TIAN Wentao, a master student of our center (first author) and Dr. Wang Zhiwen (corresponding author), published a paper entitled “Ethanol assisted laser dicing of silicon” in Infrared and Laser Engineering.

In order to reduce the thermal effect of laser dicing of silicon wafer, deionized water was used as assistant material to dice the silicon wafer. However, bubbles emerged during laser ablation and led to adverse effects. Ethanol was mixed into deionized water to decrease the number of bubbles adhering on the surface of silicon. The impact of laser parameters and ethanol concentration on dicing quality were analyzed.

The results of experiment showed that the usage of ethanol as the assistant material can decrease the number of bubbles adhering on the surface of silicon and alleviate the negative effect of bubble collapse. The kerf width decreased by 20 % and the area of affected zone decreased by more than 50 % when ethanol concentration was 5 wt.%. The dicing quality was improved effectively.

Fig.1  Surface of silicon diced under water: (a) Silicon surface affected by bubbles; (b) Enlarged optical image of area B; (c) The first enlarged optical image of area A; (d) The second enlarged optical image of area A

Fig.2  Optical images of front surface diced in different ethanol-water mixtures with ethanol in water of 0 %, 2 wt.%, 3.5 wt.%, 5 wt.% (a-d)

Fig.3  Dynamics of laser-induced bubble: (a) Under water; (b) Under ethanol solution

Fig.4  The relationship between pulse and bubbles: (a) Under water; (b) Under ethanol solution