以微機電系統（MEMS）製程技術開發而成的微機械感測器已廣泛地發展於汽車工業、航太領域與生醫應用，例如微壓力感測器與微剪應力感測器。為了使微機電系統產品的工作性能提高、成本降低以及因應不同應用的要求，微結構的最佳設計與相關製程的改善是迫切需要的。在微結構的設計方面，結構材料的機械性質、熱效應、製程技術上的限制以及工作性能的要求皆是重要的設計因素。在本研究中，非等向性機械性質的單晶矽若假設為等向性材料來進行微結構設計，是否會對設計出的元件性能有巨大影響被提出，並用有限元素法來檢驗。結果顯示對於壓阻式與電容式壓力感測器而言，將單晶矽假設為等向性材料將會造成設計出的元件靈敏度與真實性能間存在誤差。再者，二氧化矽絕緣層與單晶矽平膜間的熱應力用有限元素軟體來模擬與分析，分析結果顯示熱應力大小與絕緣層厚度有關。當絕緣層厚度等於平膜厚度一半時，熱應力為最小，其次，絕緣層厚度若小於平膜厚度十分之一，則熱應力將趨於定值，最後，絕緣層厚度若大於平膜厚度，則熱應力會劇烈增加。在考量壓力靈敏度、靈敏度溫度係數、偏差溫度係數與製程上限制的前提之下，本文建立X-ducer微壓力感測器的設計方法並實現在膝上義肢用的微壓力感測器上。此微壓力感測器的原型已製造與測試，工作性能令人滿意。另一方面，利用自行發展的解析法來完成漂浮元素微剪應力感測器的最佳設計並以有限元素模擬結果加以佐證。由解析法設計的微剪應力感測器靈敏度遠優於文獻上發表的微剪應力感測器靈敏度。
本文並發展新型接觸式微剪應力感測器，此感測器的設計重點在於避開受外界壓力的干擾以及X-ducer的方位。此微剪應力感測器原型的測試結果為壓力干擾小於12%（0~320 kPa），靈敏度為0.13 mV/mA-MPa及遲滯誤差3.5%。
在類LIGA製程研發方面，首先以理論分析來對近紫外光與KrF準分子雷射作特性的比較。高能量、短脈衝的KrF準分子雷射能製作出尺寸較小與深寬比較高的微結構物，但是成本較昂貴。在電鍍種子層方面，研究了銅、金、鋁、鎳、鉻與鈦薄膜。由於鈦薄膜與玻璃基材及鎳沈積物有好的附著力、抗腐蝕、對鎳有高的蝕刻選擇性以及低內應力的特性，所以鈦薄膜被選為種子層。用四點探針與表面輪廓儀來對鈦薄膜進行測試，測試結果顯示鈦薄膜的組織性質與電特性皆不錯。另外對所有金屬薄膜而言，電阻率會隨著膜厚變小而變大，而且在膜厚大於某臨界值後電阻率趨於定值。基於低電阻與低殘留應力為考量而決定鈦薄膜的厚度。在電鍍用微模方面，建議四種厚膜光阻，其名稱或商品名稱分別為PMMA、SU-8、Polyimide及AZ 4000。此四種光阻皆可與製程相容，且具有化學與熱穩定的特性及高絕緣強度，故可作為微模材料。製作後的微模利用顯微鏡與CCD照相機以及表面輪廓儀來檢視。接著發展正反相脈衝式電流電鍍的技術。分析與設計正反相脈衝式電流的參數，以進行電鍍物表面粗糙度、內應力、孔隙與組織型態的研究。在電鍍微結構之表面粗糙度、孔隙與組織型態的考量下，建立正反相脈衝式電流參數的設計方法，並且以近紫外光LIGA製程來實現此設計方法。實驗結果顯示，正反相脈衝式電流電鍍微結構的表面粗糙度（8.0%）比直流電鍍的結果（42.6%）還要平滑，而且在微膜邊緣沒有過渡電鍍的現象，而直流電鍍的結果則有過度電鍍的現象。再者，正反相脈衝式電流電鍍微結構比直流電鍍具有較少的孔隙。利用電子掃瞄顯微鏡（SEM）驗證出正反相脈衝式電流電鍍微結構具有較緊密的沈積物與較精細的晶粒。綜合以上結果得知，本研究發展的正反相脈衝式電流電鍍的設計方法可提供MEMS領域中的工程師獲得具有良好性質的電鍍微結構。

MEMS-based mechanical sensors such as pressure sensor and shear-stress sensor have been widely developed for the automotive industry, aerospace fields and biomedical applications. The design of microstructures and the improvement of the manufacturing technology become more and more important for products with better performance and reduced cost and for satisfying more applications. For the design of microstructures, mechanical properties of the substrate material such as pure silicon, thermal effects, manufacturing limits, and performance requirements are important issues. In this research, the validity of postulating monolithic silicon as isotropic material on evaluating the performance of wet bulk-micromachined piezoresistive and capacitive pressure sensors was examined by means of finite-element analyses. It was evident that the design of microstructures was unacceptable if the single-crystal silicon was treated as an isotropic material. Moreover, the thermal stress, which resulted from differences in the TECs between the SiO2 dielectric film and the Si diaphragm for a micro pressure sensor was studied through finite element analyses. The results revealed that the minimum thermal stress occurred when the SiO2 dielectric film to Si diaphragm thickness ratio was 0.5. The design procedures of X-ducer pressure sensors considering pressure sensitivity, temperature coefficient of sensitivity, temperature coefficient offset, and manufacturing limits were established and realized in a biomedical pressure sensor. Satisfactory performances of a prototype micro-pressure sensor were obtained. On the other hand, the optimum design for a typical micro floating-element shear-stress sensor based on the sensitivity analysis was carried out by means of a quasi-analytic method. It showed that the design by this method was approximate to the FE design and the sensitivities calculated from the quasi-analytic method were much higher than those of developed sensors in the literatures.

A new contact type shear-stress sensor insensitive to the external pressure was innovated from the inspiration of an X-ducer pressure sensor. The flange on the diaphragm was a primary mechanism loaded by the external shear stress and the location of X-ducers was an important factor for sensing decomposed shear stresses. The measured cross-talk percentage due to pressure was less than 12% in the pressure range of 0 to 320 kPa for a prototype of the contact type shear-stress sensor. The sensitivity and overall mean hysteresis error were tested and calculated to be 0.13 mV/mA-MPa and 3.5%.

For MEMS technologies, the wet bulk micromachining had lots of limits such as the simple structural geometry, low aspect ratio, and narrow choices of materials as compared with the LIGA-like process. Therefore, in this dissertation the seed layer, micro molds, and the electroplating of a UV-LIGA process were investigated for optimal process parameters and to yield microstructures with good qualities. Various metallic thin films were fabricated and studied for the seed layer. Deposition qualities of the metallic thin film were checked and the thin-film thickness was determined based on low resistance and low internal stress. Several thick photoresists compatible with the UV-LIGA process were presented for micro molds. The parameters of pulse-reverse-current (PRC) plating were analyzed to study their effects on surface roughness, pits, and morphology of plated microstructures. An available method for determining PRC parameters was developed. The results revealed that a titanium thin film was a good choice of seed layer due to its good adhesion to substrate and to plated deposits, low internal stress and low resistance, high corrosion resistance, and better etching selectivity against nickel. Depending upon the available manufacturing facilities, application requirements, and the cost, polyimide was chosen as the plating mold in the experiment. The microstructure with better surface roughness, fewer pits, and finer morphology was obtained by using the PRC plating as compared with those using the DC plating. One can extend the approach in this dissertation to other LIGA-like processes for making products with good performance and low cost.

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