Hwan-Wook Park

A 31 ns Random Cycle VCAT-Based 4F

A functional 4F2 DRAM was implemented based on the technology combination of stack capacitor and surrounding-gate vertical channel access transistor (VCAT). A high performance VCAT has been developed showing excellent Ion-Ioff characteristics with more than twice turn-on current compared with the conventional recessed channel access transistor (RCAT). A new design methodology has been applied to accommodate 4F2 cell array, achieving both high performance and manufacturability. Especially, core block restructuring, word line (WL) strapping and hybrid bit line (BL) sense-amplifier (SA) scheme play an important role for enhancing AC performance and cell efficiency. A 50 Mb test chip was fabricated by 80 nm design rule and the measured random cycle time (tRC) and read latency (tRCD) are 31 ns and 8 ns, respectively. The median retention time for 88 Kb sample array is about 30 s at 90°C under dynamic operations. The core array size is reduced by 29% compared with conventional 6F2 DRAM.

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This paper proposes a deca-data rate clocking scheme and relevant I/O circuit techniques for a multi-Gb/s/pin memory interface. A deca-data rate scheme transmits 10 bits in one external clock cycle to transfer an error control code along with original data seamlessly without a timing bubble. A 288 Mb SDRAM has been designed using the proposed scheme combined with fast cycling core techniques to have both high I/O bandwidth and fast random cycling. Measured results show that the chip exhibits per-pin data rate of 8 Gb/s and row cycle time of 9.6 ns

DRAM With Manufacturability and Enhanced Cell Efficiency

A 7Gb/s single ended transceiver with low jitter and ISI is implemented in 40nm DRAM process. DRAM optimized LC PLL achieves inductor Q of 3.86 and results in random jitter of 670fs rms. A clock tree regulator with closed loop replica path reduces low as well as high frequency noise. RX 2-tap hybrid DFE combining sampling and integration methods reduces power and area by 37% and 24%, compared to the integrating DFE. Moreover, on-chip de-emphasis circuit in TX multiplexer reduces ISI of both on and off chip.

An 8 Gb/s/pin 9.6 ns Row-Cycle 288 Mb Deca-Data Rate SDRAM With an I/O Error Detection Scheme

A 1-Gbit DRAM with 5.8-Gb/s/pin unidirectional differential I/Os was implemented by 70 nm DRAM process and a main memory module with dual in-line memory module was assembled. The implemented DRAM chips have control methods for core noise injection and a cyclic redundancy check (CRC) generator for outer-data inner-command architecture. Measurements for bit error rate and jitter performance of the transmitter was performed on an electrical test board which emulates the real memory systems environment. Also, the effect on power noise was analyzed from the DRAM chips with three class values of power decoupling capacitance for the peripheral part. The results show that no additional coding for the differential I/O protection in DRAM, like CRC, is required up to 5.8-Gb/s/pin operation.

A 40nm 7Gb/s/pin single-ended transceiver with jitter and ISI reduction techniques for high-speed DRAM interface

A 5.8 Gb/s/pin DRAM with unidirectional differential I/Os and 1 Gbit memory core was designed and 23.2 GB/s memory module was assembled. Tx BER measurement on an electrical test board similar to real memory sub-systempsilas environment was performed and the results show that no additional coding for the differential I/O protection, like CRC, seems to be required up to 5.8 Gb/s/pin operation. Also, an efficient timing usage method using matched path for a possible implementation of CRC computation in ODIC architecture was proposed.