Microsecond non-melt UV laser annealing for future 3D-stacked CMOS

Abstract

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.

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

“…The calculated film resistivity values imply that the active carrier concentration achieved by ns UV-LA SPER could be higher than that of ns UV-LA LPER. We have reported similar attempts also for µs UV-LA SPER processes [47,57], where the monocrystalline regrowth and flat surface morphology are basically reproduced as in ns UV-LA ones. Interestingly, as shown in Figure 11a, µs UV-LA SPER processes introduce the surface segregation of dopants (indeed, it is known for furnace SPER of As-implanted Si, as reported in Ref.…”

“…Therefore, in terms of the productivity, ns UV-LA might not be an optimal option. To address it, extending the process timescale towards µs scale may help [47]. In the previously reported ns UV-LA SPER, the surface morphology does not show serious degradation [46].…”

Atomistic Insights into Ultrafast SiGe Nanoprocessing

“…In the context of group IV elemental and compound semiconductor processing, pulsed-LA applications are ubiquitous. ,, These include the fabrication of poly-Si thin-film transistors, − ultrashallow device junctions, ,− efficient contacts by silicidation, explosive crystallization, − strain, defect, , and dopant engineering. − Localized heating minimizes the risk of damaging sequentially integrated components of monolithic three-dimensional (3D) devices. − In optoelectronics, pulsed-LA is a key process for fabricating poly-Si displays, − thin metal-oxides, pure-carbon electrodes for touch screens or solar cells, and hyper-doped semiconductors for near-infrared photodetectors . It also allows strain, composition and morphology engineering of fiber-based photonic devices, and fabrication of heavily doped superconducting silicon for monolithic quantum device integration. ,− Despite all of these applications, understanding the ultrafast nonequilibrium kinetics of the liquid/solid interface in early stages of the process and correlating it to the postirradiation morphology and properties is challenging.…”

“… 21 − 25 Localized heating minimizes the risk of damaging sequentially integrated components of monolithic three-dimensional (3D) devices. 26 − 30 In optoelectronics, pulsed-LA is a key process for fabricating poly-Si displays, 31 − 34 thin metal-oxides, 7 pure-carbon electrodes for touch screens or solar cells, 35 and hyper-doped semiconductors for near-infrared photodetectors. 36 It also allows strain, composition and morphology engineering of fiber-based photonic devices, 8 and fabrication of heavily doped superconducting silicon for monolithic quantum device integration.…”