Study on the process of silicon wafer marking with 532nm Nd: YVO4 laser

Abstract

Silicon wafers are the raw material for chip manufacturing, and the identification code is formed on the surface by laser engraving, which is an important part of the traceability chip management cycle. In this paper, the 532nm Nd: YVO₄ laser is used to build a laser marking system, and the stability and energy distribution of the laser light source are analyzed. The laser marking system is used to mark the surface of the silicon wafer with dot matrix, and the white light interferometer is used to analyze and measure the ablation pit at a single point, and the process effect of the system on the wafer marking is evaluated from the depth of the single point. In this paper, the process research of silicon wafer marking is carried out by changing the laser power, PRF (pulse repetition frequency), the number of laser pulse and defocus amount of the system. The research results show that: 1) 532nm Nd: YVO₄ laser has the highest energy stability at the maximum current and 20 kHz. 2) Under the condition that other system parameters such as power and repetition frequency remain unchanged, the depth of marking can be improved by increasing the number of pulses. 3) Under the condition that other parameters of the system such as the number of pulses and power remain unchanged, the balance between marking quality and marking efficiency can be achieved by optimizing the laser repetition frequency. 4) Under the condition that other parameters of the system such as power, PRF, and the number of pulses remain unchanged, there is a certain range of power. The change of defocus amount is the most sensitive, and with the increase of defocus amount, the dot depth and aperture first increase and then decrease.