Lasers solutions for wafer and thin‐film annealing

Abstract

The application of lasers for the annealing of wafer‐based and thin‐film microelectronic devices is steadily increasing. Excellent control of material characteristics (for example, dopant activation profile) can be achieved through proper selection of laser parameters, such as wavelength, pulse duration and fluence. In this paper, we present recent results achieved with our industrial lasers and tailored optical systems used for annealing and activation. Such systems include Excimer Lasers, q‐switched DPSS Lasers and our unique high‐power CW laser system that delivers scalable output power of multiple hundreds of Watts in the visible wavelength range. One focus is the formation of ultra‐shallow Source/Drain junctions for CMOS nodes below 90 nm. We will present results from Excimer Laser Annealing (ELA) that show high dopant activation, exact control over the junction depth and efficient implant damage removal. Another application is power MOSFET, where a laser source is utilized for dopant activation and damage healing over micron depths. The choice of wavelength (i.e. green) with adequate interaction time leads to an optimized activation profile. The use of single laser pulses, pulse trains or continuous irradiation leads to the preferred annealing result. Crystallization of thin films is another large domain for laser annealing equipment. We will present selected results from silicon thin‐film annealing, which is commonly used in the Flat Panel Display industry. The applicability of these technologies beyond displays into electronics and photo‐voltaic applications is also shown. In addition, descriptions are provided of experimental results and simulations of laser sources and optical systems that enable variation of the temperature profile within the irradiated materials and offer the scalability and maturity as demanded by the semiconductor industry. (© 2008 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Line beam processing for laser lift‐off of GaN from sapphire

“…Large area processing with homogenized, line beam shaped UV excimer laser pulses has been successfully employed in low temperature polysilicon (LTPS) annealing for flat panel displays over the last two decades 5, 6.…”

Nanocrystalline Ferroelectric BiFeO3 Thin Films by Low-Temperature Atomic Layer Deposition

“…However, in general, high-temperature thermal treatments and textured growth are required for improved functional properties. This adds complexity in the materials processing in device integration. ,− One approach is to achieve locally high temperatures using laser annealing. − Alternatively, efforts have been made to develop new low-temperature synthesis routes for ferroelectric perovskite oxides; many of these are based on solution methodologies requiring processing temperatures of 300–400 °C. − The unique characteristics of conformality, atomic scale control, and low-temperature deposition that atomic layer deposition technique (ALD) offers can have direct technological applications: well controlled interfaces, smaller and more demanding structures (3D substrates), and increased density of devices, including those that require flexible and transparent substrates, that have been hindered by the high-temperature thermal treatment constraints. ,− This cost-effective chemical deposition technique is based on a self-limiting surface reaction mechanism that makes it very attractive for area-selective deposition. In principle, this could allow simultaneous patterning for the growing films, which offers some advantages for hard-to-pattern materials relative to traditional top-down patterning techniques. , ALD of ternary oxides such as perovskite oxides is still in its early stages. − Most as-deposited ALD films are amorphous or polycrystalline, although epitaxial oxides can also be obtained in the as-deposited stage (<300 °C) using structurally compatible buffer layers and single crystal substrates. − …”

Advanced-UV excimer laser processing

“…The transformation of the amorphous silicon layer is obtained by selectively annealing and recrystallizing the amorphous silicon layer with the effect that a highly ordered microstructure is achieved. Due to the short wavelength of 308 nm and the small penetration depth, the underlying glass substrate is not affected by the high power excimer laser beam [4].…”