濕式氧化法應用於絕緣層覆矽與矽基板上微環共振腔之製作與量測

Fabrication and Measurement of Micro-Ring Resonators on Silicon-on-Insulator Substrates and Silicon Substrates using Wet Oxidation

姚皓凱(Hao-Kai Yao)

指導教授 ： 毛明華

國立臺灣大學/電機資訊學院/電子工程學研究所/碩士(2018年)

https://doi.org/10.6342/NTU201800441

摘要

在本論文中，我們利用理論分析與數值模擬輔助來設計元件並以製程技術實現，主要引進氧化的製程在兩種不同的基板上製作微環共振腔，由於希望成長較厚的熱氧化層，所以選擇氧化速率較快的濕式氧化技術。
我們首先在絕緣層覆矽基板上的傳統微環製程中加入濕式氧化製程，傳統製程作出的微環會因為蝕刻側壁造成表面粗糙不平整，所以我們在蝕刻製程之後引進濕式氧化，改善了微環的表面粗糙度，減少了光經過共振腔時的表面散射損耗，使得我們元件的品質因子Q值得以提升，直徑10微米的微環Q值可以從5420提升到9050，直徑20微米的微環Q值可以從2890提升到7980。
另外，我們希望在矽基板上透過濕式氧化法直接製作微環共振腔、減少製程時的成本，由於製程步驟複雜，我們藉由掃描式電子顯微鏡的輔助，觀察不同製程步驟對元件結構的影響，並用COMSOL加以模擬分析。但是因為不同晶格面的氧化速率不同的關係，造成共振腔的寬度粗細不一致，使得光在共振腔內行進時的損耗過大，導致我們無法觀測到模態的存在。

關鍵字

微環共振腔 ； 濕式氧化 ； 光學量測

並列摘要

In this thesis, our devices were based on theoretical analyses and numerical simulations, and then we fabricated such devices. The highlight of our thesis is using oxidation to fabricate micro-ring cavities on two different substrates. We hope to grow thicker thermal oxide on our devices to confine light better. Therefore, we choose wet oxidation for its higher oxidation rate.

At the beginning, we add the wet oxidation method to the traditional fabrication of micro-ring cavities on SOI substrate. The traditional fabrication method may cause surface roughness because of dry etching the sidewall. So, we use wet oxidation after etching process to improve surface roughness. We reduce the surface scattering loss while the light propagating in the cavities, and the quality factor can be improved. The quality factor of a 10-m-diameter micro-ring can be increased from 5420 to 9050, and that of a 20-m-diameter micro-ring can be increased from 2890 to 7980.

We also fabricated micro-ring cavities directly on silicon substrate by the wet oxidation method. It can reduce the manufacturing cost. Scanning electron microscope images have been taken step by step along the fabrication flow due to the need for delicate control of etching/oxidation processes. And COMSOL has been used to simulate the electromagnetic wave distribution in the device structure. However, due to the different oxidation rates on different lattice orientations, the width of the cavity is not uniform. We consider that it would lead to large loss during the light propagating in the cavity. As a result of that, the resonance modes have not been observed.

並列關鍵字

Micro-ring resonators ； Wet oxidation ； Optical measurement

參考文獻

[8]王舜能, "絕緣層覆矽全光微環調製器之製作與量測," Master Thesis, NTU GIEE (2015).

[2] K. J. Vahala, "Optical microcavities," Nature 424, 839-846 (2003).

[3] Q. Xu, D. Fattal, and R. G. Beausoleil, "Silicon microring resonators with 1.5-μm radius," Opt. Express 16, 4309-4315 (2008).

[4] J. Heebner, R. Grover, T. Ibrahim, Optical Microresonators: Theory, Fabrication and Applications, Springer (2008).

[5] B. E. A. Saleh, and M. C. Teich, Fundamentals of Photonics, Wiley(2013).