Dynamic Pad Surface Metrology Monitoring by Swing-Arm Chromatic Confocal System

Chao-Chang A Chen,Chun-Chen Chen,Jen-Chieh Li,Yong-Jie Ciou,Wei-Cheng Liao

doi:10.3390/app11010179

Chao-Chang A Chen, Chun-Chen Chen + Show 3 more

Open Access

https://doi.org/10.3390/app11010179

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Abstract

This study aims to develop a dynamic pad monitoring system (DPMS) for measuring the surface topography of polishing pad. Chemical mechanical planarization/polishing (CMP) is a vital process in semiconductor manufacturing. The process is applied to assure the substrate wafer or thin film on wafer that has reached the required planarization after deposition for lithographic processing of the desired structures of devices. Surface properties of polishing pad have a huge influence on the material removal rate (MRR) and quality of wafer surface by CMP process. A DPMS has been developed to analyze the performance level of polishing pad for CMP. A chromatic confocal sensor is attached on a designed fixture arm to acquire pad topography data. By swing-arm motion with continuous data acquisition, the surface topography information of pad can be gathered dynamically. Measuring data are analyzed with a designed FFT filter to remove mechanical vibration and disturbance. Then the pad surface profile and groove depth can be calculated, which the pad’s index PU (pad uniformity) and PELI (pad effective lifetime index) are developed to evaluate the pad’s performance level. Finally, 50 rounds of CMP experiments have been executed to investigate the correlations of MRR and surface roughness of as-CMP wafer with pad performance. Results of this study can be used to monitor the pad dressing process and CMP parameter evaluation for production of IC devices.

Highlights

Chemical-mechanical planarization/polishing (CMP) has been known as a key process for global and local planarization in IC fabrication
Because of the urgent demands for conducting linewidth of IC device downsizing to nanometers, the stability and availability of CMP process have become critically significant [1,2] for high volume production
Some efficiency indicators of pad performance can be established with measuring the surface topography, such as roughness and bearing area ratio so that the polishing pad could be efficiently utilized [8,9,10]

Summary

Introduction

Chemical-mechanical planarization/polishing (CMP) has been known as a key process for global and local planarization in IC fabrication. A CMP tool is not capable of fully monitoring the polishing pad on-line. It only measures the groove depth and pad thickness or by empirical analysis [5,6,7]. Some efficiency indicators of pad performance can be established with measuring the surface topography, such as roughness and bearing area ratio so that the polishing pad could be efficiently utilized [8,9,10]. The asperities and groove depth of pad are gradually worn with CMP processes. As the pad topography will effectively influence the MRR and polishing results, different kinds of measuring methods are developed to monitor the change of the pad surface [11,12,13].

Experimental Method and Parameters

Findings

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