Preparation Of LED Chip Sample For SIMS Analysis

In this paper, on the basis of the analysis of the LED chip structure andcomponents as well as the influence factors of the SIMS depth resolution, we usedCMP technology on the processing of the LED chip with vertical structure. At first,thinning and flattening the LED chip by using polishing agent, then the surface of theprepared samples were observed and analyzed by Olympus microscope, and selectedthe samples with better surface quality; measuring surface roughness with theprofilometer and finding out the area with relatively small roughness, finally the areawere analyzed by SIMS depth profiling. This study obtained these following results：(1)The roughness of the samples、Sputtering depth and the broadening effectduring the testing process will have a great effect on the SIMS depth profilinganalysis, therefore, in order to improve the preparation of test results, we need toimprove the test conditions and optimize the samples to meet the requirements ofSIMS analysis;(2)LED chip cannot be analyzed directly by SIMS because of its special structure.Especially the LED chip with vertical structure, its surface has a rough treatment andthe n-GaN is relatively thick, so we need to thin and flat the LED chip before SIMSdepth profilling;(3)GaN has high hardness and brittleness, and not easily soluble in acid andalkali, it can not be effectively processed by general ultra-precision methods, but CMPmethod can be used to make the GaN to achieve a smooth surface flatness;(4)Processing of LED chip is very complex by using CMP, in order to improvethe quality of the sample after processing, the whole process should use progressiveand advanced processing methods: rough polishing-fine cast-fine polishing;(5)After CMP processing, the LED chip has different surface quality, we need toselect the samples with better surface quality by Olypmus microscope, here on the"good surface quality" is defined as the sample surface is intact or exists a little crack;(6)Finding the area with relatively small roughness with the Profilometer isfeasible, which is verified by the results of SIMS analysis.