Baghbanha, S. (2015). Solderability of evaporated and sputtered metallic layers [Diploma Thesis, Technische Universität Wien]. reposiTUm. http://hdl.handle.net/20.500.12708/79875
E164 - Institut für Chemische Technologien und Analytik
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Date (published):
2015
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Number of Pages:
89
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Keywords:
Semiconductor; Backside Metallization
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Semiconductor; Backside Metallization
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Abstract:
The manufacturing process of semiconductor devices is divided into two parts: the front end processes where the electrical devices are finished on wafer-level and the backend processes where the wafers will be sawed, the separated devices bonded and packaged. One of the main criteria for a reliably functionality of the device is a good electronic and mechanical connection between the metal-layers of the chip (front end process) and the bonding material (back end process). A deviation of the required properties of the metal-layers due to manufacturing problems is usually detected only during the bonding process. Since the time between the front end processes and the back end processes can extend to a few months, the risk of a high amount of non-working devices in case of manufacturing deviations is very high. Therefore it is essential to get the information about the solder behavior as fast as possible, ideally directly after the deposition of the metal layers in the front end factory. The aim of this diploma thesis is to develop and establish a control concept for the solder behavior of two different metal stacks: one is the so called sputtered solderable frontside metal-stack (Ti/Ni/Ag on Al), the other one an evaporated backside metal stack (Al/Ti/Ni/Ti/Ag on Si). Based on existing soldering processes done at the Infineon factory in Malacca the student should be exposed to this special soldering processes and acquire the main test parameters and properties to distinguish between a good and a bad device. For this purpose the solder process must be established on a special reflow-furnace. A measure for the quality of the metal stack could be the force needed to crack the interface metal-solder (pull test). The reflow furnace and the pull tester will be available in Villach. The structuring of the solderable frontside metal stack is done by a lift-off technique, resulting in a big amount of factors influencing the electrical and mechanical quality of the metal stack. For the evaporated metal stack the main influencing parameters for the quality of the metal layers are the conditions during the evaporation process itself and the following thermal annealing of the metal stack. For both processes the main influencing parameters should be identified and quantified leading to suitable limits for the process results. After the setup of a working control process, all relevant parameters/measurements should be implemented in a special Infineon specific tool for statistical process control. To minimize costs the control concept should consider the preparation of test wafers just with the necessary amount of process steps. The creation of an automated process flow for this control concept would be the last step. Additionally the student will become familiar with some of production relevant processes and analysis methods like deposition of sputtered and evaporated metal layers, etching of silicon wafers, annealing processes, four-probe sheet resistance measurements, residual gas analysis, Auger electron spectroscopy, focused ion beam and scanning electron microscopy.