Atomic force microscopy (AFM) has been widely used for creating nanoscale oxide lines on various material surfaces. The assembling technique used for overlapping an array of these oxide lines into a uniform oxide layer is analytically investigated and experimentally verified. The experimental data of the oxide lines induced at different scanning speeds are analytically correlated to provide the basic formula for the assembling technique. The superposition principle is then applied for simulating the assembling process to extract the criteria for assembling a uniform layer. Experiments have been conducted to verify the reliability of the uniformity criteria analytically obtained and the feasibility of the assembling technique developed. Indeed, a uniform oxide layer can be precisely assembled by following the uniformity criteria developed.
The reliability in the wafer bonding is highly dependent on the surface conditions present on each individual wafer. An emerging wafer bonding technique, referred to as transmission laser bonding (TLB), is examined and implemented for the bonding of Pyrex glass-to-silicon wafers using a solid-state pulsed neodymium: yttrium aluminum garnet (Nd:YAG) laser. Focusing specifically on the physical attributes of surface roughness and contact pressures, we explore their relative effects on the associated bond strength. The bonding strengths of the TLB bonded specimens are quantified using a microtensile tester, whereas the surface roughness and flatness are determined by atomic force microscopy and profilometry, respectively. The tensile results indicate that with appropriate surface roughness and contact pressure, the bond strength obtained is comparable with, if not better than, those using conventional wafer bonding techniques. Both the x-ray photoelectron spectroscopy and Auger electron spectroscopy are used to facilitate the study of the bonding mechanism of the delaminated surfaces of TLB specimens by evaluating the migration and diffusion of different atoms across the bonding interface. A thermal penetration analysis is also provided to validate the findings of the bond strength and the spectroscopic evaluations.
KEYWORDS: Electron beam lithography, Near field optics, Glasses, Coating, Computer aided design, Germanium, Near field, Photoresist processing, Polymethylmethacrylate, Diffraction
The development of microbowtie structures for a next-generation optical probe called the Wave Interrogated Near-Field Array (WINFA) is presented. The WINFA combines the sensitivity of near-field detection with the speed of optical scanning. The microbowties are designed to act as resonant elements to provide spatial resolution well below the diffraction limit with a transmission efficiency approaching unity. Following an introduction of the concept and background information, the design of the microbowtie is presented. A numerical electromagnetic scattering model is developed and used for better designs of the bowtie structures. The electron-beam lithography process is then used to fabricate the final designed bowties structure. Special fabrication procedures have been developed to cope with the charge dissipation problem that arises when lithographing an insulating substrate as is required in the present probe design. Two types of substrates and two types of resists are considered in the present study. The fabricated microstructures have 40 nm bowtie gaps that are more than 200 000 times smaller than the one built previously. All fabricated bowtie microstructures are examined and the results are compared. It has been found that, in addition to the relative ease in fabrication, the bowties on indium-tin-oxide coated glass substrate can not only minimize the charge accumulation in a glass substrate, but also satisfy the functional requirement of optical transparency to the incident wave. Recommendations for making a bowtie structure in the even smaller bowtie array are also included.
KEYWORDS: Near field optics, Glasses, Computer aided design, Electron beam lithography, Lithography, Coating, Electron beams, Scattering, Near field, Inspection
A microbowtie array critical to a newly developed optical probe is studied. The optical probe is used for high speed detection of nanoscale objects. Based on the concept of Wave Interrogated Near Field Array, an array of microbowtie structures is acting as a detector in amplifying the incident light source to overcome the difficulties of the conventional optical probe that are limited by the diffraction limits of the optical light. In the present study, the micro bowties are fabricated by an electron beam lithography technique. The paper begins with an introduction of the probe concept and then the design considerations are given followed by the details of the fabrication procedure. Two different substrates are considered to study the charge accumulation problem caused by an insulating substrate required by the probe. The effect of the charge accumulation on the fabrication procedures is specifically discussed. Results indicate that the bowtie structure with an indium- tin-oxide coated glass substrate can minimize the charge accumulation problem, making it one of the most suitable substrates for the bowtie structures considered. The paper concludes with recommendations for making even smaller nano- sized bowtie structures.
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