Walter Spiess

Delay-time stable chemically amplified deep-UV resist

This paper describes a newly developed acetal-based positive tone deep UV photoresist called DX 46. The material consists of a 4-hydroxystyrene/4-hydroxy-3-methylstyrene copolymer, a polymeric dissolution inhibitor, and a bleachable diazo-photoactive compound. Each of the three compounds is specially designed to fit to each other for high performance sub-halfmicron resolution. The main idea is the use of a poly-N,O-acetal for dissolution inhibition which undergoes efficient acid catalyzed bond cleavage that produces strong dissolution promoting fragments in the exposed area. We determined the activation energy for hydrolysis reaction of our polyacetal to be 10 Kcal/mol. The radiation induced acid catalyzed hydrolysis reaction starts right after exposure and is accomplished by a mild post exposure bake at low temperature. This resist system is not sensitive to airborne contamination and no charcoal filtered air or diffusion barrier top coats are necessary for T-top free performance.

Progress in DUV resins

Starting from general arguments on the relation of polymer structure, transparency at 248 nm, resin hydrophilicity and resist dissolution characteristics, binder systems for novel DUV resists are presented, and the results of their lithographic evaluation are discussed. Phenolic polymers studied include homo- and copolymers of 2-, 3-, and 4- hydroxystyrenes and of their alkyl substituted derivatives for three- component systems, as well as 2- and 4-hydroxyphenylmethacrylates for use in two-component t-BOC-type resists. As an alternative nonphenolic resin, the performance of a maleimide/styrene copolymer in a two- component system is discussed.

Application aspects of a positive tone deep UV resist

Abstract Current state of process capabilities and performance items of a recently developed chemically amplified positive tone deep UV (DUV) resist is presented. The material is based on three components: an α, α-bis (arylsulfonyl) diazomethane as phtoacid generator (PAG), an oligomeric N,O-acetal as dissolution inhibitor and a poly(vinylphenol) as matrix resin. Lithography aspects being of general interest to the process engineer such as resolution, linearity, exposure and development latitudes, depth of focus, thermal resistance and use of top antireflective coating (TARC) AZ Aquatar are addressed. Furthermore, progress in delay time stability is discussed.

DN 21, DN 41: negative-tone photoresists for deep-UV lithography

Advanced negative photoresists for both KrF-excimer laser lithography (DN 21) and deep-UV broadband irradiation (DN 41) have been investigated. The materials are based on the well established chemistry of an acid-sensitive melamine derivative as the crosslinking species, a phenolic polymer containing 3-methyl-4-hydroxystyrene and 4-hydroxystyrene units, and an efficient photoacid generator. This paper briefly reviews the chemistry of DN 21 and DN 41 and concentrates on some selected lithographic performance parameters. The effects of various process conditions on resist performance have been examined, especially with respect to photosensitivity, contrast, and resist profiles. DN 21/DN 41 show an excellent delay time behavior between exposure and post exposure bake and are insensitive to environmental contaminants. An optimized process gives a resolution of 0.30 micron lines and spaces using a KrF-excimer laser stepper. A good linearity down to 0.35 micrometers and depth of focus values of clearly above 1.0 micron for 0.36 micrometers lines and spaces is shown. Other important factors for the lithographic performance, namely the 3-methyl-4-hydroxystyrene/4- hydroxystyrene ratio, the polymer/crosslinker ratio, and the concentration of photoacid generator is discussed as well. In particular, metal-ion and surfactant free standard developers yield highly vertical resist sidewalls without any scumming, bridging effects or residues between the resist lines. Dry etch properties of the material are found to be equal to conventional positive systems, while the thermal stability is superior.

Optimization of an advanced positive tone DUV photoresist towards 150 nm and beyond

This paper reports on the results of the use of resolution enhancement techniques in combination with an advanced deep ultraviolet (DUV) photoresist on an ASML PAS5500/300 stepper (maximum numerical aperture (NA) = 0.63. The performance of 0.15 and 0.13 @mm features will be evaluated using optical proximity correction (OPC) and an alternating phase-shifting mask (PSM) and these results will be compared with exposures with a binary mask. Two different resist thicknesses will be compared: 450 and 600 nm.

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.

Structure-property relationship in acetal-based chemically amplified three-component DUV resist

AZ DX series are chemically amplified, three component resists based on a poly(4-hydroxystyrene-co-3-methyl-4-hydroxystyrene) matrix resin, a poly(N,O-acetal) dissolution inhibitor, and a bis(arylsulfonyl)diazomethane acid generator. The previously described AZ DX 46 is an environmentally and delay time stable, high performance resist capable of lineating structures down to 0.23 micrometers . The material contains a photoactive base to reduce the delay time effects. In this paper the influence of styrene units in the matrix resin, and some new polyacetals on the performance of the resist in comparison to the above mentioned standard formulation AZ DX 46.

Substituted polyhydroxystyrenes as matrix resins for chemically amplified deep-UV resist materials

Abstract Substituted poly(4-hydroxystyrene)s provide an interesting source of film forming, deep UV transparent, aqueous alkaline developable polymers with a broad potential for modification of their chemical and physical properties. After a review of their synthesis and physical properties, selected examples of their use in chemically amplified resist systems, both positive and negative, will be presented.

Advanced photoresist for high-throughput i-line stepper applications

The use of i-line photolithography is finding increased importance in generating todays advanced semiconductor devices. The requirements in this area have led to the recent development of wide field i-line steppers whose large field sizes permit higher device throughput. The introductions of these wide field i-line steppers generate additional demands on the photoresist used in the manufacturing process. This paper describes the development of an advanced i-line photoresist for use in high-throughput applications. The requirements of this photoresist are high photospeed of the order of 75 mJ/cm2 to achieve targeted throughput requirements at low lamp power densities, high resolution of approximately 0.80 micrometers at NA equals 0.24 to satisfy device critical dimension requirements, and high resistance to thermal flow to permit further processing stages. The photoresists formulation and processing were optimized to produce the desired performance characteristics. Exposure, focus latitude, photosensitivity, and resistance to thermal flow were determined and correlated with resin dissolution characteristics, relative photosensitizer concentration, softbake and post exposure bake temperatures.

Evaluation results for the positive deep UV resist AZ DX 46

This contribution emphasizes resist application site by communicating lithographic results for AZ DX 46, obtained using the GCA XLS 7800/31 stepper, NA equals 0.53, equipped with krypton fluoride excimer laser ((lambda) equals 248 nm), model 4500 D, as exposure source, delivered by Cymer Laser Technologies. As far as delay time experiments are concerned ASM-L PAS 5500/70 stepper, NA equals 0.42, was used in combination with Lambda Physik excimer laser, model 248 L.