Recent Progresses and Perspectives of UV Laser Annealing Technologies for Advanced CMOS Devices

TL;DR

This paper reviews recent advances in short-timescale UV laser annealing technologies, emphasizing their potential to enable low-thermal-budget, high-performance 3D CMOS device fabrication through localized, rapid surface heating and material property control.

Contribution

It provides a comprehensive overview of UV-LA techniques and discusses their advantages for 3D CMOS integration, highlighting recent progress and future perspectives.

Findings

UV-LA enables localized surface heating with minimal heat diffusion.

Short-timescale UV-LA can control crystallization and dopant activation.

UV-LA is a promising technology for next-generation 3D CMOS devices.

Abstract

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 ({\mu}s) 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.