight hence their thermal stability and sublimination propensity has always been an issue of concern. We recently synthesize several highly thermal stable diazotized polymeric dyes. Their thermal properties as well as compatibility with resist system were investigated. The impact of polymeric dyes on the resists lithographic performance, swing reduction and reflective notching control are discussed.
The newly developed AZ BARLi II coating material is a photoresist solvent-based bottom antireflective coating (BARC) for i-line lithographic application. The coating material has good compatibility with common edge bead removal solvents such as ethyl lactate, PGME, or PGMEA mixed with ethyl lactate or PGME. To evaluate the BARC material, its chemical compatibility with common EBR solvents has been tested by several analytical techniques including liquid particle counts and surface defect studies. Both top and bottom EBR dispense processes have been investigated and optimized. Improvements on edge roughness, visual cleanliness, and the BARC coating buildup at the edge will be discussed in this paper.
A number of polymeric azo dyes was synthesized in our laboratories in the course of developing and studying i-line bottom antireflective coating materials. The key step in the synthesis involved formation of a diazonium salt intermediate which is a highly energetic species and can quickly convert to a couple of by-products, depending on the reaction medium such as solvent, temperature, time, and acidity. It is important to understand the mechanistic insight and compositional changes during the course of the reaction. ASi ReactIRTM 1000 reaction analysis system was used as the on-line monitor to follow such complicate process. By using this technique, we were able to obtain high quality kinetic data for thermal stability study of the intermediate, gained good understanding of reaction mechanism, optimized the synthesis process effectively, and achieved good control of reaction yield. The in-situ FT-IR technique proved to be a powerful tool for monitoring and controlling such a process. The highly absorptive polymers synthesized by the optimized process showed good consistency of the overall lithographic performance.
The use of bottom antireflective coatings (BARCs) as a means for controlling substrate reflectivity and thin film effects, has become commonplace in today's wafer fabs. In an effort to simplify process integration, reduce environmental impact, and reduce processing costs, some next generation organic BARC materials have recently been introduced which are formulated with photoresist compatible solvent systems. This study examines the process effects of converting from the cyclohexanone based AZTM BARLiTM anti-reflective coating, to the recently introduced PGME/Ethyl Lactate based AZTM BARLiTM II anti-reflective coating. We will present a comparison of the optical properties of the two products, and examine i-line lithographic process effects including process latitudes, CD distributions, and coat defects, as well as post etch CD distributions, and dye sublimation during cure.
AZTM BARLiTM II materials are used as highly absorptive bottom antireflective coatings (BARC) for i-line lithographic applications. The BARC formulations consist of polymer-bound dyes with the additives formulated in photoresist compatible solvents, containing none of monomeric chromophores, and showing excellent coating uniformity. We have continued to study the functional performance of the BARC materials on swing reduction, lithography, coating surface defect, thermal stability, forced aging behavior, etc. Strategy of formulations and recommendations on standard processing conditions will also be discussed.
We recently synthesized and studied a number of highly absorptive diketo azo dyes. These materials, existed in the hydrazo tautomeric forms, showed high extinction coefficients, typically (epsilon) approximately equals 25,000 - 39,000 at 365 nm. They also exhibited good solubility in common resist casting solvents such as propylene glycol monoethyl acetate (PGMEA) and ethyl lactate. The thermostability of the materials was investigated. The impact of these diketo azo dyes on i-line resist performance in terms of swing reduction, reflective notching control and lithographic performance is discussed.
In lithographic processing, implementation of a bottom antireflective coating can reduce or eliminate reflective notching and swing effects, thereby improving linewidth (CD) control. We have recently synthesized a series of novel polymeric dyes and evaluated them as bottom antireflective coatings for i-line lithographic applications. This work has led to the development of the BARLiTM II commercial bottom coat material. The BARLiTM II films show high absorbance at 365 nm and excellent coating uniformity. They are tailor- made to yield the optimum values for refractive indices (n and k) for i-line which ensures minimum reflectivity and maximum swing reduction for photoresist layers. BARLiTM II materials are formulated in photoresist compatible solvents to simplify the EBR process and to be environmentally and user friendly. Data presented in this paper also include BARLiTM II thermal stability, resist intermixing test, etch selectivity, swing reduction, lithographic performance, and step coverage profiles.
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