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.
So far, there are still many unknown phenomena on the interface of RELACS/resist during mixing bake (MB) processing. Knowing the precise quantitative interaction of these phenomena is significantly important to understand RELACS coating in order to attain much finer contacts as well as spaces with conventional optical lithography. Furthermore, more clear understanding of acid diffusion about RELACS/resist provides us more explicit design concept to increase the shrinkage of RELACS coating for 193nm lithography. In this study, we studied the differences of acid diffusion characteristics between 248nm and 193nm chemically amplified resists with various thermal acid generators (TAGs) in aqueous polymer coating. The diffusion phenomenon from resist to aqueous polymer coating is strongly correlated to the intrinsic diffusion characteristics of both resists. This study also revealed that the quantitative structure properties of organosulfonic acids generated from TAGs affects on the diffusion phenomena from resist to RELACS coating.
The IC industry is moving toward 90nm node and below. The CD size of implant layers has shrunk to 220nm. To achieve better CD uniformity, dyed KrF resist and top anti-reflective coating (TARC) are commonly used in advanced photo process of implant layers. It’s well known that bottom anti-reflective coating (BARC) has better reflection control over TARC. However, dry etching process is required if typical organic BARC is applied to photo process of implant layers. It is undesirable for two reasons. The first reason is the substrate damage caused by plasma etching could affect the device performance. The second reason is higher cost due to additional processing steps. In order to overcome those two shortcomings, developable BARC (DBARC) is introduced. It is a new type of BARC, which is soluble to developer, TMAH solution, in the resist development step. There are some reports on the developer-soluble KrF BARC. Most of them are polyamic acid and their solubility to alkline could be adjusted by changing bake condition. However, its development is isotropic, which make it difficult to get a vertical profile. Therefore, we have developed a photosensitive developer-soluble BARC (DBARC) which is anisotropic after exposure and thus results in a nice vertical profile. The photosensitive DBARC utilizes the same concept as chemically amplified resist. It has acid-cleavable groups in the resin and PAGs in the formulation. The photosensitive DBARC turns soluble to TMAH developer after exposure and resist PEB. The solubility difference caused by exposure makes developing process anisotropic and thus improves profile control. In this article, we will report the evaluation results of various combinations of KrF resists and DBARC for implant layers. Since both the resist and DBARC are photosensitive, matching of the photo speeds of them is essential. The amount and type of PAG in both the resist and the DBARC play a very import role. Finally, the optimized combination showed acceptable lithography process window and good CD uniformity over topography.
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 AZ<SUP>R</SUP> EXP HERB<SUP>TM</SUP> B.A.R.C. for 365 nm exposure and the commercialization of AZ<SUP>R</SUP> 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.
Bottom anti-reflective coatings (BARC) are useful to suppress the problems associated with reflection. In addition to matching the basic properties such as strong absorption at the exposure wavelength, and high etch rate, a commercially successful deep UV BARC material should be adaptable to as many chemically amplified resists as possible. A photoresist solvent compatible organic BARC material needs to have a minimum of two functions i.e., a dye to control the reflection, and a hardening agent or cross-linker to avoid intermixing with the resist cast on it. The dye and hardening components can be included to the BARC formulation in the form of additives or as an integral part of the polymer. We have designed novel BARC materials containing the dye and hardening function in the same polymer. Optionally, a third function can be incorporated to optimize the etch and solubility characteristics.