MEMS Sensors and Carrier-Level Reliability

Objectives

Background

Approach

Objectives

Develop necessary metrology techniques and perform environmental testing to identify and document the dominant defects, failure mechanisms, failure modes, and failure sites in hermetic and non-hermetic MEMS-based systems consisting of sensors, actuators, chip-to-chip bonded parts, and electro-optical interfaces.

Background

Developments in MEMS technology have made possible the design and fabrication of a wide variety of interesting and potentially useful devices. In order for MEMS applications to successfully transition from proof-of-concept to commercial viability, key manufacturability and reliability requirements must be met. Reliability is particularly a challenge because: 1) many promising MEMS applications will be in safety critical systems where the cost of failure is catastrophic, 2) MEMS technologies are new, and the associated failure mechanisms are poorly understood, 3) MEMS technology is evolving rapidly, and 4) design tradeoffs must account for reliability in order to control warranty costs.

This program continues the work of projects C99-52 and C00-45. In C99-52, chip-to-chip bonding of die was assessed for several different bond materials (Indium solder, thermoplastic paste, thermoplastic film and epoxy film), and bonding configurations (with an Alloy 42 spacer, silicon to ceramic, and silicon to silicon). Metrology using Acoustic Micro Imaging (AMI) was developed to determine the fraction of delamination of samples. Testing of the samples in C99-52 consisted of thermal cycling and accelerated aging. Chip-to-chip bonding environmental testing was completed in C00-45 by performing mechanical shock and die shear testing. C00-45 also extended the reliability analysis performed in C99-52 to the carrier-level by characterizing and performing environmental testing on hermetic and non-hermetic packaged carriers containing MEMS humidity sensors and microrelays.

Approach

This project will have three thrusts:

1. Completion of carrier-level testing from the C00-45 project - environmental testing should be completed prior to the start of this project, however, analysis of the data obtained and follow-up testing (if any) will be performed in this project.
2. Detailed failure analysis of MEMS LIGA structures and FEM modeling to support and the environmental test results collected in C99-52 and C00-45 - considerable data has been collected over the last two years, this thrust will develop models that aid in understanding the experimental results.
3. Introduction of a fiber optic interface into the carrier-level package - other efforts at the University of Maryland (outside of CALCE) have developed a fiber optic based interrupter for verifying the position of MEMS structures, this project will address the reliability issues associated with the fiber optic interface with the package and the interrupter design.

Special Considerations:

The Naval Surface Warfare Center (NSWC) has requested that this project be exempted from normal CALCE publication restrictions and allowed to publish (contingent upon the approval of NSWC) during the course of the project in order to raise awareness of NSWC's efforts in MEMS development.