EMULSITONE CHEMICALS, LLC.
37 Willow Street
Washington, N.J. 07882
TEL (973) 386-0053
FAX (973)503-0256

 

GOLDFILM

Goldfilm is designed for application with a spinner. After 10 or 15 seconds of spinning, a fairly hard film will form on the wafer which contains gold atoms attached through suitable groupings to the carbon-carbon backbone forming the polymer. At the selected diffusion temperature the polymer decomposes releasing gold to diffuse into the wafer and CO2 and H2O which pass out the diffusion tube. The gold concentration achieved does not depend upon the atmosphere selected for the diffusion.

Application

Goldfilm is applied to the reverse (unpolished) surface of the wafer. When used as a diffusion source, the concentration profile obtained is not dependent on the spin speed or film thickness, because the gold concentration is sufficient that any continuous film will supply enough gold to saturate the wafer. Goldfilm may also be used to deposit thin metallic films on the reverse surface to facilitate child to package bonding. The metallic film will vary with spin speed. At 6000 rpm a 20 angstrom thick film will result, while a spin speed of 1000 rpm will yield a 100 angstrom film.

Diffusion Characteristics of Gold

The following data will be useful in determining the gold concentration which may be obtained in silicon as a result of the diffusion process.

Temperature (oC) Gold Saturation Solubility (atoms/cm3) Diffusion Coefficient
(cm/Sec
2)
600 1014 2x10-10
800 1015 6x10-9
1000 8x1015 4x10-8
1100 1016 8x10-8
1200 5x1016 1x10-7




Lifetime Control

The trapping cross sections obtained with Goldfilm are similar to the values obtained with evaporated or electroplated gold films. For reference, the following data shows the reverse recovery time for a p-n junction in which the high resistivity side was n type:


Diffusion temp. tr (nanosecond)
850oC 17
1050oC 3
1250oC 0.3




Process For Plating Out Metallic Films

As noted above 20 to 100 angstroms of gold may be deposited as a continuous film on a wafer by applying the material as directed. The wafer is then heated to 250o to 300oC. In 5 to 10 minutes film decomposition will occur, and a yellow film characteristic of gold will result.

Doped Goldfilms

Goldfilm with Boron and Goldfilm with Phosphorous are handled in a manner similar to the pure Goldfilm. These were designed for simultaneous gold and phosphorous or gold and boron diffusion yielding a deep penetration of gold to create an intrinsic region and a p+ or n+ surface layer as required in PIN devices.

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