Recent Progresses and Perspectives of UV Laser Annealing Technologies for Advanced 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 (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.

Direct Laser Writing: From Materials Synthesis and Conversion to Electronic Device Processing

“…These aspects of DLW provide broad capabilities for application in the fabrication of sub‐micron lines and components, suitable for several processes. Although fully laser‐processed ICs have yet to be explored by DLW microfabrication approaches, the synthesis, and engineering of metals and semiconductors may enable FEOL processes for individual component development, to complement uses such as laser photolithography or laser annealing, [ 425 ] in cases where cost reduction and straightforward fabrication is preferred to high‐standard performance. In this specific case, integrating the capability of TP‐DLW processes for the high‐resolution synthesis and printing of metal conductors and different types of semiconductor materials, from more accessible liquid precursor forms, is beginning to be a reliable tool for microscale fabrication, monolithic integration and seamless assembly of electronic components, towards laser fabricated microelectronics.…”