High Temperature Thermal Conductivity of Amorphous Al₂O₃ Thin Films Grown by Low Temperature ALD

Abstract

grown by atomic layer deposition could be proposed as a nonactive layer for back end processes in view of the integration of scaled phase change memory devices. In this paper we report on thermal characterization from 50 to 600°C of amorphous Al 2 O 3 thin films grown on thermally oxidized silicon substrate at a temperature of 100°C and capped with a 30 nm thick Pt layer. The effects of low temperature deposition and of a post-deposition rapid thermal annealing process (RTP) on the thermal properties of the films are investigated using a modulated photo-thermal radiometry technique coupled with post-annealing morphological characterizations. Degassing process occurring at high temperature greatly affects the film surface quality, though measurements of the films after RTP show that the thermal conductivity of amorphous Al 2 O 3 increases as a function of temperature from 1.8 W K À1 m À1 at 50°C to 3.3 W K À1 m À1 at 600°C. At the same time, the value of the thermal boundary resistance at the Pt-Al 2 O 3 interface decreases from 1.02 Â 10 À7 K m 2 W À1 at 50°C to 4.8 Â 10 À8 K m 2 W À1 at 600°C.

Influence of a Nanometric Al2O3 Interlayer on the Thermal Conductance of an Al/(Si, Diamond) Interface

“…Measured thermal conductivities shown in Figure a for both the Al/Al 2 O 3 /C and Al/Al 2 O 3 /Si systems indicate that the data can be separated into two classes: at temperatures above 140 K, data fall approximately midway between measurements made by Lee et al and agree reasonably with each other. The obtained data also compare well with measurements on amorphous alumina produced by anodization, as well as other data on ALD deposited thin films extrapolated to lower temperature below 140 K, values start to vary substantially.…”

“…It is further successfully used to encapsulate organic electronic devices and is expected to help improve the lifetime of Li‐ion batteries . While much effort has been put into describing its electric, mechanical, chemical, and diffusion properties of ALD alumina, only little effort has been made to characterize its thermal properties . This knowledge could be relevant because the miniaturization of microelectronics increases significantly the criticality of thermal management.…”

Thickness-dependent thermal properties of amorphous insulating thin films measured by photoreflectance microscopy

“…It has therefore received a lot of attention, and its thermal properties are relatively well known. Some research groups have studied the thermal conductivity of Al 2 O 3 amorphous thin films [8][9][10][11], but the evaluation of their interfacial thermal resistances is still very incomplete [12]. Al 2 O 3 amorphous thin films are promising, since they can reduce electronic recombination losses in solar cells by the passivation of silicon surfaces, thus enabling higher efficiency [13].…”

Significant Phonon Drag Enables High Power Factor in the AlGaN/GaN Two-Dimensional Electron Gas

“…We used a thermal boundary resistance of 2.8 10 -8 m 2 K W -1 for mox . 7 Although an experimental determination of the thermal boundary resistance across the Al2O3/GaN film interface is not available, we estimated oxg ≈ 1 10 -8 m 2 KW -1 based on measurements across amorphous dielectric/Si interfaces, 8 since GaN and Si have similar Debye temperatures. 9 The thermal resistance of the alumina layer can be estimated as ox = ox /( ox H ) , where ox is the temperature dependent thermal conductivity of the alumina layer.…”

“…[2][3][4] Momentum transfer from non-equilibrium phonons to charge carriers, known as phonon drag (PD), produces a Seebeck coefficient ( ph ) that adds to the Seebeck coefficient from the thermal diffusion of charge carriers ( d ). Despite the potential gains in TE efficiency, understanding the contribution of PD to the overall Seebeck coefficient has not received much consideration, largely due to early work which suggested that: (1) ph is only significant at low temperatures (T ≤ 50 K), where the TE power conversion efficiency ( ) is low; 5 (2) ph is small relative to d for degenerate semiconductors, 6,7 which are the most common TE materials due to their larger ; and (3) an increase in ph coincides with a corresponding increase the thermal conductivity ( ), [8][9][10] and thus has little benefit for power generation, because ∝ 2 / .…”