The decomposition of poly(phthalaldehyde) with a photoacid generator can be used as dry-develop photoresist, where the exposed film depolymerizes into small molecules to allow the development of features via controlled vaporization. Higher temperatures enabled shorter dry-development times, but also promote faster photoacid diffusion that compromised pattern fidelity. Trihexylamine was used as a base quencher to counteract acid diffusion in a phthalaldehyde-propanal co-polymer photoresist. The propanal co-monomer in the polymer improves the vaporization rate because it has a higher vapor pressure than phthalaldehyde. The dry-development of 4μm features was achieved with no appreciable residue.
A photosensitive polyimide system based on amine catalyzed imidization of a precursor poly(amic ester) is described. The material is based on the meta ethyl ester of pyromellitic dianhydride and 2,2’ bis(trifluoromethyl)benzidine. It acts as a negative tone resist when formulated with a photobase generator. The material exhibits a dielectric constant of 3.0 in the gigahertz range, a coefficient of thermal expansion of 6±2 ppm/K, and can be patterned to aspect ratios of >2 when formulated with a highly quantum efficient cinnamide type photobase generator.
A photosensitive polyimide system based on amine catalyzed imidization of a precursor poly(amic ester) is described. The material is based on the meta ethyl ester of pyromellitic dianhydride and 2,2’ bis(trifluoromethyl)benzidine and acts as a negative tone resist when formulated with a photobase generator. The material exhibits a dielectric constant of 3.0 in the GHz range, a coefficient of thermal expansion of 6±2 ppm/K, and can be patterned to aspect ratios of greater than 2 when formulated with a high efficiency cinnamide type photobase generator.
In an effort to address the need for robust optical chip I/O interconnects, we describe the fabrication and testing of
microscopic polymer pillars for use as a flexible optical bridge between the chip and the substrate. The polymer pillars
are photoimaged using the polymer Avatrel to a height of up to 350 &mgr;m. The photodefinable polymer Avatrel was used
for the fabrication of the optical pillars due to its ease of processing and its unique material properties that include high
Tg and low modulus. To evaluate the performance of the polymer pillars, the optical coupling efficiency from a light
source to an optical aperture with and without an optical pillar is measured. For a light source with 12o beam divergence,
a 30x150 &mgr;m polymer pillar improves the coupling efficiency by 3 to 4.5 dB compared to pillar-free (free-space) optical
coupling. Due to the high mechanical compliance of the optical pillars, we also demonstrate that polymer pillars enhance
the optical coupling efficiency between the chip and the substrate when they are misaligned in the lateral direction and
that the displacement tolerance can be doubled from 15 to 30 &mgr;m for a 1dB power loss budget.
A stress gradient was induced in two directions (through the plane of the beam and along its length) to produce a beam deflection of specific curvature. The stress gradient was produced by altering the conditions during electroplating. The pull-down characteristics of four electrostatic actuators were measured. Stressed, hard gold was patterned in a triangular shape on top of stress-free soft gold. This stress gradient along the length of the beams significantly improved the tuning range compared with devices containing spatially uniform stress. The tuning range of the variably stressed gold devices improved by 30 percent for the double-hinged square devices, by 45 percent for the double-hinged elliptical devices, and by 35 percent for the double-hinged rectangular device. Voltage cycling and temperature variation has no significant impact on the pull-down characteristics of the actuator.
Electronic packaging and chip-to-module connections have evolved to meet the needs of electronic systems. The rate of change of the technology will accelerate as the package disappears and optical interconnects come into play. Compliant wafer-scale packaging is an approach which can be used to provide acceptable electrical and mechanical functions for future electronic packaging. In this work, buried air-cavities using sacrificial polymers are used to provide compressible input/output leads.
2D monolithic grating spectrometers for dense wavelength division multiplexing (WDM) show considerable promise to extend the usable bandwidth of optical fibers. Their performance is fundamentally dictated by the grating which is used. First order gratings will theoretically improve the performance of monolithic WDM devices, since WDM devices based on first order gratings do not suffer from an inherent tradeoff between efficiency and broadband operation.
Silicon dioxide films deposited by plasma-enhanced chemical vapor deposition (PECVD) are useful as interlayer dielectric for metal-insulator structures such as MOS integrated circuits and multichip modules. The PECVD for SiO2 in a SiH4/N2O gas mixture yields films with excellent physical properties. However, due to the complex nature of particle dynamics within the plasma, it is difficult to determine the exact nature of the relationship between film properties and controllable deposition conditions. Previous modeling techniques such as first principles or statistical response surface methods are limited in either efficiency or accuracy. In this study, PECVD modeling using neural networks has been introduced. Neural networks have been shown to exhibit superior performance in both accuracy and prediction capability compared to statistical models.
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