摘要:

Low pressure chemical vapor deposition (LPCVD) of SiO2in a horizontal LPCVD furnace using liquid diethylsilane and oxygen has been studied. A temperature deposition window ranging from 425–500 °C was observed resulting in a maximum deposition rate of ∼275 Å/min. The pressure dependence of the deposition rate revealed a threshold of ≳950 mTorr for gas phase reactions at a deposition temperature of 450 °C. Analysis of the films by Rutherford backscattering spectroscopy has indicated that as‐deposited films are stoichiometric SiO2for deposition temperatures ≤450 °C. Best case across wafer uniformity was ±5% for a caged boat. Wet chemical and reactive ion etch rates were found to be comparable to those of thermal oxides after annealing. Cross‐sectional scanning electron microscopy images of the SiO2films deposited on 2 μm deep 1 μm wide silicon trenches revealed a conformality of ∼80%. The electrical properties of films deposited at 450 °C were studied. The electrical properties of the films were studied as‐deposited and after annealing the films in a cold‐wall rapid thermal annealing (RTA) system. RTAs were performed at temperatures ranging from 950 to 1100 °C in Ar, N2, or O2ambients. Current–voltage, current–temperature, and capacitance–voltage measurements were performed for the electrical characterization. Catastrophic breakdown field measurements have shown electric field strengths of 9.5 MV/cm for as‐deposited 500 Å films. A study of the leakage current conduction mechanisms has indicated that as‐deposited films exhibit trap conduction mechanisms at high electric fields and temperatures. However, if deposition is followed by a RTA in Ar or O2, the leakage current follows closely the Fowler–Nordheim mechanism and yields a leakage‐current electric field dependence comparable to a thermal oxide. Results have shown that values as low as 6 × 1010/cm2for fixed charge density can be obtained if oxide deposition is followed by a RTA in Ar or N2.

ISSN:1071-1023    

DOI:10.1116/1.586423

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Borophosphosilicate glass films prepared by chemical vapor deposition techniques based on atmospheric pressure, low pressure with liquid and gaseous sources, and low pressure plasma enhanced processes in the temperature range of 390–680 °C have been studied. Films with lowB(1.5 wt %) and highP(9.0 wt %) content were used for this study. To evaluate the effect of different thermal treatments, the films were annealed in a horizontal furnace at 920 °C for 30 min in three different ambients, i.e., N2, N2/O2, and H2/O2and with rapid thermal annealing at 1050 °C for 10 s in a N2ambient. The main properties of the as‐deposited and annealed samples such as elemental content, thickness uniformity, shrinkage, density, refractive index, wet etch rate, stress, step coverage, and reflow are reported. Infrared absorption measurements were performed to study the water and Si–OH group presence in the films and P=O, B–O, Si–O bond behavior and interactions. The best physical and chemical film properties were obtained using liquid sources in a low pressure system. These films were tested as the interlevel dielectric in 1 Mbit erasable programmable read‐only memory devices and good electrical performances were obtained, comparable with atmospheric pressure deposited films.

ISSN:1071-1023    

DOI:10.1116/1.586424

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The process and feasibility verification for a full wafer silicon‐on‐insulator (SOI) process by using two merged epitaxial lateral overgrowths has been achieved. This process can be used to produce SOI material with a wide range of silicon thicknesses from 0.1 μm to several microns thick and is compatible with three‐dimensional circuit integration. Formation of local area SOI islands, formation of vertical wall seed windows, and epitaxial lateral overgrowth from these narrow vertical seeds have been demonstrated. This SOI process has the potential to reduce the defect density and cost of SOI substrates.

ISSN:1071-1023    

DOI:10.1116/1.586425

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The range profile for the combination implantation of10B and11B into the three stable isotopes of silicon28Si,29Si, and30Si in the energy range between 1 and 50 keV, has been studied by using the Monte Carlo simulation programtrim. It is found that for a given boron isotope, the implantation profile depends strongly on the isotopic state of silicon. The presence of the least abundant isotopes29Si and30Si, in silicon of natural abundance, influence considerably the range profile.

ISSN:1071-1023    

DOI:10.1116/1.586426

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Molecular dynamics simulations are used to model the formation of deep crystalline damage during the low‐energy ion bombardment of semiconductor crystals. For beams of heavy ions at energies below a kilovolt, the average penetration range of the simulated trajectories is only a few nanometers. However, a small, but significant, fraction of the ions are found to scatter into 〈011〉 axial channels through which they propagate tens of nanometers below the surface. A model is developed to convert the simulated ion channeling probabilities into predictions of optical damage as a function of depth in the crystal. The results are used to explain the recent measurements of anomalous degradation of deep quantum wells during dry etching of III–V semiconductor heterostructures. The model is also used to evaluate several strategies intended to avoid this unintentional ion channeling and to reduce the creation of deep damage during low‐energy ion bombardment.

ISSN:1071-1023    

DOI:10.1116/1.586427

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The transport properties of molecular‐beam epitaxially grown InSb films doped with Er (atom densities NErfrom 4.3×1016cm−3to 3.6×1020cm−3) are reported at temperatures between 40 and 400 K. Er is a donor in InSb films grown under Sb to In flux ratios smaller than 1.1. At a flux ratio Sb/In=1.06, 25 atoms of Er give one extrinsic electron. The maximum extrinsic electron concentration achievable is ∼1.8×1017cm−3, obtained for NEr≳4×1018cm−3. Magnetoresistance measurements at 4.2 K show evidence for spin–disorder scattering of the electrons. The low‐temperature (T<150 K) electron mobility increases with doping concentration up to rare‐earth densities of 1×1018cm−3; at higher rare‐earth concentrations, the mobility decreases again. At room temperature, the mobility decreases monotonically with increasing Er concentration. We note the analogy between these results and the observations made on HgSe:Fe, a system in which the carrier mobilities might be enhanced by impurity charge ordering.

ISSN:1071-1023    

DOI:10.1116/1.586428

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Ga outdiffusion into Ge layers grown epitaxially by molecular beam epitaxy was observed by secondary ion mass spectroscopy, x‐ray photoemission spectroscopy, capacitance–voltage, and temperature dependent Hall‐effect measurements. Films were initially grown at low rates (0.03–0.04 nm/s) and low temperatures (150–300 °C) on GaAs buffer layers on GaAs (100) substrates. The temperature and rate were then increased to 500 °C and 0.1 nm/s. The amount of Ga outdiffusion was greatest for films initially grown at 300 °C. No direct evidence of As outdiffusion at any temperature or Ga outdiffusion for initiation temperatures below 300 °C was found. Hall‐effect measurements showed higher hole concentrations and greater levels of compensation in films initiated at 300 °C, consistent with outdiffusion of both Ga and As at this temperature. No degradation in the electrical characteristics of Ge–GaAs diodes was observed when the initial Ge growth temperature was reduced from 300 to 200 °C.

ISSN:1071-1023    

DOI:10.1116/1.586429

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

The etching of the (100) face of gallium arsenide with molecular iodine has been studied at I2pressures between 0.10 and 1.25 Torr and in the temperature range from 270 to 330 °C. GaAs was found to be etched continuously at rates between 0.05 and 1.70 μm min−1under these conditions. Although the etch rate appears to be first order with respect to I2at pressures below 0.3 Torr, the order decreased at higher pressures. The data was analyzed in terms of two mechanisms, which have been proposed for the etching of semiconductors by halogen molecules. These are the ‘‘reversible dissociative adsorption’’ (RDA) mechanism, and the ‘‘surface site saturation’’ (SSS) mechanism. In the RDA mechanism the dissociative adsorption, which explains the nonlinear pressure dependence, occurs irreversibly at low pressure giving rise to first order kinetics with a first order rate constant (k1) which can be expressed in the following Arrhenius form:k1=104.7±0.2μm min−1 Torr−1exp[−(55±2) kJ mol−1/RT]. At higher pressures, the dependence on I2changes to half order and the composite half order rate constant (k1/2) can be represented by the equation:k1/2=106.5±0.9μm min−1 Torr−1/2exp[−(69±10) kJ mol−1/RT]. On the other hand, the SSS mechanism involves the reversible physisorption of I2on the GaAs surface (governed by an equilibrium constantK) followed by a rate controlling reaction of this physisorbed species leads to products (governed by the rate constantk4). The values obtained for these two constants are:K=10−4.8±0.7Torr−1exp[+(49±7) kJ mol−1/RT], andk4=109.2±0.4μm min−1exp[−(96±5) kJ mol−1/RT]. The etching is isotropic, and the major products are GaI3and AsI3.

ISSN:1071-1023    

DOI:10.1116/1.586430

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

We analyze the effect of the conduction band offset in the collector heterojunction inNpNGaAs/Ge/GaAs double heterojunction bipolar transistors (DHBT). Despite excellent diode characteristics in both the emitter‐base and base‐collector diodes, the GaAs/Ge/GaAs DHBTs exhibit relatively low common‐emitter dc current gains and a lack of collector current saturation with increasing collector‐emitter bias. Simulations indicate that this is at least in part attributable to a reduction in collection efficiency caused by the large collector‐base conduction band offset (0.26 eV) between the Ge base and the GaAs collector. A modified collector design, which incorporates higher doping in the region of the GaAs conduction band spike, is proposed to decrease the width of the barrier to electrons. Simulations predict that the collection efficiency will be greatly improved with the incorporation of a modified collector.

ISSN:1071-1023    

DOI:10.1116/1.586431

出版商:American Vacuum Society    

年代:1992

数据来源: AIP

摘要:

Epitaxial GaAs/Ca0.5Sr0.5F2(1800 Å)/GaAs heterostructures have been grown by molecular‐beam epitaxy on (100), (111)A, (511)A, (511)B, (711)A, and (711)B GaAs substrates. We used reflective high‐energy electron diffraction, Auger electron spectroscopy, low‐energy electron diffraction, Rutherford backscattering (RBS), scanning electron microscopy, and Raman scattering to study the surface morphology, crystallinity, and chemical composition of these films. On the (100) orientation, the top GaAs had a flat microstructure; the surface crystallinity improved with increased thickness from 500 Å to 1 μm, but the size of grains due to antiphase disorder also increased with thickness. On the (111)A orientation, the GaAs formed (100)‐facets to lower the surface free energy. The surface morphology and near‐surface crystallinity improved with increased thickness. The top GaAs films from (511)A and (511)B substrates showed the best near‐surface crystallinities from RBS, electron channeling pattern, and Raman scattering experiments. The properties of top GaAs on (711)A and (711)B substrates were not as good as those from (511)s, but better than those from (100) and (111)A.

ISSN:1071-1023    

DOI:10.1116/1.586432

出版商:American Vacuum Society    

年代:1992

数据来源: AIP