Inductively coupled plasma etching to fabricate sensing window for polymer waveguide biosensor application

► We designed and fabricated an improved sensing window based on the ICP method. ► The sensitivity of the sensor was enhanced by a factor of 2.8 in theory. ► The etching rate of P(MMA–GMA) was twice as fast as that of SU-8 2005. ► The parameters were optimized to minimize the surface roughness in the etched area. ► The sensor presented a higher sensitivity than the conventional waveguide sensor. Integrated polymeric waveguide biosensors are usually used for the detection of chemical/biological samples. To improve the sensitivity of the conventional waveguide sensors with only one sensing surface, we design and fabricate an improved sensing window with three sensing surfaces based on inductively coupled plasma etching method, whose sensitivity can be enhanced by a factor of 2.8 in theory. The effects of etching parameters, especially the antenna power, the bias power and the O2 flow rate were systematically studied and the parameters were optimized to fabricate the sensing window. A single-mode balanced Mach–Zehnder interferometer waveguide biosensor with the improved sensing window was fabricated under this optimum etching condition, and presented a higher sensitivity than that of the sensor with conventional sensing window. This type of sensing window will be very useful in polymer waveguide biosensor devices.