Specific Process Knowledge/Wafer cleaning/IMEC

From LabAdviser

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Please note: This elaborate cleaning method is only used very rarely. It has turned out that at DTU Danchip an 'RCA clean' prior to bonding (and do the cleaning and bonding very early in the morning with few people and thus lower particle level in the cleanroom) gives the best results. If you for some reason still prefer to do the IMEC clean described below, please contact DTU Danchip to make arrangements. We do not have dedicated IMEC equipment which is immediately ready for use.


The IMEC process: Cleaning of wafers prior to fusion bonding

The IMEC cleaning process is used in circumstances where extraordinary clean wafers are required. It is primarily intended for cleaning wafers prior to fusion bonding. This procedure is based on the IMEC cleaning process: M. Meuris et al. "The IMEC clean: A new concept for particle and metal removal on Si surfaces.", Solid state Technology, Vol. 38, Issue 7, pp 109-113, 1995. Has been slightly modified by Karen Birkelund.


Information about equipment relevant to this procedure can be found in LabManager:

Info page for 'Fume hood 01: Acids/bases'
Info page for 'Fume hood 02: Acids/bases'
Info page for 'Wet bench 03: Wafer and mask cleaning'
Info page for 'Wet bench 05: Al etch'
Info page for 'Wafer Cleaning'
Info page for 'Optional Bath (Currently not in operation!)'


Step Process Details Comments Comments
1 Pre-bond cleaning of Si wafers prior to fusion bonding. .
  • Takes approximately 1,5 hours
  • Orient flat to minimize handling
  • Preferably do the cleaning just before bonding to maintain cleanliness!
Get CLEAN box for wafers!!!
2 Piranha Mixture: H2SO4:H2O2 (4:1)

Temp: 80oC
Time: 5 min

You can use the 'Mask Clean' bath in Wet Bench 04 (in cleanroom D-3). However, this requires planning at least a couple of days in advance, since the bath is primarily used for other purposes!. Alternatively use a very clean glass beaker. The recommended procedure is:
  • Pour H2SO4 into bath/beaker
  • Place wafers in clean carrier (USE this in steps 2-7)
  • Add H2O2 to the beaker that already contains H2SO4
  • Wait 30 sec to ensure mixing of chemicals, then dip wafers.
Maybe clean the tank the day before!
3 Rinse 2 min. rinse Rinse you wafers with DI-water. Put into dedicated wet box for IMEC
4 IMEC Mixture: DI water:5% HF:Isopropanol (100:10:1)

Temp: 25oC
Time: 100 sec

Make an appointment some days in advance with a Danchip employee to help you with this step!
  • Clean tank (Cleanroom D-3, the 'Optional Bath' inside Wet Bench 05: Al etch)
  • Mix your IMEC solution in dedicated bottle (IMEC) inside a fume hood
  • Ask a Danchip employee to help you filling the solution into the 'Optional Bath' tank!

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5 Rinse 2 min. rinse Put into dedicated wet box for IMEC .
6 Piranha Not nitride wafers!

Mixture: H2SO4:H2O2 (4:1) Temp: 80oC
Time: 20 min

Re-use piranha previously made in step 2

Makes wafers hydrophilic

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7 Rinse & spin dry 5 min rinse . .
8 Put wafers in new clean carrier box . . .