CMP Pressure Chamber Control for Film Thickness Uniformity
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Solution Overview
Problem
Conventional polishing methods struggle to precisely control film thickness profiles during chemical mechanical polishing (CMP) due to variations in substrate film thickness, polishing conditions, and pad conditions, leading to difficulties in maintaining film thickness within the required allowable range.
Innovation Solution
A polishing apparatus and method utilizing a substrate holder with an elastic membrane forming pressure chambers, a retainer ring, and a controller that adjusts pressures and polishing times based on a response model and optimization calculations to achieve a desired film thickness profile, considering variations in pressure and local loads.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional polishing method using film thickness sensor is used, then polishing process is simple, but film thickness control precision deteriorates and cannot maintain film thickness within allowable range
Solution Approach 1:
The polishing head is divided into multiple pressure chambers (first, second, third pressure chambers) that can independently control pressure in different regions of the substrate. This segmentation allows localized pressure adjustment to compensate for thickness variations across the substrate surface, improving film thickness control precision without requiring complete system redesign.
Solution Approach 2:
Different pressure values are applied to different regions of the substrate through the multiple pressure chambers. The controller adjusts pressure locally in each region based on thickness measurements, allowing precise control of film thickness in specific areas rather than uniform pressure across the entire substrate.
2Manufacturing precision
If single pressure chamber is used, then device structure is simple, but ability to control thickness profile across different substrate areas deteriorates
Solution Approach 1:
The pressure control system is segmented into multiple independent pressure chambers, each capable of applying different pressure values to different regions of the substrate. This enables the system to address thickness profile variations across the substrate by applying localized pressure adjustments in each chamber region.
Solution Approach 2:
The pressure values in each pressure chamber are dynamically adjusted during the polishing process based on real-time thickness measurements and control algorithms. This dynamic pressure control allows the system to adapt to varying thickness profiles and maintain precise control throughout polishing.
3Productivity
If polishing pressure is increased to improve polishing rate, then productivity increases, but uniformity of film thickness deteriorates due to friction force variations
Solution Approach 1:
Different pressure values are applied to different regions of the substrate through the multiple pressure chambers. This local quality approach allows high pressure to be applied where polishing rate needs improvement while maintaining lower pressure in regions where uniformity is critical, thereby achieving both productivity and precision goals simultaneously.
Solution Approach 2:
The pressure parameter is changed across different regions of the substrate rather than maintaining a uniform pressure value. By varying pressure parameters locally, the system can optimize polishing rate in specific areas while maintaining film thickness uniformity in other areas, resolving the contradiction between productivity and precision.
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 of film thickness profiles by optimizing polishing recipes, minimizing deviations from target thickness, and improving uniformity and yield in semiconductor device manufacturing.
Implementation Method 1
a substrate holder for pressing a substrate against the polishing pad... an elastic membrane film to form a plurality of pressure chambers for pressing the substrate
Implementation Method 2
supplying a polishing liquid containing abrasive grains, such as silica (SiO2), onto the polishing pad... the surface of the wafer is polished to a flat finish by a combination of a chemical action of the slurry and a mechanical action of abrasive grains
Implementation Method 3
the surface of the wafer is polished to a flat finish by a combination of a chemical action of the slurry and a mechanical action of abrasive grains
Implementation Method 4
the surface of the substrate is brought into contact with the rotating polishing pad, and thus a friction force is exerted on the substrate
Data Source
AI summary
A polishing apparatus capable of obtaining a desired film thickness profile is disclosed. The polishing apparatus includes: a polishing unit; a film thickness measuring device for measuring a film thickness profile of a substrate; and a controller for controlling at least operations of the polishing unit and the film thickness measuring device. The controller stores in advance a response model which is created by taking into consideration variation in an amount of polishing between monitored areas of the substrate due to variations in a pressure of a pressurized fluid supplied to each of pressure chambers. Further, the controller obtains a film thickness profile of the substrate before polishing by use of a film thickness measuring device, and causes the substrate to be polished with an optimized polishing recipe created based on the response model and a target polishing amount, which is a difference between the film thickness profile of the substrate before polishing and the target film thickness of the substrate. A next substrate is polished with a new optimized polishing recipe which is created based on a target polishing amount of the next substrate and a response model corrected by use of the optimized polishing recipe and film thickness profiles of the substrate before and after polishing.