Ultra-low-resistivity-silicon (ULRS) coaxial through-silicon-vias (TSVs) employ silicon pillar as the central conductor, which simplifies the fabrication process and exhibits good electrical characteristics. However, microcracks that may appear on silicon pillars degrade the reliability and electrical properties. In this work, the main cause of microcracks is investigated experimentally and an optimized fabrication process is proposed to avoid microcracks, which includes a two-step chemical mechanical polishing for frontside Benzocyclobutene overburden layer removal and a two-step backside TSVs reveal process featuring mechanical grinding with a safety margin followed by chemical mechanical polishing. Utilizing the proposed method, crack-free ULRS coaxial TSVs were successfully fabricated. In addition, the electrical properties of TSVs including ${I}$ - ${V}$ curves and ${S}$ -parameters were characterized under various temperatures, and the results demonstrates that the coaxial TSVs exhibit good impedance matching and low insertion loss up to 50 GHz even under 125°C.

中文翻译：

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同轴超低电阻硅通孔的无裂纹制造和电气特性

超低电阻率硅 (ULRS) 同轴硅通孔 (TSV) 采用硅柱作为中心导体，简化了制造工艺并表现出良好的电气特性。然而，硅柱上可能出现的微裂纹会降低可靠性和电气特性。在这项工作中，通过实验研究了微裂纹的主要原因，并提出了一种优化的制造工艺以避免微裂纹，其中包括用于去除正面苯并环丁烯覆盖层的两步化学机械抛光和以机械研磨为特征的两步背面 TSV 显示工艺具有安全裕度，然后进行化学机械抛光。利用所提出的方法，成功地制造了无裂纹的 ULRS 同轴 TSV。此外，TSV 的电气特性包括 ${I}$ —— ${V}$ 曲线和 ${S}$ 参数在各种温度下进行表征，结果表明同轴 TSV 表现出良好的阻抗匹配和低插入损耗，即使在 125°C 下也高达 50 GHz。