Department of Chemistry, Wayne State University, Detroit, Michigan 48202, USA.
Department of Materials Science and Engineering, University of Texas at Dallas, Richardson, Texas 75080-3021, USA.
J Chem Phys. 2017 Feb 7;146(5):052813. doi: 10.1063/1.4968848.
The initial stages of cobalt metal growth by atomic layer deposition are described using the precursors bis(1,4-di-tert-butyl-1,3-diazadienyl)cobalt and formic acid. Ruthenium, platinum, copper, Si(100), Si-H, SiO, and carbon-doped oxide substrates were used with a growth temperature of 180 °C. On platinum and copper, plots of thickness versus number of growth cycles were linear between 25 and 250 cycles, with growth rates of 0.98 Å/cycle. By contrast, growth on ruthenium showed a delay of up to 250 cycles before a normal growth rate was obtained. No films were observed after 25 and 50 cycles. Between 100 and 150 cycles, a rapid growth rate of ∼1.6 Å/cycle was observed, which suggests that a chemical vapor deposition-like growth occurs until the ruthenium surface is covered with ∼10 nm of cobalt metal. Atomic force microscopy showed smooth, continuous cobalt metal films on platinum after 150 cycles, with an rms surface roughness of 0.6 nm. Films grown on copper gave rms surface roughnesses of 1.1-2.4 nm after 150 cycles. Films grown on ruthenium, platinum, and copper showed resistivities of <20 μΩ cm after 250 cycles and had values close to those of the uncoated substrates at ≤150 cycles. X-ray photoelectron spectroscopy of films grown with 150 cycles on a platinum substrate showed surface oxidation of the cobalt, with cobalt metal underneath. Analogous analysis of a film grown with 150 cycles on a copper substrate showed cobalt oxide throughout the film. No film growth was observed after 1000 cycles on Si(100), Si-H, and carbon-doped oxide substrates. Growth on thermal SiO substrates gave ∼35 nm thick layers of cobalt(ii) formate after ≥500 cycles. Inherently selective deposition of cobalt on metallic substrates over Si(100), Si-H, and carbon-doped oxide was observed from 160 °C to 200 °C. Particle deposition occurred on carbon-doped oxide substrates at 220 °C.
采用双(1,4-二叔丁基-1,3-二氮杂戊二烯基)钴和甲酸作为前驱体，描述了原子层沉积法钴金属生长的初始阶段。在 180°C 的生长温度下，使用钌、铂、铜、Si(100)、Si-H、SiO 和掺碳氧化物衬底。在铂和铜上，厚度与生长循环数之间的关系在 25 到 250 个循环之间呈线性关系，生长速率为 0.98 Å/循环。相比之下，在获得正常生长速率之前，在钌上的生长会延迟多达 250 个循环。在 25 和 50 个循环后没有观察到薄膜。在 100 到 150 个循环之间，观察到快速生长速率约为 1.6 Å/循环，这表明发生了类似于化学气相沉积的生长，直到钌表面被约 10nm 的钴金属覆盖。原子力显微镜显示，在 150 个循环后，铂上的钴金属薄膜光滑连续，均方根表面粗糙度为 0.6nm。在铜上生长的薄膜在 150 个循环后具有 1.1-2.4nm 的均方根表面粗糙度。在 250 个循环后，在钌、铂和铜上生长的薄膜的电阻率均小于 20μΩcm，在 150 个循环以下，其值与未涂层衬底的电阻率接近。在铂衬底上生长 150 个循环的薄膜的 X 射线光电子能谱显示钴的表面氧化，其下是钴金属。对在铜衬底上生长 150 个循环的薄膜进行类似分析表明，整个薄膜中都含有氧化钴。在 Si(100)、Si-H 和掺碳氧化物衬底上，经过 1000 个循环后，没有观察到薄膜生长。在热 SiO 衬底上，经过≥500 个循环后，形成了约 35nm 厚的二钴甲酸层。在 160°C 至 200°C 之间，观察到钴在金属衬底上相对于 Si(100)、Si-H 和掺碳氧化物的选择性沉积。在 220°C 时，在掺碳氧化物衬底上发生了颗粒沉积。
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