Rapid 3D-Imaging of Semiconductor Chips Using THz Time-of-Flight Technique

Jong Hyuk Yim,Suyoung Cho,Jangsun Kim,Yeong Hwan Ahn,Yiseob Kim,Su-Yeon Kim

doi:10.3390/app11114770

Abstract

In this study, we developed a rapid three-dimensional (3D) time-of-flight imaging tool for inspection of packaged semiconductor chips, using terahertz (THz) time-domain spectroscopy techniques. A high-speed THz system based on the optical sampling by cavity tuning technique is incorporated with a 2-axis galvano scanner to deliver a scanning speed of more than 100 Hz/pixel with a signal-to-noise ratio larger than 20 dB. Through the use of the Hilbert transformation, we reconstruct the 3D structure of the packaged chip in a nondestructive manner. Additionally, the use of frequency-selective imaging allows us to manipulate image resolution; the higher resolution was obtained when monitored using the higher frequency component. Further, using phase information, we were able to detect and identify defects in the packaged chip, such as the delamination area and epoxy-rich regions.

Highlights

THz waves are transparent to nonconductive materials frequently used for the encapsulation of devices such as semiconducting chips; THz imaging allows us to characterize the internal structures of objects in a nondestructive manner [7,8,9,10,11,12,13,14,15,16,17]
Coherent THz tomography based on frequency-modulated CW (FMCW) methods have been developed using a tunable source or ensemble source, they are limited in terms of the depth and longitudinal resolution in general [25,26,27]
We report high-speed imaging for packaged integrated circuit (IC) inspection with a high temporal resolution based on the THz–time-domain spectroscopy (TDS) technique using the optical sampling by cavity tuning (OSCAT)

Summary

Introduction

As two-dimensional (2D) array detectors are not available, most THz TOF imaging systems require sample scanning, followed by reconstruction of a series of singlepoint measurements for reflected or transmitted waves. Novel THz–TDS systems were introduced commercially based on compact femtosecond fiber laser technology without the mechanical delay stage. Artificial defects in glass fiber reinforced polymers have been imaged, proving their potential use for rapid, nondestructive inspection of various materials, components, and systems. A rapid imaging technique based on the galvano scanning system has not been introduced for inspection of defects in packaged chips, packaged chips have been studied with the THz–TDS system using relatively slow sample scanning methods [3]. The reconstruction of the 3D plots allows us to identify defects in the packaging, which is not possible using 2D integrated images

Experimental Setup

Discussion

Conclusions