Improving yields with plasma dicing
Wafer dicing is generally carried out using conventional blade technology. However this method has limitations which can be overcome by using dry plasma etching.
Blade cutting can cause die chipping or cracking leading to lower yields. Also the necessary width of the blade removes valuable “real estate” from the wafer. Deep reactive Ion Etching (DRIE) is a dry plasma process which can etch very narrow, deep vertical trenches into silicon (known as dicing “streets”) to separate individual die.
In the DRIE approach, die are defined by partially etching the front side of a masked wafer up to a depth of approx 200µm. The wafer is then attached face-down to a dicing frame and the backside of the wafer ground away until singulation of the die occurs. (see below). This is known as “Dicing Before Grinding” (DBG).
Advantages of DRIE for DBG:
- All dicing streets are etched simultaneously, giving throughputs at least 2x times greater than sawing
- Unlike sawing, plasma dicing will not damage the wafer surface or trench sidewall giving higher die strengths and increased device lifetime and reliability
- The narrower street widths for plasma dicing free up real estate allowing increased die count on each wafer
- Non-rectangular die shapes can be created (i.e. defined by mask, not blade cut)
SPTS’ Mosaic™ Rapier DRIE systems have already been qualified at customer sites for this application, and offer reduced cycle times and lower manufacturing costs when compared to conventional mechanical dicing.
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