Wafer warpage is caused by imbalance of stress between the front and backside of the wafer.
Extreme warpage causes a vacuum leak during processing or dropped wafer due to insufficient vacuuming during handling. Warpage that occurs when the stress of backside grinding damage is larger than that of the front side is called normal warpage, which renders the wafer convex-shaped. On the other hand, concave warpage is called reverse warpage.

Here, the amount of warpage caused by grinding damage will be explained.

Diagram of warpage from grinding damage (warpage direction: concave)

Warpage amount from grinding damage (by abrasive mesh)

---