The continuous studies for both the outgassing reduction and the sensitivity improvement by applying low outgassing
photo acid generator with a various kinds of polymer protection group were discussed in this paper. Further reduction of
the outgassing segments from the resist was demonstrated to achieve the total outgassing amount below the detection
limit of GC-MS (ca. less than 1E+10 molecules / cm2). Loading a large sized acetal group could be successfully reduced
the amount of the outgassing segments from polymer below the tool detection limit, which would be acceptable for a
high volume manufacturing tool usage. The development properties of PHS based bulky acetal polymers were measured
by changing molecular weight. The high dissolution rate contrast was obtained with the bulky acetel protected low
molecular weight polymer. A resolution capability study was carried out with micro exposure tool (MET) at LBNL and
Albany. The correlation between LWR through CD and DOF was measured by loading various amounts of quencher.
The resolution capability of newly developed EUV resist had been successfully improved by modifying both resist
polymer matrix and quencher amount optimization. It was possible to obtain 27.7nm lines with MET tool, where LWR
value at 35 nm L/S was 3.9 nm with reasonable sensitivity range.
In case of EUV lithography, resist material needs to be developed to improve high sensitivity and to minimize outgassing. The outgassing segments from resist were mainly from PAG decomposition. The new type PAG was synthesized by modifying cation group of the sulfonium salt. The sensitivity of the PAG could be enhanced by loading electron withdrawing group on the PAG, which has low volatility during EUV exposure. Then the newly developed PAGs were capable to reduce outgassing during EUV exposure maintaining high acid generating efficiency against EB and EUV exposure. The other approaches to improve the resist sensitivity and minimizing outgassing property were to design PHS based polymer platform with bulky acetal group. The various kind of acetal groups were simulated to determine the Van der Waals volume. The bulkiness of the protection group is effective to both a) increasing inhibition rate of the resist matrix and b) boiling points of deprotected group. The optimum protection ratio has been studied to obtain proper dissolution rate changes before and after exposure. The resist sensitivity is depend on the protection ratio of the bulky acetal group. By modifying PAG and optimizing bulky acetal group in the polymer, it is possible to minimize the amount of the outgassing segments during EUV exposure maintaining high resist sensitivity. The EUV exposure was demonstrated. It was observed that the resist had a high resolution capability in EUV exposure.
The device design rule is continuously shrinking toward optical resolution limit where k1 factor is below 0.3. The requirement for 193 nm photoresist below 90 nm node is quite challenging at the manufacturing phase. Using DI water rinse after development gives a significant amount of line collapse when the aspect ratio is over 3. To avoid line collapse, we co-developed special rinse solution for FIRM process with Tokyo Electron Ltd. Utilizing FIRM process, 90 nm dense line collapse was measured by CD SEM using focus-exposure matrices. The line collapse property has been observed using experimental 193 nm positive tone resist by varying monomer ratio of the polymer and process conditions. The surface property of the resist was also studied to investigate the interaction with rinse solution at the de-protected polymer region. However, a high surfactant concentration in the DI water rinse leads the swelling of the resist pattern profile. The resist component is the key to determine adequate surfactant concentration in rinse solution to minimize line collapse and pattern deformation
A high performance 193 nm resist has been developed from a novel hybrid copolymer based on a cycloolefin-maleic anhydride and methacrylate (COMA/Methacrylate) polymer system. A variety of copolymers have been synthesized from t-butyl norbornene carboxylate (BNC), t-butyl tetracyclo [4.4.0.1.2,617,10]dodec-8-ene-3-carboxylate (BTCDC), and 5-[2-trifluoromethyl-2,1,1-trifluoro-2-hydroxypropyl]-2- norbornene (F1) with different types of methacrylate monomers and maleic anhydride (MA). The effect of the monomers and the ratio of monomers in the copolymer on lithographic performance and etch rate has been studied. Lithographic evaluation of some of these polymers has shown resolution down to 80 nm using conventional 193 nm illumination and standard development conditions, particularly for semi and fully isolated lines. This paper will report the chemistry of the polymer platform and relative advantages of having certain monomers in terms of lithographic performance and line edge roughness.
We have studied 193 nm contact hole resists in view of resist components, process conditions and optical settings. Sidewall roughness was improved by optimizing photoacid generators. Side lobes were eliminated by applying higher post exposure bake temperature or modification of polymers. The influence of optical settings, types of masks and mask bias was discussed with simulation and lithographic results and guidelines for better resolution and iso-dense bias were proposed. The optimized formulation, AZAX1050P has a high resolution combined with a large depth of focus and an iso- dense overlap window (130 nm(NA=0.63) DOF 0.38micrometers Exposure latitude 10%).
Lithographic performance and line-edge roughness (LER) of several experimental high activation energy resists containing hydroxystyrene-co-styrene-co-t-butylmethacrylate terpolymers have been determined as a function of illumination conditions, polymer, photoacid generator and quencher composition, as well as process variations. Important lithographic properties, such as iso/dense bias, exposure latitude, may deteriorate upon minimization of LER. LER is largely affected by the changes of the optical settings, while material and process influences are less pronounced.
The development of a negative tone chemically amplified DUV resist consisting of a hydroxystyrene based copolymer, a melamine crosslinker, a photoacid generator (PAG) and certain amine additives is described. A response surface method was employed to investigate the general trends of formulation and process changes on the lithographic performance. Microbridging was eliminated by either increasing the PAG concentration or the application of lower prebake temperatures. The pattern profiles were optimized by the selection of a specific amine/ammonium hydroxide combination; the effects of individual amine components are discussed and a correlation with their structures is given. The application of monodisperse polymer materials generally improved the pattern edge accuracy. The optimized resist material has a resolution potential below 0.15 micrometers (NA equals 0.55) combined with a large depth of focus (> 1.0 micrometers 0.15 micrometers iso lines), acceptable iso-dense bias, and small sensitivity towards changes in the post exposure bake conditions.
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.
The newly developed e-beam negative tone AZ EX resist series has been designed for optical mask applications to produce 64MB DRAMs and related microdevices. The chemistry of AZ EX resists is based on chemical amplification employing the three major components: novolak, crosslinker, and radiation sensitive acid generator. The formulations have been optimized to diminish handicaps of most standard chemically amplified resists, such as delay time instability and line width variations upon post exposure bake temperature changes. The sensitivity of AZ EX series are smaller than 1.0 (mu) C/cm2 at Vacc equals 10 kV featuring a delay time stability of more than 24 hours with < 5% line width error at 1.25 micrometers pattern design. Using standard process conditions, the line width variations versus post exposure bake temperature changes are about 0.09 micrometers / degree(s)C in EX22-N, and 0.07 micrometers / degree(s)C in EX24-N, respectively.
Walter Spiess, Thomas Lynch, Charles Le Cornec, Gary Escher, Yoshiaki Kinoshita, John Kochan, Takanori Kudo, Seiya Masuda, Thierry Mourier, Yuko Nozaki, Setha Olson, Hiroshi Okazaki, Munirathna Padmanaban, Georg Pawlowski, Klaus Przybilla, Horst Roeschert, Natusmi Suehiro, Francoise Vinet, Horst Wengenroth
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.
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.
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.
KEYWORDS: Photoresist materials, Semiconducting wafers, Polymers, Picture Archiving and Communication System, Lithography, Diffusion, Deep ultraviolet, Coating, Absorbance, Scanning electron microscopy
This paper presents some methods for the investigation of delay time I3 induced effects typical of an advanced acetal-based photoresist, and strategies to improve the latent image stability. Dissolution rate monitoring was used to investigate the increasing formation of a surface inhibition layer with extended intervals I3. The impact of certain additives, the application of a protective coating (AZR Aquatar), and modified process conditions on the inhibition layer were studied in detail. The photoacid induced acetal cleavage was monitored by UV-spectroscopy (248 nm). Upon KrF excimer laser irradiation the resist absorbance increases, due to the progressing formation of a strongly absorbing aldehyde fragment. SEM pictures confirm a linear relationship between the efficiency of the acetal cleavage and acid diffusion into unexposed resist areas. Acid evaporation during PEB was determined by a novel method, the so-called Sandwich `Blue' Test. Interpretations of the experimental results and some optimization strategies are given.
E-beam/x-ray resist AZ-PN is relatively insensitive to process delay times of up to 24 h within the experimental error. Beyond this, deviation from the designed pattern size occurs due to delay times especially between exposure and post exposure bake. In the present paper an attempt has been made to evaluate the influence of humidity, prebake conditions, and overcoat materials on the sensitivity of AZ-PN to identify the reasons for the delay time (exposure - PEB) effect on the image transfer. Acidic overcoat material was used to eliminate the scavenging effect of basic impurities present in the clean room environment and prebake conditions were varied to change the residual solvent content of the resist film. It was observed that among the factors studied, humidity or moisture played a significant role. For instance, when the wafers were stored at 86% humidity the sensitivity (at 50% normalized film thickness) decreased from 7 (mu) C/cm2 to 13 and 19 (mu) C/cm2 for 48 and 96 h, respectively, while the decrease was only from 7 (mu) C/cm2 to 9 (mu) C/cm2 at 46% humidity for a delay time of 48 h. Under identical delay times, the higher the humidity, the higher the decrease in sensitivity. Use of overcoat materials decreased the overall sensitivity of the resist but did not influence the delay time behavior. Similarly, an increase in the prebake temperature from 80 to 100 degree(s)C or performing the prebake under vacuum at 90 degree(s)C for 30 minutes had no effect on the contrast curves. It was inferred from the results that if humidity is controlled, process delay time latitude of AZ-PN can be further improved.
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