TY - JOUR A1 - Tremmel, Florian A1 - Nagler, Oliver A1 - Kutter, Christoph A1 - Holmer, Rainer T1 - Mechanical robustness analysis of semiconductors with a single needle probe card using acoustic emissions JF - e-Journal of Nondestructive Testing N2 - The combination of indentation testing and acoustic emission (AE) is widely used to analyze the fracture toughness of test substrates. In the manufacturing of semiconductor devices this material parameter also plays an important role. During the so-called wafer testing inside a wafer prober small probe tips are pressed onto the chip surface to check its performance. To prevent damaging the chip by that, the fracture toughness and load limit of it has to be defined in a prequalification step. This paper presents a test system that imitates the wafer testing process as close as possible and uses acoustic emission to detect appearing cracks and thereby also the load limit. The frontend of the test setup consists of a modular single needle probe card which can be placed in a wafer prober. Also, the indenter properties (tip diameter, stiffness, etc.) can be adjusted to the probe used later on during productive wafer testing to ensure realistic probing conditions. A piezoelectric sensor and a full strain gauge Wheatstone bridge are implemented close to the single indenter to measure the AEs and the applied contact force respectively. The signal-to-noise-ratios (SNRs) of both sensors are improved with an own analog amplifier module before recording them with an USB oscilloscope. A developed measurement software (LabVIEW) is used to adjust measurement parameters (trigger limit, record length, conversion factors, etc.) and automatically store and separate measurement data from different acoustic events and imprints. To evaluate the result files a second software tool (MATLAB) reads the files out and clusters the recorded events to separate crack signals from electrical and mechanical disturbances. With a prototype first test results are generated and the functionality and accuracy of the measurement concept is proven. KW - Acoustic Emission KW - Crack probability distribution KW - Fracture load limit KW - Wafer testing Y1 - 2024 U6 - https://doi.org/10.58286/30254 SN - 1435-4934 VL - 29 IS - 10 PB - NDT.net ER - TY - JOUR A1 - Tremmel, Florian A1 - Nagler, Oliver A1 - Kutter, Christoph A1 - Holmer, Rainer T1 - Double-Beam Cantilever Probe for Crack Probability Analysis of Multilayer Substrates During Wafer Probing JF - IEEE Sensors Journal N2 - During wafer testing, small probes are contacting pads on the wafer surface to check the chip functionality and identify faulty dies. To prevent damaging structures underneath, a mechanical load limit needs to be defined. This is done by intentionally overstressing the pads and searching for cracks that appear. A customized test bench with a patented sensor-indenter (SI) system is currently used to perform the contact cycles and identify crack formations in real time using the generated acoustic emissions (AEs). This method is faster and more accurate compared with previous optical detection methods. This article presents an improved version of the SI system usable in a wafer prober, featuring a double-beam cantilever beam with an exchangeable indenter tip. This leads to measurement conditions closer to productive wafer testing, enabling more accurate load limit definitions. The cantilever beam contains a strain gauge Wheatstone bridge for contact force measurement and a piezoelectric sensor element for AE signal detection. Amplifier circuits are designed for both sensors, and a data acquisition (DAQ) system is developed. A prototype of the sensor cantilever combination (SCC) is shown together with simulated and experimental results. The accuracy of the force sensor ( ±0.5 → ±1.3 mN) and the signal-to-noise ratios (SNRs) of the AE signals ( 29.1 → 21 dB) show only a small decrease compared with the previous SI system. A crack probability analysis of a test specimen confirms the usability of the SCC, as AE crack signals are detected at a similar mechanical load with both sensor setups. KW - Acoustic emission (AE) testing KW - double-beam cantilever load senso KW - fracture load limit KW - operational amplifier circuit Y1 - 2024 U6 - https://doi.org/10.1109/JSEN.2024.3486355 VL - 24 IS - 24 SP - 40295 EP - 40304 PB - IEEE ER - TY - CHAP A1 - Tremmel, Florian A1 - Nagler, Oliver A1 - Kutter, Christoph A1 - Holmer, Rainer T1 - Smart Cantilever Probe with Integrated Force and Acoustic Emission Sensor T2 - 2023 IEEE SENSORS, Vienna, Austria, 10/29/2023 - 11/1/2023 N2 - Acoustic emission (AE) testing recently found its application in the wafer testing sector of the semiconductor industry. To find out the mechanical robustness of semiconductor devices, contact pads on the chip surface are intentionally overstressed with an indenter tip and the appearing oxide cracks are detected with help of the generated AE signals. This is done in a customized test bench with a patented sensor-indenter system. This paper presents an improved version of the measurement setup that solves certain disadvantages of it and can be used in a standard wafer prober. The main components of the developed sensor system are a strain gauge for contact force measurement and a piezoelectric sensor element for AE signal detection. Both components are integrated on a cantilever beam which has an exchangeable indenter tip at its free end. The cantilever probe is electrically conductive to enable electrical tests via the indenter tip. This smart sensor-cantilever combination (SCC) can be mounted with several adapter components on a carrier plate to place it in a wafer prober. For both sensor elements amplifier circuits are developed to enhance their signal-to-noise ratios (SNRs). A prototype setup is shown together with simulated and experimental results to demonstrate its performance. The mechanical properties of the cantilever, as well as the force sensor and the AE crack signals, already fulfill the requirements for an implementation in a wafer prober. To further improve the sensor resolutions and detection limits, several optimizations regarding the design of the SCC are in progress. KW - Acoustic emission testing KW - piezoelectric sensor KW - strain gauge KW - operational amplifier circuit Y1 - 2023 SN - 979-8-3503-0387-2 U6 - https://doi.org/10.1109/SENSORS56945.2023.10325021 SP - 1 EP - 4 PB - IEEE ER - TY - JOUR A1 - Unterreitmeier, M. A1 - Nagler, Oliver A1 - Pfitzner, L. A1 - Weigel, R. A1 - Holmer, Rainer T1 - An acoustic emission sensor system for thin layer crack detection JF - Microelectronics Reliability N2 - We present a new method for semiconductor layer characterization enabling simultaneous crack generation and detection based on the established acoustic emission testing. In this paper, we explain the test concept and failure mechanism of diamond tip indentation with acoustic wave measurement on oxide layers by analytical modeling and computer-aided simulations. For this purpose, an innovative design of a sensor-indenter system was developed and experimentally verified. In further tests, the new acoustic crack detection method is correlated with proven optical inspection methods and the good reproducibility of the measurement is demonstrated. The high sensitivity and resolution of this method offer new opportunities for thin layer characterization at lower time and cost. The new high-efficient method can be used especially for process qualification for semiconductor wafer test, where oxide cracks can be induced by sharp probes causing electrical failure of the chip. KW - FLAT KW - INDENTATION Y1 - 2018 U6 - https://doi.org/10.1016/j.microrel.2018.07.015 VL - 88-90 IS - September SP - 16 EP - 21 PB - Pergamon-Elsevier ER -