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Metal Layer H2SO4 Etch

Study of the presence and density of pinholes in ccp films through measurements made on the visibility of H2SO4 etching of underlying layer of metal.

Procedure

 
1. Wafer preparation
The wafers were prepared with a layer of 100 nm of thermal oxide, followed by a layer of 500 nm of aluminum, and then the specific CCP film.
The films were deposited according to the table below.
 
Recipe Run time Film thickness
SiO 300-1 2 min 0.16 µm
SiO 350-1 2 min 0.16 µm
SiN 300-1 3 min 0.045 µm
SiN 350-1 3 min 0.045 µm

 
2. Etch
The wafers were etched at the wet bench silicide in the H2SO4 bath for 5 minutes.
 

Results

The wafers did not present a significant amount of etched spots across the center, but showed significant film degradation near the flat area which is used for wafer handling with tweezers. The SiN 300-1 film presented discoloration in certain areas after the etch.
 

Discussion

The experiment demonstrated the degradation of the film in the area of tweezers- handling (flat edge).

Moreover, a few hypotheses can be raised to explain the discoloration observed in the SiN 300-1 film. One, the discoloration could have been caused by the degradation of the film itself in contact with the H2SO4 bath. This would indicate the film has a less stable and resistance structure than the other films. Two, the discoloration could have been caused by a superficial or shallow etching by the chemical bath of the metal layer. This would indicate the film presented more pinholes than the other films across areas not degraded by handling.

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