Edwin Jan Klein - Universiteit Twente

Chapter 5
Figure 5.21. Process flow showing the steps required to make the port and resonator
waveguides in Si3N4. (Process: Vertical II, using contact+stepper lithography)
A 0.5 µm thick layer of TEOS SiO2 is then deposited and annealed (step 17). On top
of the TEOS SiO2 a top cladding of 3.5 µm PECVD SiO2 is deposited after which the
wafer is annealed for the third time (step 18).
In microscope images taken of the devices after processing step 15 the advantages of
the stepper lithography are clearly visible. In Figure 2.22 a perfectly aligned
microring resonator is shown which would be difficult to achieve when using only
contact lithography. In Figure 2.23 the high resolution of the stepper is demonstrated:
the gap between the two resonators measures less than 300 nm but is fully opened.
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