Thickness Of Silicon Dioxide Film Research Articles

Effect of oxygen plasma on nanomechanical silicon nitride resonators

Precise control of tensile stress and intrinsic damping is crucial for the optimal design of nanomechanical systems for sensor applications and quantum optomechanics in particular. In this letter, we study the influence of oxygen plasma on the tensile stress and intrinsic damping of nanomechanical silicon nitride resonators. Oxygen plasma treatments are common steps in micro and nanofabrication. We show that oxygen plasma for only a few minutes oxidizes the silicon nitride surface, creating several nanometer thick silicon dioxide layers with a compressive stress of 1.30(16) GPa. Such oxide layers can cause a reduction in the effective tensile stress of a 50 nm thick stoichiometric silicon nitride membrane by almost 50%. Additionally, intrinsic damping linearly increases with the silicon dioxide film thickness. An oxide layer of 1.5 nm grown in just 10 s in a 50 W oxygen plasma almost doubled the intrinsic damping. The oxide surface layer can be efficiently removed in buffered hydrofluoric acid.

SimultaneousIn situMeasurement of Silicon Substrate Temperature and Silicon Dioxide Film Thickness during Plasma Etching of Silicon Dioxide Using Low-Coherence Interferometry

Simultaneous<i>In situ</i>Measurement of Silicon Substrate Temperature and Silicon Dioxide Film Thickness during Plasma Etching of Silicon Dioxide Using Low-Coherence Interferometry

Simultaneous In situ Measurement of Silicon Substrate Temperature and Silicon Dioxide Film Thickness during Plasma Etching of Silicon Dioxide Using Low-Coherence Interferometry

We have successfully performed real-time noncontact monitoring of substrate temperature and thin film thickness during plasma etching using optical-fiber-based low-coherence interferometry. The simultaneous measurement of the silicon (Si) substrate temperature and the etching depth of the silicon dioxide (SiO2) thin film on this substrate was performed in a dual-frequency capacitively coupled Ar/C4F8/O2 plasma. The SiO2 film thickness was deduced from the ratio of the interference intensity at the SiO2/Si interface to that at the Si/air interface. The measurement error in the SiO2 film thickness was less than 11 nm. The temperature variation of the Si wafer was derived from the temperature change of its optical path length. The temperature measurement error, caused by the shift in optical path length due to the change in SiO2 film thickness, was reduced from 7.5 to 0.6 °C by compensating for the shift using the SiO2 thickness data. This method enables precise control of etching performance and improves process reproducibility.

Photodetective Characteristics of Metal–Oxide–Semiconductor Tunneling Structure with Aluminum Grid Gate

The photodetective characteristics of aluminum grid gate–ultrathin silicon dioxide–silicon structures have been studied. The on–off ratio calculated from the photo and dark current densities rapidly changes at the threshold optical-power density. The threshold optical-power density is controlled by the silicon dioxide film thickness and increases with decreasing silicon dioxide film thickness. The difference between the surface potential with and without light irradiation rapidly changes at the same optical-power density. Holes do not significantly accumulate under optical-power densities lower than the threshold.

Enhanced Silicon Oxidation by a Hyperthermal Beam Obtained from Laser Evaporation of Solid Ozone

A new oxidation method for gate oxide applications using a collimated neutral hyperthermal ozone beam produced by pulsed laser evaporation of solidified ozone is demonstrated. This method enables ozone molecules, together with oxygen molecules and oxygen atoms, in an electronically excited state, with a translational energy of around 1 eV to be intermittently supplied to silicon just after each laser shot, so that the silicon dioxide film thickness can be accurately controlled by the number of laser shots. The effect of ozone having this translational energy was clearly apparent from the temperature-independent initially high oxidation rate, which enabled the oxidation to be shorter and with a lower temperature process. Compared to oxidation by the conventional method using thermal ozone gas, higher efficiency was achieved in the sense that a thicker film could be obtained with a smaller number of ozone molecules as long as the oxidized area was localized. Further enhanced oxidation was enabled by using a hyperthermal beam rich in that had been obtained at a high laser fluence irradiation, demonstrating the high reactivity of compared to the ground-state oxygen atom, © 2002 The Electrochemical Society. All rights reserved.

Enhanced oxidation of silicon using a collimated hyperthermal ozone beam

Silicon was oxidized by a collimated hyperthermal ozone beam produced by pulsed-laser ablation of solid ozone to increase the controllability of the silicon dioxide film thickness and to achieve low-temperature oxidation. The oxidation rate could be accurately controlled by the number of laser shots to which the number of supplied ozone molecules was proportional. Ozone molecules with a translational energy of around 1 eV obtained by laser ablation produced an initially rapid oxidized region with no temperature dependence in which a 0.6 nm silicon dioxide film could be synthesized at room temperature with only 200 laser shots. Higher-efficiency oxidation was also achieved in comparison with that by using a spray of ozone with thermal energy.

Reaction of Hydrogen Fluoride Gas at High Temperatures with Silicon Oxide Film and Silicon Surface

The chemical nature of hydrogen fluoride gas at high temperatures, 523–1173 K, for etching silicon dioxide in hydrogen ambient at atmospheric pressure is studied, for the first time. Although only a slight decrease in the silicon dioxide film thickness can be observed below 1000 K, its surface is significantly etched above 1000 K. Hydrogen fluoride gas in the temperature range of 500-1000 K in hydrogen ambient is experimentally shown to be nonreactive with silicon dioxide. The existence of water molecules is necessary for hydrogen fluoride gas to etch silicon dioxide even at high temperatures. At temperatures above 873 K, hydrogen fluoride gas can react to roughen the surface of the silicon substrate. The corrosion of silicon carbide by hydrogen fluoride gas is also observed as the formation of pits at the surface.

Effects of External Silicon Dioxide and Surface Roughness on the Radiative Melting of Silicon

Radiative melting of silicon surfaces on one side, with an incandescent source is examined as a function of external silicon dioxide film thickness and surface topography. Surface emissivities incorporating these variables are related to silicon melt depth by employing an optical cavity model. Experimental agreement with the model is good, demonstrating that careful consideration of film thickness, surface topography, and spectral output of incident radiation is required in order to optimally control silicon melt depths. Melt depth is profoundly influenced by surface emissivities which are shown to be, themselves, functions of external oxide thickness and surface topography. Not only do sharp differences exist between the optical properties of polished and sandblasted surfaces, but the data demonstrate that differences in the “degree” of sandblasting can also result in markedly different melt profiles. Furthermore, since radiative heating is from one side, while radiative cooling occurs from all sides, specific preparations of irradiated surfaces resulting in enhanced incident energy coupling, and increased melt depths, have an opposite effect when applied to nonirradiated surfaces. This allows for controlling melt profiles of irradiated surfaces of silicon wafers by patterning the nonirradiated side—an approach which could have application when patterning of irradiated surfaces is precluded or less desirable. We find that silicon melt depth displays a gross functional dependence on external silicon dioxide film thickness, and that an oscillatory finely‐structured dependence exists when film thicknesses are varied on the irradiated side of silicon wafers.

Ellipsometric studies of silicon dioxide films on silicon

Ellipsometry is demonstrated to be an appropriate technique for measuring the thickness of silicon dioxide films grown thermally and by an r.f. glow discharge deposition technique in commercial equipment. Optical anisotropy has been observed in thermally grown oxide layers on crystalline (111) and (100) silicon by rotating the samples (in an ellipsometer) about a normal to the sample surface. The degree of anisotropy of films on silicon (111) was found to be dependent on the oxide thickness and decreased to about zero with time at an annealing temperature of 950 °C. The changes in the optical constant produced by rotation increased from 1 × 10 -3 to 8 × 10 -3 with an increase in oxide thickness from 400 to 1000 nm and decreased for thicker films. No anisotropy was observed in thermally grown films or for films deposited by an r.f. glow discharge for thicknesses less than 400nm.