An advanced technology using a multiple moving X-ray mask deep X-ray lithography (M³DXL) to realize various microstructures with inclined or free shape side wall, namely 3-dimensional microstructures, was proposed. The side wall shape of a PMMA microstructure fabricated by deep X-ray lithography has bean controlled by moving X-ray masks in parallel with the PMMA substrate during X-ray exposure. In order to demonstrate the feasibility of this M³DXL technology, various microstructures were successfully fabricated; (1) conical shape and truncated conical shape microstructures with height of 100-300μm and a diameter of 0-310μm and (2) grooves with saw shape cross section with depth of about 30μm and width of 100-150μm.

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We have clarified the effect of potassium ion addition to TMAH solution on orientation dependence of etching rate in silicon anisotropic etching and etched surface roughness. Hemispherical specimen of single crystal silicon and wagon wheel pattern were used for experiments. The etching rate in <011> direction decreases dramatically, etching rate in <111> direction increases and surface roughness decreased with adding potassium ion in TMAH.

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We have been developing a novel fabrication method for 3-D microstructures using surface-activated bonding (SAB) of thin films. This method is a kind of layer manufacturing method for metallic or dielectric microstructures with an accuracy of sub-micrometers. In our method called FORMULA (Formation of μ-structures by lamination), all sliced patterns for microstructures are first formed on a donor substrate by photolithography, then they are transferred and laminated onto a target substrate using SAB. The transfer of thin film patterns without any damage is an essential in this method. Adhesion strength of thin films on the donor substrate should be controlled regarding the photolithography process and the bonding strength. The condition for the complete transfer of thin film patterns is discussed. A mechanism assuring paralleling of the bonding surfaces was effective to improve the bonding results. Uniformity in elastic contact pressure distribution over the bonding area was essential for the uniformity in bonding.

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It is necessary for practical and high performance MEMS to be fabricated microstructures with sub-micron widths and gaps (lines and spaces). In sub-micron deep X-ray lithography, one of the most crucial considerations is the fabrication of an X-ray mask with thick X-ray absorbers having sub-micron width. An X-ray mask, which was composed of 1μm thick Au with a 0.6μm line width and a 0.2μm space as absorbers, 2μm thick SiC with 240MPa of tensile stress as a membrane and 625μm thick Si as a frame, was fabricated. In order to reduce the influence of Fresnel diffraction, a PMMA resist was polymerized without residual stress, which had been the main cause of a warp in the substrate, by controlling of the polymerization process. As a result, a sub-micron PMMA structure with a maximum aspect ratio of 85, corresponding to 0.2μm minimum width, 6μm length and 17μm height, was fabricated by deep X-ray lithography.

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The handling of fine structure objects consisting of micrometer-sized polystyrene latex particles by laser scanning manipulation technique using a single laser beam was demonstrated. Laser ablation technique was employed to fix polymer particles regularly aligned by laser trapping. Integrated structures created by the successive trapping/laser ablation procedures were shown to be held by laser beam. When the trapping laser beam was scanned along the rod structure, the structure was stably held with the swinging motion of few hundreds nanometer. The swinging motion of the structure was strongly dependent on the scanning speed(V_S) of the laser beam, and swinging amplitude was reduced as V_S increased. The holding ability of the microstructure was proportional to the laser power. The present method is promising as a technique for precision holding of minute structures.

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The properties and mechanism of silicon protuberance and groove processing by diamond tip sliding using atomic force microscope (AFM) in an atmosphere were studied. To control the height of protuberance and the depth of groove, the processed height and depth dependencies on load and diamond tip radius were evaluated. Diamond tip of about 200nm radius sliding produces 0-5nm height protuberances on the silicon surface. In contrast, about 50nm radius tip sliding produces 0-20nm deep grooves on the silicon surface. Protuberance height processed with 200nm tip and groove depth processed with 50nm tip increase with applied load increase. Using about 100nm radius tip both protuberance and groove are produced. The hardness of processed parts is higher than that of unprocessed parts, therefore, oxidation of silicon is speculated to be caused at the rear edge of sliding contact area that the elongation stress is the highest. As application of this processing, the three dimensional nano profiles such as, 300nm×300nm square, lines and spaces with 100nm period and the standard rulers processed on silicon diffraction grating were performed.

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A silicon shadow mask for evaporation or sputtering of any shape of patterns was fabricated by Al-Delay Masking Process (DMP). Using DMP, a Si high aspect ratio structure having arbitrary number of multiple-depth can be fabricated. By applying two layers of DMP, Si shadow mask with a mechanical alignment structure was fabricated. A Si chip on which deposition should be performed was successfully inserted to the mechanical alignment structure by tweezer, ensuring the high alignment precision less than ±5μm of the shadow mask aperture to the chip. With three layers of DMP, a shadow mask for deposition of a doughnuts-like shape was fabricated. The successful deposition of the doughnuts-like shape showed the large freedom of deposition patterns.

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We have developed a microconnector with an automatic connecting/disconnecting mechanism employing magnetic force. The diameter and thickness of the microconnector is 2.5-mm and 2-mm, respectively. To obtain a large area and reliable connection, the terminals and guides must be perpendicular to the substrate of the microconnector and have high aspect ratios. These structures are fabricated using the LIGA-like process. The cantilever shape terminals as moving structures (7-μm-width, 80-μm-height and 300-μm-length) were fabricated using the one-layer sacrificial process. The tapered terminals and guides for the smooth connection were fabricated by micro-electro-discharge-machining combined with the LIGA-like process. We confirmed the electrical cronnection at 160mA/line and the automatic connection (disconnection) at a distance of 600-μm between opposing microconnectors.

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We have developed a new type of micro stereolithography to make a microstructure with multiple UV polymers. This process provides us total-polymer-based microdevices (Polymer MEMS) by ingeniously combining various UV polymers with different characteristics: refractive index, conductivity, Young's modulus. For example, the difference in refractive index can be utilized many optical devices like optical waveguides, photonic crystals, etc. Actually we succeeded to fabricate optical waveguides with two kinds of UV polymers having different refractive indexes. The fabrication system consists of laser scanning system, roller pumps to supply UV polymers, a cylinder for the store of UV polymers. We can easily switch several UV polymers by choosing roller pumps during fabrication process. This process opened "Polymer MEMS" technology giving great contribution to micro optics and micro-chemical devices.

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We have carried out three-dimensional (3-D) micromachinig of PTFE with the TIEGA process, a LIGA-like process which by replaces hard x-ray lithography with synchrotron radiation (SR) direct-photo etching. The etching rates are of the order of 100μm/min. A metallic wire covered with a PTFE sheet is rotated and/or moved while being irradiated with SR through a mask. The capabilities of these technologies and initial fabrication results are described in this paper.

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