Formation of solid-solution Cu-to-Cu joints using Ga solder and Pt under bump metallurgy for three-dimensional integrated circuits

Shih kang Lin, Hao miao Chang, Cheng liang Cho, Yu chen Liu, Yi kai Kuo

Research output: Contribution to journalArticle

17 Citations (Scopus)

Abstract

Three-dimensional (3D) integrated circuits (ICs) are the most important packaging technology for next-generation semiconductors. Cu-to-Cu throughsilicon via interconnections with micro-bumps are key components in the fabrication of 3D ICs. However, significant reliability concerns have been raised due to the formation of brittle intermetallic compounds in the entire 3D IC joints. This study proposes a Ga-based Cu-to-Cu bonding technology with Pt under bump metallurgy (UBM). A systematic analysis of reactive wetting between Ga solders and polycrystalline, single-crystalline, and Ptcoated Cu substrates was conducted. Pt UBM as a wetting layer was identified to be a key component for Ga-based Cu-to-Cu bonding. Pt-coated Cu substrates were bonded using Ga solders with various Ga-to-Pt ratios (n) at 300℃. When n ≥ 4, the Cu/Pt/Ga/Pt/Cu interface evolves to Cu/facecentered cubic (fcc)/γ1-Cu9Ga4/fcc/Cu, Cu/fcc/γ1-Cu9Ga4 + Ga7Pt3/fcc/Cu, and finally Cu/fcc + Ga7Pt3/Cu structures. The desired ductile solid solution joint formed with discrete Ga7Pt3 precipitates. When n ≤ 1, a Cu/Ga7Pt3/Cu joint formed without Cu actively participating in the reactions. The reaction mechanism and microstructure evolution were elaborated with the aid of CALPHAD thermodynamic modeling.[Figure not available: see fulltext.]

Original languageEnglish
Pages (from-to)687-694
Number of pages8
JournalElectronic Materials Letters
Volume11
Issue number4
DOIs
Publication statusPublished - 2015 Jul 25

All Science Journal Classification (ASJC) codes

  • Electronic, Optical and Magnetic Materials

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