Surface Roughness Measurement of a Semi-Conductor Wafer Using Laser Scattering Technique

Abstract

Light scattering is a non-contact technique which can be used for characterizing the topography of smooth reflecting surfaces. A technique which incorporates an integrated laser scattering model for surface roughness measurement of a semi-conductor wafer has been developed. The technique employs a He-Ne laser and incorporates various optical components (Fig. 1) to record surface roughness in the nanometer range with a high degree of accuracy. Theory of the technique and the experimental program are described. The results obtained show excellent agreement with method using the atomic force microscope with only minor discrepancy. This is a significant improvement over the conventional stylus methods, In addition, unlike previous laser scattering method which uses a spherical arrangement to record diffused light, the proposed technique detects reflected light normal to the test surface and hence resulting in a simpler and more stable optical arrangement. Using the proposed optical arrangement, accurate and repeatable measurement of a semiconductor wafer roughness of in the nanometer range can be readily obtained.