Development of densification heat treatment system to remove defects generated in the upper clad flame hydrolysis deposition process of planar silica optical waveguide

摘要

In the planar silica photonic waveguide film or silicon wafers, the interface between the upper clad layer and the densification heat treatment process is poor due to residual materials and uneven excess dopant after each interfacial process of the silicon substrate or silica waveguide, And defects such as porosity, particularly a large number of pores. In this case, not only the performance of the completed device is lowered due to the pores generated at this time, but the product itself is also discarded when the pore is severe, resulting in a large economic loss.;As a method for removing or suppressing pores in the upper clad layer fabrication process, up to now, it has been necessary to increase the density of the silica fparticles in the upper clad layer fabrication process, to decrease the heating rate or to use a vacuum heat treatment method However, there is no clear solution to this problem yet.;In the present invention, by understanding the mechanism of producing pores for removing defects such as interfacial bonding defects, crystal phases and pores in the upper clad layer manufacturing process by the flame hydrolysis deposition method, it is possible to provide an economical and continuous Densification heat treatment system.;The method developed by the present invention is a method in which a sample of fsilica particles deposited by a flame hydrolysis deposition method is rapidly heated at a temperature of about 500C in a heat treatment apparatus to rapidly heat the backside of the sample, Since residual materials or non-equilibrium dopants in the existing process start to be heated and vaporize, these vaporized gases easily escape to the surface of the upper layer of the sample before the fsilica particles are densified, , Defects such as crystal phase and pore can be removed.;Unlike the conventional method of increasing the density of fsilica particles in the flame hydrolysis deposition process, the apparatus developed in the present invention is capable of detecting defects such as pores, crystal phases and interface bonding defects, It is possible not only to improve the yield of the device, but also to add the rapid heating device to the densification heat treatment device which has been used in the past, thereby reducing the production cost of the device.;In addition, rapid heating and densification heat treatment can be performed at the same time without moving the sample, so that the sample is not exposed to the atmosphere, so contamination from the outside can be suppressed as much as possible, so that a high-quality device can be manufactured.