氮化鎢化學氣相沉積前驅物在Cu(111)與Si(100) (2x1)表面熱分解反應機制之探討

Abstract

本研究成功的使用程溫脫附法、X光光電子能譜與低能量電子繞射等技術來了解鎢錯合物(t-BuN)2W(NHBu-t)2 (BTBTT)在Cu(111)與Si(100)表面之化學反應。當BTBTT吸附在Cu(111)表面時，由程溫脫附法之結果得知，反應過程會有第三丁基胺、異丁烯、乙腈 和氫氣 等氣態產物脫離表面。另外、當前驅物熱裂解反應結束後，X光光電子能譜顯示，在700 K左右在Cu(111)表面上會形成氮化鎢的薄膜。若將基材表面由Cu(111)改成Si(100)時，BTBTT在Si(100)表面會裂解而脫附出第三丁基胺、異丁烯、和氫氣等。當前驅物熱裂解反應結束後，在Si(100)表面形成鎢金屬與碳化矽和氮化矽之薄膜。上述之實驗結果顯示當BTBTT在Si(100)吸附表面時，分子之配位基會次序轉移至基材上形成鎢金屬，再配位基裂解形成碳化矽與氮化矽。若使用另外一個氮化鎢前驅物(t-BuN=)2W(NEt2)2, bis(tert-butylimido)bis(diethylamido)tungsten (BTBDT)，當其在900 K時，在Si(100)表面依舊會形成鎢金屬與碳化矽和氮化矽之薄膜。但若將Si(100)用O2+ 鈍化而形成SiO2之表面，BTBDT在高溫時會在此表面形成氮化鎢與碳化鎢之薄膜。相同的前驅物當其使用的基材不同時，其最後所形成之薄膜卻不同，此點說明了基材表面之反應性扮演一關鍵之角色。

Thermal decomposition of (t-BuN)2W(NHBu-t)2, bis(tertbutylimido)bis (tertbutylamido)tungsten (BTBTT), a tungsten nitride CVD precursor, on Cu(111) and Si(100)(2´1) surfaces have been investigated separately by means of temperature programmed desorption (TPD), synchrotron-based X-ray photoelectron spectroscopy (SR-XPS) and low-energy electron diffraction (LEED). For the thermal decomposition of BTBTT on Cu(111), TPD results indicate the formation of various products that include t-butylamine generated from a-H abstraction, isobutylene from g-H elimination, acetonitrile from b-methyl elimination, and hydrogen. After annealing to 700 K, tungsten nitride is formed on the Cu(111) surface. In comparison, the thermal decomposition of BTBTT on Si(100) produces thin films that consist of tungsten metal, silicon carbide and silicon nitride. The volatile desorption products are originated from the ligands of the precursor and they include t-butylamine derived form a recombination of t-butylamido ligands, and isobutene generated from g-H elimination of t-butylimido ligands. Transmetalation of the BTBTT produces tungsten metal on Si(100) surface; by contrast, tungsten nitride is produced as the same precursor is decomposed on Cu(111) surface. Thermal decomposition of a similar CVD precursor, (t-BuN=)2W(NEt2)2, bis(tert-butylimido)- bis(diethylamido)tungsten (BTBDT), on Si(100) produces nearly the same products of tungsten metal, silicon carbide and silicon nitride. This is to be compared with the end product of tungsten carbonitride as BTBDT is thermally decomposed on SiO2. The observation of different decomposition products from different surfaces indicates the importance of surface electronic property in determining the reaction pathways.