【作者】 李娜；

【导师】 黄明亮；

【作者基本信息】 大连理工大学 ， 材料学， 2024， 硕士

【摘要】 晶圆级Sn-(1.5～2.1)wt.%Ag微凸点是集成电路封装中芯片互连的关键材料,随着芯片互连尺寸的不断减小,电镀法作为制备微凸点主要手段,可实现精准沉积特定尺寸和节距的微凸点。然而,目前电镀法制备晶圆级Sn-Ag微凸点技术主要被美国和日本等企业垄断,是集成电路制造中的一项“卡脖子”技术。本论文采用共沉积电镀法,通过稳定性实验、电镀实验、电化学测试手段研究了络合剂的络合作用和添加剂的抑制作用的作用机制,开发出一种高稳定性的共沉积Sn-Ag合金电镀液,实现高平整性Sn-(1.5～2.1)wt.%Ag合金微凸点的制备。本论文主要结论如下:1.研究了甲基磺酸体系Sn-Ag合金电镀液五种络合剂的络合能力与电镀液稳定性的关系。五种络合剂均可使Ag(Ⅰ)沉积电位发生不同程度的负移,络合剂C和L-半胱氨酸可使Ag(Ⅰ)的沉积电位负移至Sn(Ⅱ)附近。同时含络合剂C和L-半胱氨酸的电镀液可在180天保持澄清透明;电流密度使用范围广,在4～8 ASD电流密度下可获得平整致密、晶粒细小的镀层。筛选了络合剂C和L-半胱氨酸作为甲基磺酸体系Sn-Ag合金电镀液的络合剂。2.阐明了三类添加剂对Sn-Ag合金电镀液极化行为的影响规律和相互作用机制。主光亮剂C可显著提高镀层光亮度并增大镀层结合力,辅助光亮剂F可极大增大电镀液极化行为,分散剂G能通过胶束增溶作用促进光亮剂的吸附抑制作用。三种添加剂共同存在时可以显著提高电镀液的极化能力,提高镀层光亮度。筛选了添加剂C、添加剂F和添加剂G组合为Sn-Ag合金电镀液的添加剂。3.研究了Sn-Ag合金电镀液中不同组分对电镀液极化行为、凸点镀层形貌和成分的影响规律。甲基磺酸浓度越高镀层越易倾斜,但对成分影响较小;甲基磺酸亚锡和甲基磺酸银的浓度决定了凸点镀层的成分;络合剂C和L-半胱氨酸与Ag(Ⅰ)的浓度比分别为1:2和3.75:1时,凸点镀层的晶粒细小,平整性高,但络合剂浓度过高时未参与络合的分子游离在电镀液中,影响电镀液的分散能力和深镀能力,从而降低凸点镀层质量。4.研究了三种添加剂的浓度对凸点镀层形貌和平整度的影响规律,优化了Sn-Ag合金电镀液的组成。添加剂C可显著整平凸点镀层,添加剂F可提高电镀液的分散能力,改善镀层中高电流密度区的平整性,分散剂G对凸点镀层形貌影响较小。经优化后的Sn-Ag合金电镀液可在4和8 ASD电流密度下电镀获得细小晶粒表面平整的凸点镀层。回流后可形成无空洞的致密半球状凸点,微凸点的成分为Sn-(1.5～2.1)wt.%Ag。更多还原

【Abstract】 Wafer level Sn-(1.5-2.1)wt.% Ag alloy micro bumps are key materials for chip interconnection in integrated circuit packaging.With the continuous reduction of chip interconnection size,electroplating method is the main method for preparing micro bumps,which can achieve precise deposition of micro bumps of specific size and pitch.However,the current electroplating method for preparing wafer level Sn-Ag micro bumps is mainly monopolized by companies such as the United States and Japan,and is a bottleneck technology in integrated circuit manufacturing.This paper adopts the co-deposition electroplating method to study the complexing effect of complexing agents and the inhibition mechanism of additives through stability experiments,electroplating experiments,and electrochemical testing methods.A highly stable co-deposition Sn-Ag alloy electroplating solution is developed to achieve the preparation of high flatness Sn-(1.5-2.1)wt.% Ag alloy micro bumps.The main conclusions of this paper are as follows:1.The relationship between the complexing ability of five complexing agents and the stability of the Sn-Ag alloy electroplating solution in the methylsulfonic acid system was elucidated.All five complexing agents can cause a negative shift in the deposition potential of Ag(I)to varying degrees,while complexing agents C and L-cysteine can cause the deposition potential of Ag(I)to move negatively to the vicinity of Sn(II).The electroplating solution containing both complexing agent C and L-cysteine can remain clear and transparent for 180days;The current density has a wide range of applications,and a flat,dense,and fine-grained micro bumps can be obtained within 4-8 ASD.The complexing agents C and L-cysteine were selected as the complexing agents for the Sn-Ag alloy electroplating solution in the methylsulfonic acid system.2.The influence and interaction mechanism of three types of additives on the polarization behavior of Sn-Ag alloy electroplating solution were elucidated.The main brightener additive C can significantly improve the brightness of the micro bumps and increase the adhesion of the micro bumps.The auxiliary brightener additive F can greatly increase the polarization behavior of the plating solution.The dispersant additive G can promote the adsorption inhibition of the brightener through micelle solubilization.However,the presence of three additives is necessary to significantly improve the polarization ability of the electroplating solution and enhance the brightness of the micro bumps.The combination of additive C,additive F,and additive G was selected as the additive for Sn-Ag alloy electroplating solution.3.The influence of different components in Sn-Ag alloy electroplating solution on the polarization behavior,morphology,and composition of the micro bumps was elucidated.The higher the concentration of methylsulfonic acid,the worse the quality of the coating,but the effect on the composition of the micro bumps is relatively small;The concentration of stannous methanesulfonate and silver methanesulfonate determines the composition of the micro bumps;When the concentration ratios of complexing agents C and L-cysteine to Ag(I)are 1:2 and3.75:1,respectively,the morphology of the micro bumps is optimal.However,when the concentration of complexing agents is too high,molecules that do not participate in the complexation free up in the plating solution,affecting the dispersion and deep plating ability of the plating solution,thereby reducing the quality of the micro bumps.4.The influence of the concentration of three additives on the morphology and flatness of micro bumps was elucidated,and the composition of Sn Ag alloy electroplating solution was optimized.Additive C can significantly flatten the micro bumps,while additive F can improve the dispersion ability of the plating solution and improve the flatness of the high current density area in the micro bumps.The dispersant has little effect on the morphology of the micro bumps.The optimized Sn Ag alloy electroplating solution can obtain a smooth micro bumps with fine grain surface on 4 and 8 ASD electroplating.After reflow,dense hemispherical protrusions can be formed without defects,and the composition of the protrusions meets the requirements for micro protrusions of Sn-(1.5-2.1)wt.% Ag.更多还原