Silicate Polishing Pad Coanda Air Classifier Scratching

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Solution Overview

Problem

Chemical mechanical polishing (CMP) operations face issues such as wafer scratching due to foreign materials in polishing pads, leading to defects and variability in polishing results, which affect the quality and yield of semiconductor wafers.

Innovation Solution

A method involving the preparation of silicate-containing polishing pads with gas-filled polymeric microelements of varied densities and sizes, treated with a Coanda block air classifier to separate and clean the microelements, reducing the presence of coarse silicate particles and agglomerates, and then embedded into a polymeric matrix to form a polishing pad with improved planarization and reduced scratching.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If traditional polishing pads with glass spheres or ceramic phases are used, then polishing capability is provided, but wafer scratching and gouging occur due to foreign materials

Engineering Contradiction:

Improvepolishing capabilityVSAvoidwafer scratching

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent extracts and removes harmful foreign materials (glass spheres, ceramic phases, large silicate particles) from the polishing pad structure. By using a controlled silica sol-gel process, the invention creates a pad where silicate particles are chemically bonded within the polymer matrix, preventing them from detaching and scratching wafers, thus eliminating the harmful effect while maintaining polishing capability

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent creates a composite material structure where silicate particles are chemically integrated into the polymer matrix through silica sol-gel chemistry. This composite structure ensures that silicate particles remain firmly embedded and do not detach as foreign materials, resolving the contradiction between providing polishing capability and preventing wafer scratching

Inventive Principle:

Principle #40Composite materials

2Manufacturing precision

If careful casting techniques with controlled curing cycles are used, then macro-properties of the pad are controlled, but micro-polishing aspects and pad-to-pad variability are not addressed

Engineering Contradiction:

Improvemacro-properties controlVSAvoidpad-to-pad variability

Core Design Contradiction:

Manufacturing precisionVSReliability

Solution Approach 1:

The patent changes the fundamental parameters of pad formation by using a silica sol-gel process instead of traditional casting. This chemical process allows for precise control of particle size distribution, density, and uniformity at the micro-level, addressing both micro-polishing aspects and reducing pad-to-pad variability while maintaining macro-property control

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent performs preliminary action by pre-forming microelements with controlled silicate particle distribution before final pad assembly. This pre-structuring ensures uniform particle distribution and consistent micro-properties across all pads, reducing variability while maintaining manufacturing precision

Inventive Principle:

Principle #10Preliminary action

3Productivity

If silicate particles are present in the polishing pad, then removal rate is enhanced, but coarse particles cause chatter marks and wafer defects

Engineering Contradiction:

Improveremoval rateVSAvoidwafer surface quality

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent applies local quality by creating a non-uniform distribution of silicate particles with controlled size and concentration at different locations within the pad structure. Microelements contain silicate particles with specific size ranges (0.5-5.0 μm) that provide adequate removal rate while avoiding the chatter marks caused by larger particles, thus maintaining both productivity and surface quality

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent changes the particle size parameter to a optimized range (0.5-5.0 μm) and controls the concentration of silicate particles within microelements. This parameter optimization ensures sufficient removal rate while preventing the formation of chatter marks and wafer defects, resolving the contradiction between productivity and manufacturing precision

Inventive Principle:

Principle #35Parameter changes

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 results in a polishing pad that minimizes scratching and gouging, providing consistent polishing performance with reduced pad-to-pad variability and enhanced removal rates, improving the quality and yield of semiconductor wafers.

Implementation Method 1

passing the gas-filled microelements in the gas jet adjacent a Coanda block, the Coanda block having a curved wall for separating the polymeric microelements with Coanda effect, inertia and gas flow resistance

Methodology Applied

Scientific EffectCoanda effect: Coanda Effect

Implementation Method 2

Methodology Applied

Scientific EffectGas flow resistance: Drag

Implementation Method 3

Methodology Applied

Scientific EffectInertia: Inertia

Data Source

PatentUS8202334B2Method of forming silicate polishing pad

Publication Date: 2012.06.19 DUPONT ELECTRONIC MATERIALS HLDG INC

AI summary

The method provides a method of preparing a silicate-containing polishing pad useful for polishing at least one of semiconductor, magnetic and optical substrates. The method includes introducing a feed stream of gas-filled polymeric microelements into a gas jet. The polymeric microelements have varied densities, varied wall thickness and varied particle size. Passing the gas-filled microelements in the gas jet adjacent a Coanda block, the Coanda block having a curved wall for separates the polymeric microelements with Coanda effect, inertia and gas flow resistance. The coarse polymeric microelements from the curved wall of the Coanda block to clean the polymeric microelements. The polymeric microelements collected contain less than 0.1 weight percent total of the polymeric microelements being associated with i) silicate particles having a particle size of greater than 5 μm; ii) silicate-containing regions covering greater than 50 percent of the outer surface of the polymeric microelements; and iii) polymeric microelements agglomerated with silicate particles to an average cluster size of greater than 120 μm. Inserting the cleaned polymeric microelements into a polymeric matrix forms the polishing pad.