Continue my previous journey of writing semicon life.
Today i wanna talk about the belljar coil.
This copper line that circulated around the belljar, is functioned to heat up the belljar and make it to etch the oxide more evenly.
If the belljar coil is misaligned like in the photo, especially after the PM after the belljar installation. Then we will encounter the etch rate cannot achieve issue.
You also need to have a scanner eye to be able to detect the coils is shorted together like above photo. This also will cause that area etch rate high , but other area will lower and uneven.
But this also require some experience in installing the belljar, as it's firmly and tightly circulate the belljar, very hard not touching each other and short it.
