微波電子迴旋共振電漿物理氣相沉積法於矽晶片上沉積Si-C-N薄膜及其特性分析

Abstract

微波電子迴旋共振電漿物理氣相沉積法( Microwave ECR plasma PVD )，以Si (100)或Si加石墨為靶材，以甲烷及氮氣為反應氣體，沉積非晶質Si-C-N薄膜於Si (100)基材，探討各種沉積條件對薄膜性質的影響。利用電子能譜化學分析技術( ESCA或XPS)和傅立葉轉換紅外線光譜技術( FTIR )分別做Si-C-N薄膜之組成及鍵結分析；奈米壓痕技術(NIP)量測薄膜之奈米機械性質；X光繞射(XRD)來分析薄膜的晶體結構；原子力顯微技術(AFM)和穿透式電子顯微技術(TEM)分析薄膜表面形貌及內部結構；陰極螢光光譜技術(CL) 測定薄膜能隙；並且利用I-V量測技術以測描薄膜表面電子場效發射特性(Electron field emission properties)。實驗結果可歸結如下： 在沉積參數對成分之影響方面，當靶材負偏壓低於500 V，且真空度低於4x10-5 torr且使用矽靶材時，薄膜成分原子百分比為Si：N：C：O = 12.9∼32.6：11.3∼25.1：21.9∼44.2：18.6∼41.2。若靶材偏壓為500 V，且真空度高於4x10-6 torr且使用矽加石墨為靶材時，薄膜成分原子百分比變為Si：N：C：O = 12.5~21.2：15.0~21.5：44.0~55.6：11.2~19.5。顯示提高真空度或靶材濺射率（提高靶材負偏壓或加入石墨靶材）是降低薄膜氧含量或提高碳含量的最有效途徑，對於矽和氮含量則變化不大。 在硬度方面，氧含量越低或沉積溫度越高，可得較高的硬度。量測最高硬度可達46.5 GPa，由FTIR與XPS的鍵結分析結果推測可能與C=N，C≡N或Si-C鍵結量的提高有關。在能隙方面，CL在可見光波長(=200~700 nm)的量測範圍內並無明顯訊號峰，僅有三片高溫（750℃）試片在400 nm (= 4.0 eV) 附近有微弱訊號。在場效發射特性方面，氧含量低於20 at.％之Si-C-N薄膜其最低之啟動電場強度為12 V/mm，最大之電流密度為2.8 mA/cm2

Amorphous Si-C-N films were deposited on Si(100) substrate by microwave ECR plasma PVD method with Si(100) or Si + graphite as targets and with CH4 + N2 as source gases. Effects of deposition parameters on film properties were examined. Electron spectroscopy for chemical analysis (ESCA or XPS) was used to determine the film compositions; Fourier transform infrared (FTIR) spectroscopy to study the film bonding; nano-indentation technique to estimate the mechanical properties of the films; XRD to determine the crystal structure of the films; atomic force microscopy (AFM) and TEM to examine the film morphologies and microstructures; cathodoluminescence (CL) spectroscopy to measure the band gap of the films and the I-V measurement to characterize the filed emission properties of the films. From the experimental results, the following conclusion can be drawn: On film compositions, at negative bias voltage < 500 V, background pressure > 4 x 10-5 torr and Si as target material, the atomic percentages of Si : N : C : O are 12.9 ~ 32.6 : 11.3 ~ 25.1 : 21.9 ~ 44.2 : 18.6 ~ 41.2; in contrast, at negative bias voltage = 500 V, background pressure < 4 x 10-6 torr and Si + graphite as target materials, the atomic percentages of Si : N : C : O become 12.5 ~ 21.2 : 15.0 ~ 21.5 : 44.0 ~ 55.6 : 11.2 ~ 19.5. The results indicate that an increase in vacuum level or sputtering rate of the target (by increasing negative bias voltage or adding graphite target) are effective ways to decrease the O content or to increase C content of the films, but no significant effects on Si and N contents. On nano-hardness, a decrease in O content of the films or an increase in deposition temperature can result in an increase in film hardness. The maximum hardness of the films can reach 46.5 GPa, which may relate to an increase in amount of C=N, CºN or Si-C bondings in the films from FTIR and XPS studies. On band gap of the films, the films show no significant CL peak signals in the visible range (wavelength = 200 ~ 700 nm ), except three samples at higher deposition temperature 750℃, a weak signal at ~ 400 nm (= 4.0 eV) can be detected. On field emission properties, for the films with O at % < 20, the lowest turn-on field intensity and maximum current density are 12 V/mm and 2.8 mA/cm2 , respectively.