Three-dimensional (3D) CMOS technology encourages the use of UV laser annealing (UV-LA) because the shallow absorption of UV light into materials and the process timescale typically from nanoseconds (ns) to microseconds (µs) strongly limit the vertical heat diffusion. In this work, µs UV-LA solid phase epitaxial regrowth (SPER) demonstrated an active carrier concentration surpassing 1 × 1021 at./cm3 in an arsenic ion-implanted silicon-on-insulator substrate. After the subsequent ns UV-LA known for improving CMOS interconnect, only a slight (⁓5%) sheet resistance increase was observed. The results open a possibility to integrate UV-LA at different stages of 3D-stacked CMOS.

UV nanosecond pulsed laser annealing (UV NLA) enables both surface-localized heating and short timescale high temperature processing, which can be advantageous to reduce metal line resistance by enlarging metal grains in lines or in thin films, while maintaining the integrity and performance of surrounding structures. In this work UV NLA is applied on a typical Cu thin film, demonstrating a mean grain size of over 1 μm and 400 nm in a melt and sub-melt regime, respectively. Along with such grain enlargement, film resistivity is also reduced.

Pulsed laser thermal annealing at the nanosecond timescale was successfully introduced into semiconductor devices manufacturing in the late 2000s for high volume manufacturing of sensitive 3D architectures such as vertical Si-based Insulated Gate Bipolar Transistors, SiC-based vertical power diodes and backside illuminated CMOS imaging sensors. It is now on the verge of being integrated in key annealing process steps in next generation CMOS and memory devices manufacturing. This invited paper presents recent experimental and simulation work involving sub-µs laser annealing for a wide range of applications, from contact formation to material modification and 3D sequential integration.

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The state-of-the-art CMOS technology has started to adopt three-dimensional (3D) integration approaches, enabling continuous chip density increment and performance improvement, while alleviating difficulties encountered in traditional planar scaling. This new device architecture, in addition to the efforts required for extracting the best material properties, imposes a challenge of reducing the thermal budget of processes to be applied everywhere in CMOS devices, so that conventional processes must be replaced without any compromise to device performance. Ultra-violet laser annealing (UV-LA) is then of prime importance to address such a requirement. First, the strongly limited absorption of UV light into materials allows surface-localized heat source generation. Second, the process timescale typically ranging from nanoseconds (ns) to microseconds (μs) efficiently restricts the heat diffusion in the vertical direction. In a given 3D stack, these specific features allow the actual process temperature to be elevated in the top-tier layer without introducing any drawback in the bottom-tier one. In addition, short-timescale UV-LA may have some advantages in materials engineering, enabling the nonequilibrium control of certain phenomenon such as crystallization, dopant activation, and diffusion. This paper reviews recent progress reported about the application of short-timescale UV-LA to different stages of CMOS integration, highlighting its potential of being a key enabler for next generation 3D-integrated CMOS devices.