Scanning Magneto-optic Kerr effect microscope for inspection of MRAM manufacturing

• Published in: IEEE transactions on magnetics Vol. 59; no. 11; p. 1
• Main Authors: Numata, Mitsunori, Kim, Ingi, Suzuki, Kenji, Ueyama, Shinji, Kim, Jinseob, Kim, Wookrae, Lee, Myungjun
• Format: Journal Article
• Language: English
• Published: New York IEEE 01.11.2023; The Institute of Electrical and Electronics Engineers, Inc. (IEEE)
• Subjects: Cameras; Electromagnets; High speed; Inspection; Kerr magnetooptical effect; Magnetic anisotropy; Magnetic fields; Magnetic hysteresis; Magnetic properties; Magnetism; Manufacturing; Memory devices; MOKE; MRAM; Optical films; Optical imaging; Random access memory; Semiconductor devices; Static random access memory; TDI Camera; Time lag
• ISSN: 0018-9464; 1941-0069
• DOI: 10.1109/TMAG.2023.3289335

Spin transfer torque Magneto-resistive random access memory (STT-MRAM) is becoming next-generation non-volatile memory, for example replacement of embedded Flash and SRAM in Logic Devices. In semiconductor device manufacturing, the inspection process is very important for yield management. Optical inspection equipment is often used to detect defects in device patterns, however as for MRAM inspection, it is desirable to detect not only device patterns but also magnetic property at the same time. The magneto-optic Kerr effect (MOKE) microscope is a two-dimensional evaluation method for magnetic property using MOKE. In this paper, a high-speed inspection method for evaluating magnetic property called Scan MOKE is proposed by combining MOKE microscope with time delay integration (TDI) camera, a scan stage, and a electromagnet that enables a position dependent magnetic field in the scan direction (gradient magnet). This method shows to provide a high speed evaluation the magnetic properties based on the thickness and the anneal conditions of the perpendicular magnetic anisotropy (PMA) STT-MRAM.