以射頻磁控濺鍍法沉積銅銦鎵金屬前驅層及後硒化製備銅銦鎵硒吸收層之研究

Investigation of Copper Indium Gallium Metallic Precursor Layer Deposited by RF Magnetron Sputtering and Its Selenization for CIGS Absorb Layer

楊育貞(Yu-Chen Yang)

指導教授 ： 蔡丕椿

共同指導教授 ： 連水養

國立虎尾科技大學/工程學院/材料科學與綠色能源工程研究所/碩士(2011年)

https://doi.org/10.6827/NFU.2011.00132

摘要

本論文利用射頻磁控濺鍍法製備不同元素比例之銅銦鎵 (Copper indium gallium, CIG) 金屬前驅層於玻璃基板上，探討不同製程參數如製程功率、氬氣流量、基板溫度及製程壓力對於 CIG 膜層特性的影響。本實驗製備四種不同比例之銅銦鎵三元合金靶，銅:銦:鎵比例分別為1: 0.9: 0.1；1: 0.7: 0.3；1: 0.5: 0.5 和0.5: 0.7: 0.3，並分析不同比例之合金靶所沉積之銅銦鎵薄膜之特性，其中利用表面輪廓儀、場發射掃描電子顯微鏡、X光繞射分析儀及X光光電子能譜儀來進行薄膜特性之分析。
由實驗分析結果發現，當使用銅銦鎵比例為 1: 0.7: 0.3的三元靶，在功率100 W、流量20 sccm、溫度50 °C與壓力10 mTorr下，製備CIG薄膜具有其沉積速率快、結晶性佳與晶粒最大之特性。最佳參數之 CIG 薄膜顯示出強烈的峰值於 42.47? 之 ( 4 1 1 ) 優選方向，另一方面，其他峰值位於 29.72° 和 34.34°，顯現出 ( 3 0 0 ) 和 ( 2 2 2 ) 的繞射峰。 SEM 分析結果可看出，最佳參數之 CIG 薄膜表面形貌更為均勻緻密，且晶粒也更為粗大。
再利用後硒化退火製程使金屬前驅層轉變為銅銦鎵硒 (Copper indium gallium selenide, CIGS) 薄膜，比較四種靶材比例硒化後，由ESCA分析可發現，在銅銦鎵比例為 1:0.5:0.5的條件下，最為接近文獻上銅銦鎵硒(Cu(In,Ga)Se2)薄膜的最佳成份比例，與其他靶材比例相比，其硒化深度也較深。最後，再利用不同硒化方式處理，可發現在氫還原反應後硒化、坩鍋式硒化以及CuIn0.7Ga0.3Se2靶材後硒化下，皆能使硒化更深，得到較佳的CIGS薄膜。其最佳化參數之 CIGS 薄膜顯示出強烈的峰值於 26.62° 之 (1 1 2) 優選方向，另外位於 44.31° 和 52.48°，則顯示出 (2 2 0) 和 (3 1 2) 平面的繞射峰，這些量測訊號顯示優化後之 CIGS 薄膜為結晶性良好的黃銅礦結構，而黃銅礦結構為 CIGS 薄膜太陽能電池之吸收層對於全光譜為高吸收係數的重要因素之一。經過以上量測結果可得知，此優化後之CIGS 薄膜即為 CIGS 吸收層所需之 P-type 薄膜。
最後本文將探討不同靶材參數優化後之 CIG 薄膜進行標準硒化退火製程的特性，進一步評估利用不同元素比例靶材所製備CIG前驅層在 CIGS 太陽電池之應用。

關鍵字

銅銦鎵 ； 銅銦鎵硒 ； 射頻磁控濺鍍 ； 吸收層 ； 薄膜太陽能電池

並列摘要

In this study, the copper indium gallium (CIG) metal precursor films with different composition ratio on glass substrate by using RF magnetron sputtering to investigate the influences of the process parameters including the power, Ar gas flow rate, substrate temperature and pressure. The characteristics of CIGS films prepared by using four different sputtering targets with corresponding Cu:In:Ga ratios of 1: 0.9: 0.1, 1: 0.7: 0.3, 1: 0.5: 0.5 and 0.5: 0.7: 0.3. In this study, the films are characterized by using alpha-step, scanning electron microscopy, X-ray diffraction and X-ray photoelectron spectroscopy.
The CIGS films with a high deposition rate, high crystallinity, flat surface and largest grain size when using the sputtering target with a Cu:In:Ga of 1:0.7:0.3, power of 100 W, Ar flow rate of 20 sccm, temperature of 50 °C and pressure of 10 mTorr. From the XRD results, the optimal CIG thin film shows a strong peak at 42.47? of (4 1 1) preferred orientation and other peaks at 29.72° of (3 0 0) and 34.34° of (2 2 2). The SEM results clearly show a larger grain size and better film uniformity.
After a selenization annealing, the metallic precursors transform into CIGS thin film. We discuss the influence of different selenization treatment on the properties of the CIGS films. It can be found for sample with hydrogen reduction treatment, sample selenization in crucible and sample with CuIn0.7Ga0.3Se2 precursor, the thickness of selenization layer were thicker than the other samples. CIGS thin films with better quality were obtained in these cases.
The optimal CIGS thin film shows a strong peak at 26.62° of (111) preferred orientation and other peaks at 44.31° of (220) and 52.48° of (312), representing the film is well crystallized with chalcopyrite structure, which is an important factor for CIGS thin films having a high absorption coefficient over the whole solar spectrum. From the above measurement results, the optimal CIGS thin film can fit the requirements of a CIGS P-type absorber layer.
Finally we fabricate solar cells on glass substrate with different CIG thin films, which were sputtered from different composition ratio targets, and the cell characteristics are also presented for further assessing the use of the CIG precursor layers for thin-film solar cell applications.

並列關鍵字

CIG ； CIGS ； RF magnetron sputtering ； Absorber thickness ； Selenization ； Thin-film solar cells

參考文獻

[1] N. G. Dhere, Sol. Energ. Mat. Sol. C. 90 (2006) 2181.

[2] A. D. Compaan, Sol. Energ. Mat. Sol. C. 90 (2006) 2170.

[4] T. Dullweber, G. Hanna, et al., Sol. Energ. Mat. Sol. C. 67 (2001) 145-150.

[5] L. L. Kazmerski, M. Hallerdt, et al., Vac. Sci. Technol. A 1 (1983) 395.

[6] Miguel A, Contreras K, et al. Prog Photovolt: Res Appl (2005)