We have developed a new laser ablation process using a water-microdrop with a diameter of 70 m. The shapes of the debris were investigated at various delay times. A Q-switched Nd:yttrium-aluminium-garnet laser of 25 ns pulse width and 532 nm wavelength was used. The spattering of debris was remarkably reduced by using the water microdrop. The debris pattern was dependent on the shape of the microdrop on the wafer, which in turn was dependent on the surface condition of the wafer and the delay time. The use of a smaller microdrop would result in laser dicing with a small ridge at the rim of the ablation point and no debris. The flexural stress of 720 MPa was obtained near the blade dicing.
Market demand of information terminals for Internet of Things (IoT) is increasing. So market situation requires various semiconductor packages. Wafer Level Chip Size Package (WLCSP) is one of the most important technology among them. We selected stealth dicing (SD) as a manufacturing method for WLCSP because the cutting speed is higher than blade dicing and the yield of semiconductor chip is higher than blade dicing. But, SD process still has some technical issues. In some cases, when the laser is irradiated from circuit side (from surface side of Si wafer), the metal pattern in circuit might prevent the laser focusing. In this case, the laser should be irradiated from backside of Si wafer through dicing tape. We have already developed a transparency suitable dicing tape for the SD process, but the base film material of the dicing tape is poly vinyl chloride (PVC) which is not becoming to conform with some of recent environmental standard. Market situation requires poly olefin (PO) dicing tape because of global environmental consideration. We developed PO dicing tape for SD process through dicing tape by conducting various evaluations. In this study, we report details of the development process of novel PO base film dicing tape with the same performance as PVC base film dicing tape and successfully separated a 12 inch silicon mirror wafer into 1 mm die squares and 12 inch silicon mirror wafer with the back side protection-film into 6 mm die squares.
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