Study of a Flow Modulation CVD (FM-CVD) process at about 400°C for AlN growth as high thermal conductive insulating films in 3DICs and Chiplets

It is essential to shift from two-dimensional miniaturization to three-dimensional integrated circuits (3DICs) to realize high performances and high functionalities. However, 3DICs also increase the heat-generation density and are prone to high operating temperatures, which degrade device performance and reliability. Therefore, to establish the thermal management of 3DICs, the insulation layer should be changed from SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, which has low thermal conductivity, to AlN, which has high thermal conductivity. These AlN films are used in the sidewalls of through-silicon vias (TSVs) and molding. AlN films are formed after the chip process; therefore, the thermal budget is sufficiently severe to be below 400°C. This study aims to establish a Chemical Vapor Deposition (CVD) process capable of depositing high-quality AlN films at temperatures below 400°C using a Flow-Modulation (FM) technique to realize low-temperature AlN film deposition. In FMCVD, precursor adsorption, reaction, and surface diffusion are promoted by the intermittent supply of precursors, making it possible to synthesize high-quality thin films at low temperatures. As a result, we showed that an AlN film with a thermal conductivity of 3.9 W/mK, which is three times the theoretical value of existing SiO<inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf>, was grown at 400°C at a high growth rate and uniformity of 2.0nm/min or more and a step coverage of 81% or more at an aspect ratio (AR) of 30.