平面型微細探針的研究

Abstract

本篇研製出兩種作為資料存取用之平面型微細探針 。 整個結構將包含一懸臂樑及用來感測之探針。平面探針的尖端是利用非等向性蝕刻技術對晶格面蝕刻速率的不同，在三個晶格面的交會點而形成。根據感測元件的不同再分為兩種形式的掃瞄探針。一種是在懸臂樑的根部鋪設壓阻材料，當懸臂樑產生形變時利用橋式電路將壓阻的電阻的變化值轉換成電壓訊號以得知懸臂樑的應力變化，並推算出懸臂樑的位移 。此懸臂樑設計為三角形，以使表面應力更均勻，整個懸臂樑的尺寸為200微米(μm)×40微米×4微米。 另一種則是利用外部的光學感測元件量測反射光的角度以獲知懸臂樑的位移。懸臂樑的尺寸為250微米(μm)×45微米×4微米。 此外，也嘗試利用微電鑄以及犧牲層技術結合一電容式致動器在兩種掃描探針上。在製作技術上，不必用到傳統的結合技術，而採用厚膜光阻當犧牲層，在懸臂樑的上端鋪設一層鎳金屬作為上電極，形成一電容式致動器，以控制懸臂樑的微小位移，或是激發懸臂樑產生共振。

In this research, two types of planar scanning probes are designed and analyzed. The structure of the scanning probe includes a cantilever beam with a sensing tip. The tip is formed by the intersection of three crystal planes during wet anisotropic etching. Two types of scanning probes with different sensing principles are proposed here. One is integrated with a piezoresistor at the root of the cantilever beam. When the cantilever beam is bending, the variation of the resistance of the piezoresistor transfers to voltage signal by Wheatstone bridge circuit. Then the magnitude of the stress on the cantilever beam can be calculated and the displacement of the beam can be determined. The shape of the cantilever is designed as a triangle to have a uniform stress distribution on the surface. The dimensions of the cantilever beam are 200μm × 40μm × 4μm. Another probe use an external optical sensing component to detect the angle difference of the reflective laser light which can determine the displacement of the cantilever beam. The dimensions of the cantilever beam are 250μm × 45μm × 4 μm. An additional capacitive actuator can be integrated to the scanning probe by electroplating and sacrificial layer techniques. In fabrication, the traditional bonding technology is not needed here to form the electrostatic capacitor. Thick photoresist is coated on the cantilever beam to form a sacrificial layer and nickel is followed to be an electrode for the electrostatic actuator by electroplating. The function of the capacitive actuator is to control the tiny displacement of the cantilever beam or to excite the cantilever beam for resonance.