Long Term Stability of Polysilicon Microelectromechanical Structures

9410989布朗这项工作将研究多晶硅微机电结构（MEMS）的故障模式和长期结构稳定性。 我们发现目前缺乏对MEMS可靠性的研究，这是令人震惊的，因为许多MEMS设计用于在不利条件下持续很长一段时间。 具体而言，我们打算实现以下目标。 1.识别多晶硅微机电结构的失效模式。 在了解可能的故障模式之前，无法实现MEMS的长期性能。 2.为MEMS的加速测试提供了一个协议。 虽然MEMS可以运行数十年，但在投入使用之前无法进行这段时间的测试。 必须开发加速测试技术来评估设备的长期性能。 3.表征多晶硅结构的可靠性作为工艺和几何形状的函数。 我们已经表明，由于环境的影响，在单晶硅微机电结构的裂纹生长的可能性。 根据附加的微观结构特征，如晶界，我们可以预期多晶硅中的附加失效模式。 4.设计测试结构以指示初期或可能的故障。 这些结构旨在与操作MEMS器件一起放置，以检测裂纹萌生、永久变形、冲击或结构响应的变化。 这项工作对于确保可靠的MEMS应用至关重要。 ***

9410989 Brown This effort will examine failure modes and long term structural stability of polysilicon microelectromechnical structures(MEMS). We find the current absence of research on MEMS reliability striking given that many MEMS are designed to last long periods of time under adverse conditions. Specifically, we intend to address the following goals. 1. Identify failure modes for polysilicon microelectromechanical structures. Long term performance of MEMS cannot be achieved until possible failure modes are understood. 2. Provide a protocol for accelerated testing of MEMS. Although MEMS are meant to operate for decades, they cannot be tested for that period before being put to use. Accelerated testing techniques must be developed to assess the long term performance of the devices. 3. Characterize the reliability of polysilicon structures as a function of processing and geometry. We have shown the possibility of crack growth in a single crystal silicon microelectromechanical structure due to environmental effects. In light of additional microstructural features s such as grain boundaries, we may expect additional failure modes in polysilicon. 4. Design test structures to indicate incipient or possible failure. These structures are meant to be placed with operating MEMS devices to detect crack initiation, permanent deformation, shock, or changes in structural response. This work is essential to ensure reliable MEMS applications. ***