Abstract
The uniqueness of microelectromechanical system (MEMS) devices, with their multiphysics characteristics, presents some limitations to the borrowed test methods from traditional integrated circuits (IC) manufacturing. Although some improvements have been performed, this specific area still lags behind when compared to the design and manufacturing competencies developed over the last decades by the IC industry. A complete digital solution for fast testing and characterization of inertial sensors with built-in actuation mechanisms is presented in this paper, with a fast, full-wafer test as a leading ambition. The full electrical approach and flexibility of modern hardware design technologies allow a fast adaptation for other physical domains with minimum effort. The digital system encloses a processor and the tailored signal acquisition, processing, control, and actuation hardware control modules, capable of the structure position and response analysis when subjected to controlled actuation signals in real time. The hardware performance, together with the simplicity of the sequential programming on a processor, results in a flexible and powerful tool to evaluate the newest and fastest control algorithms. The system enables measurement of resonant frequency (Fr), quality factor (Q), and pull-in voltage (Vpi) within 1.5 s with repeatability better than 5 ppt (parts per thousand). A full-wafer with 420 devices under test (DUTs) has been evaluated detecting the faulty devices and providing important design specification feedback to the designers.
Highlights
Test and characterization of microelectromechanical systems (MEMS) is a mandatory step towards the improvement of both quality control and design iteration processes
The system enables measurement of resonant frequency (Fr), quality factor (Q), and pull-in voltages (Vpi) in 1.5 s (3–7 times faster than the results presented in [5]) while on the other hand, the use of a softcore processor enables a high degree of flexibility, making it possible to quickly adapt or change the testing algorithms for different devices, as opposed to using fully hardware implementations, as is the case in [5]
The results show that full mechanical characterization is obtained in less than 1.5 s without any algorithm optimization
Summary
Test and characterization of microelectromechanical systems (MEMS) is a mandatory step towards the improvement of both quality control and design iteration processes. The low-latency possibilities offered by this technique [5,6], the possibility to test a large range of sensitivities of devices [6], and the lack of need for using costly mechanical stimulation are good arguments to develop this approach This traditional IC technology still needs to be further enhanced to adjust to MEMS multiphysics behavior, which is still in an early development phase, in comparison to the well-studied manufacturing and design efforts [1]. Other approaches, such as [8], use optical microscopy associated with image-processing algorithms to measure the device depths, sizes, and cavities An alternative to these tests is the electromechanical testing provided by tools such as the FT-MPS02 MEMS probe station by FEMTOTOOLS [9], where a nanoposition platform and a sensing microprobe can be used to physically apply forces to the structure and evaluate the actual system response. Some conclusions are presented regarding the suitability of the presented approach for MEMS testing, characterization, and process monitoring
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