Download - Meeting Microcool LHCb
Meeting Microcool LHCb
Status update 28.03.2012Tushant Singh
Wafer Status - Fabrication#3426 #3694 #3427 #3434 #3442
Sphagetti Problem Yes Yes No No No
Bonding To be analysed with EDX* and cleaned thereafter
To be analysed with EDX* and cleaned thereafter
Ready for bonding
Bonded Bonded
Inlets -- -- -- To be done Inlets etched
Dicing -- -- -- -- To be done
*EDX = Energy-dispersive X-ray spectroscopyTo be done at CSEM Neuchatel on 2nd April
Sphagetti Problem – Recall
Wafer#3426
White colored ‘Sphagetti’ observed coming out of the channels
Oxide strip – wet etch (BHF)
SEM pictures
SEM pictures of structures were taken and this is what the side-walls of the channel look like.
Sphagetti Problem
Wafer with Sphagetti Problem #3694 Wafer without Sphagetti problem #3442
You can see dirty sidewalls and dirty surface in this picture
Sphagetti Problem
• Possible causes –– WE DONT UNDERSTAND, but the guess is :• Contamination in dry etch machine• Contamination in wet etch bath
For now we are not observing any such problems
Surface Roughness Problem
• During SEM imaging for looking at Sphagetti problem it was observed that the Wafer surface was very rough. – This could cause bad bonding.
Compare surface roughness (Top surface)
Wafer with Sphagetti problem #3694 Wafer without Sphagetti problem #3442
Surface Roughness Problem
• Preliminary investigations show that this problem is associated with wafers that had the Sphagetti problem.
• The wafer which did not have sphagetti problem looked OK in terms of Surface roughness.
• Further investigation needed with more wafers.
Further activities
• New batch of 3 wafers• Modified process flow – Slight modification in process flow has been
proposed and is under discussion with Alessandro.