Backgrind Tape

Backgrind tape is primarily used to protect the front side or device side of the wafer. Front side or device side is the side that will usually go through the front end process (patterning and etc) to create the circuits. It is crucial to protect the front side from damage. Since the tape is in direct contact with the front side, backgrind tapes will be the cleanest type of tape.

Like in the name, backgrind tape is applied prior to the grind or thinning step in the backend manufacturing process and can be removed when it makes sense in the process. It’s not uncommon for the grind tape to also go through some wet etch steps or clean steps.

To pick a backgrind tape, it is best to know what the constraints and goals are. For example, what is the final thickness after grind, are there any features that need to be encapsulated by the adhesive/tape, any thermal or chemical steps after grind?

From there we can start to down select which tape to use. We can break down grind tapes into two categories which defined by their method of removal.

Pressure sensitive adhesive (PSA) tapes are similar to your scotch tapes. These are low adhesion strength tapes that can be removed without any kind of additional steps. Generally speaking this will be the cheapest tape but if you are grinding down to the point where the wafer becomes fragile, using a PSA tape will cause the wafer to break when peeling off the tape.

To have a larger process window and address the issue with PSA, it is quite common to use tapes with a release mechanism such as a UV curable adhesive or heat release adhesive. What this means is that the tape will initially have a high adhesion strength and when one wants to remove the tape, we either expose it to UV light or to a certain temperature.

UV tapes are the most popular in backside grind due to its low post UV adhesion strenth and ability to encapsulate or conform to topography. On the front side of wafers, it is possible to have solder balls or copper pillars ranging from heights of a few microns to hundreds of microns. UV adhesive generally have the greatest ability to be able to handle these heights while still performing the necessary functions.