CMP Platen Edge-Shape Control With Annular Pressure Chambers
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes face challenges with variations in material removal rates and thickness profiles due to inconsistencies in slurry distribution, polishing pad conditions, relative speed, and load variations, leading to non-uniformities, especially at the substrate edges.
Innovation Solution
A chemical mechanical polishing apparatus with annular chambers in the platen that control fluid pressure to flex the platen and polishing pad, allowing localized adjustment of polishing rates through controlled pressure changes in these chambers, guided by an in-situ monitoring system to ensure uniformity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP process is used, then polishing is performed across the entire substrate surface, but variations in material removal rate and thickness profile occur due to inconsistent slurry distribution, pad condition, speed, and load
Solution Approach 1:
The platen is divided into multiple independently controllable annular chambers that can be pressurized or depressurized separately. This segmentation allows different regions of the polishing pad to be biased upward or downward independently, enabling localized control of polishing rates to correct thickness profile non-uniformities in specific annular regions of the substrate.
Solution Approach 2:
The platen surface is made dynamically adjustable through the annular chambers that can change their pressure state in real-time. The flexible plate allows the platen to transition between different biasing states (upward or downward flexing) based on the detected thickness profile requirements, enabling adaptive compensation for edge region variations.
2Manufacturing precision
If the platen is made rigid for stability, then positioning precision is maintained, but localized flexing to correct edge non-uniformities cannot be achieved
Solution Approach 1:
The platen is designed with a flexible plate that allows localized flexing in specific regions while maintaining overall structural integrity. The annular chambers enable selective biasing of particular pad regions without affecting the entire platen, achieving local adaptation while preserving global stability.
Solution Approach 2:
A flexible plate is used as the platen structure, allowing it to deflect locally in response to pressure changes in the annular chambers. This flexibility enables the platen to adapt its shape locally to correct edge non-uniformities while maintaining sufficient rigidity for stable operation.
3Manufacturing precision
If annular chambers are added to control platen shape, then localized polishing rate control is achieved, but device complexity increases
Solution Approach 1:
Fluid pressure is used to control the biasing of pad regions through the annular chambers. By introducing or removing fluid pressure in specific chambers, the system can selectively flex the platen and polishing pad in targeted annular regions, enabling precise control of polishing rates without complex mechanical actuation systems.
4Productivity
If the polishing pad is biased upward in edge regions, then material removal rate increases, but over-polishing may occur if not precisely controlled
Solution Approach 1:
The system uses optical monitoring to detect the thickness profile of the substrate in real-time and provides feedback to the controller. Based on this feedback, the controller adjusts the pressure in the annular chambers to flex the platen and polishing pad, dynamically controlling the polishing rate to achieve uniform thickness without over or under-polishing.
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
The solution enables precise control over polishing rates, reducing within-wafer and wafer-to-wafer non-uniformities by compensating for edge region thickness variations, enhancing polishing specificity and efficiency.
Implementation Method 1
A fluid pressure within each annular chamber is controlled to flex, e.g., vertically bias, a region of the platen above the corresponding chamber
Implementation Method 2
the platen having an annular chamber below and separated from a portion of an upper surface of the platen by a plate that is sufficiently flexible to deflect under a change of a pressure in the annular chamber
Implementation Method 3
chemical mechanical polishing apparatus having a platen having an upper surface to support a polishing pad... a carrier head to hold a surface of a substrate against the polishing pad... so as to polish an overlying layer on the substrate
Data Source
AI summary
Disclosed herein is a chemical mechanical polishing apparatus, including a platen having an upper surface to support a polishing pad, the platen having an annular chamber below and separated from a portion of an upper surface of the platen by a plate that is sufficiently flexible to deflect under a change of a pressure in the annular chamber, the platen having a channel fluidically connecting the annular chamber to a port in the platen; a pressure source coupled to the port to control the pressure in the annular chamber; a carrier head to hold a surface of a substrate against the polishing pad; and a motor to generate relative motion between the platen and the carrier head so as to polish an overlying layer on the substrate.