Laser dicing of silicon wafers has been in use for many years, and it is a growing application. As wafers become thinner, and as lasers become more powerful, the advantage of laser dicing increases dramatically. And naturally, this leads to the question: what is the best laser for the job?
The answer is not simple. For pulsed lasers with the same average power and repetition rate, the speed and quality of a dicing process can vary widely due to the strong influence of other laser characteristics such as pulse duration and wavelength. For example, while longer pulse widths and longer wavelengths will generally cut faster, they are also more likely to cause excessive melting and cracking. Alternatively, shorter pulse widths (ps, fs) and shorter wavelengths (UV, DUV) will offer the best quality result with minimal HAZ (heat affected zone) and higher die strength, but at a much higher cost and with lower system throughput. With these considerations, many in the industry have found short ns-pulse 355 nm Q-switched laser systems to be ideal for wafer scribing and dicing applications.
Today’s laser products offer ever-higher power levels, and this holds true even for short-ns pulse widths and 355 nm wavelength. With this trend, the challenge increasingly becomes utilizing this higher power and pulse energy as efficiently as possible. In Spectra-Physics’ Industrial Laser Applications Lab, we have examined experimentally the efficiency advantage of line-focus fluence optimization for thin silicon dicing. We have shown that even with the high-quality of short pulse and short-wavelength processing, exceptionally high cutting speeds are still possible, as highlighted in the table below.
|Wafer Thickness||Approximate Cutting Speed|
|25 μm||2000 mm/sec|
|50 μm||1000 mm/sec|
|75 μm||600 mm/sec|
|100 μm||375 mm/sec|
The low ablation threshold – which is a result of the short pulse width – coupled with line-focus fluence optimization offers the best of both worlds: high-quality of short pulse/short wavelength machining with industrial-scale process speeds.
Spectra-Physics is a leading supplier of lasers for the manufacture of semiconductors and LEDs. Our semiconductor lasers are proven in a wide range of semiconductor and LED applications including silicon wafer scribing and dicing. With thousands of UV lasers deployed in demanding semiconductor and LED applications, Spectra-Physics delivers a broad portfolio of highly reliable, cost-effective lasers backed by our industry-leading global support organization.
For additional information on semiconductor inspection and metrology as well as other semiconductor applications please download our free Semiconductor Devices and Process Technology eBook.