從散射測量對微影線上製程控制的研究

Abstract

隨著微影技術的不斷地向更小線寬發展，CD 量測的準確性以及製程線寬的控制，變的越來越重要；提高晶圓內CD的一致性同時也有助於提高量產的良率。然而，自光阻從原來的DNQ/Novolak光阻轉換成專為Deep UV 設計的CAR( Chemical Amplified Resist )光阻後，PEB( Post Exposure Bake )儼然成了目前微影製程中控制線寬一致性的關鍵因素。 對於奈米微影製程¬而言，傳統CD的量測方式似乎接近半導體元件解析度的有效極限；以臨界尺寸掃描電子顯微鏡(CD-SEM)的量測方式，是由上而下的觀測，並無法提供很詳細的邊緣和底部的特徵數據；除非以破壞性的切片方式，否則無法量得縱深的數據；但這種方法不及時且費時費力。因此隨著半導體技術的進步，量測上的需求，發展出基於散射測量法(Scatterometry) 的光學參數測量法成為新一代的CD測量方法。

目前控制PEB溫度的關鍵在於熱板的控溫，但是不論熱板溫度的校正誤差有多精確，似乎仍無法滿足目前奈米微影對CDU的嚴苛要求；之前也有人嘗試以顯影後的CD值來作PEB熱板的調校，以便將晶圓內CD的一致性降到更好的境界；這些PEB熱板調校的CD值量測，仍然是使用SEM來做量測，因此在量測的點數與時間上，似乎無法達到即時；隨著光學參數測量法的引進，由於其準確、快速及能提供更詳細數據的特性，似乎對以顯影後CD值來調教PEB溫度的方式，有了新的方向。本論文嘗試探討散射測量法(Scatterometry) 的光學參數測量法與 SEM的匹配性，並使用整合於Track機台中光學量測技術，搭配CD最佳化的運算軟體，利用其即時、便利的特性，直接對PEB熱板作溫度的回饋補償，以期能得到更佳的晶圓內CD的一致性。

As lithography technology keep shrinking CD size, the accuracy of CD measurement and process control become more and more important. Improve within wafer CDU also can improve product yield. After photo-resist from DNQ/Nolvolak resist change to CAR (Chemical Amplified Resist), PEB(Post Exposure bake) become the key factor of litho CDU control. For nano-node lithography, traditional CD measurement methodology looks meet the resolution limit of semiconductor component. CD-SEM is from top to bottom measurement, can not provide detail profile information. Unless use cross section method, or can not show the depth data. But this way need to damage wafer also waste a lot time. As the semiconductor technology development, optical scatterometry will be next generation of CD measurement. Currently, the key point of PEB temperature is hot plate thermal controller. But no matter how accurate of hot plate temperature control is, seem still not meet the CDU requirement of nano-lithography. Someone tried to calibrate the PEB temperature by using development CD, in order to make the within wafer CDU better. Whatever, these methods are using SEM by CD measurement. Still need lot measurement point and time for data accuracy. As the optical CD technology improve, the features of accuracy、quickly and more profile information maybe provide the new direction of PEB temperature calibration by development CD. In this paper, the feasibility of improving the within wafer CDU will be discuss by using integrated scatterometry. The target of the works are optical CD match with SEM and PEB temperature calibration by integrated scatterometry for within wafer CDU best.