Analysis of Correlation between Pad Temperature and Asperity Angle in Chemical Mechanical Planarization

Seonho Jeong,Haedo Jeong,Jinuk Choi,Kyeongwoo Jeong

doi:10.3390/app11041507

Abstract

Chemical mechanical planarization (CMP) is a technology widely employed in device integration and planarization processes used in semiconductor fabrication. In CMP, the polishing pad plays a key role both mechanically and chemically. The surface of the pad, consisting of asperities and pores, undergoes repeated cycles of glazing induced by polishing followed by the recovery of roughness by a conditioning process applied during CMP. As a polymer material, the pad also experiences thermal expansion from changes in temperature. Such changes can be expressed in terms of surface roughness values, but these do not fully capture the actual changes to the pad surface. In this study, the change in pad temperature occurring during CMP was analyzed with regard to its effect on the asperity angle, and the influence on CMP outcome was assessed. The changes in the surface asperities according to the steady-state pad temperature were evaluated using various measurement methods. The change in pad roughness was characterized in terms of the asperity angle, and the contact state predicted according to temperature were validated by measuring the contact perimeter, the number of contact points, and related values. Through Scanning Electron Microscope (SEM) and micro-CT analysis, it was confirmed that in the continuous polishing process and the conditioning process, the changes in asperity angle due to changes in pad temperature affect the polishing outcome.

Highlights

Chemical mechanical planarization (CMP) has become an essential process in the semiconductor industry, in keeping with the industry’s trend toward increased miniaturization and higher integration
We investigate how the pad temperature changes that occur during CMP cause changes to the pad surface
A new perspective on the change in the angles of pad surface asperities occurring during the CMP process has been proposed in this paper

Summary

Introduction

Chemical mechanical planarization (CMP) has become an essential process in the semiconductor industry, in keeping with the industry’s trend toward increased miniaturization and higher integration. In CMP, material removal occurs as a result of friction between the wafer surface, the polishing pad, and the abrasive particles in the slurry under a chemical reaction caused by the chemical components of the slurry [5]. It is attached to the bottom plate, and polishing proceeds by the relative pressure caused by contact between the pad and the wafer. The pad should maintain uniform and rough contact. This can control the overall pad asperity height, minimize pad deformation, minimize the pad wear rate, and maintain the pad’s material properties [6,7,8]

Methods

Results

Conclusion