LED晶粒瑕疵自動光學檢測系統研發

An Automatic Optical Inspection System Development for LED Chip Defects

陳銘福(Ming-Fu Chen) ； 周志忠(Chih-Chung Chou) ； 陳志文(Chih-Wen Chen) ； 翁睿謙(Rui-Cian Weng) ； 黃鴻基(Hung-Ji Huang)

《科儀新知》 202期 (2015/03) Pp. 6-15

摘要

依據LED晶粒製造廠商的需求設計一種運用高空間解析光學取像模組，配合影像處理與檢測演算法的開發，以研發一種檢測LED晶粒瑕疵的自動光學檢測系統，以精確檢測晶粒上大於規格的瑕疵。檢測系統由影像擷取裝置、檢測定位平台、晶粒瑕疵檢測、操作管理、晶圓定位及取像規劃等次系統或模組構成，藉以達成可自動化檢測LED晶粒表面包含電極斷裂缺損與邊緣缺裂等瑕疵的功能與目標。本檢測系統新設計一組具有優於2 μm空間解析力與寬FOV的光機取像模組，配合獨特的整合照明亮度調整的自動對焦方法，受檢晶圓置入晶圓吸盤中央區之後，可快速的完成光機取像模組的合適照明亮度調整及精確對焦，以利於晶圓定位及取得品質良好的晶粒影像。完成對焦後可進行自動晶圓定位程序，故以光機取像模組搭配檢測定位平台的移動，以影像空間頻率域為基礎的對位法所開發的自動晶圓定位方法，達成自動化的晶圓精確對位，及完成取像規劃，接著即可進行晶圓的連續取像及晶粒瑕疵檢測。目前所研發的LED自動光學檢測系統已完成原型機的製作與初步測試，已可達成原研發計畫的功能目標，可對未劈裂的Wafer form晶圓進行精確對位、擷取影像及瑕疵檢測。但由於合作廠商希望亦能對已劈裂開並置放於藍膜上的Chip form晶粒能進行對位取像與檢測，故亦已完成此項功能。但所研發的原型機尚有若干議題與挑戰需於後續提出分析與解決方法，以滿足合作廠商的實際使用需求，例如LED晶粒的電極線越來越細，需再開發具有更高空間解析力的光機取像模組，以提高其表面瑕疵的檢測正確性。對於在晶圓邊緣有未劈裂開LED晶粒的Chip form晶圓，在進行檢測取像時會有定位偏移的問題等。

並列摘要

According to collaborated customer's requirements, an optical inspection system for LED chip defects on wafers is developed to identify defects with size of greater than evaluated criteria. Inspection system is composed of an image acquisition device with high spatial resolution, a software package for image pre-processing and defect inspection, an inspection platform for precisely positioning. This LED chip defects inspection system consisted of an image acquisition device and a positioning platform, and modules of defect inspection, wafer positioning, image acquisition planning, and operations and management to achieve the capabilities and targets of automatically inspecting LED chip defects of electrode disconnection and flaws, and boundary collapses. Inspection system has a new designed opto-mechanical device with a spatial resolution of greater than 2 μm and wide FOV and integrated with a unique algorithm of auto-focusing integrated with illumination adjustment. Then the precisely focusing with suitable illumination for opto-mechanical device can be completed efficiently for wafer positioning and acquiring chip images with good quality. Thus based on the image acquisition device and the positioning platform, automatically wafer positioning can be completed precisely based on the registration methods in spatial frequency domain of acquired images. Therefore, image acquisition planning can be completed as well for continuous image acquisition and the chip defects inspection. This prototype of LED chip AOI system has been developed and tested preliminarily. The goals of our R&D project can be achieved to conduct the precisely wafer positioning, image acquisition and defect inspection for non-split LED wafers. But cooperative customer hoped this system can also inspect the chip defects for chip form LED wafers that have been split and plastered on bluefilm. And this requirement was accomplished as well. But this prototypical inspection system still has a few of issues and challenges need to be solved to meet customer's practical usages. For example, the spatial resolution of opto-mechanical device needs to be raised for LED chips with more narrow electrodes (less than 4 μm) to enhance the correctness of inspection. When performs the image acquisition for chip form LED inspection, there's the problem of positioning deviation at wafer boundary regions with un-split LED chips.