Fabrication of a surface micromachined capacitive microphone using a dry-etch process

A method of fabricating a capacitive microphone, said method comprising the steps of:

• A. depositing a diaphragm over a substrate;
• B. depositing a silicon layer over the diaphragm;
• C. depositing a backplate over the silicon layer;
• D. forming holes in the backplate;
• and
• E. introducing a dry etchant through the holes to form a cavity between the backplate and diaphragm by removing part of the silicon layer.

A method of fabricating a capacitive microphone, said method comprising the steps of:

• A. depositing a first silicon nitride layer over a silicon substrate;
• B. depositing a first conductive layer over the first silicon nitride layer;
• C. depositing a first diffusion barrier layer over the first conductive layer;
• D. depositing a silicon layer over the first diffusion barrier layer;
• E. depositing a second diffusion barrier layer over the silicon layer;
• F. depositing a second conductive layer over the second diffusion barrier layer;
• G. depositing a second silicon nitride layer over the second conductive layer;
• H. forming holes in the second conductive and silicon nitride layers;
• I. introducing a dry etchant through the holes to form a cavity between a backplate and a diaphragm by removing part of the silicon layer.