Part 5: Metrology for Wafer Dicing

Series: Advanced Packaging - Multi-Sensor Metrology for Every Process Step

In the fabrication of integrated circuits, wafer dicing is the process by which the die is separated from a semiconductor wafer after processing. The cutting process can be performed by scratching and breaking, mechanical sawing or laser cutting.

For dicing, the wafers are typically mounted on a tape and fixed to a thin sheet metal carrier frame. Once a wafer has been cut, the pieces remaining on the tape are called dies. They are encapsulated in a suitable package or placed directly on a printed circuit board substrate as "bare die". The cut-off areas, the so-called die-streets, are usually about 75 μm in width. Once a wafer has been diced, the die remains on the tape until it is further processed by a die bonder or die sorter in the assembly process. The size of dies remaining on the tape can range from around 35 mm to less than 1 mm. The dies produced are typically rectangular or square, in some cases they have other shapes depending on the separation method being used.

The dicing of silicon wafers can also be performed using a laser-based technique known as stealth dicing. It works as a two-step process in which defect areas are first introduced into the wafer by moving the laser beam along the intended cutting lines and then a carrier membrane underneath is expanded in order to induce a fracture. The advantage of the stealth dicing process is that no cooling liquid is required. For the production of certain microelectromechanical systems (MEMS), dry cutting methods must be used, especially if they are intended for bioelectronic applications. In addition, stealth dicing produces minimal deposits and enables better utilization of the wafer surface through lower cutting losses than mechanical sawing.

A good dicing process with high precision and perfect repeatability determines the quality and speed for all remaining post-fab operations.

In order to ensure that your dies have a consistent geometry after the dicing process and no defects such as edge chippings and cracks, an inspection after this process step is mandatory.

The flexible and modular multi-sensor measuring tools of the MicroProf® series offer optical and non-contact innovative solutions in the field of wafer dicing for production and R&D. Where other systems reach their limits, the measuring tools of the MicroProf® series meet the continuously increasing challenges of production parameters, process control and quality assurance.

With our 3D surface measuring tools of the established MicroProf® series, surface measurements as well as single and multiple profiles can be performed without contact. There is the possibility of automated mapping of the samples as well as the execution of evaluation routines. Roughness, even on transparent layers, can be determined down to the sub-nanometer range and topography measurements of die streets and cutting edges can be performed.

Another domain of our measuring tools is the film thickness determination of coatings, e.g. insulating and protective layers, in the form of thin layers or layer stacks. Layer thicknesses down to a few nanometers can be determined with a resolution in the sub-nanometer range.

A further application is the measurement of defects after the dicing process. Defects are e.g. edge chippings and cracks which can occur during the separation process.

All tools of the MicroProf® series offer a complete topography and TTV analysis. A fully automatic EFEM (Equipment Front End Module) also supports the processing of thin wafers. Thanks to the multi-sensor concept, the measuring tools can be retrofitted at any time with various sensors, e.g. IR sensors for coating thickness determination. An IR microscope for capturing transmission images for optical, non-contact and non-destructive 2D analysis of hidden structures in near-infrared (NIR) transparent materials can also be integrated. A combination of different measuring tasks in one measuring tool is therefore possible without problems. 

Whether laboratory, development, quality assurance or production - FRT offers the suitable measurement technology for your application from Advanced Packaging. Do not hesitate to contact us if you have any questions. Our experts will be glad to help you solve your measurement tasks by creating the best possible system configuration for you.

Interested in latest posts of this series? Click below.

Part 1/8: Metrology for Semiconductor Lithography

Part 2/8: Metrology for TSV Fabrication

Part 3/8: Metrology for RDL, UBM and Solder Bump Fabrication        

Part 4/8: Metrology for Carrier Bonding/ Debonding, Backside Thinning and Nail Reveal

Part 6/8: Metrology for 3D Chip Stacking

Part 7/8: Metrology for Molding of 3D Chip Stacks

Part8/8: Metrology for Every Process Step in Advanced Packaging

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