A three-dimensional (3-D) integration technology based on the wafer-to-wafer bonding using through silicon vias (TSV's) has been developed for the fabrication of new 3-D LSIs. A 3-D image sensor chip, 3-D shared memory chip, 3-D artificial retina chip and 3-D microprocessor test chip have been fabricated by using this technology. In addition, we have proposed a new reconfigurable parallel image processing system. To achieve this system, we have proposed a new 3-D integration technology based on multichip-to-wafer bonding called a super-chip integration. Many chips are simultaneously aligned and bonded onto lower chips using a self-assembly technique in a super-chip integration.

High density through silicon via (TSV) is a key in fabricating three-dimensional (3-D) large-scale integration (LSI). We have developed polycrystalline silicon (poly-Si) TSV technology and tungsten (W)/poly-Si TSV technology for 3-D integration. In the poly-Si TSV formation, low-pressure chemical vapor deposition poly-Si heavily doped with phosphorus was conformally deposited into the narrow and deep trench formed in a Si substrate after the surface of Si trench was thermally oxidized. In the W/poly-Si TSV formation, tungsten was deposited into the Si trench by atomic layer deposition method after the poly-Si deposition, where poly-Si was used as a liner layer for W deposition. The 3-D microprocessor test chip, 3-D memory test chip, 3-D image sensor chip, and 3-D artificial retina chip were successfully fabricated by using poly-Si TSV.

We have measured, at 57.5 GHz, the reflection and transmission coefficients of typical walls, floor, ceiling, window, and partitions and have compared the measured reflection characteristics with the reflection characteristics estimated by multi-layer dielectric models. Although the positional inhomogeneity of structure types gives rise to some variation from one measured position to another, these positional variabilities are not large, The overall trend of reflection coefficients calculated by multi-layer dielectric models thus mainly agrees well with the trend of the measurements. We have shown that the use of circular polarization can reduce the reflection even if the interior parts of the structure have complicated structures. In addition, the shadowing effects of several types of partitions were measured. The transmission coefficients of partitions depend on the materials. The losses due to plywood partitions are very low, but a metallic partition shields millimeter waves.

The RAKE receiving technique is effective for improving transmission performance of CDMA mobile radio communication systems. To clarify the multipath propagation characteristics for this technique, an experiment is carried out in the Tokyo urban area using a 1.5 GHz band channel sounder, It is found that; (1) the probability of the path number exceeding 2 is 97 percent. (2) The dominant path number is 3. (3) The fade probability is less than the Rayleigh distribution. (4) The RAKE receiving technique is effective for improving transmission performance.