Microstructures Of Wet Etching Patterned Sapphire Substrate And Its Simulation Research

The patterned sapphire substrate is a periodic pattern structure etched by a wet etching process on the basis of a planar sapphire substrate.It has great advantages in improving the luminous efficiency of GaN-based LEDs.The anisotropic wet etching characteristics of sapphire are relatively complicated,and the resulting etched structures are directly affected by many factors,such as mask shapes,sizes and directions,etching environments,etc.Based on this,this paper uses the idea of geometric method to develop a simulation system for simulating the sapphire anisotropic wet etching process by means of Level Set method and explores the influence of different etching conditions on the etched morphology.The main contents of the paper are as follows:1)Firstly,the full etch rate of sapphire anisotropic wet etching is obtained by hemispherical etching experiments.Based on the full rate of etching and the Level Set method,the different directions of sapphire different crystal planes and arbitrary mask patterns can be developed.High-precision simulation system of heterosexual wet etching,and etched morphologies of sapphire spheres under different etching environments are simulated wel.At the same time,the simulation system is versatile and suitable for wet etching simulation of various crystal materials.2)With the Level Set simulation system,the mask shape is designed and the corresponding etching time is determined.The anisotropic etching characteristics of the C-plane sapphire wafer were studied by etching long rectangular grooves and cavities and mesas of sapphire under the sapphire complex mask and etching pattern.At the same time,the Level Set is applied to different patterned sapphire substrate structures(long rectangular mesas and grooves,circular grooves).The composition of the etched topography of the sapphire long rectangular grooves and circular grooves under different etching environments are analyzed.Finally,the etched surface of the sapphire R plane is presented using the Level Set simulation system.3)The etching process of double-step etching of sapphire pattern substrate was explored.Based on the physical mechanism of LED internal light propagation,the appropriate range of the slope angle of the patterned sapphire substrate structure is determined.With the Level Set simulation system,some process parameters affecting the double-step etch morphology(single-step etching time and mask size)are explored.And according to the shape of the simulation,the inclination data is measured to obtain a suitable processing method.Investigating the effect of mask size on the morphology after two-step etching,combined with the Level Set simulation system,the etched topography under different mask pattern sizes is obtained to determine the appropriate mask size.