  Two-dimensional (2D) materials are considered for numerous applications in
microelectronics, although several challenges remain when integrating them into
functional devices. Weak adhesion is one of them, caused by their chemical
inertness. Quantifying the adhesion of 2D materials on three-dimensional
surfaces is, therefore, an essential step toward reliable 2D device
integration. To this end, button shear testing is proposed and demonstrated as
a method for evaluating the adhesion of 2D materials with the examples of
graphene and hexagonal boron nitride (hBN), molybdenum disulfide, and tungsten
diselenide on silicon dioxide (SiO${_2}$) and silicon nitride substrates. We
propose a fabrication process flow for polymer buttons on the 2D materials and
establish suitable button dimensions and testing shear speeds. We show with our
quantitative data that low substrate roughness and oxygen plasma treatments on
the substrates before 2D material transfer result in higher shear strengths.
Thermal annealing increases the adhesion of hBN on SiO${_2}$ and correlates
with the thermal interface resistance between these materials. This establishes
button shear testing as a reliable and repeatable method for quantifying
adhesion of 2D materials.
