Ion Implantation Profile Optimization in Piezoresistive Diaphragms
Implantation energy and post-anneal thermal budgets set piezoresistive sensitivity and offset stability in silicon pressure sensor diaphragms.
Bridge Sensitivity
Measurement Ratio
Transducer performance depends on the ratio of change in electrical output per unit of mechanical or physical input at a given excitation voltage. For a wheatstone network, bridge sensitivity determines the output voltage change divided by the input change when a constant excitation voltage is applied. This coefficient typically represents millivolts per volt of excitation per unit of physical stimulus.
Calibration Stability
The conversion factor is established during factory calibration by applying known reference standards under controlled conditions. When a silicon diaphragm undergoes pressure cycles, resistance variations alter the bridge sensitivity. This value must remain stable across cycles.
Excitation Level
Voltage applied to the bridge circuit directly scales the absolute output voltage. A higher supply voltage increases the absolute signal amplitude but introduces resistive self-heating that degrades accuracy. The system designer chooses a voltage that balances output strength against thermal stability.
Influence Parameter
Environmental conditions such as ambient temperature and humidity affect the stability of the output. If the operating temperature deviates from reference conditions, the nominal bridge sensitivity changes because the material properties of the piezoresistors depend on temperature. Compensating resistors or digital calibration coefficients are often added to the network to minimize this drift.
Testing at the limits of the operating range confirms that the residual error remains within the specified tolerance.