Single Crystal Silicon Wafers Research Articles

A Vibration Resistant Nanopositioner for Mobile Parallel-Probe Storage Applications

We describe a planar microelectromechanical systems (MEMS)-based x/y nanopositioner designed for parallel-probe storage applications. The nanopositioner is actuated electromagnetically and has x/y motion capabilities of plusmn60 mum. The mechanical components are fabricated from a single-crystal silicon wafer using a deep-trench-etching process. To render the system robust against vibration, we utilize a mass-balancing concept that makes the system stiff against linear shock, but still compliant for actuation, and therefore results in low power consumption. We present details of the finite-element model used to design the device as well as experimental results for the frequency response, actuation, and vibration-rejection properties of the nanopositioner

Characteristics of mask layer on (100) silicon induced by tribo-nanolithography with diamond tip cantilevers based on AFM

Abstract Nanoscale fabrication of silicon substrate based on the use of atomic force microscopy (AFM) followed by chemical etching was demonstrated. A specially designed cantilever with a diamond tip, allowing the formation of damaged layer on silicon substrate by a simple scratching process, has been applied instead of conventional silicon cantilever for scanning. A thin damaged layer forms in the substrate at the diamond tip–sample junction along scanning path of the tip, which was found to be a low crystallized amorphous silicon layer. Hence, these sequential processes, called tribo-nanolithography, TNL, can fabricate 2D or 3D microstructures in nanometer range. Diamond tip fabrication processes for TNL follow the micro-patterning, wet chemical etching and CVD based on MEMS processes. The developed TNL tools show outstanding machinability against single crystal silicon wafer. Hence, they are expected to have a possibility for industrial applications as a micro-to-nano-machining tool. In our previous work, is has been clearly known that the damaged layer withstands against aqueous potassium hydroxide solution, while it dissolves in diluted hydro fluoric solution. This study demonstrates the effect of various machining parameters on mask layer, followed by wet chemical etching in potassium hydroxide and hydro fluoric solution.

The development of a wire saw for wafer slicing of single-crystal silicon

Most Integrated Circuit (IC) chips are built on single-crystal silicon wafers. The typical manufacturing process for silicon wafer includes: slicing, lapping or grinding and polishing, etc. The wafer slicing is a key technology that has influence on chip quality and cost. In this paper, the principle and characteristics of inner diameter saw and wire saw are summarised; a looped wire saw is developed. It uses fixed abrasive diamond looped wire that moves continually, which reduces or eliminates the influence on wafer surface accuracy for change in speed. This wire saw can provide a continuous speed range though electrical drive. Silicon bar is fixed on the worktable by a special fixture. The wire saw has two kinds feeding fashion. Some measures in design, machining and assembling are adopted to reduce the amplitude of wire vibration and to improve wafer-slicing quality. It is proved that this wire saw is excellent at wafer slicing, safe in prevention and convenient in operation.

Oxidation of thin films of zirconium and Zr-Ti solid solutions on single-crystal silicon

We have studied the oxidation of thin films of zirconium and Zr-Ti (1.2–2.03 at % Ti) solid solutions produced on single-crystal silicon wafers by magnetron sputtering. The films have been oxidized in flowing oxygen at temperatures from 473 to 673 K in a resistance furnace. The phase composition of the resultant oxide layers has been determined. Our results indicate that the oxidation kinetics of thin-film zirconium and Zr-based solid solutions are well represented by a linear-parabolic rate law. The composition, structure, and optical constants of the oxide layers depend on the heat-treatment conditions and the titanium content of the films.

Gas Pressure Sensor Based on PECVD Grown Carbon Nanotubes

AbstractIn present paper we describe development and manufacturing of the pressure sensor based on electron field emission from carbon nanotubes (CNTs). The sensor consisted of two parts, silicon membrane as an anode and multiwalled CNTs on a silicon cathode, creating a vacuum micro-chamber. Both electrodes were fabricated from the silicon single crystal (Si) wafer of the orientation (<100>) doped by phosphorus. The CNTs were grown by plasma enhanced CVD using iron catalyst in atmospheric pressure microwave torch. The catalyst was patterned into the area corresponding to the membrane dimensions. The thin CNTs with the diameter about 80 nm were straight standing perpendicularly to the substrate due to a crowding effect. In order to find the threshold current the emission characteristics of prepared sensors were measured.

７０ｍｍコンフラットフランジマウント型加熱冷却機構付きシリコン単結晶ホルダー

We introduce a silicon single crystal wafer holder with a cold trap and a direct current heating mechanism mounted on a conflat flange with an outer diameter of 70 mm. It consists of 300-ml cold trap, tantalum electrodes for direct-current heating and commercial electrical feedthroughs. A silicon single crystal with a size of 30×5×0.5 mm can be heated to >1100 °C by direct heating, and can be cooled down to <100 K with liquid nitrogen.

Platelet activation behavior on nitrogen plasma-implanted silicon

To enhance the surface biocompatibility of silicon-based materials used in micro-biomedical devices, nitrogen plasma immersion ion implantation (PIII) was performed on single-crystal silicon wafers. The platelet activation behavior on the N-PIII silicon was investigated in vitro, and the results indicate that the nitrogen plasma-treated surface exhibits less platelets activation than low temperature isotropic pyrolytic carbon (LTIC) that is a common material used in blood-contacting implants such as artificial heart valves. Our results also indicate that Si–N bonds enhance the surface hydrophilicity and combined with good critical surface tension, activation of platelets is mitigated. The mechanism of the platelet activation reactions is discussed from the perspective of the surface energy.

Hybrid nanocomposite of Fe nanoparticles on SiO 2 nanowires by sublimation route

A simple route was developed to synthesize the hybrid nanocomposite with Fe nanoparticles (NPs) dispersed on the surface of SiO 2 nanowires (NWs), where SiO 2 NWs with the diameter of 20–40 nm were produced by heating single-crystal silicon wafer, and Fe NPs in the size range of 3–20 nm were generated by heating Fe powders. The nucleation and growth of Fe NPs follows the solid–vapor–solid (S–V–S) mechanism, namely, Fe powders firstly sublime and then Fe atoms deposit on SiO 2 NWs to form Fe NPs.

Anodic bonding of silicon onto glass by ion-cut technique and their characterization using high resolution X-ray diffraction studies

Anodic bonding of single crystal silicon wafer with glass and subsequent splitting of the silicon wafer is done by ion-cut technique that involves proton bombardment at desired energies at a dose level > 5 × 10 16 cm − 2 and then subjected to the bond pair for heat treatment at ∼ 550 °C. Details of the bonding and splitting processes have been discussed in the present study. The high resolution X-ray diffractometry studies have been performed and found that transferred single crystalline thin silicon layer has less crystalline perfection than the original wafer. It suggests that some improvement is still required in the ion-cut technique to improve the crystalline quality of the transferred layer before going to be used for the device applications.

Direct synthesis of SiC nanowires by multiple reaction VS growth

β-SiC nanowires were directly synthesized by heating single-crystal silicon wafer and graphite without metal catalysts. The diameter of SiC nanowires is in the range of 10–30 nm, and the length is up to a few millimeters. Two kinds of SiC nanowires, namely pure SiC nanowires and SiC/SiO 2 composite nanowires, formed at higher temperature (the holding stage) and lower temperature (the cooling stage), respectively. A multiple-reaction model was proposed to explain the formation of SiC nanowires.

Melting and crystallization dynamics of single-crystal silicon exposed to compression plasma flows

The melting and crystallization of single-crystal silicon wafers exposed to compression plasma flows generated by quasi-stationary plasma accelerators are studied by numerical simulation. The results include the phase transition kinetics described on the basis of the Kolmogorov equation. The space-time characteristics of the melting and crystallization processes for variously shaped plasma pulses are discussed. Based on the experimental data and estimates, it is concluded that thermoelectric instability plays an essential role in the formation of three-dimensional periodic structures.

Structure and physical properties of nickel films deposited by microwave plasma-assisted cathodic sputtering

Nanocrystalline nickel films have been deposited by microwave plasma-assisted sputtering from pure argon discharges on steel and (100)-oriented single crystal silicon wafers mounted on a water-cooled substrate holder biased to various direct current voltages ranging from 0 to −120 V. The crystallographic structure and surface morphology of films were determined by x-ray diffraction techniques and atomic force microscopy, respectively. The magnitude of compressive residual stresses (intrinsic stress) calculated from the radius of curvature of Si substrates reached a maximum value of −250 MPa in films deposited on grounded substrates and decreased with increasing negative substrate bias voltage. The hardness of films was determined by nanoindentation as a function of the substrate bias voltage. Alumina ball-on-disk tribological tests of films deposited on steel substrates were conducted in room air at 20 °C under a load of 1 N with a sliding speed of 50 mm s−1. The value of the stabilized friction coefficient was in the range 0.35–0.45 for 5000 cycles. Beyond 5000 cycles, the films were worn and the friction coefficient increased rapidly. The electrical resistivity of films deduced from the thickness and sheet resistance of films determined by four point probe measurements was approximately equal to 13 µΩ cm.

Micromechanical properties of hydrogenated diamond-like carbon multilayers

Hydrogenated diamond-like carbon (H:DLC) coatings including monolayer and multilayers were prepared on single crystal silicon (100) wafers by an RF plasma enhanced chemical vapour deposition (PE-CVD) system. The system has two coating zones A and B where the deposition process and the thickness of each layer can be easily controlled. A nano hardness tester was used to measure hardness and reduced elastic modulus of the coatings, and a nano scratch tester was used to estimate adhesion properties and friction behaviors of the coatings. The result shows that the amorphous carbon multilayers with A(10 Å)/B(4 Å) developed the best micromechanical properties among all the samples.

Tribological properties of chemically bonded polyimide films on silicon with polyglycidyl methacrylate brush as adhesive layer

Polyimide thin films, which possess good stability and film uniformity, are successfully fabricated on single crystal silicon wafers coated with a thin polymer brush by suface-initiated polymerization (SIP) as an adhesive layer. The growth kinetic of polyglycidyl methacrylate (PGMA) brush was studied by the means of ellipsometry. The nano-scale morphology and chemical composition of PGMA brush and polyimide film were studied with atomic force microscopy (AFM), Fourier transform infrared spectrum (FT-IR), and X-ray photoelectron spectroscopy (XPS). The tribological behaviors of the thin films sliding against AISI-52100 steel ball were examined on a static-dynamic friction precision measurement apparatus and UMT-2MT tribometer. The worn surface of the polyimide thin films was investigated with scanning electron microscopy (SEM). The results indicated that the chemically bonded polyimide films exhibited better friction reduction and antiwear behavior compared to the polymide films on bare silicon surface. At a load of 0.5N and sliding speed of 20mms−1, the durability life of the polyimide thin films is over 25,000 sliding cycles and the friction coefficient is about 0.08.

Micro channel forming with ultra thin metallic foil by cold isostatic pressing

The objective of this study is to establish the limit of the metal forming process in terms of size and accuracy. In the present investigation, micro channel forming with ultra thin metallic foil by the sheet metal forming process was studied. In order to examine the fabrication limit of the process, both the channel size needed to be as small as possible and the sheet thickness to be as thin as possible. Copper foil 1.0 μm thick was made into 5.6 μm wide and 3.2 μm deep channels. The shapes of the channels were straight line, concentric circle, cross, and other curved shapes. Forming was done by cold isostatic pressing. Single crystal silicon wafer was used as the die material, and die grooves were made by micro machining techniques. The die, metallic foil, and plasticine as the pressure-transmitting medium were vacuum packed in a bag made of multilayered film. The forming was conducted with a cold hydrostatic press where the forming pressure was 240 MPa. The formed channels were examined in terms of their dimensions and surface qualities. Based on the examinations, channel formability was also discussed.

MEMS-based combustor with hairpin-shape design of gas recirculation channel

This paper describes the design, fabrication and test of a silicon-based micro combustor, which is a part of a micro power generation system under development. Based on the three-dimensional computational fluid dynamics (CFD) simulation and analysis of different micro combustor design, a hairpin-shape design for air/fuel recirculation channel is adopted. The combustor is fabricated from seven single crystal silicon wafers using deep reactive ion etching (DRIE) process. It has been assembled successfully with gas tubing and thermal couplers for monitoring the exit gas temperature. The effect of mass flow rate on the combustion characteristics is studied experimentally and numerically under several operating conditions. The exhaust gas temperature can reach the range from 870 to 1,100 K. The results indicate that with the increases of the mass flow rate, the combustor exhaust gas temperature increase as well in both experimental and the simulated results. This is due to the heat released in the combustor increases with the fuel/air mass flow rate.

Load effects on the phase transformation of single-crystal silicon during nanoindentation tests

Depth-sensing nanoindentation tests were made on single-crystal silicon wafers at various loads using a sharp Berkovich indenter, and the resulting indents were studied using transmission electron microscope and selected area diffraction techniques. The results indicated that the shape of the unloading parts of the load–displacement curves was affected by indentation load. The geometry and the size of the phase transformation region were also dependent on the indentation load. A strong correlation between the indentation load and the microstructure change of silicon was confirmed. A small load (∼20 mN) leads to a complete amorphous indent after unloading, whereas a big load (∼50 mN) produces a mixture of amorphous and nano-crystalline structure around the indent. The critical load for this transition to occur was approximately 30 mN. These results provide information for ductile regime machining technologies of silicon parts.

Real-Time and Full-Field Deflection Measurement of Thin Films Electroplated on the Single Crystal Silicon Wafers

A special speckle microinterferometer has been developed to test the mechanical properties of thin films electroplated on the single crystal silicon wafer. A piezo-actuated micro-loading unit is synchronized with the microinterfermeter to measure thin film deflection in bending with an accuracy of sub-micrometers. All of the film specimens were microfabricated to be the type of microbridge samples. They are made of Cu and NiFe, the sizes from 1102.9µm to 213.7µm long, 491.0µm to 9.7µm wide. The corresponding thicknesses are 9.4µm and 7.6µm, respectively. Deflections of the microbradge samples can be measured full-field and real-time by using the microinterferometer and no patterning or marking of the specimen surface is needed. The loading force is directly measured using a miniature load cell. The Young’s moduli are calculated for both material and sample size from the load-deflection curves. Test techniques, procedures and factors which affect on the deflection measurements are briefly presented along with detailed analyzes of the results.

The mechanism of formation and properties of stratified-inhomogeneity defects in silicon

The mechanism of formation and properties of stratified-inhomogeneity defects in single-crystal and epitaxial silicon wafers are studied using currently available investigation methods. The mechanism of formation of these defects is found to be due to the layered structure of silicon wafers. The type of defects and conditions of impurity precipitation are determined.

Resonance ultrasonic vibration diagnostics of elastic stress in full-size silicon wafers

A resonance vibration approach is developed to measure residual stress non-destructively in full-size multicrystalline silicon wafers used in solar cell manufacturing. This method is based on excitation of longitudinal resonance ultrasonic vibrations in the material using an external piezoelectric transducer combined with high-sensitive ultrasonic probe and data acquisition of the frequency response to make the method suitable for in-line diagnostics during wafer and cell manufacturing. Theoretical and experimental analysis of the vibration mode in single-crystal and multicrystalline silicon wafers is used to provide a benchmark reference analysis and validation of the approach.