薄膜物理与技术复习课.pdf

1、真空相关真空是指低于一个大气压的气体空间。常用“真空度”度量。真空 度越高，压强越小。 “vacuum” = lower molecular density than in our atmosphere results in a lower pressure of gas.The vacuum degree is higher, the higher the vacuum degree, the smaller the pressure.常用计量单位：Pa, Torr, mmHg, bar, atm.。关系如下： 1mmHg=133.322Pa,1 Torr=atm/760=133.322Pa

2、1mmHg 1 bar=105Pa最可几度平均速度均方根速度vm =2kT=2RT= 1.41RTMmMva =8kT=8RT= 1.59RTpmpMMvr =3kT=3RT= 1.73RTmMM平均自由程：每个分子在连续两次碰撞之间的路程称为自由程；其统 计平均值成为平均自由程。Mean free path: the distance between each molecule in a continuous two collision is called a free path, and the average value of the system is a mean free path

3、.l =kTps 2 P2 根据气体分子运动论，在气体压力为P时，单位时间内碰撞单位面积器 壁上的分子数量，即碰撞分子流量（通量或蒸发速率）。According to kinetic theory of gases, the gas pressure when P, the number of molecular collisions per unit time per unit area of the wall, ie, molecular collision flow (flux or evaporation rate). 平均自由程与分子密度n和分子直径的平方成反比关系，平均自由 程与压

4、强成反比，与温度成正比。The mean free path of molecules and molecular density n and is inversely proportional to the square of the diameter, and the pressure is inversely proportional to the mean free path is proportional to temperature.为什么用薄膜？Why thin films? （1）薄膜所用原料少，容易大面积化，而且可以曲面加工。(研究和使用成 本) 例：金箔、饰品、太阳能电池，

5、GaN，SiC，Diamond；Materials used less film, easily large area, and can be surface processing. (Research and cost) Example: gold, jewelry, solar, GaN, SiC, Diamond （2）新的效应: 某一维度很小、比表面积大. 例：限域效应、表面和界面效 应、耦合效应，隧穿效应、极化效应；新的效应: 某一维度很小、比表面积大. 例：限域效应、表面和界面效 应、耦合效应，隧穿效应、极化效应； New effects: for a dimension is s

6、mall, than a large surface area. For example: confinement effect, surface and interface effect of, coupling effect, tunneling effect, polarization effect;（3） 可以获得体态下不存在的非平衡和非化学计量比结构；Can be obtained under the condition of the non balance and non stoichiometry structure;（4）容易实现多层膜,相互作用与功能集成Easy to imp

7、lement multi-layered film, interaction and functional integration真空区域的划分classification of vacuum 大气Atmospheric: 760 Torr 粗真空Rough Vacuum: 1 to 1x10-3 Torr 低真空Low Vacuum: 1x10-3 to 1x10-5 Torr 高真空High Vacuum (HV): 1x10-6 to 1x10-8 Torr 超高真空Ultra-High Vacuum (UHV): < 1x10-9 Torr真空计 Vacuum gauge （1）

8、绝对真空计：U型真空计、压缩式真空计Absolute vacuum gauge: U-type vacuum gauge, compression-type vacuum gauge （2）相对真空计：放电真空计、热传导真空计、电离真空计The relative vacuum gauge: discharge vacuum gauges, heat conduction vacuum gauges, ionization vacuum gauge各种真空泵 Vacuum pump （1）旋转式机械真空泵、油扩散泵、复合分子泵，属于气体传输 泵，即通过气体吸入并排出真空泵从而达到排气的目的。A

9、rotary mechanical vacuum pump, an oil diffusion pump, a composite molecular pump, the gas transfer pump belongs, and is discharged through a gas suction pump so as to achieve the purpose of the exhaust gas. （2）分子筛吸附泵、钛升华泵、溅射离子泵、低温泵，属于气体 捕获泵，即通过各种吸气材料特有的吸气作用将被抽气体吸 除，以达到所需真空。不需要油作为介质，又称为无油泵。Molecular

10、sieve adsorption pump, titanium sublimation pump, sputter ion pump, cryopump, below the gas-trapping pump, i.e. the gas will be pumped through a variety of getter material suction specific gettering effect, to achieve the desired vacuum. You do not need oil as a medium, also known as free pump.机械泵的工

11、作原理Working principle of mechanical pump 利用机械力压缩和排除气体Using mechanical force of the compression and exhaust gas旋片式机械泵的工作原理Working principle of rotary vane pump 依靠放置在偏心转子中可以旋转的旋片将气体隔离、压缩，然后排出泵体外Rely placed in the eccentric rotor can rotate the rotary vane isolate the gas, compressed, and then discharge

12、 pump body扩散泵的工作原理Working principle of diffusion pump 靠蒸汽喷射的动量把气体带走The gas is taken away by steam injection. 利用被抽气体向蒸汽流扩散的现象实现排气，在扩散泵中没有转动或压缩部件The exhaust gas is realized by pumping gas to the steam flow, and there is no rotating or compression part in the diffusion pump.分子泵的工作原理 Working principle o

13、f molecular pump 涡轮分子泵的工作原理Working principle of the turbo molecular pump 靠对气体分子施加作用力，并使气体分子向特定的方向运动By applying force to the gas molecules and the gas molecules motion in a specific direction Molecules mechanically pumped by collision with angled high speed turbine blades (rotor).真空计的工作原理 Working pri

14、nciple of vacuum gauge 真空激发沉积Vacuum excitation deposition两个关键： （1）真空度：P<=10(-3)pa(保证粒子具有分子流特征，以直线运动）Vacuum degree: P<=10 (-3) pa (which can ensure that the particles have molecular flow characteristics, in order to move in a straight line). 真空室压力过高，会出现以下情况：（a）粒子频繁碰撞，难以得到均匀的薄膜；（b）污染薄膜（会轰击基片并吸附）

15、；（c）蒸发形成的均源被氧化The vacuum chamber pressure is too high, the following occurs: (a) particles collide frequently difficult to obtain a uniform film; (b) pollution film (will bombard the substrate and adsorption); (c) Evaporation of the formation of the source is oxidized （2）蒸发距离（相对于蒸发源）：1050cm能使用情况：蒸发时

16、不发生化学反应。沉积物中杂质的含量与残余气体的压强成正比，与沉积的速度成反比。(2) from the evaporator (relative to the evaporation source): 10-50cmIt can be used: do not chemically react upon evaporation.Sediments content of impurities and residual gas pressure is proportional with the deposition rate is inversely proportional.点蒸发源和小平面蒸发

17、源特性The characteristics of the origin and the small plane evaporation source of the point见课件什么是同质外延、异质外延 （1）同质外延：生长外延层和衬底是同一种材料。典型的例子：硅/硅，砷化镓/砷化镓或n-GaAs/p-GaAs等Homoeptiaxy: the composition of the grown layer is essentially the same as that of the underlying substrate. Typical examples: Si/Si, GaAs/Ga

18、As or n-GaAs/p-GaAs, etc. （2）异质外延：生长外延层不同于衬底。典型的例子：AlGaAs/GaAs, InGaAsP/InP, GaN/sapphire,等Heteroeptiaxy: the composition of the layer differs from that of the substrate. Typical examples: AlGaAs/GaAs, InGaAsP/InP, GaN/sapphire, etc.什么是失配度 晶格失配：当在某种单晶衬底上生长另一种物质的单晶层时,由于这两种物质的晶格常数不同,会在生长界面附近产生应力,进而产生晶

19、体缺陷失配位错.通常把这种由于衬底和外延层的晶格常数不同而产生的失配现象叫晶格失配。 Lattice mismatch: when grown single crystal layer of another substance in some single crystal substrate, because the grain of these two substancesDifferent lattice constants, can cause stress in the vicinity of the growth interface, and produce crystal defe

20、cts - misfit dislocations usuallyThis phenomenon is due to the mismatch in lattice constant different substrates and epitaxial layers produced called lattice mismatch. 失配度Thermal accommodation coefficientthe effusion cell temperature Ti,substrate surface temperature Ts, usually lower than Ti, reevap

21、orate temperature Te.The impinging atoms may exchange energy with the atoms of the substrate until they are in thermodynamic equilibrium at Ts.Clearly, when Te is equal to Ts the accommodation coefficient is unity. Thus, it emerges as a measure of theextent to which the arriving atoms reach thermal

22、equilibrium with the substrate.真空蒸发沉积Vacuum evaporation deposition（1） 电阻式蒸发装置：电阻热Resistive evaporation plant:Thermal resistance(2) 电子束蒸发装置：电子束轰击Electron beam evaporation device:Electron beam bombardment(3) 电弧激发装置：电弧Arc excitation device:arc(4) 激光蒸发装置：激光Laser evaporation device: laser分子束外延（MBE）的特点？（M

23、olecular beam epitaxy (MBE) features） （1）外延: 在一定的单晶材料衬底上，沿衬底某个指数晶面向外延伸生长一层单晶 薄膜。Extension: In a certain monocrystalline material substrate, the extension of an index crystal substrate extending outwardly growing a single crystal thin film. （2）MBE可以严格控制薄膜生长过程和生长速率。MBE虽然也是以气体分子论为基础 的蒸发过程，但它并不以蒸发温度为控制参

24、数，而是以四极质谱、原子吸收光谱等 近代分析仪器，精密控制分子束的种类和强度。MBE can strictly control the growth process and the growth rate films. Although MBE evaporation process is also based on the basis of the gas molecules, but it is not to evaporate the temperature control parameters, but in modern times of the instruments quadru

25、pole mass spectrometry, atomic absorption spectroscopy, the type and intensity of precise control of the molecular beam. （3）MBE是一个超高真空的物理淀积过程，即不需要中间化学反应，又不受质量输运 的影响，利用快门可对生长和中断进行瞬时控制。薄膜组成和掺杂浓度可以随源的 变化作迅速调整。MBE is a high vacuum deposition process, which is not required for intermediate chemical react

26、ion, and is not affected by mass transport, the use of shutter can be used to control the growth and interruption of the film. （4）MBE的衬底温度低，降低了界面上热膨胀引入的晶格失配效应和衬底杂质对外延 层自掺杂扩散的影响。The substrate temperature is low, and the effect of the lattice mismatch effect and the substrate impurities on the self -

27、doping diffusion of the epitaxial layer is reduced by the thermal expansion of the interface. （5）MBE是一个动力学过程，即将入射的中性粒子（原子或分子）一个一个地堆积在 衬底上进行生长，而不是一个热力学过程，所以它可以生长普通热平衡生长难以生 长的薄膜。MBE is a dynamic process that is about to be carried out by the incoming neutral particles (atoms or molecules) that are gro

28、wn on a substrate rather than a thermodynamic process, so that it can grow ordinary heat balance to grow hard to grow thin films. （6）MBE生长速率低，相当于每秒生长一个单原子层，有利于精确控制薄膜厚度、结 构和成分，形成陡峭的异质结结构。特别适合生长超晶格材料。MBE生长速率低，相当于每秒生长一个单原子层，有利于精确控制薄膜厚度、结 构和成分，形成陡峭的异质结结构。特别适合生长超晶格材料。 The growth rate of MBE is low, which

29、 is equivalent to the growth of a single atomic layer per second, which is conducive to the precise control of film thickness, structure and composition, and the formation of steep heterojunction structures, especially for the growth of superlattice materials. （7）MBE在超高真空下进行，可以利用多种表面分析仪器实时进行成分、结构及生长

30、 过程分析，进行科学研究。MBE is carried out in the ultra high vacuum, and can be used to analyze the composition, structure and growth process of a variety of surface analysis instruments.溅射镀膜与真空镀膜相比，有何特点？Compared with the sputtering vacuum coating, What are the characteristics?（1）任何物质都可以溅射，尤其是高熔点金属、低蒸气 压元素和化合物

31、；Any material can be sputtering, especially high melting point metal, low vapor pressure elements and compounds;（2）溅射薄膜与衬底的附着性好；Sputtered film with good adhesion to the substrate;（3）溅射镀膜的密度高、针孔少，膜层纯度高；High density sputtering, less pinhole, high film purity;（4）膜层厚度可控性和重复性好。Film thickness controllabil

32、ity and repeatability（5）溅射设备复杂，需要高压装置；Sputtering equipment complex and require high voltage devices（6）mm）mm)溅射的概念及溅射参数The concept sputtering and sputtering parameters （1）溅射是指荷能粒子轰击固体表面（靶），使固体 原子或者分子从表面射出的现象. Sputtering is the phenomenon that the charged particle bombardment the solid surface (target

33、), so that the solid atoms or molecules from the surface of the phenomenon. (2)溅射参数i. 溅射阈值 Sputtering thresholdii.溅射率及其影响因素 Sputtering rate and its affecting factorsiii.溅射粒子的速度和能量分布 Velocity And energy distribution of sputtered particlesiv.溅射原子的角度分布溅射原子的角度分布 Angular distribution of sputtered atomsv.

34、 溅射率的计算 Calculation of sputtering yield溅射机理Sputtering mechanism 溅射现象是被电离气体的离子在电场中加速并轰击靶面， 而将能量传递给碰撞处的原子，导致很小的局部区域产生高 温，使靶材融化，发生热蒸发。Sputtering phenomenon is ionized gas ions are accelerated and bombard the target surface in the electric field, and the energy transfer to atomic collisions at lead a sm

35、all local area to produce high temperature, so target melt, thermal evaporation. 溅射完全是一个动量转移过程。 该理论认为，低能离子碰撞靶时，不能直接从表面溅射出原子，而是把动量传给被碰撞的原子，引起原子的级联碰撞。这种碰撞沿晶体点阵的各个方向进行。碰撞因在最紧密排列的方向上最有效，结果晶体表面的 原子从近邻原子得到越来越多的能量。当原子的能量大于结合能时，就从表面溅射出来。Sputtering is entirely a momentum transfer process. The theory is that

36、when low-energy ion collisions target, can not be directly sputtered atoms from the surface, but the momentum was passed atomic collisions, causing a cascade of atomic collisions. Such collisions along each direction of the crystal lattice. Collision because most closely aligned in the direction of

37、the most effective results atomic crystal surface more and more energy from neighboring atoms. When the energy is greater than the binding energy of atoms, it sputtered from the surface.溅射沉积法Sputter deposition放电条件Discharge condition： （1）真空环境 vacuum environment ：P=10(-1)-10(2)Pa （2）放电气体：需要冲入惰性气体（一般为氩

38、气）Discharge gas：Need to be rushed into the inert gas (usually argon) （3）外加电场：在其作用下，放电气体被电离，形成阳离子（Ar+）和自由电子（e），并分别在电场作用下被加速，进而飞向阴极（靶材）和阳极Electric field: in its action, the discharge gas is ionized, to form a cation (Ar +) and free electrons (e), and were accelerated in the electric field, and then fl

39、y to the cathode (target) and the anodeCVD热力学分析的主要目的The main purpose of thermodynamic analysis of CVD 预测某些特定条件下某些CVD反应的可行性（化学反 应的方向和限度）。The feasibility of predicting certain CVD responses under certain conditions (direction and limitation of chemical reactions).CVD热力学基本内容反应速率及其影响因素热分解反应、化学合成反应及化学输运反

40、应及其特点Thermal decomposition reaction, chemical synthesis and chemical transport reaction and its characteristics （1）热分解反应（吸热反应）：该方法在简单的单温区炉中，在真空或惰性 气体保护下加热基体至所需温度后，导入反应物气体使之发生热分解，最 后在基体上沉积出固体图层。Thermal decomposition reaction (endothermic reaction): after the process in a simple single-zone furnace, u

41、nder vacuum or inert gas for heating the substrate to the desired temperature, introducing the reactant gas so that thermal decomposition, and finally deposited on a substrate the solid layer. （2）化学合成反应:指两种或两种以上的气态反应物在热基片上发生的相互 反应。化学合成反应法比热分解法的应用范围更加广泛。可以制备单晶、 多晶和非晶薄膜。容易进行掺杂。Chemical synthesis react

42、ion: refers to the interaction of two or more than two kinds of gaseous reactants in Reji. Chemical synthesis reaction Fabiger decomposition method is used more widely. Can preparation of single crystal, polycrystalline and amorphous films. Doping. （3）化学输运反应: 将薄膜物质作为源物质（无挥发性物质），借助适当的 气体介质与之反应而形成气态化合

43、物，这种气态化合物经过化学迁移或物 理输运到与源区温度不同的沉积区，在基片上再通过逆反应使源物质重新 分解出来。Chemical transport reaction: The film material as a source material (non-volatile matter), by means of a suitable gaseous medium react to form gaseous compounds, such gaseous compounds through chemical or physical transport migrate to a differe

44、nt deposition source zone temperature area, on the substrate and then through the reverse reaction of the source material break out again.CVD的必要条件Necessary conditions for CVD （1）在沉积温度下，反应物具有足够的蒸气压，并能以适当的 速度被引入反应室；At the deposition temperature, the reactant has sufficient vapor pressure, and can be i

45、ntroduced into the reaction chamber at an appropriate rate; （2）反应产物除了形成固态薄膜物质外，都必须是挥发性的； In addition to the formation of the reaction product of solid film material, it must be volatile; （3）沉积薄膜和基体材料必须具有足够低的蒸气压Deposited films and substrate materials must be sufficiently low to vapor pressure什么是低压CVD

46、和等离子CVD？What is the low pressure CVD and plasma CVD? 1.低压CVD（LPCVD）（1）气体压力1毫乇 - 1托（而不是1个大气压）;（2）较高的初始气体浓度（3）气体到基片的下部，P =>到较高的D;（4）表面反应往往成为速率限制;（5）的优点：更好的薄膜均匀;更好的薄膜覆盖在步骤;较少的缺陷1. Low Pressure CVD (LPCVD)(1)gas pressures 1 mtorr - 1 torr (rather than 1 atm) ;(2)higher initial gas concentrations(3)lo

47、wer P => higher D of gas to substrate ;(4)surface reaction often becomes rate limiting ;(5)advantages:better film uniformity;better film coverage over steps ;fewer defects2，等离子增强化学气相沉积（PECVD）（1）血浆中衬底的附近（2）等离子体打破了气体分子（3）较高的反应（4）可以使用较低的温度（5）可以使用较低的压力（6）等离子电子：电离气体，以保持等离子;“激活”气解离，以提高心血管疾病;通常为约1的气体被激活

48、;压力比在溅射沉积更高2. Plasma Enhanced CVD (PECVD)(1)plasma in vicinity of substrate (2)Plasma breaks up gas molecules(3)higher reactivity(4)can use lower temperatures (5)can use lower pressures（6）electrons in plasma:ionize gas to keep plasma going；"activate" gas by dissociation to enhance CVD ；typ

49、ically about 1% of gas is activated；pressures are higher than in sputter deposition低压下气体扩散系数增大，使气态反应物和副产物的质 量传输速率加快，形成薄膜的反应速率增加。The gas diffusion coefficient increases with the increase of the gas diffusion coefficient, so that the mass transfer rate of the gaseous reactants and byproducts is accele

50、rated, and the reaction rate of the film is increased.对于等离子化学气相沉积 ，如果能在反应室内形成低温等离子体（如辉光放电），则可以利用在等离子状态下粒子具有的较高能量，使沉积温度降低。For plasma chemical vapor deposition, if they can form a low temperature plasma in the reaction chamber (such as glow discharge), you can use a higher energy particles have an ionic state in, so that the deposition temperature is lowered. 薄膜形成的基本过程描述The basic process described film formation薄膜形成分为：凝结过程、核形成与生长过程、岛形成与结合 生长过程Thin film formation is divided into: coagulation, formation and g