Tomoaki Yoshizawa

A 90-nm low-power 32-kB embedded SRAM with gate leakage suppression circuit for mobile applications

In sub-100-nm generation, gate-tunneling leakage current increases and dominates the total standby leakage current of LSIs based on decreasing gate-oxide thickness. Showing that the gate leakage current is effectively reduced by lowering the gate voltage, we propose a local dc level control (LDLC) for SRAM cell arrays and an automatic gate leakage suppression driver (AGLSD) for peripheral circuits. We designed and fabricated a 32-kB 1-port SRAM using 90-nm CMOS technology. The six-transistor SRAM cell size is 1.25 /spl mu/m/sup 2/. Evaluation shows that the standby current of 32-kB SRAM is 1.2 /spl mu/A at 1.2 V and room temperature. It is reduced to 7.5% of conventional SRAM.

Worst-case analysis to obtain stable read/write DC margin of high density 6T-SRAM-array with local Vth variability

6T-SRAM cells in the sub-100 nm CMOS generation are now being exposed to a fatal risk that originates from large local Vth variability (/spl sigma//sub v/spl I.bar/Local/). To achieve high-yield SRAM arrays in presence of random /spl sigma//sub v/spl I.bar/Local/ component, we propose worst-case analysis that determines the boundary of the stable Vth region for the SRAM read/write DC margin (Vth curve). Applying this to our original 65 nm SPICE model, we demonstrate typical behavior of the Vth curve and show new criteria for discussing SRAM array stability with Vth variability.

A 90nm dual-port SRAM with 2.04 /spl mu/m/sup 2/ 8T-thin cell using dynamically-controlled column bias scheme

A high-density dual-port SRAM (DP-SRAM) with a 2.04 /spl mu/m/sup 2/ cell size is implemented in 90 nm CMOS technology. A dynamically-controlled column-bias scheme is presented, which reduces the active power by 64% and the stand-by current by 93%.

A 99-mm/sup 2/, 0.7-W, single-chip MPEG-2 422P@ML video, audio, and system encoder with a 64-Mbit embedded DRAM for portable 422P@HL encoder system

A scalable single-chip 422P@ML MPEG-2 video, audio, and system encoder LSI for portable 422P@HL system is described. The encoder LSI is implemented using 0.13 /spl mu/m embedded DRAM technology. It integrates 3-M logic gates and 64-Mbit DRAM in an area of 99-mm/sup 2/. The power consumption is suppressed to 0.7-Watts by adopting a low power DRAM core. It performs real-time 422P@ML video encoding, audio encoding, and system encoding with no external DRAM. Furthermore, the encoder LSI realizes a 422P@HL video encoder with multi-chip configuration, due to its scalable architecture. This results in a PC-card size 422P@HL encoder with lowest power consumption for portable HDTV codec system.

A Large Scale, Flip-Flop RAM imitating a logic LSI for fast development of process technology

We propose a new, large-scale, logic TEG, which is called flip-flop RAM (FF-RAM), to improve the total process quality before and during initial mass production. It is designed to be as convenient as an SRAM for measurement and imitates a logic LSI. We implemented a 10-Mgate FF-RAM using our 65 nm CMOS process. The test results show that it is effortless to detect failure locations and layers by using fail bit maps. Owing to this TEG, we can significantly shorten the development period for advanced CMOS technology.

A Large-Scale, Flip-Flop RAM Imitating a Logic LSI for Fast Development of Process Technology

We propose a new, large-scale, logic TEG, which is called flip-flop RAM (FF-RAM), to improve the total process quality before and during initial mass production. It is designed to be as convenient as an SRAM for measurement and imitates a logic LSI. We implemented a 10-Mgate FF-RAM using our 65 nm CMOS process. The test results show that it is effortless to detect failure locations and layers by using fail bit maps. Owing to this TEG, we can significantly shorten the development period for advanced CMOS technology.