Be careful what you wish for

SiO2 backside protection

A coating of SiO2 is deposited on the backside of the wafer to

insolate it from the doping process

PECVD• Plasma

• Enhanced

• Chemical

• Vapor

• Deposition

PECVD is used extensively in the manufacture of microelectronic devices because it allows for lower temperature processes

Just like in sputtering, a plasma is formed in an electric

field

The plasma allows for the deposition or growth of films at lower temperature than would

normally be required in just a CVD process

Trion ORION III PECVD tool

The plasma can be viewed through a

viewport on the side

Typical PECVD Process• The wafer is loaded in into the vacuum

chamber

• The chamber is pumped to vacuum conditions

• The wafer is heated to deposition temperatures (300oC typical)

• Gas are introduced that will acts as precursors to the film growth

Typical PECVD Process (continued)

• Chamber pressure is regulated to provide an equilibrium pressure ( gas in, pumping out)

• RF power is applied to the chamber creating a plasma

• A film is grown based on the gases introduced

For our solar cell

• We will be using SiO2 as the protective layer

Trion ORION III PECVDChamber lid open

Heated substrate stageCan accommodate up to 8”

wafers

Trion ORION III water chiller and dry (no oil) chemical vacuum pump

Trion ORION III process gas cabinet TEOS (tetraethylorthosilicon) SiO2 precursor

The backside of the solar cell will have a color tint. The color will

relate to the SiO2 thickness