Direct Bonding Mechanism of ALD-Al₂O₃Thin Films

Abstract

Direct bonding mechanism of amorphous ALD alumina has been investigated from room temperature up to 1200 • C. By considering the evolution with temperature of free alumina surfaces and bonded configuration we highlight strong interaction between oxidant species and defect generation through interfacial oxidation. In the first case, the combination of internal stress and adhesion loss by dry O 2 oxidation results in blister formations, whereas in the case of bonding structures, wet oxidation with H 2 production at Silicon-Alumina interfaces explains void formation. Based on these established mechanisms we provide insights on alumina layer integration within a large temperature range. © The Author Direct bonding is used to join two mirror-polished wafers without any additional material. This technique has proven to be a powerful assembly strategy and found extensive application in microelectronics, MEMS and optoelectronic device fabrication. In particular, direct bonding has enabled the emergence of Silicon-On-Insulator (SOI) based technologies. For many reasons including processing convenience, good electrical and thermo-mechanical behavior, SiO 2 appeared from the beginning as an ideal candidate as buried insulating material and also for as bonding material. SiO 2 SOI structures promote many advantages such as the improvement of device switching speed and power consumption or even parasitic capacitance. Recently, with device scale reduction, SiO 2 material has shown some limitations such as notable leakage current or self-heating that affects next generation devices. In this context, one possible alternative would be the replacement of SiO 2 by a better candidate.1-3 The consideration of the comprise between thermal and electrical properties has already pointed out different materials such as diamond, Al 2 O 3 , HfO 2 or Si 3 N 4 .1 Among these materials, alumina thin film appears as a credible candidate replacement of buried SiO 2 with suitable electrical (ρ = 10 12 -10 14 .cm) and thermal (thermal conductivity = 0.3-30 W.m −1 .K −1 ) properties. In addition, bonding feasibility was already demonstrated in the past. [4][5][6][7] Recently with the emergence of III-V-OI substrates at low bonding temperature, ALD-Al 2 O 3 thin film found new outlooks. Indeed the improvement of interface quality between III-V substrates and ALD-Al 2 O 3 layers in comparison with SiO 2 layer (lower interface roughness) results in better performance in specific configuration. 8,9 Moreover, direct wafer bonding using the high-k dielectric material provides a better mechanical assembly, much stronger than deposited SiO 2 within the low temperature range.10,11 Nevertheless recent works pointed out numerous defect generations at higher thermal required for other devices and integration scheme typically T ≤ 600• C. 12,13 The defect apparition, and resulting debonding, alters its fabrication and its performance. In this paper we focus on these defects within a wide temperature range [RT to 1200• C]. We conduct a comparative analysis betwee...

Blistering mechanisms of atomic-layer-deposited AlN and Al2O3 films

“…Blistering in films grown by atomic layer deposition (ALD) takes place for various substrate-film combinations [1][2][3] and is typically observed after high-temperature treatments. 4 Blisters are generally treated as reliability risks as they create mechanically weak spots in protective and structural coatings 5 but can be also exploited in rear semiconductor-metal contact formation of passivated solar cells. 6 Most studies regarding blistering of ALD films deal with Al 2 O 3 as it is one of the most thoroughly characterized ALD material and since it provides excellent passivation of Si-based solar cells.…”

InGaAs-OI Substrate Fabrication on a 300 mm Wafer

“…This optimization allows us to substantially reduce the thickness of the dielectric capping layer, which is used to reduce the surface roughness by using a well-known CMP process on this material. The study of the direct bonding interface quality was done in terms of annealing temperatures [8].…”

“…All the bonding conditions present no defects up to 400 • C, except the Al 2 O 3 /Si bonding, which is already defective. At over 400 • C, only the last stack (with the SiO 2 //SiO 2 bonding configuration) presented good performance in temperature without bonding defects up to 600 • C. This configuration avoids the diffusion of bonding interface water at the Al 2 O 3 //Si interfaces, which are known to be weak and easily defectives [8,9]. This deposited SiO 2 layer is essential in the bonding process for two reasons: it can be easily polished to allow the DWB, and it allows the best bonding condition, but a pre-annealing before bonding (at 600 • C) is necessary to avoid defect at 600 • C after bonding [5].…”

“…At over 400 °C, only the last stack (with the SiO2//SiO2 bonding configuration) presented good performance in temperature without bonding defects up to 600 °C. This configuration avoids the diffusion of bonding interface water at the Al2O3//Si interfaces, which are known to be weak and easily defectives [8,9].…”

Structure and Surface Morphology Effect on the Cytotoxicity of [Al2O3/ZnO]n/316L SS Nanolaminates Growth by Atomic Layer Deposition (ALD)

“…To obtain the Al 2 O 3 layer, cycles of 150 ms TMA dose, 750 ms N 2 purge, and 150 ms DI water dose were introduced into the chamber, and then 500 ms N 2 purge for the vacuum process. The chemical reactions with the TMA follow the Equation (1) [25,26]. Afterward, UHP N 2 purge the chamber before starting another cycle.…”