Mitsumasa Koyanagi

Bio: Mitsumasa Koyanagi is an academic researcher. The author has contributed to research in topics: System in package & Scale (ratio). The author has an hindex of 1, co-authored 2 publications receiving 261 citations.

High-Density Through Silicon Vias for 3-D LSIs : Silicon stacked chips that perform highly-parallel data transfer have been successfully fabricated for image processing, artificial retinas, and for microprocessor and memory testing

Abstract: 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 chem- ical 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.

A study of Through-Silicon-Via impact on the 3D stacked IC layout

Abstract: Through-Silicon-Via (TSV) is the enabling technology for the fine-grained 3D integration of multiple dies into a single stack. These TSVs occupy non-negligible silicon area because of their sheer size. This significant silicon area occupied by the TSVs and the interconnections made to the TSVs greatly affect area, power, performance, and reliability of 3D IC layouts. Well-managed TSVs alleviate congestion, reduce wirelength, and improve performance, whereas excessive TSVs not only increase the die area, but also have negative impact on many design objectives. In this paper, we study the impact of TSV on various aspects of 3D layouts. We use GDSII layouts of 2D and 3D designs, and thoroughly compare the pros and cons of TSV usage. We propose a new force-directed 3D gate-level placement that efficiently handles TSVs. In addition, we present an algorithm that assigns TSVs to nets to complete routing that involves TSVs. This algorithm, together with our 3D placer, is integrated into a commercial P&R tool to generate fully validated GDSII layouts. Our experiments based on synthesized benchmarks indicate that our algorithms help generate GDSII layouts of 3D designs that are optimized in terms of area, wirelength, and metal layer count.

InFO (Wafer Level Integrated Fan-Out) Technology

Abstract: A powerful integrated fan-out (InFO) wafer level system integration (WLSI) technology has been developed to integrate application processor chip with memory package for smart mobile devices. This novel InFO technology is the first high performance Fan-Out Wafer Level Package (FO_WLP) with multi-layer high density interconnects proposed to the industry. In this paper we present the detailed comparison of InFO packages on package (InFO_PoP) with several other previously proposed 3D package solutions. Result shows that InFO_PoP has more optimized overall results on system performance, leakage power and area (form factor) than others, to meet the ever-increasing system requirements of mobile computing. InFO technology has been successfully qualified on package level with robust component and board level reliability. It is also qualified at interconnect level with high electromigration resistance. With its high flexibility and strong capability of multi-chips integration for both homogeneous and heterogeneous sub-systems, InFO technology not only provides a system scaling solution but also complements the chip scaling and helps to sustain the Moore's Law for the smart mobile as well as internet of things (IoT) applications.

On-Chip TSV Testing for 3D IC before Bonding Using Sense Amplification

Abstract: We present a novel testing scheme for TSVs in a 3D IC by performing on-chip TSV monitoring before bonding, using a sense amplification technique that is commonly seen on a DRAM. By virtue of the inherent capacitive characteristics, we can detect the faulty TSVs with little area overhead for the circuit under test.

On-chip testing of blind and open-sleeve TSVs for 3D IC before bonding

Abstract: Pre-bond test is preferred for a three-dimensional integrated circuit (3D IC), since it reduces stacking yield loss and thus saves cost. In this paper, we present two schemes for testing through-silicon vias (TSVs) by performing on-chip screening before wafer thinning and bonding. The first scheme is for blind TSVs, which have one end floating, using a charge-sharing technique commonly seen in DRAM. The second scheme is for open-sleeve TSVs, which have one end shorted to the substrate, using a voltage-dividing technique commonly seen in ROM. By virtue of the inherent capacitive and resistive characteristics, we detect the TSVs out of a specified range as anomalies, taking into account the effects of process variations in the detection circuitry. The statistical design by Monte Carlo simulation using TSMC 65nm low-power process shows that for blind TSVs, the best overkill ratio is below 6%. For open-sleeve TSVs, inherent limitations restrict the applicability, so more work needs to be done in the future. Our implementation enjoys little area overhead, requiring only a simple sense amplifier and a write buffer that are shared among a number of TSVs. Reducing the number of TSVs that share a test module will reduce the test time, but increase the area overhead. For blind TSVs, the parallelism also affects the overkill and escape rates.