EMULSITONE COMPANY
19 Leslie Court
Whippany, New Jersey 07981
TEL. (973)386-0053
FAX (973)503-0256

PHOSPHOROFILM FOR SOLAR CELLS

Phosphorofilm for Solar Cells is an aqueous solution of a polymer containing phosphorous which may be applied to silicon wafers either by spraying or spinning.

Physical Characteristics
Viscosity 7 cp @ 25^oC
Density 1.01

Contaminant Limits
Na, Fe, Zn, Cu, Au, Mn, Ni < 1 ppm

Application Notes
Films may be deposited either by spinning or spraying. Spinning at 3000 rpm will yield a film about 3200 angstroms thick. Film deposited by spraying will exhibit excellent leveling characteristics. Film thickness obtained by spraying will depend upon such variable as the liquid flow rates, determined by liquid pressure, and rate of travel of the substrates under the spray nozzle. Typical conditions are as follows:

Orifice size...............0.3 mm
Liquid flow rate...........5 cm3/minute
Height of nozzle above wafers................8-10 cm.
Wafer Traverse under spray gun...............30 cm/minute


Films deposited by spinning are ready for diffusion. Films deposited by spraying should be heated to 40-50^oC to insure drying.

Diffusion
Diffusion is carried out in nitrogen atmosphere with 1-2% oxygen. Typical results for one hour diffusion are as follows:

After diffusion films which remain on the wafer surface are readily etched away in dilute HF solution.

Cleaning
All apparatus used with this solution may be cleaned in warm water.

Safety Considerations The solution is essentially non-flammable. The phosphorous concentration is such that the material should not be ingested. Eye protection should be used, since the solution is acidic. During the diffusion process, in addition to CO₂, oxides of phosphorous will be evolved. At room temperature the only volatile is H₂O. Since no toxicity studies have been carried out with this product, it should be treated with care as with any laboratory chemical.

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