Ni/Ti/Si形成硅化物的特性分析
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摘要
随着MOSFET的特征尺寸进入20nm技术节点,源漏接触电阻成为源漏寄生电阻的主导部分,后栅工艺对硅化物的高温特性提出了更高的要求。分析了Ni/Ti/Si结构在不同温度退火下形成的硅化物的薄膜特性和方块电阻。分别采用J-V和C-V方法,提取硅化物与n-Si(100)接触的势垒高度。Ni/Ti/Si结构形成的镍硅化物在高温下具有良好的薄膜特性,并且可以得到低势垒的肖特基接触。随着退火温度的升高,势垒高度逐渐降低。研究了界面态的影响,在低于650℃的温度下退火,界面态密度随退火温度升高而逐渐增大,高于750℃后,界面电荷极性翻转。
As feature size of MOSFETs shrinks to 20nm,source/drain contact resistance has become a dominant portion of source/drain parasitic resistance.Meanwhile,post gate processes demand that silicide should remain stable at high temperature.Film characteristics and sheet resistance of silicide formed with Ni/Ti/Si at different temperatures were analyzed.J-Vand C-V methods were used to extract barrier height of Schottky contact.Silicide formed with Ni/Ti/Si structure had a uniform thickness at high temperature,and it also led to Schottky contact with low barrier height.Barrier height decreased with increasing annealing temperature.Effects of interface states were investigated.It was found that interface state density increased with annealing temperature when it was below 650 ℃,and interface charge polarity reversed after 750℃annealing.
As feature size of MOSFETs shrinks to 20nm,source/drain contact resistance has become a dominant portion of source/drain parasitic resistance.Meanwhile,post gate processes demand that silicide should remain stable at high temperature.Film characteristics and sheet resistance of silicide formed with Ni/Ti/Si at different temperatures were analyzed.J-Vand C-V methods were used to extract barrier height of Schottky contact.Silicide formed with Ni/Ti/Si structure had a uniform thickness at high temperature,and it also led to Schottky contact with low barrier height.Barrier height decreased with increasing annealing temperature.Effects of interface states were investigated.It was found that interface state density increased with annealing temperature when it was below 650 ℃,and interface charge polarity reversed after 750℃annealing.
引文
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[2]TUNG R T,LEVI A F J,SULLIVAN J P,et al.Schottky-barrier inhomogeneity at epitaxial NiSi2interfaces on Si(100)[J].Phys Rev Lett,1991,66(1):72-75.
[3]NAKATSUKA O,SUZUKI A,SAKAI A,et al.Electrical properties of epitaxial NiSi2/Si contacts with extremely flat interface formed in Ni/Ti/Si(001)system[J].Microelec Engineer,2006,83:2272-2276.
[4]CHIU S L,CHU Y C,TSAI C J,et al.Effects of Ti interlayer on Ni/Si reaction systems[J].J Electrochem Soc,2004,151(7):G452-G455.
[5]LIM P S Y,CHI D Z,ZHOU Q,et al.NiSi2formation through annealing of nickel and dysprosium stack on Si(100)and impact on effective Schottky barrier height[J].J Appl Phys,2013,113:013712.
[6]CHEUNG S K,CHEUNG N W.Extraction of Schottky diode parameters from forward currentvoltage characteristics[J].Appl Phys Lett,1986,49:85-87.
[7]GOODMAN A M.Metal-semiconductor barrier height measurement by the differential capacitance method—one carrier system[J].J Appl Phys,1963,34:329-338.
[8]SULLIVAN J P,TUNG R T,PINTO M R,et al.Electron transport of inhomogeneous Schottky barriers:a numerical study[J].J Appl Phys,1991,70:7403-7424.
[9]CARD H C,RHODERICK E H.Studies of tunnel MOS diodes I.interface effects in silicon Schottky diodes[J].J Phys D:Appl Phys,1971,4:1589-1601.
[10]MAMOR M.Interface gap states and Schottky barrier inhomogeneity at metal/n-type GaN Schottky contacts[J].J Phys:Conden Matter,2009,21:335802.
[11]AHAITOUF A,SROUR H,HAMADY S O S,et al.Interface state effects in GaN Schottky diodes[J].Thin Solid Films,2012,522:345-351.
[12]SELLAI A,OUENNOUGHI Z.Analysis of frequencyand temperature-dependent interface states in PtSi/p-Si Schottky diodes[J].Mater Sci Eng,B,2008,154-155:179-182.