Protective Barrier
Protective thin films deposited on the surface of a microelectronic sensor prevent environmental contamination and chemical attack of the active circuitry. This protective coating, called a passivation layer, is typically composed of silicon dioxide, silicon nitride, or specialized polymers. It seals the sensitive electrical structures from moisture, ions, and mechanical damage, preserving the calibration and performance of the device.
Without this barrier, the silicon sensor would quickly degrade in harsh operating environments.
Drift Prevention
Moisture and mobile ions on an unprotected silicon surface cause leakage currents that lead to severe sensor drift. The passivation layer blocks these contaminants from reaching the silicon dioxide interface. This stabilization of the surface charge ensures the long term repeatability of the sensor output.
Manufacturing Control
Deposition of these protective films occurs during the wafer fabrication process using chemical vapor deposition techniques. The thickness and uniformity of the film must be tightly controlled to prevent mechanical stress on the sensor diaphragm.
Quality Inspection
Technicians inspect the film for pinholes and microcracks using scanning electron microscopy and electrical leakage testing. Any defect in the layer can lead to premature failure of the device. Ensuring a defect-free surface is a necessary step in qualifying the sensor for industrial use.
