空间隔离原子层沉积系统的研究

原子层沉积(ALD)技术制备的薄膜在纳米尺度精确可控,并且各处薄膜厚度具有良好的均匀性。空间隔离原子层沉积(SALD)相比于时间隔离ALD技术,此工艺更易实现大面积基底沉积和连续沉积。由于SALD技术巨大的应用前景,关于SALD技术的研究成为ALD技术研究的热点之一。本文介绍了实验室自主设计搭建的SALD系统平台,以Al2O3生长评估SALD系统,实现Al2O3薄膜线性生长。并对反应温度、基底与前驱体喷头间距这两个重要的工艺参数进行了研究。SALD沉积实验表明,减小基底表面温度波动可以提高薄膜的微观形貌质量。同时,前驱体进气喷头与基底之间的距离会强烈影响基底表面的前驱体压力和前驱体间隔离效果,进而影响薄膜生长。为平衡薄膜生长均匀性和系统密封性的要求,需要选择最优的间距值。     

柔性基体表面原子层沉积Al_2O_3薄膜研究进展

随着机械、光学、微电子和纳米科技等领域的发展,在柔性基体上如聚酯(PET)、聚乳酸酯(PLA)、聚酰亚胺(PI)等聚合物表面沉积Al_2O_3薄膜作为阻挡层、介电层、钝化层的研究也越来越多。无机Al_2O_3薄膜因其机械强度与硬度高、光学性能优良、透明性高与绝缘性好、耐磨、抗蚀及化学惰性等特点引起人们的极大兴趣。较传统薄膜制备技术,原子层沉积(ALD)技术制备的薄膜具有精确的厚度和成分可控性、高度均匀性和保形性,成为制备Al_2O_3薄膜的主要方式之一。本综述首先概述了原子层沉积原理,其次阐述了柔性沉积基体的特点,介绍了Al_2O_3薄膜的生长过程和影响因素,比较了在柔性基体上热原子层沉积和等离子体辅助原子层沉积Al_2O_3薄膜的优缺点,最后总结和展望了ALD制备Al_2O_3薄膜的研究趋势和应用前景。     

基于原子层沉积技术制备氧化钽薄膜及其特性研究

本工作以单晶硅为衬底,乙醇钽和水分别为钽源和氧源,研究原子层沉积技术制备氧化钽薄膜的工艺,考察了乙醇钽温度、衬底温度、脉冲时间等工艺条件对氧化钽薄膜的生长速率、粗糙度和表面形貌等特性的影响.通过椭偏仪、原子力显微镜、扫描电子显微镜以及高分辨X射线光电子能谱测试分析表明,制备获得的氧化钽薄膜表面光滑,粗糙度小于1 nm,薄膜生长速率受工艺参数的影响较大,其中在乙醇钽源瓶温度170℃、脉冲时间0.1 s以及衬底温度200℃时,氧化钽的生长速率为0.253?/cycle.本工作基于原子层沉积高性能氧化钽薄膜的工艺研究,将对氧化钽薄膜在介质材料、存储介质以及光学涂层等领域的应用奠定基础.     

不同温度对原子层沉积掺铝氧化锌薄膜性能的影响

采用热原子层沉积(ALD)方法,在固定氧化锌与氧化铝沉积比例的情况下,研究了不同温度下在玻璃衬底上沉积的掺铝氧化锌薄膜性能的变化,特别是"ALD窗口"温度的影响。通过计算薄膜沉积速率,得到了薄膜沉积的"ALD窗口"温度范围为225~275℃,相应的沉积速率为0.214 nm/cycle。分析样品的表面形貌后发现,虽然反应的温度有所不同,但薄膜的微观结构均为密集堆积的纺缍体,它们的尺寸受到温度、晶体结构等因素的影响。结构分析表明,在"ALD窗口"温度范围内,所有沉积得到的样品均为(100)择优取向,并且结晶质量、晶粒尺寸以及(002)峰的相对强度均随着温度升高而增大。薄膜的光学透过率以及光学带隙没有随温度变化而表现出明显的变化,分别在80%(350~770 nm)和3.90 e V左右。薄膜的电导率和光学质量在"ALD窗口"内随温度增加而增长,直到300℃时达到最佳。     

原子层沉积技术及其在光学薄膜中的应用

回顾了原子层沉积(ALD)技术的发展背景,通过分析ALD的基本工艺,并与传统薄膜制备工艺进行了对比研究.介绍了它在膜层的均匀性、保形性以及膜厚控制能力等方面的优势.着重列举ALD在减反膜、紫外截止膜、折射率可调的薄膜、抗激光损伤薄膜及复杂结构光子晶体等方面的应用.同时指出了目前ALD工艺在光学薄膜应用中存在的主要问题,并对ALD未来的发展进行了展望.     

沉积速率对ZnO薄膜生长过程和微结构影响的分子反应力场方法研究

应用基于反应力场的分子动力学方法研究了ZnO薄膜(001)表面作为衬底的薄膜沉积生长过程,初步讨论了500K时,沉积速率(1.5、2.5和3.5m/s)变化对沉积薄膜质量的影响。结果表明沉积速率约3.5m/s时,衬底结构最稳定,沉积原子结构径向分布函数曲线特征峰尖锐、明显,有序度较高;每原子层密度分析表明优化的沉积温度和沉积速率下,沉积形成的薄膜结构稳定而又致密。在预置衬底表面平坦的情况下薄膜呈现一种岛状的生长模式,近衬底区Zn—O键呈现理想的生长取向,而近表面区则两种生长取向共存,导致其生长前锋交汇处形成新的有序缺陷及氧空位。     

Cu薄膜三维生长的Monte Carlo模拟

利用蒙特卡罗(Monte Carlo)方法模拟了Cu薄膜在四方基底上的三维生长过程。模型中考虑了三个主要的原子热运动过程:原子沉积、原子扩散、原子脱附,各过程发生的概率是由各运动的速率来决定的。讨论了基底温度、沉积速率及原子覆盖度对Cu薄膜的表面形貌及表面粗糙度的影响。模拟结果表明:随基底温度升高或沉积速率下降,岛的平均尺寸增大,数目减少,薄膜以层状生长方式生长;Cu薄膜表面粗糙度随温度的升高而减小,当基底温度处于某一临界温度之内时,表面粗糙度随沉积速率的变化很大,但当基底温度超过临界温度时,表面粗糙度随沉积速率的变化很小;薄膜的粗糙度与薄膜亚单层的形核密切相关。     

基于响应面法的原子层沉积高阻隔膜研究

目的 研究分析等离子辅助原子层沉积技术(ALD)技术在PET表面上沉积超薄Al2O3阻隔层的工艺优化。方法 采用单因素结合响应面设计试验法,对Al2O3/PET薄膜的沉积速率(GPC)进行优化,通过AFM分析得到薄膜的生长模式和表面粗糙度,最后用水蒸气透过率表征薄膜的阻隔性能。结果 最大GPC的沉积参数:TMA脉冲时间为0.17 s、吹扫时间为11 s、O2的脉冲时间为0.35 s、吹扫时间为10 s、沉积速率为0.215 nm/cycle;薄膜以层状生长模式生长,表面粗糙度均方根(RMS)为0.58 nm;沉积500个循环后薄膜的水透过率从7.456 g∙d/m²降低到0.319 g∙d/m²。结论 通过响应面法优化了ALD制备工艺参数,Al2O3在PET表面沉积100 nm左右时,水蒸气阻隔性提高了25倍。     

多孔基底原子层沉积薄膜分布的数值模拟北大核心CSCD

原子层沉积(ALD)技术能在多孔基底内沉积亚纳米精度的薄膜,从而调节孔道尺寸和界面性质。此类ALD薄膜沉积,同时受到前驱体扩散和反应的影响,这给沉积动力学研究带来了困难。本文对ALD制备ZnO薄膜过程中前驱体在γ-Al_(2)O_(3)基底外表面沉积和孔道内沉积过程建立了模型,并通过数值模拟对表面和孔道两种模型进行了参数敏感性分析,拟合得到沉积物覆盖率公式。结果表明:在表面沉积过程中,随着吸附速率常数ka、吸附态的二乙基锌(DEZ*)向单乙基锌(MEZ)转化速率常数k1、羟基浓度COH的增大,和脱附速率常数kd的减小,基底表面的薄膜沉积加快;对于孔道内沉积过程,较大的羟基浓度COH和较小的扩散系数DS,驱使薄膜沉积在较浅位置;拟合所得解析式能准确预测多孔基底外表面和孔道内的沉积物覆盖率及其分布。     

原子层沉积技术及应用发展概况

首先回顾了原子层沉积(ALD)发展历史,介绍了ALD的基本工艺和ALD薄膜具有的优良特性,并与传统的薄膜制备工艺进行了对比研究.重点阐述了ALD在微电子技术、微电子机械系统以及光学工程中的几个应用研究现状.分析了ALD目前存在的问题,并对ALD未来的发展进行了展望.     

Electrical resistivity of Ti-Zn mixed oxide thin films deposited by atomic layer deposition

Ti-Zn mixed oxide thin films, with thickness less than 50 nm, were grown with atomic layer deposition (ALD) technique at low temperature (90 °C) varying the composition. ALD is a powerful chemical technique to deposit thin films with thickness of few atomic layers. ALD oxide material growth is achieved by dosing sequentially the metal precursor and the oxidizing agent. Thanks to ALD nature of layer by layer growth it was possible to realize mixed metal, Ti and Zn, oxide thin films with controlled composition, simply by changing the number of cycles of each metal oxide layer. Structural and electrical properties of the prepared thin films were studied as a function of their composition. Synchrotron radiation X-ray diffraction technique was used to follow thin film crystallization during sample annealing, performed in situ. It was observed that the onset temperature of crystallization raises with Ti content, and sample structure was Zn₂TiO4 phase. Electrical resistivity measurements were performed on crystalline samples, annealed at 600 °C, revealing an increase in resistivity with Ti content.     

In-situ synchrotron X-ray scattering study of thin film growth by atomic layer deposition

We report an atomic layer deposition chamber for in-situ synchrotron X-ray scattering study of thin film growth. The chamber was designed for combined synchrotron X-ray reflectivity and two-dimensional grazing-incidence X-ray diffraction measurement to do a in-situ monitoring of ALD growth. We demonstrate ruthenium thermal ALD growth for the performance of the chamber. 10, 20, 30, 50, 70, 100, 150 and 250-cycled states are measured by X-ray scattering methods during ALD growth process. Growth rate is calculated from thickness values and the surface roughness of each state is estimated by X-ray reflectivity analysis. The crystal structure of initial growth state is observed by Grazing-incidence X-ray diffraction. These results indicate that in-situ X-ray scattering method is a promising analysis technique to investigate the initial physical morphology of ALD films.     

Atomic layer deposition of nanocrystallite arrays of copper(I) chloride for optoelectronic structures

Zinc blende structure γ-copper(I) chloride is a wide bandgap semiconductor with high exciton and biexciton binding energies. γ-CuCl has applications in UV-wavelength optoelectronic structures which can exploit these characteristics, such as 4-wave mixing and optical bistability. For these purposes, a controllable method of achieving thin films and nanocrystallite arrays is necessary. Atomic layer deposition (ALD) of nanocrystallites and thin films of γ-CuCl under restricted conditions has previously been demonstrated. This paper greatly extends the previous work and unequivocally confirms that ALD growth takes place over a range of deposition parameters, as characterised by growth saturation with increasing precursor dose, deposition rate independent of temperature and linear growth rate once a complete film has been formed. Arrays of nanocrystallites of different sizes can be controllably deposited by varying the number of ALD cycles within the initial nucleation region. In this region two distinct growth regimes have been observed depending on the length of the post-chloride precursor purge pulse. Long purge time results in retarded nucleation whereas short pulse time shows enhanced nucleation compared to a strictly linear process. The zinc blende γ-CuCl phase was confirmed with both X-ray analysis and also the signature excitonic Z_1,2 and Z₃ peaks in optical absorption, with no evidence of other impurities. This demonstrates that ALD is a suitable technique for the controllable deposition of thin films and arrays of nanocrystallites of CuCl which may facilitate the use of CuCl in thin film or nanocluster form for further exploration in optoelectronic and photonic applications.     

In-situ inspection of cracking in atomic-layer-deposited barrier films on surface and in buried structures

Thin inorganic barrier films deposited on plastics are essential to provide protection from moisture- and oxygen-aided degradation while maintaining a flexible substrate. Mechanical bending of the barrier films, causes stress-induced cracks that may lead to significant reduction or loss of barrier protection. In-situ characterization of film cracking on the nanoscale, transparent, and conformal atomic-layer-deposited (ALD) thin films is challenging especially when these films are in a buried layer structure. We developed a technique that can inspect in real-time the cracking of the stressed barrier films using laser scanning confocal microscopy. The in-situ inspection avoids the inaccurate measurement of the crack onset strain associated with the crack “close-up” phenomenon. SU8 cover-coat is applied to form a buried ALD layer structure and in-situ inspection demonstrates the cracking of the ALD film in real-time underneath the cover-coat. This technique is nondestructive, versatile, and allows rapid and large-area inspection of different types of barrier films.     

Simulation of growth dynamics in atomic layer deposition. Part II. Polycrystalline films from cubic crystallites

The growth dynamics of polycrystalline thin films by the atomic layer deposition (ALD) technique has been simulated for randomly oriented and randomly positioned seed objects. Cubic crystals with the shape of cubes, octahedra, and truncated cubes have been used to exemplify the dynamics of polycrystalline growth of films with columnar structures. We have reproduced the non-linear growth in the initial stages of ALD preparation of polycrystalline films according to type-2 substrate-inhibited growth. The dependences of topography roughness, surface object density, and selection of angles on terminating surfaces on the film thickness are demonstrated. The topography and cross sections of the simulated films are also shown for the different crystal shapes considered. Means to control the topography to obtain either smooth or rough films are discussed. A possible reduction of surface roughness by the use of different types of precursors is exemplified for growth of crystal objects combining cube and octahedron shapes.     

原子层淀积制备金属氧化物薄膜研究进展

原子层淀积(ALD)技术作为一种先进的薄膜制备方法近年来越来越得到重视,它能精确地控制薄膜的厚度和组分,实现原子层级的生长,生长的薄膜具有很好的均匀性和保形性,因而在微电子和光电子等领域有广泛的应用前景。本文综述了ALD技术的基本原理,及其在金属氧化物薄膜制备上的研究进展。     

柔性高阻隔薄膜材料的研究现状

目的为柔性高阻隔薄膜的应用提供理论指导。方法综述柔性高阻隔膜的应用现状及存在问题,总结热蒸发、化学气相沉积、原子层沉积等制备柔性高阻隔薄膜的方法、原理、特点及应用,展望高阻隔膜包装材料的发展前景。结果高阻隔薄膜制备工艺趋向于单次制备,采用等离子体辅助原子层沉积技术是制备超高阻隔薄膜的首选,原子层沉积(ALD)和分子层沉积(MLD)结合也是获得超高阻隔薄膜的未来发展方向。结论快速、高效地制备柔性高阻隔薄膜是包装工业的发展趋势。     

Thin film atomic layer deposition equipment for semiconductor processing

Atomic layer deposition (ALD) of ultrathin high-K dielectric films has recently penetrated research and development lines of several major memory and logic manufacturers due to the promise of unprecedented control of thickness, uniformity, quality and material properties. LYNX-ALD technology from Genus, currently at beta phase, was designed around the anticipation that future ultrathin materials are likely to be binary, ternary or quaternary alloys or nanolaminate composites. A unique chemical delivery system enables synergy between traditional, production-proven low pressure chemical vapor deposition (LPCVD) technology and atomic layer deposition (ALD) controlled by sequential surface reactions. Source chemicals from gas, liquid or solid precursors are delivered to impinge on reactive surfaces where self-limiting surface reactions yield film growth with layer-by-layer control. Surfaces are made reactive by the self-limiting reactions, by surface species manipulation, or both. The substrate is exposed to one reactant at a time to suppress possible chemical vapor deposition (CVD) contribution to the film. Precisely controlled composite materials with multiple-component dielectric and metal–nitride films can be deposited by ALD techniques. The research community has demonstrated these capabilities during the past decade. Accordingly, ALD equipment for semiconductor processing is unanimously in high demand. However, mainstream device manufacturers still criticize ALD to be non-viable for Semiconductor device processing. This article presents a broad set of data proving feasibility of ALD technology for semiconductor device processing.     

ZnO thin films prepared by atomic layer deposition and rf sputtering as an active layer for thin film transistor

Recently, the application of ZnO thin films as an active channel layer of transparent thin film transistor (TFT) has become of great interest. In this study, we deposited ZnO thin films by atomic layer deposition (ALD) from diethyl Zn (DEZ) as a metal precursor and water as a reactant at growth temperatures between 100 and 250 °C. At typical growth conditions, pure ZnO thin films were obtained without any detectable carbon contamination. For comparison of key film properties including microstructure and chemical and electrical properties, ZnO films were also prepared by rf sputtering at room temperature. The microstructure analyses by X-ray diffraction have shown that both of the ALD and sputtered ZnO thin films have (002) preferred orientation. At low growth temperature T_s ≤ 125 °C, ALD ZnO films have high resistivity (> 10 Ω cm) with small mobility (< 3 cm²/V s), while the ones prepared at higher temperature have lower resistivity (< 0.02 Ω cm) with higher mobility (> 15 cm²/V s). Meanwhile, sputtered ZnO films have much higher resistivity than ALD ZnO at most of the growth conditions studied. Based upon the experimental results, the electrical properties of ZnO thin films depending on the growth conditions for application as an active channel layer of TFT were discussed focusing on the comparisons between ALD and sputtering.     

Surface chemistry and film growth during TiN atomic layer deposition using TDMAT and NH3

Surface chemistry and film growth were examined during titanium nitride (TiN) atomic layer deposition (ALD) using sequential exposures of tetrakis-dimethylamino titanium (TDMAT) and NH₃. This ALD system is shown to be far from ideal and illustrates many potential problems that may affect ALD processing. These studies were performed using in situ Fourier transform infrared (FTIR) techniques and quartz crystal microbalance (QCM) measurements. Ex situ measurements also analyzed the properties of the TiN ALD films. The FTIR studies revealed that TDMAT reacts with NH_x* species on the TiN surface following NH₃ exposures to deposit new Ti(N(CH₃)₂)_x* species. Subsequent NH₃ exposure consumes the dimethylamino species and regenerates the NH_x* species. These observations are consistent with transamination exchange reactions during the TDMAT and NH₃ exposures. QCM studies determined that the TDMAT and NH₃ reactions are nearly self-limiting. However, slow continual growth occurs with long TDMAT exposures. In addition, the TiN ALD growth rate increases progressively with growth temperature. The resistivities of the TiN ALD films were ?10⁴ μΩ cm and the densities were ?3 g/cm³ corresponding to a porosity of ∼40%. The high porosity allows facile oxidation of the TiN films and lowers the film resistivities. These high film porosities will seriously impair the use of these TiN ALD films as diffusion barriers.