双脉冲电场伏安特性对纯Ti薄膜结构及性能的影响
发布时间：2018-12-13 19:15
【摘要】：针对磁控溅射离子镀沉积粒子离化率低而造成的薄膜均匀性差等技术不足,依据等离子体物理学中气体放电伏安特性曲线中存在一强辉弱弧区间,探讨了强辉弱弧区间磁控阴极电场模式对纯金属Ti薄膜微观结构及性能的影响规律和可调控范围,以可观察的微观组织和可测的硬度等性能指标为依据,揭示了难以直接观察的阴极靶面沉积粒子瞬态脱靶方式随电场模式的演变规律,并通过对脱靶方式的调控以提高沉积粒子离化率。实验通过在阴极靶材与阳极腔体间构建具有较大电流密度和较强电场强度的高功率脉冲及双脉冲电场将气体放电引入强辉弱弧区间,借助Ar+轰击靶材产生的能量累积和靶材内电子传输产生的焦耳热积累,使沉积粒子因靶面温度迅速上升而引起大量的热发射,即实现了沉积粒子以碰撞增强热发射方式脱靶,并以此改善沉积薄膜的微观结构及综合性能。研究表明:在相同平均功率条件下,直流电场峰值电流密度处于较小值为0.04A/cm2,气体放电处于辉光区,薄膜表现出疏松、致密性差的结构,晶粒尺寸为28nm,表面粗糙度为127 nm,由此表明碰撞脱靶难以获得高能量、高离化率的沉积粒子导致薄膜性能较差。当采用高功率脉冲及双脉冲电场时,均可获得大于0.5 A/cm2的峰值电流密度,并且根据测得的电流密度达到0.2 A/cm2时气体放电进入反欧姆区,说明脉冲电场环境可将气体放电引入强辉弱弧区,实现了由Ar+单纯碰撞脱靶机制向Ar+碰撞和靶材热发射两种脱靶机制的混合脱靶方式的转变。沉积的薄膜表现出致密的结构,晶粒尺寸在20nm以内,粗糙度在20 nm左右。并且双脉冲电场平均沉积薄膜速率45.7 nm/min,约为高功率脉冲的2倍且接近直流的沉积速率,在靶基距240mm处薄膜最厚为1.496μm,正反厚度比为2.51最接近于1,说明碰撞增强热发射脱靶方式能够获得离化率及能量均较高的沉积粒子,从而改善了真空腔内沉积粒子分布的均匀性,并且薄膜具有致密的微观结构、优异的膜基结合强度及力学性能等。通过对双脉冲电场中不同峰值靶电流密度下沉积的薄膜结构与性能的研究发现,随着峰值电流密度的增加,薄膜在近靶处与远靶处的厚度差越来越小,最小达到1.4μm,沿靶基距方向的厚度减小率也从90 %降至77.8 %,正反厚度比最小为1.91。通过缩短脉冲开通时间,不但峰值电流密度增加,而且单脉冲内有足够的停顿时间使高活性和扩散能的沉积粒子在基片表面沉积成膜。随着靶峰值电流密度的增加,薄膜微观形貌越来越平整致密,在峰值电流密度为1.35 A/cm2时,划痕测试临界载荷最高达到13.7 N且划痕整体未出现断裂剥落现象,硬度及弹性模量最大分别为5.625 GPa和165.380 GPa,NaCl腐蚀溶液中的腐蚀速率仅为1.9655x10-4mm/a。最终,通过构建新型双脉冲电场及对其电流密度的调控可获得结构致密,性能优异的薄膜。
[Abstract]:In view of the lack of uniform film due to the low ionization rate of ion plating deposited by magnetron sputtering, there is a strong and weak arc region in the volt-ampere characteristic curve of gas discharge in plasma physics. The influence of the mode of magnetic controlled cathode electric field on the microstructure and properties of pure metal Ti thin films is discussed in the range of strong glow and weak arc. The controllable range is based on the observable microstructure and measurable hardness. The evolution law of transient miss mode with electric field mode of deposited particles on cathode target surface which is difficult to observe directly is revealed and the ionization rate of deposited particles is improved by adjusting the miss mode. In this experiment, high power pulse and double pulse electric field with high current density and strong electric field intensity were constructed between cathode target and anode cavity to introduce gas discharge into strong glow and weak arc region. With the energy accumulation generated by Ar bombarding the target material and the Joule heat accumulation caused by electron transport in the target material, a large amount of heat emission is caused by the rapid rise of the target surface temperature, that is, the deposition particles miss the target by collision enhanced heat emission. The microstructure and comprehensive properties of the deposited films are improved. The results show that under the same average power, the peak current density of DC field is 0.04A / cm ~ 2, the gas discharge is in the glow region, the thin film exhibits loose structure and poor compactness, and the grain size is 28 nm. The surface roughness is 127 nm, which indicates that the collision miss is difficult to obtain high energy, and the high ionization rate of the deposited particles leads to the poor performance of the film. When the high power pulse and double pulse electric field are used, the peak current density of more than 0.5 A/cm2 can be obtained, and the gas discharge enters the anti-ohmic region according to the measured current density of 0.2 A/cm2. It is shown that the gas discharge can be introduced into the strong glow and weak arc region in the environment of pulsed electric field, and the mixed miss mode can be changed from the pure collision mechanism of Ar to the two mechanisms of Ar collision and hot emission of target materials. The deposited films exhibit dense structure with grain size within 20nm and roughness of about 20 nm. The average deposition rate of double pulse electric field is 45.7 nm/min, which is about 2 times of that of high power pulse and close to DC. The film thickness is 1.496 渭 m at the target substrate distance from 240mm, and the ratio of positive and negative thickness is close to 1. The results show that collision enhanced thermal emission miss mode can obtain deposited particles with higher ionization rate and higher energy, thus improving the uniformity of particle distribution in the vacuum cavity, and the film has a compact microstructure. Excellent bonding strength and mechanical properties. The structure and properties of the films deposited at different peak current densities in a double-pulse electric field are studied. It is found that with the increase of the peak current density, the thickness difference between the near target and the distant target becomes smaller and smaller, and the minimum is 1.4 渭 m. The decrease rate of the thickness along the distance direction of the target is also reduced from 90% to 77.8%, and the minimum ratio of positive and negative thickness is 1.91. By shortening the pulse opening time, not only the peak current density is increased, but also there is enough pause time in the monopulse to make the highly active and diffusive particles deposited on the substrate surface. With the increase of the target peak current density, the microcosmic morphology of the film becomes more and more smooth and compact. When the peak current density is 1.35 A/cm2, the critical load of scratch test reaches 13.7 N and the whole scratch does not appear fracture and spalling phenomenon. The maximum hardness and modulus of elasticity are 5.625 GPa and 165.380 GPa,NaCl respectively. The corrosion rate is only 1.9655 x 10-4 mm / a. Finally, the thin films with dense structure and excellent performance can be obtained by constructing a new type of double-pulse electric field and regulating its current density.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4
[Abstract]:In view of the lack of uniform film due to the low ionization rate of ion plating deposited by magnetron sputtering, there is a strong and weak arc region in the volt-ampere characteristic curve of gas discharge in plasma physics. The influence of the mode of magnetic controlled cathode electric field on the microstructure and properties of pure metal Ti thin films is discussed in the range of strong glow and weak arc. The controllable range is based on the observable microstructure and measurable hardness. The evolution law of transient miss mode with electric field mode of deposited particles on cathode target surface which is difficult to observe directly is revealed and the ionization rate of deposited particles is improved by adjusting the miss mode. In this experiment, high power pulse and double pulse electric field with high current density and strong electric field intensity were constructed between cathode target and anode cavity to introduce gas discharge into strong glow and weak arc region. With the energy accumulation generated by Ar bombarding the target material and the Joule heat accumulation caused by electron transport in the target material, a large amount of heat emission is caused by the rapid rise of the target surface temperature, that is, the deposition particles miss the target by collision enhanced heat emission. The microstructure and comprehensive properties of the deposited films are improved. The results show that under the same average power, the peak current density of DC field is 0.04A / cm ~ 2, the gas discharge is in the glow region, the thin film exhibits loose structure and poor compactness, and the grain size is 28 nm. The surface roughness is 127 nm, which indicates that the collision miss is difficult to obtain high energy, and the high ionization rate of the deposited particles leads to the poor performance of the film. When the high power pulse and double pulse electric field are used, the peak current density of more than 0.5 A/cm2 can be obtained, and the gas discharge enters the anti-ohmic region according to the measured current density of 0.2 A/cm2. It is shown that the gas discharge can be introduced into the strong glow and weak arc region in the environment of pulsed electric field, and the mixed miss mode can be changed from the pure collision mechanism of Ar to the two mechanisms of Ar collision and hot emission of target materials. The deposited films exhibit dense structure with grain size within 20nm and roughness of about 20 nm. The average deposition rate of double pulse electric field is 45.7 nm/min, which is about 2 times of that of high power pulse and close to DC. The film thickness is 1.496 渭 m at the target substrate distance from 240mm, and the ratio of positive and negative thickness is close to 1. The results show that collision enhanced thermal emission miss mode can obtain deposited particles with higher ionization rate and higher energy, thus improving the uniformity of particle distribution in the vacuum cavity, and the film has a compact microstructure. Excellent bonding strength and mechanical properties. The structure and properties of the films deposited at different peak current densities in a double-pulse electric field are studied. It is found that with the increase of the peak current density, the thickness difference between the near target and the distant target becomes smaller and smaller, and the minimum is 1.4 渭 m. The decrease rate of the thickness along the distance direction of the target is also reduced from 90% to 77.8%, and the minimum ratio of positive and negative thickness is 1.91. By shortening the pulse opening time, not only the peak current density is increased, but also there is enough pause time in the monopulse to make the highly active and diffusive particles deposited on the substrate surface. With the increase of the target peak current density, the microcosmic morphology of the film becomes more and more smooth and compact. When the peak current density is 1.35 A/cm2, the critical load of scratch test reaches 13.7 N and the whole scratch does not appear fracture and spalling phenomenon. The maximum hardness and modulus of elasticity are 5.625 GPa and 165.380 GPa,NaCl respectively. The corrosion rate is only 1.9655 x 10-4 mm / a. Finally, the thin films with dense structure and excellent performance can be obtained by constructing a new type of double-pulse electric field and regulating its current density.
【学位授予单位】：西安理工大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TG174.4
【参考文献】
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