Wafer, the primary material used to make semiconductor chips, are found in almost every type of electronic device used in everyday life. As the quality of wafer used in large-scale integrated circuits has improved considerably, the diameter of wafer has continued to increase, and the thickness of silicon wafer has become increasingly thin. Wafer manufacturers and device manufacturers are increasingly focusing on wafer thickness variation. In the past few years, the usual capacitive tools for wafer inspection have been replaced by interferometric tools for higher sensitivity and resolution. We, therefore, describe a method that uses two Fizeau-type phase-shift interferometers to simultaneously measure the front and back surfaces of a vertically placed wafer and calculate the thickness variation of the wafer based on the resulting morphologies. The reliability of the method was verified by comparing the wafer thickness variation obtained from experimental measurements with that obtained from optical glass bonding. Over three days, five consecutive measurements were performed daily on 50mm wafer using this method, and the experimental results showed that the average values of RMS (Root Mean Square) of the thickness variation calculated for each day were 41.843nm, 40.751nm, and 40.490nm, and the average values of PV (Peak to Veally) were and 206.761nm, 205.252nm, and 209.800nm, and the measurements proved to be highly reproducible. The method has good stability and reliability to meet the measurement of wafer thickness variation.
Ring elements are of great significance in the field of precision machining, and their performance is crucial for the functionality of the whole system. However, the present frequent inspection of such components lacks effective means and is prone to causing damage to the component. In view of this, this article on the basis of comprehensive research, combined with the principle of optical interference detection, puts forward a measuring method for such components, the method by introducing a pyramid to realize high precision optical path, and according to the inner surface in the shape of different components, it can be divided into cylinder and circular arc surfaces, respectively, measuring scheme is designed. Then, according to the designed inspection scheme, the system is built separately for inspection. After the system is stable, the shape information of the tested part is obtained. After the system is stabilized, the shape information of the inspected part is obtained. The shape information of the inner surface of the ring element can be obtained after only one inspection.
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