Process variation in silicon photonic devices

Abstract

An array of passive silicon-on-insulator optical devices is laid out in repeating patterns on four foundry-fabricated wafers. The physical and optical characterization of these microrings, racetrack resonators, and directional couplers are found to exhibit significant variation in optical response. A device-heating experiment carried out on a number of different devices demonstrates that thermal effects are independent of the device's location on the wafer. An analysis of the variation of the optical responses of the room-temperature devices is used to determine the process variation. We find that if we form successive arrays of the values of a quantity of interest (the peak wavelength of a transfer function) at a single device at some point on the wafer, and then increase the size of the array by including the values of the devices at ever greater distances from the original, then the variance of the values of the successive arrays increases linearly with the linear extent of the sample. That is, the process variation exhibits "random walk" pattern with spatial extent. We express the process variation in units of variance per length and find that our measured values agree with others in the literature; that is, the process variation is approximately 1 nm2/cm.

Chip-Scale Silicon Photonic Interconnects: A Formal Study on Fabrication Non-Uniformity

“…Another important observation is that there is a good agreement between the results in Fig. 7(a), which is based on (13), and those indicated in Figs. 9(a) and 9(b).…”

“…The measured data gathered over multiple reticles, wafers, and fabrication lots indicated that the absolute resonance wavelengths of individual devices cannot be controlled across wafers or even across reticles or fields within a wafer. Chen et al studied process variations in microring resonators, racetrack resonators, and directional couplers all identically designed but fabricated through two different establishments (LETI and IMEC) [13]. They reported variations with the variances of 1.3, 1.3, and 0.33 nm 2 /cm in the responses of the microrings, racetrack resonators, and directional couplers, respectively.…”

Stochastic simulation and robust design optimization of integrated photonic filters

“…On the contrary, stochastic uncertainties related to fabrication variations, such as waveguide geometry deviation, gap opening issues, material composition fluctuations, and surface roughness, are unavoidable in production processes [5][6][7][8][9]. It is well known that such uncertainties can have a dramatic impact on the functionality of fabricated circuits [4,[10][11][12][13][14][15].…”

Uncertainty quantification of silicon photonic devices with correlated and non-Gaussian random parameters

“…Thanks to its ease of integration with the CMOS process, silicon photonics can remarkably reduce fabrication costs, increase the integration scale and improve the overall system performance [2]. However, silicon-based optical devices are very sensitive to fabrication process variations, leading to potentially significant device performance degradations and potential system failures [3][4][5][6][7][8].…”