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Lecture

Stress in Thin Films: Film Growth and Microfabrication

In course

MICRO-621: MOOC: Micro and Nanofabrication (MEMS)

Micro- and nanofabrication can be taught to students and professionals by textbooks and ex-cathedra lectures, but the real learning comes from seeing the manufacturing steps as they happen. This MOOC will not only explain the basics of microfabrication but ...

Description

This lecture covers the stress in thin films, including extrinsic and intrinsic stresses, uniform stress distribution, and stress gradients. It also discusses factors like expansion coefficients, Young's modulus, Poisson ratio, and thermal expansion. The lecture further explores lattice mismatch, voids, foreign atoms, and the impact of bombardment during deposition on stress levels. Additionally, it delves into the Stoney equation, concave and convex shapes, and their effects on film stress. The presentation concludes with a summary of film growth, focusing on atoms arrival, film-substrate interface, adhesion, growth modes, crystal structure, and stresses in thin films, all within the context of micro and nanofabrication (MEMS).

In MOOC

Micro and Nanofabrication (MEMS)

Instructors (2)

Martinus Adela Maria Gijs

Martin A.M. Gijs received his degree in physics in 1981 from the Katholieke Universiteit Leuven, Belgium and his Ph.D. degree in physics at the same university in 1986. He joined the Philips Research Laboratories in Eindhoven, The Netherlands, in 1987. Subsequently, he has worked there on micro-and nano-fabrication processes of high critical temperature superconducting Josephson and tunnel junctions, the microfabrication of microstructures in magnetic multilayers showing the giant magnetoresistance effect, the design and realisation of miniaturised motors for hard disk applications and the design and realisation of planar transformers for miniaturised power applications. He joined EPFL in 1997. His present interests are in developing technologies for novel magnetic devices, new microfabrication technologies for microsystems fabrication in general and the development and use of microsystems technologies for microfluidic and biomedical applications in particular.

Jürgen Brugger

I am a Professor of Microengineering and co-affiliated to Materials Science. Before joining EPFL I was at the MESA Research Institute of Nanotechnology at the University of Twente in the Netherlands, at the IBM Zurich Research Laboratory, and at the Hitachi Central Research Laboratory, in Tokyo, Japan. I received a Master in Physical-Electronics and a PhD degree from Neuchâtel University, Switzerland. Research in my laboratory focuses on various aspects of MEMS and Nanotechnology. My group contributes to the field at the fundamental level as well as in technological development, as demonstrated by the start-ups that spun off from the lab. In our research, key competences are in micro/nanofabrication, additive micro-manufacturing, new materials for MEMS, increasingly for wearable and biomedical applications. Together with my students and colleagues we published over 200 peer-refereed papers and I had the pleasure to supervise over 25 PhD students. Former students and postdocs have been successful in receiving awards and starting their own scientific careers. I am honoured for the appointment in 2016 as Fellow of the IEEE “For contributions to micro and nano manufacturing technology”. In 2017 my lab was awarded an ERC AdvG in the field of advanced micro-manufacturing.

Official source

Related concepts (32)

Evaporation (deposition)

Evaporation is a common method of thin-film deposition. The source material is evaporated in a vacuum. The vacuum allows vapor particles to travel directly to the target object (substrate), where they condense back to a solid state. Evaporation is used in microfabrication, and to make macro-scale products such as metallized plastic film. Evaporation involves two basic processes: a hot source material evaporates and condenses on the substrate. It resembles the familiar process by which liquid water appears on the lid of a boiling pot.

Chemical vapor deposition

Chemical vapor deposition (CVD) is a vacuum deposition method used to produce high-quality, and high-performance, solid materials. The process is often used in the semiconductor industry to produce thin films. In typical CVD, the wafer (substrate) is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. Frequently, volatile by-products are also produced, which are removed by gas flow through the reaction chamber.

Physical vapor deposition

Physical vapor deposition (PVD), sometimes called physical vapor transport (PVT), describes a variety of vacuum deposition methods which can be used to produce thin films and coatings on substrates including metals, ceramics, glass, and polymers. PVD is characterized by a process in which the material transitions from a condensed phase to a vapor phase and then back to a thin film condensed phase. The most common PVD processes are sputtering and evaporation.

Thin film

A thin film is a layer of material ranging from fractions of a nanometer (monolayer) to several micrometers in thickness. The controlled synthesis of materials as thin films (a process referred to as deposition) is a fundamental step in many applications. A familiar example is the household mirror, which typically has a thin metal coating on the back of a sheet of glass to form a reflective interface. The process of silvering was once commonly used to produce mirrors, while more recently the metal layer is deposited using techniques such as sputtering.

Stress (mechanics)

In continuum mechanics, stress is a physical quantity that describes forces present during deformation. An object being pulled apart, such as a stretched elastic band, is subject to tensile stress and may undergo elongation. An object being pushed together, such as a crumpled sponge, is subject to compressive stress and may undergo shortening. The greater the force and the smaller the cross-sectional area of the body on which it acts, the greater the stress. Stress has units of force per area, such as newtons per square meter (N/m2) or pascal (Pa).

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