DISCO Corporation can look back on over 70 years of experience in the field of abrasive technologies and is the leading company for KIRU (Dicing), KEZURU (Grinding) and MIGAKU (Polishing). The need for more precise cutting, grinding and polishing of different material like silicon, glass or ceramics increases. Irrespective of the material, DISCO takes up every challenge to realize the best solutions for its customers. DISCO always works on the technologies in dicing and grinding ultra thin wafers, Dicing before Grinding, and Stress Relief process.
Dicing saws use dicing blades to cut silicon, glass, and ceramic workpieces with a high degree of accuracy. Fully automatic dicing saws can perform the entire process sequence: loading from the cassette, alignment, dicing, cleaning/drying and unloading to the cassette completely automatically. The dicing saw automatic performs loading, alignment, dicing, washing/drying and then reloading of the workpiece back into the cassette.
|Workpiece is removed from thecassette and placed on to the chuck table.||Cutting line is detected.||Cuts the line detected during alignment.||While the workpiece is rotatedat high speed, it is washed withdistilled water and dried with air.||Workpiece is returned to the cassette.|
Grinders can thin silicon wafers, compound semiconductors, and many other types of materials with a high degree of accuracy.
Processing for applications which use the DBG system or DAF (Die attach film) is also possible by incorporating a polisher and wafer mounter with the grinder into an inline system.
Disco Laser Dicing
Laser saws make use of the characteristics of lasers to achieve high speed, high accuracy, and high quality processing of composite materials and difficult-to-cut materials.
Compound semiconductors, such as GaAs (Gallium Arsenide), are used in high frequency devices. When blade dicing compound semiconductors with an existing diamond blade, the feed speed is slow and high productivity is difficult to obtain.
With the trend towards high integration, based on such technology as SiP (System in Package), high-strength thin-die manufacturing technology has become necessary. However, with blade dicing, as the thickness of the wafer becomes thinner, dicing difficulty increases.
To solve this kind of issue, DISCO has optimized the laser head and optical system of the DFL7160 laser saw to establish a laser full cut application.
Grinder/polishers can complete every step of the process from wafer backgrinding to dry polishing on the same chuck table for high stability processing to very thin finish thicknesses.
Support for applications which use the DBG system or DAF (die attach film) is also possible by incorporating a wafer mounter with the grinder/polisher into an inline system.
The DGP8761 is the successor to the DGP8760, which is used by premier manufacturers worldwide. It integrates backside grinding and stress relief processing and performs stable thin grinding to thicknesses less than 25 µm. The DGP8761 is equipped with a newly developed spindle to support high-speed grinding. This contributes to a shorter thin wafer processing time (compared to the DGP8760). In addition, an optimized handling layout shortens the cycle time (not including processing time).
The following Z3 spindle configurations for thin wafer processing can be selected:
- Dry polishing – an environmentally friendly process without chemicals or water
- CMP (optional)
Super fine grinding (optional)
Laser Full Cut Dicing Process
The process involves feeding the laser over the front side (pattern side) of a thinned wafer (less than 200 µm) once, or irradiating the wafer multiple times until a cut is made to the tape. Laser full cut dicing can improve throughput because the feed speed can be increased.
– Thin wafer dicing of the GaAs compound semiconductor
During dicing, breakage and cracking can easily occur in the GaAs wafer because the material is very brittle. Therefore, it has been difficult to increase the feed speed using existing blade dicing. With laser full cut dicing, it is possible to process at feed speeds ten times faster than blade dicing, and thus increase throughput. (This is just an example. The actual speed depends on the wafer to be processed.)
By employing laser full cut dicing, it is possible to realize a reduction in the street width because the kerf width after processing is narrower and the kerf loss compared to blade dicing is less. Compound semiconductors wafers, which tend to have more processing lines to singulate into small die, can increase the number of dies that can be produced from one wafer, by realizing a reduction in the street width.
What is stealth dicing?
“Stealth dicing” is a dicing method that forms a modified layer in the workpiece by focusing a laser inside the workpiece, and then a tape expander is used to separate the die.
Stealth dicing illustration
Before tape expansion After tape expansion
Merits of stealth dicing
•Able to suppress cutting waste because it modifies an internal portion of the workpiece. Therefore, it is suitable for workpieces that are vulnerable to contamination.
•It is a dry process that does not require cleaning, therefore it is suitable to processes (such as MEMS) that are vulnerable to load.
•Greatly contributes to street reduction because the kerf width can be made narrow.
Stealth dicing example
The profile of a MEMS die, such as one with a hollowed structure, or one that is already embedded with complicated minute elements, is generally not strong enough for cleaning water or the dicing load. Stealth dicing can be expected to result in high-quality processing of MEMS because it does not use water for processing or cleaning, and there is little or no damage to the die front or back surfaces.
MEMS photograph after stealth dicing
Stealth dicing is expected to increase the number of die that can be obtained from a wafer compared to normal dicing because it is possible to make the necessary street width (cut width) narrower. This is a particularly effective processing method for long shaped die, such as line sensors.
Comparison of the number of die that can be obtained from one wafer :
The number of die obtained from one wafer increases by reducing the street width on a wafer with long-shaped dies.
A Hasen Cut is a method that cuts while repetitively turning the laser ON/OFF at a set cycle during laser processing. It is possible to process various shapes depending on the ON/OFF setting.
Hasen Cut application example
– Systematic complex die size wafer cut
By using the Hasen Cut, it is possible to process a wafer with combinations of irregular die shapes that could not be realized with the existing laser full cut processing or a blade dicer.
– Processing irregular shaped die
This cutting method can efficiently process workpieces like polygon shaped die, such as hexagons and octagons. Depending on the conditions, it is also be possible to process irregular shaped die.
Photograph of a hexagon die process
– Die offset processing
By applying the Hasen Cut, the dicing street can also support intermittent die layout, as shown in the illustration below. This is effectively useful for large die sizes, high-priced wafers or long die, and enables increasing the number of die that can be obtained.