Pattern Photoresist Silicon Silicon Nitride Silicon Photoresist Silicon Nitride Silicon Etch Nitride Remove Photoresist

In this proposal we seek to establish a porous silicon based etching process in the WTC microfabrication laboratory. The new process will allow us to etch high aspect ratio holes through a wafer. Holes like these are important for decreasing the dead volume of connections between micro and macro systems and for increasing the complexity of micro-fluidic systems. At the present time, the minimum size of through holes we can etch in a 4 " wafer is about 500 m 500 m with a total volume of approximately 100 nl. The new process will allow through holes with a cross section smaller than 20 m (total volume approximately 0.2 nl, a factor of 500 less than previously achievable in our laboratory.) Briefly, the project consists of two parts. First, we will design, machine, build, and characterize an electrochemical etching cell and associated electronics that will be situated in the WTC microfabrication laboratory. Second, we will use this new process to fabricate a number of new microfluidic devices that exploit the new capabilities. Competitive technologies (deep reactive ion etching) are available at other laboratories, but have a big disadvantages. The machinery is expensive (at least $500k). This porous silicon based process will be complementary to that offered with deep reactive ion etching. The etching cell will also be capable of forming porous silicon, which has exciting material with optical applications. Commercial applications are anticipated for any company that is interested in complex fluidic circuits and low dead volume interconnects. Nationally, this includes companies working on integrated genetic analysis systems (Perkin Elmer/Applied Biosystems and Molecular Dynamics) and high throughput screening for drug discovery applications (Caliper Technologies and Orchid Biocomputer along with the major pharmaceutical companies, Johnson and Johnson, SmithKline Beecham, etc.) Micro-fluidics is still a research field. There is commercial interest, but there is no real " killer app " for micro-fluidic systems yet. Virtually everything done in these systems can still be done (faster and better) by a laboratory technician. An application so useful that it cannot be ignored is needed to advance the technology from the laboratory research stage to practical products. Once an initial application begins large-scale commercialization, the manufacturing and systems issues will be solved and many other applicatons become feasible. The problem is to find a unique application that takes advantage of the capabilities of a micro-fluidic system. Attempts to date have tried to focus on (a) …