Mumbai University > Electronics Engineering > Sem 8 > MEMS Technology

Marks: 2M

Before subjected to micromachining processes the wafer must be cleaned.

The standard set of wafer cleaning steps is called the RCA cleans.

The first step is removal of all organic coatings in a strong oxidant, such as 7:3 mixture of concentrated sulfuric acid and hydrogen peroxide.

Then organic residues are removed in a 5:1:1 mixture of water, hydrogen peroxide and ammonium hydroxide.

Because this step can grow a thin oxide on silicon, it is necessary to insert a dilute HF etch to remove this oxide when cleaning a bare silicon wafer and it is omitted when cleaning wafers have intentional oxide on them.

Finally ionic contaminants are removed with a 6:1:1 mixture of water, hydrochloric acid and hydrogen peroxide.

Cleaning solutions do not have captions.

These RCA cleans must be performed before every high-temp steps.