A submicrometer megabit DRAM process technology using trench capacitors

This paper describes guidelines for developing a 1-4-Mbit DRAM process, and device/process technologies for fabricating an experimental 1-Mbit DRAM. A single transistor cell combined with a trench capacitor and on-chip ECC technologies has the potential to realize a cell size of 10 µm²without degrading soft error immunity. A depletion trench capacitor, submicrometer n-well CMOS process, Mo-poly gate, and submicrometer pattern formation technologies are developed, and an experimental 1-Mbit DRAM with a cell size of 20 µm²is successfully developed by using these technologies.     

A 400-MHz random-cycle dual-port interleaved DRAM (D/sup 2/RAM) with standard CMOS Process

This paper describes a standard CMOS process based on embedded DRAM macro with dual-port interleaved DRAM architecture (D/sup 2/RAM), which is suitable for the leading edge CMOS LSIs with both high-speed and large-scale memories on a chip. This macro exploits three key technologies: fully sense-signal-loss compensating technology based on the whole detailed noise element breakdowns, the novel striped trench capacitor (STC) cell, and the write-before-sensing (WBS) circuit by decoded write-bus. A 400-MHz random cycle access has been verified for D/sup 2/RAM fabricated by a 0.15-/spl mu/m standard CMOS process.     

A 60-ns 3.3-V-only 16-Mbit DRAM with multipurpose register

A single 3.3-V 16-Mbit DRAM with a 135-mm/sup 2/ chip size has been fabricated using a 0.5- mu m twin-well process with double-metal wiring. The array architecture, based on the twisted-bit-line (TBL) array, includes suitable dummy and space word-line configurations which suppress the inter-bit-line noise and bring yield improvement. The multipurpose register (MPR) designed for the hierarchical data bus structure provides a line-mode test (LMT), copy write, and cache access capability. The LMT with on-chip test circuits using the MPR and a comparator creates a random test pattern and reduces the test time to 1/1000. A field shield isolation and a T-shaped stacked capacitor allow the layout of a 4.8- mu m/sup 2/ cell size with a storage capacitance of 35 fF. These techniques enable the 3.3-V 16-Mbit DRAM to achieve a 60-ns RAS access time and 300-mW power dissipation at 120-ns cycle time.<>     

Trench transistor DRAM cell

A new one-transistor DRAM cell with both the transistor and the capacitor fabricated on the trench sidewalls is described. With the signal stored on the polysilicon node surrounded by oxide, the cell is expected to have a high alpha particle immunity. The cell occupies only 9 µm²using 1-µm design rules. This cell size is sufficiently small to enable a 4-Mbit DRAM of reasonable chip size with these design rules, and possesses further scalability for 16-Mbit DRAM's.     

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.     

NAND-type DRAM-on-SGT

In this brief, we propose a novel NAND-type DRAM-on-surrounding-gate transistor (SGT) architecture for high-density and low-voltage memory. The cell structure is composed of NAND-type DRAM vertically stacked on an SGT and an SGT-type capacitor. A cell size of 4F/sup 2/ can be achieved. Since it operates as a gain cell, it is possible to obtain a sufficient amount of signal charge. The device was fabricated with a 0.8-/spl mu/m lithography system.     

Submicrometer Electron-Beam Direct Writing Technology for 1-Mbit DRAM Fabrication

A 1-Mbit DRAM with 0.5-/spl mu/m minimum linewidth is fabricated using variable shaped e-beam direct writing technology. A simple linewidth control technique using newly developed submicrometer resists is developed to achieve high resolution and better linewidth accuracy. In addition, a highly accurate registration technique is developed to ensure required overlay. These techniques are successfully used to achieve overlay accuracy of 0.04 /spl mu/m(sigma) and linewidth deviation of 0.018 /spl mu/m(sigma) in the fabrication.     

120-ns 128 K*8-bit/64 K*16-bit CMOS EEPROMs

A 1-Mbit CMOS full-featured EEPROM using a 1.0- mu m triple-polysilicon and double-metal process is described. The design is aimed at developing a manufacturable 120-ns 1-Mbit EEPROM with small chip size. Therefore, an advanced memory cell with high read current, an improved differential sensing technique, and an efficient ECC scheme are developed. The differential sensing amplifier utilizes the output of a current sensing amplifier connected to unselected memory as a reference level. The cell size is 3.8*8 mu m/sup 2/ and the chip size is 7.73*11.83 mm/sup 2/. The device is organized as either 128 K*8 or 64 K*16 by via-hole mask options. A 256-byte/128-word page-mode programming is implemented.<>     

A 64-Mb embedded FRAM utilizing a 130-nm 5LM Cu/FSG logic process

A low-voltage (1.3 V) 64-Mb ferroelectric random access memory (FRAM) using a one-transistor one-capacitor (1T1C) cell has been fabricated using a state-of-the-art 130-nm transistor and a five-level Cu/flouro-silicate glass (FSG) interconnect process. Only two additional masks are required for integration of the ferroelectric module into a single-gate-oxide low-voltage logic process. Novel overwrite sense amplifier and programmable ferroelectric reference generation schemes are employed for fast reliable read-write cycle operation. Address access time for the memory is less than 30 ns while consuming less than 0.8 mW/MHz at 1.37 V. An embedded FRAM (eFRAM) density of 1.13 Mb/mm/sup 2/ is achieved with a cell size of 0.54 /spl mu/m/sup 2/ and capacitor size of 0.25 /spl mu/m/sup 2/.     

An embedded DRAM with a 143-MHz SRAM interface using a sense-synchronized read/write

This paper describes a 4-Mb embedded DRAM macro using novel fast random cycle architecture with sense-synchronized read/write (SSR/SSW). The test chip has been fabricated with a 0.15-/spl mu/m logic-based embedded DRAM process and the 1.5-V 143-MHz no-wait row random access operation has been confirmed. Data retention power is suppressed to 92 /spl mu/W owing to the hierarchical power supply and SSR. The macro size is 4.59 mm/sup 2/. The cell occupation ratio of the macro is 46%, which is the same as that of a conventional embedded DRAM macro. The macro size and the data retention power are 30% and 4.6%, respectively, of a 4-Mb embedded SRAM macro fabricated by an identical process.     

DRAM plate electrode bias optimization for reducing leakage current in UV-O/sub 3/ and O/sub 2/ annealed CVD deposited Ta/sub 2/O/sub 5/ dielectric films

A new plate biasing scheme is described which allowed the use of 65% higher supply voltage without increasing the leakage current for the UV-O/sub 3/ and O/sub 2/ annealed chemical-vapor-deposited tantalum pentaoxide dielectric film capacitors in stacked DRAM cells. Dielectric leakage was reduced by biasing the capacitor plate electrode to a voltage lower than the conventionally used value of V/sub cc//2. Ta/sub 2/O/sub 5/ films with 3.9 nm effective gate oxide, 8.5 fF//spl mu/m/sup 2/ capacitance and <0.3 /spl mu/A/cm/sup 2/ leakage at 100/spl deg/C and 3.3 V supply are demonstrated.<>     

A multiplexed 4 Mbit bubble memory device

A 4-Mbit magnetic bubble memory has been designed and demonstrated which is architecturally compatible with an 1-Mbit memory. The design goals for the memory were to achieve user software compatibility and pin-for-pin interchangeability. To achieve this, one key 4-Mbit device feature was additional multiplexing. This was obtained by a novel application of thin-film detectors and replicate generators along with other function designs. The result is a 4 bit/cycle write and read operation and a page length of 512 bits. The margins for the functions are shown to be comparable to those for the 1-Mbit process while the detector signal is over three times larger. The 1-Mbit process is extended to the 4-Mbit device by adding a thin permalloy level which requires one additional critical alignment and scaling geometries to give a 0.75-/spl mu/m minimum feature size on a 5.5-/spl mu/m square memory cell.     

1.5-V single work-function W/WN/n/sup +/-poly gate CMOS device design with 110-nm buried-channel PMOS for 90-nm vertical-cell DRAM

This letter reports on 1.5-V single work-function W/WN/n/sup +/-poly gate CMOS transistors for high-performance stand-alone dynamic random access memory (DRAM) and low-cost low-leakage embedded DRAM applications. At V/sub dd/ Of 1.5-V and 25/spl deg/C, drive currents of 634 /spl mu/A//spl mu/m for 90-nm L/sub gate/ NMOS and 208 /spl mu/A-/spl mu/m for 110-nm L/sub gate/ buried-channel PMOS are achieved at 25 pA//spl mu/m off-state leakage. Device performance of this single work function technology is comparable to published low leakage 1.5-V dual work-function technologies and 25% better than previously reported 1.8-V single work-function technology. Data illustrating hot-carrier immunity of these devices under high electric fields is also presented. Scalability of single work-function CMOS device design for the 90-nm DRAM generation is demonstrated.     

A 2.0-/spl mu/m pixel pitch MOS image sensor with 1.5 transistor/pixel and an amorphous Si color filter

In this paper, an ultrafine pixel size (2.0/spl times/2.0 /spl mu/m/sup 2/) MOS image sensor with very high sensitivity is developed. The key technologies that realize the MOS image sensor are a newly developed pixel circuit configuration (1.5 transistor/pixel), a fine 0.15-/spl mu/m design rule, and an amorphous Si color filter (Si-CF). In the new pixel circuit configuration, a unit pixel consists of one photodiode, one transfer transistor, and an amplifier circuit with two transistors that are shared by four neighboring pixels. Thus, the unit pixel has only 1.5 transistors. The fine design rule of 0.15 /spl mu/m enables reduction of wiring area by 40%. As a result, a high aperture ratio of 30% is achieved. A newly developed Si-CF realizes the 1/10 thickness of that of the conventional organic-pigment CF, giving rise to high light-collection efficiency. With these three technologies combined, a high sensitivity of 3400 electrons/lx/spl middot/s is achieved even with a pixel size of 2.0/spl times/2.0 /spl mu/m/sup 2/.     

Nano-Watt silicon-on-sapphire ADC using 2C-1C capacitor chain

An analogue-to-digital converter (ADC) in a 0.5 /spl mu/m silicon-on-sapphire CMOS technology is reported. This innovative ADC uses a 2C-1C capacitor chain and a switched capacitor comparator. The ADC is capable of sampling at 409 kS/s, consuming 900 nW at 1.1 V power supply and 1.35 /spl mu/W at 1.5 V. It uses an active area of 300/spl times/700 /spl mu/m/sup 2/ and 640/spl times/1070 /spl mu/m/sup 2/ with pads.     

A substrate-plate trench-capacitor (SPT) memory cell for dynamic RAM's

A (dynamic random-access memory) DRAM cell using a trench capacitor with a grounded substrate plate has been demonstrated, fabricated of functional fully decoded 64K arrays. The cell array is located inside the well and the trench capacitor extends from the planar surface through the well and epitaxial layer into the heavily doped substrate. The polysilicon inside the trench, connected to the source region of the transfer device, is used as the storage node and the bulk silicon surrounding the trench serves as the capacitor plate electrode. The cell features small area, high capacitance, small leakage current, low soft error rate, reduced surface topography, and a very stable capacitor-plate electrode. The arrays were fabricated in an advanced, 3.3-V, n-well epitaxial CMOS technology with a 15-nm gate insulator. The n- and p-channel transistors, exhibit transconductances of 120 and 650 mS/mm, respectively, at effective channel lengths of 6.0 /spl mu/m. Ring oscillators designed at this length have delays of 170 ps at 3.3 V.     

A novel technique for fabricating high reliable trench DMOSFETs using self-align technique and hydrogen annealing

A novel technique for fabricating high reliability trench DMOSFETs using three mask layers is realized to obtain cost-effective production capability, higher cell density and current driving capability, and higher reliability. This technique provides a unit cell with 2.3/spl sim/2.4 /spl mu/m pitch and a channel density of 100 Mcell/in/sup 2/. Specific on-resistance is 0.36 m/spl Omega//spl middot/cm/sup 2/ with a blocking voltage of 43 V at a gate voltage of 10 V and 5 A source-to-drain current. The time to breakdown of gate oxide grown on the hydrogen annealed trench surface is much longer than that of oxide grown on a nonhydrogen annealed trench surface.     

Very high density RF MIM capacitors (17 fF//spl mu/m/sup 2/) using high-/spl kappa/ Al/sub 2/O/sub 3/ doped Ta/sub 2/O/sub 5/ dielectrics

Using high-/spl kappa/ Al/sub 2/O/sub 3/ doped Ta/sub 2/O/sub 5/ dielectric, we have obtained record high MIM capacitance density of 17 fF//spl mu/m/sup 2/ at 100 kHz, small 5% capacitance reduction to RF frequency range, and low leakage current density of 8.9/spl times/10/sup -7/ A/cm/sup 2/. In combination of both high capacitor density and low leakage current density, a very low leakage current of 5.2/spl times/10/sup -12/ A is calculated for a typical large 10 pF capacitor used in RF IC that is even smaller than that of a deep sub-/spl mu/m MOSFET. This very high capacitance density with good MIM capacitor characteristics can significantly reduce the chip size of RF ICs.     

A 1.0-ns 5-kbit ECL RAM

A bipolar 512/spl times/10-bit emitter-coupled logic (ECL) RAM with an access time of 1.0 ns and a power dissipation of 2.4 W, achieving an access-time power/bit product of 0.48 pJ/bit, has been developed. The RAM was fabricated using an advanced bipolar technology featuring poly-base self-alignment, poly-emitter shallow profile, and silicon-filled trench isolation with a minimum mask dimension of 1.2 /spl mu/m. A Schottky-clamped multiemitter cell with a cell size of 760 /spl mu/m/SUP 2/ is obtained as a result of compact cell layout and the use of 1.2-/spl mu/m trench isolation.     

A 312-MHz 16-Mb random-cycle embedded DRAM macro with a power-down data retention mode for mobile applications

An embedded DRAM macro with a self-adjustable timing control (STC) scheme, a negative edge transmission scheme (NET), and a power-down data retention (PDDR) mode is developed. A 13.98-mm/sup 2/ 16-Mb embedded DRAM macro is fabricated in 0.13 /spl mu/m logic-based embedded DRAM process. Co-salicide word lines and MIM capacitors are used for high-speed array operation. The delay timing variation of 36 % for an RC delay can be reduced to 3.8% by using the STC scheme. The NET scheme transfers array control signals to local array blocks with high accuracy. Thereby, the test chip achieves 1.2-V 312-MHz random cycle operation even in the low-power process. 73-/spl mu/W data retention power is realized by using the PDDR mode, which is 5% of conventional schemes.