A significant challenge in the fabrication of thin-film (<1 µm) Au MEMS devices is maintaining planarity after removal of the sacrificial layer. Out-of-plane deformations are driven by residual stress gradients in the Au films. It was found that the baking time and temperature of the sacrificial photoresist layer, as well as the thermal history once the Au was deposited, combined to determine the stress gradient within the Au film. In this technical note we provide the complete details of the optimized procedures to fabricate planar thin-film Au devices with unattached ends that are characterized by low residual stresses.

Micromachined WR 3.4 waveguide circuits are fabricated using a SU-8 micromachining process. In order to demonstrate the viability and repeatability of this process both straight waveguide sections and cylindrical cavity resonators are fabricated and measured. The SU-8 waveguide compares reasonably well to a standard WR 3.4 waveguide section. The measured cavity resonators demonstrate quality factors of 1900 and 2200 at a resonant frequency of 308 GHz.

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Lightweight cement can present unique challenges to efficient and accurate evaluation of cement sheath integrity. Standard bond log tools require strong compressional bonding to casing to observe an attenuation of the sonic signal that is set up inside the casing. Lightweight cement often experiences less cohesion to casing because of its lowered fluid density when pumped and lower compressive strength after being set up. These properties can negatively affect measurement.Definition of the cement sheath must still be determined using a method that is both valid and repeatable. The industry has demonstrated the ability to accomplish this task using ultrasonic logging tools. These devices allow very precise definition of the cement sheath using 360°examination of the data, but still require innovative interpretation techniques to derive useful solutions regarding the isolation capability of the cement.Additional complication is introduced when consolidated efficiency fluid material is pumped as an isolation fluid. This fluid material is lighter weight and has lower compressive strength than even the lightest cements. However, isolation of the reservoirs from surface water and the ability to fracture treat wells with restrained fluid mobility must still be determined.This paper demonstrates the application of ultrasonic cement evaluation tools under these difficult conditions. Examples of conventional cement, lightweight cement, and consolidated efficiency fluid isolation fluids are considered. The processed logs highlight the confidence in the reservoir isolation identified using these tools and evaluation techniques.

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