Research On Pulsed Laser Pitting Separation Of Glass Materials

The demand for ultra-thin wafers in semiconductor production continues to grow.However,in the current manufacturing process,the cutting process will cause a 50%waste rate of crystal material.In order to improve material utilization and cut ultra-thin wafers,a new way of wafer slicing using laser slicing technology instead of mechanical processing technology is explored.Laser processing has advantages over mechanical processing because it is a non-contact process that can reduce machine vibration and tool wear caused by traditional mechanical processing.At the same time,the heat-affected zone formed by laser processing is very small,which can meet the processing requirements of ultra-thin wafers.The laser slicing method is mainly composed of two steps.The first step is to focus the laser at a specific depth of the substrate,define the laser scanning path,and form a scanning mark,and then connect a single laser processing line in the plane to form a modified layer.The second step is to divide the crystal into two parts from the modified layer to achieve wafer peeling.In order to reduce the cost of the experiment,this paper studies the nanosecond laser separation method of glass through laser single point simulation,glass modification layer formation experiment and peeling experiment.Based on the theory of heat transfer and thermoelastic mechanics,a single-pulse laser heat conduction model was constructed in the finite element software ABAQUS,and the body heat source model was established using the FORTRAN subroutine interface,and the temperature field simulation of a single point mark was completed,corresponding to a single point ablation The thickness of the modified layer in the experiment has an error of about 7.5%,which verifies that the temperature field simulation model of the single-point mark is reliable.The analysis of the stress field formed by a single pulse laser shows that tensile stress is formed at the focal depth,and the adjacent upper and lower ranges form compressive stress.The maximum compressive stress reaches 278Mpa and the maximum tensile stress reaches 49.1Mpa.The stress field simulation results prove that the laser generated material The modified layer facilitates the subsequent peeling process of the sliced material.Under different laser parameters such as laser power,dot spacing,and number of repeated dots,the damage characteristics of the material formed by processing a single straight path inside the glass were studied through experiments.The experimental results determined the range of laser processing parameters that produced qualified modified layers.For different laser pulse energy,it is necessary to correspond to the value of the limit point spacing and the number of repetitions.Plexiglass and borosilicate glass were selected for peeling experiments on a universal testing machine.The experimental results showed that the separation surfaces of the two types of glass were expanded in the modified layer.The smaller the thickness of the modified layer processed by laser,the roughness of the separated surface.The smaller.Among them,after the high borosilicate glass is peeled off,the roughness of the separated surface reaches about 3.9μm,which is much smaller than the surface roughness of the material cut by the ordinary wire saw,which proves that the use of laser for slicing brittle materials has a good research prospect.