CMP Pad Grooves for Edge Polishing Rate Compensation
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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
A method and system for CMP that includes a polishing pad with a concentric polishing-rate adjustment groove, where a coolant or dilutant is dispensed into the groove to reduce the polishing rate in an annular zone radially inward of the groove, and the substrate is oscillated laterally to position the central and edge portions over specific zones of the polishing pad to control polishing rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional CMP polishing is used, then polishing process is simple and fast, but polishing rate is non-uniform across the substrate surface
Solution Approach 1:
The polishing pad is divided into different zones with distinct properties: a central zone with standard polishing characteristics and an annular zone with modified properties (cooler temperature, diluted slurry) to reduce polishing rate. This local differentiation allows the edge portions to polish at a reduced rate while the central portion maintains normal polishing speed, achieving uniform overall polishing.
Solution Approach 2:
The polishing pad surface is segmented into a central zone and an annular zone, each with different polishing rates. The annular zone is further defined by a polishing-rate adjustment groove that separates it from the central zone. This segmentation enables independent control of polishing parameters in different regions to compensate for edge effects.
2Productivity
If edge portions are polished at higher rate, then material removal is efficient, but substrate surface becomes uneven with hot spots
Solution Approach 1:
The annular zone is pre-configured with cooling channels and grooves to deliver cooled, diluted slurry before the substrate reaches the edge portions. This preliminary action prevents excessive heating and over-polishing at the edges by applying cooling and slurry dilution in advance, counteracting the natural tendency for edge portions to polish too quickly.
Solution Approach 2:
The polishing parameters (temperature and slurry concentration) are changed in the annular zone compared to the central zone. The annular zone operates at lower temperature and lower slurry concentration, which reduces the polishing rate. This parameter change allows the edge portions to be polished at a controlled, reduced rate while maintaining overall productivity.
3Manufacturing precision
If coolant and dilutant are applied to reduce edge polishing rate, then polishing uniformity improves, but process complexity increases
Solution Approach 1:
The cooling function and slurry delivery function are merged into a single integrated system. The cooling channels are incorporated within the polishing pad structure itself, and the same channels that deliver cooled slurry also serve as the cooling mechanism. This merging reduces the need for separate cooling systems and simplifies the overall process.
Solution Approach 2:
The polishing-rate adjustment groove acts as an intermediary structure that facilitates the delivery of cooled, diluted slurry from the cooling channels to the annular zone. This groove guides and distributes the slurry effectively, enabling controlled polishing rate reduction without requiring complex delivery mechanisms.
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 portions, achieving a more uniform polishing outcome and minimizing the occurrence of 'hot spots' on the substrate surface.
Implementation Method 1
dispensing a coolant, a dilutant, or both, into a polishing-rate adjustment groove... such that a polishing rate is reduced in an annular zone
Implementation Method 2
dispensing a coolant, a dilutant, or both, into a polishing-rate adjustment groove... such that a polishing rate is reduced
Data Source
AI summary
A method for chemical mechanical polishing includes rotating a polishing pad about an axis of rotation, positioning a substrate against the polishing pad, dispensing a polishing liquid onto the polishing pad, and oscillating the substrate laterally across the polishing pad. The polishing pad has a polishing-rate adjustment groove that is concentric with the axis of rotation, and a coolant, a dilutant, or both, is dispensed into the polishing-rate adjustment groove such that a polishing rate is reduced in an annular zone of the polishing pad that is positioned radially inward of the polishing-rate adjustment groove. The annular zone surrounds a central zone of the polishing pad in which a polishing rate is not substantially affected by the coolant, dilutant, or both.