Laser Dicing (Wafer Cutting) by Laser-Microjet® SYNOVA Innovative Laser Systems

Wafer Dicing Semiconductor Wafers are cut into individual chips (dies), a processing step in the so-called back-end semiconductor production. Cutting kerf Die Semiconductor Wafer Street March 2003 Laser Microjet Dicing

Today’s Technique: Sawing Sawing with abrasive diamond blades Diamond particles High-speed rotary blade Semiconductor Wafer March 2003 Laser Microjet Dicing

Problems with Sawing Chipping High residual stress (micro-cracks) Low speed Only straight cutting possible Un-adapted to thin wafers De-lamination Continuous wearing out of the blade High running costs Chipping Street The possibilities of abrasive cutting have reached their limits. March 2003 Laser Microjet Dicing

Conventional Laser for Wafer Dicing? Laser beam Laser light is characterised as light waves of equal frequency and phase, which can be bundled at high intensity on account of their negligible divergence. Focusing lens Cutting gas The focused laser beam heats material to temperatures of several thousand degrees, causing it to melt and/or evaporate. Focus Workpiece An additional gas-jet expels the molten material from the cut. March 2003 Laser Microjet Dicing

The Failure of the Conventional Laser Profound thermal effects upon silicon give rise to cracks and structural changes, such as burrs and deposits on the wafer surface. Thermal damages Contamination Example of a conventional laser cut March 2003 Laser Microjet Dicing

New Lasers for Wafer Dicing? Lasers with short wavelength (UV lasers) and short pulse (switched lasers) reduce heat damage and contamination Problems: Although reduced, contamination and heat damage persist Low speed due to low laser power Short pulse UV lasers allow thermal damage and contamination reductions, inherent in laser cutting, but at the expense of reduced productivity. March 2003 Laser Microjet Dicing

The Solution: Laser Microjet® (LMJ) Dicing The Laser Microjet ® dicing technology applies a water jet guided laser, allowing high speed and high quality. The problems of heating and contamination are solved by the simultaneous use of the water jet which conducts heat away from the material before the heat can damage it. Example of a water jet guided laser cut March 2003 Laser Microjet Dicing

The Advantages of Laser Microjet Dicing No chipping No mechanical damage (cracks), high fracture strength Ideal for thin wafers Omnidirectional cutting (any shape can be cut) High speed No tool wear, low running costs March 2003 Laser Microjet Dicing

No Chipping The force generated by the water jet is very low, because the diameter of the water jet is very small. As a result, the mechanical force is negligible. Ablation is by absorption of laser light and heating. The result is a force free, non-mechanical cutting, which avoids completely the chipping of the edges. Sawing Laser Microjet ® Dicing March 2003 Laser Microjet Dicing

High Fracture Strength The absence of heat penetration into the material prevents micro-cracks and generates a high fracture strength A european chip manufacturer compared the fracture strength of 100 micron thick silicon wafers diced with LMJ technology against those with abrasive blade sawing Force Force Silicon Chip Fracture Strength Average Force Beam Bending Test Ball Bending Test 3.68 N Saw 27.46 N 5.83 N LMJ 41.48 N The LMJ diced chips have significantly higher fracture strength than sawed chips. March 2003 Laser Microjet Dicing

Example: 100 micron thick memory chip diced by LMJ Ideal for Thin Wafers Wafers are thinned for stacked chips, smart cards, and smart labels in order to save volume or to reach mechanical flexibility. Thin wafers are presently between 50 and 150 microns thick. In the future, thicknesses of 25 microns and less will be used. Example: 100 micron thick memory chip diced by LMJ March 2003 Laser Microjet Dicing

Omnidirectional Cutting The LMJ dicing allows for cutting in any direction due to its point-like tool. Slots Holes Contours T-cuts March 2003 Laser Microjet Dicing

High Speed In the case of thin wafers, the LMJ dicing is faster than the saw 50 100 200 300 500 700 1000 1500 2000 LMJ Cutting speed [mm/s] Throughput of 50 m wafers 15 wafers/hour 3 wafers/hour Sawing speed Saw LMJ Wafer thickness [micron] The typical speed of a saw is 60 mm/s, but the real cutting speed is only 40 mm/s as the saw makes a return without cutting, contrary to the LMJ which can cut in any direction. The thinner the wafer is, the greater the advantage is in the throughput. March 2003 Laser Microjet Dicing

Low Running Costs The LMJ technology has significantly lower, running, hourly costs than sawing. In the case of thin wafers, the high throughput allows substantial cost savings. 8.38 €/h Investment 16.00 €/h Cost of Ownership 6.80 €/h Consumption DI water 0.23 €/h Saw LMJ 8.33 €/h Consumption Blades 0 €/h 0 €/h Consumption Lamps 1.20 €/h 0 €/h Consumption Glasses, Nozzles 0.64 €/h 0.20 €/h Consumption Electricity 0.90 €/h The Complete Cost of Ownership Comparison, made with a european chip manufacturer, is available. 1.56 €/h Consumption Gas 0.66 €/h 1.23 €/h Cleanroom Costs 1.32 €/h 11.39 €/h Operator costs 6.83 €/h 37.89 €/h Total running costs 27.79 €/h Need of equipment for 50 m wafers 5 machines 1 machine Cost saving per year with LMJ -1.3 million € Cost saving after 5 years -6.5 million € March 2003 Laser Microjet Dicing

The LaserTape® For the Laser Microjet Dicing an optimal tape has been developed. The so-named LaserTape® is ideal for the LMJ dicing. Uneffected by the laser, the basic film is transparent and porous, allowing the water jet to pass through without tearing. The LaserTape® has a UV-curable adhesive, making it ideal for thin wafer dicing, due to the adhesive strength reduction after UV curing. The LaserTape® can be utilised in taping machines, and in pick-and-place machines. The LaserTape® is available in two different back films and in various adhesive strengths. The LaserTape® is manufactured and distributed by Furukawa (Japan) March 2003 Laser Microjet Dicing

New Technology Opens New Possibilities In the future, chip designers will have entirely new possibilities benefitting from unlimited chip shapes. Round chips, hexagonal chips, different chip sizes on one wafer, any geometry is possible. Chips of the future will be adapted to the requirements of emplacement. Example of wafer cut into round chips March 2003 Laser Microjet Dicing

The Future of Laser Microjet Dicing Reduction of kerf width 25 microns and less Increasing of cutting speed of up to 1000mm/s 25 mm 1000 mm/s March 2003 Laser Microjet Dicing

The Laser Dicing System March 2003 Laser Microjet Dicing

Laser Dicing Video March 2003 Laser Microjet Dicing