Effects on low energy ion irradiation for synthesis of carbon nitride thin films

采用电子回旋共振（ECR）等离子体溅射法，以碳靶为靶，在不同工艺参数下制备了氮化碳薄膜。重点研究了基片偏压、等离子体气氛、微波输入功率、基片材料和基片温度等工艺参数。采用XPS、FT-IR、拉曼等测试手段对薄膜中氮原子浓度（N/C原子比）及氮原子和碳原子的化学键结构（N-spC、N-sp^2 C、N-sp^3 C）进行了分析，结果表明，薄膜的氮原子浓度、化学键结构等性质明显地依赖于衬底上施加的正、负偏压。在基片偏压为-40V、微波输入功率为200 W、纯氮等离子体条件下，N/C原子比达到0.35。在低于-50 V的衬底偏压下，由于对沉积的氮原子进行了再溅射，氮原子主要与sp^3和sp^2杂化碳原子发生化学键合，因此氮原子不存款。工艺参数中氮气分压和微波输入功率的增加导致（N-sp^3C）/（N-sp^2C）峰面积比的增加。工艺参数中衬底偏压的降低导致（N-sp^3C）/（N-sp^2C）峰面积比的增加。N2+浓度的增加对上述结果有影响实验结果表明，在ECR等离子体中控制低能氮离子束（40 eV以下）和高离子束流密度的离子轰击生长膜表面，有利于亚稳晶态氮化碳膜的生长。通过与亚注入模型的比较，提出了亚稳相形成的生长模型被讨论了。实验结果表明，亚稳态模型可以定性地应用于亚稳相氮化碳薄膜的形成。

Carbon nitride thin films were synthesized by electron cyclotron resonance (ECR) plasma sputtering method with a carbon target and under various process parameters. Especially, substrate bias voltage, plasma atmosphere, microwave input power, substrate materials and substrate temperature as the process parameters were investigated. The nitrogen concentration (N/C atomic ratio) and chemical bond structure (N-spC, N-sp^2C, N-sp^3C) of nitrogen and carbon atoms in synthesized thin films were discussed with XPS, FT-IR, Raman spectroscopy.The nitrogen concentration, chemical bond structure and other properties of carbon nitride thin films were clearly dependent on the positive and negative bias voltage applied to the substrate. The N/C atomic ratio reached to 0.35 at pure nitrogen plasma, -40V in substrate bias voltage, 200 W in microwave input power. The firms do not deposit at less than -50V of substrate bias voltage, because of re-sputtering the deposited firm.Nitrogen atoms in the firms are chemically bonded mainly with sp^3, and sp^2 hybridized carbon. Increasing the nitrogen partial pressure and microwave input power in process parameter lead up to increase the peak area ratio of (N-sp^3C)/(N-sp^2C). Decreasing the substrate bias voltage in process parameter leads to increase the peak area ratio of (N-sp^3C)/(N-sp^2C). These results were affected the increase of the N2+ ion density in the ECR plasma.These experimental results demonstrate that the ion bombardment onto the growing film surface with controlled low energy nitrogen ion of below 40eV and high ion flux density is favorable to synthesize of the metastable crystalline carbon nitride films.A growth model for formation of metastable phase in comparison between these experimental results and subimplantation model were discused. Our experimetnal results were implied that the subimplantaiton model could be applied qualitatively for the formation of metastable phase carbon nitride films.