H.T.M. Pham

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In this paper we present a novel post-process surface micromachining module that uses a commercial PI2610 polyimide as a sacrificial layer and PECVD SiC or SiN as structural layers. No wet etching is required thus avoiding stiction problems often encountered in wet sacrificial etching processes. A mask set containing cantilever beams, membranes, rotating(More)
Porous SiC has been found to be extremely sensitive to the presence of ammonia (NH/sub 3/) gas. We report the fabrication and preliminary characterisation of NH/sub 3/ sensors based on porous SiC and Al electrodes. The idea of the SiC is that it is a very durable material and that it should be good for sensors in harsh environments. Until now the only(More)
This paper presents a new low-cost, CMOS-compatible and robust wafer-level encapsulation technique developed using a stress-optimised PECVD SiC as the capping and sealing material, imparting harsh environment capability. This technique has been applied for the fabrication and encapsulation of a wide variety of surface- and thin-SOI microstructures that(More)
MEMS electron-transparent membranes made of low-stress silicon nitride are widely employed in electron microscopy. However, this material has limited resistance to electron beams. We therefore developed a layer of LPCVD SiC. Our layer is amorphous, uniform, continuous, low-stress, and has extremely low etch-rates in common wet etchants. As free-standing(More)
This paper presents the design, fabrication and characterization of a new concept of microsieves with vertical nano-perforated walls. A new approach is applied to realize these walls accurately without sophisticated or non-conventional lithography while preserving IC-compatibility. By simply changing the deposition and etch time in the fabrication process,(More)
Very thin (20-200 nm) SiC membranes with controlled composition and thickness, low tensile stress, layer continuity and etching selectivity are fabricated using a specially developed LPCVD process. These characteristics are necessary for their application in vacuum sensors, especially for operation in harsh environment. The continuity, low stress (180 MPa)(More)
We report a new RH sensor based on a porous SiC membrane and Al electrodes. The RESET function has also been successfully tested. Using SiC allows us to fabricate sensors that can withstand harsh environments, while using Al for the electrodes makes the fabrication process much more cleanroom friendly. SEM images were used to examine the fabricated devices.(More)
In this paper we present a new technique to vertically grow aligned carbon nanotubes (CNTs) on nanosize pore anodic aluminum oxide (AAO) templates on a Si substrate. The CNTs are grown using methane in an RF PECVD system at only 400/spl deg/C without using a transition metal catalyst. The AAO templates are prepared by a two-step anodizing process in oxalic(More)
In this paper an in-situ isotropic and anisotropic deep reactive ion etching (DRIE) sequence process is presented to obtain a periodic asymmetric variation along the z-axis in pore diameter on silicon wafers, which can act as massively parallel and multiply stacked Brownian ratchets. The etch rates of isotropic and anisotropic etching process depends(More)
Anisotropic etchants like TMAH are used to etch cavities with smooth sidewalls in silicon wafers for MEMS applications. However, complicated crystalline alignment steps are usually needed as crystalline misalignment will enlarge and rotate the etched cavities in an unpredictable way. In this paper, we presented a simple process to avoid unexpected cavity(More)