高密度電漿化學氣相沉積製備低介材SiOC:H 之薄膜特性研究

Abstract

本論文為低介材 SiOC:H 薄膜的製備方式與其製程整合性質之探討。薄膜製備採高密度電漿（感應耦合電漿）化學氣相沉積，沉積主要參數為3MS/N2O 比例、基材溫度、ICP 功率、偏壓4參數。 沉積最佳參數為壓力250 mTorr，3MS/N2O氣體流量比0.15，沉積溫度90℃，ICP功率250 W。薄膜介電常數值為2.45。前述參數成長之薄膜經400℃回火一小時後，介電常數可由2.45降至2.07；以鋁為電極，於電場強度1 MV/cm時，漏電流密度約4.28×10-9 A/cm2，呈現良好電特性。薄膜於500℃回火後，因 Si-CH3 鍵逐漸分解脫附，產生微孔，600℃回火後產生之微孔又大又多，顯示薄膜熱穩定性於400℃回火仍具有良好性質，極限應為500℃左右。經回火後，Si-O-Si 類籠狀結構經過分子重排，逐漸轉換成 Si-O-Si 網狀結構。 未加偏壓之薄膜，以銅為電極，於電場強度1 MV/cm時，漏電流密度介於 9.45×10-9 A/cm2至3.94×10-8 A/cm2之間，加偏壓之試片漏電流密度均變大，最差的達到 4.35×10-6 A/cm2，顯示未加偏壓之試片在漏電流密度上具有較佳的電特性，並具良好銅原子阻障性質。 SiOC:H 如經最適化參數製備，提升機械強度與降低熱膨脹係數，有潛力應用為 90 nm節點，介電常數 <2.2之超低介材。

In this thesis, the preparation of low-k SiOC:H film and its properties of process integration were studied. All thin film depositions were carried out in High Density Plasma (ICP) CVD system. The major deposition parameters were 3MS (Trimethylsilane) / N2O (Nitrous Oxide) ratio, substrate temperature, ICP power, and bias. The optimal parameters of deposition are chamber pressure 250 mTorr, 3MS/N2O ratio 0.15, substrate temperature 90℃, ICP power 250W. The dielectric constant of thin film was measured as 2.45. The annealing of thin film prepared from above parameters at 400℃ for 1 hr, dielectric constant was reduced from 2.45 to 2.07. Under electric strength 1 MV/cm, Al-gate leakage current density was 4.28×10-9 A/cm2, good electrical characteristic property was shown. Annealing at 500℃, the Si-CH3 bond breaking and desorption gradually happened, then, small pores produced. When annealing at 600℃, the pores grew more and larger, indicating the film’s thermal stability can be kept after 400℃ annealing, and limitation was estimated at about 500℃. After annealing, the Si-O-Si caged-like structure was transformed to network structure through molecular rearrangement. Without bias, Cu-gate leakage current density was between 9.45×10-9 A/cm2 to 3.94×10-8 A/cm2 under 1 MV/cm . When bias was applied, the leakage current of samples became greater and the worst value was 4.35×10-6 A/cm2. The samples without bias will have better electrical and barrier properties. If SiOC:H film was prepared by optimized parameters, and mechanical strength raised, thermal expansion coefficient decreased, will have the potential to be used in 90 nm node as ultra low-k material with dielectric constant <2.2.