INTRODUCTION
The measurement of mechanical properties of microelectronic thin films and coatings are very much necessary in many electronic based industries like integrated circuits microprocessors, data storage technologies [1]. All these electronic based industries need the material, which has good mechanical properties, and also to understand the strengthening and deformation mechanisms of the material to evaluate and optimize their use for specific engineering applications. Generally silicon is commonly used for this purpose. The research is going on in order to replace silicon with nickel since nickel and nickel-based materials have received more interest for structural components in the MEMS industries and also nickels are low cost components with high strength, stiffness, fracture toughness, hardness and modulus of elasticity. The materials used for this research are nickel on copper substrate with various thick nesses, nanocrystalline and commercial pure nickels.
Nanoindentation is the commonly used method to measure the quality of films and coatings, which are in nano or micro scale [2]. Test works software is used to analyze the properties like hardness and modulus of elasticity of the material. Its popularity is not only due to high spatial resolution of indentations but also from the simplicity with which mechanical properties of surface layers of bulk materials and of films adherent to their substrates can be determined under essentially compressive conditions [3].
Indentations were made by using there different tips namely Berkovich, Cubecorner and Conical indenters. Berkovich is the standard indenter used for this purpose. Basically for pyramidal indenters like berkovich and cubecorner the hardness increases with decrease in depth, which is

called indentation size effect, and for conical indenters the hardness values are less sensitive to indentation depth [4].
Substrate effects: Pile up and sink in effects.
MEMS materials: From MEMS textbook. Nickels and
Nanoindentation is very common method to measure mechanical properties of thin films and also characterizing the indenter size effects on elastic and plastic deformations of metals from nano to micro sizes [Nanoindentation study of plasticity length scale effects in LIGA Ni micro electro mechanical system structures]. Yield stress in micro and macro scales can be estimated using indentation tests. In this case, an assumption is made that hardness is independent of indentation size [Nanoindentation study of plasticity length scale effects in
LIGA Ni micro electro mechanical system structures] . There are two types of indenters called sharp indenters and spherical indenter. The indentation made by sharp indenters produce low plasticity at the tip of the indenter [Indentation by nominally flat or conical indenters with round corner].
Measuring the mechanical properties of the thin film on substrates has been difficult because of the influence of the substrate. Analyzing the plastic and elastic deformation through the data available from indentation is a complex function of both film and the substrate [Effects of the substrate on the determination of the thin film mechanical properties by nanoindentation].
The standard method used to know the mechanical properties is from load-displacement data were developed primarily for monolithic materials [Oliver WC, Pharr GM. J. Mater Res
1992;7;1564]. The same method is used to measure for the films, which are on substrate. In this case, to measure properties with out substrate effects, a rule of thumb is used which limits the

indentation depth to 10% of the film thickness [Oliver WC, Pharr GM. J. Mater Res
1992;7;1564]. Rule of thumb is used only for the material whose thickness is greater than one micrometer.
For this research, three different tips were used. They are Berkovich, conical and cubecorner.
Berkovich is the most commonly used indenter because it produces low plasticity .
When conical indenter is used, local plastic flow occurs at the contact region for any homogenous plastic or elastic material. When the load on the indenter is removed , the unloading becomes purely elastic [Accurate determination of mechanical properties of thin Al films deposited on sapphire flats using nanoindentation].
During spherical indentation pileup is formed around the indenter, indenter apex, and the film substrate interface .[Substrate effects on indentation plastic zone development in thin soft films]
For sharp indenters, the hardness decrease with increase in penetration depth called as
Indentation size effect where as spherical indenters does not depend on depth of penetration [The correlation of the indentation size effect measured with indenters of various shapes] .
Nix and Gao model was introduced to measure the indentation size effect using dislocation loops. This model assumes that the plastic deformation of the surface is due to generation of dislocation loops in an approximately hemispherical volume below the region of contact. The density of geometrically necessary dislocations are given by

G

3
2 bh
P tan 2


In Nix and Gao model it also assumes that the flow stress is related to the shear strength by Von mises rule
 
3

and the hardness is related to the flow stress by the Tabor factor of 3. Then the expression is given by
H

H
0
1
 h h
P
*
(Nix and Gao model)
[Nanoindentation study of plasticity length scale effects in LIGA Ni micro electro mechanical system structures] suggested that accurate hardness values can be obtained by calibrating the indenter geometry and tip rounding , and pile up and sink in effects at the sub micron and nano scales.