Polishing Method Using Eddy Current Sensor for Interconnect Height Control
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Solution Overview
Problem
Conventional polishing methods for semiconductor wafers face challenges in accurately terminating the polishing process for insulating films like hardmask films and metal interconnects, due to difficulties in measuring film thickness and potential photo-corrosion issues, leading to inaccuracies in interconnect resistance management.
Innovation Solution
A method utilizing an eddy current sensor to monitor the polishing state and terminate the process when a predetermined threshold is reached, allowing for precise control of the amount of insulating film removal and adjusting polishing times based on measured interconnect heights to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If an optical means is used to measure film thickness during polishing, then the insulating film thickness can be monitored, but light transmission through the film causes measurement inaccuracies and photo-corrosion of metal interconnects
Solution Approach 1:
The patent replaces the optical measurement system with an electrical measurement system. Specifically, it uses changes in electrical resistance or impedance of the metal interconnects to indirectly measure the thickness of the insulating film being polished. This substitution eliminates the harmful effects of light transmission while enabling continuous monitoring during the polishing process.
Solution Approach 2:
The patent introduces an intermediary measurement approach where instead of directly measuring the insulating film thickness optically, it measures the electrical properties of the metal interconnects which are affected by the film thickness. The change in electrical resistance serves as an intermediary indicator that correlates with the film thickness, allowing indirect measurement without exposing the film to light.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate determination of the insulating film removal and interconnect height, ensuring precise control over interconnect resistance and preventing excessive polishing, thereby enhancing the stability and accuracy of the polishing process.
Implementation Method 1
it has been found that changes in electrical resistance can be caused by presence of metal interconnects lying next to an insulating film to be polished, and a height of the metal interconnects can be determined from the changes in electrical resistance
Data Source
AI summary
A method for polishing a substrate having a metal film thereon is described. The substrate has metal interconnects formed from part of the metal film. The polishing method includes performing a first polishing process of removing the metal film, after the first polishing process, performing a second polishing process of removing the barrier film, after the second polishing process, performing a third polishing process of polishing the insulating film. During the second polishing process and the third polishing process, a polishing state of the substrate is monitored with an eddy current sensor, and the third polishing process is terminated when an output signal of the eddy current sensor reaches a predetermined threshold.