Dissolution of Nickel-Manganese-Gallium Alloys: the first step for
manufacturing hybrid micro-devices composed of Ni-Mn-Ga and Silicon
layers
Abstract
Our aim is to develop next generation of MEMS (microelectromechanical
systems) devices that are composed Ni-Mn-Ga and silicon layers. Due to
the large magnetic-field-induced strains of Ni-Mn-Ga, actuating
components can be fabricated in the Ni-Mn-Ga layers. Other functional
components can be manufactured in the silicon layer. Single crystalline
Ni-Mn-Ga alloys that are grown by using the Bridgman vertical growth
technique have thus far obtained the largest magnetic field-induced
strain (MFIS), a magnetic shape memory (MSM) effect. Similar to silicon
wafers, Ni-Mn-Ga wafers are also sliced from crystal-oriented single
crystalline ingots. To fabricate hybrid MEMS devices such as
micromanipulators and robots, lab-on-chip containing micropump manifolds
and valves, or vibration energy harvesters, the fabrication processes
used for MEMS devices will be used are also be used to fabricate
components in the Ni-Mn-Ga layer of the hybrid MEMS devices. One of the
most important processes for MEMS fabrication is the structuring of
materials by chemical etching. The main goal of this study is to obtain
evidence that the etchant etches silicon but not Ni-Mn-Ga and to
identify an etchant that etches Ni-Mn-Ga but not silicon. The present
paper reports on a novel experiment in dissolving Ni-Mn-Ga alloys. An
etchant composition of 69% HNO3, 98% H2SO4, and CuSO4•5H2O is proposed
for dissolving Ni-Mn?Ga alloys and the variation in the dissolution rate
by adjusting the concentrations of HNO3 and ultrapure water (UPW) is
demonstrated. This etchant was demonstrated to etch Ni-Mn-Ga but not
silicon. The HF+HNO3 acidic solution commonly used for etching silicon
does not dissolve Ni-Mn-Ga