Double-Side Polishing Pad Conditioning with Variable-Thickness Tools
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Solution Overview
Problem
Existing methods for conditioning polishing pads in double-side semiconductor wafer polishing are insufficient to meet the increasing requirements for the geometry of polished wafers, particularly in achieving a planar and parallel surface without edge roll-off.
Innovation Solution
The method involves using conditioning tools and spacers with external teeth, where the thickness of the conditioning tools differs from the spacers, to create a varying polishing gap width in the radial direction by generating material abrasion on the polishing pads during a revolving and rotational movement, allowing for a greater gap width at the inner edge compared to the outer edge.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional conditioning methods with uniform conditioning tools are used, then the polishing pads can be conditioned with simple equipment, but the geometry of polished wafers cannot meet increasing requirements for planarity and parallelism without edge roll-off
Solution Approach 1:
The conditioning process is segmented by dividing the conditioning tools into multiple components with different thicknesses. Instead of using a single uniform conditioning tool, the invention employs at least two conditioning tools or a conditioning tool with variable thickness, allowing different radial zones of the polishing pad to be conditioned independently. This segmentation enables precise control over the polishing gap width across the wafer surface, improving geometry without requiring complete system redesign.
Solution Approach 2:
The invention applies local quality by giving different parts of the conditioning system different properties. Specifically, different radial zones of the polishing pad are conditioned with different tool thicknesses - the inner radius zone uses conditioning tools of one thickness while the outer radius zone uses conditioning tools of another thickness. This local differentiation allows optimization of polishing parameters for each zone, achieving superior wafer geometry with reduced edge roll-off.
2Manufacturing precision
If a uniform polishing gap width is maintained across the polishing pad, then the polishing process is simple to control, but edge roll-off cannot be reduced and planarity is compromised
Solution Approach 1:
The invention introduces asymmetry into the previously symmetric uniform polishing gap configuration. By using conditioning tools with different thicknesses at different radial positions, the polishing gap width becomes asymmetric - wider at the inner radius and narrower at the outer radius (or vice versa). This asymmetric gap configuration compensates for edge roll-off effects and improves wafer planarity, while the thickness difference between conditioning tools provides a straightforward method for achieving the desired asymmetry.
3Manufacturing precision
If conditioning tools with the same thickness as spacers are used, then the device configuration is simplified, but the polishing gap width cannot be varied in the radial direction to optimize geometry
Solution Approach 1:
The invention changes the thickness parameter of the conditioning tools to achieve radial variation in polishing gap width. Specifically, the conditioning tools are designed with at least two different thickness values - a first thickness for the inner radius zone and a second thickness for the outer radius zone. This parameter change in tool thickness directly translates to the desired parameter change in gap width profile, enabling optimization of wafer geometry. The spacers maintain uniform thickness while the conditioning tools provide the variable thickness needed for radial gap control.
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 results in improved global and local geometry of semiconductor wafers, with reduced edge roll-off and enhanced planarity, by adjusting the polishing gap width to achieve a monotonic profile that optimizes the polishing process.
Implementation Method 1
generate material abrasion of at least one of the polishing pads by its relative movement
Data Source
AI summary
A method for conditioning polishing pads for the simultaneous double-side polishing of semiconductor wafer uses a double-side polishing device. The device has an annular lower polishing plate and an annular upper polishing plate, each covered with a polishing pad, as well as a rolling device for carrier disks. The method for conditioning polishing pads includes disposing at least one conditioning tool having external teeth and at least one spacer having external teeth in a working gap formed between the first and second polishing pad, where the thickness of at least one of the conditioning tools differs from the thickness of at least one of the spacers. At least one conditioning tool and one spacer are set, simultaneously, in a revolving movement about the axis of the rolling device and in rotation themselves so as to generate material abrasion of at least one of the polishing pads.