低溫製備矽基鍺磊晶薄膜及矽基鍺緩衝層砷化鎵薄膜之研究

Low Temperature Growth and Fabrication of Silicon-based Epitaxial Germanium Films and Silicon-based Epitaxial Germanium Buffer Gallium Arsenide Films

謝泓火奇(HUNG-CHI HSIEH)

指導教授 ： 張正陽

國立中央大學/工學院/材料科學與工程研究所/碩士(2015年)

摘要

本篇研究低溫製備矽基鍺磊晶薄膜及矽基鍺緩衝層砷化鎵薄膜之研究，使用電子迴旋共振化學氣相沉積法(ECR-CVD)在180度的低溫製備矽基鍺薄膜。矽基鍺薄膜有許多項優點，因此未來發展相當有潛力: (1) 鍺材料的電子遷移率為矽的兩倍，其能隙為0.66 eV，比起矽的能矽1.12 eV來的更小，因此相當適合發展近紅外光的光電元件； (2)矽基鍺薄膜元件比起鍺基板元件所花費的成本較低 (3)矽基鍺薄膜元件易和矽基製程整合，並達到單時積體化的目的。傳統的矽基鍺薄膜成長溫度約為400-700度，而本研究的薄膜成長溫度為180度，不但低於傳統成長溫度，對於未來元件整合於CMOS製程上更有低溫製程的優勢。
本實驗藉由改變主磁場電流、氫氣流量和工作壓力，搭配熱退火處理，探討矽基鍺薄膜的特性影響。實驗結果顯示，品質最佳的鍺薄膜X光繞射(XRD)的半高寬(FWHM)為406 arcsec；原子力顯微鏡的均方根植(RMS)為2 nm；貫穿差排密度(TDD)為107 cm-2，鍺薄膜並存在0.32%的拉伸應變。相較於大部分低溫製程團隊鍺薄膜的特性，XRD的FWHM為1000 arcsec；AFM的RMS為2-10 nm；TDD為107 cm-2，鍺薄膜平均存在0.1-0.2%的拉伸應變，我們的鍺薄膜在應變和半高寬性質上相當突出。接著我們將鍺薄膜應用於近紅外光矽基鍺光偵測器，並獲得在1310波段0.01 A/W的光響應與0.2 mA/cm2的暗電流密度。而一般期刊中矽基鍺光偵測器的暗電流密度平均都在1-10 mA/cm2左右，所以我們的暗電流比起別人低了一個級數。此外，我們將上述鍺薄膜搭配”有機金屬化學氣象沉積法”(MOCVD)與”分子束磊晶法與”(MBE)，在矽基鍺薄膜上成長砷化鎵薄膜，比起傳統砷化鎵基板元件，其成本更低，也更容易與矽基系統整合與達到單石積體化。實驗上藉由改變鍺薄膜品質、改變砷化鎵薄膜厚度和使用不同成膜機台，而薄膜量測方面使用XRD、AFM、TEM、SEM和PL等設備進行分析。實驗結果顯示，品質最佳的砷化鎵薄膜XRD的FWHM為257 arcsec。

關鍵字

低溫 ； 電子迴旋共振化學氣相沉積法 ； 鍺薄膜 ； 砷化鎵薄膜 ； 虛擬基板 ； 鍺光偵測器

並列摘要

In this study, we use the electron cyclotron resonance chemical vapor deposition (ECR-CVD) to grow epitaxial germanium (Ge) thin films on single crystal silicon substrates (c-Si) and applied to the photodetector at a low temperature. Ge films grow on Si substrate has many benefit. (1)Ge has higher carrier mobility and smaller bandgap than Si. (2) Compared to a bulk Ge devices, Ge/Si devices can cost down. (3) Ge/Si devices are integrated on Si process easily. In this work, we use ECR-CVD to deposit epitaxial Ge on c-Si at a low growth temperature of 180 oC. Then, we use atomic force microscope (AFM), X-ray diffraction (XRD), and Etch pit density (EPD) to characterize the thin films properties. The result shows that the XRD full width at half maximum (FWHM) of 406 arcsec, AFM root mean square surface roughness (rms) of 2nm and EPD threading dislocations density (TDD) of 107cm-2 can be obtained when the Ge film thickness is 100 nm. After that, We fabricate a PIN Ge photodetector. The responsivity of photodetector in 1310 nm light source is 0.01 A/W at -1V and the dark current density is 0.2 mA/cm2. In addition, GaAs layers were grown by MBE and MOCVD on Ge/Si substrates. Compared to a bulk GaAs technology, this technology has great potential for use in the growth of GaAs nanoelectronic devices and optoelectronic devices on the Si substrate. The result shows that the XRD full width at half maximum (FWHM) of 257 arcsec.

並列關鍵字

Low Temperature ； ECR-CVD ； Germanium Film ； Gallium Arsenide Film ； Virtual substrate ； Gallium Photodetector

參考文獻

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