Application of the hottest fiber laser in silicon

Application of fiber lasers in silicon wafer processing

generally speaking, silicon wafers are cut by diamond saws, which can only rely on imported products. Occasionally, scribers and stripping processing are used, but scribers and stripping processing have certain limitations, they can only line straightly, and are easy to lack edges. With the continuous improvement and development of laser technology, more and more silicon wafer processing adopts laser technology. The main applications of lasers in the field of silicon wafer processing include cutting, engraving, punching and marking. At present, the main laser sources used for silicon wafer processing are frequency doubled YVO4 green light, ultraviolet light, etc., but the operation of frequency doubled YVO4 laser is time-consuming and expensive, which limits its application to a certain extent. With high beam quality, wide pulse frequency adjustment range and low cost, fiber lasers are increasingly developed rapidly in silicon wafer processing

spi fiber laser introduction

at present, SPI's products are mainly divided into two categories: continuous fiber laser and pulse fiber laser. Continuous fiber laser includes 25 ~ 400W series products, and pulse fiber laser includes 10 ~ 40W series products. Continuous fiber lasers are mainly used for silicon wafer cutting; Pulsed fiber lasers are mainly used for silicon wafer engraving, punching and marking

g3 pulse laser - different from the fiber laser based on Q-switch technology, SPI's 10 ~ 40W G3 (third generation) pulse laser adopts the main oscillation power amplification (MOPA) technology. Because its output frequency is determined by the frequency of seed light, and the frequency of seed laser can be directly controlled by electrical modulation, Therefore, the laser has two operation modes: continuous output (when the output of seed light is continuous output) and pulse output (when the output of seed light is pulse output). In the pulse mode, the 40W pulse laser has a heavy frequency range of 1 ~ 500KHz, a peak power of 20kW, a single pulse energy of 1.25mj, a pulse width of 10nm, and 25 built-in waveforms for selection. The parameters such as average power, peak power, pulse frequency and pulse width can be adjusted according to the application requirements, which greatly broadens the application range of G3 laser in the field of silicon wafer processing and greatly improves the processing efficiency

r4 CW laser system - SPI's CW lasers include 25 ~ 200W air-cooled CW laser and 100 ~ 400W water-cooled CW laser. The maximum modulation frequency is 100kHz and the output power stability is ± 0.5%

laser cutting wafer

SPI company recently invented a high-speed wafer cutting method that can obtain ultra-high cutting quality. Using 200W CW fiber laser at 200 μ Cutting on M (0.008 ") thick polysilicon at the speed of 10m/min can obtain a fairly smooth cutting edge without any cracks and a width of 40 μ M very parallel crack free notch. Even when the wafer thickness reaches 1.2mm (0.05 "), it can still achieve ultra-high quality cutting at a speed of more than 1m/min, which is comparable to other existing cutting methods. The data in Table 1 shows the competitive advantages of fiber lasers in silicon wafer cutting applications

at present, SPI is applying for a patent for this processing method. This method can achieve excellent cutting edge quality. Figure 1 shows the cutting quality obtained with a 50W CW fiber laser. Even when cutting patterned wafers, high-quality top edges can be obtained without any cracks (see Figure 2). This new cutting method can also be processed like the existing diamond cutting and sawing technology, and the cost of protection is low to produce a flat shape

table 1:spi continuous laser cutting parameters

figure 1:50w continuous laser cutting 250 m thick silicon strip, with a cutting speed of 2.5m/min

figure 2:200w CW laser cuts 0.8mm (0.03 ") thick wafer with circuit diagram, and the cutting speed is 3.5m/min

spi can also be effectively used for silicon cutting or scribing. With a 20W fiber laser, the parameters are set to a repetition rate of 65khz and a pulse length of 75ns, which can be in the range of 200 μ M thick wafer is cut at the speed of 200mm/min. This produces a cutting edge characterized by re solidified silicon nodules (see Figure 3)

Figure 3: sample cut by 20W fiber laser: 100 m thick silicon wafer, multiple times, effective speed 250mm/min, repetition rate 25kHz, pulse length 200ns

laser drilling silicon wafer

spi pulse laser realizes great flexibility through pulse waveform control, and can play a great role in drilling applications. Greater amplitude means greater peak power. The higher peak power and pulse energy provided by waveform wf0 can produce larger diameter holes. Changing the frequency, the peak power and pulse energy will change, and the aperture will also change. Therefore, the different aperture of micron can be changed by the frequency and pulse characteristics of the laser. Figure 4 shows several holes machined on silicon wafer by 20W fiber laser with different pulse characteristics

figure 4:20w pulse laser parameter setting: pulse frequency 500 kHz, waveform wf5 (above figure); Pulse frequency 25kHz, waveform wf0 (below). The aperture in the left figure is 25 μ m. The aperture in the right figure is 50 μ m。

it can be seen from Figure 4 that laser drilling can produce a wide range of aperture, which also shows the flexibility of SPI 20W pulse laser. Using 163mm focal length and 8mm input beam diameter, a good processing effect can be obtained

during the drilling process, the material is removed from the hole and the debris remains on the surface. However, debris tends to be less viscous and can be removed by ultrasound. The advantage of ultrasonic cleaning is that it is carried out in water, which is much milder than traditional acid cleaning

blind holes are sometimes used. This requires a smooth internal contour. Figure 5 shows a blind hole drilled on a silicon wafer with a 20W pulse laser

Figure 5: blind holes punched on silicon wafer with 20W pulse laser

laser marking of silicon wafer

20w HS pulsed fiber laser can be used to mark silicon. Requirements for scribing applications include narrow lines, low HAZ (heat affected zone), minimal surface debris, and no saw marks. At low repetition rate and high pulse energy, deep scratches will be generated, but the HAZ is higher and there are more debris. At high repetition rate and low pulse energy, the input heat can be better controlled, and the influence of HAZ and debris can be reduced accordingly. Although the marking is not deep enough at this time, the required depth can be guaranteed through multiple pulses. Figure 6 shows the scribing at different speeds (mm/s), using a 20W laser with a focal length of 163mm, a frequency of 25kHz, wf0 and an input beam diameter of 6.5mm

Figure 6: silicon scribing with 20W pulse laser at different speeds of 150mm/s, 175mm/s and 200mm/s

Figure 7 shows scribing on silicon with a 25kHz, wf0 and 500mm/s laser. The scratches have been cleaned by ultrasonic

Figure 7: groove silicon wafer with 20W pulse laser. Laser parameter setting: speed 500m, m/s with the change of living conditions, pulse frequency 25kHz, waveform wf0. Groove width is about 35 μ m。

laser wafer marking

20w HS can also be used for silicon marking. With low-energy pulses, smooth or even low evaporation marks can be obtained. Figure 8 shows the excellent effect of marking with a 20W, 375khz laser

figure 8: good effect achieved by marking with 20W pulse laser at 375khz pulse frequency

it can be seen from the above application examples that by setting different settings for the same laser and selecting different waveform, pulse frequency and other parameters according to the characteristics of the material, the material can be finely processed step by step, so as to obtain the best processing effect