The purpose of this project was to develop a repeatable process flow for Silicon-Nitride optical waveguides at RIT. Previous projects have fabricated optical waveguides out of amorphous silicon and polymers but never out of Nitride. The grating coupler pitch was varied from 700nm to 1500nm and the length was varied from 100μm to 1000μm. A target Nitride deposition thicknesses of 250nm, 500nm, and 750nm were deposited through LPCVD methods and were measured to be 150nm, 450nm, and 770nm. The thicknesses were chosen to be half the waveguide width for optimal transmission. Fabrication was successful for all three waveguide widths on the 450nm and 770nm thick Nitride wafers for both the Loopback and Ring Resonator designs. The grating couplers were able to resolve with pitches of 900nm to 1500nm but the 800nm pitch and under were overexposed and did not develop. Optical testing was unable to be performed due to test setup being broken at the end of fabrication. Instead simulations of the test setup were done to see the optimal transmission for the 450nm thick and 1000nm wide Nitride grating coupler and waveguide. The test setup can vary wavelength from 1500nm to 1600nm so optimal transmission should have been about 1550nm. The best transmission results came from the tester head at an angle of 24 degrees and the grating coupler pitch of 1300nm showing a peak at the 1500nm wavelength.
"Fabrication of Photonic LPCVD Silicon-Nitride Waveguides,"
Journal of the Microelectronic Engineering Conference: Vol. 25
, Article 1.
Available at: https://scholarworks.rit.edu/ritamec/vol25/iss1/1