A rational ice-skater will always choose a smooth and perfect ice surface over one full of pits and cracks, as the latter will undoubtedly be weak and dangerous. Similarly, as semiconductor die become thinner and thinner, the dangers of backside chipping—analogous to cracks in thin ice—are also growing. To solve this problem, Disco offers the Dicing Before Grinding process, which can significantly reduce backside chipping and thereby increase overall die strength.
Backside Chipping
In the conventional dicing after grinding process, the wafer is fixed on a dicing frame with tape and cut fully (and slightly into the tape) to effect die singulation. Because fully cutting the die places stress on the die backside, backside chipping results.
In the DBG process, however, the wafer is first grooved (half-cut), then ground with a precision grinder. It is during the grinding step that die singulation occurs. Because a full cut of the wafer is not necessary, pressure on the wafer backside during dicing is greatly lessened, and backside chipping thereby significantly reduced.
Die after standard process Die after DBG
With DBG, backside chipping and cracking is significantly reduced
The Dangers of Backside Chipping
Die strength is measured by a test in which increasing amounts of pressure are placed on the die until its interior stress intensity is so great that it breaks. Die strength is determined primarily by the following three elements:
1. The strength of the wafer (including crystal orientation and presence of defects)
2. Effects of grinding on the wafer (saw marks and damage layer)
3. Effects of dicing on the wafer (backside chipping)
A die with significant backside chipping is similar to a sheet of ice with pits and cracks: In either case, catastrophic breaks can originate from what appear to be minor flaws in the surface.
Advantages of the DBG Process
In the DBG process, die singulation occurs during grinding instead of dicing. For this reason, there is almost no stress placed on the die backside during the dicing stage. In addition, because DBG employs grooving (half-cutting) during dicing, measures used to reduce backside chipping in the conventional process (step cutting, bevel cutting, etc.) become virtually unnecessary, and throughput is also significantly increased.
Today, even as finished die become smaller and thinner, the wafers from which they are made are growing larger to improve productivity. As a result, backside chipping presents a bigger problem than ever before. DBG not only reduces backside chipping, but can be combined with a stress relief process for even greater die strength and quality.
Die backside after conventional Die backside after processing with DBG
processing plus etching
（Both images have been magnified 30x）
