KEYWORDS: Picture Archiving and Communication System, Molecules, Scanning electron microscopy, Photoresist developing, Hydrogen, Molecular interactions
Our earlier studies pointed to a strong correlation between the molecular weight of novolac resin and lithographic characteristics. In particular, they showed that the resolution and DOF characteristics of resists may be improved by controlling molecular weight distribution. The present study focuses on photoactive compound (PAC) structure and resin structure. This paper discusses the effects of differences in PAC ballast structure and the composition of m-cresol (metacresol), p-cresol (para-cresol), and xylenol, phenolic monomers that constitute novolac resin, on resolution and lithographic characteristics, based on development rates and resist pattern simulations.
In recent years, nanoimprint lithography is applied to manufacturing of optical materials and biosensor. However, void and generated gas are caused pattern failures. We proposed cellulose based gas permeable molds to reduce pattern failures. In this research we could raise the mold reproducibility by using the under-layer coating and liquid release agent. It was confirmed that imprinting materials including 10 wt% each of acetone, cyclopentane, and propylene glycol methyl ether acetate (PGMEA) as volatile solvents could also be imprinted accuracy and number of imprinting times were increased. In addition, we succeeded in expand the cellulose based gas permeable mold size 5 times as compared with the conventional cellulose based gas permeable mold by using step and repeat process and large scale quartz mold. Various manufacturing can be expected by increasing the repeatability and the pattern area of the cellulose based gas permeable mold.
The electronic substrate used for the MEMS device is finely processed, and imprint lithography is often used as a processing method. However, in the printing process, gas is caught in the molding material, and transfer failure frequently occurs. Therefore, in this study, a gas permeable metal plate with a gas permeable structure inside was fabricated and imprinted on a material to be transferred containing 50% of volatile material. As a result, no gas pool was observed and imprinting was possible without defective transfer. This not only prevents entrainment of gas at the time of imprinting, but also a transfer material containing a volatile solvent can be used as a material to be transferred. It is greatly expected that the developed gas permeable metal plate becomes a material necessary for MEMS device processing.
MEMS technology is incorporated into various devices (automobiles, digital cameras, optical devices) indispensable for our daily lives. Semiconductor manufacturing process technology such as photolithography method and ion beam method is mainly used for micropatterning necessary for MEMS and microfabrication of diffraction grating. In photolithography, many transfer defects caused by gas are generated. Therefore, a metal plate having gas permeability was prepared with a 3D printer, and the surface and internal structure of the metal plate was evaluated. Further, the porosity of the metal plate was calculated by measuring the size and weight of the produced metal plate. As a result, it was confirmed that there were numerous holes in the inside of the metallic material, and it was confirmed that the hole having the role of permeating the gas and the hole having the role of temporarily preserving the gas. Furthermore, it was also confirmed that the porosity of the metal plate is about 10%. Metallic materials with gas permeability can be expected to be materials required for MEMS device processing.
Nanoimprint lithography is applied to manufacturing of cell culture dish and biosensor. The outgas released from the material often causes defects on patterns. Gas permeable templates were derived from cellulose for ultraviolet nanoimprint lithography process. The templates were made of thermoset cellulose of acrylic group and methacrylic group. The light transmission rate of the thermoset cellulose film and mechanical properties and pattern structure of the gas permeable template were measured. The template with acrylic group baked at 80 °C for 10 min. showed superior mechanical properties. This suggests the template had a large number of crosslinked points. After pattern transfer from quartz template, structures of the holes, the pillars, and the lines and spaces on the gas permeable template were observed.
We have been trying to improve nanoimprint lithography performance through modification of template materials. We have reported a biomass based template with gas permeability which decreases transcriptional defects on template materials caused by involved solvents and cracked gasses generated from imprinted materials. (SPIE2016 and 2017) The line patterning results using the biomass based gas permeable template were better to reduce the line pattern failure as compared with that of quartz based template as the standard reference. In this study, we will report a mechanical property improvement of the template by blending cellulose nanofiber (CNF) to the biomass template. The blended template showed improved gas transmission coefficient and mechanical properties than non-blended template. The proposed nanoimprint lithography using biomass based template with gas permeable and gaseous adsorption is one of the most promising processes ready to use for mass-production of nanoscale devices.
A cellulose-based gas permeable mold having thermal crosslinking group for nanoimprint lithography has been developed to prevent transcriptional defects by volatile solvents from nanoimprinting materials. 3 wt.% of thermal initiator was required for producing the cellulose-based gas permeable mold. The void on 10 μm line structure of imprinted UV crosslinked resin with acetone as volatile solvents in nanoimprint lithography process using non-gas permeable mold was significantly removed using the cellulose-based gas permeable mold due to its high oxygen gas permeability. The cellulosebased gas permeable mold allows the employment of solvent including imprinting materials such as compounds and alloy particle.
Advanced nano-imprint lithography appears as a simple, cost reduction in manufacturing, fast operation, develop-less patterning application compatible with conventional pattern transfer techniques such as ultraviolet and electron beam lithography. However, defects generated in nano-imprint lithography present challenges that must be resolved in order to mass-produce advanced devices. The nano-imprint lithography requires the clean separation of a quartz template from a resist material, and the force required to create this separation must be minimized to prevent the resist pattern collapse and defects. This procedure is proven to be suitable for material design and the process conditions of organic-inorganic hybrid resist materials on photo-reactive underlayer material for the defect reduction by mold contamination when the mold was removed from the organic-inorganic hybrid resist materials after ultraviolet irradiation. The developed organic-inorganic hybrid resist material with ultraviolet crosslinking groups produced high resolutions nano-patterning of 50 nm line and excellent etch properties for semiconductor memory, MEMS, NEMS, biosensors, and medical devices.
Silicone elastomers ( polydimethylsiloxane _ PDMS) are widely used in the field of imprint lithography and microcontactprinting (μCP). When performing microcontactprinting, the mechanical properties of the PCMS as a base material have a great influence on the performance of the device. Cellulose nanofibers having features of high strength, high elasticity and low coefficient of linear expansion have attracted attention in recent years due to their characteristics. Therefore, three types of crystalline cellulose having different molecular weights were added to PDMS to prepare a composite material, and dynamic viscoelasticity was measured using a rheometer. The PDMS with the highest molecular weight crystalline cellulose added exhibited smaller storage modulus than PDMS with other molecular weight added in all temperature ranges. Furthermore, when comparing PDMS to which crystalline cellulose was added and PDMS which is not added, the storage modulus of PDMS to which cellulose was added in the low temperature region was higher than that of PDMS to which it was not added, but it was reversed in the high temperature region It was a result. When used in a low temperature range (less than 150 ° C.), it can be said that cellulose can function as a reinforcing material for PDMS.
A chemical cross-linked transparent film was got by a silicon compound to crystalline cellulose. Temperature dependency for the elasticity modulus of a provided film was measured. The shear elastic modulus was obtained the value of 2 x 106 [Pa] at room temperature. The sample decreases in 190 [deg. C] for the elasticity modulus at the room temperature as 60%, but approximately 10% recover when temperature rises up to 200 [deg. C] or more.
Traditional diazonaphthoquinone (DNQ) positive photoresists are widely used for TFT-LCD array process. Current LTPS technology has more than 600ppi resolution is required for small or middle-sized TFT liquid crystal display panels. One of the ways to enhance resolution is to apply i-line single exposure system instead of traditional g/h/ibroadband exposure system. We have been developing i-line chemically amplified photoresist ECA 200 series for the next generation flat panel display (FPD). ECA 200 consists of three components: a phenol resin, a photo acid generator and dissolution enhancer. We applied two different types of dissolution enhancers with two different kinds of protected groups to our resist materials. As a result, we achieved higher sensitivity, higher resolution, less footing of the resist profile and reduced standing wave effect compared with traditional DNQ photoresists. In addition, we have found further property of photoresist that does not need post exposure bake (PEB) process. This resist has a great advantage at most of current panel plants without PEB process.
Cracked gasses generated from imprinted materials and/or involved solvents cause transcriptional defects on template materials and insufficient filling of imprinted materials in nanoimprint lithography. This study aims to create the novel gas permeable nanoimprint template materials to prevent such defects caused by cracked gasses and involved solvents. A biomass based template was investigated in thermal and UV nanoimprint lithography instead of the conventional template such as quartz, PMDS, DLC, block copolymers. The line patterning results using the biomass based gas permeable template in nanoimprint lithography were better to reduce the line pattern failure compared with that of quartz based template as a reference. Gas transmission coefficient was evaluated for template materials having thermal crosslinkable urethane groups. The proposed nanoimprint lithography using biomass based gas permeable template is one of the most promising processes ready to be investigated for mass-production of fine device applications.
Novolak resists have been widely used in IC production and are used to this day in the production of flat panel displays (FPDs) and MEMS. However, with the advent of high-definition devices, FPDs must meet growing requirements for finer dimensions. These trends have generated requirements for higher sensitivity, higher resolution, and wider process margins for novolak resists. Using a lithography simulator with the goal of improving the performance of novolak resists, we examined various approaches to improving resist materials. This report discusses efforts to improve resolution and to broaden process margins using a novolak resin that exhibits a higher degree of fractionation than in the previous report (maximum fractionated resin) with the addition of low molecular weight phenol resins.
In this paper, we studied a novel approach, UV nanoimprint lithography using glucose-based template with gaspermeable
and gaseous adsorption for reduction of air-trapping issue. The air-trapping issue in UV nanoimprint
lithography resist is a cause of pattern failure in resist or UV curable materials. The results of 180 nm dense line
patterning of UV curable patterning materials containing acetone in UV nanoimprint lithography using glucose-based
template with gas-permeable and gaseous adsorption were effected to reduce the pattern failure as compared with that of
the poly(dimethylsiloxane) without gas-permeable and gaseous adsorption as the reference. The proposed UV
nanoimprint lithography using glucose-based template with gas-permeable and gaseous adsorption is one of the most
promising processes ready to be investigated for mass-production of photomask applications.
In order to enable the large-area patterning of micro-fabrication, constant intensity will be required to the mold material.
Then, we have deposited the sample was subjected to a chemical synthesis in different hydroxy propyl cellulose (HPC)
viscosity, we evaluated its transferability and optical transparency. As a result of gel permeation chromatography system
(GPC) measurement, we confirmed that high viscosity sample was high molecular weight in the two types of HPC with
different viscosity. Further, we will produce a film with the sample, we evaluated the transfer and light permeability of
the film. In the evaluation of transfer properties, Regardless of the level of the viscosity of the HPC of the main raw
material, the shape of the master silicon template(5μm line and space) had been transferred to the HPC template.
Moreover in the evaluation of optical transparency, HPC template had about 60% of the light transmittance in the 365nm
wavelength. The sample have a possibility to improve the strength to be polymerized, and a high optical transparency, it
used in this study is expected to be a mold material for UV nano-imprint lithography.
A novel nanoimprint lithography process using disposable biomass template having gas permeability was investigated. It was found that a disposable biomass template derived from cellulose materials shows an excellent gas permeability and decreases transcriptional defects in conventional templates such as quartz, PMDS, DLC that have no gas permeability. We believe that outgasses from imprinted materials are easily removed through the template. The approach to use a cellulose for template material is suitable as the next generation of clean separation technology. It is expected to be one of the defect-less thermal nanoimprint lithographic technologies. It is also expected that volatile materials and solvent including materials become available that often create defects and peelings in conventional temples that have no gas permeability.
Novolak resists have been widely used in IC production and are still used in the production of flat panel displays (FPDs) and MEMS. However, with the advent of high-definition products, FPDs increasingly face requirements for finer dimensions. These trends have generated requirements for higher sensitivity, higher resolution, and wider process margin for novolak resists. Using a lithography simulator with the goal of improving the performance of novolak resists, we examined various approaches to improving resist materials. This report discusses efforts to improve resolution and sensitivity using highly fractionated novolak resins and adding low molecular weight phenol resins.
The validity of our approach of inedible cellulose-based resist material derived from woody biomass has been confirmed experimentally for the use of pure water in organic solvent-free water spin-coating and tetramethylammonium hydroxide(TMAH)-free water-developable techniques of eco-conscious electron beam (EB) and extreme-ultraviolet (EUV) lithography. The water developable, non-chemically amplified, high sensitive, and negative tone resist material in EB and EUV lithography was developed for environmental affair, safety, easiness of handling, and health of the working people. The inedible cellulose-based biomass resist material was developed by replacing the hydroxyl groups in the beta-linked disaccharides with EB and EUV sensitive groups. The 50-100 nm line and space width, and little footing profiles of cellulose-based biomass resist material on hardmask and layer were resolved at the doses of 10-30 μC/cm2. The eco-conscious lithography techniques was referred to as green EB and EUV lithography using inedible cellulose-based biomass resist material.
Newly eco-friendly high light transparency film with plant-based materials was investigated to future development of liquid crystal displays and optical devices with water repellency as a chemical design concept of nanoimprint lithography. This procedure is proven to be suitable for material design and the process conditions of ultraviolet curing nanoimprint lithography for green water-repellent film derived from biomass with high-light transparency. The developed formulation of advanced nanoimprinted materials design derived from lactulose and psicose, and the development of suitable UV nanoimprint conditions produced high resolutions of the conical shaped moth-eye regularly-nanostructure less than approximately 200 nm diameter, and acceptable patterning dimensional accuracy by the replication of 100 times of UV nanoimprint lithography cycles. The newly plant-based materials and the process conditions are expected as one of the defect less nanoimprint lithographic technologies in next generation electronic devices.
We investigated the eco-friendly electron beam (EB) and extreme-ultraviolet (EUV) lithography using a high-sensitive negative type of green resist material derived from biomass to take advantage of organic solvent-free water spin-coating and tetramethylammonium hydroxide(TMAH)-free water-developable techniques. A water developable, non-chemically amplified, high sensitive, and negative tone resist material in EB lithography was developed for environmental affair, safety, easiness of handling, and health of the working people, instead of the common developable process of TMAH. The material design concept to use the water-soluble resist material with acceptable properties such as pillar patterns with less than 100 nm in high EB sensitivity of 10 μC/cm2 and etch selectivity with a silicon-based middle layer in CF4 plasma treatment was demonstrated for EB and EUV lithography.
Reverse-tone step and flash imprint lithography (S-FIL/R) requires materials that can be spin-coated onto patterned substrates with significant topography and that are highly planarizing. Ideally, these planarizing materials must contain silicon for etch selectivity, be UV or thermally curable, and have low viscosity and low volatility. One such unique material, in particular, a branched and functionalized siloxane (Si-12), is able to adequately satisfy the above requirements. This paper describes a study of the properties of epoxy functionalized Si-12 (epoxy-Si-12) as a planarizing layer. An efficient synthetic route to epoxy-Si-12 was successfully developed, which is suitable and scalable for an industrial process. Epoxy-Si-12 has a high silicon content (30.0%), low viscosity (29 cP at 25°C), and low vapor pressure (0.65 Torr at 25°C). A planarizing study was carried out using epoxy-Si-12 on trench patterned test substrates. The material showed excellent planarizing properties and met the calculated critical degree of planarization (critical DOP), which is a requirement for a successful etch process. An S-FIL/R process using epoxy-Si-12 was demonstrated using an Imprio® 100 (Molecular Imprints Inc., Austin, Texas) imprint tool. The results indicate that epoxy-Si-12 works very well as a planarizing layer for S-FIL/R.
This presentation reported an approach of glucose derivatives to resist polymers for eco-friendly optical NEMS and MEMS. The material design concept to use the water-soluble resist material with highly efficient crosslinking, water development, and lower film thickness shrinkage was proposed for green lithography. The lithographic properties due to the glucose derivatives, and the low film thickness shrinkage due to distinctive bulky chemical structure were proposed in the resist material, and then demonstrated to be effective for creating high resolution, excellent patterning dimensional accuracy, and low line edge roughness in EB lithography. Mixing or blending of glucose and cellulose derivatives was a valuable approach to the design of resist formulations for eco-friendly optical NEMS and MEMS.
Reverse-tone Step and Flash Imprint Lithography (S-FIL/R) requires materials that can be spin coated onto patterned
substrates with significant topography and that are highly-planarizing. Ideally, these planarizing materials must contain
silicon for etch selectivity, be UV or thermally curable, have low viscosity, and low volatility. One such novel material
in particular, a branched and functionalized siloxane (Si-12), is able to adequately satisfy the above requirements.
This paper describes a study of the properties of epoxy functionalized Si-12 (epoxy-Si-12) as a planarizing layer. An
efficient synthetic route to epoxy-Si-12 was successfully developed, which is suitable and scalable for an industrial
process. Epoxy-Si-12 has a high silicon content (30.0 %), low viscosity (29 cP @ 25 °C), and low vapor pressure (0.65
Torr @ 25 °C). A planarizing study was carried out using epoxy-Si-12 on trench patterned test substrates. The material
showed excellent planarizing properties and met the calculated critical degree of planarization (critical DOP), which is a
requirement for a successful etch process. An S-FIL/R process using epoxy-Si-12 was demonstrated using, an ImprioR
100 (Molecular Imprints Inc., USA) imprint tool. The results indicate that epoxy-Si-12 works very well as a planarizing
layer for S-FIL/R.
Nanoimprint lithography is a newly developed patterning method that employs a hard template for the patterning of
structures at micron and nanometerscales. This technique has many advantages such as cost reduction, high resolution,
low line edge roughness (LER), and easy operation. However, resist peeling, defects, low degree of planarization, and
low throughput issues present challenges that must be resolved in order to mass produce advanced nanometer-scale
devices. In this study, the new approach of using spin-on hard mask materials under the resist to modify its adhesion
during a UV irradiation process in nano imprint lithography was proposed to increase process latitudes. The performance of this process is evaluated by using step and flash imprint lithography. We expect that these spin-on hard mask materials (NCI-NIL-U series) under organic resist will be one of the most promising materials in the next generation of nano imprint lithography.
Nanoimprint lithography (NIL) technology has been focused on its wide variety of applications and good cost performance. It has also been indicated that the selection of materials depending on the application fields is important. In this research, we selected silicasol nanoparticles as inorganic materials and successfully dispersed them uniformly into photofunctional monomers with non-solvent systems. Dispersed silicasols were also treated with a photofunctional crosslinker and were mixed with other monomers to prepare various imprint materials. The UV-NIL performance, obtained by using an imprint test machine "LTNIP-5000" from Litho Tech Japan Co. showed greatly improved UV hardening properties and physical properties such as refractivity, thermal stability compared to organic (non-hybrid) materials. As a result, 200 nm line and space patterns were successfully imprinted with no shrinkage at pressure of 3.1 MPa and exposure doses of 1 J/cm2.
PACs which have a defined number of DNQs and -OH groups were synthesized with high yield by the selective esterification method, and the relationship between number and orientation of DNQs, and lithographic performances and dissolution properties, were examined and measured by puddle development. From our present and previous examinations, it is concluded that existence of one -OH group and two DNQs, which are separated from each other on a ballast molecule, is the most preferable structure of PAC, which provides a photoresist not only a high (gamma) -value and resolution capability but also suitable sensitivity and a scum-free pattern. According to concept of polyphotolysis results are discussed quantitatively by dissolution inhibition effect and the number of DNQs of the PAC.
Steric hindrance on a ballast molecule causes selective esterification of -OH groups and provides novel di-esterified PACs having -OH group(s) with high selectivity. These novel PACs give photoresists higher sensitivities, (gamma) -values and resolutions, than those of fully esterified PACs. Also, these novel PACs provide scum-free patterns. Comparison of dissolution properties of a novel di-esterified PAC having a sterically hindered -OH with those of a di-esterified PAC suggests that the presence of -OH enhances dissolution rates, but it does not change the slope of logR-logE plots. DRM's agitated development reduces a large (gamma) -value of a novel PAC observed in puddle development. On the other hand, (gamma) -values of fully esterified PACs were not affected by the change of development methods. This observation suggests significance of (gamma) - value evaluation by puddle development for the investigation of high performance PACs.
A new type of novolak resins is proposed for high performance positive photoresists. This novolak resin has a molecular weight distribution different from the existing materials and is characterized by its low content of middle molecular weight components. We call this novolak resin 'Tandem type novolak resin'. The positive photoresists that contain Tandem type novolak resins exhibit improved performance in resolution, sensitivity, and heat resistance which are usually balanced in trade-off relationships. The characteristics, syntheses, and advantages of Tandem type novolak resins are described. The mechanism of resist performance improvement will also be discussed.
The relationship between resist performance and the kinds of phenolic
compounds for novolak resins was investigated from the standpoint of the
image formation process. Dissolution rates were measured on photoresists
containing novolak resins made from various phenolic compounds including
phenol,cresol,ethylphenol,butylphenol,and their copolymers. It was fo.und
that there are suitable combinations of phenolic compounds to exhibit high
resist performance. On the basis of the experimental results,we discuss the
effect of the kinds of phenolic compounds on the dissolution characteristics
and the structure of novolac resins. Finally,we propose a selection
principle of phenolic compounds for novolak resins useful to design high
performance positive photoresists.
1.lntroduction
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.