Properties of Si/sub 3/N/sub 4//Si/sub x/Ge/sub 1-x/ metal-insulator-semiconductor capacitors

The density of fast interface states was studied in Si/sub 3/N/sub 4//Si/sub 0.8/Ge/sub 0.2/ metal-insulator-semiconductor (MIS) capacitors. The interface state density does not appear to be strongly affected by the presence of a thin Si interlayer between the nitride and SiGe alloy. This is in contrast to the results when SiO/sub 2/ is used as the insulator material in similar structures.<>     

RF, DC, and reliability characteristics of ALD HfO/sub 2/-Al/sub 2/O/sub 3/ laminate MIM capacitors for Si RF IC applications

High-performance metal-insulator-metal capacitors using atomic layer-deposited HfO/sub 2/-Al/sub 2/O/sub 3/ laminate are fabricated and characterized for RF and mixed-signal applications. The laminate capacitor can offer high capacitance density (12.8 fF//spl mu/m/sup 2/) up to 20 GHz, low leakage current of 4.9/spl times/10/sup -8/ A/cm/sup 2/ at 2 V and 125/spl deg/C, and small linear voltage coefficient of capacitance of 211 ppm/V at 1 MHz, which can easily satisfy RF capacitor requirements for year 2007 according to the International Technology Roadmap for Semiconductors. In addition, effects of constant voltage stress and temperature on leakage current and voltage linearity are comprehensively investigated, and dependences of quadratic voltage coefficient of capacitance (/spl alpha/) on frequency and thickness are also demonstrated. Meanwhile, the underlying mechanisms are also discussed.     

Lanthanide (Tb)-doped HfO/sub 2/ for high-density MIM capacitors

A high-density metal-insulator-metal (MIM) capacitor with a lanthanide-doped HfO/sub 2/ dielectric prepared by physical vapor deposition (PVD) is presented for the first time. A significant improvement was shown in both the voltage coefficient of capacitance (VCC) and the leakage current density of MIM capacitor, yet the high capacitance density of HfO/sub 2/ dielectrics was maintained by achieving the doping of Tb with an optimum concentration in HfO/sub 2/. This technique allows utilizing thinner dielectric film in MIM capacitors and achieving a capacitance density as high as 13.3 fF//spl mu/m/sup 2/ with leakage current and VCC values that fully meet requirements from year 2005 for radio frequency (RF) bypass capacitors applications.     

Evidence and understanding of ALD HfO/sub 2/-Al/sub 2/O/sub 3/ laminate MIM capacitors outperforming sandwich counterparts

Metal-insulator-metal capacitors with atomic-layer-deposited HfO/sub 2/-Al/sub 2/O/sub 3/ laminated and sandwiched dielectrics have been compared, for the first time, for analog circuit applications. The experimental results indicate that significant improvements can be obtained using the laminated dielectrics, including an extremely low leakage current of 1/spl times/10/sup -9/ A/cm/sup 2/ at 3.3V and 125/spl deg/C, a high breakdown electric field of /spl sim/3.3MV/cm at 125/spl deg/C, good polarity-independent electrical characteristics, while retaining relatively high capacitance density of 3.13 fF//spl mu/m/sup 2/ as well as voltage coefficients of capacitance as low as -80 ppm/V and 100 ppm/V/sup 2/ at 100 kHz. The underlying mechanism is likely due to alternate insertions of Al/sub 2/O/sub 3/ layers that reduce the thickness of each HfO/sub 2/ layer, hereby efficiently inhibiting HfO/sub 2/ crystallization, and blocking extensions of grain boundary channels from top to bottom as well as to achieve good interfacial quality.     

MIM capacitors using atomic-layer-deposited high-/spl kappa/ (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ dielectrics

Metal-insulator-metal (MIM) capacitors with (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ high-/spl kappa/ dielectric films were investigated for the first time. The results show that both the capacitance density and voltage/temperature coefficients of capacitance (VCC/TCC) values decrease with increasing Al/sub 2/O/sub 3/ mole fraction. It was demonstrated that the (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ MIM capacitor with an Al/sub 2/O/sub 3/ mole fraction of 0.14 is optimized. It provides a high capacitance density (3.5 fF//spl mu/m/sup 2/) and low VCC values (/spl sim/140 ppm/V/sup 2/) at the same time. In addition, small frequency dependence, low loss tangent, and low leakage current are obtained. Also, no electrical degradation was observed for (HfO/sub 2/)/sub 1-x/(Al/sub 2/O/sub 3/)/sub x/ MIM capacitors after N/sub 2/ annealing at 400/spl deg/C. These results show that the (HfO/sub 2/)/sub 0.86/(Al/sub 2/O/sub 3/)/sub 0.14/ MIM capacitor is very suitable for capacitor applications within the thermal budget of the back end of line process.     

Polarisation-insensitive Si/sub 3/N/sub 4/ strip-loaded BaTiO/sub 3/ thin-film waveguide with low propagation losses

A low-loss and polarisation-insensitive singlemode BaTiO/sub 3/ thin-film waveguide is reported. Polarisation-dependent loss as low as 0.1 dB/cm at a wavelength of 1.55 /spl mu/m has been achieved by a novel Si/sub 3/N/sub 4/ strip-loaded BaTiO/sub 3/ waveguide structure. Propagation loss of less than 0.9 dB/cm for both TE and TM polarisations was measured     

Electrical and reliability characteristics of an ultrathin TaO/sub x/N/sub y/ gate dielectric prepared by ND/sub 3/ annealing of Ta/sub 2/O/sub 5/

This letter describes a unique process for the preparation of high quality tantalum oxynitride (TaO/sub x/N/sub y/) via the ND/sub 3/ annealing of Ta/sub 2/O/sub 5/, for use in gate dielectric applications. Compared with tantalum oxide (Ta/sub 2/O/sub 5/), a significant improvement in the dielectric constant was obtained by the ammonia treatment followed by light reoxidation in a wet ambient. We were able to confirm nitrogen incorporation in the tantalum oxynitride (TaO/sub x/N/sub y/) by Auger electron spectroscopy. Compared with NH/sub 3/ nitridation, tantalum oxynitride prepared by nitridation in ND/sub 3/ shows less charge trapping and larger charge-to-breakdown characteristics.     

Submicron gate Si/sub 3/N/sub 4//AlGaN/GaN-metal-insulator-semiconductor heterostructure field-effect transistors

We present the characteristics of a quarter-micron gate metal-insulator-semiconductor heterostructure field-effect transistor (MISHFET) with Si/sub 3/N/sub 4/ film as a gate insulator. A detailed comparison of the MISHFET and an identical geometry HFET shows them to have the same radio frequency (RF) power gain and cut-off frequency, while the MISHFET has much lower gate-leakage currents and higher RF powers at operating frequencies as high as 26 GHz. The MISHFET gate-leakage currents are well below 100 pA at gate bias values from -10 V to +8 V. At zero gate bias, the drain saturation current is about 0.9 A/mm and it increases to 1.2 A/mm at +8 V gate bias. The output RF power of around 6 W/mm at 40 drain bias was found to be frequency independent in the range of 2 to 26 GHz. This power is 3 dB higher than that from HFET of the same geometry. The intrinsic cutoff frequency is /spl sim/63 GHz for both the HFET and the MISHFET. This corresponds to an average effective electron velocity in the MISHFET channel of 9.9/spl times/10/sup 6/ cm/s. The knee voltage and current saturation mechanisms in submicron MISHFETs and heterostructure field-effect transistors (HFET) are also discussed.     

Ultrathin stacked Si/sub 3/N/sub 4//SiO/sub 2/ gate dielectrics prepared by rapid thermal processing

Ultrathin (58 AA equivalent oxide thickness) stacked Si/sub 3/N/sub 4//SiO/sub 2/ (NO) films with the bottom oxide prepared by rapid thermal oxidation (RTO) in O/sub 2/ and the top nitride deposited by rapid thermal processing chemical vapour deposition (RP-CVD) were fabricated and studied. Results show that the charge trapping and leakage current of the stacked films are comparable to those of pure SiO/sub 2/ and low-field breakdown events are significantly reduced. By scaling down the top nitride thickness the commonly observed flat-band voltage instability of MNOS devices was minimised, but the low-defect property was still preserved.<>     

Fabrication and characterization of high-quality uniform and apodized Si/sub 3/N/sub 4/ waveguide gratings using laser interference lithography

A method is presented for fabricating high-quality ridge waveguide gratings by combining conventional mask lithography with laser interference lithography. The method, which allows for apodization functions modulating both amplitude and phase of the grating is demonstrated by fabricating a grating that is chirped by width-variation of the grated ridge waveguide. The structure was optically characterized using both an end-fire and an infrared camera setup to measure the transmission and to map and quantify the power scattered out of the grating, respectively. For a uniform grating, we found a Q value of /spl sim/8000 for the resonance peak near the lower wavelength band edge, which was almost completely suppressed after apodization.     

Comparison among various Si/sub 3/N/sub 4/ waveguide geometries grown within a CMOS fabrication pilot line

Low-pressure chemical-vapor deposition (LPCVD) thin-film Si/sub 3/N/sub 4/ waveguides have been fabricated on Si substrate within a complementary metal-oxide-semiconductor (CMOS) fabrication pilot line. Three kinds of geometries (channel, rib, and strip-loaded) have been simulated, fabricated, and optically characterized in order to optimize waveguide performances. The number and optical confinement factors of guided optical modes have been simulated, taking into account sidewall effects caused by the etching processes, which have been studied by scanning electron microscopy. Optical guided modes have been observed with a mode analyzer and compared with simulation expectations to confirm the process parameters. Propagation loss measurements at 780 and 632.8 nm have been performed by both using the cutback technique and measuring the drop of intensity of the top scattered light along the length of the waveguide. Loss coefficients of approximately 0.1 dB/cm have been obtained for channel waveguides. These data are very promising in view of the development of Si-integrated photonics.     

GaAs MMIC的MIM电容Si3N4介质的TDDB评价

运用TDDB理论,研究分析了G aA s MM IC的M IM氮化硅电容的导电特性和击穿特性,设计制作了三种对比分析的G aA s MM IC的M IM氮化硅电容结构,通过不同斜率的斜坡电压对氮化硅介质进行了可靠性评价,S i3N4M IM电容的可靠性与其面积和周长密切相关,介质缺陷是导致电容失效的主要因素。通过不同斜率的斜坡电压获得电场加速因子(γ)预计了10 V工作电压下的S i3N4介质层的寿命。     

Improvement of voltage linearity in high-/spl kappa/ MIM capacitors using HfO/sub 2/-SiO/sub 2/ stacked dielectric

It is demonstrated that the voltage coefficients of capacitance (VCC) in high-/spl kappa/ metal-insulator-metal (MIM) capacitors can be actively engineered and voltage linearity can be significantly improved maintaining high capacitance density, by using a stacked insulator structure of high-/spl kappa/ and SiO/sub 2/ dielectrics. A MIM capacitor with capacitance density of 6 fF/spl mu/m/sup 2/ and quadratic VCC of only 14 ppm/V/sup 2/ has been demonstrated together with excellent frequency and temperature dependence (temperature coefficients of capacitance of 54 ppm /spl deg/C) as well as low leakage current of less than 10 nA/cm/sup 2/ up to 4 V at 125 /spl deg/C.     

Spectroscopic and stimulated emission characteristics of Nd/sup 3+/ in transparent Y/sub 2/O/sub 3/ ceramics

Nd:Y/sub 2/O/sub 3/ ceramic materials have been synthesized using the vacuum sintering technique with the raw materials prepared by the nanocrystalline methods. The TEM measurements reveal the excellent optical quality of the ceramic with low pore volume and narrow grain boundary. The radiative spectral properties of Nd:Y/sub 2/O/sub 3/ ceramic have been evaluated by fitting the Judd-Ofelt model with the absorption and emission data. Individual Stark levels for /sup 2s+1/L/sub J/ manifolds are obtained from the absorption and fluorescence spectra and are analyzed to identify the stimulated emission channels possible in the Nd:Y/sub 2/O/sub 3/ ceramic. Laser performance studies reveal two stimulated emission channels at 1074.6- and 1078.6-nm wavelengths with stimulated emission cross sections of 7.63/spl times/10/sup -20/ and 6.35/spl times/10/sup -20/ cm/sup 2/. With 1.5 at % Nd:Y/sub 2/O/sub 3/ ceramic acting as a laser medium, we obtained a slope efficiency of 32% with 160-mW output power and pump threshold of 200 mW at 1078.6 nm.     

Electrical characteristics and reliability properties of metal-oxide-semiconductor capacitors with HfZrLaO gate dielectrics

Metal-oxide-semiconductor (MOS) capacitors incorporating atomic-layer-deposition (ALD) HfZrLaO high-κ gate dielectric were fabricated and investigated. The equivalent oxide thickness (EOT) is 0.68 nm and the gate leakage current density (J_g) is only 9.3 × 10⁻¹ A/cm². The time-dependence dielectric breakdown (TDDB) behavior agrees with the percolation model, and the TDDB characteristics are consistent with the thermochemical E-model for lifetime projection. The experimental results show that the Weibull slopes are almost independent of capacitor area and stress conditions. The field acceleration parameter (γ) and activation energy (ΔH₀) are determined around 5.9-7.0 cm/MV and 0.54-0.60 eV, respectively. At 85 °C, the maximum voltage projected for 10-years TDDB lifetime is 1.87 V.     

Electrical characterisation and reliability of HfO2 and Al2O3–HfO2 MIM capacitors

Current leakage and breakdown of MIM capacitors using HfO₂ and Al₂O₃–HfO₂ stacked layers were studied. Conduction in devices based upon HfO₂ layers thinner than 8 nm is probably dominated by tunnelling. Al₂O₃–HfO₂ stacked layers provide a limited benefit only in term of breakdown field. Constant-voltage wear-out of samples using insulating layer thicker than 6 nm is dominated by a very fast increase of the leakage current. A two step mechanism involving the generation of a conduction path followed by a destructive thermal effect is proposed to explain breakdown mechanism.     

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.     

Structural, electrical and optical properties of GZO/HfO2/GZO transparent MIM capacitors

Metal–insulator–metal (MIM) transparent capacitors were prepared by pulsed laser deposition (PLD) on glass substrates. The effect of the thickness of the dielectric layer and oxygen pressure on structural, electrical, and optical properties of these capacitors was investigated. Experimental results show that film thickness and oxygen pressure have no effect on the structural properties. It is also found that the optical properties of the HfO₂ thin films depend strongly on both the film thickness and oxygen pressure. The electrical properties of transparent capacitors were investigated at various thickness of the dielectric layer. The capacitor shows an overall high performance, such as a high dielectric constant of 28 and a low leakage current of 2.03×10⁻⁶ A/cm² at ±5 V. Transmittance above 70% was observed in visible region.     

La/sub 2/O/sub 3//Si/sub 0.3/Ge/sub 0.7/ p-MOSFETs with high hole mobility and good device characteristics

We have studied high-k La/sub 2/O/sub 3/ p-MOSFETs on Si/sub 0.3/Ge/sub 0.7/ substrate. Nearly identical gate oxide current, capacitance density, and time-dependent dielectric breakdown (TDDB) are obtained for La/sub 2/O/sub 3//Si and La/sub 2/O/sub 3//Si/sub 0.3/Ge/sub 0.7/ devices, indicating excellent Si/sub 0.3/Ge/sub 0.7/ quality without any side effects. The measured hole mobility in nitrided La/sub 2/O/sub 3//Si p-MOSFETs is 31 cm/sup 2//V-s and comparable with published data in nitrided HfO/sub 2//Si p-MOSFETs. In sharp contrast, a higher mobility of 55 cm/sup 2//V-s is measured in La/sub 2/O/sub 3//Si/sub 0.3/Ge/sub 0.7/ p-MOSFET, an improvement by 1.8 times compared with La/sub 2/O/sub 3//Si control devices. The high mobility in Si/sub 0.3/Ge/sub 0.7/ p-MOSFETs gives another step for integrating high-k gate dielectrics into the VLSI process.     

超薄Si3N4/SiO2（N/O）stack栅介质及器件

成功制备了EOT(equivalent oxide thickness)为2.1nm的Si3N4/SiO2(N/O) stack栅介质,并对其性质进行了研究．结果表明，同样EOT的Si3N4/SiO2 stack栅介质和纯SiO2栅介质比较，前者在栅隧穿漏电流、抗SILC性能、栅介质寿命等方面都远优于后者．在此基础上,采用Si3N4/SiO2 stack栅介质制备出性能优良的栅长为0.12μｍ的CMOS器件，器件很好地抑制了短沟道效应．在Vds=Vgs=±1.5V下，nMOSFET和pMOSFET对应的饱和电流Ion分别为584.3μA/μｍ和－281.3μA/μｍ，对应Ioff分别是8.3nA/μｍ和－1.3nA/μｍ．