Substrate Edge Tapering for Uniform Chemical Mechanical Polishing
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Solution Overview
Problem
Chemical mechanical polishing processes face variations in material removal rates due to slurry composition, polishing pad conditions, speed, initial substrate layer thickness, and load, leading to non-uniform polishing and potential over- or under-polishing of substrate edges, resulting in electrical failures.
Innovation Solution
A method and system that modify the substrate thickness profile by removing material from the edge region before polishing, using a modification station with a support and modification device to create a tapered edge, ensuring uniform polishing and reducing stress concentrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP is used with uniform substrate thickness, then the polishing process is simple, but material removal rate varies across the substrate leading to non-uniform polishing
Solution Approach 1:
The substrate thickness profile is modified in advance before the CMP process by removing material from the edge region to create a tapered profile. This preliminary action compensates for the expected non-uniform material removal during polishing, ensuring that the center and edge regions reach the target thickness simultaneously, thereby achieving uniform polishing results.
Solution Approach 2:
The substrate is given different thickness characteristics in different regions: the center region maintains the original thickness while the edge region is thinned to create a tapered profile. This local differentiation in thickness quality compensates for the varying material removal rates during polishing, with the thinner edge region requiring less removal to achieve uniform final thickness.
2Reliability
If edge regions are polished with same parameters as center, then the process is simple, but edge regions are over-polished or under-polished causing electrical failures
Solution Approach 1:
The edge region thickness is reduced in advance before polishing to account for the higher material removal rate expected at the edges during CMP. This preliminary thickness adjustment ensures that when standard polishing parameters are applied, both center and edge regions achieve the target thickness simultaneously, preventing over-polishing of edges and under-polishing of centers, thus maintaining electrical reliability.
Solution Approach 2:
The substrate thickness parameter is modified in the edge region to create a tapered profile that transitions from the original uniform thickness at the center to a reduced thickness at the edges. This parameter change compensates for the spatial variation in material removal rate during polishing, ensuring uniform final thickness and preventing electrical failures caused by non-uniform polishing.
3Productivity
If material removal rate is increased to improve productivity, then polishing is faster, but variations in removal rate across substrate increase leading to non-uniform results
Solution Approach 1:
The substrate edge thickness is reduced in advance to create a tapered profile that anticipates the non-uniform material removal that will occur during high-speed polishing. This preliminary modification allows the use of higher polishing speeds for improved productivity while maintaining thickness uniformity, as the thinner edge region compensates for the increased removal rate at the edges.
Solution Approach 2:
Different thickness characteristics are applied to different substrate regions: the center maintains original thickness while edges are thinned. This local quality differentiation enables higher overall polishing speeds because the tapered profile ensures that the thinner edge regions (which experience higher removal rates) will reach the target thickness at the same time as the thicker center region, maintaining uniformity even at increased productivity levels.
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 achieves uniform metal line topography and electrical properties, improving yield by maintaining consistent material removal rates across the substrate, preventing over- or under-polishing and potential electrical failures.
Implementation Method 1
The modification device is configured to modify the edge of the substrate at the modification station by removing material from a region of the first surface
Implementation Method 2
Chemical mechanical polishing (CMP) is one accepted method of planarization
Data Source
AI summary
Before a first surface of a substrate is polished using a chemical mechanical process, the substrate is transferred to a modification station. The substrate comprises a side wall connected with the first surface at an edge and a second surface opposite to the first surface and also connected to the side wall. The first surface is substantially flat. The side wall is substantially perpendicular to the first surface. The edge of the substrate is modified at the modification station by removing material from a region of the first surface. The side wall of the substrate is a boundary of the region. The modified edge comprises a modified first surface that tapers within the region towards the second surface. The side wall remains substantially perpendicular to the first surface.