Research On Evaluating The Performance Of Wafer Focusing And Leveling Sensor

Information industry plays a mainstay role in development of national economy, but it depends on the Integrated Circuit technology which is pushed forward by design, process and equipment. The optical lithography tool is the key equipment for fabrication of IC. Being one of the critical subsystems of lithography tool, focusing and leveling sensor is worth researching. Focusing and leveling sensor is used to detect wafer position with respect to the lens, and feeds back to wafer stage. So, wafer stage can accurately control the position of wafer surface. The thesis is trying to resolve the problem that the lithography tool working in defocus state because of the failure of the focusing and leveling sensor.Due to its complexity, it takes the laser interferometer as the main instrument, the performance of focusing and leveling sensor can be evaluated by comparing its result with the result measured by laser interferometer. Then an appropriate algorithm is used to compensate the error which resulted by the fluctuating of the temperature and the pressure, then, the measuring accuracy and stability are improved obviously, and it reaches 5nm measurement accuracy in vertical. A super precision stage with 3 axes simulates the exposure chuck to drive wafer. The three-dimensional measurement module of laser interferometer is established by simplifying the formula to calculate the height and the rotation of wafer.For the high reliability, it must simulate the lithography's working conditions, the Temperature Control Unit and the temperature measuring appliance are used to control the environment temperature with an algorithm, and the error which resulted by the vibration is eliminated by the shock-absorbing system.A test bench is built on account of the theory advanced by the thesis, the test bench provides a simulated condition for the focusing and leveling sensor, and it can be used to evaluate the accuracy, resolution and repeatability of the sensor with its high performance. With the exception of this, the test bench can correct the error resulted by the deforming of mechanical structure and the drifting of temperature. So, it improves the lithography tool's performance and efficiency, and can be used to evaluate the focusing and leveling sensor's performance in 100nm resolution lithography tool.