TMA와 IPA를 이용해 ALD법으로 증착된 Al₂O₃ 박막의 증착 기구와 특성에 관한 연구 (A) study on the deposition mechanism and characteristics of Al₂O₃ films deposited by atomic layer deposition using TMA and IPA원문보기
$Al_2O_3$는 높은 유전율과 낮은 누설전류 특성때문에 미래의 Si을 기반으로한 집적회로에서 $SiO_2$를 대치할 게이트 유전체로 여겨지고 있다. 본 연구에서는, 비정질 $Al_2O_3$ ...
$Al_2O_3$는 높은 유전율과 낮은 누설전류 특성때문에 미래의 Si을 기반으로한 집적회로에서 $SiO_2$를 대치할 게이트 유전체로 여겨지고 있다. 본 연구에서는, 비정질 $Al_2O_3$ 박막을 p형-Si(100)기판위에 원자단위 증착법으로 TMA와 IPA를 사용하여 250 ℃에서 성공적으로 증착하였다. 박막의 증착기구는 원자단위 증착의 개념을 이용하여 연구하였고 우수한 특성의 박막을 얻었다. TMA와 IPA를 이용해 원자단위 증착할때 가능한 온도범위는 230 ℃에서 290 ℃사이였다. $Al_2O_3$를 250 ℃, 0.01 torr의 TMA분압, 0.1 torr의 IPA분압에서 원자단위로 증착하기 위한 최적의 조건을 얻기 위해 TMA 주입시간에 따른 cycle당 증착두께와 IPA 주입시간에 따른 cycle당 증착두께에 대한 연구를 하였다. 완전히 포화된 cycle당 증착두께를 얻기위한 최소한의 TMA, IPA주입 시간은 각각 2초, 1초였고 포화된 cycle당 증착두께는 0.8 Å/cylce이였다. 이는 0.37 ML(monolayer)/cycle에 해당한다. 또한 증착한 $Al_2O_3$ 박막의 굴절율은 1.61과 1.62사이 값을 보였다. 또한 굴절율은 TMA 주입시간에는 영향을 받지 않았지만 IPA 주입시간에는 영향을 받았다. 증착한 박막의 조성은 XPS에의해 분석했으며, 탄소 불순물개제는 SIMS에 의해 분석하였다. 분석결과 약간 산소성분이 많은 stoichiometric $Al_2O_3$에 가깝고 탄소 개제가 없는 박막임이 확인되었다. 박막의 결정구조는 XRD를 이용해 분석해 본 결과 열처리에 관계없이 비정질임이 확인되었다. AFM을 이용해 박막의 표면거칠기를 분석해본 결과 열처리에 관계없이 모든 박막의 표면 거칠기는 수 Å에 불과했다. 또한 XPS와 TEM을 이용해 박막의 계면을 관찰해 본 결과, as-deposited의 경우는 계면에 $SiO_2$가 형성되지 않았고 열처리한 박막의 경우에는 계면에 $SiO_2$가 형성되었다. 박막의 전기적 특성을 I-V, C-V 측정방법을 이용해 분석해 본 결과 누설전류는 열처리한 경우 1 MV/cm에서 $10^-8 A/cm^2$ 정도의 낮은 누설전류값을 보였고 유전율은 약 10 정도를 보였다. 이는 등가 산화막 두께로 환산할때 80 Å의 $Al_2O_3$를 증착하면 30 Å의 $SiO_2$ 두께에 해당한다. 따라서, TMA와 IPA를 이용해 원자단위 증착법으로 증착한 $Al_2O_3$박막은 향후 sub-0.2㎛ 소자에 유전체로서 사용될수 있는 훌륭한 후보물질임을 확인하였다.
$Al_2O_3$는 높은 유전율과 낮은 누설전류 특성때문에 미래의 Si을 기반으로한 집적회로에서 $SiO_2$를 대치할 게이트 유전체로 여겨지고 있다. 본 연구에서는, 비정질 $Al_2O_3$ 박막을 p형-Si(100)기판위에 원자단위 증착법으로 TMA와 IPA를 사용하여 250 ℃에서 성공적으로 증착하였다. 박막의 증착기구는 원자단위 증착의 개념을 이용하여 연구하였고 우수한 특성의 박막을 얻었다. TMA와 IPA를 이용해 원자단위 증착할때 가능한 온도범위는 230 ℃에서 290 ℃사이였다. $Al_2O_3$를 250 ℃, 0.01 torr의 TMA분압, 0.1 torr의 IPA분압에서 원자단위로 증착하기 위한 최적의 조건을 얻기 위해 TMA 주입시간에 따른 cycle당 증착두께와 IPA 주입시간에 따른 cycle당 증착두께에 대한 연구를 하였다. 완전히 포화된 cycle당 증착두께를 얻기위한 최소한의 TMA, IPA주입 시간은 각각 2초, 1초였고 포화된 cycle당 증착두께는 0.8 Å/cylce이였다. 이는 0.37 ML(monolayer)/cycle에 해당한다. 또한 증착한 $Al_2O_3$ 박막의 굴절율은 1.61과 1.62사이 값을 보였다. 또한 굴절율은 TMA 주입시간에는 영향을 받지 않았지만 IPA 주입시간에는 영향을 받았다. 증착한 박막의 조성은 XPS에의해 분석했으며, 탄소 불순물개제는 SIMS에 의해 분석하였다. 분석결과 약간 산소성분이 많은 stoichiometric $Al_2O_3$에 가깝고 탄소 개제가 없는 박막임이 확인되었다. 박막의 결정구조는 XRD를 이용해 분석해 본 결과 열처리에 관계없이 비정질임이 확인되었다. AFM을 이용해 박막의 표면거칠기를 분석해본 결과 열처리에 관계없이 모든 박막의 표면 거칠기는 수 Å에 불과했다. 또한 XPS와 TEM을 이용해 박막의 계면을 관찰해 본 결과, as-deposited의 경우는 계면에 $SiO_2$가 형성되지 않았고 열처리한 박막의 경우에는 계면에 $SiO_2$가 형성되었다. 박막의 전기적 특성을 I-V, C-V 측정방법을 이용해 분석해 본 결과 누설전류는 열처리한 경우 1 MV/cm에서 $10^-8 A/cm^2$ 정도의 낮은 누설전류값을 보였고 유전율은 약 10 정도를 보였다. 이는 등가 산화막 두께로 환산할때 80 Å의 $Al_2O_3$를 증착하면 30 Å의 $SiO_2$ 두께에 해당한다. 따라서, TMA와 IPA를 이용해 원자단위 증착법으로 증착한 $Al_2O_3$박막은 향후 sub-0.2㎛ 소자에 유전체로서 사용될수 있는 훌륭한 후보물질임을 확인하였다.
Al_(2)O_(3) is considered as the most promising alternative to SiO_(2) for a gate dielectric materials in future Si-based integrated circuits owing to its high dielectric constant and low leakage current. In this study, amorphous Al_(2)O_(3) films on p-Si(100) at 250 ℃ have been successfully grown b...
Al_(2)O_(3) is considered as the most promising alternative to SiO_(2) for a gate dielectric materials in future Si-based integrated circuits owing to its high dielectric constant and low leakage current. In this study, amorphous Al_(2)O_(3) films on p-Si(100) at 250 ℃ have been successfully grown by atomic layer deposition (ALD) using $Al(CH_{3})_{3}$ [trimethylaluminum: TMA] and $C_{3}H_{8}O$ [isopropylalcohol: IPA]. TMA is a conventional Al precursor but IPA isn''t conventional O precursor. Even though $H_{2}O$ is a conventional oxygen precursor to deposit $Al_{2}O_{3}$ using ALD, in this thesis, IPA was used to oxygen precursor. The main reason of IPA selection will be discussed in later. The film growth kinetics were studied using the concept of ALD and also excellent film characteristics were confirmed. The ALD temperature range for $Al_{2}O_{3}$ using TMA and IPA was between 230 ℃ ∼ 290 ℃. In order to acquire the best ALD condition for Al_(2)O_(3) deposition using TMA and IPA at 250 ℃, $P_{TMA}$=0.01 torr, $P_{IPA}$=0.1 torr, the behaviors of deposition thickness/cycle with TMA pulse time and deposition thickness/cycle with IPA pulse time have been investigated. The set of minimum pulse times to get the fully saturated deposition thickness/cycle was (TMA pulse =2s,IPA pulse = 1s) and also, at the optimal condition, the fully saturated deposition thickness/cycle was around 0.8 Å/cycle, which corresponds to 0.37 ML (monolayer)/cycle. Also, refractive index of $Al_{2}O_{3}$ films has 1.61 ∼ 1.62. The refractive index of $Al_{2}O_{3}$ films were affected by IPA pulse time but not affected by TMA pulse time. Also, an ideal linear relationship between the number of cycles and the film thickness was confirmed. The compositions of deposited films were investigated by x-ray photoelectron spectroscopy (XPS) and also, the carbon incorporations into the films were analyzed by secondary ion mass spectroscopy (SIMS). The results of these studies shows almost stoichiometric $Al_{2}O_{3}$ films with slightly oxygen rich phase $(Al_{2}O_{3.1})$ and also there were no carbon incorporations into the films, i.e. SIMS results showed the detection limits values. Structure of Al_(2)O_(3) films were studied by x-ray diffraction (XRD) method. The results showed us that all films have amorphous structure regardless of annealing treatments. Surface morphology was also investigated by atomic force microscopy (AFM). Surface morphology of ALD $Al_{2}O_{3}$ films was as smooth as RMS roughness values of a few Å regardless of annealing treatments. These smooth surface of $Al_{2}O_{3}$ films indicated that the ALD process is the best choice to deposit ultra-thin layer with smooth surface. The analysis of interfacial regions of Al_(2)O_(3)/Si was studied by XPS and transmission electron microscopy (TEM). For the as-deposited $Al_{2}O_{3}$ film, there was no parasitic $SiO_{2}$ at the interfacial regions of $Al_{2}O_{3}$/Si even though there were parasitic $SiO_{2}$ at the interfacial regions of $Al_{2}O_{3}$/Si for the cases of the annealed $Al_{2}O_{3}$ films. The electrical properties of Al_(2)O_(3) films were investigated by I-V, C-V measurements. The leakage current values of Al_(2)O_(3) films were as low as $10^{-8} A/cm^{2}$. This low leakage value is desirable for sub-0.2 ㎛ design rule applications. Also, the dielectric constants of Al_(2)O_(3) films were as high as 9.66, 10.29 for the O2-annealed and the Ar-annealed Al_(2)O_(3) films, respectively. These high dielectric constant values correspond to the equivalent oxide thicknesses of 31.9 Å and 29.9 Å, for 80 Å-thick films, respectively. In general, since the equivalent oxide thickness required in sub-0.2 ㎛ design rule applications is about 26 Å, if Al_(2)O_(3) film with thickness less than 70 Å is fabricated, $Al_2O_3$ film will be adopted in sub-0.2 ㎛ design rule applications. Al_(2)O_(3) film prepared by ALD using TMA and IPA gave us possibility to use Al_(2)O_(3) film as a dielectric material for sub-0.2 ㎛ design rule applications.
Al_(2)O_(3) is considered as the most promising alternative to SiO_(2) for a gate dielectric materials in future Si-based integrated circuits owing to its high dielectric constant and low leakage current. In this study, amorphous Al_(2)O_(3) films on p-Si(100) at 250 ℃ have been successfully grown by atomic layer deposition (ALD) using $Al(CH_{3})_{3}$ [trimethylaluminum: TMA] and $C_{3}H_{8}O$ [isopropylalcohol: IPA]. TMA is a conventional Al precursor but IPA isn''t conventional O precursor. Even though $H_{2}O$ is a conventional oxygen precursor to deposit $Al_{2}O_{3}$ using ALD, in this thesis, IPA was used to oxygen precursor. The main reason of IPA selection will be discussed in later. The film growth kinetics were studied using the concept of ALD and also excellent film characteristics were confirmed. The ALD temperature range for $Al_{2}O_{3}$ using TMA and IPA was between 230 ℃ ∼ 290 ℃. In order to acquire the best ALD condition for Al_(2)O_(3) deposition using TMA and IPA at 250 ℃, $P_{TMA}$=0.01 torr, $P_{IPA}$=0.1 torr, the behaviors of deposition thickness/cycle with TMA pulse time and deposition thickness/cycle with IPA pulse time have been investigated. The set of minimum pulse times to get the fully saturated deposition thickness/cycle was (TMA pulse =2s,IPA pulse = 1s) and also, at the optimal condition, the fully saturated deposition thickness/cycle was around 0.8 Å/cycle, which corresponds to 0.37 ML (monolayer)/cycle. Also, refractive index of $Al_{2}O_{3}$ films has 1.61 ∼ 1.62. The refractive index of $Al_{2}O_{3}$ films were affected by IPA pulse time but not affected by TMA pulse time. Also, an ideal linear relationship between the number of cycles and the film thickness was confirmed. The compositions of deposited films were investigated by x-ray photoelectron spectroscopy (XPS) and also, the carbon incorporations into the films were analyzed by secondary ion mass spectroscopy (SIMS). The results of these studies shows almost stoichiometric $Al_{2}O_{3}$ films with slightly oxygen rich phase $(Al_{2}O_{3.1})$ and also there were no carbon incorporations into the films, i.e. SIMS results showed the detection limits values. Structure of Al_(2)O_(3) films were studied by x-ray diffraction (XRD) method. The results showed us that all films have amorphous structure regardless of annealing treatments. Surface morphology was also investigated by atomic force microscopy (AFM). Surface morphology of ALD $Al_{2}O_{3}$ films was as smooth as RMS roughness values of a few Å regardless of annealing treatments. These smooth surface of $Al_{2}O_{3}$ films indicated that the ALD process is the best choice to deposit ultra-thin layer with smooth surface. The analysis of interfacial regions of Al_(2)O_(3)/Si was studied by XPS and transmission electron microscopy (TEM). For the as-deposited $Al_{2}O_{3}$ film, there was no parasitic $SiO_{2}$ at the interfacial regions of $Al_{2}O_{3}$/Si even though there were parasitic $SiO_{2}$ at the interfacial regions of $Al_{2}O_{3}$/Si for the cases of the annealed $Al_{2}O_{3}$ films. The electrical properties of Al_(2)O_(3) films were investigated by I-V, C-V measurements. The leakage current values of Al_(2)O_(3) films were as low as $10^{-8} A/cm^{2}$. This low leakage value is desirable for sub-0.2 ㎛ design rule applications. Also, the dielectric constants of Al_(2)O_(3) films were as high as 9.66, 10.29 for the O2-annealed and the Ar-annealed Al_(2)O_(3) films, respectively. These high dielectric constant values correspond to the equivalent oxide thicknesses of 31.9 Å and 29.9 Å, for 80 Å-thick films, respectively. In general, since the equivalent oxide thickness required in sub-0.2 ㎛ design rule applications is about 26 Å, if Al_(2)O_(3) film with thickness less than 70 Å is fabricated, $Al_2O_3$ film will be adopted in sub-0.2 ㎛ design rule applications. Al_(2)O_(3) film prepared by ALD using TMA and IPA gave us possibility to use Al_(2)O_(3) film as a dielectric material for sub-0.2 ㎛ design rule applications.
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