EVGNEWS Issue 2 2016


Laser Debonding: Broad Process Window and High Throughput 

Laser debonding is based on low laser fluence to separate the device wafer from the carrier substrate. This technique enables force-free separation at room temperature while at the same time providing high debonding throughput. In particular, the availability of high-temperature-resistant materials, combined with debonding at room temperature, makes this technology an ideal solution for applications demanding process latitude such as Fan-Out Wafer-Level Packaging and Advanced Packaging. 

The latest addition to the fully automated EVG850 temporary bonding/debonding (TB/DB) equipment series is laser debonding, which makes this platform the most universal offering to support thin-wafer processing.

Laser debonding is an attractive option for several reasons, including the combination of force-free separation and high throughput. Additionally, adhesive materials can be used that offer extended sustainability for high annealing temperature or chemical treatments. This capability significantly increases the process window for debonding compared to other methods. EVG's process and materials know-how enables the implementation of any commercially available material to provide an optimized solution for a wide variety of requirements and applications. 

Common to all adhesive material systems is the high absorption in the wavelength regime of the debond laser. Thus, the carrier substrate has to be highly transparent to guarantee optimal results, and as a result glass wafers are typically the first choice. Debonding occurs within a few hundred nanometers of the adhesive close to the carrier wafer, which leads to at least several micrometers of adhesive between the debond line and the device wafer. Therefore, there is no risk of harm to the device wafer at any time. The separation mechanism within the adhesive is the breakage of chemical bonds in the polymer chains, which is not a thermal process and which leads to a debonding process at true room temperature.

Key features for EVG's Laser Debonding solution:

  • High-throughput debonding using field-proven excimer laser technology
  • Force-free separation after laser treatment
  • Debonding at true room temperature
  • No thermal stress subjected to the device wafer
  • Compatible with a wide variety of commercially available adhesives
  • High-vacuum-capable materials available
  • Debonding occurs very close to the carrier wafer resulting in no harm to the device wafer
  • Carrier recycling possible 

Capabilities and Requirements:

  • High-thermal-resistance up to 370°C
  • Carrier must be transparent to UV laser (glass, no Si)
  • High throughput - exact specifications determined by cleaning process
  • Build Up Packaging process compatible, e.g. RDL-first

Application for Laser Debonding:

  • Power Devices 
  • Fan-Out Wafer-Level Packaging
  • Interposers
  • MEMS

EVG ® Laser Debonding

Comparison of different debonding processes based on process temperature and temperature stability
(click to enlarge) 

Laser debonding principle
(click to enlarge)

Microscopic image of excimer laser exposure field
(click to enlarge)