Renato Guida

Laser-induced selective copper deposition on polyimide

Laser irradiation of organometallic palladium compounds with an argon ion laser at 351 nm is used to selectively deposit catalytic amounts of palladium on polyimide. Subsequent immersion of the irradiated samples in an electroless copper solution results in copper deposition. Since a few monolayers of palladium are sufficient to catalyze the electroless copper process, fast writing speeds of several centimeters per second are obtained.

Laser ablation of polymers for high-density interconnect

Abstract Fabrication of micro-vias with a diameter of less than 100 μm in polymeric materials is a key processing technology for high-density interconnect applications. This paper discusses material properties that are relevant to laser ablation and describes several laser techniques (e.g. excimer, UV YAG and CW argon ions lasers) for micro-via fabrication in a thin-film multilayer structure for high-density interconnect applications.

Self-Aligned Single-Mode Polymer Waveguide Interconnections for Efficient Chip-to-Chip Optical Coupling

Single-mode (SM) ultrashort optical interconnections between the fibers and waveguides using self-forming polymeric waveguides with low optical losses at 1300 and 1550 nm were demonstrated. The localized refractive index in the SM regime is estimated by measuring the surface topography induced by monomer diffusion during the waveguide formation. A loss less than -1 dB can be obtained from self-aligning SM-to-multimode (MM) fibers and SM-to-SM fibers interconnections, respectively. A self-formed waveguide-to-fiber interconnection is fabricated and measured with loss less than 0.2 dB at 1550 nm. The polymer waveguide relaxes the positioning requirements for single-mode chip-to-chip optical interconnections, showing great potential to improve the short-term yield and long-term reliability

Photoetching Of Polymers With Excimer Lasers

Photoetching with excimer lasers has been studied in a variety of polymeric materials. Photoetching rates of polymers irradiated were measured at various laser wavelengths and fluences. The relationship of these results to the polymer absorption coefficient is examined. We propose that different mechanisms of photoetching may prevail, which depend on the absorption coefficient of the polymer. Potential use of this dry-etching process for lithography applications is evaluated.

Laser Processing For Interconnect Technology

Laser processing of polyimide dielectric layers for use in high-density interconnect structures was studied. A pulsed excimer laser was used to photoetch via holes and a CW argon ion laser operating at 351 nm was used to selectively deposit catalytic amounts of palladium on polyimide. Subsequent immersion of the irradiated samples in an electroless copper solution resulted in selective copper deposition.

Photonic bandgap fiber enabled Raman detection of nitrogen gas

Raman detection of nitrogen gas is very difficult without a multi-pass arrangement and high laser power. Hollow-core photonic bandgap fibers (HC-PBF) provide an excellent means of concentrating light energy in a very small volume and long interaction path between gas and laser. One particular commercial fiber with a core diameter of 4.9 microns offers losses of about 1dB/m for wavelengths between 510 and 610 nm. If 514nm laser is used for excitation, the entire Raman spectrum up to above 3000 cm-1 will be contained within the transmission band of the fiber. A standard Raman microscope launches mW level 514nm laser light into the PBF and collects backscattered Raman signal exiting the fiber. The resulting spectra of nitrogen gas in air at ambient temperature and pressure exhibit a signal enhancement of about several thousand over what is attainable with the objective in air and no fiber. The design and fabrication of a flow-through cell to hold and align the fiber end allowed the instrument calibration for varying concentrations of nitrogen. The enhancement was also found to be a function of fiber length. Due to the high achieved Raman signal, rotational spectral of nitrogen and oxygen were observed in the PBF for the first time to the best of our knowledge.

Online compositional analysis in coal gasification environment using laser-induced plasma technology

Integrated Gasification Combined Cycle (IGCC) power plants have great potential for future clean-coal power generation. Today, the quality of coal is measured by sampling coal using various offline methods, and the syn-gas composition is determined by taking samples downstream of the gasifier and measured by gas chromatograph (GC). Laser induced plasma technology has demonstrated high sensitivity for elementary detection. The capability of free space transmission and focusing of laser beam makes laser induced plasma a unique technology for online compositional analysis in coal gasification environment and optimization control.

A self-forming compact polymer waveguide for efficient chip-to-chip single-mode interconnection based on radiation mode coupling

Based on radiation mode coupling through a self-formed polymer waveguide extension, efficient single-mode optical coupling can be achieved between the active and passive chips while relaxing the stringent positioning requirements. A 20 dB improvement can be achieved according to simulation results.

Characterization and calibration of Raman based distributed temperature sensing system for 600°C operation

Fiber optic distributed temperature sensing based on Raman scattering of light in optical fibers has become a very attractive solution for distributed temperature sensing (DTS) applications. The Raman scattered signal is independent of strain within the fiber, enabling simple packaging solutions for fiber optic temperature sensors while simultaneously improving accuracy and robustness of temperature measurements due to the lack of strain-induced errors in these measurements. Furthermore, the Raman scattered signal increases in magnitude at higher fiber temperatures, resulting in an improved SNR for high temperature measurements. Most Raman DTS instruments and fiber sensors are designed for operation up to approximately 300˚C. We will present our work in demonstrating high temperature calibration of a Raman DTS system using both Ge doped and pure silica core multi-mode optical fiber. We will demonstrate the tradeoffs involved in using each type of fiber for high temperature measurements. In addition, we will describe the challenges of measuring large temperature ranges (0 – 600˚C) with a single DTS interrogator and will demonstrate the need to customize the interrogator electronics and detector response in order to achieve reliable and repeatable high temperature measurements across a wide temperature range.

Self-Formed Functional Polymer Wires Mimicking Filament Structure in Aquatic Respiration System for Intravascular In-vivo Bio-chemical Sensing

Mimicking filament structure commonly found in aquatic respiration system, we report a self-formed, self-assembled three-dimensional optical waveguide polymer wire suitable to form massive sensing array to enhance bio-chemical sensitivity in intravascular environments.