Commercial Silicon Wafers Research Articles

Influence of storage time on laser cleaning of SiO 2 on Si

The influence of the ‘storage time’ τs on the threshold fluence φcl and the efficiency in dry laser cleaning is investigated. τs denotes the time between the deposition of particles and the cleaning. As a model system we employed silica spheres with diameters of 500 nm and 1500 nm on commercial silicon wafers and single-pulse KrF excimer laser radiation (τFWHM=28 ns). For the 1500-nm silica spheres, φcl was found to increase from about 65 mJ/cm2 to 125 mJ/cm2 for storage times of 4 h and 362 h, respectively. For 500-nm silica spheres the increase in the threshold fluence was less than 20% for storage times up to 386 h.

Position-sensitive analysis in curved-crystal three-axis neutron spectrometry (quasielastic scattering case)

The use of bent perfect crystals in focusing three-axis neutron spectrometry with position-sensitive detection (PSD) is analyzed on the basis of a phase-space theory. With PSD, the usual sequential scans are replaced by simultaneous scans. The case of high resolution in energy transfer is considered in detail. With commercial thin silicon wafers, the achievable resolutions are in the 10–150 µeV range, depending on neutron energy. Resolutions around 10 µeV are obtained on the peak of cold-source spectra. To take advantage of the possibilities offered by silicon wafers, PSD with spatial resolution well below 1 mm will be needed. With PSD analysis, a new kind of focusing exists that allows the thickness of bent perfect analyzer crystals to be increased, providing an intensity gain at no resolution loss. With multilamella assemblies a gain in count rate by the number of lamellae in the packet is achievable. Results of a demonstration experiment are presented, confirming that under the right conditions, a multilamella analyzer may resemble a single bent wafer, the individual curves of many wafers having been combined to provide the intensity gain.

The Effect of the Nucleation Temperature on the Variation of the Microstructure of Czochralski Silicon after Two‐and Three‐Step Anneals

Two‐step and three‐step anneals were applied systematically to a set of commercial Czochralski silicon wafers. The microdefects generated during the anneals were decorated with Wright etchant and investigated by optical microscopy. The types of microdefect generated were observed to vary with the time and temperatures of the nucleation anneal. The observations provide very useful information relevant to the control of microdefects in Czochralski silicon to improve the gettering efficiency. © 1999 The Electrochemical Society. All rights reserved.

Second-order neutron optics of three-axis spectrometers. I. Quasielastic scattering

The basics of second-order neutron optics for bent-crystal three-axis spectrometers are presented. Energy-transfer resolution for quasielastic scattering is examined in detail. Experimental data illustrating the effect of second-order aberrations are presented. The resolution of energy transfer at 5 meV neutron energy with bent monochromators made from commercial thin silicon wafers was improved to 8 µeV from a previous record of 16 µeV.

High resolution neutron scattering with bent monochromators made of commercial silicon wafers

Commercial thin silicon wafers are shown to be superb focusing crystals in three-axis spectrometers. With fully open beams, they allow resolutions that in conventional flat-crystal arrangements can only be achieved with Soller collimators of 2 min of

High-resolution neutron scattering with commercial thin silicon wafers as focusing monochromators

Quasielastic scattering measurements with commercial silicon wafers as focusing monochromator and analyzer in a three-axis spectrometer showed energy-transfer resolutions in the 10–100 μeV range (fwhm). Resolutions were better and intensities higher than in a conventional arrangement with Soller collimators and pyrolytic graphite (PG) monochromator and analyzer. Resolution remained high when extended-plate samples were used in focusing orientation. At cold sources, this technique would give 10–20 μeV resolutions at neutron energies near the peak of the spectrum. Projections of resolution ellipsoids were determined by diffraction from powder samples. The orientations of the ellipsoids are controlled by horizontal curvatures and can be rotated 90° for Q-resolution. A monochromator unit with remote control of horizontal curvature and fixed vertical curvature set to spatial focusing at the sample position was also tested. The strong vertical focusing gave a significant gain in integrated intensities, but worsened the resolution because of second-order aberrations.

Adsorption and growth of dip-coating prepolymer films on silicon wafers. An atomic force microscope study

Ultrathin films of a prepolymer of the dicyanate of bisphenole A were made by dip-coating on commercial silicon wafers. The initial stages of film formation could be characterized in detail by AFM (atomic force microscopy) in the tapping mode and in a newly developed deformation mapping mode. The interpretation is assisted by simple molecular modelling as well as surface analytical investigations. The thinnest films are discontinuous and have a mean thickness <1 nm (ellipsometry). They consist primarily of an amorphous deformable phase which probably represents monomer. Even for the tiny roughness of the wafers (0.13 nm RMS), the initial adsorption is preferred in substrate depressions. High resolution imaging could be reproducibly achieved even for this amorphous film surface. An extended contact time of the wafer with the prepolymer solution induces the adsorption of adsorbates, whose heights correspond to the next larger species of the prepolymer, the trimer. Further increase in contact time results in a close packing of these adsorbates and such with double the height. After a contact time of about one minute, a steady state of the film morphology is reached. Then, the mean film thickness can only be raised by increasing the concentration of the solution. In addition, all films comprise large prepolymer agglomerates which represent conglomerates already present in the solution above a small, critical concentration.

Observation of hydrogen in commercial Czochralski-grown silicon wafers

Commercially available, Czochralski-grown (CZ), phosphorus- and boron-doped (100) silicon wafers have been characterized by capacitance-voltage and deep-level transient spectroscopy measurements of Schottky diodes. Two electron traps labelled A1 (Ec-0.10 eV) and A2 (Ec-0.13 eV) are commonly observed in n-type wafers with a concentration around 1011 cm-3. These correspond to the hydrogen-related complexes previously reported. A decrease of carrier concentration occurs near the surface in p-type wafers. This is ascribed to the passivation of boron acceptors by hydrogen. These results indicate that hydrogen is incorporated near the surface in commercial CZ silicon wafers.

The correction of geometrical factors in the analysis of X-ray reflectivity

X-ray reflectivity is a powerful technique to study electron density profiles in the direction normal to the surface of a fiat sample. As usual in scattering experiments, where the phase information is lost, it is necessary to build a model that can be used to calculate the reflectivity for comparison with the measured reflectivity. In the calculations, it is necessary to correct the calculated reflectivity from geometrical and resolution-function factors, which play a major role at low angles of incidence. These factors are presented in this paper and the corrected calculated intensity is compared with the measured reflectivity of a commercial silicon wafer and of a niobium film on a sapphire substrate.

On the Hydrogen Content of Commercial Silicon Wafers

We have characterized a series of commercially available p‐type silicon wafers using Schottky barrier capacitance voltage and spreading resistance measurements. A high resistivity near surface (∼1 μm) region is systematically observed, which can be annealed out by heating the material above ∼200°C. Hydrogen neutralization of boron acceptors has been identified as the cause of this phenomenon. Atomic hydrogen is believed to be incorporated in the material during polishing.

A Chemical/Microwave Technique for the Measurement of Bulk Minority Carrier Lifetime in Silicon Wafers

A chemical/microwave technique for the measurement of bulk minority carrier lifetime in silicon wafers is described. This method consists of a wet chemical treatment (surface cleaning, oxidation in solution, and measurement in solution) to passivate the silicon surfaces, a laser diode array for carrier excitation, and a microwave bridge measuring system which is more sensitive than the microwave systems used previously for lifetime measurement. Representative experimental data are presented to demonstrate this technique. The result reveals that this method is useful for the determination of bulk lifetime of commercial silicon wafers.