Gas Characterization
Ionization of gas molecules within a vacuum chamber allows the identification and quantification of different chemical species based on their mass-to-charge ratios. Performing a residual gas analysis reveals the presence of moisture or solvent residues that can compromise sensor operation. This diagnostic process is carried out using a quadrupole mass spectrometer attached directly to the vacuum chamber.
Analytical Mechanism
The mass spectrometer accelerates the ionized molecules through a dynamic radio-frequency electric field that filters them by mass. Only ions of a specific mass-to-charge ratio can pass through the filter to reach the ion detector at any given moment. This selective filtration allows the system to generate a partial pressure spectrum for each gas species present in the mixture.
The resulting scan shows the presence of trace contaminants that might otherwise go unnoticed but could still affect sensor longevity. This method provides real-time tracking of the gas composition during critical fabrication steps.
Outgassing Detection
Identifying the source of contamination requires analyzing the species present during different stages of the packaging process. High concentrations of water vapor suggest incomplete baking, while the presence of organic molecules indicates residual solvent contamination from cleaning steps. This distinction allows production engineers to adjust the process parameters to eliminate the source of contamination.
Calibration Routine
Quantitative measurement requires calibrating the spectrometer using known gas mixtures at specified pressures. This procedure determines the sensitivity of the detector for different gases and establishes the baseline noise level of the analytical system. Regular calibration ensures that the measurement results remain accurate and comparable across different batches of sensors.
