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功率器件或大规模集成电路中,当电流密度达1×10~6A/cm~2时,电迁移将引起铝金属化层开路失效。 电迁移是在外加直流电场作用下,金属离子和导电电子间的动量交换导致前者热激活而引起的质量传输。理论上通常用离子流和离子流散度描述电迁移过程。工程上大多通过直流加载的寿命试验研究电迁移现象。Blcak通过合理的假设得到了理论与工程相结合的电迁移公式:MTF~(-1)=Aj~2exp(—Q/KT)。Black的试验结果还证实了电迁移属于晶界扩散机理。 文章综述了寿命试验中加载方式的影响,举例说明了怎样预计寿命值和估算失效率,最后提到了防止电迁移失效的措施。 鉴于铝具有高导电率,与硅和二氧化硅有良好的附着性能,与N型硅、P型硅均可形成低阻欧姆接触以及适合于大规模集成电路多层布线等优点,硅器件金属化工艺中铝材得到了广泛的应用。纯铝的金属化层在使用中也暴露出一些弱点。比如,当电流密度较高,如达到1×10~6A/cm~2 时容易发生电迁移现象,当温度高于400℃时发生铝硅反应等。 随着集成电路微型化,金属化层布线密度增加,其截面积显著缩小(1—2×10~(-6)cm~2),流经铝膜的电流密度有可能达到10~6A/cm~2或更高,因此,研究金属化层的电迁移问题具有重要意义。
In power devices or LSIs, when the current density reaches 1 × 10 -6 A / cm 2, electromigration will cause the failure of the aluminum metallization layer to open. Electromigration is the mass transfer caused by the thermal activation of the former due to the exchange of momentum between metal ions and conductive electrons under the action of an applied DC electric field. In theory, ion mobility and ion mobility are commonly used to describe the electromigration process. Most projects through the life of the DC load test to study the electromigration phenomenon. Blcak obtained theoretical and engineering electromigration equations through reasonable assumptions: MTF ~ (-1) = Aj ~ 2exp (-Q / KT). Black’s experimental results also confirmed that electromigration belongs to the grain boundary diffusion mechanism. This paper summarizes the influence of loading method in life test, and gives an example of how to predict the life value and estimate the failure rate. Finally, the measures to prevent the failure of electromigration are mentioned. In view of the high conductivity of aluminum, good adhesion with silicon and silicon dioxide, it can form low-resistance ohmic contacts with N-type silicon and P-type silicon, and is suitable for multi-layer wiring of large scale integrated circuits. The silicon device metal Aluminum technology has been widely used. Pure aluminum metallization also exposed some weaknesses in use. For example, when the current density is high, electromigration occurs easily when it reaches 1 × 10 -6 A / cm 2 and aluminum-silicon reaction occurs when the temperature is higher than 400 ° C. With the miniaturization of integrated circuits, the wiring density of the metallization layer increases and its cross-sectional area is significantly reduced (1-2 × 10 -6 cm 2). The current density flowing through the aluminum film is likely to reach 10-6A / cm ~ 2 or higher. Therefore, it is of great importance to study the electromigration of metallized layers.