Bias Instability Figures That Decide Whether Dead Reckoning Holds
Inertial dead reckoning holds only while gyroscope bias instability bounds cubic tilt divergence within allowable spatial position tolerance thresholds.
DRIE Wafer Etching Yield
Yield Percentage
Percentage of functional semiconductor devices recovered from a substrate after a deep reactive ion etching process. High aspect ratio features depend on drie wafer etching yield to define the viability of microelectromechanical systems production. It measures the effectiveness of the plasma chemistry and the protective polymer deposition in maintaining vertical sidewalls.
Process Uniformity
Radial variations in plasma density often cause the etch rate to differ between the center and the edge of the silicon disc. This imbalance in drie wafer etching yield results from the microloading effect where dense patterns consume reactants faster than isolated features. Equipment manufacturers calibrate the gas flow and power distribution to minimize these local discrepancies.
Sidewall Integrity
Scalloping along the trench walls occurs as a result of the alternating etch and passivation steps in the Bosch process. Excessive roughness reduces the drie wafer etching yield by creating stress concentrations or electrical leakage paths in the final device. Metrology tools use scanning electron microscopy to verify that the profile angle remains within a few tenths of a degree from vertical.
Optical emission spectroscopy monitors the plasma state in real time to detect the precise moment the etch reaches the buried oxide layer.
Defect Density
Particles landing on the wafer surface during the vacuum cycle can mask the underlying material and create unetched pillars. Such contamination significantly lowers the drie wafer etching yield in cleanroom environments with poor air filtration. Periodic chamber seasoning and cleaning cycles maintain the necessary stability for high volume manufacturing.