Development of Low Temperature Deposition Process of Carbon Thin Film by Low Frequency 50Hz Plasma CVD.

氢化非晶碳(a-C：H)薄膜具有较大的热导率、化学惰性、较高的电阻率和击穿电场以及光学透明性，这些都适合作为微电子和机械应用中的涂层材料。关于用各种方法制备a-C：H薄膜的研究已经发表了许多报道。这种a-C：H薄膜的低温形成是微电子应用所必需的。本研究的目的是用氢气和甲烷(H_2+CH_4)混合气体，用50 Hz的低频等离子体CVD在未加热的衬底上沉积非晶碳膜。所获得的结果可概括如下：1)测量了目前a-C：H薄膜的主要电学和光学性质。薄膜的透明度很高，干涉颜色非常均匀。得到的a-C：H薄膜的折射率、电阻率、击穿场强和光学带隙分别为2.4、10…More&lt；14&gt；omega cm、10^6 V/cm和4.0 eV。在上述条件下，a-C：H薄膜的沉积速率为60A/H。2)红外吸收光谱和拉曼光谱表明，薄膜主要由sp3键组成。用双线辐射比法测量了H_2+CH_4等离子体的电子温度。在200 kHz以下，电子温度随等离子体频率的增加而缓慢下降，但在200 kHz~13.56 MHz之间，电子温度迅速下降。电子温度在1 kHz时为16000 K，在13.56 MHz时为8200K。由此推论，低频等离子体的电子温度高于高频等离子体的电子温度。4)从这些结果可以看出，在50 Hz的等离子体中，高温电子加速了H_2+CH_4气体的离解。此外，50赫兹等离子体中的正离子轰击沉积的薄膜，轰击的离子能量作为迁移能量用于沉积原子的重排。因此，用50 Hz等离子体CVD沉积的a-C：H薄膜在不需要衬底加热的情况下具有高质量的性能。较少

Hydrogenated amorphous carbon (a-C : H) films show large thermal conductivity, chemical inertness, high electrical resistivity and breakdown field, and optical transparency, all of which are suitable for the coating material in microelectronics as well as in mechanical applications. A number of reports have been published on the preparation of a-C : H films by various methods. The low-temperature formation of such an a-C : H film is required for microelectronics application. The purpose of the present study is to deposited of amorphous carbon films on unheated substrate using low frequency 50Hz plasma CVD with hydrogen and methane (H_2+CH_4) mixtures. The results obtained may be summarized as below.1) Major electrical and optical properties of the present a-C : H films were measured. The films were highly transparent and showed very uniform interference color. The refractive index, resistivity, breakdown field strength and the optical band gap of the obtained a-C : H film were 2.4, 10^ … More <14> OMEGA cm, 10^6 V/cm and 4.0 eV, respectively. The deposition rate of a-C : H films under the condition specified above was 60 A/h.2) Infrared absorption as well as Raman spectroscopy showed that the film predominantly consisted of sp^3-bonded C.3) The electron temperature for H_2+CH_4 plasma at 50Hz to 13.56MHz plasma power frequency range was measured from the two-line radiance ratio method using the Balmer lines (Halpha, Hbeta). The electron temperature slowly decreased with increased plasma frequency below 200 kHz, but rapidly decreased between 200 kHz and 13.56MHz. The electron temperature was 16000 K at 1kHz and 8200 K at 13.56 MHz. Accordingly, it was deduced that the electron temperature of low-frequency plasmas is larger than that in high-frequency plasmas.4) From these results, it appears that dissociation of H_2+CH_4 gas is accelerated by high temperature electrons in 50Hz plasma. Moreover, the positive ion in 50Hz plasmas bombard on the deposited film, and the bombarding ion energy is spent as migration energy for rearrangement of deposited atoms. Therefore, the deposited a-C : H films by the 50Hz plasma CVD have the high-quality properties without substrate heating. Less