Raghunathan Vivek, Izuhara Tomoyuki, Michel Jurgen, Kimerling Lionel
Microphotonics Center, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, USA.
Opt Express. 2012 Jul 2;20(14):16059-66. doi: 10.1364/OE.20.016059.
Temperature sensitivity of Si based rings can be nullified by the use of polymer over-cladding. Integration of athermal passive rings in an electronic-photonic architecture requires the possibility of multi-layer depositions with patterned structures. This requires establishing UV, thermal and plasma stability of the polymer during multi-layer stacking. UV stability is enhanced by UV curing to saturation levels. However, thermal stability is limited by the decomposition temperature of the polymer. Further, robust performance in oxidizing atmosphere and plasma exposure requires a SiO(2)/SiN(x) based dielectric coatings on the polymer. This communication uses a low temperature (130°C) High Density Plasma Chemical Vapor Deposition (HDPCVD) for dielectric encapsulation of polymer cladded Si rings to make them suitable for device layer deposition. UV induced cross-linking and annealing under vacuum make polymer robust and stable for Electron Cyclotron Resonance (ECR)-PECVD deposition of 500nm SiO(2)/SiN(x). The thermo-optic (TO) properties of the polymer cladded athermal rings do not change after dielectric cap deposition opening up possibilities of device deposition on top of the passive athermal rings. Back-end CMOS compatibility requires polymer materials with high decomposition temperature (> 400°C) that have low TO coefficients. This encourages the use of SiN(x) core waveguides in the back-end architecture for athermal applications.
通过使用聚合物外包层，可以消除硅基环的温度敏感性。将无热无源环集成到电子 - 光子架构中需要具备多层沉积有图案结构的可能性。这就要求在多层堆叠过程中确定聚合物的紫外线、热和等离子体稳定性。通过紫外线固化至饱和水平可提高紫外线稳定性。然而，热稳定性受聚合物分解温度的限制。此外，在氧化气氛和等离子体暴露环境中要实现稳健性能，需要在聚合物上涂覆基于SiO(2)/SiN(x)的介电涂层。本通讯采用低温（130°C）高密度等离子体化学气相沉积（HDPCVD）对聚合物包覆的硅环进行介电封装，使其适合器件层沉积。紫外线诱导交联和真空退火使聚合物对于500nm SiO(2)/SiN(x)的电子回旋共振（ECR）-PECVD沉积具有稳健性和稳定性。在沉积介电帽之后，聚合物包覆的无热环的热光（TO）特性不变，这为在无源无热环顶部进行器件沉积开辟了可能性。后端CMOS兼容性要求聚合物材料具有高分解温度（> 400°C）且热光系数低。这促使在后端架构中使用SiN(x)芯波导用于无热应用。
