Technique of electrical beam treatment leading to an accurate and reliable critical dimension metrology measurement on a postetch layer

Abstract

Accurate and reliable Critical Dimension (CD) measurement is one of the most important goals of CD metrology. Today, most CD measurements are performed utilizing the Scanning Electron Microscope (SEM). One of the most commonly employed measurement detection algorithms is the Threshold method. This method is most useful for measuring CD when the structure being measured consistently produces stable peaks in the secondary electron induced image intensity profile'3. However, the intensity profile becomes more complicated when there are multiple peaks whose peak heights are neither stable nor fixed in position. In this case, accurate and reliable CD measurements are difficult to achieve. In this paper, a novel technique of pre-dose and re-dose electrical beam treatment will be described. The technique is effective in producing reliable intensity profiles resulting in accurate CD measurements, and the recipe developed using the technique runs fully automated. The technique has been applied in our factory with success.