高品質高敏感度之矽鍺奈米感測元件平台之開發

Abstract

我們將利用側壁式奈米線結構製作可量產的矽鍺奈米線，預期鍺的加入將會增加奈米線的電流外，而分別在pH與蛋白質的奈米生醫檢測上，我們可以發現鍺的濃度越高其感測能力也相對提升，但是過高的鍺濃度(40%)卻反而會降低其敏感度，其因可能為過高的鍺濃度造成表面的缺陷過多的緣故。由於高濃度的矽鍺薄膜沈積是較困難，而在矽鍺薄膜的氧化過程中，只有矽會參與氧化而鍺原素則會析出，最後鍺的濃度會提高且整個薄膜厚度會下降並降低其缺陷，且相較同濃度的沉積，氧化後的矽鍺薄膜擁有較低的缺陷。因此本計劃希望藉由矽鍺氧化技術與Si-Ge奈米線整合，以解決高濃度鍺沈積問題之外，且大幅增加敏感度。 我們將此計畫主要分為幾個部份。首先，我們先穩定製作矽鍺薄膜的沉積。並穩定製作各種濃度之矽鍺奈米線，以及分析各濃度矽鍺奈米線電性外，並比較各濃度之感測能力。其次，我們將以矽鍺薄膜電晶體作為測試結構，利用氧化造成鍺析出的技術來提高鍺濃度，並探討不同的氧化時間、氧化溫度、氧的流量、氮氧比、氧化前退火、氧化後退火，以及先疊一層PE/ECR SiO2將氧化控制在diffusion control mode以大幅降低氧化速度來提升氧化品質，並進一步分析和討論造成電晶體電性提升之物理機制及最佳化條件。最後，我們將其分析結果應用於矽鍺奈米線，以完成純鍺奈米線研究與電性探討；此外，研究氧化後矽鍺奈米線電流的增益情況並分析改善後的矽鍺奈米線敏感度。預計在元件旁邊增加Micro Wire做氧化後的探討，以及多項測試結構為製程監控。我們預期藉以鍺的加入、高溫處理，與氧化製程而得到更高濃度的矽鍺奈米線、更高的導通電流、更小體積的奈米線、更低的缺陷，以期擁有更高的感測能力。

We will use sidewall spacer technique to fabricate the SiGe nanowire (NW) with high carrier mobility instead of Si nanowire. We expected resulst: Ge enhances the drive current for SiGe nanowire, and we also found that the sensitivity improves with the increment concentration of Ge at low concentration of Ge which detecting the pH solution and protein. However, the reason for decrement of the sensitivity at 40%-Ge concentration may be higher defects appearing at the interface. It is well-known that the SiGe film with higher Ge concentration is difficult to deposit. We found that only Si element was oxided and Ge was rejected to the interface between SiGe film and oxide film during SiGe oxidation. The concentration of Ge increases, but the thickness of SiGe film and the defect decrease after SiGe oxidation. In addition, compared to the SiGe film with the same Ge concentration, we find that fewer defects appear after SiGe oxidation. So that we expect to combine the SiGe oxidation technique with our SiGe nanowire to solve the problem of SiGe deposition with high Ge concentration and improve the sensitivity. We separate three major parts about this plane. First, the stable deposition of SiGe film and stable fabrication of SiGe nanowires will be studied. The electronic properties and the sensitivities of SiGe nanowires with different Ge concentrations will be studied and compared. Second, the SiGe-thin film transistor (TFT) is utilized to test the SiGe oxidation technique. Various conditions such as oxidation time、oxidation temperature、flow of oxygen、the ratio of oxygen and nitrogen、pre-annealing、post-annealing, and pre PE/ECR-SiO2 deposition for diffusion control mode will be studied to realize and discuss the enhancement、the mechanism and the optimal conditions after SiGe oxidation. Finally, we will apply the results to our SiGe nanowire. The properties of pure Ge nanowire will be discussed. We will analyze that the improvement of the sensitivity for Bio-Sensor by SiGe nanowire oxidation. Also, the additional micro wires are used to understand the influence after SiGe oxidation, and some test structures are used to monitor the fabrication processes. We anticipate that a SiGe nanowire with higher Ge concentration、higher drive current、smaller size, fewer defects and higher sensitivity will be obtained after well-controlled oxidation.