Multi-modal Pore Distribution Polishing Pad for Slurry Retention
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Solution Overview
Problem
Conventional chemical mechanical polishing (CMP) pads with mono-modal pore distributions face limitations in slurry retention and distribution, leading to potential slurry starvation during large wafer polishing, which can limit polish performance and require additional improvements in CMP pad technology.
Innovation Solution
Polishing pads with multi-modal distributions of pore diameters, such as bimodal, trimodal, or graded distributions, are developed to increase the number and area of pores, enhance slurry retention, and ensure consistent slurry interaction with the wafer, using thermoset polyurethane materials with closed-cell pores and porogens to optimize mechanical and chemical performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If polishing pads with mono-modal pore distributions are used, then the structure is simple and easy to manufacture, but slurry retention and distribution are insufficient leading to slurry starvation
Solution Approach 1:
The pore distribution is segmented into multiple distinct size ranges (first range and second range), creating a multi-modal distribution pattern. This segmentation allows different pore sizes to perform specialized functions: larger pores for slurry storage and smaller pores for controlled release, thereby improving slurry retention and distribution without requiring complex external systems
Solution Approach 2:
The polishing pad incorporates pores with different local qualities (different size ranges) throughout its structure. The first range pores (e.g., 10-30 μm) provide high surface area for slurry adsorption, while the second range pores (e.g., 30-100 μm) provide larger capacity for slurry storage and transport. This local differentiation of pore qualities optimizes slurry retention and prevents starvation
2Reliability
If polishing pads with multi-modal pore distributions are used, then slurry retention and distribution are improved, but the manufacturing process becomes more complex
Solution Approach 1:
The invention controls the pore size distribution by adjusting key parameters during the foam formation process, including crosslinking density, porogen particle size distribution, and curing conditions. By modifying these parameters, a multi-modal pore distribution is achieved through a relatively simple one-step process, maintaining ease of manufacture while improving slurry distribution consistency
Solution Approach 2:
The polishing pad utilizes a composite foam structure combining pores of different size ranges within a single polymeric body. This composite pore structure integrates the benefits of both small pores (high surface area) and large pores (high capacity) in one material system, achieving reliable slurry distribution without requiring assembly of multiple separate components
3Quantity of substance
If polishing pads with larger pores are used, then slurry capacity increases, but surface area for slurry interaction decreases
Solution Approach 1:
The pore population is segmented into two distinct size ranges that work synergistically. The first range (smaller pores, e.g., 10-30 μm) provides extensive surface area for slurry adsorption and interaction, while the second range (larger pores, e.g., 30-100 μm) provides additional slurry capacity and acts as reservoirs. This segmentation resolves the trade-off by distributing different functions across different pore size segments
Solution Approach 2:
The pore structure resembles a nested doll configuration where smaller pores are distributed throughout the matrix containing larger pores. The smaller pores provide high surface area within the volume occupied by larger pores, which serve as storage reservoirs. This nested arrangement maximizes both surface area and capacity within the same overall volume
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 multi-modal pore distribution pads improve slurry retention and distribution, preventing slurry starvation and enhancing polish performance, particularly for large wafers, by providing a greater volume of slurry interaction and optimizing mechanical and chemical properties, thus improving the CMP process efficiency.
Implementation Method 1
combining a polymer resin with a supercritical gas to produce a single-phase solution
Implementation Method 2
depressurizing the molded homogeneous polishing body to a pressure below the critical pressure of the gas, thereby expanding the gas in situ to a extent sufficient to form closed-cell pores
Implementation Method 3
The plurality of closed cell pores has a multi-modal distribution of diameters... improve slurry retention and distribution, preventing slurry starvation
Data Source
AI summary
Polishing pads with multi-modal distributions of pore diameters are described. Methods of fabricating polishing pads with multi-modal distributions of pore diameters are also described. In an example, a polishing pad for polishing a semiconductor substrate includes a homogeneous polishing body. The homogeneous polishing body includes a thermoset polyurethane material and a plurality of closed cell pores disposed in the thermoset polyurethane material. The plurality of closed cell pore has a multi-modal distribution of diameters.