Development of simultaneous in-situ measurements of size, density, and refractive index of particles in rf silane plasmas using a polarization-sensitive laser-light-scattering method

发展了一种偏振敏感激光散射方法，用于同时原位测量加工等离子体中形成的颗粒的性质（尺寸、尺寸分散、密度和折射率）以及尺寸和密度的二维空间分布。所开发的系统被应用于观察其尺寸大于约10 nm的范围内的颗粒在射频硅烷等离子体的生长过程。发现等离子体中颗粒的尺寸、尺寸分散（尺寸的标准偏差的对数）、密度和折射率分别为10-200 nm、约0.1、10^7 - 10^9 cm-<-3>1和约3-5i。该二维测量系统可以观测到50 × 200 mm ~ 3的放电区域，空间分辨率为2 × 2 × 2 mm ~ 3，时间分辨率为33 ms，并可以测量尺寸大于50 nm、密度大于10_6cm ~ 3的颗粒<-3>。前者这样的值同意相当不错，从扫描电子显微镜（SEM）观察推断。这些颗粒的生长经历了成核和初始生长、快速生长和生长饱和三个阶段。在快速生长阶段期间和之后通过SEM观察验证的具有窄尺寸分散体的两个尺寸组的颗粒的共存可以通过考虑带相反电荷的颗粒之间的凝聚的模型来解释。

A polarization-sensitive laser-light-scattering method is developed for simultaneous in-situ measurements of properties (size, size dispersion, density and refractive index), and two dimensional spatial distributions of size and density of particles formed in processing plasmas. The developed system is applied to observe the growth processes of particulates in a range of their size larger than about 10 nm in rf silane plasmas. A size, a size dispersion (logarithm of a standard deviation of size), a density, and a refractive index of particulates in the plasmas are found to be 10-200 nm, about 0.1,10^7-10^9cm^<-3> and about 3-5i, respectively. The developed two demensional system can view the whole discharge area of 50*200mm^3 illuminated by a sheet laser beam with a spatial resolution of 2*2*2mm^3 and a time resolution of 33 ms, and measure particles larger than 50 nm in size and higher than 10^6cm^<-3> in density. The former such values agree fairly well with ones deduced from scanning electron microscopic (SEM) observation. These particles grow through three phases of nucleation and initial growth, rapid growth and growth saturation. Co-existence of two size-groups of particulates with narrow size dispersions during and after the rapid growth phase verified by the SEM observation may be explained by a model taking into account coagulation between oppositely charged particulates.