Li Intercalation in Tl2Ba2CuO6+δ Superconductor and Effective Charge of Migrating Li Ion

Abstract

Li intercalation into Tl₂Ba₂CuO_6+δ Superconductor was shown to decrease doping level, leading to T_C increase for this overdoped material. By studying redistribution of intercalated atoms under flow of longitudinal electrical current, effective charge of migrating Li ion was determined as 1.1±0.3.     

Roughness and texture correlation of Al films

Titanium films prepared by standard direct-current (DC) magnetron physical vapor deposition (PVD) and ionized metal plasma PVD (I-PVD), with Al (0.5wt.%Cu) films on them, were studied. The surface roughness, reflectivity, and crystalline texture of Ti on SiO₂/Si and Al on TiN/Ti/SiO₂/Si were investigated with the same thickness of Al, TiN, and Ti. The surface roughness of Al films with Ti/TiN underlayers was found to be capable of monitoring Al(111) texture. So, the reflectivity of Al/TiN/Ti film stack can be used as a quick monitor for the electromigration (EM) lifetime.     

Combined low-frequency noise and resistance measurements for void extraction in deep-submicrometer interconnects

Electromigration stress can give rise to voids that increase the resistance and localized thermal stress in interconnects. Estimation of the extent of voiding can provide information on the material quality and the amount of degradation that has resulted from the electrical stress. In this paper, a model is proposed that can be used to estimate the effective void volume in deep-submicrometer interconnects. The model uses a combination of low-frequency noise and resistance measurements, and also considers the thermal coefficient of resistance in calculating the change in resistance of the interconnect line. A deconvolution scheme was employed to extract the 1/f noise component from the noise-measurements to improve the accuracy of the extraction algorithm. To verify the accuracy of the model, the focused ion beam (FIB) technique was used to mill holes (to simulate voids) of known dimensions. The model was further applied to an electromigration stress study of aluminum (Al) interconnects as a method of testing its validity for stress-induced voids. The proposed technique is a useful reliability tool for void detection in deep-submicrometer interconnects.     

SnAgCu焊点电迁移诱发IMC阴极异常堆积

为了研究电迁移过程中焊点与焊盘界面金属问化合物(IMC)的变化,在28℃下,对无铅Sn3.0Ag0.5Cu焊点进行了6.5A直流电下的电迁移实验.结果发现,通电144h后,阳极侧IMC层变厚,平均达到10.12 μm;阴极侧IMC层大部分区域变薄至0.86μm,局部出现Cu焊盘的溶解消失,但在界面边缘处出现Cu3Sn5...     

电流密度对Sn3.0Ag0.5Cu焊点蠕变行为的影响

通过观察焊点的电阻变化和显微组织演变,研究了电流密度对Sn3.0Ag0.5Cu焊点蠕变行为的影响。结果表明:焊点在低电流密度条件下蠕变时,其电阻波动大、寿命长,失效机制由蠕变过程主导,损伤逐渐累积导致最终失效;焊点在高电流密度条件下蠕变时,其电阻波动小、寿命短,电迁移作用缓解了焊点的初期蠕变损伤,但是加速了焊点后期脆性断裂失效。     

基于电迁移法的铝微米带弯曲生长现象研究

基于电迁移法制备了弯曲形状的铝微米带,可作为连接件直接应用于微机电系统和光电器件中。试验所需试样是一层沉积在TiN层的铝膜,并在铝膜的阳极端制作原子排出孔。试验结果表明,铝微米带的生长驱动力来自于铝原子积聚产生的压应力,排出孔的位置靠近铝膜边缘,使铝原子在排出孔两侧的析出速率出现差异,导致铝微米带出现自发弯曲生长现象。     

W-Plug通孔电迁移研究

We analyze the failure mechanism of W-plug via electromigration made in a 0.5-μm CMOS SPTM process. Failure occurs at the top or bottom of a W-plug via. We design a series of via chains, whose size ranges from 0.35 to 0.55μm. The structure for the via electromigration test is a long via chain, and the layer in the via is Ti/TiN/W/TiN. Using a self-heated resistor to raise the temperature of the via chain allows the structure to be stressed at lower current densities, which does not cause significant joule heating in the plugs. This reduces the interaction between the plug and the plug contact resistance and the time-to-failure for the via chain. The lifetime of a W-plug via electromigration is on the order of 3×10^7S, i.e., far below the lifetime of metal electromigration. The study on W-plug via electromigraion in this paper is beneficial for wafer level reliability monitoring of the ultra-deep submicron CMOS multilayer metal interconnect process.     

多晶硅加热法评价金属互连线电迁移寿命

采用一种新颖的方法——多晶硅加热法评价了金属连线的电迁移（EM）寿命．用该方法得到的结果与传统封装测试法得到的结果进行了对比，两者有相当好的一致性．同时，测试时间不到封装测试的1‰．说明多晶硅加热法是一种非常有效的EM评价方法．由于该方法是晶片级测试，而且测试时间非常短，所以采用这种方法可以实现对金属互连线质量的在线实时监控．     

The Al/Ni interfacial reactions under the influence of electric current

Electromigration has been observed and quite extensively investigated in the compositionally homogeneous conducting lines in the integrated circuit devices; however, the effect of electric current upon the interfacial reactions has not been discussed. This study investigated the effect of electric current upon the chemically driven interfacial reactions in the Al/Ni system. Al/Ni reaction couples annealed at 400°C with and without the passing of electric current were examined. Two intensities of electric currents, 5×10² A/cm² and 10³ A/cm², were used in this study. Same intermetallics, Al₃Ni and Al₃Ni₂, were formed at the interfaces; however, the thickness of the reaction layer in the reaction couples with the passing of electric current was much larger than those without electric current. This novel phenomenon has never been reported in the literature, and the understanding of its mechanism needs further investigation.     

Curing of polyimide and the effect of the TEOS SiO2 barrier layer on the electromigration of sputtered Cu with polyimide passivation

The curing process of polyimide and the electromigration of copper films with polyimide (PI) passivation are studied. Thermal analysis of polyimide suggests that imidization completes at ∼200°C with an endothermic reaction associated with the breaking of the C-OH and N-H bonds as revealed by Fourier transformation infrared spectroscopy (FTIR). Although there is 89.8% weight loss when PI is heated from 20°C to 200°C, outgassing of PI passivation is still observed at higher temperatures. Carbon, nitrogen, and oxygen atoms diffuse into Cu during thermal processing of PI/Cu films. The tetraethyl orthosilicate (TEOS) SiO₂ films are used as the barrier layer between PI and Cu to retard the poisoning of Cu. The effect of TEOS SiO₂ film on electromigration of Cu is investigated.