Surface activated bonding of ALD Al₂O₃ films

Abstract

Room temperature direct bonding of plasma enhanced ALD Al2O3 films was achieved by using surface activated bonding (SAB). ALD Al2O3 films was amorphous with C and O impurities contained. The high deposition power and H2 plasma post-treatment increased the crystallinity and hydrophilicity of ALD Al2O3 films, respectively. However, both methods increased the surface roughness of films slightly. The bond strength of ALD Al2O3 films was not changed obviously by raising the deposition power, but it experienced a slight decrease after H2 plasma post-treatment. The water in the debonding atmosphere influenced the bond strength of standard ALD Al2O3 films greatly, which was 0.54 J/m2 in humid air and 1.00 J/m2 in anhydrous N2. The bond strength in vacuum was just a little larger than that in anhydrous N2 suggesting that the trapped water at the bonding interface was less.

Effect of oxidant sources on carbon-related impurities in ALD-Al2O3 for solid-state devices

“…[11][12][13] Furthermore, ALD-Al 2 O 3 is also used in advanced packaging such as surface-activated bonding (SAB) of heterogeneous wafers due to the thickness controllability for nano-adhesion layers and relatively high thermal conductivity. [14][15][16][17][18][19] For SAB, bond strength is degraded by defects due to the reduction in binding species such as -OH groups. We have previously reported that the -OH groups in the ALD-Al 2 O 3 films were decreased by changing the oxidant source from H 2 O vapor to O 2 plasma.…”

“…This trend was in agreement with the results of a previous study using O 2 plasma-Al 2 O 3 . 14) It is considered that the decomposition of -CH 3 groups was enhanced by O 2 plasma, and C-O residue was generated. 33) Moreover, the peak of O-H bonds observed at ∼1100 cm −134) was significantly reduced by O 2 plasma [Fig.…”