The Research Of Water Guide Laser Cutting Wafer Pre-alignment And Water Guide Laser Coupling Technology

In recent years, the market demand for micro-chip is growthing rapidly withthe rapid development of the semiconductor industry manufacturing technology.The chip size and thickness requirements continue to decrease, the wafer as theraw material of integrated circuit (IC), which also increases the substrate size,reduces the thickness and refines the line size. The micro-cutting technology hasbeen faced great challenge, even the traditional cutting technology already can'tmeet the narrow cutting requirements. Later, a new kind of cutting technologywith powerful advantages for small heat-affected zone, the melt can be removed,good processing quality, speed faster etc., water guided laser cutting technology,have been born at the right moment. In this paper, a in-deepth research on thewafer pre-alignment technology and the water guide laser coupling technologyincludes the following main aspects.The wafer pre-alignment system is to ensure the correct wafer cuttingdirection and precision. According to analyze the functional requirements anddesign the structure, then complete to build the hardware platform, whichincludes vision system and motion control system in detail, respectively. B asedon the visual image processing technology, establish the correspondingrelationship between the machine coordinate system and the image pixelcoordinate system. Using the MATLAB to develop the wafer pre-alignmentsoftware program, which mainly contains image enhancement, edge detection,linear fitting, circle fitting, flats or notches detection and coordinatetransformations, etc. At last, calculate the position and angle deviation betweenwafer center and platform center to provide accurate compensation data duringwafer cutting.As the core technology of the water guided laser cutting, the couplingtechnology mainly includes two aspects of difficulties, water beam stability andlaser beam transmission limited in water beam. Nozzle and coupling device havebeen modeled and meshed by GAMBIT software, set reasonable boundaryconditions to simulate the water beam in air and the flow field's uniformity andstability inside the coupling device by FLUENT. The influence of water beamstability with nozzle structural parameters and inlet velocity of water jet beamhas been analyzed, the conclusion is that the longest stable length hascorresponding to an optimum inlet jet velocity. The simulation data will provideevidence for choosing reasonable water length in real application.After all hardware platform built, complete the experiments about calibration of the vision system and the wafer pre-alignment based on theproposed method. The results shows that the calibration of the vision system hasachieved sub-pixel accuracy and the wafer pre-alignment error could meet theneed of cutting within the error range.