Short-Pulse Laser and Plasma Etching Composite Micromachining for Realizing High-Accuracy SiC Pressure Sensor

The micromachining of silicon carbide (SiC) materials, particularly deep etching with high precision and uniformity, limits their widespread application. This article presents a composite micromachining method combining short-pulse laser and plasma etching. Approximately 85 sensitive diaphragms are successfully fabricated on one-quarter of a 6-in SiC wafer. The central 5 × 5 array was selected for testing, with the final diaphragm thickness deviation maintained below 3%. A statistical analysis of the static characteristics of eight sensors was conducted, revealing a correlation between machining error and sensitivity error. The best-performing sensor exhibited a sensitivity of 1.819 mV/V/MPa within the 0-5-MPa range, with an accuracy error as low as 0.36%. The zero temperature drift coefficient (TCZ) of the chip was within 0.1% FS/°C up to 550 °C, reaching a maximum value of approximately 0.15% FS/°C at 600 °C. The relative voltage fluctuation (RVF) remained within 8% at 600 °C. After 12 days of exposure, the chip's resistance value increased by 0.72% in H2SO4 solution and by 1.47% in NaOH solution, demonstrating its resilience to corrosive environment.