Laser Induced Desorption Time of Flight Mass Spectrometer Analysis of Adsorbed Contaminants on Vacuum Ultraviolet Lithography Optic Materials

Adsorbed surface contaminants on optical elements absorb light energy in an optical lithography system and, if left unclean, will result in reduced wafer yield. In order to nondestructively analyze the surface adsorbate of different CaF2 samples, a laser induced desorption-Time of Flight Mass Spectrometer (LID-TOFMS) technique was developed. The main object of this technique is to investigate the surface composition of adsorbed contaminants as a function of position on the sample. An Er:YAG laser at 2.94 μm was used as the light source to induce desorption. Electron impact ionization was used to obtain ionization of desorbed molecules. The detection of ionized species was accomplished by TOFMS operated in Angular Reflectron (AREF) mode to obtain better resolution. The data reported here can be used in semiconductor industries either to modify conventional processing or to design a new efficient laser cleaning process for optical elements

Apparatus and Method of Fabricating Directional Fiber Optic Taps, Sensors and Other Devices with Variable Angle Output

An apparatus and method for fabricating directional fiber optic taps having a variety of output angles. The taps can be used to monitor losses due to misalignment of the fiber or losses due to bending and straining of the fiber. The apparatus and method can also be used to fabricate taps which filter out higher order modes in a fiber. The apparatus and method can also be used to produce taps which can be used in a position or refractive index measuring system

Method for Producing Conductive or Insulating Feedthroughs in a Substrate

A method for producing feedthroughs in a substrate having a front and back surface, wherein the substrate either has a hole or absorbs radiation at a given wavelength. The method includes selecting and intimately bonding a sheet to the back surface of the substrate with an adhesive which is absorptive at the given wavelength. If the substrate has a hole, an exposed area of the sheet is illuminated with laser radiation at the given wavelength and at a power level sufficient to ablate a portion of the sheet behind the exposed area, thereby creating the feedthrough in the substrate. If the substrate has no hole, an area on the front surface of the substrate is illuminated with laser radiation at the given wavelength and at a power level sufficient to ablate a portion of the substrate and a portion of the sheet behind the area, thereby creating the feedthrough in the substrate. The sheet can then be removed from the substrate. Alternatively, if the sheet is conductive, the sheet can remain bonded to the substrate and can serve as a ground plane for the substrate. If the sheet is an insulator, the feedthrough is an insulated feedthrough and if the sheet is conductive, the feedthrough is a conductive feedthrough. This procedure can be extended to produce a two conductor feedthrough

Use of Case Studies to Promote Critical Thinking in Occupational Therapy Students

Critical thinking is a necessary component of clinical reasoning that should be addressed as part of the graduate curriculum for occupational therapists. For students to apply critical thinking in practice they must also have confidence and minimal anxiety about their abilities. Case-based learning was chosen to address critical thinking skill development, increase confidence, and decrease anxiety. The purpose of this mixed methods pilot study was to evaluate progressively independent engagement with case-based learning on student performance, confidence, and anxiety in applying critical thinking skills in the clinical setting. Critical thinking was measured using a rubric to assess students’ performance in analyzing the case studies with decreasing levels of instructor guidance over the semester. Confidence and anxiety levels were measured using a Likert confidence and anxiety scale at the start and end of the semester. Qualitative data was collected through telephone interviews to determine ways in which classroom activities translated to a clinical setting and to elicit student feedback about the lesson design and what they felt they learned in class after the first Level II fieldwork. All three areas of critical thinking, confidence, and anxiety improved, demonstrating a significance of

Photoacoustic Study of KrF Laser Heating of Si: Implications for Laser Particle Removal

A photoacoustic study of KrF laser heating of Si has revealed that the dominant mechanism of acoustic generation is thermoacoustic with a considerable contribution from the concentration-deformation mechanism at laser fluences below the Si melting threshold of 0.5 J/cm 2. Upon Si melting the contraction of the molten material contributes significantly to acoustic generation. At fluences above 1.4 J/cm 2 laser ablation of the molten layer enhances the amplitude of the compression pulse and diminishes that of the rarefaction pulse. The results of photoacoustic measurements allow optimization of experimental conditions for dry laser particle removal. © 2002 American Institute of Physics

Laser-Assisted Fabrication of NMR Resonators

A detection coil for use in nuclear resonance magnetic (NMR) spectroscopy and a method of manufacture thereof. At least two film layers of material are deposited on an outer surface of a cylindrical tube of dielectric material. The layers are patterned to form a solenoid on the tube. At least one of the deposited materials is a conductor

Removal Versus Ablation in KrF Dry Laser Cleaning of Polystyrene Particles from Silicon

Direct absorption and melting of 0.2, 0.5 and 1.1 μm polystyrene particles on a Si substrate irradiated by 248 nm excimer laser radiation was found to contribute to their dry laser removal via a hopping mechanism at cleaning thresholds of 0.05, 0.1, and 0.16 J/cm 2, respectively. Ablation of these particles, which starts near the beginning of substrate deceleration at fluences above 0.4-0.5 J/cm 2, suppresses particle removal due to ablative recoil momentum. At fluences above a second cleaning threshold of 0.7 J/cm 2 particles are completely evaporated without any visible surface damage of the Si substrate. © 2002 American Institute of Physics

Optical Transmission Measurements of Explosive Boiling and Liftoff of a Layer of Micron-Scale Water Droplets from a KrF Laser-Heated Si Substrate

Water plume velocities were measured in air by optical transmission as a function of laser fluence using a KrF laser for explosive boiling and liftoff of a layer of micron-scale waterdroplets from a laser-heated Si substrate of interest for laser particle removal. The thickness of the superheated water layer near the water/Si interface determines acceleration and removal of the waterdroplets from the Si substrate. © 2003 American Institute of Physic

Analysis of Adsorbed Contaminants of CaF/sub 2/ Surfaces by Infrared Laser Induced Desorption

157 nm photolithography technologies are currently under development and have been accepted as the leading candidate for fabrication of the next generation semiconductor devices after 193 nm. At this and shorter wavelengths, molecular contamination of surfaces becomes a serious problem as almost all molecules absorb at 157 nm and below. The light transmitted by a photolithographic tool can be significantly decreased by the presence of a few monolayers adsorbed on its many optical surfaces. We have developed a laser induced desorption, electron impact ionization, time-of-flight mass spectrometer (LID TOFMS) to study contaminants on 157nm and other ultraviolet optics, e.g., polished CaF2. The LID TOFMS of CaF2(100) samples showed water ions, hydrocarbon ions, oxygen-containing hydrocarbon ions, as well as alkali metal ions (Na+,K+). For multiple irradiations of one site at fixed laser fluence, the ion intensities decreased as the number of pulses increased, suggesting that surface contaminants were being removed. A degenerate threshold model that assumes preferential adsorption at surface defects was employed to quantitatively analyze the LID data. Desorption thresholds for water and hydrocarbons were obtained from this model. © 2004 American Vacuum Societ