Deok-Hyung Lee

Scaling of 32nm low power SRAM with high-K metal gate

This paper describes SRAM scaling for 32 nm low power bulk technology, enabled by high-K metal gate process, down to 0.149 mum2 and 0.124 mum2. SRAM access stability and write margin are significantly improved through a 50% Vt mismatch reduction, thanks to HK-MG Tinv scaling. Cell read current is increased by 70% over Poly-SiON process. Ultra dense cell process window is expanded with optimized contact process. A dual-ground write assist option can additionally enable ultra dense 0.124 mum2 cell to meet low power application requirements.

Manufacturable embedded CMOS 6T-SRAM technology with high-k gate dielectric device for system-on-chip applications

Manufacturable embedded CMOS 6T-SRAM with the HfO/sub 2/-Al/sub 2/O/sub 3/ dielectric for system-on-chip (SoC) applications is successfully demonstrated for the first time in the semiconductor industry. The possibility of the high-k gate dielectric in low power SoC applications is suggested. 0.11/spl mu/m NFET and PFET devices with thin high-k gate dielectric have 470 and 150/spl mu/A//spl mu/m at Ioff=0.1nA/um and Vdd=1.2V, respectively. Inversion thickness of NFET and PFET are 2.4nm and 2.7nm, respectively. Gate leakage current of the high-k is 1000 times lower than that of the oxynitride at the accumulation region. Static noise margin of 2.14/spl mu/m/sup 2/ 6T-SRAM bit cell is about 300mV at Vdd=1.2V. 6T-SRAM chip yield of the high-k is comparable to that of the oxynitride. The post nitridation after high-k film deposition is very important to the yield of the SRAM chips due to the suppression of the PFET boron penetration. Stand-by current of the SRAM chips with the high-k is shown to be a decreases of 60% compared with the oxynitride.

50nm gate length logic technology with 9-layer Cu interconnects for 90nm node SoC applications

A 90 nm generation logic technology with Cu/low-k interconnects is reported. 50 nm transistors are employed using gate oxide 1.3 nm in thickness and operating at 1.0 V. High speed transistors have drive currents of 870 /spl mu/A/pm and 360 /spl mu/A//spl mu/m for NMOS and PMOS respectively, while generic transistors have currents of 640 /spl mu/A//spl mu/m and 260 /spl mu/A//spl mu/m respectively. Low power process using high-k gate dielectrics and SOI process are also provided in this technology. The low-k SiOC material with 2.9 in the k value is used for 9 layers of dual damascene Cu/low-k interconnects. The effective k (k/sub eff/) value of interconnect is about 3.6. Fully working 6-T SRAM cell with an area of 1.1 /spl mu/m/sup 2/ and SNM value of 330 mV is obtained. For MIM capacitor, voltage coefficient of capacitance is less than 20 ppm/V.

Improved Cell Performance for sub-50 nm DRAM with Manufacturable Bulk FinFET Structure

FinFET, the milestone for sub-50 nm DRAM cell transistor has been successfully demonstrated by a unique fabricating method with novel concept. We obtained a core solution of front-end-of-line process and structure, focusing on short channel behavior, off-state leakage, and saturation current. We have developed the scheme that is able to suppress off-state leakage current below 1 fA/cell with p+ poly-Si gate. We have also examined mobility and parasitic engineering techniques to maximize the cell performance (DeltaIon > 48 %). In conclusion, we propose the effective guideline for highly manufacturable FinFET for DRAM application at the sub-50 nm node.

High performance device utilizing ultra-thick-strained-Si (UTSS) grown on relaxed SiGe

We demonstrate a highly manufacturable substrate-induced strained Si device, which is compatible with the conventional Si bulk process. It utilizes ultra-thick-strained Si (UTSS) layer thicker than 3000 /spl Aring/ and relaxed SiGe layer with low Ge content less than 10%. The UTSS n-MOSFET gives 6 /spl sim/ 12% increase in I/sub on/ according to the gate length without the cost of increase in I/sub off/. In addition, more than 5% increase in I/sub on/ for p-MOSFET can be obtained by hybrid stress of UTSS and SiGe source/drain process. We also emphasize the importance of the ratio of channel resistance (R/sub CH/) to source-drain resistance (R/sub SD/) for performance enhancement.

Front-end-of-line (FEOL) optimization for high-performance, high-reliable strained-Si MOSFETs; from virtual substrate to gate oxidation

Front-end-of-line (FEOL) process parameters including virtual substrate (Si/Si/sub 1-x/Ge/sub x/), shallow-trench-isolation (STI) process, and gate oxidation have strong effects on performance and reliability of strained-Si MOSFETs such as gate oxide integrity (GOI), threshold voltage (V/sub TH/ roll-off, reliability behavior including junction breakdown and device isolation characteristics. It is found that gate oxide integrity can be improved by 1 order of magnitude by applying low-temperature, plasma oxidation process as compared with thermal oxidation, junction leakage and device isolation characteristics can be improved by 1 order of magnitude and by two times, respectively, by using low-defect virtual substrate and further defect-curing process, and parameters related with STI process such as thin SiN layer and oxide densification temperature must be optimized both to reduce junction leakage current and to improve device performance such as Ion-Ioff characteristics.

Performance of DRAM Cell Transistor with Thermal Desorption Silicon Etching (TDSE) and Selective Si Channel Epi Techniques

This paper describes thermal desorption silicon etching (TDSE)/channel-epi transistor, which has improved the profile and the electrical characteristics of channel-epi transistor. Thermal desorption silicon etching (TDSE) process is introduced before Si channel-epi growth using ultrahigh vacuum system to improve transistor performance at dynamic random access memory (DRAM) device. TDSE process for etching active silicon was carried out using Cl2 gas at 700°C in UHV chamber. Following the TDSE process, in-situ Si channel-epi was grown at the same chamber. We evaluated the electrical characteristics of TDSE/channel-epi transistor, and also measured the reliability of gate oxide. Compared with the conventional channel-epi which shows the degradation of transistor characteristics due to the raised active profile, TDSE process with channel-epi presents superior transistor performance in terms of transistor hump characteristics and inverse narrow width effect (INWE). TDSE induced interface and junction leakages, however, are observed. To solve these problems, H2 added TDSE process or H2 anneal process after TDSE has been developed.

High performance cell technology featuring sub-100nm DRAM with multi-gigabit density

Fully metal embedded cell technologies, including poly-Si/W/sub x/N/W gate, Co salicide with elevated source/drain using UHV-selective epitaxial growth and CVD-W cell pad has been integrated successfully for the first time for 100 nm design rule DRAM devices. Each key technology exhibits excellent performance.