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標題: | 基於高解析度光學同調斷層掃描術應用於化合物半導體之非破壞性檢測 Non-destructive Inspection of the Compound Semiconductors using High-resolution Optical Coherence Tomography |
作者: | 曾柏皓 Po-Hao Tseng |
指導教授: | 李翔傑 Hsiang-Chieh Lee |
關鍵字: | 光學同調斷層掃描術,高解析度,化合物半導體,缺陷偵測,半導體檢測,三維成像, optical coherence tomography (OCT),high resolution,compound semiconductor,defect inspection,semiconductor inspection,three-dimensional imaging, |
出版年 : | 2023 |
學位: | 碩士 |
摘要: | 隨著淨零碳排放的熱潮,電動車已成為各國發展的重點。而電動車需要功率元件,也就是逆變器,將低壓電轉換至電器所需要的電壓。相較於矽基功率元件,化合物半導體當中的碳化矽功率元件可以提供更高的轉換效率。因此,目前各國對於碳化矽功率元件的需求日益增加。然而,碳化矽當中的缺陷除了會降低這些功率元件的轉換效率,還可能會使元件產生漏電流而導致溫度過高引發危險。為了在增加產能的同時有效的降低缺陷的產生,在晶圓製造的階段就必須進行快速的檢測。而光學同調斷層掃描術(Optical coherence tomography, OCT)具有非破壞性、快速、微米級解析度以及三維成像等優點,相較於現今產線上常用的光學顯微鏡(Optical microscopy, OM)具有能夠解析樣品內部結構的能力。
在本篇論文當中,我們希望能透過OCT掃描碳化矽晶圓當中的數種不同缺陷,包含大型凹痕(Macropit)、疊差(Stacking fault)、微管(Micropipe)以及夾雜粒子(Particle inclusion)等種類,並透過量化分析取得各個缺陷在橫向上的尺寸、所在深度以及在三維空間中的分布,藉以證明OCT具有在半導體產業中發展的潛力。為此我們取得了三片6吋以及兩片4吋的碳化矽晶圓,並使用專業儀器對晶圓中的缺陷進行定位。同時,我們透過光學以及光機構模擬設計了OCT系統的樣品端並結合可以調整入射角度的尺寸的載物平台,以建立一套具有高解析度且掃頻式光學同調斷層掃描系統(Swept-source OCT, SS-OCT)來對缺陷進行掃描分析。該系統所使用的光源中心波長為1310 nm、光譜頻寬為120 nm且掃描頻率為20 kHz。其在空氣中的軸向解析度為11.213 μm,而軸向解析度為4.38 μm。最大可掃描範圍為2.155 mm × 2.155 mm。 基於本論文所得到的結果,我們預期更進一步改良樣品端的光學設計,將消色差雙合透鏡組改為掃描透鏡,以在減少樣品端長度的同時提升工作距離,並且避免透鏡像差降低影像品質。在提升品質後,我們還可以進一步套用數位再聚焦(Computational refocusing, CR)演算法。透過CR演算法補償OCT正向影像當中來自透鏡的轉換函數(Transfer function),藉以增加由於高解析度所帶來淺景深,以助於OCT在半導體檢測中的實行性。 With the trend of the net zero emissions, electric vehicles have become the focus of development for countries worldwide. The electric vehicles require the power device, or inverter, to convert the low-voltage electricity into the voltage required by electronic devices. Compare to silicon-based power devices, silicon carbide (SiC) power devices can provide higher conversion efficiency. Therefore, the demand for SiC power devices is increasing in various countries. However, defects in SiC not only reduce the conversion efficiency of the power devices but may also cause leakage current and increase the temperature, which may induce danger. In order to increase the yield, i.e. effectively reduce the occurrence of defects while increasing the production capacity, rapid inspection during the wafer manufacturing stage is necessary. Optical coherence tomography (OCT) has the advantages of non-destructive inspection, high speed, micrometer-level resolution, and three-dimensional imaging. It is capable of resolving internal structure of samples, which makes it superior to the commonly used inspection technique, optical microscopy (OM), in current in-line inspection. In this paper, we aim to use OCT to scan various types of defects in SiC wafers, including macro pits, stacking faults, micropipes, and particle inclusions. To demonstrate the potential of OCT in the semiconductor industry, we intend to obtain the lateral dimensions, depths, and spatial distributions of each defect in three-dimensional space through quantitative analysis. For this purpose, we obtained three 6-inch and two 4-inch SiC wafers and used specialized equipment to locate the defects in the wafers. Simultaneously, we designed the sample arm of the OCT system through optical and optical-mechanical simulations. We combined it with a translation stage that can adjust incident angles to establish a high-resolution swept-source OCT (SS-OCT) system for scanning and analyzing the defects. The system utilizes a swept source with a central wavelength of 1310 nm, spectral bandwidth of 120 nm, and a scanning rate of 20 kHz. The axial and lateral resolutions are 11.213 μm (in air) and 4.38 μm. The maximum scanning range is 2.155 mm × 2.155 mm. Based on the results obtained in this research, we anticipate further improvements in the optical design of the sample arm. We propose replacing the achromatic doublet lens with a scanning lens to reduce the length of the sample arm as well as to increase the working distance and avoid lens aberrations that may degrade image quality. After improving the image quality, we can further apply the Computational refocusing (CR) algorithm. By applying the CR algorithm, the transfer function introduced by the lens in OCT enface images will be compensated, which will increase the depth of field (DOF) caused by high resolution. This will aid in the feasibility of using OCT for semiconductor inspection. |
URI: | http://tdr.lib.ntu.edu.tw/jspui/handle/123456789/90697 |
DOI: | 10.6342/NTU202302484 |
全文授權: | 同意授權(限校園內公開) |
顯示於系所單位: | 光電工程學研究所 |
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