CMP Pad Edge Hot Spot Compensation via Discharge Grooves
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Solution Overview
Problem
Chemical mechanical polishing (CMP) processes often result in non-uniform polishing rates across substrates, with edge portions polishing at a higher rate than central portions, leading to uneven substrate surfaces.
Innovation Solution
The method involves using a polishing pad with an annular outer region and a circular central region, where the annular outer region has polishing liquid discharge grooves to preferentially discharge polishing liquid, and the substrate is oscillated laterally to position the central and edge portions over different regions of the pad, thereby controlling the polishing rate.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If the substrate is polished using a conventional polishing pad without region-specific modifications, then the polishing process is simple and fast, but the polishing rate is non-uniform with edge portions polishing faster than central portions
Solution Approach 1:
The polishing pad is divided into distinct regions with different properties: a central region and an annular outer region. The annular outer region includes polishing liquid discharge grooves that are absent in the central region, creating localized differences in polishing liquid distribution and discharge characteristics to compensate for edge polishing effects
Solution Approach 2:
The polishing pad surface is segmented into functional zones - a central polishing region and an annular outer region with discharge grooves. This segmentation allows different regions to perform different functions: the central region provides standard polishing while the annular region with grooves manages polishing liquid discharge to reduce edge polishing rate
2Manufacturing precision
If the polishing liquid discharge grooves are added to the annular outer region, then the polishing rate uniformity is improved, but the device complexity and manufacturing difficulty increase
Solution Approach 1:
The discharge grooves are localized only to the annular outer region rather than being distributed across the entire pad surface. This localized modification allows the grooves to specifically address edge polishing issues while maintaining simple polishing pad fabrication in the central region
Solution Approach 2:
The polishing liquid discharge grooves are pre-formed in the annular outer region during polishing pad manufacturing. This preliminary structuring of the discharge path ensures that polishing liquid is efficiently discharged from the edge regions before the polishing process begins, preventing accumulation and ensuring uniform polishing rates
3Manufacturing precision
If the substrate is oscillated laterally to position different regions over the polishing pad, then the polishing rate is controlled and uniformity is improved, but the process complexity and time increase
Solution Approach 1:
The substrate is oscillated laterally in a periodic manner, alternating between positions where the central portion and edge portion are polished, and positions where only the central portion is polished. This periodic positioning control allows the edge portions to be polished at a reduced rate when positioned over the annular region with discharge grooves, achieving uniformity without requiring complex real-time adjustment
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 effectively reduces the polishing rate of the edge portion, achieving a more uniform polishing outcome and minimizing the occurrence of 'hot spots' on the substrate surface.
Implementation Method 1
The exposed surface of the substrate is typically placed against a rotating polishing pad... An abrasive polishing slurry is typically supplied to the surface of the polishing pad
Implementation Method 2
the annular outer region having a plurality of polishing liquid discharge grooves that start at an outer perimeter of the circular central region and extend radially outward to an edge of the polishing pad so as to preferentially discharge the polishing liquid from the annular outer region
Implementation Method 3
oscillating the substrate laterally across the polishing pad such that for a first duration a central portion of the substrate and an edge portion of the substrate are positioned over the central region of the polishing pad
Data Source
AI summary
A polishing pad has a polishing layer having a polishing surface that has a circular central region and an annular outer region surrounding the central region. The polishing surface can include slurry distribution grooves formed with uniformity spacing across the central region and the annular outer region, and slurry discharge grooves that start at an outer perimeter of the circular central region and extend radially outward to an edge of the polishing pad so as to preferentially discharge the polishing liquid from the annular outer region. The central region can be formed of a first polishing material and the annular outer region can be formed of a second polishing material that is softer than the first polishing material.