Secondary Electron Image Profiles Using Bias Voltage Technique In Deep Contact Hole Yeong-Uk Ko *a , David C. Joy a,b and Neal Sullivan c , Martin E. Mastovich c a EM Facility, Univ. of Tennessee, Knoxville, TN 37996-0810 b Oak Ridge National Laboratory, Oak Ridge, TN 37813-6064 c Schlumberger, Concord, MA 01742 ABSTRACT Charging effects on secondary electron (SE) profiles with bias voltage in deep contact holes are investigated. We show first in detail the SE beam profiles for operating conditions such as scanning time, current and landing energy, the brightness of the bottom of the contact hole depends on the charge of SE yield with incident energy. We conclude that we can enhance the contrast of the beam profile by optimizing the applied bias voltage. KEYWORD: deep contact hole, secondary electron, charging, bias voltage technique 1. INTRODUCTION As the size of semiconductor devices shrinks, the cost of wafer fabrication increases and it becomes more important to use non-destructive techniques to monitor all aspect production. Though current CD metrology tools can give reliable, in-line, measurement of lines, spaces, pitches and contact holes, information on sidewall angle or resist profiles is needed for quality control, which is a time consuming and tedious process. It is also important to determine if the deep contact hole is open or closed by analyzing the SEM signal collected from the bottom of the contact 1 . To enhance this bottom image, the technique of applying a high bias voltage between objective lens and sample ground has been developed 2-3 . But it is not clear what is the mechanism of extraction of secondary electrons (SEs) from the bottom and it is needed to know the degree of improvement quantitatively using this technique. Ose et al used electron reflection model that considered the SE bouncing off the wall 3 . In this work we use Monte Carlo simulations, which use actual calculation of the trajectories of numerous electrons, for modeling the charging phenomena and for calculation of the resultant SE beam profile in contact hole. Firstly we calculate the spatial distribution of charges when e-beams are incident onto the sample. A potential results because positive and negative charges are placed in different areas and current flows as a result of EBIC and therefore the potential is decreased. We can then calculate the ejected SE trajectories from this potential distribution. We compute quantitatively image profiles error in various operating condition and dimensions of contact hole. Used material and method will be showed in next section. 2. SIMULATION MODEL We have used two kinds of samples, etched oxide/Si and UV5/AR/Si. We firstly set standard condition for our calculation to compare with those from changing parameters. The thicknesses of specimen are 0.7 ? m and 0.65 ? m and the diameters are 0.45 ? m and 0.2 ? m for each etched oxide/Si and UV5/AR/Si sample. Fig. 1 shows the configuration of standard condition of etched oxide. Figures in parenthesis are for only the case of UV5/AR/Si. The scanned area is 2.0 ? m ? 2.0 ? m. For the operating condition, we have changed the parameters to identify their