【作者】 齐雪莲；

【导师】 马腾才； 任春生；

【作者基本信息】 大连理工大学 ， 等离子体物理， 2008， 博士

【摘要】 本文的研究内容分为两大部分:第一部分研究了一种新型的薄膜制备技术,即会切场约束ICP(Inductively Coupled Plasma)增强非平衡磁控溅射沉积薄膜技术,并应用该技术在合适的参数条件下沉积了性能良好的铜膜;第二部分用发射光谱和Langmuir探针研究了该技术中等离子体参数随气压、射频功率、会切磁场及放电室中不同位置处的变化规律。ICP增强非平衡磁控溅射技术使用自制的非平衡磁控溅射装置,外加以射频线圈增强等离子体电离,并在基片台上加脉冲负偏压,来增加离子到达基片的速率。溅射靶位于真空室内上方,和真空室上壁之间采用绝缘的聚乙烯连接。放电室外共有两组永久磁铁:真空室外侧环绕真空室的三匝永久磁铁环和溅射靶上面的永久磁铁。两组磁铁产生的磁场在真空室中相互叠加,形成会切场磁场位形。此设备在实现射频放电及射频增强磁控溅射放电过程中,在会切场的约束下,放电室中间区域等离子体均匀。在调节气压、功率及考虑到离子流密度不致过大的情况下,选择了沉积铜膜的最佳沉积参数。我们在传统的磁控溅射沉积的基础上,由柱形真空室外增加的永久磁铁和靶上面的永久磁铁叠加形成会切磁场约束作用,增加了电子的自由程,提高了等离子体的电离率。真空室外还加了由柱状天线传输的射频功率,进一步激励等离子体,增强了等离子体的密度和电子温度。实验过程中,使用纯度为99.99%的高纯氩气,纯度为99.9%的铜作为溅射靶。用发射光谱法研究了射频放电氩等离子体随射频功率、气压和放电室中位置的变化规律,选用了两条特定氩的原子和离子谱线。射频放电中谱线强度表现出了模式跳变和回滞现象,即射频功率增加到400 W时,射频放电从E模式跳变到H模式,Ar原子谱线强度证明了增加的跳变,而Ar~+谱线强度只是有小的变化,而从高功率降低时,到300W时射频放电从H模式跳变到E模式。还用发射光谱法研究了放电室在有无会切磁场及射频情况下,特定的氩和铜的原子和离子谱线的变化情况,从而定性的研究等离子体参数的变化。用Langmuir探针测量了放电室内等离子体参数。研究了射频放电时,等离子体参数如电子温度、电子密度和离子密度等在轴向和径向的分布及会切磁场会对等离子体参数的影响。证实了在有外约束磁场的情况下,ICP增强的非平衡磁控溅射等离子体参数都有明显的提高。用该实验设备在硅基片上沉积了铜膜。在如下三种条件下沉积了薄膜:有射频无会切磁场、无射频有会切磁场和有射频有会切磁场。膜的表面形貌和织构通过扫描电子显微镜(SEM)和X射线衍射(XRD)测得。用电子能谱(ES)对薄膜的成分进行了分析。膜的表面特性由原子力显微镜(AFM)和来自原子力显微镜数据的粗糙度来表征。电阻率通过四探针法测量。通过比较最后的实验结果,表明射频和会切磁场的加入明显改善了放电室中等离子体参数如电子温度、电子密度及离子密度等。因此,在有射频和会切磁场时,膜的表面光滑致密,晶粒尺度在几百纳米,粗糙度也不大,电阻率最小。原因可能是射频放电和会切磁场增强等离子体密度,高密度的等离子体在相同的脉冲偏压下能更好的改善了离子轰击效应。离子轰击可以明显地影响着沉积Cu膜的表面生长和性能。通过实验,可以找到沉积性能好的Cu膜的最佳实验参数,并希望这一工艺能应用在集成电路中。更多还原

【Abstract】 The present work includes two main parts: The first part mainly investigates a new technique of thin film deposition, referred as to the technology of thin film deposition by ICP enhanced unbalanced magnetron sputtering process in cusp-field confined magnetron. Then it is applied to deposit Cu film of good characteristics under appropriate parameter condition. In the second part, the regularity of plasma parameter, which varies with the air pressure, the power of radio frequency (rf), the cusp magnetic field and different positions in the chamber is studied, by using the emission spectrometry and Langmuir probe.The self-regulating unbalanced magnetron sputtering device and rf winding, which enhance the plasma ionization, are used in ICP (Inductively Coupled Plasma) enhanced unbalanced magnetron sputtering technique. The pulse minus bias voltage is applied to the substrate to increase the velocity of ions arriving at the substrate. The magnetron target is lied above the vacuum chamber, connected with the chamber’s upper wall by the insulating polyethylene. There are two groups of permanent magnet outside the discharge chamber: one is three circles of permanent magnet hoop around the outside of the vacuum chamber, and the other is a permanent magnet on the top of the sputtering target. The magnetic fields resulting from the two groups above interact with each other and form a figure of cusp magnetic field. With the confinement of the cusp magnetic field, during the rf discharge and rf enhanced magnetron sputtering discharge, the uniform plasma could be obtained in the middle area of the chamber. The optimum parameters of Cu film deposition are chosen by adjust considering the pressure, the power of rf and the ion current which should not be over large. On the basis of the conventional magnetron sputtering, the permanent magnets outside the column vacuum chamber and above the target interact with each other and form a combined cusp magnetic field, which plays the role of confinement and increases the electron free path, and improves the plasma ionization rate as well. Besides this, the rf power is added through a cylinder antenna to inspire the plasma further and increase plasma density and electron temperature effectively.In this experiment, Ar with the purity of 99.99% is used as discharging gas, and Cu with the purity 99.9% is used as the material of sputtering target. The changing regularity of rf Ar plasma, which varies with the power of radio frequency, the air pressure and the position in the discharge chamber, is investigated by the emission spectrometry. Two given atom and ion spectral lines of Ar are selected. The intensity of spectral lines in RF discharge shows a jumping mode and a hysteresis phenomenon with the change of RF power. When the rf power increases to 400 W, the discharge jumps from E-mode to H-mode, where the line intensity of Ar atom demonstrates an increase jumpily, but the intensity of Ar~+ ion only has a little bit changes. If the RF power decreases from a high power, such as from 1000 W, the discharge jumps from H-mode back to E-mode at 300W. Moreover, under the condition of with or without cusp magnetic field and rf, the change of given atom and ion lines of Ar and Cu is studied by the method of emission spectrometry. In this way, the variety of plasma parameters is investigated qualitatively. The plasma parameters in the discharge chamber are measured by Langmuir probe. The distributing of the plasma parameters (electron temperature, electron density and ion density) at the axis and radial and the influence of cusp magnetic field on plasma parameters are investigated during the process of rf discharge. It has been proved that, with the confinement of cusp magnetic field, parameters of ICP enhanced unbalanced magnetron sputtering plasma are improved obviously.Cu films are deposited on the Si substrate by using this experiment equipment. The films are deposited under three conditions as follows: with rf and without cusp magnetic field, without rf and with cusp magnetic field and with rf and with cusp magnetic field. The morphology and structure of films are examined by scanning electron microscopy (SEM), x-ray diffraction (XRD) and electron spectroscopy (ES). The surface average roughness of the deposited Cu film is characterized by atomic force microscope (AFM) data. The resistivity is measured by four probe method. The results show that rf and cusp magnetic field play an important role in plasma discharge and improve plasma parameters significantly, including electron temperature, electron and ion density. Therefore, the Cu film deposited with rf discharge enhanced ionization and cusp magnetic field confinement has smooth and dense surface, low surface roughness and low resistivity. The scale of the crystal grain is about 100～1000 nm. The reason may be attributed to that the rf discharge and cusp magnetic field could enhance the plasma density, which further improves ion bombardment effect under the same bias voltage. Ion bombardment can influence the growing feature and characteristics of deposited Cu films obviously. From the experiments, the best experiment parameters for the deposition of Cu film with good characteristics can be found. This technique will be contributed to integrated circuit, and is expected to be applied to practical work.更多还原