From Static Thermal and Photoelectric Laser Stimulation (TLS/PLS) to Dynamic Laser Testing

This paper describes a new way to analyze inertial MEMS with the electro-optical technique. Usually, this technique is used in failure analysis to probe on electronic devices from old technologies to modern VLSI. In our case, we make use of the variation in power of the reflected beam between different layers of materials in an accelerometer (MEMS). We introduce a new method based on the electro-optical technique to extract a physical resonant frequency in inertial MEMS.

The mixed-mode ICs (Integrated Circuits), by involving multiple functions (digital, analog, RF, power) inside one device, are becoming more compact and useful. At the same time, their developments and Failure Analysis (FA) are more and more complex: test, diagnostic and defect localization steps are harder and longer in time. Each step needs to be improved as far as defect localization is concerned. Several techniques based on emission microscopy, electron beam, direct probing or laser stimulation have been developed and introduced to follow these ICs evolutions. The most recent evolution in the laser stimulation field has been the introduction of several dynamic laser stimulation techniques aimed to localize defects or weakness regions inside functional but failing ICs (environmental marginalities related to temperature, frequency, voltage, etc.). This paper deals with the use of dynamic photoelectric laser stimulation techniques applied on mixed-mode ICs where the major difficulty is due to their considerable intrinsic sensitivity. Indeed, the analog circuitry is more sensitive than the digital circuitry since a slight change in an electrical parameter can trigger a functionality failure. This property limits the defect localization because of the complex interpretation of the results, the laser stimulation mapping. We propose to help the failure analyst by coupling the dynamic laser stimulation mapping with the photoelectric impact simulations run on a previously analyzed structure. The goal is to predict and interpret the laser sensitivity mapping so to isolate the defective areas in the analog devices.