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November 30, 2009

Introducing the Gettering DP Wheel, a New Solution for Wafer Ultrathin Finishing: Maintaining the Gettering Performance through the Dry Polishing Process

DISCO Corporation (Head Office: Ota-ku, Tokyo; President: Kazuma Sekiya) has developed the Gettering DP wheel. This new solution in the dry polishing after rough and finishing grinding in the production of extremely thin wafers will be displayed at SEMICON Japan, held in December.

Development Background
In the field of memory devices represented by flash memory and DRAM, die in SiP (system in package) are becoming thinner, and the needs for thinning other devices, such as logic and RF chips, have also increased.
In the conventional backgrinding, a silicon wafer is processed in a brittle mode, so that subsurface damage is produced. This post-processing distortion causes wafer cracking and chipping during die bonding after dicing. At present, the stress relief process using dry polishing or CMP (chemical mechanical polishing) is commonly used in order to eliminate this subsurface damage and maintain die strength.
However, in the existing stress relief method, a sufficient gettering effect*1 cannot be obtained at the time of thinning to less than 50 µm, and therefore in some cases a new problem of characteristics distortion occurs due to heavy metal contamination*2.
The Gettering DP wheel has been developed as a solution for this new problem.


The gettering effect is a mechanism that forms crystal defects or distortions (= gettering sites) inside the silicon wafer (bulk or backside) and then captures impurities in these gettering sites.



Device destruction due to heavy metal contamination, which occurs with the inability to secure the gettering effect, is different depending on the device material and other conditions.

Features of the Gettering DP wheel
<Gettering performance equal to the normal grinding>
Thanks to a newly developed pad, the Gettering DP wheel maintains a gettering performance equal to the finishing by a grinding wheel.
<Eco-friendly process>
The Gettering DP wheel realizes a chemical-free process, which has less environmental impact, and enables thin wafer polishing much easier than the process using slurry.
<High die strength>
The Gettering DP wheel provides high die strength while maintaining the gettering performance, taking advantage of the expertise in the dry polishing process that DISCO has acquired.
<Usable as the final finishing wheel of the fully automatic grinder/polisher DGP series>
The same as the existing dry polishing wheels, the Gettering DP wheel can be installed as the final finishing (Z3-axis) of the DGP8761 or DGP8760, which has been widely accepted.
TEM comparison of wafer damage

Gettering DP Wheel

#2000 Wheel
Die strength comparison (measured by the ball-ring bending test)
Gettering effect
TXRF (total reflection X-ray fluorescence) measurement data before and after Cu solution application (φ8" mirror wafer)
Wafer polished by the Gettering DP wheel
Mirror surface before contamination After contamination and diffusion
Mirror wafer (assuming the stress relief surface)
Mirror surface before contamination After contamination and diffusion
The amount of Cu precipitated onto the polished surface of a mirror wafer sample after applying a copper solution exceeds 1.0 E11. In contrast, the amount of Cu precipitated onto the polished surface of a Gettering DP sample is below the detection limit (0.5 E10 atoms/cm²), thus indicating that the surface had a gettering effect.

Unveiling at SEMICON Japan 2009


December 2009

Starting sample shipments


January 2010

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