矽鍺合金由於其可調變能隙特性以及與積體電路製程的高相容性成為近來廣泛應用於高速元件及光電子元件的熱門材料。然而通常矽鍺薄膜在高溫環境沉積或是對沉積後的薄膜作高溫退火處理才能獲得高效能特性。為了避免高溫處理步驟，我們利用一新式二氧化碳雷射輔助電漿增強化學氣相沉積的技術，是由於二氧化碳雷射為一能量源誘發矽烷以及鍺烷兩反應氣體分解。
本研究主要是以雷射輔助電漿增強化學氣相沉積系統沉積矽鍺薄膜作為通道層之金氧半場效電晶體，其中探討改變有無雷射輔助條件成長通道層對元件特性的影響，當有雷射輔助條件成長時，由元件之直流特性量測结果，在相同的閘極電壓40 V下，有雷射輔助的元件工作電流大小可達約450 nA比無雷射輔助的元件工作電流約30 nA大15倍；雷射輔助之最大互導值gm,max = 23 nS同樣地比無雷射輔助之最大互導值gm,max = 1.6 nS的大15倍，顯示雷射輔助條件成長矽鍺薄膜作為元件通道層具有一定的輔助效果。

Silicon-germanium (SiGe) alloy is a popular material in applications of high speed devices and optoelectronic devices recently due to its tunable bandgap and compatibility with integrated circuits. However, the deposited SiGe films usually has to be deposited or annealed at high temperature for obtaining high performances. To avoid the undesirable treatment in high temperature, we used a new technique of laser-assisted plasma-enhanced chemical deposition system. Since CO2 laser can be used as an energized source to induce reactions gases of SiH4 and GeH4.
SiGe based metal-oxide-semiconductor field-effect transistors (MOSFETs) were fabricated, in which the SiGe channel layer was deposited by using laser-assisted plasma-enhanced chemical vapor deposition (LAPECVD) system. The characteristics were compared with the device without laser assistance. It can be seen that under the same gate voltage 40 V, the source/drain current of the MOSFETs fabricated with laser-assisted SiGe channel is about 450 nA, which is 15 times larger than that of the MOSFETs with the SiGe channel deposited without laser assistance. The gm,max of the devices with laser-assisted SiGe channel is 23 nS, which is 15 times larger compared with the gm,max of 1.6 nS for the device without laser assistance. When the SiGe films were deposited with laser assistance, it shows that the deposited SiGe device channel layer with laser-assisted were quite assisting purpose.

[1] H. Tu, Q. Xiao, and T. Ma, “Strain effects and microstructural evolution in Ge-Si system materials prepared by ion implantation and by ultrahigh vacuum chemical vapor deposition”, J. Appl. Phys., vol. 102, 103502, 2007.
[2] C. Y. Su, S. L. Wu, S. J. Chang, and L. P. Chen, “Strained Si1-xGex graded channel PMOSFET grown by UHVCVD”, Thin Solid Films, vol. 369, pp. 371-374, 2000.
[3] B. G. Budaguan, A. A. Sherchenkov, and G. L. Gorbulin, “The properties of a-SiGe:H films deposited by 55 kHz PECVD”, J. Non-Cryst. Solids, vol. 297, pp. 205-209, 2002.
[4] S. Kannan, C. Taylor, and D. Allred, “PECVD growth of SixGe1-x films for high speed devices and MEMs”, J. Non-Cryst. Solids, vol. 352, pp. 1272-1274, 2006.
[5] J. Kubota, A. Hashimoto, and Y. Suda, “Si1-xGex sputter epitaxy technique and its application to RTD”, Thin Solid Films, vol. 508, pp. 20-23, 2006.
[6] H. Hanafusa, A. Kasamatsu, N. Hirose, T. Mimura, T. Matsui, and Y. Suda, “Strain-relaxed Si1-xGex and strained Si grown by sputter epitaxy”, Jpn. J. Appl. Phys., vol. 47, pp. 3020-3023, 2008.
[7] K. M. Shoukri, Y. M. Haddara, A. P. Knights, and P. G. Coleman, “Impact of growth conditions on vacancy-type defects in silicon–germanium structures grown by molecular-beam epitaxy”, Appl. Phys. Lett., vol. 86, 131923, 2005.
[8] W. X. Ni, A. Henry, M. I. Larsson, K. Joelsson, and G. V. Hansson, “High quality Si/Si1-xGex layered structures grown using a mass-spectrometry controlled electron-beam evaporation system”, Appl. Phys. Lett., vol. 65, pp. 1772-1774, 1994.
[9] T. F. Deutsch, “Infrared laser photochemistry of silane”, J. Chem. Phys., vol. 70, pp. 1187-1192, 1979.
[10] C. T. Lee, H. Y. Lee, and J. H. Cheng, “Crystalline SiGe films grown on Si substrates using laser-assisted plasma-enhanced chemical vapor deposition at low temperature”, Appl. Phys. Lett., vol. 91, 091920, 2007.
[11] L. W. Lai, H. Y. Lee, J. H. Cheng, and C. T. Lee, “Investigation of laser-assisted microcrystalline SiGe films deposited at low temperature”, J. Electron. Mater., vol. 37, pp. 167-171, 2008.
[12] R. People, “Indirect band gap of coherently strained GexSi1-x bulk alloys on <001> silicon substrates”, Phys. Rev., vol. 32, pp. 1405-1408, 1985.
[13] R. People and J. C. Bean, “Band alignments of coherently strained GexSi1-x / Si heterostructures on <001> GeySi1-y substrates”, Appl. Phys. Lett., vol. 48, pp. 538-540, 1986.
[14] A. Levitas, “Electrical properties of germanium-silicon alloys”, Phys. Rev., vol. 99, pp. 1810-1814, 1955.
[15] J. A. Moriarty and S. Krishnamurthy, “Theory of silicon superlattices : Electronic structure and enhanced mobility”, J. Appl. Phys., vol. 54, pp. 1892-1902, 1983.
[16] T. Tatsumi, H. Hirayama, and N. Aizaki, “Si/Ge0.3Si0.7/Si heterojunction bipolar transistor made with Si molecular beam epitaxy”, Appl. Phys. Lett, vol. 52, pp. 895-897, 1988.
[17] S. S. Rhee, J. S. Park, R. P. G. Karunasiri, Q. Ye, and K. L. Wang, “Resonant tunneling through a Si/ GexSi1-x /Si heterostructure on a GeSi buffer layer”, Appl. Phys. Lett., vol. 53, pp. 204-206, 1988.
[18] K. Ismail, B. S. Meyerson, and P. J. Wang, “Electron resonant tunneling in Si/SiGe double barrier diodes”, Appl. Phys. Lett., vol. 59, pp. 973-975, 1991.
[19] H. Dambkes, H. J. Herzog, H. Jorke, H. Kibbel, and E. Kasper, “The n-channel SiGe/Si moduladon-doped filed-effect transistor”, IEEE Trans. Electron Devices, vol. ED-33, pp. 633-638, 1986.
[20] P. J. Wang, B. S. Meyerson, F. F. Fang, J. Nocera, and B. Parker, “High hole mobility in p-type moduladon-doped double heterostructures”, Appl. Phys. Lett., vol. 55, pp. 2333-2335, 1989.
[21] S. M. Sze, “Physics of semiconductor device”, New York: John Wiley & Sons, second ed., 1981.
[22] D. A. Neamen, Semiconductor physics and devices, Mc Graw Hill, 2003.
[23] 施敏, 半導體元件物理與製作技術, 國立交通大學出版社, 2003.
[24] T. F. Deutsch, “Infrared laser photochemistry of silane”, J. Chem. Phys., vol. 70, pp. 1187-1192, 1979.
[25] 李宗翰, “平面顯示器用奈米複晶矽鍺薄膜以及薄膜電晶體的研製”, 國立成功大學微電子工程研究所, 碩士論文, 2006.