本研究成功開發一套創新的全域式晶圓翹曲量測系統，用以即時偵測待測晶圓的翹曲值及其表面形貌。此套晶圓翹曲量測技術以「疊紋」為技術核心，結合光柵自成像效應、瞬時相移法及四步移相法等設計概念進行開發，使系統具備高解析度、高穩定度及全域式的偵測能力。藉由全域式的光路設計使一雷射光源通過擴束系統後，形成一道直徑兩吋(2″)的準直光束，而後入射至待測晶圓表面，此道準直光束被待測晶圓表面反射之後，將依序穿透兩片自製的同心圓狀光柵，再聚焦於CCD攝影機上進行影像擷取，最後透過自行開發的影像分析模組計算待測晶圓之翹曲量及其表面形貌。由於兩同心圓狀光柵放置間距遵循泰柏成像定理，可使第一片光柵的影像清楚地成像於第二片光柵上，進而交疊出相對應的同心圓疊紋條紋影像，此疊紋條紋影像之週期大小可藉由控制兩光柵影像之週期來調整。當待測晶圓發生翹曲時，晶圓表面各偵測點的傾斜角度變化量將載於反射準直光束之中，使同心圓疊紋條紋影像沿其徑向產生相對性橫移，透過瞬時相移法及四步移相法即可計算晶圓表面各偵測點的傾斜角度變化，將各點的傾斜角度值沿著同心圓疊紋條紋徑向進行累加，即可得到待測晶圓的翹曲值及其表面形貌。由實驗結果證明，本套全域式晶圓翹曲量測系統可精準地量測整面晶圓之翹曲變形及其表面輪廓，當待測晶圓上各偵測點之角度解析度為2µrad時，其最小可量測到之相對翹曲值約為0.04μm。此套系統可直接架設於待測設備上或腔體之外，不會影響磊晶製程品質，相較於現有的光束量測法、共焦顯微法、雷射干涉儀、陰影疊紋法、結構光法等翹曲量測技術，本技術具備全域式量測、高量測解析度、高穩定度以及高可調性等量測優勢。

A full-field wafer warpage measurement technique for measuring wafer warpage and surface topography is presented in this study. The wafer warpage measurement technique is developed based on moiré method, Talbot effect, as well as four-step phase shift method, granting it high resolution, high stability and full-field measurement capabilities. Following the full-field optical path design a laser beam is expanded into a collimated beam with a 2 inch diameter and projected onto the wafer surface. The beam is reflected by the wafer surface and forms a moiré fringe image after passing two circular gratings, which is then focused and captured on a CCD camera for computation on a self-developed image analysis module. In accordance with the Talbot effect, the distance between the two circular gratings can be arranged such that the diffraction image of the first grating can be clearly projected onto the second one, thus creating the corresponding circular moiré pattern. The periodic variation of the pattern can be adjusted by altering the period of the two gratings. When wafer warpage occurs, changes in the slope of each detection point will be reflected in the reflected beam, resulting in a corresponding linear shift in the radial direction of the circular moiré pattern. The change in the slope of each detection point can be calculated via the instantaneous phase-shift method and the four-step phase-shift method, and by arranging the angular value of each point along the radii of the circular gratings, the warpage value and surface topography of the wafer can be obtained. The results of the experiment show that this technique can accurately measure wafer warpage and its surface topography, and that when the angular resolution of the detection points on the tested wafer is 2 μrad the minimum relative warpage value that can be detected is approximately 0.04 μm. The structure can be mounted directly on the equipment under test or the outside of the testing chamber, avoiding adverse effects on the quality of epitaxial wafer fabrication. Compared to current warpage measurement methods such as the beam optical method, confocal microscopy, laser interferometry, shadow moiré method, and structured light method, this technique has the advantage of full-field measurement, high resolution, stability and adaptability.

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