利用溶膠法探討不同溶液製備之鉿金屬氧化層經不同退火溫度處理之特性

Abstract

矽型微電子元件的微縮已經導致了做為閘極介電質的SiO2層產生大的漏電，因此以高介電常數(高κ)氧化物來取代SiO2是必要的。 溶膠法具有吸引力扮演低溫路徑來製備氧化物。溶膠法的低製作成本與簡單技術使易實現薄膜製備成為可能。 使用四氯化鉿原物料是依據表面溶膠法，膠為一種固態物質包含於液態成份中。四氯化鉿(98% Aldrich)與乙醇(≥99.8% Fluka)不需要進一步純化即可被使用。前驅物溶液被製備是先將四氯化鉿溶解進乙醇並攪拌十分鐘於室溫下，然後緩慢加入正乙醇並再攪拌十分鐘。各成分的莫耳比為HfCl4: EtOH: CH3(CH2)5OH = 1: 80: 10，以這樣莫耳比所製作出的樣本具有較佳的效能。. 溶膠的表面、架構與電子特性使得HfO2被發明。當薄膜被以室溫置放在空氣中1-4天後，水滴接觸角會達到常數值介於80°到100°之間，這表示薄膜表面具有疏水性。即使薄膜被有機溶劑處理過其疏水性仍可以被維持。掃描電子顯微鏡檢查法顯示薄膜表面是平坦且均勻的。當後沉積退火溫度在500°C至550°C之間，薄膜中的HfO2會結晶化成為單晶相，並且一直觀查到800°都不會有其它晶相出現。薄膜的折射指標與光學間隙分別為1.88-1.93與5.1 eV。 我們可以從先前的結果建立出表面溶膠處理法來使高品質HfO2薄膜的溶液製造能成功。表面薄膜處理法根據前驅物質的化學吸收，特別適合於維持大表面面積的奈米薄膜均勻度。反面來看，以旋轉塗佈形成的非結晶形的奈米薄膜將造成奈米顆粒與較少同質金屬氧化網狀物與較差的電子特性。 在論文中，用快速退火處理二氧化鉿絕緣層可以有效改善絕緣層特性。根據實驗結果，快速退火處理可以有效消除絕緣層中的缺陷和HfO2/ SiO2的介面層，進而改善二氧化鉿的品質和可靠度。除此之外我們也研究了二氧化鉿閘極漏電對溫度的相關性，經由數據結果分析出是F-P漏電機制。而漏電對電場的相關性，經由數據結果分析出是F-N漏電機制。 我們已經製備出一Al/HfO2/SiO2(IL)/Si/Al閘極堆疊電容器於不同退火溫度有關OFET的應用。

The scaling of silicon-based microelectronics devices has led to large leakage current of the silicon dioxide layer as a gate dielectric. It is necessary to replace the SiO2 with high dielectric constant (high-κ) oxides. The sol-gel method has attracted attention as a low temperature route to oxide materials. Facile film fabrication is possible with low operation costs and simple facilities. Using hafnium chloride (HfCl4) source by the surface sol-gel method, a gel is a solid material network containing a liquid component. Hafnium(IV) tetrachloride (98% Aldrich) and ethanol (≥99.8%Fluka) were used without further purification. The precursor solution was prepared by dissolving HfCl4 in ethanol stirred for 10min, then 1-hexanol was added slowly and the mixture was stirred for 10min at room temperature. The molar ratios of the components were: HfCl4: EtOH: CH3(CH2)5OH = 1: 80: 10. The molar ratio of the sample has the better performance. The surface and structural and electric properties of sol-gel derived HfO2 films have been investigated. The water droplet contact angles reached constant values between 80 and 100° after the films were left for 1-4 days in air at ambient temperature, indicating that the film surface exhibited hydrophobicity. Hydrophobicity was maintained even after the films were treated with organic solvents. Scanning electron microscopy observation showed that the film surface was smooth and uniform. The HfO2 in the films crystallized to the monoclinic phase at post deposition annealing temperatures between 500 and 550°C and no other phases were observed to 800°C. The refractive index and optical gap of the films were 1.88-1.93 and 5.1 eV, respectively. It is established from the preceding results that the surface sol-gel process enables solution-based fabrication of high quality HfO2 films. The surface sol-gel process, as based on chemical sorption of precursor materials, is particularly suitable for maintaining nano-film uniformity over a wide surface area. In contrast, formation of amorphous nano-films by spin-coating leads to nano-grains and less-homogeneous metal oxide network and inferior electrical properties. In this thesis, the improved characteristics of hafnium dielectrics with rapid thermal annealing are investigated. Based on the experimental results, the rapid thermal annealing can effectively improve the reliability and quality of hafnium dioxide owing to the elimination of traps in the dielectrics and interfacial layer between HfO2 and SiO2. Besides, we report the temperature dependence of gate leakage current by way of the data result analysis is F-P tunneling. The electric field dependence of gate leakage current by way of the data result analysis is F-N tunneling. We have fabricated a Al/HfO2/SiO2(IL)/Si/Al gate stack capacitor during the different annealing temperature for OFET application.