New Laser Technology for Fragile Materials

November 27 [Mon], 2017, 17:14
Cost, quality, yield are the key success factors for the semiconductor and photovoltaic manufacturing industries. Among them, an important processing method is cutting, because the need to use different cutting process to separate the wafer into a die or the solar cell into a half-cell. However, the conventional mechanical or laser-based cutting techniques have more or less disadvantages such as particle formation due to material removal or material damage at the cutting edge.

In this case, TLS-Dicing becomes a fast, clean, easy-to-use and reliable method for separating semiconductor materials such as silicon (Si), silicon carbide (SiC), germanium (Ge) and gallium arsenide (GaAs) Cost-effective alternative solution. Depending on the application, starting with the initial scribing process, the material is then high power laser heated according to carefully calculated energies. The material is heated and expanded, the pressure in the heated zone rises, and the tensile stress around the heated zone also increases. Immediately after laser heating, a very small amount of deionized water is sprayed for cooling (less than 10 ml / min). This will create a second cooling zone near the first zone, causing a tangential tensile stress mode. Tensile stresses generated in the superposed area of the two stress modes cause the material to crack and guide the crack tip through the material.

Compared with traditional cutting technology, the heat laser beam separation technology shows many advantages, such as fast separation speed, very smooth side wall, no cracks and micro-cracks, excellent bending strength and no tool wear and material consumption Low cost of ownership. The process uses two laser sources: a Gaussian beam short pulse scribing laser (532 nm or near-infrared wavelength laser) for initial scribing and another cutting green laser pointer. Cutting lasers enable 200W continuous wave laser and near infrared wavelengths. Thermal laser beam separation technology is a non-cutting cutting process, the process itself produces almost no particles.

Traditional cutting techniques have some drawbacks in terms of processing speed and cutting quality. For example, mechanical sawing feeds slowly, blades wear large, and costly. In addition, sawing tends to cause chipping on the edge of the wafer and delamination. In contrast, laser ablation produces a significant heat-affected zone, resulting in poor edge quality and the formation of micro-cracks. At the same time, the laser ablation rate is very low, requiring multiple ablations to complete the singulation of a single wafer. Compared with the above processing methods, the heat laser beam separation technology is a one-time process that can complete the thickness of the SiC wafer 300mm / s separation. In addition, the metal structure on the front-end cut tracks, the polyimide on the wafer, and the backside metal are both successfully separated without delamination or thermal effects.

In general, thermal burning laser pointer separation is an entirely new and efficient way to segment brittle semiconductor materials used in the semiconductor and photovoltaics industries. It offers the advantages of high yield, low cost, and high quality partitioning, often with a single separation. The feed rate of this process is between 300 mm / s and 500 mm / s, depending on the application.
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