Ming-Fu Tsai

Metalorganic chemical vapor deposition of tantalum nitride by tertbutylimidotris(diethylamido)tantalum for advanced metallization

We deposited tantalum nitride (TaN) films by low‐pressure metalorganic chemical vapor deposition (LP‐MOCVD) using a new precursor tertbutylimidotris(diethylamido)tantalum (TBTDET). Strong Ta–N double bond in the precursor preserved the ‘‘TaN’’ portion during the pyrolysis process. This method has yielded low‐resistivity films. It changed from 10 mΩ cm (deposited at 500 °C) to 920 μΩ cm (obtained at 650 °C). The carbon and oxygen concentrations were low in the films deposited at 600 °C, as determined by x‐ray photoelectron spectroscopy. Transmission electron microscopy and x‐ray diffraction analysis indicated that the as‐deposited films exhibited polycrystalline structures with the lattice constants close to the bulk TaN value. The TaN barrier layer was successfully applied as a glue layer for CVD tungsten (W) metallization schemes.

Metalorganic chemical vapor deposition of tungsten nitride for advanced metallization

In this study, the physical and electrical properties of tungsten nitride thin films deposited by thermal decomposition of bis(tertbutylimido)bis(tertbutylamido)tungsten have been investigated. The films have an excellent step coverage over high aspect‐ratio contact holes as well as a low carbon concentration. Strong W–N double bonds in the precursor preserved the nitrogen atoms during the pyrolysis process. This method subsequently yielded low‐resistivity films. A decrease in film resistivity from 4300 to 620 μΩ cm corresponded to an increase in the deposition temperature from 500 to 650 °C. X‐ray diffraction (XRD) and wavelength dispersive spectroscopy (WDS) results indicated that the as‐deposited films have face centered cubic (fcc) phase polycrystalline structures with excessive nitrogen atoms.

A voltage‐tunable multicolor triple‐coupled InGaAs/GaAs/AlGaAs quantum‐well infrared photodetector for 8–12 μm detection

A voltage‐tunable multicolor triple‐coupled quantum‐well infrared photodetector (TC‐QWIP) has been developed for 8–12 μm detection. The TC‐QWIP consists of three coupled quantum wells formed by an enlarged Si‐doped InxGa1−xAs quantum well and two undoped GaAs quantum wells separated by two thin AlyGa1−yAs barriers. Two TC‐QWIP structures with varying indium and aluminum compositions were designed and demonstrated. Due to the strong coupling effect of the asymmetrical quantum wells, three bound states (E1, E2, E3) are formed inside the quantum wells of the TC‐QWIP. The main detection peak wavelength is due to E1→E3 bound states transition for both devices, while two secondary detection peaks due to E1→E2 and E1→Ec continuum states transitions under different biases were also observed. In addition, a strong quantum‐confined Stark shift effect for the E1→E3 transition was observed in the wavelength range of 8.2–9.1 and 10.8–11.5 μm for QWIP‐A and QWIP‐B, respectively; both devices exhibit a linear dependence...

Metal-organic chemical vapor deposition of tantalum nitride barrier layers for ULSI applications

Abstract Low-resistivity tantalum nitride (TaN) films were deposited by low-pressure metal-organic chemical vapor deposition (MOCVD) using a new precursor tertbutylimidotrisdiethylamidotantalum. The surface morphology and the step coverage of TaN films were characterized by scanning electron microscopy. The film deposited at 450 °C had nearly 100% step coverage and the step coverage decreased to 25% for the films deposited at 650 °C. The carbon and oxygen concentrations are about 10 at.% in the CVD TaN films, as determined by Auger electron spectroscopy. From Rutherford backscattering spectroscopy and secondary ion mass spectroscopy analysis, TaN films were found to be effective diffusion barriers between aluminum and silicon up to 550 °C. The electrical measurements of diode-leakage current indicate that the Al/TaN Si structure remained stable up to 500 °C, after which Al started to diffuse through the TaN layer and resulted in a higher leakage current.

Performance of MOCVD tantalum nitride diffusion barrier for copper metallization

A low-resistivity and low carbon concentration CVD TaN film has been realized by using a new precursor terbutylimido-tris-diethylamido tantalum (TBTDET). Results show that CVD TaN as a diffusion barrier for Cu has higher thermal stability up to 500/spl deg/C than CVD TiN of 450/spl deg/C.

EFFECT OF RAPID THERMAL ANNEALING ON THE ELECTRICAL AND PHYSICAL PROPERTIES OF METALORGANIC CHEMICAL-VAPOR-DEPOSITED TIN

This work reports on the effect of postdeposition thermal treatment using rapid thermal annealing on the physical and electrical properties of metalorganic chemical‐vapor‐deposited (MOCVD) titanium nitride (TiN) thin films. When ammonia is used as the annealing ambient, the resistivity decreases with increasing annealing temperature. The resistivity of MOCVD TiN was reduced from 6000 to 320 μΩ cm after 800 °C rapid thermal annealing in ammonia (RTN). Annealing in nitrogen ambient was found to be not nearly as effective as that in ammonia. The decrease in resistivity may be attributed to a reduction in the carbon and oxygen content, growth in grain size through polycrystalline recrystallization, as well as to an increase in film density.

A comparative analysis of tunneling FET circuit switching characteristics and SRAM stability and performance

With steep sub-threshold slope, tunneling FETs (TFETs) are promising candidates for ultra-low voltage operation, achieving low leakage current and superior performance compared with the conventional MOSFETs. However, the broad soft transition region in the Id-Vgs characteristics, where Id increases slowly to reach saturation following the steep slope region, results in large crossover region/current in an inverter, thus degrading the Hold/Read Static Noise Margin (H/RSNM) of TFET SRAMs. The Write-ability and Write Static Noise Margin (WSNM) of TFET SRAMs are constrained by the uni-directional conduction characteristics caused by the asymmetric source-drain structure and large cross-over contention of the Write access transistor and the holding transistor. In this paper, we present a detailed analysis of TFET circuit switching characteristics/performance and compare the stability/performance of several TFET SRAM cells using atomistic TCAD mixed-mode simulations. A robust 7T Driver-Less (DL) TFET SRAM cell is proposed. The proposed 7T DL TFET SRAM cell, with decoupled Read current path from cell storage node and push-pull Write action with asymmetrical raised-cell-virtual-ground Write-assist, provides significant improvement in Read/Write stability and performance.

Variation tolerant CLSAs for nanoscale Bulk-CMOS and FinFET SRAM

In this paper, we propose three Current-Latch-based Sense Amplifiers (CLSA) configurations for nanoscale Bulk-CMOS SRAM and several CLSAs using FinFET devices with independently-controlled-gate. Extensive simulations suggest the proposed structures are robust against random offset errors. The proposed CLSA structures feature significant offset suppression capabilities with σoffset reduction up to 74% (76%) in 40nm Bulk-CMOS (25nm FinFET-SOI) technology compared with the conventional CLSA. Meanwhile, up to 27% (52%) shorter sensing delay, 71% (77%) shorter Time-To-Sense and 73% (76%) lower bit-line power consumption are achieved in 40nm Bulk-CMOS (25nm FinFET-SOI). Finally, the proposed CLSA structures significantly enhance the sensing yield and affordable number of cells per bit-line, thus improving the array efficiency hence overall area and performance/power as well.

A new CVD tungsten nitride diffusion barrier for Cu interconnection

This paper reports the investigation of a newly developed WNx film by metalorganic chemical vapor deposition (MOCVD). The WNx material provided an excellent diffusion barrier for Cu metallization.

Impacts of random telegraph noise on the analog properties of FinFET and trigate devices and Widlar current source

We investigate the impacts of the single charged trap induced Random Telegraph Noise (RTN) on the analog properties of FinFET and Trigate devices. A comprehensive comparative analysis between FinFET and Trigate device is carried out for the trap located along the channel length and fin height direction employing 3D atomistic TCAD simulations, and the resulting impacts on g_m, r_o, f_T and Wildar current source examined. The results indicate that Trigate device, with larger (smaller) fraction of electron current flowing near the bottom (top) region of the fin, suffers larger (smaller) RTN degradation when the trap is located at the bottom (top) region of the fin. As such, the RTN amplitude in Trigate device has broader dispersion and stronger dependence on the location of the trap compared with FinFET device. For trap positioned along the channel length direction, the single trap located near the source region has the largest influence on the output resistance (Δ_ro/r_o) when the device operates at saturation region (V_D= 1V), because the sensitivity of ID to ΔV_D becomes higher as the potential barrier for carrier injection near the source is significantly perturbed. The variability of RTN Δg_m/g_m under fin Line Edge Roughness (LER) and Work Function Variation (WFV) is examined, and Trigate device is shown to exhibit larger nominal Δg_m/g_m and larger s(Δg_m/g_m). The Widlar current source is used as an example to illustrate the impacts of RTN on analog circuit. The combinations of trapping/detrapping in the current source device and mirroring/output device, and the dependence of ΔI_out/I_out on their VGS difference are examined. The Trigate device exhibits larger ΔI_out/I_out and larger s(ΔI_out/I_out), and the difference between Trigate and FinFET becomes more significant with decreasing gate over-drive.