Maximum Permissible EB Acceleration Voltage for SEM-Based Inspection Before Electrical Characterization of Advanced MOS

The electron beam based inspection instruments such as the review-SEM are widely used to analyze defects during manufacturing and failure analysis of scaled devices. Nano-probers used for scaled device analysis also employs SEM for probe guidance. However, electron beam (EB) induced damages are increasing with the scaling. A higher SEM resolution induces device damage. To avoid the damage, the acceleration voltage should be lower. Several generations of scaled devices from 350nm to 65nm were examined, and critical EB acceleration voltage that induced device degradation was quantitatively evaluated. The determination mechanism of permissible electron beam acceleration voltage is clarified.

Introduction

Electron beam based inspection methods such as CD-SEM (Critical Dimension SEM), and Review-SEM have become indispensable in the manufacturing and development area [1]. Also, the Nano-prober with SEM guidance has become important in the failure analysis area to evaluate the localized device in the actual LSI [2]. However, these instruments should be used without inducing gate oxide damages by EB, which is known to induce device degradation [3]–[4]. For scaled devices, permissible acceleration voltage and its relation to the device structure have not been reported. A higher SEM resolution induces device damage. To avoid the damage, the acceleration voltage should be lower. In the present work, we prepared scaled devices with generations from 350nm to 65nm, and evaluated device degradation for several accleration voltages. Indeed, the maximum possible accellerating voltage reduces with smaller device technologies. The determination mechanism of the voltage is discussed.