A NOVEL HIGH-RESOLUTION SCANNING ELECTRON-MICROSCOPE FOR THE SURFACE-ANALYSIS OF HIGH-ASPECT-RATION 3-DIMENSIONAL STRUCTURES

A scanning electron microscope (SEM) with an immersion-type objective lens has been developed. The objective lens generates a strong axial magnetic field of about 0.17 T at a wafer surface and has a very short focal length of about 2.5 mm. The SEM realizes an image resolution of 30 angstrom at 0.7 kV accelerating voltage. The capability to observe the bottom of a trench with a 5.3-mu-m depth and 0.55-mu-m width and that of a hole with a 0.46-mu-m diameter and 1.6-mu-m depth has been demonstrated at a low accelerating voltage of 0.5 approximately 1.5 kV. A good measurement reproduceability of 5 nm/3-sigma (sigma: standard deviation) has been achieved in the measurement of the 0.55-mu-m SiO2 line pattern on the bottom of a trench of 0.55-mu-m width and 5.3-mu-m depth. The SEM has been applied to the observation of 64MDRAM cell patterns with a 0.4-mu-m design rule.