取向铜、镍镀层对键合界面反应的影响
发布时间：2019-03-29 13:04
【摘要】：随着微电子产品向高密度、窄间距、短路径的趋势发展,应用于三维叠层封装的互连焊点尺寸也显著减小。铜凸点由于具有良好机械性能和电学性能,被认为可代替传统的焊球微凸点,用于细节距高深宽比的高密度封装技术中。在微小化条件下,单个凸点所含晶粒减少导致其晶体学取向对键合界面反应的影响愈发明显,显著影响界面金属间化合物的形核与生长。目前对于晶体学取向对键合界面反应的影响的研究多基于单晶基板,而单晶基板的制作不易、成本高昂,实际应用中多应用电沉积多晶凸点。因此,明确电沉积工艺参数对于镀层择优取向的影响以及镀层织构对于界面金属间化合物生长的影响有着深刻的意义。为此,本课题探究镀液添加剂、电流密度、脉冲电镀等对于薄膜晶向择优性的影响。通过电沉积制备出具有两种不同择优取向的铜薄膜和镍薄膜,观察和研究不同择优取向铜和锡及镍和锡的键合界面反应,系统研究了镀层晶体学择优取向对金属间化合物生长的影响。在电沉积过程中,通过控制添加剂、电流密度、电源类型等电沉积条件可以获得具有特定择优取向的铜薄膜和镍薄膜。添加剂P-68使得铜薄膜择优取向明显表现为(220)方向。随着电流密度的升高,镍薄膜晶粒择优取向由(111)方向逐渐转为(200)方向。在直流条件下镍薄膜(200)晶面表现为明显的择优取向,脉冲条件下使(111)晶面开始表现出一定的择优性。原子在不同晶面扩散系数不同,当镀层取向存在择优性时,原子在其中的扩散也表现出各向异性。加之与固-液反应(回流)相比,决定固-固界面反应(时效)速率及生成物形貌的是反应原子的扩散速率。由于原子的扩散速率具有各向异性,因此在择优取向不同的镀层中具有不同的扩散速率,从而影响了界面反应产物的形貌和生长速率。(200)晶面上的原子排列比(220)晶面更为密排,因而原子在(200)晶面扩散更困难,扩散系数小于其在(220)晶面。Cu(200)-Sn界面处IMCs晶粒存在明显的小刻面,小刻面呈不同角度排列形成多边形花纹,且在晶粒间形成细小的孔,而在Cu(220)-Sn界面并未有类似现象。Cu3Sn优先形核与Cu(220)-Cu6Sn5界面,在晶界处存在优先形核长大的现象。Ni(220)-Sn界面处形成厚度相同大小不一的薄片状IMCs,而Ni(200)-Sn界面处的IMCs则呈等轴块状且晶粒大小均匀。Ni(220)-Sn界面薄片状IMCs中Ni/Sn原子比大于Ni(200)-Sn界面处的IMCs,时效反应充分进行时,两种IMCs中的Ni/Sn原子比例均发生变化达到3:4,即形成常见的镍锡金属间化合物Ni3Sn4。长时间时效,IMCs层持续生长,不断地消耗中间的锡镀层生成大块状金属间化合物,甚至可以消耗区别Sn层从而贯穿整个界面,此时Ni(220)-Sn界面处的IMCs组织松散出现孔洞与裂缝,这将影响键合界面的机械性能和电学性能。
[Abstract]:With the development of micro-electronic products to high density, narrow spacing and short path, the size of interconnect solder joint used in 3D laminated packaging also decreases significantly. Due to its good mechanical and electrical properties, copper bump is considered to be a substitute for traditional solder ball micro-bumps, which can be used in high-density packaging technology with the aspect ratio of detail distance to depth. Under the condition of miniaturization, the crystal orientation of a single convex point has a more and more obvious effect on the interfacial reaction and the nucleation and growth of intermetallic compounds at the interface are greatly affected by the decrease of the grain content in the single convex point. At present, the research on the effect of crystallographic orientation on bonding interface reaction is mostly based on single crystal substrate. However, the fabrication of single crystal substrate is not easy and the cost is high. In practical application, polycrystalline convex points should be deposited by electrodeposition. Therefore, it is of great significance to clarify the effect of electrodeposition process parameters on the preferred orientation of the coating and the effect of the coating texture on the growth of intermetallic compounds at the interface. In this paper, the effects of bath additives, current density and pulse plating on the orientation selection of thin films were investigated. Copper and nickel films with two different preferred orientations were prepared by electrodeposition. The interfacial reactions of copper and tin and nickel and tin with different preferred orientations were observed and studied. The effect of crystallographic preferred orientation on the growth of intermetallic compounds was systematically studied. In the process of electrodeposition, copper and nickel films with specific orientation can be obtained by controlling the electrodeposition conditions such as additive, current density, power supply type and so on. The preferred orientation of copper film was (220). With the increase of current density, the preferred orientation of nickel films changed from (111) to (200). The (200) crystal plane of nickel thin film exhibits obvious preferred orientation under DC condition, and the (111) crystal plane begins to show a certain degree of preference under pulse condition. The diffusion coefficients of atoms in different crystal planes are different. When the orientation of the coating is preferred, the diffusion of atoms in the coating also shows anisotropy. In addition, compared with solid-liquid reaction (reflux), it is the diffusion rate of the reaction atom that determines the reaction rate (aging) and morphology of the solid-solid interface reaction. Because the diffusion rates of atoms are anisotropic, they have different diffusion rates in coatings with different preferred orientations. As a result, the morphology and growth rate of the interface reaction products are affected. (200) the arrangement of atoms on the crystal plane is more dense than that on the (220) plane, so the diffusion of atoms on the (200) crystal plane is more difficult. The diffusivity is smaller than that on the (220) crystal plane. There are obvious small facets in the IMCs grain at the Cu (200)-Sn interface, which are arranged at different angles to form polygonal patterns, and fine pores are formed between the grains. However, there was no similar phenomenon at the interface of Cu (220)-Sn. The preferential nucleation of Cu _ 3SN and the interface of Cu _ (220)-Cu6Sn5 existed at the grain boundary. A thin sheet IMCs, of the same thickness was formed at the interface of Ni _ (220)-Sn. IMCs at the interface of Ni _ (200)-Sn is equiaxed and the grain size is uniform. When the atomic ratio of Ni/Sn in the flake IMCs of Ni _ (200)-Sn interface is greater than that at the interface of Ni _ (200)-Sn, the aging reaction of IMCs, is fully carried out. The ratio of Ni/Sn atoms in the two kinds of IMCs changed to 3? 4, that is, the common nickel-tin intermetallic compound Ni3Sn4. was formed. Over a long period of time, the IMCs layer continues to grow, constantly consuming the tin coating in the middle to form large intermetallic compounds, and can even consume differentiated Sn layers that run through the entire interface. At the same time, holes and cracks appear in the loose structure of IMCs at the interface of Ni (220)-Sn, which will affect the mechanical and electrical properties of the bonding interface.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ153
[Abstract]:With the development of micro-electronic products to high density, narrow spacing and short path, the size of interconnect solder joint used in 3D laminated packaging also decreases significantly. Due to its good mechanical and electrical properties, copper bump is considered to be a substitute for traditional solder ball micro-bumps, which can be used in high-density packaging technology with the aspect ratio of detail distance to depth. Under the condition of miniaturization, the crystal orientation of a single convex point has a more and more obvious effect on the interfacial reaction and the nucleation and growth of intermetallic compounds at the interface are greatly affected by the decrease of the grain content in the single convex point. At present, the research on the effect of crystallographic orientation on bonding interface reaction is mostly based on single crystal substrate. However, the fabrication of single crystal substrate is not easy and the cost is high. In practical application, polycrystalline convex points should be deposited by electrodeposition. Therefore, it is of great significance to clarify the effect of electrodeposition process parameters on the preferred orientation of the coating and the effect of the coating texture on the growth of intermetallic compounds at the interface. In this paper, the effects of bath additives, current density and pulse plating on the orientation selection of thin films were investigated. Copper and nickel films with two different preferred orientations were prepared by electrodeposition. The interfacial reactions of copper and tin and nickel and tin with different preferred orientations were observed and studied. The effect of crystallographic preferred orientation on the growth of intermetallic compounds was systematically studied. In the process of electrodeposition, copper and nickel films with specific orientation can be obtained by controlling the electrodeposition conditions such as additive, current density, power supply type and so on. The preferred orientation of copper film was (220). With the increase of current density, the preferred orientation of nickel films changed from (111) to (200). The (200) crystal plane of nickel thin film exhibits obvious preferred orientation under DC condition, and the (111) crystal plane begins to show a certain degree of preference under pulse condition. The diffusion coefficients of atoms in different crystal planes are different. When the orientation of the coating is preferred, the diffusion of atoms in the coating also shows anisotropy. In addition, compared with solid-liquid reaction (reflux), it is the diffusion rate of the reaction atom that determines the reaction rate (aging) and morphology of the solid-solid interface reaction. Because the diffusion rates of atoms are anisotropic, they have different diffusion rates in coatings with different preferred orientations. As a result, the morphology and growth rate of the interface reaction products are affected. (200) the arrangement of atoms on the crystal plane is more dense than that on the (220) plane, so the diffusion of atoms on the (200) crystal plane is more difficult. The diffusivity is smaller than that on the (220) crystal plane. There are obvious small facets in the IMCs grain at the Cu (200)-Sn interface, which are arranged at different angles to form polygonal patterns, and fine pores are formed between the grains. However, there was no similar phenomenon at the interface of Cu (220)-Sn. The preferential nucleation of Cu _ 3SN and the interface of Cu _ (220)-Cu6Sn5 existed at the grain boundary. A thin sheet IMCs, of the same thickness was formed at the interface of Ni _ (220)-Sn. IMCs at the interface of Ni _ (200)-Sn is equiaxed and the grain size is uniform. When the atomic ratio of Ni/Sn in the flake IMCs of Ni _ (200)-Sn interface is greater than that at the interface of Ni _ (200)-Sn, the aging reaction of IMCs, is fully carried out. The ratio of Ni/Sn atoms in the two kinds of IMCs changed to 3? 4, that is, the common nickel-tin intermetallic compound Ni3Sn4. was formed. Over a long period of time, the IMCs layer continues to grow, constantly consuming the tin coating in the middle to form large intermetallic compounds, and can even consume differentiated Sn layers that run through the entire interface. At the same time, holes and cracks appear in the loose structure of IMCs at the interface of Ni (220)-Sn, which will affect the mechanical and electrical properties of the bonding interface.
【学位授予单位】：上海交通大学
【学位级别】：硕士
【学位授予年份】：2015
【分类号】：TQ153
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