Conductivity of high-temperature annealed silicon direct wafer bonds

Electrical, Mechanical, and Hermetic Properties of Low-Temperature, Plasma Activated Direct Silicon Bonded Joints

“…The calculated resistance of the bulk silicon in the dies was between 15 and 96 m , which is significantly lower than the measured resistances of 2.2 . The current density of 1.1 × 10 4 A/m 2 in F200 dies at 50 mV was significantly lower than the 15 This difference does indicate that the current is restricted across the bonded interface produced by the plasma activated direct bonding method presented in this paper.…”

“…The current density of 1.1 × 10 4 A/m 2 in F200 dies at 50 mV was significantly lower than the current densities of 4.0-6.2 × 10 4 A/m 2 obtained on high-temperature annealed Si directly bonded dies. 15 This difference does indicate that the current is restricted across the bonded interface produced by the plasma activated direct bonding method presented in this paper. The linear, ohmic behavior observed on the dies in the current study is in contrast to the non-linear I-V curve reported by Amirfeiz et al and by Raeissi et al 11,12 The reason for the discrepancy is unknown, but it could be related to differences in silicon surface activation process, or to differences in sample preparation.…”

“…7 The capacitance values obtained in the current study are highly different from capacitance values obtained in similarly shaped test dies, bonded by high-temperature annealed direct silicon (fusion) bonding. 15 Fusion bonded samples made from bonding Si wafers without thermal SiO 2 had ohmic behavior and no measureable capacitance when measured after bond anneal. 15 In contrast, samples fabricated by bonding a Si wafer with a 60 nm thick thermal SiO 2 to a wafer with no thermal SiO 2 exposed the expected 574 pF/mm 2 .…”

“…15 Fusion bonded samples made from bonding Si wafers without thermal SiO 2 had ohmic behavior and no measureable capacitance when measured after bond anneal. 15 In contrast, samples fabricated by bonding a Si wafer with a 60 nm thick thermal SiO 2 to a wafer with no thermal SiO 2 exposed the expected 574 pF/mm 2 . This result suggests that the electrical properties of the bonded interface is different for interfaces formed by Si-Si fusion bonding and plasma bonding.…”