3.2.4 Summary to: 3.2 Mechanical Properties

	Thin films have other spatial properties besides their thickness, i.e. roughness
		Interface roughness and surface roughness R defined by their "root mean square".
		R  =  æ ç è 1 N    N S i=1 zi2 ö ÷ ø ½
	Useable thin films adhere to their substrate.
		A direct measure of adhesion is the interfacial energy gAB between film A and substrate B.
		The phase diagram provides some guideline. Complete miscibility = good adhesion, (eutectic)) decomposition =(?) low adhesion. Calculations of g are difficult.
		Full adhesion can only be obtained for films grown on a substrate. Adhesion energies can be measured.
	Generally, there will be stress s and strain e in a thin film and its substrate.			Stress and strain in thin films can be large and problematic!
		A major source of strain is the difference of the thermal expansion coefficients a
		eTF   =    DT · Da       sTF   =   Y · DT · Da
	Stress in thin films may relax by many mechanisms; and this might be good or bad: Cracking or buckling Plastic deformation Viscous flow Diffusion Bending of the whole system (Warpage)
		Warpage can be a serious problem in semiconductor technology.
		Exercise 3.2-1 All Questions to 3.2

© H. Föll (Semiconductor Technology - Script)