Nae-In Lee

A high-endurance low-temperature polysilicon thin-film transistor EEPROM cell

A planar type polysilicon thin-film transistor (poly-Si TFT) EEPROM cell with electron cyclotron resonance (ECR) N/sub 2/O-plasma oxide has been developed with a low temperature (/spl les/400/spl deg/C) process. The poly-Si TFT EEPROM cell has an initial threshold voltage shift of 4 V for programming and erasing voltages of 11 V and -11 V, respectively. Furthermore, the poly-Si TFT EEPROM cell maintains the threshold voltage shift of 4 V after 100 000 program/erase cycles. The excellent high endurance of the fabricated poly-Si TFT EEPROM cell is attributed to the ECR N/sub 2/O-plasma oxide with good charge-to-breakdown (Qbd) characteristics.

Improved stability of polysilicon thin-film transistors under self-heating and high endurance EEPROM cells for systems-on-panel

The stability of poly-Si TFTs on quartz with thin (12 nm) ECR N/sub 2/O-plasma gate oxide and high endurance poly-Si TFT EEPROMs are presented. The fabricated n-channel (p-channel) TFTs on quartz have mobilities of 262 (102) cm/sup 2//V/spl middot/s and subthreshold slopes of 72 (86) mV/dec. Although the TFTs on quartz exhibit self-heating effects, /spl Delta/V/sub T/ after stress is less than 0.2 V, which is remarkably excellent. The fabricated planar CMOS poly-Si TFT EEPROMs have excellent endurance characteristics of 10/sup 5/ program/erase cycles, which is attributed to the highly reliable ECR N/sub 2/O-plasma tunnel oxide. The degradation of stage delay of a ring-oscillator is also very small after stress.

Highly reliable polysilicon oxide grown by electron cyclotron resonance nitrous oxide plasma

Highly reliable inter-polysilicon oxide (polyoxide) for nonvolatile memory applications has been achieved using electron cyclotron resonance (ECR) N/sub 2/O-plasma. It is demonstrated that the N/sub 2/O-plasma polyoxide grown on doped poly-Si has a low leakage current and high breakdown field due to a smooth polyoxide/poly-Si interface and nitrogen incorporation during oxidation. Moreover, the polyoxide has much less electron trapping and over one order larger charge-to-breakdown (Q/sub bd/) up to 10 C/cm/sup 2/ than thermal polyoxide. The N/sub 2/O-plasma polyoxide can be a good choice for the interpoly dielectric of nonvolatile memories.

Oxidation of Silicon Using Electron Cyclotron Resonance Nitrous Oxide Plasma and Its Application to Polycrystalline Silicon Thin Film Transistors

Electron cyclotron resonance nitrous oxide (N 2 O) plasma oxidation has been investigated as a process to grow thin oxide on polycrystalline silicon and (100), (111), and (110) oriented crystalline silicon. In spite of a low thermal budget, N 2 O plasma oxidation incorporates nitrogen atoms at the silicon/silicon dioxide interface and forms a nitrogen-rich layer. The incorporated nitrogen atoms are tightly bound to silicon atoms at the interface with N (Is) electron energy of 397.8 eV. The oxidation rate in N 2 O plasma is less dependent on crystalline orientation in comparison with thermal O 2 , and is therefore nearly identical in poly- and single-crystalline-Si. Polysilicon oxide (polyoxide) grown by N 2 O plasma oxidation exhibits better electrical properties than thermally grown oxides; this is attributed to the smooth interface between the polyoxide and a poly-Si film. Polysilicon thin film transistors fabricated with N 2 O plasma oxide show improved performance, which is attributed not only to the smooth interface but also to oxygen- and nitrogen-plasma passivation.

Improved stability of short-channel hydrogenated N-channel polycrystalline silicon thin-film transistors with very thin ECR N 2 O-plasma gate oxide

Stability has been investigated for short-channel hydrogenated n-channel polycrystalline thin-film transistors (poly-Si TFTs) with very thin (12 nm) electron cyclotron resonance (ECR) N/sub 2/O-plasma gate oxide. The TFTs show negligible changes in the electrical characteristics after hot-carrier stresses, which is due to the highly reliable interface and gate oxide. The hydrogenated TFTs with 3-/spl mu/m gate length TFTs exhibit very small degradation (/spl Delta/V/sub th/<15 mV) under hot-carrier stresses and Fowler-Nordheim (F-N) stress (/spl Delta/V/sub th/=/sub 81/ mV, /spl Delta/Gm/Gm=2.2%, /spl Delta/S/S=4.7%).

A poly-Si thin-film transistor EEPROM cell with a folded floating gate

A new polysilicon thin-film transistor (poly-Si TFT) EEPROM with the folded floating gate structure has been proposed to suppress the field dependent leakage current at the programmed state. The control gate folds the floating gate and acts as a field plate to reduce the leakage current. As a result, the leakage current is maintained to the minimum level at an off-state control gate bias, irrespective of the programmed state, which is confirmed by simulation and experimental results. The fabricated poly-Si TFT EEPROM shows successful programming/erasing operation with a threshold voltage shift of 1 V after 5/spl times/10/sup 4/ program and erase cycles.

Stability of short-channel P-channel polysilicon thin-film transistors with ECR N 2 O-plasma gate oxide

Stability of hydrogenated short-channel (/spl les/3 /spl mu/m) p-channel poly-Si TFTs with very thin (12 nm) electron cyclotron resonance N/sub 2/O plasma gate oxide is investigated. The fabricated poly-Si TFTs with gate length not less than 2 /spl mu/m show excellent stability characteristics of less than 0.1 V in the threshold voltage shift and less than 3% in the percent change of transconductance after harsh electrical stresses. In a small |V/sub G/| stress, an effective shortening of channel length is observed due to trapping of hot-electrons and the minimum leakage current is decreased. However, a large |V/sub G/| stress causes more degradation on the subthreshold slope and minimum leakage current due to trapping of hot-holes.

Characteristics of polysilicon thin-film transistor with thin-gate dielectric grown by electron cyclotron resonance nitrous oxide plasma

Polysilicon thin-film transistors (poly-Si TFTs) with thin-gate oxide grown by electron cyclotron resonance (ECR) nitrous oxide (N/sub 2/O)-plasma oxidation is presented. ECR N/sub 2/O-plasma oxidation successfully incorporates nitrogen atoms at the SiO/sub 2//poly-Si interface, consequently forms a nitrogen-rich layer with Si/spl equiv/N bonds at a binding energy of 397.8 eV. ECR N/sub 2/O-plasma oxide grown on poly-Si films shows higher breakdown fields than thermal oxide. The fabricated poly-Si TFTs with N/sub 2/O-plasma oxide show better performance than those with ECR O/sub 2/-plasma oxide, which results not only from the smooth interface but also oxygen- and nitrogen-plasma passivation.

Suppressed short-channel effects and improved stability in polysilicon thin film transistors with very thin ECR N/sub 2/O-plasma gate oxide

Short-channel polysilicon thin film transistors with very thin (12 nm) electron cyclotron resonance N/sub 2/O-plasma gate oxide are investigated. Short-channel effects are drastically suppressed using ECR N/sub 2/O-plasma gate oxide. The fabricated n-channel TFTs exhibit a very small threshold voltage shift (<50 mV) and ON current change (<3%) after an electrical stress of 2/spl times/10/sup 4/ sec with Vgs=Vds=5 V.