Byung-Il Ryu

Highly manufacturable high density phase change memory of 64Mb and beyond

Highly manufacturable 64Mbit PRAM has been successfully fabricated using N-doped Ge/sub 2/Sb/sub 2/Te/sub 5/ (GST) and optimal GST etching process. Using those technologies, it was possible to achieve the low writing current of 0.6 mA and clear separation between SET and RESET resistance distributions. The 64Mb PRAM was designed to support commercial NOR flash memory compatible interfaces. Therefore, the fabricated chip was tested under the mobile application platform and its functionality and reliability has been evaluated by operation temperature dependency, disturbance, endurance, and retention. Finally, it was clearly demonstrated that high density PRAM can be fabricated in the product level with strong reliability to produce new nonvolatile memory markets.

High performance 5nm radius Twin Silicon Nanowire MOSFET (TSNWFET) : fabrication on bulk si wafer, characteristics, and reliability

For the first time, we have successfully fabricated gate-all-around twin silicon nanowire transistor (TSNWFET) on bulk Si wafer using self-aligned damascene-gate process. With 10nm diameter nanowire, saturation currents through twin nanowires of 2.64 mA/mum, 1.11 mA/mum for n-channel TSNWFET and p-channel TSNWFET are obtained, respectively. No roll-off of threshold voltages, ~70 mV/dec. of substhreshold swing (SS), and ~20 mV/V of drain induced barrier lowering(DIBL) down to 30 nm gate length are observed for both n-ch and p-ch TSNWFETs

Highly scalable on-axis confined cell structure for high density PRAM beyond 256Mb

We firstly fabricated on-axis confined structure and evaluated based on 64Mb PRAM with 0.12/spl mu/m-CMOS technologies. Ge/sub 2/Sb/sub 2/Te /sub 5/ was confined within small pore, which resulted in low writing current of 0.4mA. The pore is on-axis with upper and lower contacts, which leads to good scalability of PRAM above 256Mb. The confined structure was relatively insensitive to small cell edge damage effect. The on-axis confined structure is a promising candidate for high density PRAM due to low writing current, good scalability, and insensitiveness to edge damage.

Gate-All-Around (GAA) Twin Silicon Nanowire MOSFET (TSNWFET) with 15 nm Length Gate and 4 nm Radius Nanowires

GAA TSNWFET with 15 nm gate length and 4 nm radius nanowires is demonstrated and shows excellent short channel immunity. p-TSNWFET shows high driving current of 1.94 mA/mum while n-TSNWFET shows on-current of 1.44 mA/mum. Merits of TSNWFET and performance enhancement of p-TSNWFET are explored using 3D and quantum simulation

Bit line coupling scheme and electrical fuse circuit for reliable operation of high density DRAM

Two design techniques are presented to improve the yield of high density DRAM product. One is bit line coupling (BLC) scheme and the other is electrical fuse (E-Fuse) circuit for reliable field programmable repair scheme. We obtain an improvement of 100 ms for the data retention time (tREF) using the BLC scheme. BLC scheme also improves the low VCC margin by 0.3 V and the RAS to CAS delay time (tRCD) by 1.5 ns. Differential current evaluation for the E-fuse implementation shows polysilicon fuse fail rate <10/sup -12/.

Floating Body DRAM Characteristics of Silicon-On-ONO (SOONO) Devices for System-on-Chip (SoC) Applications

We completed the demonstration of three key functions of SOONO devices by demonstrating the DRAM characteristics of FD and PD SOONO devices successfully, together with the previously reported logic transistor and flash memory characteristics. Floating body SOONO DRAM cells implemented on electrically thin buried insulator shows the large sensing margins more than 5muA in FD device with long data retention and nondestructive read even at the W/L of 60/55nm which is the smallest IT DRAM ever reported.

A novel multi-channel field effect transistor (McFET) on bulk Si for high performance sub-80nm application

We demonstrate highly manufacturable double FinFET on bulk Si wafer, named multi-channel field effect transistor (McFET) for the high performance 80nm 144M SRAM. Twin fins are formed for each transistor using our newly developed simple process scheme. McFET with L/sub G/=80nm shows several excellent transistor characteristics, such as /spl sim/5 times higher drive current than planar MOSFET, ideal subthreshold swing of 60mV/dec, drain induced barrier lowering (DIBL) of 15mV/V without pocket implantation, and negligible body bias dependency, maintaining the same source/drain resistance as planar transistor due to the unique feature of McFET.

8 Gb MLC (multi-level cell) NAND flash memory using 63 nm process technology

For the first time, 8 Gb multi-level cell (MLC) NAND flash memory with 63 nm design rule is developed for mass storage applications. Its unit cell size is 0.0164 /spl mu/m/sup 2/, the smallest ever reported. ArF lithography with off-axis illumination (OAI) was employed for critical layers. In addition, self-aligned floating poly-silicon gate (SAP), tungsten gate with an optimized re-oxidation process, oxide spacer and tungsten bit-line (BL) with low resistance were implemented.

Highly Scalable Phase Change Memory with CVD GeSbTe for Sub 50nm Generation

first present a PRAM with confinement of chemically vapor deposited GeSbTe (CVD GST) within high aspect ratio 50 nm contact for sub 50 nm generation PRAMs. By adopting confined GST, we were able to reduce the reset current below ~260 muA and thermally stable CVD Ge2Sb2Te5 compound having hexagonal phase was uniformly filled in a contact while maintaining constant composition along with 150 nm depth. Our results indicate that the confined cell structure of 50 nm contact is applicable to PRAM device below 50 nm design rule due to small GST size based on small contact and direct top electrode contact, reduced reset current, minimized etch damage, and low thermal disturbance effect.

High-density low-power-operating DRAM device adopting 6F/sup 2/ cell scheme with novel S-RCAT structure on 80nm feature size and beyond

For the first time, the DRAM device composed of 6F/sup 2/ open-bit-line memory cell with 80nm feature size is developed. Adopting 6F/sup 2/ scheme instead of customary 8F/sup 2/ scheme made it possible to reduce chip size by up to nearly 20%. However, converting the cell scheme to 6F/sup 2/ accompanies some difficulties such as decrease of the cell capacitance, and more compact core layout. To overcome this strict obstacles which are originally stemming from the conversion of cell scheme to 6F/sup 2/, TIT structure with AHO (AfO/AlO/AfO) is adopted for higher cell capacitance, and bar-type contact is adopted for adjusting to compact core layout. Moreover, to lower cell V/sub th/ so far as suitable for characteristic of low power operation, the novel concept, S-RCAT (sphere-shaped-recess-channel-array transistor) is introduced. It is the improved scheme of RCAT used in 8F/sup 2/ scheme. By adopting S-RCAT, V/sub th/ can be lowered, SW, DIBL are improved. Additionally, data retention time characteristic can be improved.