Specific Process Knowledge/Wafer cleaning/RCA

RCA cleaning

RCA bench: positioned in cleanroom 2.
RCA1 - RCA2 - HF - BHF(pre-dep wafers)

The RCA clean is used for cleaning the wafers before taking them into the furnaces and a few other equipments (check the cross contamination sheet). It consists of two solutions: RCA1 and RCA2 plus diluted HF. A crucial part of the RCA clean is the oxidation by H₂O₂. Therefore the life time of the RCA solutions are limited by the presence of the H₂O₂ which is highly volatile at 70 ^oC.

• The RCA1 contains: H₂O, NH₄OH and H₂O_{2 (5:1:1). It is used for removal of light organics, particles and metals.}
  
• The RCA2 contains: H₂O, HCl and H₂O₂ (5:1:1). It is used for removal of alkalis, metal hydroxides, and residual metals.

RCA procedure

• RCA1: 10 min
• DI water rinsing (dumping three times)
• HF: 30 sec (you may avoid this step in case of a very thin oxide (0-200 Å) as the top layer)
• DI water rinsing (dumping three times)
• RCA2: 10 min
• DI water rinsing (dumping three times)
• Optional: HF: 30 sec (avoid it if you have a very thin oxide (0-200 Å) as the top layer)
• DI water rinsing (dumping three times)

For procedure details please look in the user manual positioned in LabManager.

Overview of RCA process data

	RCA1	RCA2	HF
General description	Used for removal of light organics, particles and desorption of trace metals (Au, Ag, Ni, Cd, Zn, Co, Cr, etc).	Used for removal of alkali ions, metal hydroxides (of Al, Fe, Mg, Zn) and residual trace metals (e.g. Cu and Au).	Used for removal of oxide generated in RCA1 and RCA2
Chemical solution	H2O, NH4OH(25-29%) and H2O2(30%) (5:1:1)	H2O, HCl(37%) and H2O2(30%) (5:1:1)	5% H2
Process temperature	70-80 oC	70-80 oC	Room temperature
Process time	10 min.	10 min.	30 sec.
Life time of the chemical solutions	Can only be heated one time. When hot: it lasts for ~1h	Can only be heated one time. When hot: it lasts for ~1h	~2 months
Allowed materials	Silicon Silicon oxide Silicon nitride Quartz wafers/fused silica	Silicon Silicon oxide Silicon nitride Quartz wafers/fused silica	Silicon Silicon oxide Silicon nitride
Batch size	1-25 2",4" or 6" wafers at a time	1-25 2",4" or 6" wafers at a time	1-25 2",4" or 6" wafers at a time
Size of substrate	4"-6" wafers For 2" wafers please contact Danchip staff	4"-6" wafers For 2" wafers please contact Danchip staff	4"-6" wafers For 2" wafers please contact Danchip staff