超大型積體電路的類比電容中電壓與溫度係數所建立一新精確模擬預估

Abstract

類比與數位混合式積體電路製程中,製造高精確性電容是重要關鍵因素.本 文中將討論對類比電容兩種特性參數: 電壓及溫度參數. 關於溫度參數將 建立一模擬預估式, 針對四種不同電容結構分別比較實驗與模擬之溫度參 數值. 藉由溫度參數模擬預估式可以找出其主要決定項是中間氧化層介電 常數受溫度影響程度多寡.至於電壓參數, 本文引進高載子濃度必需考慮 之能帶窄化效應到一包括考慮SIS型電容能帶彎曲的模擬電容-電壓特性曲 線的模擬程式, 從程式中所萃取的載子濃度與SIMS法所得吻合程度良好. 利用此模擬程式可模擬無法實際求得如WSix層之載子濃度. A new precise C-V model of a semiconduction - insulator - semiconductor (SIS) by using Fermi - Dirac statistics is investigated to replace the Boltzman approximation. The degenerate and bandgap narrowing effect are also taken into consideration. Using the precise model, we get the relationship between electron doping concentration and the Fermi - level. It can also be used to get the precise prediction of surface energy bending, two respective surface charges in the respective capacitors and two respective widths due to surface charge depletion or accumulation. On the other hand, based on the precise C-V model we investigate a new precise simulation prediction of the temperature - coefficient of capacitor (Tcc). It is found that the temperature dependence of dielectric - constant is the major component in Tcc. By lowing the polysilicon doping concentration and thinning oxide thickness, Tcc can be reduced significantly. No matter simulated voltage or temperature - coefficient of capacitor, the most importance of these three parameters for simulation rediction are the oxide thickness, the top and bottom plate carrier doping concentrations of capacitor. To get a low voltage/temperature - coefficient of capacitor, it needs to find the optimize condition of these three parameters.