不同構型之高G值壓阻式微型加速度計的研製探討

Abstract

隨著現代國防發展，各國競相發展精緻型戰術裝備，期能以精準武器給予敵方關鍵性的致命一擊，而不致殺傷普羅百姓，摧毀民生建物，破壞工業設施。這些精準武器需要統合的範圍包含：自動偵查技術、引信精準定位、導彈軌道修正、飛彈攔截追蹤、安全系統等系統，皆須仰賴精密的加速度計、陀螺儀等元件互相配合下才能發揮特定的功能，因此這類技術是目前先進國家亟待精進的領域。。然而我國在高G值微型加速度計的研究和發展目前仍處於積極開發的階段，因此本篇論文正以開發可行之高G值加速度計的製程技術為探討重點，並且設計不同種形式之加速度計，以研究何種製程流程設計及製程方法最為可行，且符合成本及時間上的考量和要求。 本篇論文所設計之微型加速度計，預期可承受的衝擊為10,000G。為了尋求最適合的設計，並節省製程的成本和時間，本文首先以CAD繪製五種不同設計之加速度計結構，並利用ANSYS將幾何構型進行網格切割及參數設定，完成後匯入LS-DYNA或是ANSYS進行數值模擬計算，以模擬的結果檢測五種不同結構在設定的高G值衝擊環境下，是否會發生響應的應力超過材料的強度而損壞。 經過模擬計算後，確定本文所設計的加速計能承受預定之衝擊力，結構仍不破壞，且感測的壓阻器有足夠的應變量，可輸出明顯的電壓值，接著便著手進行製程規劃的設計。由於所設計之各型加速度計結構並不相同，可分為十字原型、十字原型上懸臂樑處額外加入質量塊、十字原型上於四街角處加入質量塊、可彎曲板式加速度計和改良後可彎曲板式加速度計等五種，並將前三種設計放於N型矽晶圓上製作，後兩種則使用SOI晶圓材料來進行製作，因此本文所開發出的製程流程共有三種。 經過三種不同的製程步驟規劃，然後依規劃在不同的矽晶圓上研製五種不同設計的加速度計。經過這三種試製過程，實際成功完成設計結構形狀的加速度計僅有最後一種設計：改良後可彎曲板式加速度計。晶圓製作完成後，經切割和簡易封裝，放置於高速旋轉機台上進行加速度測試。由實驗的結果證明所製造出的晶片是符合預期目標的，其訊號經過濾波處理後，其線性度可達1.12%、敏感度則為1.54μV/G。

With the rapid progress of modern defense technology, many developed countries devote to smart munitions, aiming to fatal attack with less damage to human, civil and industrial facilities. These elaborate weapons integrate automatic detection technology, precisely positioning fuse, guided projectiles, target intercept tracking, safety system, etc. The modern fuze technology plays one of important rolls in the current advances of all systems. This smart subsystem relies on accelerometer, gyroscope, and other components in coordinate with each other to accomplish the mission. However, research and development of high-G accelerometer in this country is still in the stage of emergent phase. As such, the emphasis of this thesis is to plan for fabrication processes suitable for high-G accelerometers. Several configurations of accelerometers are designed which can be processed by facilities of university and related institutions. The key factors considered for the design of fabrication processes are feasibility and required time and cost. In this thesis, micro accelerometers were designed to withstand the impact of 10,000 G. In order to seek the most proper design and to reduce cost and time in fabrication, the current research employed the CAD package to create five structural models of accelerometers, and ANSYS to generate mesh and to set up computing parameters. Upon finishing the setup, the discretized models were imported to LS-DYNA or ANSYS to execute numerical computation. The results of simulations were examined whether the five accelerometers can survive from the designated impact condition or need further modifications in design. The respond stresses of all five accelerometers must be within the allowable stresses of the materials in the high G environment. After the simulation, the thesis guarantee structure is still not destroyed in the expected impact strength, then began the fabrication flow design. Due to the design of the accelerometer structure is different, it can be divided into five categories: crisscross prototype, adding additional proof masses under four cantilever beams, adding additional proof masses at the four corners, flexible plate accelerometer, and improved flexible plate accelerometer. The first three designs were manufactured on N-type wafers, the other two were processed on SOI wafers. Three processing procedures were proposed for these accelerometers. With the three planed schedules for processing, five accelerometers were fabricated on several wafers. However, some fetal difficulties were encountered in semiconductor processing. Failures in transresistors and metal conducting films occurred in the first three designs of accelerometers. Unfortunately, poor response sensitivity was found in the fourth design, even though the structure was successfully fabricated. Nevertheless, the improved flexible plate accelerometer was accomplished both in structure and function. With simple packaging, this accelerometer was placed in a high-speed centrifugal machine for quasi-static testing. Sampling data were transmitted in radio frequency to a PC for acquisition and process. Experimental results demonstrated that the sensing chip performs as expectations. The linearity of the filtered data was found to be 1.12%, and the sensitivity is 1.54μV/G.