applications sEMiconDUctor procEssinG
Cutting costs with chips
Pressure to lower costs has always been a driving force of new techniques in manufacturing, but few industries are under quite as much pressure as semiconductor manufacturers. stephen Mounsey discovers the ways in which laser processing is driving development
M
odern businesses come in all shapes and sizes, from lone traders to multi-national corporations employing hundreds of thousands of people. One constant running through businesses of all sizes is the desire to maximise revenue while minimising costs. At fi rst glance, the semiconductor industry seems to have mastered this principle; what could be more profi table than taking a quantity of the second most abundant element on the surface of the planet, processing it, and selling the resulting component for thousands of pounds per gram? Unsurprisingly, silicon of the purity required for semiconductor manufacture is costly, and so manufacturers are keen to adopt any new technique that can reduce waste. Laser processing looks set to replace many dated mechanical techniques, and some novel and innovative laser processes even look set to replace their older laser-based counterparts.
Semiconductor components are produced
on circular wafers of silicon around 100µm thick and eight to 12 inches in diameter, with hundreds of integrated circuits or LEDs built on each. The process of cutting out the individual components is known as dicing, and it’s an area in which laser processing has
10 ElEctro optics l MARCH 2011
proven useful to manufacturers. Craige Palmer, a sales director at Hamamatsu, explains the attraction: ‘The existing technology normally used in these applications is blade dicing – a sawing process to dice the wafers. The problem is that it causes a lot of regional mechanical damage to the wafer. Where the cut is made, the silicon suffers an effect we call chipping. Laser produces a cleaner cut.’ This cleaner cut means that no dust is introduced into the processing environment and no water or lubricant is needed. The process is also much faster than sawing, he adds, achieving cutting speeds of up to 300mm/s, compared to 80mm/s for sawing. While quicker wafer processing means
greater profi t margins, and while removing airborne dust from the working environment is a plus, Palmer notes that materials costs are a signifi cant motivation: ‘The main advantage is that more of the wafer can be used. Not only do we not get the chipping caused by sawing, but we can achieve much narrower cutting widths.’ Hamamatsu’s ‘stealth’ cutting technique can achieve a cutting loss of less than one micron, whereas a conventional blade would cause a cutting loss of 40µm or more.
Ralf Schmidt, manager of semiconductor sales at Rofi n-Sinar Laser, highlights some
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