Al(2)O(3) and TiO(2) atomic layer deposition (ALD) were employed to develop an ultrathin barrier film on copper to prevent water corrosion. The strategy was to utilize Al(2)O(3) ALD as a pinhole-free barrier and to protect the Al(2)O(3) ALD using TiO(2) ALD. An initial set of experiments was performed at 177 °C to establish that Al(2)O(3) ALD could nucleate on copper and produce a high-quality Al(2)O(3) film. In situ quartz crystal microbalance (QCM) measurements verified that Al(2)O(3) ALD nucleated and grew efficiently on copper-plated quartz crystals at 177 °C using trimethylaluminum (TMA) and water as the reactants. An electroplating technique also established that the Al(2)O(3) ALD films had a low defect density. A second set of experiments was performed for ALD at 120 °C to study the ability of ALD films to prevent copper corrosion. These experiments revealed that an Al(2)O(3) ALD film alone was insufficient to prevent copper corrosion because of the dissolution of the Al(2)O(3) film in water. Subsequently, TiO(2) ALD was explored on copper at 120 °C using TiCl(4) and water as the reactants. The resulting TiO(2) films also did not prevent the water corrosion of copper. Fortunately, Al(2)O(3) films with a TiO(2) capping layer were much more resilient to dissolution in water and prevented the water corrosion of copper. Optical microscopy images revealed that TiO(2) capping layers as thin as 200 Å on Al(2)O(3) adhesion layers could prevent copper corrosion in water at 90 °C for ~80 days. In contrast, the copper corroded almost immediately in water at 90 °C for Al(2)O(3) and ZnO films by themselves on copper. Ellipsometer measurements revealed that Al(2)O(3) films with a thickness of ~200 Å and ZnO films with a thickness of ~250 Å dissolved in water at 90 °C in ~10 days. In contrast, the ellipsometer measurements confirmed that the TiO(2) capping layers with thicknesses of ~200 Å on the Al(2)O(3) adhesion layers protected the copper for ~80 days in water at 90 °C. The TiO(2) ALD coatings were also hydrophilic and facilitated H(2)O wetting to copper wire mesh substrates.

We report the first use of a bimetallic buckling disk as a thermal conduction switch. The disk is used to passively alter the thermal resistance of the package of a chip scale atomic clock. A vertical-cavity surface-emitting laser and a cesium vapor cell, contained in the clock, must be maintained at 70±0.1°C even under an ambient temperature variation of −40°Cto50°C. A thermal test vehicle has been developed to characterize a sample package with a thermal conduction switch. Three cases are presented for the temperature control of the test vehicle under different load placements and environmental conditions: (1) a heating load with a good conduction path to the switch in a vacuum package; (2) the same loading as in Case 1, but packaged in air; and (3) a heating load insulated from the switch, in a vacuum package. At 38°C, the switch snaps upward to reduce the package’s thermal resistance. As a result, the heating power needed to maintain a constant temperature, 63.9±0.1°C, is increased from 118to200mW for Case 1. Such a significant change of the thermal resistance demonstrates the effectiveness of the thermal switch. However, the switch becomes less effective with air filling the gap, as in Case 2, and the switch is not effective at all if the heating load does not have a good conduction path to the switch as in Case 3. The steady state response of this novel thermal conduction switch has been well characterized through experimentation and finite element analysis.

Lenslet integrated Micro-Electro-Mechanical Deformable Micromirrors (LMEM-DMs) are electrostatic micromirror arrays fabricated through a commercial surface micromachining process and integrated with polymer or glass microlenses. The electronics resins (Photo-BCB) which are photo-sensitive polymers were used to fabricate polymer microlens arrays. A 4 x 4 element photo-BCB Cyclotene microlens array was fabricated on a thin quartz substrate. Self-aligned soldering flip-chip assembly is applied to integrate microlens arrays directly over the micromirrors. The lens/mirror gap is controlled using the final height of solder balls, and the lateral alignment is achieved by the solder self-aligning mechanism. The LMEM-DM is attractive due to its low cost and the low drive voltages. The use of a lenslet to focus the incoming laser beam onto the reflective surface of a micromirror substantially increases overall optical fill factor of the micromirror array. The LMEM-DM provides superior aberration correction with low residual diffraction effects. For mirror deflections much smaller than the lenslet focal length, the LMEM-DM behaves as a phase-only modulating optical element. The LMEM-DM thus serves as a rugged, compact optical element for beam steering, beam shaping, and aberration correction applications.