Ion Implantation Profile Optimization for Thermal Drift Suppression in MEMS
Dual-implant boron-phosphorus profiles achieve zero-crossing TCR at 3.5e19 cm^-3, suppressing piezoresistive thermal drift to 12 ppm/K.
Thermal Drift Suppression
Stability Control
A system design methodology reduces the unwanted variation in a sensor’s output caused by temperature changes. Applying thermal drift suppression is necessary to maintain the accuracy of precision instruments in environments with fluctuating temperatures.
Compensation Circuit
The most common approach involves integrating a temperature sensor close to the sensing element to measure the localized thermal changes. This temperature signal is used to adjust the bias current or the gain of the signal amplifier to cancel the drift. If the drift is non-linear, a digital microcontroller can apply polynomial corrections stored in a lookup table.
This dynamic adjustment maintains the output signal stability across the full operating range.
Material Selection
Using materials with matched coefficients of thermal expansion reduces the mechanically induced stress on the silicon die. Symmetrical layouts for critical analog components also help cancel out the differential thermal gradients. This physical design approach reduces the baseline drift before any electronic compensation is applied.
Performance Verification
Sensors are tested in thermal chambers while being subjected to a constant physical input. The output is monitored across the entire temperature profile to calculate the residual drift. This test ensures that the suppression techniques have achieved the required specifications.