射频反应磁控溅射制备AIN薄膜及其物理性能分析

【作者】 郑晓娟；

【导师】 张庆瑜；

【作者基本信息】 大连理工大学 ， 材料物理化学， 2004， 硕士

【摘要】 作为宽能隙直接能带结构半导体材料，AlN、GaN、InN等Ⅲ族氮化物由于高效率可见光和紫外光发射以及光响应特性而在全色光器件方面具有良好的应用前景。其中，AlN还具有高热导、高硬度以及良好的介电性质、声学性质和化学稳定性，可望在短波光发射和光探测、表面声学、压电器件等光电子和微电子器件方面得到广泛应用。本文采用RF反应磁控溅射方法在n-Si(100)、熔融石英上外延生长AlN薄膜，主要考察了沉积温度和工作气压对薄膜结构性能等的影响。并且利用卢瑟福背散射分析(RBS)、原子力显微镜(AFM)、透射电子显微镜(TEM)、X射线衍射(XRD)、反射高能电子衍射(RHEED)、傅立叶红外吸收谱(FTIR)和椭偏仪等分析方法对薄膜的表面形貌、组织结构进行了检测与分析；通过AlN薄膜在可见光范围内的吸收光谱、扫描电镜(SEM)研究了石英衬底上AlN薄膜的折射率、膜厚、能带宽度等光学特性；通过对射频反应磁控溅射制各AlN薄膜的等离子体气氛进行了原子发光光谱分析，提出一种新的光谱谱线标定的方法，建立了光谱半定量分析的模型，系统地研究了等离子体气氛中元素谱线强度随放电条件的变化趋势。 本论文的主要研究内容及结论如下： Ⅰ不同沉积温度下，纳米AlN薄膜的表面形貌和结晶特性分析 A在较高的工作气压(2.5Pa)下合成的AlN薄膜均具有原子量级平滑的表面，在室温至550℃的沉积温度范围内，薄膜表面粗糙度(RMS)为0.2nm-0.4nm，且不随沉积温度的增加而发生明显变化；而薄膜的生长行为则有比较显著的差异，大体上分成三个类型：室温下的非扩散生长、150℃-450℃时的有限扩散生长和550℃的扩散生长。 B沉积温度为室温的薄膜，其晶粒尺度为10nm左右；沉积温度为550℃的薄膜，其晶粒尺度为20-30nm。在室温至550℃的沉积温度范围内，薄膜的折射率随沉积温度的增加而增加，说明薄膜的致密度和结晶性随着沉积温度的增加而逐渐变好。 Ⅱ不同工作气压下，AlN薄膜的表面形貌和结晶取向分析 A从薄膜的表面形貌和组织结构来看，在一定温度下，随着工作气压由1.2Pa降低到0.3Pa，表面岛的尺寸越来越大；薄膜由多晶结构逐渐转向(002)择优取向，即倾向于c轴方向生长。 B从薄膜界面处的状态来看，AlN薄膜的生长过程大致分为三个阶段：非晶层，成核、竞争长大区，枝晶区。其中生长初期的约5nm左右的非晶层对形成c轴取向的AlN薄膜枝晶结构是有益处的。 Ⅲ不同工作气压下，AlN薄膜的光学性能和微观结构研究射频反应磁控溅射制备AIN薄膜及其物理性能分析A通过对石英衬底上AIN薄膜的吸收光谱的分析计算，所制备AIN薄膜的光学常数如 下:AIN薄膜的膜厚在388一1158nm之间;折射率n633在1.8915一2.0346之间，n350 在1.9854一2.1254之l旬;消光系数无。33在0.2625xlo一2.2700 xzo一之间，无35。，在 2.2500xlo一3一4.s700xlo一3之l’ed;能带宽度在5，590一6.logev之l’gl。B利用X射线衍射(XRD)对石英衬底上的AIN薄膜进行了表征，我们认为:在同一实 验条件下，晶体衬底和非晶衬底上的AIN薄膜的织构大致是一样的;随着工作气压 的降低、沉积温度的升高，能够获得高质量的AIN薄膜，薄膜的单晶取向性逐渐增 强;而薄膜的折射率、能带宽度亦随之增大，趋近于AIN单晶的光学特性，反映了 AIN薄膜的结构趋近于有序化，结晶特性逐渐变好。W对磁控溅射生成AIN薄膜的等离子体气氛的光谱分析A可以通过提高溅射功率、降低工作气压、选择合适的氮气百分含量等方式来降低成膜 空间中O、Ai等杂质的含量，从而降低薄膜中的杂质含量。B降低工作气压、增加氮气百分含量有助于提高成膜空间中活性N和活性Al的谱线强 度比。更多还原

【Abstract】 The Ill-nitrides AlN, GaN and InN with related alloys form an interesting class of wide bandgap materials, which are likely to be the basis of a strong development of a novel family of semiconductor device, for Optronics as well as for electronics. For example, the entire spectral region from UV to red can be covered with III-N optical devices. Furthermore, AlN has some outstanding physical properties that have attracted much interest. Its hardness, high thermal conductivity, resistance to high temperture and caustic chemicals, makes AlN an attractive material for electronic and optical devices. However, the majority of interest in AlN stems from the properties of its alloys with GaN which may permit the fabrication of AlGaN based optical devices which are active from the blue wavelength well into the UV.In this study, AlN thin films have been deposited on n-Si (100) and quartz substrates by reactive radio frequency magnetron sputtering. And the influence of substrate temperture and sputtering pressure is emphasized. The morphological and structural chacterizations have been determined by Rutherford backscattering spectroscopy, atomic force microsiscopy, transmission electron microscopy, x-ray diffraction, reflection high energy electron diffraction, Fourier transform infrared spectroscopy and ellipsomerty. Optical constants and thickness have been analyzed from the transmittance and scanning electron microscopy. In the mean time, the relationships between intensity of line spectrum of aluminium, nitrogen, argon, oxygen and sputtering parameter were discussed from emission spectrum of the plasma ambience.The major points of this work were summarized as folio wings:I Morphological and structural characterization of nano-scale AlN thin films deposited at different substrate tempertureA. AlN thin films in nano-scale deposited at high sputtering pressure (2.5Pa) are with atomistic smoothness. And the surface roughness with a root mean square(rms) roughness ~0.4nm has little changes with the substrate temperture varied from room temperature to 550C. But AlN thin film growth behavior varies with substrate temperture and could be classified into three types which are the growth with non-diffusion at room temperture, the growth with finite diffusion at 150C-450C, the growth with diffusion at 550C.B. The grAlN size of the film deposited at 550C is in the range of 20 nm to 30 nm, while thegrAlN size of the film deposited at room temperature is about 10 nm. And the rising of refractive index of AlN thin film with increasing substrate temperture shows that the crystallization of AlN thin films are improved.II Morphological and structural characterization of AlN films deposited at various sputteringpressureA. At a certAlN substrate temperature, the decreasing sputtering pressure from 1.2Pa to 0.3Pa makes the size of surface island largened obviously. Furthermore, the preferred orientation of the AlN film changes from polycrystalline structure to c-axis oriented as the sputtering presure decreasing.B. The growing process of AlN film could be divided into three stages which are the amorphous region, the region of nucleation and competition in the growth, the growth of crystalline AlN. Moreover, the amorphous layer of 5 nm thickness in the initial stage provides nucleation sites for the groeth of c-axis oriented crystallites.IllOptical and structural characterization of AlN films deposited at various sputtering pressureA. The ranges of the optical constants calculated from the transmittance in the spectral range of 190-1100 nm are as follows: thickness d =388-1158nm, refractive index n633=1-8915 -2.0346, n350=1-9854-2.1284, extinction coefficient k633=0.2625x10-3-2.2700x10-3, k350 =2.2500x10-3-4.8700x10-3. The optical band gaps ranges between 5.590 and 6.109 eV.B. The crystal structure and crystalline orientation of AlN films on quartz substrate were measured by x-ray diffraction. It is found that structural characterization of AlN films are similar deposited on whether n-Si (100) or quartz substrate.更多还原