Research On The Orientation Accuracy And Damage Layer Thickness Of Silicon With Specific Crystallographic Plane Cut By WEDM

With the rapid development of modern science and technology, the diffraction crystal made of the single silicon with specific crystallographic plane has been widely used in the field of high technology, such as neutron scattering spectrometer, hard X-ray calibration device, et al. When machining the large size of the silicon crystal with specific crystallographic plane by WEDM, the surface of the silicon wafer is not the ideal plane, and the crystal orientation error of each point is different from that of the ideal plane, so we need measure the whole crystal orientation error of the silicon. At the same time, because of the large size of silicon and small size of the loading stage, we can only obtain the accuracy of some point on the crystal surface, the measurement is difficult, time consuming, and the measured accuracy is not very good. In addition, there will form a damage layer when machining the silicon by WEDM, it is difficult to measure the thickness of the damage layer on the surface of the silicon accurately. In this paper, we take the method to measure the orientation error of each point by combining the orientation error of the single point with the surface contour of the silicon, and to measure the thickness of the damage layer on the surface of silicon machined by WEDM by X-ray rocking curve. Furthermore, in order to reduce the depth of the surface damage layer and improve the accuracy of the surface, the multi-cutting by electrical discharge machining about metal material is applied to the machining of the single crystal silicon in this paper. Major works:(1) For the large size of crystal silicon, the surface of the diffraction crystal is not an ideal plane, and the orientation error of each point is different. In this paper, we take the method to measure the orientation error of each point by combining the orientation error of the single point with the surface contour of the silicon, and the results are in agreement with theoretical analysis.(2) Producing silicon wafer surface with a high integrity is an important part in the production of semiconductor. In the process of processing the silicon wafer by WEDM, there will form a damage layer composed by pits, micro crack, elastic distortion, dislocation and so on. In this paper, the surface damage depth of the silicon wafer is measured by the method of X-ray rocking curve and etching on the aspects of the measurement principle, the different crystal orientation and the different energy, etc.(3) The thickness of the damage layer and the discharge gap of the single crystal silicon machined by WEDM are studied. According to the analysis, the parameters of the reasonable compensation value of the multi-cutting are got. Experimental results show that the high efficiency and the high quality surface of the single crystal silicon can be got by using the multi-cutting of WEDM. Under the same surface quality, it can greatly shorten the processing time, and simplify the follow-up process.(4) This paper studied the influence of the multi-cutting technology by WEDM on the accuracy of the crystal orientation when processing the silicon wafer with specific crystallographic plane. When cutting large size of single crystal silicon, it not only improves the surface quality of the silicon wafer surface, but also improves the accuracy of orientation on the wafer surface and wakens the fluctuation of the orientation error on the silicon surface.