The effectivity of haloalkane (CH₂FCF₃) plasma in selective etching of a quartz crystal microbalance biosensor

Profiling a quartz (SiO2) crystal in the application of QCM biosensor is one of the efforts in enhancing its sensitivity and stability. The profiling was realized by a plasma etching method using haloalkane gas (CH₂FCF₃). The plasma was generated using a low frequency (40 kHz) generator with a power of 100 watts. The effectivity of haloalkane plasma was measured by varying the pressure in the reactor ranged betweeen 0.8 Torr and 1.4 Torr. Since the pressure plays the main role in the process, other parameters such as gas flow rate, temperature and etching time were set fixed. The specimen was prepared by covering a half part of the crystal while exposing the other half part for the plasma etching. The covered area was set as a reference of the etching process. The effectiveness of the haloalkane plasma etching process was evaluated by measuring the etching rate and anisotropy coefficient. The observation and measurement of the specimens were carried out using a topography measurement system (TMS). The measurement results indicated that the highest etching rate was 8.95 nm/min which occurred at a pressure of 1 Torr. The anisotropy coefficient was also affected by the chamber pressure. It was inversely proportional to the pressure in the reactor.