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Application of photodecomposable base concept to two-component deep-UV chemically amplified resists

The use of photodecomposable bases (PDB) offers distinct benefits to the general lithographic performance, and in particular, to the stability of the latent image in positive tone chemically amplified deep UV resists (CAR). The PDB concept utilizes radiation sensitive basic compounds, such as triphenylsulfonium hydroxide (TPSOH), which are coformulated as additives to the resist formulation. In the exposed resist sectors the PDB is decomposed into neutral fragments, which do not interfere with the simultaneously produced acid from the photolyzed photoacid generator (PAG). In the unexposed regions the PDB remains active and effectively neutralizes acid molecules diffusing into these areas. The successful integration of the PDB concept into acetal-based three component systems has been described previously. Its usefulness for standard two component materials, consisting of a polymer partly reacted with acid-labile protective groups, such s t-BOC or acteal/ketal protected ploy-4-hydroxystyrene (PHS), and a PAG is investigated in this paper. The effects of the PDB on the latent image stability, and additional resist properties, such as transparency, sensitivity, contrast, standing waves, etc. are discussed in detail. Finally, a new high performance deep UV CAR material incorporating the PDB concept is presented.

High performance positive DUV photoresists AZ DX 1100P AZ, DX 1200P, AZ DX 1300P, AZ DX 2034P, AZ DX 2058p for advanced lithographic applications

An increasing number of DUV resists, which have taken considerable steps on the maturity curve, is available on the market these days. It becomes obvious that - similar to i-line application - there is not the universal resist giving the best fit for every aspect of DUV handling. Meanwhile this seems to find wide acceptance by the majority of the user community. Classifying major commercial PHS based resists according the protective group: acetal, t-BOC and acrylate type with the chemistry concept of low, medium and high activation energy may be distinguished. In order to satisfy specific customer needs Clariant have a commercially available family of AZ® DUV products. These recently developed products include on the positive resist side AZ® DX 1100P, AZ® DX 1200P, AZ® DX 1300P, AZ® DX 21134P and AZ® DX 2058P, all two component acetal-based systems. The details of this resist chemistry are described elsewhere 1 . Dose-to-print versus dose-to-clear ratio is about 2.4 indicating high contrast. Process parameters, as well as selected characteristics and performance items are highlighted in this contribution. AZ® DX 1100P is intended for use on weakly reflective substrates, such as bottom antireflective coatings (BARCs) of organic or inorganic nature. On AZ® BARLi, a BARC originally developed for i-line application, AZ® DX 1100P shows a lines and spaces resolution well below 0.2 μm. Depth of focus (DOF) amounts to 1.05 μm for 0.25 μm critical dimension (CD). Excellent post exposure bake (PEB) latitudes are found where CD change is below 1 nm/°C. Post exposure delay stability for CD 0.2 μm is better than 12 hours for amine concentrations at around 5 ppb. Good substrate compatibility is also found on TiN and Tungsten (W). AZ® DX 1200P is targeted for contact hole (C/H) printing. Besides an excellent sensitivity with the C/H dose to print at around 40 mJ/cm 2 for 0.96 μm resist thickness. C/H ultimate resolution goes down to < 0.2 μm. For CD 0.25 μm the DOF is determined to be greater than 1.2 μm. As far as the baking parameters are concerned, there is full processing compatibility with conventional diazonaphtoquinone/novolak based resists. This is also valid for AZ® DX 1300P, an allround resist, aimed for a wide range of applications on standard and highly reflective substrates. Evaluation highlights of AZ® DX 1300P include high sensitivity of around 20 mJ/cm 2 , excellent resolution down to 0.2 μm and a large DOF of 1.2 μm for 0.25 μm l/s. To respond to most advanced sub 0.2 μm CD needs AZ® DX 2034P comparable to AZ® DX 1100P addresses BARC and AZ® DX 2058P analogous to AZ®DX 1300P covers the remaining more general areas of use.

Acetal-based three-component CARs: a versatile concept to tailor optical properties of resists

Cost and yield effective IC fabrication requires the use of a large variety of substrates with distinct reflectivity, which may cause problems during the lithographic process either due to reflective notching and standing wave formation on highly reflective substrates, or trapezoidal resist patterns and deterioration of resolution, when a substrate with low reflectivity is employed. Reflectivity problems become more evident, when i-line radiation is replaced by DUV illumination tools. In addition, the non-bleaching nature of state-of-the-art chemically amplified resists further aggravates the reflectivity issues. It is therefore generally accepted that substrate reflectivity and resist transparency have to be closely matched to gain maximized lithographic performance, i.e., dissolution characteristics, resolution, depth-of-focus and exposure latitude. We have reported previously that poly-N,O-acetals act as effective dissolution inhibitors/promoters for PHS-based chemically amplified DUV resist materials. Alkylsubstituted poly(benzaldehyde-N,O-acetal)s are basically transparent in the 248 nm wavelength region, and therefore do not contribute to resist absorption. On the other hand, poly(naphthaldehyde-N,O-acetal)s are quite strong absorbants in the deep UV region. It was found that certain benz- and naphthaldehyde poly-N,O-acetal derivatives exhibit essentially identical inhibition and dissolution properties combined with similar cleavage kinetics. By both, physical mixing or co-condensation, of these materials, it is possible to adjust the optical resist absorption to precalculated values between approx. 0.30 - 0.80 micrometer MIN1 solely by poly-N,O-acetal selection without deterioration of other important resist properties. Basic chemistry, physico-chemical and optical properties of the resists are discussed in detail. Lithographic results including SEMs prove the versatility and efficiency of this approach.