Please use this identifier to cite or link to this item: http://hdl.handle.net/11455/9963
標題: The preparation and characterization of large grain silicon seeding layer on alumina substrates
在氧化鋁基板上成長大晶粒矽種晶層之製備與分析
作者: 陳茂越
關鍵字: 多晶矽薄膜
固化結晶法
電子遷移率
出版社: 材料工程學研究所
摘要: 摘要 本研究是以氧化鋁作為基板而實驗中分為兩組,一組試片是在氧化鋁基板上直接沉積1.5μm的非晶矽薄膜(Si/Al2O3),另一組則是在氧化鋁基板上先以電子束蒸鍍上0.5μm的鋁,之後再以PECVD的方式沉積1.5μm的非晶矽薄膜(Si/Al/Al2O3)。藉由不同條件的熱處理後以探討不同熱處理條件對結晶性、微結構、晶體結構及電性分析方面的影響。本實驗中藉由X光繞射儀(X-ray diffractometer)、場發射掃描式電子顯微鏡(FE-SEM)、穿透式電子顯微鏡(TEM)及霍爾效應量測系統(Hall Effect Measurement System)等儀器分析其性質及微結構。 由Si/Al2O3試片在Ar/H2與Ar氣氛下熱處理後的X光繞射結果顯示,Si/Al2O3試片經熱處理後已有矽的繞射峰產生,但由實驗結果顯示其晶粒太小約為15~20nm不適用於作為太陽能電池之種晶層,因此在實驗中改用Si/Al/Al2O3試片,藉由高溫及鋁、矽之間相互擴散而結晶的效應以期得到較大之晶粒。由X光繞射結果顯示鋁的繞射峰強度隨著隨著熱處理時間增加而降低,也就是說氧化效應隨著熱處理時間增加而上升,並且熱處理溫度越高其效應越明顯。由FE-SEM的照片中可以觀察到矽種晶層為雙層結構,底層的部分厚度非常平均並會隨著基材的表面形貌而改變,但在熱處理溫度為900℃時則底層的部分變得較為粗糙且看得到有部分的鋁殘留在其中,而在上層的晶粒大小約6μm。由霍爾效應的結果中發現熱處理溫度升高而電子遷移率下降,推測其原因為熱處理溫度升高後,種晶層中的鋁含量增加,使得之後鍍著的多晶矽薄膜中的摻雜濃度增加,並且溫度越高氧化效應越嚴重,而使得電子遷移率降低。而在熱處理條件為700℃、1小時的時候得到最大的電子遷移率50cm2/V•sec,推測其原因為熱處理時間增加讓矽晶粒當中的鋁原子有足夠的時間擴散出來,因此當鋁蝕刻完鍍著上多晶矽薄膜後其中的鋁原子濃度因而降低,使得電子遷移率提高。但在900℃時則因為氧化效應隨著時間增加而越趨嚴重,因此在900℃時熱處理時間增加而電子遷移率開始下降。
Abstract In this paper we used alumina as the substrate for thin film solar cell . There were two kinds of specimens in this investigation. One was Si/Al2O3 and the other Si/Al/Al2O3. The effect of the heat treatment to crystallization, microstructure, crystal structure and electrical properties were investigated by changing the heat treatment conditions. The crysta- llization, microstructure, crystal structure and electrical property were characterized by X-ray diffractometer, FE-SEM, TEM and Hall effect measurement system. The results of X-ray diffraction of the Si/Al2O3 specimens after annealing in the atmospheres of Ar/H2 and Ar show that the grain size is about 15~20nm, which is too small to be the seeding layer of thin film solar cell. In order to obtain bigger grains, we changed the specimen to Si/Al/Al2O3 in this study. Because of the effects of high temperature and interdiffusion between aluminum and silicon the average grain size becomes bigger. The result of X-ray diffraction shows the intensity of aluminum is getting lower when the annealing time is longer. And it is more obviously when the annealing temperature is higher. It was suggested that the oxidation is more serious when the annealing time is longer and the annealing temperature is higher. In the photograph of FE-SEM, it can be seem that there are double layers in the silicon seeding layer. While annealing at 900℃, the part of lower layer becomes more rough and it shows there is some aluminum remaining in it. The average grain size at the upper layer is about 6μm estimated from cross-section pictures. Hall effect measurement shows that the mobility decrease with increasing the annealing temperature. It was suggested that there is more aluminum in the seeding layer when the annealing temperature is higher. At the mean time, the higher annealing temperature makes the more serious oxidation. More aluminum in the seeding layer increases the concentration of aluminum in the polysilicon layer and therefore the mobility decreases. The effect of the oxidation may also lower the mobility. In this study the biggest mobility was obtained with annealing at 700℃ for 1hr. A possible reason is that more impurities diffuse out from silicon. This makes the concentration of aluminum lower in the polysilicon layer after etching, and increase the mobility. However, the oxidation is more serious at 900℃ for longer annealing time. And that may make the mobility lower with the longer annealing time at 900℃.
URI: http://hdl.handle.net/11455/9963
Appears in Collections:材料科學與工程學系

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