Synchrotron Radiation Lithography Research Articles

Patterning of burnishing head for hard disk platters by synchrotron radiation lithography

This paper discusses the patterning of the burnishing head for hard disk platters on the AlTiC substrate, performed by X-ray exposure through X-ray mask to identify areas still left on the substrate after the photoresist development. The high energy and the low divergence of the synchrotron light provided the high-aspect-ratio microstructures with high accuracy patterns of burnishing head specifications. After the X-ray lithography was processed, the AlTiC substrate coated with the SU-8 hard mask was dry-etched with CF4 of the RIE machine and run under the various conditions of the industrial process. An appropriate condition based on a total of 10 experimental conditions, which were based on the CCD technique, was investigated at Minitab using the data collected for analysis and compared with the standard specification. Based on the standard specification of the critical dimension of 8.02 µm and the etched depth of 30.0 µm, the best condition for the experiment, calculated by the desirability approach, was the 250 µm-thick SU-8 photoresist with an exposure dose of 23,010 mJ/cm3 and an RIE etching time of about 20 h. Mathematically, this condition offers a critical dimension and an etched depth of 7.02 and 30.11 µm, respectively. When the actual experiment was conducted to confirm the results, and we found that the critical dimension and the etched depth showed values of 7.03 and 30.02 µm, respectively.

基于同步辐射光刻工艺和电铸工艺的金属纳米光栅模具制备

基于同步辐射光刻工艺和电铸工艺的金属纳米光栅模具制备

Shape Prediction of 3‐D Microstructures Fabricated by PCT Technique and Synchrotron Radiation Lithography

AbstractWe report in this paper simulations for deformed shape predictions of three‐dimensional (3‐D) microstructures fabricated by the plane pattern to cross‐section transfer (PCT) technique and synchrotron radiation (SR) lithography. The investigation of the shape‐prediction system enhances the possibility for higher accuracy of the prediction. In addition, the desired shapes can be confirmed by the shape prediction before designing the mask and running experiments. It is necessary to investigate a variety of error factors to shape prediction. We attempted various investigations. One of the possible causes could be the etching direction, which is dependent on the developing time. Therefore, we currently emphasize on the factor causing this error. In order to comprehend the mechanism of the factor, an algorithm that can simulate development was devised. We have developed a mathematical system of X‐ray energy distribution onto the PMMA (polymethylmethacrylate) resist, and the shape prediction is consequent to the simulations based on calculations from the mathematics software. The mathematical system for energy distribution depends on the SR light source, X‐ray mask specification, and resist specification. As a result, the predicted structures relevant to the absorbed energy–depth–position parameter set and absorbed energy–etching rate parameter set were obtained from this system. This system for shape prediction was implemented by the above parameter sets in C language. Copyright © 2010 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Design of hybrid sol–gel films for direct x-ray and electron beam nanopatterning

New epoxy based sol–gel organic inorganic materials, showing lithographic resist-likeproperties without the addition of any photocatalysts, are presented. To obtain a materialsensitive to radiation, specific sol–gel syntheses based on an organically modified alkoxidecontaining an epoxy ring, 3-glycidoxypropyltrimethoxysilane (GPTMS), have beendeveloped. The synthesis and the patternability of hybrid materials have been obtainedcontrolling the inorganic crosslinking degree and with an almost total absence of organicpolymerization. Two examples of directly patternable hybrid films, called GB and GGe,have been synthesized using acidic (GGe) and basic (GB) conditions and obtainingdifferent compositions.After electron beam lithography (EBL) or x-ray synchrotron radiation lithography (XRL)the polymerization of the organic component of the sol–gel film occurs, generating ahardening of the structure after post-exposure baking. The exposed polymerized materialbecomes insoluble, determining a negative resist-like behaviour of the film: the lithographicprocess of nanopatterning results from the dissolution of the unexposed areas in propersolvents (developers). Spatial resolution of the order of 200 nm is reported and a contrast of2.2 is achieved.The novelty of this work is that epoxy based materials, which have enhancedthermomechanical stability with respect to the more usual acrylic based resins, are directlynanopatterned for the first time by electron beam (EB) and/or x-ray beam radiationexposure without the aid of catalysts for polymerization. In contrast to common resiststhat are sacrificial layers of the fabrication process, direct patternable sol–gel hybridsconstitute the final material of the devices. In fact, an example of doping with a lightemitting dye is reported together with the achievement of directly patterned structures byEBL and XRL.

High-aspect-ratio through-hole array microfabricated in a PMMA plate for monodisperse emulsion production

Microchannel (MC) emulsification is a promising technique for producing monodisperse emulsions consisting of highly uniform droplets. The authors developed a high-aspect-ratio microstructure (HARMST) made of poly(methyl methacrylate) (PMMA) as a new MC emulsification device. A PMMA straight-through MC array plate consisting of 31,250 through-holes with a 7.3 × 22.9-μm oblong section and a 200-μm depth was fabricated by a process of synchrotron radiation (SR) lithography and etching. Oblong MCs fabricated in a PMMA straight-through MC array were highly uniform with a coefficient of variation of less than 2%. The fabricated PMMA straight-through MC array plate was used to produce water-in-oil (W/O) emulsions. Monodisperse W/O emulsions with average droplet diameters of approximately 25 μm and a minimum coefficient of variation of 3.2% were produced via a hydrophobic PMMA straight-through MC array. The PMMA straight-through MC array plate also produced monodisperse W/O emulsions at droplet production rates of up to 1.7 × 104/s. The PMMA straight-through MC array plates developed in this work are expected to expand the application field of emulsification using straight-through MC array plates, which have previously been made of single-crystal silicon.

Research and Application of LIGA Process at Nationol Synchrotron Radiation Laboratory

LIGA(Lithographie galvanformung and abformug)process is a micro fabrication method that can use various materials to obtain high aspect ratio microstructures.The principle of LIGA techniques and the parameters o f LIGA experimental station at NSRL are introduced.The recent progresses in the research of LIGA techniques at NSRL,such as synchrotron radiation lithography,mi- cro-electroforming,micro-molding,and the application of LIGA techniques,such as micro-inerial devices and micro-fluidic devices, are presented in detail.The development status of research and application of LIGA techniques and the problems encountered are analyzed.Some of the prospects of LIGA application are put forward by combining the features of synchrotron radiation lithgraphy

ちょっとＭＥＭＳ 第１１回 放射光リソグラフィーによるプロトタイピング技術とその応用（１）：波長可変型大面積リソグラフィー

ちょっとＭＥＭＳ 第１１回 放射光リソグラフィーによるプロトタイピング技術とその応用（１）：波長可変型大面積リソグラフィー

Novel Characteristics of Multifunctional Fluid Filters Fabricated by High-Energy Synchrotron Radiation Lithography

A new method using multifunctional fluid filters with through-capillary arrays for high throughput and large-scale integrated microfluidics is proposed. The method utilizes a liquid's surface tension and fluid flows perpendicular to a substrate using a fluid filter. Utilizing this method, we can minimize the space consumption of microchannels, and enhance the flexibility of channel design, because these are not extant on the surface of substrates as in traditional microfluidics, but are through-capillary arrays passing through the substrates. In addition, the passive multifunctional characteristics of the fluid filter are favorable for the integration of microfluidics. Therefore, the integration number can be increased from the previous order of hundreds to thousands or more. We conducted a computational fluid dynamics (CFD) analysis to examine the feasibility of vertical fluid flow operation; the multifunctionality of the fluid filter as a microvalve, a microchannel and a micromixer was estimated. The fabrication of the fluid filter by deep X-ray lithography and the vertical fluid flow operation were successfully conducted and the high-throughput properties of the vertical fluid flow were demonstrated.

Fabrication of high aspect ratio nano gratings using SR lithography

In this paper, the fabrication technique for high-aspect-ratio diffractive optical element (DOE) is introduced. The 500 nm-width and 1,000 nm-width line-and-space pattern has been successfully fabricated. It was fabricated by synchrotron radiation (SR) lithography for the application of nano gratings, and poly-methylmethacrylate (PMMA) was used as X-ray resist. The nanoscale grating with the aspect ratio of 4.4 and 2.2 was achieved. So far, there are a number of reported techniques for fabrication of DOEs yet the height of those gratings is not sufficient. Therefore, we have attempted to investigate the fabrication of high-aspect-ratio nano gratings by a high-resolution X-ray lithography using SR source at Ritsumeikan University, Japan. Nevertheless, the evaluation of various factors influencing the high-aspect-ratio structure fabricated by our recommended technique is discussed. So far the fabricating process, such as, proximity gap of exposure, the exposure dosage, and the development time have been optimized to fabricate the gratings.

Three-dimensional patterning using fine step motion in synchrotron radiation lithography

A simple method of fabricating blazed diffraction gratings using synchrotron radiation lithography was developed that employs an ordinary binary mask with a line-and-space pattern, a step-and-expose procedure that provides a linear cumulative-dose distribution, and a thick resist with a linear sensitivity curve. This method enables the fabrication of blazed gratings with a grating pitch of 1μm and a blaze angle of 15°–40°. The angle and pitch can be changed by changing the dose from step to step and/or by using mask spaces of different widths.

ＳＲリソグラフィを用いて製作した複合圧電材料の内部共振

A ceramic micro fabrication process has been developed for the 1-3 piezo-electric composites which is suitable for high frequency, wideband ultrasonic transducer. This process employs synchrotron radiation (SR) lithography and a micro molding process. This process realized an array of lead zirconate titanate (PZT) rods whose cross section is 25 microns. The material is expected to improve the resolution of the ultrasonic diagnosis, because composites can transmit a short ultrasonic pulse and have high sensitivity. In addition, when circular shape PZT rods is arranged at the apex of the regular triangle, the internal resonant mode became clear to be suppressed.

Flow measurements below 50 μm: NMR microscopy experiments in lithographic model pore spaces

Quasi two-dimensional random site percolation model objects have been prepared using a synchrotron radiation lithography technique with a spatial resolution better than 50 microm and an aspect ratio of up to 17. Flow of water through the pore space was studied with the aid of an NMR velocity mapping method and compared with a computational fluid dynamics simulation. In order to be able to measure and map widely distributed flow velocities with microscopic resolution (typically 40 x 40 microm), an experimental protocol that permits one to cover an effectively very wide velocity field of view (0.6-10 mm/s) had to be developed.

Dot Array Microoptics for Lighting Panel Using Synchrotron Radiation Lithography

The lighting-panel (LP) for liquid crystal displays (LCDs), which leads the light from the illuminating light emitting diode (LED) to the front panel, is one of the key parts of personal digital assistants (PDAs) for decreasing the power consumption. We developed a high luminosity LP for LCDs with accurate three dimensional microstructures using synchrotron radiation lithography, and their optical properties were also evaluated using the luminosity distribution measurement. The mean luminosity and the luminescence efficiency were more than 800 cd/m2. It is notable, from the simulation results, that the mean luminosity for the LP with trapezoidal cylindrical dots increases to 1.5 times higher than that of the LP with cylindrical dots. Qualitatively, the measured result corresponds well with the simulated results.

Three-dimensional micro/nanostructures formed by synchrotron radiation lithography

Three-dimensional micro/nanostructures formed by synchrotron radiation lithography

Effects of Improved Microchannel Structures on the Separation Characteristics of Microchip Capillary Electrophoresis

We fabricated the electrophoresis microchips using the UV polymerization technique. We employed plastic substrates that were suitable for rapid prototyping instead of glass and quartz. A thick UV negative photo resist was used to form molds and poly-dimethylsilozane (PDMS) was polymerized by a thermal curing process on the mold to obtain replica microchips. Electroosmotic flow (EOF) was measured to evaluate the surface. Rhodamine B and sulforhodamine B are successfully separated using the microchip. Characteristic differences between UV-fabricated and SR-fabricated microchips were evaluated by EOF measurement. It was observed that accurately defined microchannels fabricated by synchrotron radiation (SR) lithography show constant peak heights and FWHMs. Thus the advantage of the application of SR lithography to the mold fabrication is also demonstrated.

LIGA process – micromachining technique using synchrotron radiation lithography – and some industrial applications

We developed the LIGA (Lithographie or lithography/Galvanoformung or electroforming/Abformung or molding) process using a compact synchrotron radiation (SR) source. To make a compact SR source applicable for the LIGA process, we developed a highly sensitive resist and highly transparent mask for deep SR lithography. We commercialized two devices, a piezoelectric composite and a microprobe for IC testing. A microconnector and optical switch were also developed.

Growth of suspended carbon nanotube networks on 100-nm-scale silicon pillars

We investigated carbon nanotube growth by means of methane chemical vapor deposition on ultrafine silicon patterns prepared by synchrotron-radiation lithography. Grown nanotubes formed suspended bridges between pillars when pillar spacing was comparable to pillar height. Network-like interconnections were obtained on pillar arrays. Nearest-neighbor bridging accounted for more than 80% of all the bridging nanotubes. The self-directed growth between neighboring pillars may be explained by the swing of the nanotube cantilever which contacts a catalyst particle in liquid phase as the nanotube grows. These results confirm the possibility of self-assembled wiring of nanostructures.

Adhesion and Cohesion Properties of Dot Resist Patterns Ranging from 84 to 364 nm Diameter Analyzed by Direct Peeling Method with Atomic Microscope Tip.

By directly applying a load to top corner of a resist pattern with a microcantilever tip, a dot resist pattern adhering on a flat substrate can be collapsed easily by accompanied with slight residue. By the synchrotron radiation (SR) lithography, the dot resist patterns ranging from 84 to 364nm diameter and 550nm height are formed on the Si(100) substrate. The static load applied by the cantilever, which is required for pattern collapse, decreases with decreasing the pattern diameter and is proportional to the cross-sectional area of the resist pattern. In combination with the stress distribution analysis, the mechanism of pattern collapse and residue formation can be clarified. The pattern collapse occurs by the stress concentration at the pattern bottom slightly away from the interface. It is clear that the pattern collapse can be dominated by the stress concentration in the resist pattern.

Compact synchrotron radiation lithography system for 70 nm device manufacturing

We report on the performance and reliability of our synchrotron radiation (SR) based x-ray lithography (XRL) system installed in Tanashi Works of Sumitomo Heavy Industries, Ltd. Our XRL facilities include a compact racetrack-type SR light source “AURORA-2S” (A2S), the injector microtron, a 3-m-long beamline, and the second version x-ray aligner. In 2000, A2S proved the beam lifetime of 16 h in regular operation at the designed beam current 500 mA. The XRL beamline offers a high-dose exposure rate of over 43 mW/cm2 on a wafer at beam current 500 mA. The x-ray aligner achieved an overlay accuracy better than 16 nm (3σ) using a video-based scattered-light alignment (SLA) system. In the SLA, edge scattering on matrix array patterns provides multispot video images for mask to wafer alignment. A 70 nm line and space (L/S) pattern was replicated with a gap of 15 μm. In resolution enhancement exposure, we replicated a 100 nm L/S and 1 100 nm hole pattern using a 200 nm L/S and a 200 nm hole pattern of x-ray mask, respectively.

Patterning Yield of Sub-100-nm Holes Limited by Fluctuation of Exposure and Development Reactions in Synchrotron Radiation Lithography Using Biased Mask Patterns

In this article, we evaluate the patterning yield of sub-100-nm holes limited by the fluctuation of exposure and development reactions in synchrotron radiation (SR) lithography, particularly with the use of biased mask patterns. By increasing the exposure dose as a parameter, yield versus exposure dose and yield versus pattern size for both chemically amplified and conventional resists are investigated under various conditions of exposure and development. By estimating the number of photons contributing to the photochemical reactions in each hole, it is shown that the fluctuation of the absorbed photons is a primary factor limiting the patterning yield around the threshold exposure dose. Improvement of the yield for very fine patterns around the diffraction-limited resolution (50 nm) will be discussed.