| As the continuous development of semiconductor manufacturing technology,the wafer sizes are getting larger and larger,and the features on wafers are getting smaller and smaller.To ensure the positional repeatability and dimensional consistency of the different processes,wafer inspection with metering effects becomes critical.Atomic force microscopy(AFM)has high-resolution capability for three-dimensional measurement and is widely used in semiconductor detection.However,most current AFM systems with metering functions employ the sample scanning structure,which make the sample stage difficult to carry large-sized wafer samples.Furthermore,the probe scanning method in the AFM can be used for wafer inspection mostly,using a tube scanner or tripod scanner,but the scanning track shows arch distortion which is not able to meet the measurement requirements.In response to the above problems,this paper proposed and developed a metering AFM system based on probe scanning structure for 12-inch wafer inspection,which uses a plate scanner to eliminate the arch distortion.Six laser interferometer mounting holes are designed for the traceability of dimensional measurement results.The specific works are shown as follows:1.The typical inspection methods of wafer feature structure are introduced,and the limitations of the current AFM systems for wafer metrology detection are analyzed.2.An AFM measuring platform was developed for 12-inch wafer inspection.The design and assembly of the marble frame structure as well as the installation and debugging of the three-dimensional large-traveling range with rough positioning platform were completed.Based on the demand of traceability,the measurement scheme were designed.3.An AFM probe with three-dimensional orthogonal scanning function was developed.The construction and debugging of the 3D follow-up optical lever detection optical path and the upright microscopic observation optical path were completed.The scanning system based on the serial 2D plate scanner,Z scanner and compensational scanner was designed.A probe clamping mechanism and a suitable probe changing method were also developed.4.An overall performance test of the developed AFM system were conducted.The sensitivity of the detection optical path and the scanner was calibrated.The optical lever detection error caused by the scanner motion was measured.The imaging noise of the system was evaluated,and the scanning imaging capability and the accuracy of the measurement result in the contact mode and the tapping mode were verified. |
