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Meeting Microcool LHCb. Status update 28.03.2012 Tushant Singh. Wafer Status - Fabrication. *EDX = Energy-dispersive X-ray spectroscopy To be done at CSEM Neuchatel on 2 nd April. Sphagetti Problem – Recall. Oxide strip – wet etch (BHF). Wafer#3426.
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Meeting MicrocoolLHCb Status update 28.03.2012 Tushant Singh
Wafer Status - Fabrication *EDX = Energy-dispersive X-ray spectroscopy To bedoneat CSEM Neuchatel on 2nd April
SphagettiProblem – Recall Oxide strip – wet etch (BHF) Wafer#3426 White colored ‘Sphagetti’ observed coming out of the channels
SEM pictures SEM pictures of structures weretaken and thisiswhat the side-walls of the channel look like.
Sphagetti Problem Wafer with Sphagetti Problem #3694 Wafer without Sphagetti problem #3442 You canseedirtysidewalls and dirty surface in thispicture
SphagettiProblem • Possible causes – • WE DONT UNDERSTAND, but the guessis: • Contamination in dry etch machine • Contamination in wetetch bath For nowwe are not observinganysuchproblems
Surface RoughnessProblem • During SEM imagingfor lookingatSphagettiproblemitwasobservedthat the Wafer surface wasvery rough. • This could cause badbonding.
Compare surface roughness (Top surface) Wafer with Sphagetti problem #3694 Wafer without Sphagetti problem #3442
Surface RoughnessProblem • Preliminary investigations show thatthisproblemisassociatedwith wafers thathad the Sphagettiproblem. • The wafer whichdid not have sphagettiproblemlooked OK in terms of Surface roughness. • Further investigation neededwith more wafers.
Furtheractivities • New batch of 3 wafers • Modifiedprocess flow • Slight modification in process flow has been proposed and isunder discussion with Alessandro.