Michihiro Yamada

A 45-ns 64-Mb DRAM with a merged match-line test architecture

A single 3.3-V 64-Mb dynamic RAM (DRAM) with a chip size of 233.8 mm/sup 2/ has been fabricated using 0.4- mu m CMOS technology with double-level metallization. The dual-cell-plate (DCP) cell structure is applied with a cell size of 1.7 mu m/sup 2/, and 30-fF cell capacitance has been achieved using an oxynitride layer (t/sub eff/=5 nm) as the gate insulator. The RAM implements a new data-line architecture called the merged match-line test (MMT) to achieve faster access time and shorter test time with the least chip-area penalty. The MMT architecture makes it possible to get a RAS access time of 45 ns and reduces test time by 1/16000. A parallel MMT technique, which is an extended mode of MMT, leads to the further test-time reduction of 1/64000. Therefore, all 64 Mb are tested in only 1024 cycles, and the test time is only 150 mu s with 150-ns cycle time. >

A 4-Mbit DRAM with folded-bit-line adaptive sidewall-isolated capacitor (FASIC) cell

A 5-V 4-Mb word/spl times/1-b/1-Mb word/spl times/4-b dynamic RAM with a static column model and fast page mode has been built in a 0.8-/spl mu/m twin-tub CMOS technology with single-metal, two-polycide, and single poly-Si interconnections. It uses an innovative folded-bit-line adaptive sidewall-isolated capacitor (FASIC) cell that measures 10.9 /spl mu/m/SUP 2/ and requires only a 2-/spl mu/m trench to obtain a storage capacitor of 50 fF with 10-nm SiO/SUB 2/ equivalent dielectric film. A shared-PMOS sense-amplifier architecture used in this DRAM provides a low power consumption, small C/SUB B/-to-C/SUB S/ capacitance ratio, and accurate reference level for the nonboosted word-line scheme with little area penalty. These concepts have allowed the DRAM to be housed in the industry standard 300-mil dual-in-line package with performances of 90-ns RAS access time and 30-ns column address access time.

AN ADDRESS MASKABLE PARALLEL TESTING FOR ULTRA HIGH DENSITY DRAMS

This paper describes a new memory array architecture and its related test method named column address-maskable parallel-test (CMT) architecture, suitable for ultra high density DRAMs. We adopt the column address masking technique to achieve effective parallel testing with the least area penalty. The CMT architecture makes it possible to handle various test patterns and to search failed addresses quickly during parallel test operation. In an experimental 64M-bit DRAM, the test time has been reduced to V16K with an area penalty of less than 0.1%.

Design methodology of embedded DRAM with virtual-socket architecture

This paper proposes the virtual-socket architecture in order to reduce the design turn-around time (TAT) of the embedded DRAM. The required memory density and the function of the embedded DRAM are system dependent. In the conventional design, the DRAM control circuitry with the DRAM memory array is handled as a hardware macro, resulting in the increase in design TAT. On the other hand, our proposed architecture provides the DRAM control circuitry as a software macro to take advantage of the automated tools based on synchronous circuit design. With array-generator technology, this architecture can achieve high quality and quick turn-around time (QTAT) of flexible embedded DRAM that is almost the same as the CMOS ASIC. We applied this virtual-socket architecture to the development of the 61-Mb synchronous DRAM core using 0.18-/spl mu/m design rule and confirmed the high-speed operation, 166 MHz at CAS latency of two, and 180 MHz at that of three. The experimental results show that our proposed architecture can be applied to the development of the high-performance embedded DRAM with design QTAT.

A high-speed 64K/spl times/4 CMOS DRAM using on-chip self-timing techniques

The duration of internal operation of this DRAM is controlled by on-chip self-timing signals. With this feature, the leading and trailing edges of the row address strobe are allowed to have timing windows of 16 and 11 ns, respectively, even at a minimum cycle time of 80 ns. A novel address decoding scheme, utilizing a combination of NMOS NOR row decoders, CMOS NAND column decoders, and common predecoders, is employed to realize a fast array access time and a small die. The RAM has been fabricated with a 1.2-/spl mu/m n-well CMOS technology, and has a 21.34-mm/SUP 2/ die. Typical row access and column address access times are 47 and 16 ns, respectively. The active power dissipation is 115 mW at 200-ns cycle time.

A 70 ns 256K DRAM with bit-line shield

A 256K/spl times/1 dynamic RAM has been developed in a triple-poly, single-metal NMOS technology with a open bit-line architecture. Noncommon-mode noise inherent in the architecture is shielded by a third-level polysilicon plate placed between bit lines and signal lines. The die is 30.2 mm/SUP 2/ and is housed in the standard 300-mil and 16-pin dual-in-line plastic package. The RAM has a worst-case access time of 70 ns. Wire bonding of an extra bonding pad determines whether the RAM is for nibble mode or for page mode; this, it is noted, gives much flexibility to production. Laser repairable redundancy with eight spare columns is implemented for yield enhancement.

A CMOS Dual Port Memory with Serial Read/Write Function for Graphic Systems

As the cost per bit of semiconductor memories and the price of small computer systems continue lowering, personal work stations or computer aided design (CAD) systems come to be used widely. The market for graphic display systems also expands, because interactive operations between users and such systems are unavoidable in personal usage.

An effect of the subthreshold current on scaled-down MOS dynamic RAMs

Data-output holding characteristics of MOS dynamic RAMs with 2.5 /spl mu/m design rules are studied by employing the hidden-RAS-only-refresh mode. It is verified that the noise voltage caused by internal circuit operation increases the subthreshold current and that the clamp circuitry effectively decreases the subthreshold current.