We summarize various measurements of the thermal conductivity of thin ceramic films which show that the thermal conductivity of thin films with thickness in the micron and sub-micron range may be up to two orders of magnitude lower than the thermal conductivityof the corresponding bulk solid. The reduction in the thin film effective thermal conductivity is attributed to the interfacial thermal resistance across the film/substrate interface.

A new technique for the characterization of nitride electron traps responsible for the memory action of MNOS devices is proposed. It is assumed a uniform density of traps in the nitride bulk and an excess of interface traps which is described according to an exponential decreasing distribution. We have modelled the discharge of MNOS devices induced by the application of low positive gate voltages in samples previously charged up toits maximum level of trap occupancy. Since the discharge rate is necessarily dependent on the trapped charge distribution, it is possible to infer the spatial profile of traps by comparing the results obtained by computer simulation of the model to those obtained from field assisted discharge experiences in MNOS samples.

Oxide-Nitride-Oxide, ONO, heterostructures, fabricated by low-temperature, 300°C, Remote Plasma Enhanced Chemical Vapor Deposition, have been used as gate dielectrics in metal insulator semiconductor devices. Analysis of C-V data for this devices indicates that higher levels of fixed charge are associated with the internal dielectric interfaces. A high-temperature, ̃900°C, Rapid Thermal Annealing, RTA, step has been inserted into the process sequence for fabricating ultra-thin, 4.7 nm SiO2 equivalent, device-quality ONO dielectric layers. The electrical properties of these ONO dielectrics, including the Si/SiO2 interfacial trap density, the flat band voltage, the charge to breakdown and the reliability under electron injection are comparable to those of high temperature, thermally-grown oxides.

Ultra thin silicon nitride films have been indispensable in high density memory devices as a dielectric. We investigated the effect of the silicon surface state on initial silicon nitride growth process, we have used X-ray Photoelectron spectrometry (XPS), Secondary ion mass spectrometry(SIMS), and Capacitance-Voltage(C-V) characteristics. The results of our study show that the fluorine on silicon surface influences initial silicon nitride growth. The presence of fluorine delays low pressure chemical vapor deposition(LPCVD) silicon nitride growth as well as restraining native oxide growth at the silicon nitride/silicon substrate interface. We propose that it is a key process of thin dielectric films deposition to control fluorine on silicon surface.

The transient process of the accumulation of charge in the Silicon Nitride by applying a positive voltage pulse to MONOS structure is investigated with the help of the experimental and theoretical methods (monopolar injection of electrons). The mathematical model of charge carriers transport in an amorphous nitride thin films in MONOS structures at the high electric fields has been developed. The essential peculiarity of this modelis that the injected carriers from the contact are captured by a quasi - continuous spectrum of states that there are traps, having an exponential distribution of densityin the nitride band gap and by the monoenergetic positively charged deep centers. The positive traps are made by the negative correlation energy defects. These defects are formed by the weak quasi- hydrogenous bonds Si-H-Si the changes of ones in consequences of a migration of hydrogen stipulate for the degradation processes in the nitride. It is established that the quasi - distributed traps are answered for the prolonged relaxation of current in the external circuit when t≫Tg in which the exponent α of function J∼t-α is determined by the parameter of the energy distribution of traps and by the applied voltage on the structure that is in agreement with experimental results and corresponds to the dispersive transport of carriers.

In order to fill high quality insulators into narrower spaces in advanced metallizationthe digital CVD (Chemical Vapor Deposition) of multilayer stacked Si oxide and nitride films was studied. Reaction of TES (triethylsilane) with hydrogen (H) atoms was also found to lead to conformal CVD of Si film involving organic species. This reaction took place only on the surface reaction. In-situ FTIR studies reveal that H atoms react with Si-C2H5 bonds in TES and thus generate strong Si-CH3 bonds and weak Si-H bonds, thereby liberating H2 and forming the organic Si film on the surface, and the surface reaction is dominated by the thermal effect from the substrate. Then Si oxide or nitride films were formed by the digitaCVD which repeated a cycle of deposition of this film with subsequent oxidation or nitridation. Oxide film integrity was improved greatly by removing included organic bonds in the TES/H reaction film by exposing the film to H atoms before the oxidation step. Thus electrically excellent multilayer stacked oxide and nitride films were obtained in a deep trench.

Low temperature deposition of dielectric thin films is more and more used in very largescale integrated (VLSI) circuits. For this purpose, distributed electron cyclotron resonance (DECR) plasma appears to be a promising tool. The most interesting feature of this recent plasma is the high ion density (≈1011 cm−3) associated with low electronic temperature (2–3eV) and low energy species (20–30 eV). The purpose of this study is to discuss the effects of the reactant gas mixture composition (O2sol;SiH4) and the rf substrate bias power on the physical, chemical and electrical properties of DECR SiO2 films deposited at floating temperature (<100°C). Under optimum deposition conditions, the films show excellent characteristics, comparable to those obtained with thermal oxides grown at 850–1050°C.

Silicon dioxide was plasma-deposited at 300C using either the reaction of silane and nitrous oxide or the reaction of tetraethylorthosilicate with oxygen. The structural and electronic properties of films produced by both reactions were studied as functions of post-deposition heat treatments. The former reaction produced films which were more dense and less conductive than the latter. A model was developed to determine the amount and location of charge in the deposited films. The charge was found to be dependent on the reaction and the post-deposition anneal.

Silicon dioxide films have been deposited using a microwave plasma of (SiH4 + O2) excited by distributed electron cyclotron resonance. The ratio of flow rates of the reactive gas was (O2: SiH4) = 7 and no intentional substrate heating was used. The effect of ion energy during deposition, in the 10 — 150 eV range, has been studied through refractive index, infrared absorption bands, chemical etch rate and electrical measurements. It is found that for an ion energy > 50 eV, many of the film characteristics are close to those of thermal SiO2.

Rapid thermal annealing is investigated for curing spin-on glass insulating films. The annealed SOG films were mainly evaluated using infrared absorption spectroscopy and by electrical measurement of the defects present at the Si/Sio2 interface. We found in particular after rapid thermal annealing an important densification of the layers as a function of temperature and a reduction of the interfacial state densities which are comparable to classical thermal oxides.

Borophosphosilicate glass (BPSG) is an essential insulating material used to modify thecomplex topography of highly dense, next generation dynamic random access memory (DRAM)devices. The shallow junctions in 16 and 64 Meg DRAMs can only be maintained by severely restricting the time, temperature, and atmosphere of all thermal process steps following the junction implant.

In this paper we present the results of rapid thermal process (RTP) assisted reflow of BPSG over complex topographies and compare the results of RTP to furnace reflow in both dry and wet ambients. We also compare the out-diffusion of boron and phosphorous from BPSG films during the RTP and furnace reflow. We found an optimum RTP cycle that completely removes voids in the vicinity of overhang geometries and provides sufficient activation of the underlying dopants (as compared to a furnace reflow and activation cycle). In this study we used the results of boron and phosphorous profile redistribution, underlying dopant activation, and the amount of reflow to compare RTP and furnace processing techniques.

This paper explains the analysis and elimination of BPO4 crystal formation in an Atmospheric Pressure Chemical Vapor Deposition BPSG film. Film deposition and furnace anneal/flow parameters were studied using full factorial techniques, with anneal/flow parameters having the most significant effect. It was learned that BPO4 crystals could be readily induced by performing the anneal/flow process in a POCl3/O2 ambient. Most testing was done in a POCl3/O2 ambient and inferences made concerning the standard anneal ambient.

BPO4 formation is primarily dependent on thermal processing during anneal toprovide the activation energy necessary to initiate crystal growth. Other factors include 02:Hydride ratio during film deposition, phosphorous concentration in the deposited film, deposition temperature, and anneal/flow ambient. No tested level of these secondary factors completely eliminated crystal formation.

The growth of BPO4 crystals can be eliminated by controlling the thermal environment ofthe anneal/flow step. The primary means employed was to increase the rate of heat dissipation by doubling the spacing between wafers. An alternative method involves utilization of reduced anneal/flow furnace temperatures.

Destructive breakdown in silicon dioxide is shown to be strongly correlated to the oxide degradation caused by hot-electron-induced defect production and charge trapping ner the interfaces of the films. Two well defined transitions in the chargc-to-breakdown data as a function of field and oxide thickness are shown to coincide with the onset of mechanisms due to trap creation and impact ionization by electrons with energies exceeding 2 and 9 eV (the SiO2 bandgap energy), respectively. The temperature dependence of charge-to-breakdown is also shown to be consistent with that of these two defect-producing mechanisms.

Current-voltage and conductance-voltage characterization is used to study high bias related “positive charge” in MOS tunnel diodes fabricated on p-type substrates. This charge effect appears to be associated with interface state levels that are located both throughout the band gap, and at a well-defined energy level roughly 0.3 eV above the silicon valence band edge. The well-defined state apparently acts as a tunnelingcenter communicating with the gate electrode and the silicon valence band. In addition, the first observation of high bias related charge is reported for tunnel diodes built on n-type substrates. This charge has positive character at low bias levels, transforming to net negative charge at high gate voltages.

It has been shown that the transient decay of the current after removal of a high voltage stressing pulse changed from an exponential RC time constant decay to a very long decay that had a 1/t time dependence[l]. During these long transients the flat-band voltages of the capacitors changed as the traps inside the oxides discharged. The discharge of both positive and negative changes near the silicon-oxide interface have been measured using QSCV measurements. In this paper the transient shifts in the flat-band voltages due to the discharging of stress generated traps in the oxide will be described.

As design rules shrink to conform with ULSI device dimensions, gate dielectrics for MOSFET structures are required to be scaled to even thinner proportions. Upon scaling the gate oxides below ∼60Å the interfacial region becomes a significant proportion of the total film. Thus interface properties are weighted more heavily in determining device performance and reliability.

We have developed a Pump-Probe charge integrating measurement technique for studying the emission kinetics of traps in the M/SiO2/Si system. Essentially, a MOS capacitor is pumped by exposure to a charging pulse. The emission of the charge at short time scales (<10ms), can be measured using a delayed application of a probe pulse which determines the remainder of the filled traps as a function of delay time. For a lightly doped p-Si (lll) substrate, we observe an uncommon behavior of the emission kinetics in the initial time regime (< 100ms). A possible explanation for this phenomenon is the perturbation of the emission cross-section of the probed traps due to the presence of another state in communication with the trap site.

After thin silicon oxide films were stressed at high voltages, two changes occurred in the current-voltage and transient current characteristics of the films. The low-level, pre-tunneling current rose and the transient decay of the current after removal of a voltage pulse changed from an exponential RC time constant decay to a very long decay that was characterized by a 1/t time dependence. Using an extension of the tunneling front discharge model, previously developed to describe the transient changes in the threshold voltages of transistors after avalanche injection or irradiation, the 1/t time dependence was derived. This 1/t transient discharge current was used to determine the density and distribution of the traps inside of the oxide after the high voltage stress. The technique and model used for determining the trap densities and distributions from the transient currents will be described. The model was used to describe the charging of traps in the oxide.

Redistribution of hydrogen caused by hot electron injection has been studied in large Al-gate capacitors using internal photemission followed by hydrogen depth profiling with the 15 N nuclear reaction. A large peak of hydrogen (∼ 1015 at /cm2) at the Al/SiO2 interface due to a hydrated layer on the surface of the SiO2 was found to act as a source of hydrogen during the photoinjection. A small fraction of the hydrogen released from this peak was found to be re-trapped near the Si/;SiO2 interface if a field of >1 MV/cm was applied to the SiO2 during the injection. Up to 2 × 1014 atoms/cm2 of hydrogen were found to be trapped at this interface for injected fluences up to 5 C/cm2. These results are discussed in terms of current models of interface state generation involving hydrogen.

Hydrogen is a common impurity in silicon dioxide (SiO2) which can influence its optical and electronic properites. Here, nuclear magnetic resonance (NMR) is applied to study of hydrogen in these materials, despite their relatively low hydrogen content. We present results for bulk fused silica as well as thermally grown films of SiO2 on silicon. These experiments demonstrate the potential of solid state NMR for studying low hydrogen content film systems. In bulk fused silica, we have observed that although the majority of hydrogen is isolated, a small number of centers exist involving adjacent silanol pairs. These pairs react during high temperature annealing as well as during deep ultraviolet irradiation. Furthermore, the presence of these centers is related to the susceptibility of fused silica to radiation damage. The results obtained on the fused silica material are compared to SiO2 films on silicon. The NMR spectra and relaxation associated with thick (>1μm) wet SiO2 films are similar to those for the fused silica while the NMR data for thinner oxide more closely resembles those of surface water on silica gel.

Amorphous SiO2 films formed by thermal oxidation of silicon have been bombarded by low-energy (350 — 400 eV) ion beam and neutral beam of inert atoms. The modified SiO2 layers have been characterized by Auger electron spectroscopy (AES), Rutherford backscattering spectroscopy (RBS) and reflection high energy electron diffraction (RHEED). It is shown that neutral beam bombardment does not cause preferential sputtering of oxygenfrom SiO2, whereas ion beam of the same energy causes significant preferential sputtering. For neutral bombardment, densification and crystallization of SiO2 have been observed. The formation of α-cristobalite and α-quartz from amorphous SiO2 has been observed for high dose bombardments (>1017neutrals/cm2). These densification and crystallization phenomena can be attributed to high temperature and high pressure local spot formation upon the incidence of energetic neutral atoms. For ion beam bombardments, these densification and crystallization phenomena have not been observed.