Polishing Head Elastic Membrane Vaulted Shape Prevents Side Wall Contact

Solution Overview

Problem

In chemical mechanical polishing (CMP) processes, the formation of negative pressure in pressure chambers can cause the side walls of elastic membranes to attract each other, preventing the retainer ring from being raised to its predetermined position, leading to obstruction of the liquid release jet and potential damage to the elastic membrane, which shortens its lifespan.

Innovation Solution

A polishing head design featuring a second elastic membrane with support portions and a coupling member that includes a recessed portion and protruding portion to prevent side wall contact, allowing the retainer ring to be raised effectively and extending the membrane's lifespan by preventing side wall attraction and facilitating smooth deformation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Ease of operation

If negative pressure is formed in the pressure chamber to raise the retainer ring, then the workpiece can be released from the polishing head, but the side walls of the elastic membrane come into contact with each other causing damage and shortening membrane lifespan

Engineering Contradiction:

Improveworkpiece releaseVSAvoidelastic membrane lifespan

Core Design Contradiction:

Ease of operationVSReliability

Solution Approach 1:

The elastic membrane is pre-formed with a vaulted shape (convex toward the pressure chamber) before negative pressure is applied. This preliminary geometric configuration ensures that when negative pressure is later applied to raise the retainer ring, the vaulted structure prevents the side walls from collapsing into contact with each other, thus avoiding damage while enabling workpiece release.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The vaulted shape of the elastic membrane acts as a protective cushioning structure against the harmful effect of negative pressure. By designing the membrane with this pre-compression-resistant geometry, the patent cushions against the vacuum-induced attraction forces that would otherwise cause side wall contact and membrane damage, extending membrane lifespan while maintaining release functionality.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

2Strength

If the retainer ring is pressed against the polishing pad during polishing, then the workpiece is prevented from slipping out, but the side walls of the elastic membrane are attracted together by vacuum when negative pressure is applied

Engineering Contradiction:

Improveworkpiece holding forceVSAvoidelastic membrane shape stability

Core Design Contradiction:

StrengthVSShape

Solution Approach 1:

The elastic membrane is pre-formed with a vaulted shape (convex toward the pressure chamber) before negative pressure is applied. This preliminary geometric configuration ensures that when negative pressure is later applied to raise the retainer ring, the vaulted structure prevents the side walls from collapsing into contact with each other, thus avoiding damage while enabling workpiece release.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The vaulted shape of the elastic membrane acts as a protective cushioning structure against the harmful effect of negative pressure. By designing the membrane with this pre-compression-resistant geometry, the patent cushions against the vacuum-induced attraction forces that would otherwise cause side wall contact and membrane damage, extending membrane lifespan while maintaining release functionality.

Inventive Principle:

Principle #11Beforehand cushioning (Prior cushioning)

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

Prevents side wall contact during negative pressure formation, ensuring the retainer ring can be raised correctly, allowing for efficient workpiece release and extending the life of the elastic membrane by preventing vacuum-induced damage.

Implementation Method 1

When a pressurized gas (for example, pressurized air) is supplied into the pressure chamber 513, the elastic membrane 512 receives a fluid pressure in the pressure chamber 513 to press the retainer ring 510 against the polishing pad 500

Methodology Applied

Scientific EffectFluid pressure: Pressure Increase

Implementation Method 2

a negative pressure is formed in the pressure chamber 513 to raise the retainer ring 510 relative to the workpiece W

Methodology Applied

Scientific EffectNegative pressure: Pressure Drop

Implementation Method 3

A first elastic membrane 38 configured to press the workpiece W against the polishing pad 2a

Methodology Applied

Scientific EffectElastic deformation: Elasticity

Data Source

PatentUS11752590B2Polishing head and polishing apparatus

Publication Date: 2023.09.12 EBARA CORP

AI summary

A polishing head capable of preventing contact between both side walls of an elastic membrane when a negative pressure is formed in a pressure chamber formed by the elastic membrane. The polishing head includes: a first elastic membrane configured to press the workpiece against the polishing pad; a retainer ring surrounding the first elastic membrane; a second elastic membrane configured to press the retainer ring against the polishing pad; a carrier to which the first elastic membrane is secured; and an attachment member arranged in a pressure chamber formed by the second elastic membrane and fixing the second elastic membrane to the carrier. The attachment member has a support portion extending toward the retainer ring along a side wall of the second elastic membrane.