Sidewall profile reconstruction of microstructures with high aspect ratio based on near-infrared light scanning interferometry

Jianhua Shi,Bingchen Han

doi:10.1063/1.5049494

Jianhua Shi, Bingchen Han

Open Access

https://doi.org/10.1063/1.5049494

Copy DOI

Abstract

Sidewall profile reconstruction of microstructures with the high aspect ratio is a problem urgently to be solved in MEMS field. In this paper, a measuring method based on near-infrared light scanning interferometry (NILSI) is presented according to the transmission principle of semiconductor materials in the infrared light region. The NILSI is extended from the white light to near-infrared light and from surface profile reconstruction to sidewall profile reconstruction. The NILSI system is constituted by a near-infrared light source, an interference microscope, infrared CCD, piezoelectric ceramics (PZT) with high accuracy and the data acquisition system. The test sample is taken from GaAs microstructures with high aspect ratio and made by two different height steps for measuring with different typical testing equipment. Near-infrared light vertical scanning interference (NILVSI) is improved to compensate optical path difference (OPD) and the large surface roughness. The sidewall profile of the sample is obtained and compared with that of scanning electron microscopy (SEM) and white light scanning interferometry (WLSI). Test results demonstrate that the steps have 2.115 μm and 0.762 μm relative heights and 1.34 % and 2.14% relative errors respectively. There is a good agreement with the results of SEM and WLSI. The system can reconstruct the sidewall profile of microstructures with high aspect ratio.

Highlights

In recent years, the microstructures with high aspect ratio have the advantages of high sensitivity and large displacement which has been widely used in the field of MEMS.[1]
In order to compare with different typical testing equipment, test sample is taken from GaAs microstructures with high aspect ratio and made by two different height steps which is shown in right picture of Fig. 1
The results prove that this system can measure the sidewall profile of the microstructures with high aspect ratio

Summary

Introduction

The microstructures with high aspect ratio have the advantages of high sensitivity and large displacement which has been widely used in the field of MEMS.[1]. It is a problem how to realize non-destructive real-time online three-dimensional reconstruction of the sidewall profile.[2] At present, there are three kinds of instruments for measuring the three-dimensional profile of microstructures: Scanning Electron Microscope[3,4] (SEM), Atomic Force Microscope[5,6] (AFM), white light scanning interferometer (WLSI).[7,8] When SEM tests the microstructures with the high aspect ratio, it is necessary to cut the microstructures into the sectioned sample which is a method of damage, and the test time is long and costly. For sidewall profile measurement of the microstructures with high aspect ratio, on the one hand the white light diffraction is more serious. The light can’t entirely through the narrow slit because of the existed angle between the light and the object when measuring, so it is difficult to measure the sidewall profile.[9,10] From what has been discussed above, based on

Methods

Results

Conclusion