Deep reactive ion etching of polyimide for microfluidic applications

In this work, deep reactive ion etching (DRIE) of polyimide (PI) was carried out for the fabrication of a microfluidic channel and reservoir by using a CF₄/O₂ inductively coupled plasma. The DRIE characteristics of PI were investigated by varying process parameters such as the total gas flow rate, the gas flow ratio, and the dc self-bias voltage (V_dc)- The results show that the etch rate increases with increasing total flow rate and with increasing Vdc due to the increased fluxes of reactive radicals and ions and to the increased ion-bombarding energy, respectively. The lateral etch (undercut) also increases with increasing of V_dc When the CF₄/(CF₄ + O₂) flow ratio was varied, a maximum etch rate as high as 2.2 μm/min was obtained at a 20 % CF₄ flow ratio. The 50-μm-thick PI sheet could be etched, though vertically, for application to a microfluidic channel or reservoir.