Low-temperature growth of epitaxial ß-SiC on Si(100) using supersonic molecular beams of methylsilane
Low-temperature growth of epitaxial ß-SiC on Si(100) using supersonic molecular beams of methylsilane
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DOI：
10.1021/jp020905u
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发表时间：
2002-08-22
影响因子：
3.3
通讯作者：
Sibener, SJ
中科院分区：
文献类型：
--
作者：
Sanchez, EC;Sibener, SJ
在Si（100）衬底上成功地生长了外延β-SiC薄膜，其衬底温度比常规CVD生长中所用的衬底温度低得多。这已经实现了使用通过播种超声分子束传递的能量和空间定向的甲基硅烷。在830-1030 K的衬底温度范围内，甲基硅烷的动能显著影响薄膜的形貌和生长行为，并提高了薄膜的生长效率。从热束（0.079 eV）获得的膜仅通过涉及向外扩散的硅原子与前体物质的反应的简易机制生长，与通过硅表面的反应性转化的所谓的“缓冲层”的生长相同。在适度较高的动能（0.45 eV），第二生长机制打开，除了硅外扩散过程。在较高入射能量下的生长可以生长较厚的膜，即，不受厚度限制，并且在有或没有缓冲层的情况下以基本相同的速率发生。在裸衬底上生长的膜的形态演变通过有坑的缓冲层或过渡层进行，这允许由于晶格失配而导致的应变松弛。最终获得的连续的无空隙的膜表现出几乎二维生长的立方外延材料的双简并域结构特征。此外，显着的正方形和方位对齐的孤立的三维特征，确定为Si岛观察到生长的同时与二维SiC膜。低于900 K生长的薄膜，虽然也是外延β-SiC，但不显示这些孤立的三维特征，并且比高于900 K生长的薄膜粗糙得多。这些结果强调，新的，增强的电子材料沉积的生长制度，可以通过使用高强度和速度调谐的超声分子束提供动力学加速中性分子作为有效的生长前体。这些实验还表明，较低的基板的热范围可能，有利的情况下，成为可访问的高品质的薄膜生长时，使用超声分子束外延（SMBE）的沉积方法。
Epitaxial beta-SiC films have been successfully grown on Si(100) at substrate temperatures considerably lower than those used during conventional CVD growth. This has been achieved using translationally energetic and spatially directed methylsilane delivered via seeded supersonic molecular beams. Methylsilane kinetic energy was found to dramatically affect both film morphology and growth behavior, as well as the enhancement of growth efficiency in the substrate temperature range 830-1030 K. Films obtained from thermal beams (0.079 eV) grow only through the facile mechanism involving the reaction of out-diffused silicon atoms with precursor species, identical to the growth of so-called "buffer layers" via the reactive conversion of the silicon surface. At moderately higher kinetic energies (0.45 eV), a second growth mechanism opens which operates in addition to the silicon out-diffusion process. Growth at the higher incident energy can grow thicker films, i.e., is not thickness-limited, and occurs with essentially the same rates with or without a buffer layer. The morphological evolution of films grown on bare substrates proceeds through a pitted buffer or transitional layer, which allows,for the relaxation of strain due to lattice mismatch. The continuous, void-free films eventually obtained exhibit the doubly degenerate domain structure characteristic of cubic epitaxial material growing nearly two-dimensionally. Furthermore, remarkable square-pyramidally shaped and azimuthally aligned isolated three-dimensional features identified as Si islands are observed to grow simultaneously with the two-dimensional SiC film. Films grown below 900 K, though also epitaxial beta-SiC, do not show these isolated three-dimensional features, and are much rougher than films grown above 900 K. These results emphasize that new, enhanced growth regimes for electronic materials deposition can be achieved by using high-intensity and velocity-tuned supersonic molecular beams to deliver kinetically accelerated neutral molecules for use as efficient growth precursors. These experiments also suggest that lower substrate thermal ranges may, for favorable cases, become accessible for growing high-quality films when using supersonic molecular beam epitaxy (SMBE) deposition methods.