|Abstract: ||本文利用台積電0.35μm 2P4M標準積體電路代工（CMOS foundry）和後製程程序（post process），製作壓力感測薄膜為50μm×50μm大小之壓阻式壓力感測器；壓力薄膜之材質為二氧化矽，壓電阻之材質為多晶矽。因應微小壓力薄膜之製作，本文利用正面濕式蝕刻的方式進行中空壓力腔之後製程，蝕刻孔洞大小為5μm×5μm。在濕式蝕刻製程中，預先設計之金屬犧牲層將被蝕去，得到感測薄膜之微結構，其後利用氫氧化鉀(KOH)對矽基底材蝕刻出V型槽(V-groove)，為得到與外界隔絕之壓力感測器之空腔結構，此處使用明膠(gelatin)來進行孔洞填塞，最後對晶片進行加壓測試。|
This work investigates the fabrication of a piezoresistive micro pressure sensor with the size of 50μm×50μm using the standard CMOS and post process. The CMOS foundry, TSMC 0.35μm 2P4M process herein, is provided by CIC (Chip Implementation Center), Taiwan. The material of sensor membrane is silicon dioxide, and piezoresistors are made by polysilicon. To release the membranes of micro pressure sensors, this work proposes to use the front-side etching technique with etching holes of 5μm×5μm only. In wet etching process, the sacrificial metal layers will be removed, and release the membrane structure. After these, the V-grooves are etched anisotropically into the silicon substrate using KOH, and to get the pressure sensor''s cavity which is separated from the outside. Here we use one of the protein stuffs, gelatin, to seal the etching holes, and examine the chip in pressure test.
In the pressure test, the operating bias voltage of pressure sensor is 1 Volt, and the testing pressure ranges from 0 to 60psi. The performance of pressure sensor, the sensitivity is around 8.56±0.13 mv/v/psi, the linearity is 4.3±1.6%, and the hysteresis is less than 1%. This work demonstrated a piezoresistive pressure sensor which was made by CMOS MEMS technique, post process, and the packaging of gelatin. With the electrical/mechanical integration the micro structure of membrane , the micro force sensor have the advantages of smaller size and high sensitivity.