雜質在假晶型碳矽合金對張力之熱穩定性影響;Effect of impurities on thermal stability of pseudomorphically strained Si:C layer

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题名:	雜質在假晶型碳矽合金對張力之熱穩定性影響;Effect of impurities on thermal stability of pseudomorphically strained Si:C layer
作者:	莊曜滕;Chuang,Yao-Teng
贡献者:	物理研究所
关键词:	碳矽合金;張力之熱穩定性;phosphorus doped;silicon carbon;strain stability
日期:	2012-06-29
上传时间:	2012-09-11 18:40:35 (UTC+8)
出版者:	國立中央大學
摘要:	我們藉由高解析x光繞射儀(HRXRD)及傅立葉轉換紅外線光譜(FTIR)來研究假晶型的碳矽合金在矽基板上的張應力熱穩定性的問題。為了產生夠大的張應力來提升電晶體的載子遷移數度，因此利用了非平衡方式突破碳元素在矽基板中的平衡溶解度來產生夠大的張應力。我們發現無論在只有碳元素的摻雜(C樣品)或多摻雜磷元素(CP樣品)，張應力隨著後段加熱時間的拉長或溫度提升而釋放所保有的張應力，但在氮氣流通加熱的環境下全部張力釋放所需的熱處理條件卻遠低於前人研究需高溫加熱並以β-SiC析出的形成釋放張應力的條件，且CP樣品的全部張力釋放更是遠低於此條件。為了瞭解磷在CP樣品中如何影響張應力的消失，我們以動態模擬的方式來模擬張應力在HRXRD中量測各樣品中的分布趨勢並和(FTIR)做比較且探討張應力釋放的運動方式。從FTIR中我們發現晶格位置上的碳含量(607cm-1)並沒有太大的改變，且過渡帶的碳矽化合物(750cm-1)及β-SiC(810cm-1)的特徵訊號皆無變化，說明了張應力的釋放並非以晶格位置上的碳被置換或β-SiC形成而造成的。另外，我們比較了張力釋放和矽基板的氧化程度並發現兩者有著相似的趨勢的。因為碳元素是有良好的吸引並限制間隙元素的能力且二氧化矽的形成所造成的晶格擴大會產生多餘的間隙矽元素，因此我們推測系統並非以置換晶格位置上的碳元素或β-SiC形成的方式使張應力消失的原因是因為張應力以較低耗能的體積補償方式釋放。雖然在CP樣品中依舊有著和矽基板氧化相似的趨勢，但是張應力卻在表面摻雜磷元素的區域迅速消失，因此我們視磷元素在系統中為另為一種間隙元素來加速張應力的釋放。We investigate the thermal stability of pseudomorphically strained Si:C layer after fully recrystallization using high resolution x-ray diffraction (HRXRD) and Fourier transform infrared (FTIR) spectroscopy. From HRXRD, the strain is relaxed with increasing post-annealing time or temperature as previous study, revealed almost complete strain relaxation in carbon incorporation (C sample). However, we found phosphorus doped Si:C (CP sample) far below the β-Si:C precipitation threshold under nitrogen flow ambient especially. The strain is well defined by HRXRD kinematic simulation in at least five layers concentration distribution and compared to FTIR spectroscopy analysis. Surprisingly, almost complete strain relaxation is found without significant substitutional carbon (Csub) loss (at 607 cm-1). The strain loss is strongly correlated to the Si-O bond (at 1100cm-1) formation and the P doped profile. The above observations indicate interstitial silicon injected by oxidation process and additional phosphorus atoms provide another strain relaxation pathway rather than previously thought mechanism of Csub kicked out from substitutional site and formed β-Si:C precipitation. The volume compensation by forming Csub interstitial complexes rather than Csub diffusing out from substitutional site during the thermal treatment is the most possibility mechanism, due to the fact that carbon is known to be strong gettering center. For CP sample, the interstitial phosphorus is proposed to be taken as additional interstitial source to promote the volume compensation. In summary, we find another pathway, namely the volume compensation, for strain relaxation in pseudomorphicallly strain Si:C alloy. The resultant process yields lower deactivation energy than the β-Si:C precipitation mechanism.
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