【作者】 丁万昱；

【导师】 邓新绿； 徐军；

【作者基本信息】 大连理工大学 ， 等离子体， 2007， 博士

【摘要】 自1956年IBM向世人展示了世界上第一台商用磁盘至今，已有五十余年。其间，磁盘虽没有象CPU那样经历了飞速发展，但其存储密度在不断增加。尤其在近年来，随着巨磁阻磁头（GMR）、磁阻磁头（MR）等技术的应用，磁盘存储密度迅速提高（年增长100％）。同时，由于人们对计算机的依赖程度越来越高，“磁盘有价，数据无价”，因此人们在对磁盘存储密度提出更高要求的同时，对其使用寿命以及可靠性也提出了更高的要求，即对磁头／磁盘保护膜的性能提出更高要求。提高磁存储密度要求必须减小磁头和磁盘间隙，即减小磁头／磁盘保护膜厚度。未来，在磁存储密度达到1T bit／in²时，磁头／磁盘保护膜在具有必要的抗腐蚀、抗磨损性能同时，要求其厚度降至2.5nm以下。本论文围绕微波电子回旋共振等离子体性质，采用非平衡磁控溅射技术，开展一系列研究工作，制备出满足磁头／磁盘保护膜使用要求的超薄a-SiN_x薄膜。主要研究内容如下：（1）在微波电子回旋共振等离子体对Si原子腐子、N离子／活性基团密度的影响研究中发现：Si靶的溅射产额并不受微波功率变化的影响，而只与其射频溅射功率有关；然而，在N₂流量不变的情况下，等离子体密度、以及等离子体中N离子／活性基团的相对含量却随着微波功率的增加而增加。在空间等离子体中Si原子／离子含量不变（恒定Si靶溅射功率）、以及N₂流量不变的情况下，N离子／活性基团密度，是影响a-SiN_x薄膜结构、性质的主要因素。因此，必须调节微波功率至较高值，以使N离子／活性基团密度保持一合适值，这样才能使Si原子／离子与其充分反应，生长出高性能的a-SiN_x薄膜。（2）在最优化实验参数过程中发现：在各实验参数中，N₂流量、Si靶溅射功率为最重要参数。Si靶溅射功率直接影响Si原子／离子的溅射产额，在恒定微波功率和N₂流量的条件下，增加Si靶溅射功率，Si原子／离子的溅射产额随之增加，在高功率（350W）下制备的薄膜，由于到达基片的Si原子／离子束流较高，因此薄膜显示较好的化学结构，以及较好的机械性能。在Si靶溅射功率恒定的情况下，N₂流量为2sccm时所制备的a-SiN_x薄膜中Si-N键含量最高，可达94.8％，此时薄膜中N／Si原子比例为1.33，满足Si₃N₄的化学配比；同时，薄膜显示出最佳的机械性能，硬度值达到23GPa，RMS为0.18nm，摩擦系数为0.1，且薄膜表现出优良的抗腐蚀、抗磨损性能。过量增加N₂流量，由于靶中毒以及N元素存在方式变化，导致沉积的薄膜转向富N结构，并且薄膜表现出较差的机械性能，以及较差的抗腐蚀、抗磨损性能。（3）在研究a-SiN_x薄膜膜厚极限过程中发现：在最优化参数下，即Si靶溅射功率为350W，Ar、N₂流量分别为20sccm和2sccm时，薄膜厚度与沉积时间呈线性关系，薄膜沉积速率为4.7nm／min。所制备的厚度为5nm的a-SiN_x薄膜，其FT-IR光谱显示结构以Si-N键为主。此时，薄膜硬度较Si基片增加1GPa有余，同时，薄膜显示出优良的抗腐蚀、抗磨损性能。以a-Al₂O₃／Si多层结构为基片，模仿磁头真实结构制备a-SiN_x／a-Al₂O₃／Si多层膜，并模仿磁头生产厂真实测试条件，研究a-SiN_x薄膜膜厚极限。实验结果表明，2nm的a-SiN_x薄膜可以为基底材料提供充分的抗腐蚀、抗磨损保护，a-SiN_x薄膜的膜厚极限（＜2nm）低于DLC薄膜和CN_x薄膜（4nm）。（4）在a-SiN_x薄膜沉积过程中，在恒定微波功率和Ar流量的条件下，虽然等离子体电位、电子温度等参数随N₂流量的增加单调下降，但是适当增加N₂流量，由于Ar^*的过量，因此MW-ECR等离子体中N⁺、N2⁺密度、以及等离子体密度都不断增加，在N₂流量为5sccm时，等离子体密度达到最高值。同时，随着N₂流量的增加，由于Si靶表面中毒现象加剧导致Si原子的溅射产额不断减少。综合这两方面的原因，在N₂为2sccm时制备的薄膜，显示出最佳的结构、最佳的机械性能，以及最佳的抗腐蚀、抗磨损性能。在高N₂流量情况下，由于Ar^*的减少而导致MW-ECR等离子体中N⁺减少，N元素主要以N²⁺形式存在；同时，由于Si靶中毒加剧导致Si原子的溅射产额严重下降，因此所制备薄膜显示为富N态结构，相应薄膜的各方面性能都严重下降。因此，在薄膜沉积过程中，等离子体中Si原子的密度，以及N元素的存在状态，是决定薄膜结构、性能的主要因素。更多还原

【Abstract】 It has been more than 50 years ever since IBM shipped the first magnetic disk in 1956. In recent years, the magnetic storage density is increasing at 100% per year, because of the using of GMR, and MR technologies. Furthermore, people’s dependence on computer has been increased to ever-higher levels. All those require disk devices should have much larger storage density, longer using life, and more reliability. One of the crucial issues to increase the storage density is the reduction of the fly height, which is the distance between the disk and the read/write head. As the result, the thickness of protective layers, which were deposited on both the disk and the read/write head, needs to be reduced correspondingly, for example, it should be less than 2.5 nm when the storage density reaches 1T bit/inch² in the near future. To prepare such ultrathin continuous layer with excellent anti-corrosion and antifriction and tribology properties to protect the underlied magnetic layer is one of the main challenges in the present magnetic storage R&D areas.In this thesis, the ultra-thin a-SiN_x film with acceptable properties was deposited by MW-ECR plasma enhanced unbalance magnetic sputtering system. The MW-ECR plasma characteristics and the film properties have been studied systematically. The results are summarized as follow:（1） The Si target sputtering yield was independent of MW power, but only related to the sputtering radio frequency power. The plasma density and N ion/active radicals density increased with the increasing of MW power. On the condition of keeping Si target sputtering power and N₂ flow rate constant, the N ion/active radical density was the key parameter that influenced the component, structure, and properties of a-SiN_x films. In order to deposit the films with acceptable properties, keeping high MW power was necessary which makes the Si atom/ion react with N ion/active radical sufficiently.（2） Si target sputtering power and N₂ flow rate were the key parameters. On the condition of keeping other parameter constant, Si atom/ion sputtering yield increased with the increasing of the sputtering power. The films deposited with 350 W sputtering power and 2 sccm N₂ flow rate displayed good stoichiometric, structure, and mechanical properties, such as stoichiometric of 1.33, 94.8% Si-N bond content, 23 GPa hardness, 0.18 nm RMS, and excellent anti-corrosion property. But the a-SiN_x films deposited with high N₂ flow rate displayed poor mechanical properties because of rich N structure in film.（3） The a-SiN_x film thickness was linear with the deposition time. The film growth rate was 4.7nm/min, which was deposited at the optimum deposition parameters. 5 nm thickness a-SiN_x film deposited on Si substrate displayed acceptable anti-corrosion property and anti-wear property. 2 nm thickness a-SiN_x film deposited on a-Al₂O₃/Si substrate could stand the stringent corrosion test. The thickness limit with sufficient protection for the magnetic layer of a-SiN_x film could reach 2 nm, lower than that of DLC film and CN_x, film （4 nm）.（4） On the condition of keeping other parameter constant, the plasma potential and electron temperature T_e decreased monotonously with increasing the N₂ flow rate. The plasma density increasd with N2 flow rate and reached maximum when the N2 flow rate was 5sccm, this increase of plasma density could be attributed to the Ar^*-N2 collision process since the density of Ar metstable active state density was high when N₂ flow rate was less 5 sccm. So N⁺ and N₂⁺ density increased with increasing the N₂ flow rate proportionally, and reached to the peak value at 5 sccm N₂ flow rate. At the same time, Si atom sputtering yield decreased monotonously with increasing the N₂ flow rate, because of target poisoning phenomenon. These two factors resulted in the a-SiN_x film with the excellent structure and properties when N2 flow rate was set at 2 sccm. When N₂ flow rate was higher than 5 sccm, the density of Ar^* decreased tremendously, N₂⁺ was the main component in plasma. Combining with the serious target poisoning phenomenon, the a-SiN_x film was N-rich structure and displayed poor properties. The Si atom density and the N⁺ density were two crucial parameters which influenced the a-SiN_x film structure and properties.更多还原