High-performance MIM capacitor using ALD high-k HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectrics

For the first time, we successfully fabricated and demonstrated high performance metal-insulator-metal (MIM) capacitors with HfO/sub 2/-Al/sub 2/O/sub 3/ laminate dielectric using atomic layer deposition (ALD) technique. Our data indicates that the laminate MIM capacitor can provide high capacitance density of 12.8 fF//spl mu/m/sup 2/ from 10 kHz up to 20 GHz, very low leakage current of 3.2 /spl times/ 10/sup -8/ A/cm/sup 2/ at 3.3 V, small linear voltage coefficient of capacitance of 240 ppm/V together with quadratic one of 1830 ppm/V/sup 2/, temperature coefficient of capacitance of 182 ppm//spl deg/C, and high breakdown field of /spl sim/6 MV/cm as well as promising reliability. As a result, the HfO/sub 2/-Al/sub 2/O/sub 3/ laminate is a very promising candidate for next generation MIM capacitor for radio frequency and mixed signal integrated circuit applications.     

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.     

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.     

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.     

High-density MIM capacitors using AlTaO/sub x/ dielectrics

The authors have obtained good MIM capacitor integrity of high-capacitance density of 10 fF//spl mu/m/sup 2/ using high-/spl kappa/ AlTaO/sub x/ fabricated at 400/spl deg/C. In addition, small voltage dependence of capacitance of <600 ppm (quadratic voltage coefficient of only 130 ppm/V/sup 2/) is obtained at 1 GHz using their mathematical derivation from measured high-frequency S parameters. These good results ensure the high-/spl kappa/ AlTaO/sub x/ MIM capacitor technology is useful for high-precision circuits operated at the RF frequency regime.     

Integrated high-/spl kappa/ (/spl kappa/ /spl sim/19) MIM capacitor with Cu/low-/spl kappa/ interconnects for RF application

We demonstrate a high-performance metal-high /spl kappa/ insulator-metal (MIM) capacitor integrated with a Cu/low-/spl kappa/ backend interconnection. The high-/spl kappa/ used was laminated HfO/sub 2/-Al/sub 2/O/sub 3/ with effective /spl kappa/ /spl sim/19 and the low-/spl kappa/ dielectric used was Black Diamond with /spl kappa/ /spl sim/2.9. The MIM capacitor (/spl sim/13.4 fF//spl mu/m/sup 2/) achieved a Q-factor /spl sim/53 at 2.5 GHz and 11.7 pF. The resonant frequency f/sub r/ was 21% higher in comparison to an equivalently integrated Si/sub 3/N/sub 4/-MIM capacitor (/spl sim/0.93 fF//spl mu/m/sup 2/) having similar capacitance 11.2 pF. The impacts of high-/spl kappa/ insulator and low-/spl kappa/ interconnect dielectric on the mechanism for resonant frequency improvement are distinguished using equivalent circuit analysis. This letter suggests that integrated high-/spl kappa/ MIM could be a promising alternative capacitor structure for future high-performance RF applications.     

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.     

A high-density MIM capacitor (13 fF//spl mu/m/sup 2/) using ALD HfO/sub 2/ dielectrics

Metal-insulator-metal (MIM) capacitors with different HfO/sub 2/ thickness have been investigated. The results show that both the capacitance density and voltage coefficients of capacitance (VCCs) increase with decreasing HfO/sub 2/ thickness. In addition, it is found that the VCCs decrease logarithmically with increasing thickness. Furthermore, the MIM capacitor with 10-nm HfO/sub 2/ shows a record high capacitance density of 13 fF//spl mu/m/sup 2/ and a VCC of 607 ppm/V, which can meet the requirement of the International Technology Roadmap for Semiconductors. It can also provide a low leakage current of 5.95 /spl times/ 10/sup -8/A/cm/sup 2/ at room temperature at 1 V, low tangent values below 0.05, and a small frequency dependence. These results indicate that the devices are suitable for use in silicon integrated circuit applications.     

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.     

DRAM plate electrode bias optimization for reducing leakage current in UV-O/sub 3/ and O/sub 2/ annealed CVD deposited Ta/sub 2/O/sub 5/ dielectric films

A new plate biasing scheme is described which allowed the use of 65% higher supply voltage without increasing the leakage current for the UV-O/sub 3/ and O/sub 2/ annealed chemical-vapor-deposited tantalum pentaoxide dielectric film capacitors in stacked DRAM cells. Dielectric leakage was reduced by biasing the capacitor plate electrode to a voltage lower than the conventionally used value of V/sub cc//2. Ta/sub 2/O/sub 5/ films with 3.9 nm effective gate oxide, 8.5 fF//spl mu/m/sup 2/ capacitance and <0.3 /spl mu/A/cm/sup 2/ leakage at 100/spl deg/C and 3.3 V supply are demonstrated.<>     

A Two-Stage Monolithic IF Amplifier Utilizing a Ta/sub 2/O/sub 5/ Capacitor

A two-stage monolithic IF amplifier incorporating a sputtered Ta/sub 2/O/sub 5/ capacitor has been fabricated. The monolithic capacitor is based on a composite layer structure consisting of Au, Ta, Ta/sub 2/O/sub 5/, Ta, and Au. This layered structure is sequentially deposited in a single sputtering run, which eliminates particulate contamination. As a result, a thin pinhole-free dielectric layer can be deposited over large areas, and 140-pF capacitors have been fabricated with excellent yields. The large unit area capacitance of 1500 pF/mm/sup 2/ available with the present process has the potential for reducing the size of matching and bias circuits in microwave monolithic circuits and hybrid thin-film circuits. The monolithic amplifiers exhibit a gain of 17.5 +- 1.0 dB from 1.2 to 2.6 GHz and a minimum noise figure of ~2.7 dB, with an associated gain of 17.5 dB at 1.7 GHz.     

A novel high-/spl kappa/ SONOS memory using TaN/Al/sub 2/O/sub 3//Ta/sub 2/O/sub 5//HfO/sub 2//Si structure for fast speed and long retention operation

A novel high-/spl kappa/ silicon-oxide-nitride-oxide-silicon (SONOS)-type memory using TaN/Al/sub 2/O/sub 3//Ta/sub 2/O/sub 5//HfO/sub 2//Si (MATHS) structure is reported for the first time. Such MATHS devices can keep the advantages of our previously reported TaN/HfO/sub 2//Ta/sub 2/O/sub 5//HfO/sub 2//Si device structure to obtain a better tradeoff between long retention and fast programming as compared to traditional SONOS devices. While at the same time by replacing hafnium oxide (HfO/sub 2/) with aluminum oxide (Al/sub 2/O/sub 3/) for the top blocking layer, better blocking efficiency can be achieved due to Al/sub 2/O/sub 3/'s much larger barrier height, resulting in greatly improved memory window and faster programming. The fabricated devices exhibit a fast program and erase speed, excellent ten-year retention and superior endurance up to 10/sup 5/ stress cycles at a tunnel oxide of only 9.5 /spl Aring/ equivalent oxide thickness.     

RFIC TaN/SrTiO$_3/$TaN MIM Capacitors With 35fF$/muhboxm^2$Capacitance Density

A very high density of 35$hboxfF/muhboxm^2$is measured in a radio frequency (RF) metal-insulator-metal (MIM) capacitor using high-$kappa (kappa=hbox169)$$hboxSrTiO_3$fabricated by very large scale integration (VLSI) back-end integration. A very small capacitance reduction of 4.1% from 100kHz to 10GHz, low leakage current of 1$times hbox10^-7 hboxA/cm^2$at 1V are simultaneously measured. The small voltage dependence of a capacitance$Delta C/C$of 637ppm is also obtained at 2GHz, which ensures this MIM capacitor useful for high precision circuits operated at a RF regime.     

Successful enhancement of lifetime for SiO/sub 2/ on 4H-SiC by N/sub 2/O anneal

Time-dependent dielectric breakdown (TDDB) measurement by constant current stress has been performed to investigate the oxide (SiO/sub 2/) reliability grown on n-type 4H-SiC. At 300K, the intrinsic injected charge to breakdown (Q/sub BD/) of thermally grown SiO/sub 2/ in wet O/sub 2/ ambience is about 0.1 C/cm/sup 2/, whereas N/sub 2/O anneal after the thermal oxidation results in the drastic improvement of the reliability. The intrinsic Q/sub BD/ of N/sub 2/O annealed SiO/sub 2/ is found to be 10 C/cm/sup 2/, which is two orders of magnitude larger than that of the oxide without N/sub 2/O anneal, suggesting that the quality of SiO/sub 2/ and/or SiO/sub 2//SiC interface is improved. TDDB measurement has been also performed at high temperatures up to 423 K. The activation energy of oxide lifetime estimated from time to failure of 80% is 0.35 and 0.10 eV for the oxide with and without N/sub 2/O anneal, respectively.     

Very high-density (23 fF//spl mu/m/sup 2/) RF MIM capacitors using high-/spl kappa/ TaTiO as the dielectric

A very high density of 23 fF//spl mu/m/sup 2/ has been measured in RF metal-insulator-metal (MIM) capacitors which use high-/spl kappa/ TaTiO as the dielectric. In addition, the devices show a small reduction of 1.8% in the capacitance, from 100 kHz to 10 GHz. Together with these characteristics the MIM capacitors show low leakage currents and a small voltage-dependence of capacitance at 1 GHz. These TaTiO MIM capacitors should be useful for precision RF circuits.     

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.     

High-k Al/sub 2/O/sub 3/ gate dielectrics prepared by oxidation of aluminum film in nitric acid followed by high-temperature annealing

A simple, cost-effective, and room temperature process was proposed to prepare high-k gate dielectrics. An aluminum oxide (Al/sub 2/O/sub 3/) gate dielectric was prepared by oxidation of ultrathin Al film in nitric acid (HNO/sub 3/) at room temperature then followed by high-temperature annealing in O/sub 2/ or N/sub 2/. The substrate injection current behavior and interface trap-induced capacitance were introduced to investigate the interfacial property between the gate dielectric and Si substrate. Al/sub 2/O/sub 3/ gate dielectric MOS capacitors with and without initial SiO/sub 2/ layers were characterized. It was shown that the Al/sub 2/O/sub 3/ gate dielectrics with initial oxide exhibit better electrical properties than those without. The 650/spl deg/C N/sub 2/-POA Al/sub 2/O/sub 3/-SiO/sub 2/ sample with an equivalent oxide thickness of 18 /spl Aring/ exhibits three orders of magnitude reduction in gate leakage current in comparison with the conventional thermal SiO/sub 2/ sample.     

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.     

A new metal-ferroelectric (PbZr/sub 0.53/Ti/sub 0.47/O/sub 3/)-insulator (Dy/sub 2/O/sub 3/)-semiconductor (MFIS) FET for nonvolatile memory applications

Metal-ferroelectric-insulator-semiconductor (MFIS) field-effect transistors with Pb(Zr/sub 0.53/,Ti/sub 0.47/)O/sub 3/ ferroelectric layer and dysprosium oxide Dy/sub 2/O/sub 3/ insulator layer were fabricated. The out-diffusion of atoms between Dy/sub 2/O/sub 3/ and silicon was examined by secondary ion mass spectrometry profiles. The size of the memory windows was investigated. The memory windows measured from capacitance-voltage curves of MFIS capacitors and I/sub DS/-V/sub GS/ curves of MFIS transistors are consistent. The nonvolatile operation of MFIS transistors was demonstrated by applying positive/negative writing pulses. A high driving current of 9 /spl mu/A//spl mu/m was obtained even for long-channel devices with a channel length of 20 /spl mu/m. The electron mobility is 181 cm/sup 2//V/spl middot/s. The retention properties of MFIS transistors were also measured.     

High-density MIM capacitors using Al2O3 andAlTiOx dielectrics

We have investigated the electrical characteristics of Al₂ O₃ and AlTiO_x MIM capacitors from the IF (100 KHz) to RF (20 GHz) frequency range. Record high capacitance density of 0.5 and 1.0 μF/cm² are obtained for Al₂ O₃ and AlTiO_x MIM capacitors, respectively, and the fabrication process is compatible to existing VLSI backend integration. However, the AlTiO_x MIM capacitor has very large capacitance reduction at increasing frequencies. In contrast, good device integrity has been obtained for the Al₂O₃ MIM capacitor as evidenced from the small frequency dependence, low leakage current, good reliability, small temperature coefficient, and low loss tangent