Research On Loss And Coupling Characteristics Of Optical TSVs

TSV(Through-Silicon Vias) technology can significantly reduce the length of the wires between the different chip layers. Thus it becomes the core technology of 3D-IC technologies. Optical TSVs have the advantages of optical waveguides and electrical TSVs. Compared with electrical TSVs, optical TSVs are more efficient with greater bandwidth, smaller parasitic effects and stronger anti-interference ability. Thus optical TSV technology has become another new field of 3D integration technologies.Diameter, height, wavelength and other factors have a great influence on the loss characteristics of optical TSVs. Besides, optical TSVs are manufactured with TSV technology, so the defects of TSV technology will also affect the performance of optical TSVs. In order to improve the integration of optical TSVs, the distance between optical TSVs should be as small as possible. However, when the distance between optical TSVs reduces, the coupling between these optical TSVs will be greater. We study the loss and coupling characteristics of optical TSVs with the assistance of a software called RSOFT.In term of the loss characteristics of optical TSVs, at first this paper studies the influence of structure parameters and wavelength on transmission loss. The simulation results indicate that the transmission loss of optical TSVs becomes greater with the decrease of core diameter and the increase of wavelength and height. Secondly, this paper studies the transmission loss of optical TSVs with different sidewall conditions. The results indicate that the greater the degree of tilt of the sidewalls, the greater the transmission loss of optical TSVs. The degree of loss depends on the end face where the incident light comes from. The transmission loss of optical TSVs with rough sidewalls is greater than optical TSVs with smooth sidewalls. For optical TSVs with rough and inclined sidewalls, the roughness of the sidewalls has less influence on the transmission loss than the degree of tilt of the sidewalls.In term of the coupling characteristics of optical TSVs, at first this paper studies the influence of distance between two optical TSVs on coupling. The simulation results indicate that the coupling of two optical TSVs which are close to each other becomes smaller with the increase of their distance. Secondly, this paper studies the coupling of optical TSVs with different sidewall conditions. The results indicate that smooth optical TSVs have smaller coupling effect than optical TSVs with protrusions or depressions on the sidewalls. When the distance is small, smooth optical TSVs have much smaller coupling effect than optical TSVs with protrusions or depressions on the sidewalls. Optical TSVs with inclined sidewalls and incident light from the upper end have smaller coupling effect on adjacent optical TSVs than optical TSVs with inclined sidewalls and incident light from the lower end. Optical TSVs with depressions on the sidewalls have greater coupling effect on adjacent optical TSVs than optical TSVs with protrusions on the sidewalls. For optical TSVs with rough and inclined sidewalls, incident light from the lower end can cause greater coupling effect on adjacent optical TSVs than incident light from the upper end. For optical TSVs with rough and inclined sidewalls, the combined effect of rough sidewalls and incident light from the upper end can cause greater coupling effect on adjacent optical TSVs.