This paper presents a newly developed 3-Dimensional (3-D) simulation system for Moving Mask Deep X-ray Lithography (M 2 DXL) technique, and its validation. The simulation system named X-ray Lithography Simulation System for 3-Dimensional Fabrication (X3D) is tailored to simulate a fabrication process of 3-D microstructures by M 2 DXL. X3D consists of three modules: mask generation, exposure and resist development (hereafter development). The exposure module calculates a dose distribution in resist using an X-ray mask pattern and its movement trajectory. The dose is then converted to a resist dissolution rate. The development module adopted the "Fast Marching Method" technique to calculate the 3-D dissolution process and resultant 3-D microstructures. This technique takes into account resist dissolution direction that is required by 3-D X-ray lithography simulation. The comparison between simulation results and measurements of "stairs-like" dose deposition pattern by M 2 DXL showed that X3D correctly predicts the 3-D dissolution process of exposed PMMA.[1474]

Double exposure in deep x-ray lithography (D2XRL) was proposed for the first time to fabricate three-dimensional (3D) microstructures with inclined walls by common deep x-ray lithography (DXRL) without any special apparatus and complicated exposure process controls. The feasibility of this technique for 3D microfabrication was demonstrated by fabricating micro-projection arrays. Then, a determination procedure for important process parameters of D2XRL, i.e., the dependence of absorbed dose on depth from a resist surface and the dependence of the dissolution rate on the absorbed dose, was proposed. By applying this procedure, the prediction of the micro-projection in D2XRL was carried out. It was confirmed that the processed structural shape was predicted successfully using the proposed procedure with an acceptable accuracy.

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This paper reports a novel fabrication process of 3 dimensional (3-D) microstructures by double X-ray exposure in standard deep X-ray lithography (DXL). The proposed fabrication process made it possible to realize 3-D microstructures with an inclined and curved sidewall without any apparatuses and difficult process control. In order to demonstrate the feasibility of the double X-ray exposure technique, a micro-needle array fabrication was carried out. The sharp micro-needle array with the top radius of less than 100 nm was easily and successfully fabricated by the double X-ray exposure method.

This paper proposed an analysis for the piezoresistive property of heavily-doped polycrystalline silicon (polysilicon) with upper and lower bounds derived using the fundamental piezoresistive coefficients of single-crystalline silicon (SCS). The analysis is applicable to the polysilicon that the piezoresistive effect in grain boundaries is negligible and the orientations of the SCS grains are completely random. For deriving the upper and lower bounds, the analysis employed two approximation models on the basis of two extreme assumptions of uniform stress and fractional change in resistivity in each SCS grain of polysilicon. The fundamental piezoresistive coefficients of polysilicon derived from these models were successfully defined as the upper and lower bounds, based on the elastic theories in the micromechanics filed. The applicability of the analysis was discussed by comparing the derived upper and lower bounds with the piezoresistive property of heavily-doped polysilicon measured in some previous works. The measured piezoresistive property of both p-type and n-type polysilicon lay within the theoretical possible range between the upper and lower bounds at the impurity concentration of 1019 cm−3 levels, which suggested the applicability of the proposed analysis for the piezoresistive property of heavily-doped polysilicon.