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In this paper, the feasibility of a large area exposure for the manufacturing of a NIL master (silicon wafer) dealing with a long writing time is shown. Fraunhofer CNT succeeded in a 355h exposure with a variable shaped e-beam using a commercially available positive tone chemically amplified resist. The wafer has been evaluated in terms of resist contrast and stability, CD uniformity, linearity, pattern quality and defectivity. Electron beam tool parameters like Wehnelt voltage and stage temperature have been analyzed. Different writing strategies and concepts will be considered to optimize the exposure and minimize stitching error defects.

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.

Electron beam direct write (EBDW) provides high resolution for device and technology development. A new variable shaped beam system with improved electron optics was introduced, which features the capability for the 32nm node. Because of the limited resolution of commercially available chemically amplified resists at this node, it is important to determine a stable and optimum resist process window. To compare a process window under different premises, a universally applicable and low error-prone method is needed. The isofocal dose method is investigated with regard to these properties for its use in EBDW. Experiments were performed on 50kV variable shaped electron beam direct writers using the new electron-optical column SB3050 DW (Vistec Electron Beam GmbH). Exposures are performed at different sites in Dresden (Fraunhofer CNT/Qimonda Dresden), Jena (Vistec) and Stuttgart (IMS Chips); also patterns are exposed on different layer stacks at one site. The strong need for a process window can be fulfilled by the isofocal dose method, which will be shown by contour plots.

When using electron beam direct write for patterning, resist selection (positive or negative) plays an important role. This is because writing time for shaped beam machines is proportional to the mean density of exposed shapes. There is an optimum with respect to writing time when using either the direct exposure or the complementary exposure with reversed resist tonality. Switching from positive to negative resist or vice versa has an impact on writing time. In this paper, we derive the fundamental differences on CD accuracy when using direct or complementary exposure, which is given by the local registration error. Additionally, a simple method is developed to measure this local registration error by simple CD SEM measurement of 1:1 line/space patterns.

Further work is described 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. By optimizing both resin structure and loading of photoacid generator and base additive a good compromise can achieved between resolution power, dark erosion resistance, sensitivity and transparency at 157 nm. In this manner, resist systems with a transparency as low as 0.87 AU/micron were designed capable of resolving 55 nm 1:1 features, at a dose of 92 mJ/cm2 using a phase shift mask on a Exitech 157 nm small field mini-stepper. Also, these have 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/cm2 employing using a Binary mask. A description is also given of our work on 193 nm/immersion lithography. Specifically, the effects of changing resist compoents such as PAG and Base content will be discussed. Also, a description of the utility of a protective base soluble barrier coat will be given.

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].

A new correction technique has been developed not only to reduce the corner rounding, but also to restrain the building up of shot counts that is able to increase the exposure time in electron beam (e-beam) lithography. It is able to prove the developed corner rounding correction technique is useful with high accuracies throughout the simulation of several different types of correction in the data preparation software, Inscale® from Aselta Nanographics, and its comparisons with exposure images. The developed one is helpful to suppress the accumulation of shot counts either. Furthermore, it shows the general limit of corner rounding correction in a conventional variable shaped beam exposure tool with current resist process. Firstly, we are demonstrating the new method for correcting the corner rounding that either can avoid the extension of exposure shot counts, called writing time. Secondly, this study reveals the current bounds of corner rounding correction, especially the lithography employing the shaped beam tool. Finally, we propose the criteria of data preparation for the corner rounding in e-beam lithography, specifically upcoming 18nm technology node and practical applications.

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.

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 etch roughness. Here Si-doped ZrO2 (ALD) and spin-coatable ZrO2 were compared to the pure and crystalline ZrO2 as main selective material.

Resist processing for future technology nodes becomes more and more complex. The resist film thickness is getting thinner and hardmask concepts (trilayer) are needed for reproducible etch transfer into the stack. Additional layers between resist and substrate are influencing the electron scattering in e-beam lithography and may also improve sensitivity and resolution. In this study, bare silicon wafers with different assisting underlayers were processed in a 300 mm CMOS manufacturing environment and were exposed on a 50 keV VISTEC SB3050DW variable-shaped electron beam direct writer at Fraunhofer CNT. The underlayers are organic-inorganic hybrid coatings with different metal additives. The negative-tone resist was evaluated in terms of contrast, sensitivity, resolution and LWR/LER as a function of the stack. The interactions between resist and different assisting underlayers on e-beam direct writing will be investigated. These layers could be used to optimize the trade-off among resolution, LWR and sensitivity in future applications.

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.

Using electron beam direct write (EBDW) as a complementary approach together with standard optical lithography at 193nm or EUV wavelength has been proposed only lately and might be a reasonable solution for low volume CMOS manufacturing and special applications as well as design rule restrictions. Here, the high throughput of the optical litho can be combined with the high resolution and the high flexibility of the e-beam by using a mix & match approach (Litho- Etch-Litho-Etch, LELE). Complementary Lithography is mainly driven by special design requirements for unidirectional (1-D gridded) Manhattan type design layouts that enable scaling of advanced logic chips. This requires significant data prep efforts such as layout splitting. In this paper we will show recent results of Complementary Lithography using 193nm immersion generated 50nm lines/space pattern addressing the 32nm logic technology node that were cut with electron beam direct write. Regular lines and space arrays were patterned at GLOBALFOUNDRIES Dresden and have been cut in predefined areas using a VISTEC SB3050DW e-beam direct writer (50KV Variable Shaped Beam) at Fraunhofer Center Nanoelectronic Technologies (CNT), Dresden, as well as on the PML2 tool at IMS Nanofabrication, Vienna. Two types of e-beam resists were used for the cut exposure. Integration issues as well as overlay requirements and performance improvements necessary for this mix & match approach will be discussed.

Two inorganic non-chemically amplified resists (XE15CB and XE15IB) were investigated. The resists are based on hafnium oxide sulfate and spin-cast from aqueous solution. They differ in sensitivity and resolution. In contrast to other studies, the materials were coated for the first time on 300 mm wafers and exposed on a 50 kV VISTEC SB3050DW variable shaped electron beam direct writer in a near-production environment at Fraunhofer CNT. In this paper, the evaluation of this resist family and its feasibility for production will be discussed. The resists were evaluated in terms of contrast, sensitivity and resolution. The process characteristics required for CMOS manufacturing such as delay stability were also examined. Furthermore, by exposing a large SRAM pattern (design CD of 22 nm), the exposure of a real application pattern was demonstrated.

A new correction approach was developed to improve the process window of electron beam lithography and push its resolution at least one generation further using the same exposure tool. An efficient combination of dose and geometry modulation is implemented in the commercial data preparation software, called Inscale®, from Aselta Nanographics. Furthermore, the electron Resolution Improvement Feature (eRIF) is tested, which is based on the dose modulation and multiple-pass exposure, for not only overcoming the narrow resist process windows and disability of exposure tool but also more accurate correction of exposure data in the application of sub-35nm regime. Firstly, we are demonstrating the newly developed correction method through the comparison of its test exposure and the one with conventional dose modulation method. Secondly, the electron Resolution Improvement Feature is presented with the test application for complementary exposure and with the application of real design, specifically for sub-30nm nodes. Finally, we discuss the requirements of data preparation for the practical applications in e-beam lithography, especially for future technology nodes.

For the manufacturing of semiconductor technologies following the ITRS roadmap, we will face the nodes well below 32nm half pitch in the next 2~3 years. Despite being able to achieve the required resolution, which is now possible with electron beam direct write variable shaped beam (EBDW VSB) equipment and resists, it becomes critical to precisely reproduce dense line space patterns onto a wafer. This exposed pattern must meet the targets from the layout in both dimensions (horizontally and vertically). For instance, the end of a line must be printed in its entire length to allow a later placed contact to be able to land on it. Up to now, the control of printed patterns such as line ends is achieved by a proximity effect correction (PEC) which is mostly based on a dose modulation. This investigation of the line end shortening (LES) includes multiple novel approaches, also containing an additional geometrical correction, to push the limits of the available data preparation algorithms and the measurement. The designed LES test patterns, which aim to characterize the status of LES in a quick and easy way, were exposed and measured at Fraunhofer Center Nanoelectronic Technologies (CNT) using its state of the art electron beam direct writer and CD-SEM. Simulation and exposure results with the novel LES correction algorithms applied to the test pattern and a large production like pattern in the range of our target CDs in dense line space features smaller than 40nm will be shown.

For the manufacturing of semiconductor technologies following the ITRS roadmap, we will face the nodes well below 32nm half pitch in the next 2~3 years. Despite being able to achieve the required resolution, which is now possible with electron beam direct write variable shaped beam (EBDW VSB) equipment and resists, it becomes critical to precisely reproduce dense line space patterns onto a wafer. This exposed pattern must meet the targets from the layout in both dimensions (horizontally and vertically). For instance, the end of a line must be printed in its entire length to allow a later placed contact to be able to land on it. Up to now, the control of printed patterns such as line ends is achieved by a proximity effect correction (PEC) which is mostly based on a dose modulation. This investigation of the line end shortening (LES) includes multiple novel approaches, also containing an additional geometrical correction, to push the limits of the available data preparation algorithms and the measurement. The designed LES test patterns, which aim to characterize the status of LES in a quick and easy way, were exposed and measured at Fraunhofer Center Nanoelectronic Technologies (CNT) using its state of the art electron beam direct writer and CD-SEM. Simulation and exposure results with the novel LES correction algorithms applied to the test pattern and a large production like pattern in the range of our target CDs in dense line space features smaller than 40nm will be shown.

For the manufacturing of semiconductor technologies following the ITRS roadmap, we will face nodes well below a 32-nm half pitch in the next 2 to 3 years. Despite being able to achieve the required resolution, which is now possible with electron beam direct-write variable-shaped beam equipment and resists, it becomes critical to precisely reproduce dense line space patterns onto a wafer. This exposed pattern must meet the targets from the layout in both dimensions (horizontally and vertically). For instance, the end of a line must be printed in its entire length to allow a contact to be placed later. Up to now, the control of printed patterns such as line ends was achieved by a proximity effect correction mostly based on a dose modulation. This investigation of line end shortening (LES) includes multiple novel approaches, and contains an additional geometrical correction to push the limits of the available data preparation algorithms and the measurement. The designed LES test patterns, which aim to characterize the status of LES in a quick and easy way, were exposed and measured at Fraunhofer Center Nanoelectronic Technologies using its state-of-the-art electron beam direct writer and CD-SEM. Simulation and exposure results with the novel LES correction algorithms applied to the test pattern and a large production-like pattern in the range of our targeted critical structure dimensions in dense line space features smaller than 40 nm will be shown.

For shortening the writing time, especially in shaped Electron Beam Direct Writing (EBDW), it is crucial to reduce the number of shapes and the coverage of layout for exposure. The determination of conventional or reversed image printing according to the process integration is one of the concerns for time and cost-effective process in the EBDW. We have studied two different cases for the purpose above. First, the proximity effect correction (PEC) with dose modification applied on each tone of resists, positive and negative, for the printing of conventional and reversed images. The CDs that are obtained from the both printed images compared and are either with that from the simulations. Secondly, the two different types of PEC, dose and shape modification, applied to a conventional image using an identical point spread function (PSF). The line edge roughness (LER), line width roughness (LWR) and CDs in dose and shape corrected conventional image pattern have been measured and compared. The MGS/PROXECCO was used for all the preparation of exposure data mentioned above. In summary, we suggest the strategies of efficient PEC for the EBDW of contrasting images, propose the available method of PEC for the time-efficient EBDW, and for the further multiple EBDW developments.

Electron beam direct write (EBDW) can be utilized for developing metrology methods for future technology nodes. Due to its advantage of high resolution and flexibility combined with suitable throughput capability, variable-shaped E-Beam lithography is the appropriate method to fabricate sub 40nm resist structures with accurately defined properties, such as critical dimension (CD), pitch, line edge roughness (LER) and line width roughness (LWR). In this study we present results of exposure experiments intended to serve as an important instrument for testing and fitting various metrology and defect density measurement methods for future technology nodes. We successfully fabricated sub 40nm gratings with varying CD, pitch, programmed defects and LER/LWR. First metrology measurements by means of optical scatterometry on these dense structures show that variation of the signal response is sufficient to detect sub 10nm fluctuations with a satisfying repeatability.

Because of mask cost reduction, electron beam direct write (EBDW) is implemented for special applications such as rapid prototyping or small volume production in semiconductor industry. One of the most promising applications for EBDW is design verification by means of metal fix. Due to write time constrains, Mix & Match solutions have to be developed at smaller nodes. This study reports on several Mix and Match processes for the integration of E-Beam lithography into the optical litho process flow of Qimonda's 70 nm and 58 nm DRAM nodes. Different metal layers have been patterned in part with DUV litho followed by E-Beam litho using a 50 kV Vistec SB3050 shaped electron beam direct writer. All hardmask patterns were then simultaneously transferred into the DRAM stack. After full chip processing a yield study comprising electrical device characterization and defect investigation was performed. We show detailed results including CD and OVL as well as improvements of the alignment mark recognition. The yield of the E-Beam processed chips was found to be within the range of wafer-to-wafer fluctuation of the POR hardware. We also report on metal fix by electrical cutting of selected diodes in large chip scales which usually cannot be accessed with FIB methods. In summary, we show the capability of EBDW for quick and flexible design verification.

The resolution of a variable shaped beam writer is typically given for the standard geometries like isolated line, isolated space, and dense (1:1) line/space pattern. It is related to the imaging power of both the tool itself as well as the resist process. In this paper we concentrate on small shots with dimensions smaller than the resolution limit, butting to a larger shot. We show experimentally that for a line resolution of 40 nm the resolution for butting sub resolution shots can be as small as 20 nm.

Summary form given only. High resolution variable shaped beam (VSB) electron lithography becomes more and more important for chip and mask making. The use for direct write of critical layers, at least one node ahead of the current production level, enables early device and technology development as well as fast prototyping. Aggressive OPC features of advanced photomasks require a resolution capability of the chrome patterning process clearly below 80 nm. Finally, the nanoimprint lithography has been discussed as a future option for device making and template structuring demands minimum feature sizes corresponding to the considered node. These three addressed pattern generator applications require both, high resolution and a cost-effective throughput for complex pattern and therefore we evaluated a VSB system in combination with latest chemically amplified resist (CAR) samples for these purposes. The used Vistec VSB writer is equipped with Vistec's most recent 3050 column [1], operating at 50 kV, a current density of 20A/cm2 with an improved edge acuity focussed on a resolution of 35 nm and below. In a test using HSQ lines with 30 nm half pitch could be obtained proving the high resolution capability of this new column. For the considered applications we evaluated e-beam sensitive pCARs and nCARs of different vendors in combination with the new Vistec column. The evaluation of all CARs was accomplished according to an identical method focussed on the determination of resolution, line edge roughness, sensitivity, vacuum stability, bake sensitivity and etch stability After these basic tests first optimized processes have been developed executing DoEs with bake and developer conditions as input parameters. Many CARs suffer from limited resolution and severe line edge roughness. One resist vendor provided CARs based on the same polymer but with different PAG and quencher concentrations resulting in different e-beam sensitivities. On the basis of these materials we investigated the dependency between the sensitivity on one hand and resolution and line edge roughness on the other hand. Finally, we will demonstrate the application of selected CARs for nanoimprint template and photomask patterning. Sub-50 nm pillars on a template have been generated using a negative-tone resist while a pCAR has been applied for structuring of 50 nm features in an 80 nm thick hardmask / chrome stack of a binary photomask.

For Electron Beam Direct Write (EBDW) a systematic investigation of defect density using a Negevtech 3100 darkfield inspection system was performed. A special defect learning pattern for memory applications with coverage of 50% was designed and printed partially on 300mm wafers using chemically amplified positive and negative E-Beam resists. By optical defect measurements post litho it was possible to inspect 50nm dense lines to characterize the exposure system as well as the used resist process. Using this method a large exposed area in millimeter range can be inspected and an overview on exposure quality can be gained in a reasonable amount of time. Particle measurements were performed additionally to distinguish between particles and exposure issues. By using darkfield measurements, process related issues like development problems and resist residuals can be found, as well as writing issues like shot butting and write field stitching can be quickly determined and controlled with this method. In this paper, the measurement methodology is described as well as the effect of writer imperfections on the darkfield images. A pareto analysis is performed and shows the frequency of occurrence of different defects. Measures to reduce defects - especially on the tool side - are given. The method is feasible to use in a regular check to control tool and process performance.

An overview about process window evaluation and characteristic features of photoresists for e-beam/optical hybrid lithography as well as mix and match applications and implementation into new integration concepts is given. For that, several commercially available deep ultraviolet (DUV) (248 nm), ArF (193 nm), and e-beam resist samples from various suppliers were exposed at Qimonda's dynamic random access memory pilot line environment using both e-beam and optical exposure. Due to the diverse, sometimes contradictory requirements and properties of the different material platforms (e.g., resolution, sensitivity, vacuum stability, etch resistance, etc.), a unique material for true hybrid lithography is difficult to find. At least the tested DUV resist is limited applicable for e-beam exposures putting up with low e-beam sensitivity.

E-beam direct writing, one node ahead of advanced optical lithography, can be a time and cost effective option for early device and technology development as well as for fast prototyping. Because of the device complexity only a variable-shaped e-beam writer combined with sensitive chemically amplified resists (CAR) can be considered for this approach. We evaluated various pCARs and nCARs of all major suppliers for our goal to structure DRAMs of the 50nm node using the Leica SB350 e-beam writer. The most promising samples were selected for a process optimization by variation of bake and development conditions. Finally, one resist of each tonality met the most of our specifications like dense lines and contact holes resolution, sensitivity and vacuum stability.

A detailed account will be given of work done on the Micrascan VII (NA 0.75) at INVENT in Albany with AZ EXP X20 and AZ EXP X25 resist systems based upon BOCME protected fluoroalcohol resins. These resins were examined either with a high or low level of formulated photoacid generator (PAG). Our evaluations done both with binary and alternating phase shift mask exposures. It was found in our initial studies done at relatively high amine levels (1-2 ppb) that AZ EXP X25 X with low PAG gave the best performance.

We summarize our work on devising protective barrier coats for use against airborne contamination when using tert-butoxycarbonylmethyl (BOCME) capped fluoroalcohol resist resins as part of our strategy to develop a 157 nm resist platform. We will describe how a barrier coat (AZ® EXP FX Coating 145) consisting of a fluoroc-yclopolymer formulation, soluble in aqueous developer, can improve the post-exposure delay (PED) latitude of 157 nm resist resists exposed under conditions or airborne contamination. Specifically, a 20 nm thick coating of AZ® EXP FX Coating 145 gives a PED latitude for L/S features of at least 10 min under condition of airborne amine contamination (10 ppb amine contamination). The barrier coat, AZ® EXP FX coating 145 is formulated in a solvent which is compatible with resist film coated from typical 193 nm resist spin casting solvents. Moreover, it can be easily removed as part of the normal aqueous base development scheme, no extra post-apply bake or stripping step is required.

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.

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.