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A dual hard mask concept for high resolution patterning has been evaluated with focus on highly selective etching processes for semiconductor manufacturing. The integration of thin SiO2 and ZrO2 hard mask materials enables highly selective patterning via plasma etch processes for future technology nodes. The patterning sequence is demonstrated for hole arrays with sizes down to 25 nm using a 50 nm thin resist which leads to the fabrication of trenches in silicon with aspect ratios up to 20:1. Alternative ZrO2 based materials were investigated with focus on surface roughness reduction since it influences the final line edge roughness (LER). Here Si-doped ZrO2 (ALD) was compared to the undoped and crystalline ZrO2 as main selective material.

The application of phasefluid based intelligent fluids® in the field of photoresist stripping was studied. Due to their highly dynamic inner structure, phasefluids penetrate into the polymer network of photoresists and small gaps between resist layer and substrate and lift off the material from the surface. These non-aggressive stripping fluids were investigated regarding their efficiency in various resist stripping applications including initial results on copper metallization. Furthermore intelligent fluids® have been evaluated on an industry standard high volume single wafer cleaner. A baseline process on 300 mm wafers has been developed and characterized in terms of metallic and ionic impurities and defect level. Finally a general proof of concept for removal of positive tone resist from 300 mm silicon wafers is demonstrated.

The fabrication of high aspect ratio silicon trenches (critical dimension < 100 nm, aspect ratio > 10:1) by dry etch processing has proven to be a challenge mainly due to limited etch selectivity of conventional hardmask materials to Si. Moreover, for future technology nodes the hardmask thickness will be limited by the thickness of the photoresist. This work focuses on a concept to enable the usage of very thin resist layers (< 100 nm) for patterning of silicon trenches by the integration of an unconventional hardmask stack consisting of SiO2 and ZrO2. Deposition of such material films has been investigated, as well as e-beam lithography exposure and finally pattern transfer by dry etching. Using this hardmask stack and 100 nm thin resist, the fabrication of 35 nm wide trenches with an aspect ratio of ~ 20:1 is demonstrated revealing a very high selectivity (> 100:1) of the ZrO2 layer to Si during the deep silicon etch. A silicon etch rate > 1.5 µm/min was achieved. The ZrO2 layer itself provides the main selectivity improvements of the final hardmask stack.

The concept of Main Chain Scission of photoresist polymers (MCS) is used to reducing the influence of molecular dimensions on the quality of photoresist patterns. Independent from the wavelength or lithography technique, the concept will raise in relevance as critical dimensions approach molecular dimensions. After the introduction of the MCS concept on last years conference of photopolymer science and technology, initial results are given in this paper to verify this concept.[1] Starting with polymer synthesis, after optimization of resist formulation and process conditions, ebeam patterns with the MCS resist and a commercial ebeam resist were generated. The patterns were compared with respect to their roughness. It was found, that lines printed in the MCS resist show a significant lower LER than the same patterns in the ebeam resist.

The usage of phase fluid based stripping agents to remove photoresists from silicon substrates was studied. Photoresists are required for many silicon based technologies such as MEMS patterning, 3D-Integration or frontend and backend of line semiconductor applications [1]. Although the use of resists is very common, their successful integration often depends on the ability to remove the resist after certain processing steps. On the one hand the resist is changing during subsequent process steps that can cause a thermally activated cross-linking which increases the stripping complexity. Resist removal is also challenging after the formation of a hard polymer surface layer during plasma or implant processes which is called skin or crust [2]. On the other hand the choice of stripping chemistry is often limited due to the presence of functional materials such as metals which can be damaged by aggressive stripping chemistries [3].

The usage of phasefluid based stripping agents to remove photoresists from silicon substrates was studied. Due to their highly dynamic inner structure phasefluids offer a new working principle, they are penetrating layers through smallest openings and lift off the material from the surface. These non-aggressive stripping fluids were investigated regarding their cleaning efficiency as well as contamination behavior to enable usage in semiconductor and MEMS manufacturing. A general proof of concept for the usage of phasefluids in resist stripping processes is shown on silicon coupons and BKM’s are given for different resist types. In addition a baseline process on 12inch wafers has been developed and characterized in terms of metallic and ionic impurities and defect level.

Organic photorefractive materials have attracted a lot of interest recently. Their optical response times of a few milliseconds, however, are not yet adequate for the desired commercial applications. We present an investigation on the correlation between the optical response time and photoelectric quantities, such as the hole mobility and the dispersivity of charge carrier transport.

A novel organic photorefractive composite system is presented consisting of the amorphous multifunctional low-molar mass compound DR1-DCTA, doped with C 60 as sensitizer and diisooctyl phthalate (DOP) as plasticizer. DR1-DCTA, a carbazole substituted triphenylamine with a covalently attached nonlinear optical azo chromophore unit has been synthesized in a 4 step reaction. The compound forms a stable glass. Its thermal, optical and electrochemical properties are discussed. Holographic experiments (2BC, DFWM) of the photorefractive composite exhibit a fast response time in the range of only 30 ms and a maximum gain coefficient of 90 cm –1 .

A variety of new functional materials based on triarylamines, such as low molecular weight glasses which possess hole conducting/photoconductive properties as well as amorphous bifunctional materials which combine photoconductive and non-linear optical (NLO) properties in one compound, have been synthesized. The new hole transporting glasses belong to the class of 1,3,5-tris(triaryldiamino)benzenes (TTADB). The hyperbranched structure and the large aryl groups attached as substituents lead to high glass transition temperatures (Tg) of up to 141°C in these compounds. The TTADBs do not recrystallize upon cooling from the melt, but form stable glasses. Cyclic voltammetry studies reveal multi-oxidation stages for these compounds of which the first oxidation is reversible. The HOMO energy values determined from CV for TTADB-1 and TTADB-2 are -4.82 and -4.94 eV, respectively. Light emitting diodes with the structure ITO/TTADB-2/Alq3/Al (where ITO=indium tin oxide) show high efficiency and large current carrying capacity. Further, bifunctional compounds have been synthesized in which a photoconductive moiety such as bis(carbazolyl)triphenylamine or bis(diphenylamino)triphenylamine is covalently bound to different NLO chromophores. Some of these compounds are thermally and morphologically stable amorphous materials, possessing Tg in the range from 85 to 122°C. Cyclic voltammetry measurements reveal that the HOMO energy values are between -4.81 and -5.45 eV. In photorefractive measurements using 40 µm thick samples, a diffraction efficiency of 27%, which corresponds to a refractive index modulation (Δn) of 3.5×10-3, a maximum two beam coupling gain coefficient (Γ) of 90 cm-1 and a response time of 40 ms were obtained.

This paper focuses on zirconia and TiN based metal-isolator-metal capacitors integrated in immediate vicinity to the Si substrate. A high capacitance density is aimed by significant area enhancement realized through silicon pattering. By material optimization the capacitors also withstand higher supply voltages and show excellent temperature and reliability performance independently of the 3D structure.

To fulfill the requirements of future technology nodes new resists with high resolution, high sensitivity and low LWR and LER respectively are needed. A new inorganic non-chemically amplified resist (XE15IB, an experimental resist provided by Inpria Corp.) was investigated. The resist is spin-cast from aqueous solution and is based on hafnium oxide. Metal oxide based resist as XE15IB supersede other resist materials due to its high etch resistance. 1, 2 This new material can be considered as a direct patternable spin on hard mask. XE15IB was processed in a 300mm complementary metal oxide semiconductor (CMOS) manufacturing environment and exposed on a 50 kV VISTEC SB3050DW variable shaped electron beam direct writer at Fraunhofer Center Nanoelectronic Technologies (CNT). The resist was evaluated in terms of contrast, sensitivity and resolution. The process characteristics required for CMOS manufacturing such as delay stability were also examined. Furthermore, by printing a large static random access Memory (SRAM) pattern (design CD of 22 nm), the exposure of a real application pattern was demonstrated.

In electron beam lithography, the electron scattering and the corresponding proximity effect highly influence the feature resolution. Especially for sub-100 nm features a compensation for this effect is needed. There are several methods of determination of the proximity parameters, which mostly are time-consuming and complex due to a need of an initial proximity effect correction and immense measurement effort. In this paper the checkerboard pattern is proposed to provide the opportunity for proximity parameter determination in a fast and easy manner without using a sophisticated CD-SEM metrology. The concept is illustrated by simulation and first experimental results are shown.

This paper is part of our continuing work on a new generation of more transparent, 157 nm resist platforms, which are based upon capping of fluoroalcohol-substituted, transparent perfluorinated resins (TFR) with a tert-butoxycarbonylmethyl (BOCME) moiety. Recent results indicate that by optimizing both resin structure and loading of photoacid generator and base additive a good compromise can be achieved between resolution power, dark erosion resistance, sensitivity and transparency at 157 nm. Specifically, it was found that a decrease in PAG (50% nominal loading) and base loading (75% nominal loading), coupled with optimization of the TFR resins to achieve higher transparency, gives the best compromise of properties. In this manner, resist systems with a transparency as low as 0.87 AU/micron were designed capable of resolving 60 nm 1:1 features, at a dose of 92 mJ/cm 2 (non corrected for sigma), using a strong phase shift mask, and a sigma of 0.3 on a Exitech 157 nm small field mini-stepper. This type of resist material has also been imaged with a larger field tool ( DUV30 Micrascan VII ) to give 80 nm 1.1.5 L/S features at a dose of 135 mJ/cm 2 employing using a Binary mask (σ=0.85). Finally, it was found that our BOCME-TFR based resist system can be used to transfer a 120 nm L/S pattern (imaged by 193 nm lithography) into a hardmask stack on top of silicon.

Several fluoro-substituted polymers consisting of acid cleavable methacryoic or cinnamic acid tert.-butyl ester compounds copolymerized with maleic acid anhydride derivatives were synthesized by radical copolymerization. Vacuum ultraviolet transmission measurements of the samples reveal absorbances down to 5micrometers -1 despite of the strongly absorbing anhydride moiety which serves as silylation anchor for the application of the Chemical Amplification of Resist Lines (CARL) process, one of the promising approaches for sub-90nm pattern fabrication. Some of the samples exhibit resolutions down to 110nm dense at 157nm exposure using an alternating phase shift mask. The feasibility of the CARL principle including the silylation reaction after development has been demonstrated with selected fluorinated polymer samples.

SUMMARY Thin film imaging is a possible solution for 157 nm and other NGL techniques in lithography due to DOF problems,absorbance and possible pattern collapse in thick resist films at line widths below 90 nm. We have modified the CARLbilayer process consisting of a thin imaging top resist with the option of silylation and a thick Novolac bottom resist tothe 157 nm wavelength. This work is part of the German BMBF project ,,Laserbasierte Ultraprazisionstechnik - 157 nm-Lithographie".We used a silicon free top resist (Si free CARL) for the CARL bilayer resist process to avoid silicon outgassing andirreversible contamination of the tool optics at 1 57 nm. The top resist polymer is a base polymer for our ongoing workof fluorination and therefore for resists with a higher transparency at 1 57 nm. In the first imaging experiments a film thickness of ca. 50 nm was applied. The silylation step between wet development of the imaging top resist and dry development of the bottom resist provides a high etch resistance in the final plasma process. A high silicon content inthe structures obtained by this treatment allows a structuring of up to 300 nm bottom resist with ultra-thin films of theimaging top resist (< 50 nm). The Novolac or PHS based bottom resist provides high etch resistance also for aggressivesubstrate etch processes.

An efficient method for the synthesis of a multifunctional dye conjugate containing an electrooptical merocyanine chromophore and a photoconducting triphenylamine electrophore is described. In the first step 4,4'-di(9-carbazolyl)-substituted 4"-hydroxytriphenylamine 7 is reacted with 2,3-dihydro-5H-oxazolo[3,2-a]pyrid-5-one (6) by dihydrooxazole ring opening leading to precursor 8 which could be converted to the bichromophoric conjugate 2 in a Knoevenagel condensation. UV/VIS spectroscopy and cyclic voltammetry of the bichromophoric compound 2 revealed optical and electrical properties that make such multifunctional dye conjugates highly promising for photorefractive applications.

Most photorefractive (PR) materials require plasticizers in order to decrease the glass transition temperature, allowing for orientational enhancement by the chromophores. Introduction of the plasticizer, however, alters not only the viscosity but also the photoconductive properties of the material. This can be shown by comparing two different plasticizers which were introduced into a bifunctional low-molecular-weight PR glass and into a polyfluorene guest-host polymer. The latter reaches response times down to 600 microsecond(s) at a writing intensity of 1 W/cm2. We have recently improved the concept of low-molecular-weight PR glasses. A suitable, photoconducting unit allows the synthesis of a bifunctional system with a glass transition of 22.6 degree(s)C. Therefore, no plasticizer is needed. The material is based on a triphenyldiamine (TPD) moiety to which a nonlinear-optical chromophore is directly attached. The system is the first representative of a whole class of TPD molecules and polymers for photorefractive applications.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We report on holographic investigations of several organic photorefractive materials based on monolithic low molar mass glasses. The addition of different plasticizing agents and the variation of three NLO-units prove to change the photorefractive performance and the thermal properties of the resulting compounds dramatically. Very fast holographic response times down to 2.5 ms could be reached at refractive index modulations of 6 10- and two-beam coupling gains of up to 140 cm-1.© (2000) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

A series of novel bifunctional cyclosiloxanes with pendant photoconducting and nonlinear-optical moieties was synthesized in a two step procedure. The variation of the spacer length between the siloxane ring and the functional carbazole and azo moieties leads to glass transition temperatures between 33 degrees C and 61 degrees C. These well defined low-molar mass compounds are characterized with regard to their chemical, thermal and electrooptical properties. Compared to commonly used guest-host systems crystallization of the chromophore dopants is diminished due to the covalent bonding of the azo-dye to the cyclosiloxane backbone.

Seven novel photorefractive glasses have been prepared in an effective four-step synthesis. The low molar mass glasses consist of a triphenylamine-core substituted with two carbazole moieties and a NLO-chromophore (NLO-DCTAs). In a second series of compounds (NLO-DATAs) the carbazole groups are replaced by diphenylamine. The compounds from stable glasses with Tgs of about 120 degrees C and 85 degrees C. The photorefractive properties such as the diffraction efficiency (eta) , the modulation amplitude of the refractive index (Delta) n, and the gain coefficient (Gamma) were determined by means of degenerate four-wave mixing and two- beam coupling experiments. We observed diffraction efficiencies of (eta) equals 90 cm-1. The samples have excellent properties with respect to optical quality and shelf-lifetime.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

We investigated polymeric materials based on polysiloxane (PSX), polymethylmethacrylate (PMMA), polyurethane (PU), as well as a triphenylamin-based glass (DRDCTA) with respect to their photorefractive properties. Electric-field dependencies of the two-beam coupling gain, diffraction efficiencies, refractive index amplitudes and holographic rise-times could be obtained by means of two-wave mixing and degenerate four-wave mixing measurements. The examined PSX polymer systems were composed of a photoconducting polysiloxane host doped with trinitrofluorenone (TNF) as a sensitizing moiety and various chromophores, namely, an azo derivative, a stilben derivative and a tolan derivative. Due to their comparatively low glass-transition temperatures T g , an orientational enhancement of the photorefractive properties was observed. Furthermore, the influence of photoisomerisation (based on trans-cis-trans cycles) on the holographical properties could be determined for the different chromophores. In addition, a class of fully functionalized polymers with azo chromophores and carbazole-units covalently attached to PMMA- and PU-backbones was synthesized. These systems show comparatively high glass transition temperatures of more than 80 degrees C. The third type of materials investigated is a glass of triphenylamin with attached carbazole and NLO-chromophore moieties. It has a glass transition temperature of 120 degrees C. For the high-T g materials, poling procedures--essential for the photorefractive properties--could be monitored in-situ by second-harmonic generation. Absolute values for the nonlinear Pockets coefficients χ (2) (-ω; ω, 0) have been obtained by electro-optical measurements.

In this paper we report on the synthesis of a number of photorefractive materials with high glass transition temperatures. We have developed a series of fully-functionalized polymethacrylates with both photoconducting and NLO-active moieties. Secondly, low molecular weight glasses based on triphenylamine and carbazole units together with different NLO-chromophores have been designed which show no tendency towards crystallization. We now report on the synthetic approach to these novel materials and their properties with regard to photorefractive applications.

Hydrogen silsesquioxane (HSQ) has interesting applications as an electron-beam resist and hardmask. In this work, HSQ was investigated with regard to the postcoat delay, isofocal dose for an optimum process window, a-beam proximity effect correction, and the molecular structure in order to better understand the processing. Several independent methods were set up and applied to characterize the structuring of HSQ with e-beam including contrast measurements, basedose-over-critical-dimension tests, the isofocal dose method, the doughnut test, and Fourier transform infrared analysis. HSQ was coated on 300 mm bare silicon wafers and exposed with a 50 kV variable shaped e-beam writer in the dynamic random access memory pilot line environment of Qimonda Dresden and Fraunhofer CNT. The postcoat delay showed no significant influence on the exposure results. A dose difference between the basedose and the isofocal dose was observed, which indicates a working point-in a suboptimal process window related to the poor contrast. The FTIR analysis showed a molecular structure change up to 600 mu C/cm(2). Finally, a point-spread-function for HSQ has been generated for the first time. In summary, the results from this detailed characterization show promise for a manageable process.

A number of organic glass forming starburst molecules have been synthesized and characterized with regard to their thermal and optical properties. Photorefractivity is observed and discussed within triphenylamine derivatives substituted with an NLO-chromophore. The tuning of glass forming properties in novel phenylquinoxaline glasses and their use as electron transport materials for OLEDs is presented.

A series of different fluorinated polymer platforms used for early and current 157-nm photoresists is investigated with regard to blanket etch properties and surface roughness. Besides methacrylic-based polymers applied for 193-nm lithography, fluorine containing norbornene homopolymers, fluorinated cycloolefines, and tetrafluoroethylene (TFE) norbornene copolymers are chosen. Etch rates in different plasmas used for several applications, such as poly, SiN mask open, and selective/nonselective SiO2 etch, are determined and compared to standard 193-nm platforms currently used for DRAM manufacturing. Looking at various base resins, significant differences can be found using HBr- or Cl2-based poly etch conditions and various fluorocarbon-based oxide etch chemistries. Up to 2.4 times higher etch rates in Cl2 and the different CxFy oxide etch recipes are observed for the highly fluorinated cycloolefines and the TFE norbornenes, showing a strong correlation between fluorine content and etch rate. After stress by different etch conditions, the polymer surfaces are characterized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). Surprisingly, the surface roughness of the methacrylic platforms and the norbornene base resin (determined by AFM) are found to be substantially higher than that of the highly fluorinated platforms. These results can directly be correlated to pictures obtained by optical methods (SEM).