Eddy Current Sensor for Precise Semiconductor Polishing
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Summary
Problems
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 solutions
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.
TRIZ Analysis
Specific contradictions:
General conflict description:
Principle concept:
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
Why choose this principle:
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.
Principle concept:
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
Why choose this principle:
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.
Application Domain
Data Source
AI summary:
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.
Abstract
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.