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Electrically Conductive Self-Assembled Monolayer (SAM) Anti-Stiction Coating for Micro-Electromechanical Systems (MEMS)


OUSD (R&E) CRITICAL TECHNOLOGY AREA(S): Hypersonics; Microelectronics; Nuclear The technology within this topic is restricted under the International Traffic in Arms Regulation (ITAR), 22 CFR Parts 120-130, which controls the export and import of defense-related material and services, including export of sensitive technical data, or the Export Administration Regulation (EAR), 15 CFR Parts 730-774, which controls dual use items. Offerors must disclose any proposed use of foreign nationals (FNs), their country(ies) of origin, the type of visa or work permit possessed, and the statement of work (SOW) tasks intended for accomplishment by the FN(s) in accordance with the Announcement. Offerors are advised foreign nationals proposed to perform on this topic may be restricted due to the technical data under US Export Control Laws. OBJECTIVE: Develop an anti-stiction self-assembled monolayer (SAM) coating that is electrically conductive along the molecule chain, but not conductive between molecules. DESCRIPTION: SAM coatings have been shown to reduce stiction-related failures for Micro-Electromechanical Systems (MEMS) devices during fabrication and in operation. Although industry has incorporated this technology into commercial products such as accelerometers and gyroscopes, the requirements for strategic sensors necessitate special considerations, including minimizing induced stresses from mismatches of coefficients of thermal expansion (CTE), designing the sensor to be robust through strategic radiation environments, preventing parasitic charges from creating erroneous signals, and ensuring that the sensor will be stable over several decades. Examples of existing research for SAM coatings can be found in the referenced articles [Refs 1-3]. MEMS sensors are more frequently being considered as alternatives to conventionally machined sensors in order to meet stringent performance requirements. This SAM coating is likely to bring value to multiple industries as the need for stability and reliability become more important. PHASE I: Design a SAM coating for wafer-level processing with the desired goals of 1) reducing stiction in a silicon MEMS device; 2) allowing electrical conduction along the molecule chain (goal of < 100 Ohm resistance between the coating and silicon substrate), but not across molecules (goal of > 1 MOhm resistance laterally across the coating); 3) selectively coating only exposed silicon surfaces, and not oxide or metal surfaces 4) ensuring stability of the coating for up to 30 years. Material space is not constrained and unique designs are encouraged. The Phase I study shall assess all aspects of fabrication and justify the feasibility and practicality of the designed approach. The Phase I Option, if exercised, will include the initial design specifications and capabilities description to build a prototype solution in Phase II. PHASE II: Based on the Phase I design and execution plan, fabricate and characterize a small lot (up to Qty: 5 wafers) of silicon articles with the sample coatings. This characterization may include coating selectivity, coating conductivity, stiction reduction for sample MEMS devices, and thermal sensitivity for sample MEMS devices. These articles do not need to incorporate etched features – however, the prototypes must address the desired goals specified during Phase I. The prototypes, test samples, and characterization results should be delivered by the end of Phase II. PHASE III DUAL USE APPLICATIONS: Based on the prototypes developed in Phase II, continuing development must lead to productization of the SAM coating. While this technology is aimed at military/strategic applications, SAM coatings are used more broadly in the MEMS industry. Perform final qualification by inserting and demonstrating the SAM coating into a known microfabrication process for a MEMS design. (Note: The devices incorporating the SAM coating may be subject to several common test environments for strategic sensors, including radiation and vibration environments.) A stable SAM coating carefully designed to reduce parasitic effects (such as charging in the coating) is likely to bring value to existing commercial applications such as space and autonomous vehicle navigation to improve both the reliability and performance of high-end MEMS sensors. REFERENCES: 1. Maboudian, Roya; Ashurst, W. Robert; Carraro, Carlo. “Self-assembled monolayers as anti-stiction coatings for MEMS: characteristics and recent developments.” Sensors and Actuators 82, October 1999: 219-223. 2. A. Rissanen et al. “Vapor-phase self-assembled monolayers for improved MEMS reliability.” SENSORS, 2010 IEEE: 767-770. 3. Y.X. Zhuang et al. “Vapor-Phase Self-Assembled Monolayers for Anti-Stiction Applications in MEMS.” Journal of Microelectromechanical Systems, Vol. 16, No. 6, December 2007: 1451-1460. KEYWORDS: Self-assembled monolayers; coatings; micro-electromechanical systems; microfabrication; anti-stiction; wafers
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