The manufacture of Micro Electro Mechanical Systems (MEMS) benefits from new techniques and processes to be inserted in industrial applications such as the lab-on-a-chip technology. Among these techniques, we find the supercritical fluid deposition process for thin film. The main goal of this paper is the study of adsorption and mass transfer of mixture in a rectangular cavity with a hot plate and an adsorbent at the lower limit. The physical model consists of a mixture of diluted solute (naphthalene-supercritical CO2) enclosed in rectangular cavity of height of order 1 mm. To benefit from the supercritical fluid specific properties and optimize thermodynamics conditions allowing a better adsorption with a good mass transfer, effects of the critical point proximity and heating are the object of several numerical simulations in the present work. The employed mathematical model is based on the solution of Navier-Stokes equations, associated with energy and mass scattering equations including the additional Peng-Robinson state equation. In order to reduce computational costs, these equations are solved as part of the low Mach approximation. The velocity field, perturbation of the mass fraction as well as the temporal evolution of the average Sherwood number are presented for different heatings. The confinement effect is also analysed. The results show that in the mixture critical point neighborhood and for a very high heated wall, the homogeneous adsorption of the solute is obtained. Among other key results, we cite that, under the same optimized conditions, the better is the mass transfer on the adsorbent plate.