Investigation on the Effect of in situ Plasma Supply During Growth of Polycrystalline Silicon Films by Low-Pressure Chemical Vapor Deposition, and on their Electric Conduction Properties

在熔融石英衬底上制备了多晶硅（poly-Si）薄膜，并对射频功率（0 ~ 30 W）、沉积温度（T_d = 620 ~ 770 C）和氢稀释比（H_2/SiH_4 = 0 ~ 8）的变化规律进行了研究。未掺杂多晶硅薄膜的结构变化及其抗外来污染稳定性。随着射频功率的增加，可以选择随机、<100>和<110>纹理的优先取向。在薄膜生长过程中，射频等离子体供应对结构性能的影响与T_d的降低或H_2/SiH_4的降低（SiH_4分压的增加）是等效的。此外，发现等离子体供应在工业上对平滑薄膜表面和提高抗外来污染（如氧气）的稳定性具有有用的作用。等离子体供应的结构变化可以用沉积速率的变化和sih相关吸附物表面扩散系数的变化来解释。用溅射效应来解释等离子体对表面粗糙度的进一步改善，这可能也是导致结构变化的原因。。掺杂效率。等离子体增强化学气相沉积法（PECVD）制备的多晶硅薄膜中磷和硼的掺杂效率与无等离子体供应的低压CVD （LPCVD）制备的多晶硅薄膜相比有很大提高。掺杂薄膜的结构与未掺杂薄膜相似。此外，PECVD膜的表面非常光滑，与掺杂水平无关，而LPCVD膜的粗糙度在中间掺杂范围内大大增加。薄膜晶体管的检验。研究了在未掺杂多晶硅薄膜上制备的薄膜晶体管的场效应迁移率。具有<110>结构的PECVD薄膜的迁移率最高，而具有随机结构的LPCVD薄膜的迁移率最低。从晶粒尺寸、择优取向和表面粗糙度等方面对这些结果进行了讨论。少

Polycrystalline Si (poly-Si) films were prepared on a fused quartz substrate as a function of the rf power (0-30 W), deposition temperature (T_d = 620-770ﾟC) and hydrogen dilution ratio (H_2/SiH_4 = 0 to 8).1. Structural Changes and Stability against Foreign Contamination in Undoped Poly-Si films. As the rf power is increased, the preferential orientation to a random, <100> and <110> texture can be selected. The effect of rf plasma supply during the film growth on the structural properties was found to act as an equivalent effect to a decrease in T_d or a decrease in H_2/SiH_4 (an increase in the partial pressure of SiH_4). Furthermore, the plasma supply was found to have industrially useful effects for smoothing the film surface and improving the stability against foreign contamination such as oxygen. The structural change with the plasma supply was interpreted in terms of both of a change in deposition rate and a change in a surface-diffusion coefficient of SiH-related adsorbates. Th … More e improvement of surface roughness with the plasma supply was explained in terms of a sputtering effect which is likely to be also responsible for the structural change.2. Doping Efficiency. The doping efficiency for phosphorus and boron in poly-Si films deposited by plasma-enhanced chemical vapor deposition (PECVD) method was largely improved as compared with that in poly-Si films prepared by low-pressure CVD (LPCVD) without plasma supply. The structure of doped films was similar to that of undoped films. Also PECVD films had very smooth surface independent of doping level, though the roughness of LPCVD films largely increased in an intermediate doping range.3. Examination of Thin-Film transistors. The field-effect mobility for thin-film transistors fabricated on the undoped poly-Si films was investigated. The highest mobility was observed for PECVD films exhibiting a dominant <110> texture, while LPCVD films with a random texture had the lowest mobility. These results were discussed in terms of the crystallite size, preferential orientation and surface roughness. Less