High-temperature post-oxidation annealing of poly-Si/SiO2/Si structures such as metal-oxidesemiconductor capacitors and metal-oxide-semiconductor field effect transistors is known to result in enhanced radiation sensitivity, increased 1/f noise, and low field breakdown. We have studied the origins of these effects from a spectroscopic standpoint using electron paramagnetic resonance (EPR) and atomic force microscopy. One result of high temperature annealing is the generation of three types of paramagnetic defect centers, two of which are associated with the oxide close to the Si/SiO2 interface (oxygen-vacancy centers) and the third with the bulk Si substrate (oxygen-related donors). In all three cases the origin of the defects may be attributed to out-diffusion of O from the SiO2 network into the Si substrate with associated reduction of the oxide. We present a straightforward model for the interfacial region which assumes the driving force for O out-diffusion is the chemical potential difference of the O in the two phases (SiO2 and the Si substrate). Experimental evidence is provided to show that enhanced hole trapping and interface-trap and border-trap generation in irradiated high-temperature annealed Si/SiO2/Si systems are all related either directly, or indirectly, to the presence of oxygen vacancies.

The necessity of employing nitridation process in advanced technologies will be underlined. The different technological alternatives for preparing oxinitride layers will be traced back, followed by a review of the methods currently available for assessing the degradation features of the Si/SiO2 system. Furthermore, comparison between pure SiO2 layers and nitridated films in N2O ambient will be conducted in terms of bulk/interface trapping properties and the obtained physical degradation data will be correlated with classical reliability results. Large emphasis will be given on the trapping properties of tunnel oxides used in non—volatile memory arrays and different technological alternatives will be exploited (i.e. Rapid Thermal Nitridation, Furnace Nitridation). In addition, a similar analysis will be carried out for gate oxides. Finally, some guidelines concerning the optimum selection of the furnace nitridation conditions will be given.

This work describes an orthogonal array (OA8) designed experiment involving several insitu process perturbations during oxidation to develop a 90 Å gate oxide for 0.5μm CMOS technology. The biggest impactors were (i) the insitu preoxidation anneal at oxidation temperature, Tox, (ii) 90% N2 dilution of the ambient during ramp-up, and (iii) lowering the Tox to 850°C. Significant improvements in leakage, breakdown, and wear-out characteristics of the oxide are probably due to the reduction of poor quality ramp oxide grown by 90% N2 dilution and improved Si/SiO2 interfacial substructure attained by the insitu preoxidation anneal.

In this work, an electron spin resonance study of NH3-nitrided, N2O-nitrided, and N2O-grown oxides yields information relating the process history, point defect structure, and electrical behavior. NH3-nitridation is responsible for the introduction of bridging nitrogen centers, high capture cross section neutral electron traps, while N2O-processed dielectrics never exhibit these defects. In addition, structural changes at the interface due to nitridation result in observable differences in the interfacial defects.

We combine electron spin resonance measurements with vacuum ultraviolet, ultraviolet, and corona bias charge injection schemes to examine the properties and charge trapping roles of three E′ variants in conventionally processed thermally grown thin film SiO2 on Si.

Rapid thermal chemical vapor deposition (RTCVD) oxides formed using TEOS and oxygen (O2) are compared with RTCVD oxides formed using silane (SiH4) and nitrous oxide (N2O). These oxides were deposited under varying pressure and gas composition to investigate the film step coverage and electrical properties. Cross-sectional scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used in determining the oxide step coverage. Excellent oxide conformality, greater than 90 %, was achieved with SiH4 and N2O over a wide range of aspect ratios. The average breakdown field obtained for the SiH4/N2O oxides is approximately 13 MV/cm, which is greater than values measured for oxides formed by conventional dry thermal process. Oxides deposited using TEOS typically have an average breakdown field of about 8 MV/cm. We conclude that the SiH4/N2O oxide process for the deposition of SiO2 films in a RTCVD reactor is a very promising candidate for sidewall spacer formation in advanced device applications.

Plasma etching can cause damage in gate oxide during ULSI processing. The damage in the oxide is believed to arise through a high field induced stress current. However, there is another type of damage which is due to ion and photon bombardment on the edge of poly-Si gate during the plasma etching. These two damage mechanisms impose different reliability problems. One is hot-carrier(HC) stress and the other is Fowler-Nordheim(F-N) stress. MOS devices with special test structures to assess plasma process damage were fabricated using 0.35 μm CMOS technology. The devices with different poly gate antennas and etching through different poly-Si gate etching conditions were studied using SEM and various electrical techniques. It was found that oxide charging damaged device is more susceptible to F-N type of stress while ion and photon bombardment damaged device is more susceptible to HC type of stress.

The effect of power on the properties of SiO2 films produced by direct plasma-enhanced chemical vapor deposition using nitrous oxide and silane with high helium dilution has been investigated. As the power increases the p-etch rate decreases while the frequency of the Si-O-Si stretching vibration measured by Fourier transform infra-red spectroscopy increases. However the refractive index of the films measured by ellipsometry is almost constant as is the electron density measured by low-angle x-ray reflection, indicating that the structural changes of the film with power do not relate to bulk density changes. The x-ray and ellipsometry measurements indicate the existence of a transitional layer with monolayer dimensions at the Si/SiO2 interface.

In this paper we address the degradation of oxide reliability after annealing the phosphorusdoped polysilicon of MOS structures. The oxide reliability was studied in terms of X-ray radiation sensitivity as well as breakdown characteristics.

We found that annealing the polysilicon increased the radiation sensitivity of the gate oxide. We believe that this increase is a result of the phosphorus out-diffusion from the polysilicon into the oxide and a result of the creation of phosphorus related traps in the oxide bulk. We also found that the oxide charge to breakdown (Qbd) degradation correlates well with the density of the phosphorus in the oxide.

The ac conductance-voltage (G–V) characteristics at various frequencies have been measured in MOS diodes which suffered constant current stress by Fowler–Nordheim (F–N) electron injection from Si substrate.It is found that a double-peak structure appears in G–V curve and grows continuously with proceeded current stress.The growth of two kinds of interface states is elucidated after subtracting the effect of oxide capacitance and substrate resistance by a simple equivalent circuit analysis.

For integrated circuits, the integrity and film quality of the final passivation layer plays an important role in the device performance and reliability. Hydrogenated amorphous silicon oxynitride (α-SixNyOz:H) films deposited by plasma enhanced chemical vapor deposition (PECVD) have been extensively used for final device passivation applications. In this paper, a detailed characterization of PECVD oxynitride process for 200 mm Si wafer processing is presented. Silicon oxynitride of various compositions were deposited by changing the amounts of silane, ammonia, nitrogen and nitrous oxide in the reactant gas stream. Ultraviolet/Visible (UV/VIS) spectroscopy, Fourier transform infrared (FTIR) spectroscopy, Rutherford backscattering spectrometry (RBS), and refractive index measurements were used to examine the variation in physical, optical and electrical properties. A correlation is observed between the oxynitride film composition, mainly N-H/Si-H ratio, and UV transmissivity (UV %T) which is of particular interest for memory applications. Effects of oxynitride film quality on e-test parameters and device performance are discussed.

Diffusion-induced precipitation in arsenosilicate glass (AsSG) under high temperature anneal is studied by high resolution Transmission Electron Microscopy (TEM), and other techniques. Polycrystalline precipitates of a few hundred angstroms in size have been observed near the interface of AsSG and the silicon substrate, covering the entire interface area after high temperature anneal. It is proposed that high concentrations of arsenic (above the solid solubility limit) precipitate initially at nucleation sites near the AsSG/silicon interface. Further anneal-induced diffusion of arsenic to the interface promotes growth of the precipitates. As a result, the precipitates cover the entire interface area, and impede further As diffusion into the Si substrate. Techniques to avoid the precipitation process without compromising the thermal budget or reduced arsenic diffusion have been explored and will be discussed.

Adhesion of thin films to solid substrates has been measured by various methods. In addition to the traditional and the conventional methods, a novel method has been proposed. The adhesion is expressed by various units depending on the measuring method. Obtained values by typical or well known methods such as scratch, peel and pull method are expressed in terms of N, N/m and N/m2, respectively. Relation among these quantities was discussed. The interface structure between the films and the substrates was investigated by TEM, ED, EDS, etc. and was related to the adhesion. Particular attention was paid to the ion bombardment effect of the substrate on the adhesion.

This paper shows experimental results concerning the life time of mirrors irradiated with a continuous wave CO2 laser. An experimental process and a possible mecanism of degradation are discussed.

Two types of mechanical tests associated with acoustic microscopy characterizations were performed to investigate the mechanical stability of PSG and Si3N4 passivation films. An in situ tensile test micro-device was installed under a scanning acoustic microscope to study the damage development in the passivation films deposited on A1,1%Si substrates. The analysis of the attenuation of the acoustic signature of the film/substrate systems and the variations of the leaky surface acoustic wave velocity permitted detection of the cracking and decohesion of the passivation films. The four-point bending test was used to submit passivated aluminum multilayers deposited on silicon substrates to cyclic compression. Then subsurface acoustic images revealed decohered zones in the passivation.

Multi-layer semiconductor structures (quantum wells and grain boundaries) grown by molecular beam epitaxy (MBE) as well as precipitates in glasses are investigated by high resolution electron microscopy (HREM) providing local atomic information at the relaxed interfaces. The interpretation of the micrographs requires methods of image analysis and the computer simulation of the HREM contrast by calculating the electron beam specimen interaction of a theoretical structure model, and by subsequently considering the electron-optical process. The relaxed atomic structures of the interfaces are modelled by molecular dynamics and energy minimization with the bonding forces and the parameters of the pair and three-body potentials being varied. Possibilites will be discussed of revealing the compositional variations and the elastic deformations at the interfaces by HREM imaging under special imaging conditions.

The effects of stress on the measurement of hardness and elastic modulus in aluminum alloy 8009 have been studied experimentally and by finite element simulation. The experiments were performed by making a linear array of nanoindentations on the side of a stressed bend bar, sampling regions of high uniaxial tension, high uniaxial compression, and a variety of stresses in between. When analyzed according to standard methods, the nanoindentation data reveal a decrease in both hardness and modulus with increasing stress from compression to tension. While the decrease in hardness is consistent with previous observations made in conventional hardness testing, the modulus decrease was unexpected. Finite element simulation revealed that the drops in hardness and modulus are not real, but occur because the procedure for determining contact area from the nanoindentation load-displacement data does not account for pileup around the indentation. The finite element simulation shows that large compressive stresses promote pileup while tensile stresses reduce it, and this must be properly accounted for if accurate hardnesses and moduli are to be obtained. Experimental results are presented which further support this point of view.

Micromechanical tensile experiments in a Scanning Electron Microscope (SEM) allowed us to identify and follow the activation of a variety of different deformation mechanisms, on several sorts of films on substrate systems. The investigated systems consisted of SiO2 and YF3 films deposited on copper and aluminium substrates, with or without an interlayer. The experimental results show that the mechanical response of the films differs, in particular, with respect to the interface response: the cracking activity will depend on the film adhesion. An attempt is made to relate the microstructural parameters of the assembled materials with the observed mechanisms, through models which are based on the shear lag formalism. Critical parameters of the systems under stress are determined and compared to theoretical calculations: critical stresses and strains for cracking, stress transfer lengths, interfacial fracture energies. The approach gives some insights on the mechanical response of films on substrate systems submitted to a tensile state of stress.

A stress calculation method is proposed by improving the force and moment balance method to calculate the stress in semiconductor layers. The following three points are improved. The first point is that the vertically precise stress distribution in multilayers can be calculated by using imaginary thin layers. The second point is that the stress can be calculated on the basis of threedimensional deformation. The third point is that the stress can be calculated in strained layers with interfacial misfit dislocations. The stress distribution in strained semiconductor layers such as InGaAs/GaAs multilayers, InGaAs/graded lnGaAs/GaAs layers and GaAs/Si structures is calculated using this improved method.

Carbon-doped base GaAs/AlGaAs HBTs display current-induced decreases in dc gain which are correlated with the amount of hydrogen incorporated in the base layer during growth by Metalorganic Molecular Beam Epitaxy (MOMBE). During device operation, minority carrier injection induced debonding of hydrogen from neutral C-H complexes leads to an increase in effective base doping level and therefore to a decrease in gain. Post-growth in-situ or ex-situ annealing eliminates this effect by breaking up the C-H complexes. Properly designed HBTs are stable even for very high collector current densities (105 A · cm−2)