| AVS 61st International Symposium & Exhibition | |
| Manufacturing Science and Technology | Thursday Sessions |
| Session MS-ThP |
| Session: | Manufacturing Science and Technology Poster Session |
| Presenter: | Adriano Ricardo do Nascimento Jr., University of Campinas, Brazil |
| Authors: | A.R. Ricardo do Nascimento Jr., University of Campinas, Brazil L.T. Tiago Manera, University of Campinas, Brazil J.A. Alexandre Diniz, University of Campinas, Brazil A.R. R. Silva, University of Campinas, Brazil M.V. Vinicius Puydinger dos Santos, University of Campinas, Brazil A.C. Cerqueira S. Jr., National Institute of Telecommunications, Brazil L.A. A. M. Barea, University of Campinas, Brazil N.C. C. Frateschi, University of Campinas, Brazil |
| Correspondent: | Click to Email |
Silicon nitride (SixNy) films deposited by low-pressure electron cyclotron resonance plasma enhanced chemical vapor deposition (ECR-CVD) at room temperature are proposed for nonlinear optics applications in the telecommunications C-band. Due to the high silicon nitride nonlinearity, these films recently have also been used for nonlinear optics [1]. For nonlinear applications such as the generation of frequency combs, the waveguide needs a zero dispersion point in the middle of C-band, requesting large waveguide area. Unfortunately, these thick SixNy films (>400 nm) have high stress and suffer from catastrophic cracking, which reduces the device efficiency [2]. Using numerical simulations it was demonstrated that for refractive index (η) values greater than 2, the area of the waveguide with zero dispersion point at λ = 1.55 µm is greatly reduced.
By varying deposition parameters, such as gas pressure (4-6 mTorr) and Si/N ratio (0.62-1.25), SixNy films with high deposition rate and high refractive index was obtained. In many cases, for larger pressure values a considerable increase in the deposition rate is observed, and for lower N2 flow was observed a large increase of η (due to high concentration of Si). However, increasing the gas pressure, a reduction of η due the incorporation of hydrogen in the film was also observed.
A Si-rich silicon nitride layer with 730 nm of thickness, refractive index of 2, high deposition rate, low hydrogen concentration and roughness average of 0.52 nm was deposited above a Si/SiO2 wafer during 100 minutes using ECR-CVD and applied for fabrication of nonlinear microring resonators. Due to the low temperature deposition, no thermal stress was observed in the SixNy film, allowing a large thickness (obtained with only one deposition process) . The main advantage of higher Si concentration in this film is the higher values of η and the absence of losses caused by two-photon absorption, responsible for the introduction of additional losses in silicon based waveguides [3].
After experimental measurements, microring resonators having a radius of 60 µm, presented an equidistant Free Spectral Range and a Q-factor of 4x103 was achieved, showing the high efficiency of the device. Finally, using the deposition process at low temperature and controlling the process parameters such as pressure and gas ratios, a remarkable free thermal stress silicon nitride film was obtained, overcoming the stress limitation of thick silicon nitride films.
[1] J. S. Levy et al., Nat. Photonics, vol. 4, no. 1, pp. 37–40, 2009.
[2] K. Luke et al., Opt. Express 21, 22829-22833, 2013.
[3] H. K. Tsang et al., Appl. Phys. Lett., vol. 80, no. 3, p. 416, 2002.