Polishing Apparatus Torque Current Model for Hard Mask Film
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Solution Overview
Problem
Accurately monitoring the thickness of thin hard mask films during polishing in multi-level interconnect structures is challenging due to their low thickness and mechanical properties, making it difficult to detect the polishing end point effectively.
Innovation Solution
A polishing apparatus and method that utilize a model equation incorporating the integrated value of torque current and cumulative operating time of a dresser to estimate the removal amount of the object material, allowing for precise control of the polishing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If optical sensor or eddy current sensor is used to monitor film thickness during polishing, then real-time monitoring capability is provided, but accurate monitoring of thin hard mask films (50-60 nm oxide films) cannot be achieved
Solution Approach 1:
The patent introduces a dresser as an intermediary device that modifies the polishing pad surface to create a controlled polishing environment. The dresser prepares the polishing surface to enable accurate thickness monitoring by ensuring consistent contact and removal rates, which indirectly improves the effectiveness of thickness monitoring during polishing of thin hard mask films
Solution Approach 2:
The patent changes the parameters of the polishing system by introducing a dresser that modifies the polishing pad's surface properties. This parameter change enables more accurate monitoring of thin film removal by creating consistent polishing conditions that make thickness changes detectable even for 50-60 nm oxide films
2Productivity
If polishing is continued to remove all unwanted films, then complete removal of barrier film is achieved, but hard mask film is accidentally removed which compromises substrate integrity
Solution Approach 1:
The patent implements a feedback mechanism by continuously monitoring film thickness during polishing and comparing it against target values. When the hard mask film thickness reaches the predetermined threshold (e.g., 10 nm), the system automatically stops polishing, preventing over-removal and compromising substrate integrity while maintaining high productivity
Solution Approach 2:
The patent performs preliminary action by pre-establishing the target thickness value for the hard mask film before polishing begins. This predetermined parameter guides the polishing process and enables automatic stoppage at the correct point, ensuring both complete removal of barrier film and preservation of hard mask film integrity
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
Enables accurate estimation of the removal amount, ensuring the polishing process is stopped at the desired time, thereby maintaining the integrity of the hard mask film and achieving precise control over the multi-level interconnect structure.
Implementation Method 1
a motor configured to drive the polishing table
Implementation Method 2
a polishing apparatus including a polishing table for holding a polishing pad having a polishing surface
Data Source
AI summary
An apparatus polishes an object material such as a film on a substrate. This apparatus includes a polishing table for holding a polishing pad having a polishing surface, a motor configured to drive the polishing table, a holding mechanism configured to hold a substrate having an object material to be polished and to press the substrate against the polishing surface, a dresser configured to dress the polishing surface, and a monitoring unit configured to monitor a removal amount of the object material. The monitoring unit is operable to calculate the removal amount of the object material using a model equation containing a variable representing an integrated value of a torque current of the motor when polishing the object material and a variable representing a cumulative operating time of the dresser.