<title>Microfabricated silicon gas chromatographic microchannels: fabrication and performance</title>

Abstract

Using both wet and plasma etching, we have fabricated micro-channels in silicon substrates suitable for use as gas chromatography (GC) columns. Micro-channel dimensions range from 10 to 80 pm wide, 200 to 400 p m deep, and 10 cm to 100 cm long. Micro-channels 100 cm long take up as little as 1 cm' on the substrate when fabricated with a high aspect ratio silicon etch (HARSE) process. Channels are sealed by anodically bonding Pyrex lids to the Si substrates. We have studied micro-channel flow characteristics to establish model parameters for system optimization. We have also coated these micro-channels with stationary phases and demonstrated GC separations. We believe separation performance can be improved by increasing stationary phase coating uniformity through micro-channel surface treatment prior to stationary phase deposition. To this end, we have developed microfabrication techniques to etch through silicon wafers using the HARSE process. Etching completely through the Si substrate facilitates the treatment and characterization of the micro-channel sidewalls, which dominate the GC physico-chemical interaction. With this approach. we separately treat the Pyrex lid surfaces that form the top and bottom surfaces of the GC flow channel.

<title>Integratible process for fabrication of fluidic microduct networks on a single wafer</title>

“…R, and the indentation modulus E*. The elastic response relationship of the curve is given in equation (1).…”

Post-Processed Integrated Microsystems

“…15 Micro-channel devices have several advantages over more conventional GC structures including reduced size and cost, lower dead volume, and design flexibility. The performance of such devices is highly dependent upon optimization of channel length, width, and depth.…”

“…The 1 µm wide trenches were etched to an approximate depth of 7.5 µm while the 3.5 µm trenches were etched to a depth of approximately 9.5 µm. 15 for the reactive species to diffuse to the bottom of the trench and more difficult for etch products to be extracted. Improved ARDE effects have been obtained for the DRIE process under high SF 6 flow conditions due to a reduction in redeposition of etch products.…”

Gas phase chemical detection with an integrated chemical analysis system

“…A Si DRIE process, similar to that used to fabricate the preconcentrator, is employed to produce the GC column [4]. Because of the exceptionally high aspect ratio and anisotropy of the DRIE process, closely spaced, narrow gas flow channels can be etched into the Si substrate to a depth many times the channel width.…”

“…After the channels are etched, the Si substrate is thermally oxidized to produce a thin, glasslike layer on the surface of the channels in order to facilitate stationary phase deposition (see below). Closed channels are produced by anodically bonding a Pyrex lid to the top surface of the Si substrate [4]. Since the bonding process is carried out at elevated temperatures, Pyrex is used because it closely matches Si's thermal expansion coefficient.…”