Applications of Picosecond Laser Acoustics to Power Semiconductor Device: IGBT and MOSFET

Picosecond Ultrasonics (PULSE$^{TM})$ Technology has been the unique metrology tool for single-layer and multilayer metal films in semiconductor process control. [1] PULSE Technology is an industry benchmark for metal metrology and is a tool-of-record in multiple device segments, including logic, radio frequency (RF), memory, microelectromechanical systems (MEMS) and flash. In addition to thickness, the non-destructive technique has been adopted to provide elastic modulus, which is a critical parameter for process control. For example, low-k materials in logic and DRAM, amorphous carbon (a-C) in 3D NAND and AlN in RF filter devices are all exclusively characterized in-line using Picosecond Ultrasonics Technology.In recent years, power semiconductor applications have expanded from industrial control and consumer electronics to energy, rail, smart grid, inverter home appliances, electrical vehicles and other markets. The market size for global power components is estimated to be ${\$}$97.2 billion (U.S.) by 2030, with a compound annual growth rate of 6.30% by Market Research Future (MRFR). [2] As the automobile industry transitions from traditional cars to electric vehicles, the increase in automotive electronics has been beneficial to the power semiconductor market. The value of semiconductor components for a pure electric vehicle can be ${\$}$750 (U.S.); the value of power semiconductor alone is about ${\$}$413 (U.S.), which is about six times the price of a power semiconductor for a traditional car.In this paper, we demonstrate how PULSE Technology can be applied to the production of power semiconductors, specifically insulated gate bipolar transistors (IGBT) and metal oxide semiconductor field effect transistors (MOSFET), targeting both the frontside (gate metallization) and backside (backside metallization). We show how PULSE Technology is capable of being used for standard power semiconductor applications involving single-layer metal films and offers excellent repeatability, long-term stability, and fast and reliable thickness profile measurement. For a gate metallization application with a three-to-five layer stack, we demonstrate PULSE Technology’s unique advantage when it comes to measuring multiple layers with a single measurement, while offering excellent repeatability and long-term stability. We also show how PULSE Technology offers improved repeatability and throughput by using dual modulation and/or crossed polarization for relatively rough films, such as aluminum, and backside metallization (BSM) stacks.