Specific Process Knowledge/Wafer cleaning/RCA

RCA cleaning

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 consist of two solutions: RCA1 and RCA2 plus diluted HF.

The RCA1 contains: H $_{2}$ O, NH $_{4}$ OH and H $_{2}$ O $_{2}$ (5:1:1). It is used for removed of light organics, particles and metal.
The RCA2 contains: H $_{2}$ 0, HCl and H $_{2}$ O $_{2}$ (5:1:1). It is used for removal of heavy metals, alkalies and metal hydroxides.

RCA procedure

RCA1: 10 min
DI wafer rinsing (dumping three times)
HF: 30 sec (avoid it if you have oxide as the top layer)
DI wafer rinsing (dumping three times)
RCA2: 10 min
DI wafer rinsing (dumping three times)
HF: 30 sec (avoid it if you have oxide as the top layer)
DI wafer rinsing (dumping three times)

Overview of RCA process data

	7-up	Piranha
General description	Cleaning of wafers or masks using the dedicated tanks. There are one tank for masks and glass wafers and one for 4-6" Si wafers in cleanroom 4 and one tank in cleanroom 3 for 4" Si wafers only.	Cleaning of wafers using a beaker in the fumehood in cleanroom 2. Used for glass wafers or wafers with metal or other materials that you are not allowed to put in the 7-up for wafers.
Chemical solution	98% Sulfuric acid and Ammonium sulfate	98% Sulfuric acid and Hydrogen peroxide 4:1 add H $_{2}$ O $_{2}$ to H $_{2}$ SO $_{4}$
Process temperature	80 ^oC	~70 ^oC the chemicals will heat up to working temperature during mixing, therefore be careful!
Process time	10 min.	10 min.
Allowed materials	Dependent on which bath is used, look at the text in the pictures.	All materials (in beaker).
Batch size	1-19/25 4" wafers or 4 masks at a time	1-5 4" wafer at a time
Size of substrate	4-6" wafers	2-4" wafers