We demonstrated fabricating a needle array of polycarbonate (PC) and polymethyl methacrylate (PMMA) by using a 3-D LIGA (lithografie, galvanoformung, abformung) process. The diameter of the bottom of the needle was about 50 µm, and the height was 135 µm. Although the LIGA process is commonly applied for making structures with vertical sidewalls, the use of an x-ray grayscale mask in the LIGA process has made it possible to fabricate needle-shaped structures. The x-ray grayscale mask was composed of a Si x-ray absorber and an SU-8 membrane. The sidewall of the x-ray absorber was diagonally processed by Si tapered-trench-etching technology such that the transmission intensity of x rays could be changed locally. The x-ray lithography experiment was executed by using this x-ray grayscale mask on a beamline BL-4 in the TERAS synchrotron radiation facility at National Institute of Advanced Industrial Science and Technology (AIST). By using this facility, a PMMA resist master with three-dimensional (3-D) structures was made. A Pt layer was then sputter-deposited as a seed layer on the PMMA resist master, and a Ni mold was fabricated by electroforming technology. In addition, a needle array of PC and PMMA was produced by hot embossing technology. Self-assembled monolayers (SAMs) of a release agent were required on the surface of the mold pattern to achieve a complete molding. Thus, we succeeded in extending the LIGA process to three dimensions by the use of an x-ray grayscale mask.
Our recent development of transition-edge sensor (TES) microcalorimeters for future X-ray astronomical missions
such as DIOS is reported. In-house micromaching processes has been established aiming at prompt fabrication
of TES devices. With a single-pixel TES microcalorimeter and an Au absorber, the energy resolution of 4.8 eV
at 5.9 keV is achieved. 16×16 pixel arrays of TES microcalorimeters are successfully fabricated by using deep
dry etching technique. The energy resolution is 11 eV and 26 eV with and without an Au absorber, respectively.
The worse energy resolution than a single-pixel TES is due to large decrease of TES sensitivity and increase
of transition temperature after etching. The reason for these phenomena is under investigation. In parallel,
mushroom-type Au absorber structures are being tested. Furthermore, to precisely measure TES sensitivities
and heat capacity, an experimental setup for impedance measurements is established.
We have succeeded in fabricating a needle array of polycarbonate by using a three-dimensional LIGA process. The diameter of the bottom of the needle was about 50 μm, and the height was 135 μm. Although a usual LIGA process has been employed to form structure only with vertical sidewalls, it has now become possible to fabricate needle shape structure by employing a technology that combines X-ray gray mask with the LIGA process. The X-ray gray mask was composed of Si X-ray absorbers and a SU-8 membrane. The sidewall of the X-ray absorber was diagonally processed by Si tapered-trench-etching technology where the transmission intensity of X-rays could be varied locally. An X-ray lithography experiment was executed by using the X-ray gray mask on a beamline BL-4 in TERAS synchrotron radiation facility at AIST. Using this technology a PMMA resist master with three-dimensional structures was made. A Pt layer was sputter deposited as a seed layer on the PMMA resist master, and a Ni mold was fabricated by an electroforming technology. In addition, needle arrays of polycarbonate (PC) and of polymethyl methacrylate (PMMA) were produced by hot embossing technology. Thus, we succeeded in extending the LIGA process to a three-dimensional process capability by employing X-ray gray mask.
Deep reactive ion etching (DRIE) is an important tool in MEMS fabrication to achieve three-dimensional structures.
However, the etching profiles are not yet perfect. We had etching test samples fabricated in three MEMS foundries and
measured the etching rates, sidewall angles, mask selectivity, and sidewall roughness against the line and space of 2 to
5000 μm. We also performed similar DRIE processes using our system and compared our samples and the samples from
the foundries. The measurement results revealed the typical fabrication results in the MEMS foundries and their
differences. The data were included in the database of MemsONE, a newly developed MEMS design software, and can
be used for the process emulations.
We propose a new fabrication method of an x-ray grayscale mask using micro-electro-mechanical-systems (MEMS) technologies, and also report on successful fabrication of three-dimensional (3D) microstructures on a polymethylmethacrylate (PMMA)sheet by using only a single x-ray exposure. We showed that silicon can be diagonally etched by optimizing the etching condition in a reactive-ion-etching (RIE) process. It is well known that the absorbers of an x-ray mask can be made into 3D shapes. Here, we describe how this process can be extended to fabricate an x-ray grayscale mask by using a tapered-trench-etching technique. With such a mask, we carried out experiments on x-ray lithography (XRL) using a beam line BL-4 in the synchrotron radiation facility TERAS of National Institute of Advanced Industrial Science and Technology (AIST). The dose energy used for the exposure was 150 mA·h, and the subsequent resist development was done by a GG developer at room temperature for 16 h. The sidewalls in the upper part of the PMMA resist structure were inclined and rounded. In particular, the shape of the PMMA resist structure of the lines with 20-μm width (also referred as 20-μm lines) could be processed to achieve a halberd-like shape. Thus, the effectiveness of the grayscale mask in adjusting to the varying thicknesses of absorber was confirmed by XRL experiments. Moreover, we showed that the final shape of PMMA resist structures after XRL was predictable by calculations.
The first light of a ultra-lightweight and low-cost micro-pore X-ray optic utilizing MEMS (Micro Electro Mechanical
Systems) technologies is reported. Our idea is to use silicon (111) planes appeared after anisotropic wet
etching of silicon wafers. As a first step to Wolter type-1 optics, a single-stage optic with a focal length of 750
mm and a diameter of 100 mm was designed for energies below 2 keV. The optic consists of 218 mirror chips
for X-ray reflection and an optic mount for packing these chips. Design parameters and required fabrication
accuracies were determined with numerical simulations. The fabricated optic satisfied these accuracies and its
imaging quality was measured at the ISAS X-ray beam line at Al Kα 1.49 keV. A focused image was successfully
obtained. The measured image size of ~4 mm was consistent with the chip sizes. The estimated X-ray reflectivity
also could be explained by micro-roughness of less than 3 nm and geometrical occulting effect due to large
obstacle structures on the reflection surface.
We proposed a new fabrication method of an X-ray gray mask using MEMS technologies, and we also succeeded in
fabricating three-dimensional microstructures on a PMMA sheet by using only a single X-ray exposure. Silicon can be
diagonally etched by optimizing the etching condition in a RIE process. We thought X-ray absorbers of an X-ray mask
were processed to three-dimensional shape, and a gray mask for the X-ray lithography was fabricated by using a tapered-trench-
etching technique. Then, we experimented on the X-ray lithography using the beamline BL-4 in the synchrotron
radiation facility TERAS of AIST. The total dose energy was 150 mAxh and the development was performed at the room
temperature for 16 h using a GG developer. Sidewalls in the upper part of the PMMA resist structure were inclined and
rounded. Especially, the shape of the PMMA resist structure of the line width 20 μm was able to be processed to shape
like the target. Thus, the effectiveness of the gray mask that adjusted the thickness of absorber was confirmed by X-ray
lithography experiments. Moreover, we experimentally showed that the final shape of PMMA resist structures after the
X-ray lithography was predictable by the calculation.
Recent development of the extremely light-weight micro pore optics based on the semiconductor MEMS (Micro Electro Mechanical System) technologies is reported. Anisotropic chemical wet etching of silicon (110) wafers were utilized, in order to obtain a row of smooth (111) side walls vertical to the wafer face and to use them as X-ray mirrors. To obtain high performance mirrors with smooth surfaces and a high aspect ratio, several modifications were made to our previous manufacturing process shown in Ezoe et al. (2005). After these improvements, smooth surfaces with rms roughness of the order of angstroms and also a high aspect ratio of 20 were achieved. Furthermore, a single-stage optic was designed as a first step to multi-stage optics. A mounting device and a slit device for the sample optic were fabricated fully using the MEMS technologies and evaluated.
This paper describes the conception and design of a micropump for gas, with no moving or deformable parts, for use on the future sensor network system, which includes environment monitoring. This design is original because of the complete absence of moving parts for the pumping of gas. In fact, fluid movement was obtained by means of repetitive heating and cooling cycles of the gas, in the pump chamber. The prototyping work is on going and the first results are presented with particular emphasis on thermal characterization.
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