Specific Process Knowledge/Wafer cleaning/IMEC

IMEC process for cleaning of wafers before fusion bonding:

Based on the IMEC clean 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 modified by Karen Birkelund @DTU Nanotek.

Step	Process	Details	Comments	Comments
1	Pre-bond cleaning of Si wafers prior to fusion bonding.		Takes 1½ hours Orient flat to minimize handling Preferable done just before bonding!	Get CLEAN box for wafers!!!
2	Piranha	Mixture: H$_{2}$SO$_{4}$:H$_{2}$O$_{2}$ (4:1) Temp: 80 oC Time: 5 min (a yellow and a black spot)	Clean tank (cleanroom 4, 7-up bath for wafers) and make your own or make in dedicated glass. Pour up H$_{2}$SO$_{4}$ first, put wafers in carrier (USE this in steps4.1-4.6), add H2O2, wait 30 sec, dip wafers.	Maybe clean the tank the day before!
3	Rinse	2 min. rinse		Put into dedicated wet box for IMEC
4	IMEC	DI water:5% HF:isopropanol (100:10:1) Temp: 25 oC Time: 100 sec (two black spots)	Clean tank (cleanroom 4, tank for buffer with wetting solution) and make your own. Mix in dedicated bottle (IMEC) in fume hood and add to tank using BHF pump from RCA fumehood!	.
5	Rinse	2 min. rinse	Put into dedicated wet box for IMEC	.
6	Piranha	Not nitride wafers! Mixture: H$_{2}$SO$_{4}$:H$_{2}$O$_{2}$ (4:1) Temp: 80 oC Time: 20 min	Re-use previous piranha Makes wafers hydrophilic	.
7	Rinse & spin dry	5 min rinse	.	.
8	Put wafers in new clean carrier box	.	.	.