Wafer Back-Side Polishing System for Scratch Reduction

Resolve Bottlenecks,
Find Innovative SolutionsGenerate Solutions

Solution Overview

Problem

Current wafer cleaning methods using chemical etchants are uneven and lead to excessive wafer breakage and focus spots due to scratches from abrasive polishing, while back-side polishing with abrasives also results in breakage and focus issues.

Innovation Solution

A multi-stage polishing and buffing process that includes separate stages for polishing and buffing the whole wafer back-side and bevel region using abrasive pads with soft backing and regularly shaped particles, followed by fine grit or non-abrasive buffing, and irrigation with friction-reducing agents to minimize scratching and focus spots.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If chemical etchants are used for wafer cleaning, then cleaning effectiveness is improved, but wafer breakage increases and surface uniformity deteriorates

Engineering Contradiction:

Improvecleaning effectivenessVSAvoidwafer integrity

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent replaces chemical etching processes with a mechanical polishing system that uses a polishing head with abrasive pads to clean the wafer back side. This mechanical approach eliminates the need for chemical etchants that cause wafer breakage and uneven surfaces, providing both effective cleaning and wafer integrity preservation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent controls polishing parameters including downforce applied by the polishing head, rotational speed of the wafer and polishing head, and abrasive particle characteristics (size, shape, hardness). By optimizing these parameters, the system achieves effective cleaning while minimizing wafer breakage and maintaining surface uniformity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If abrasive polishing is used on wafer back side, then cleaning capability is improved, but manufacturing precision deteriorates due to scratches and focus spots

Engineering Contradiction:

Improvecleaning capabilityVSAvoidsurface uniformity

Core Design Contradiction:

ReliabilityVSManufacturing precision

Solution Approach 1:

The patent applies different abrasive characteristics to different regions of the wafer back side. The polishing head uses abrasive pads with specifically controlled particle size, shape, and hardness to treat the back side surface uniformly, preventing scratches and focus spots while maintaining cleaning effectiveness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The polishing system uses composite abrasive pads combining soft backing material with controlled abrasive particles. This composite structure provides both the mechanical action needed for cleaning and the gentleness required to prevent surface damage, resolving the contradiction between cleaning capability and surface uniformity.

Inventive Principle:

Principle #40Composite materials

3Manufacturing precision

If bevel region polishing is performed, then particulate debris is reduced, but process complexity increases

Engineering Contradiction:

Improveparticulate debris controlVSAvoidpolishing process complexity

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The patent combines the polishing of the wafer back side and bevel region into a single integrated process using one polishing head. This merging of operations eliminates the need for separate polishing steps, reducing process complexity while effectively preventing particulate debris from the bevel region that would cause defocus issues.

Inventive Principle:

Principle #5Merging (Combining)

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

Significantly reduces wafer breakage and focus spots by ensuring even polishing and buffing, preventing particulate debris from the bevel region from causing defocus issues, and replaces chemical etchant-based cleaning processes.

Implementation Method 1

polishing a first region of the wafer that includes a central area on the back-side of the wafer, polishing a second region that includes a peripheral area on the back-side of the wafer

Methodology Applied

Scientific EffectAbrasion: Abrasion

Implementation Method 2

irrigation with friction-reducing agents to minimize scratching and focus spots

Methodology Applied

Scientific EffectFriction: Friction

Data Source

PatentUS9287127B2Wafer back-side polishing system and method for integrated circuit device manufacturing processes

Publication Date: 2016.03.15 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

A wafer polishing process includes polishing a central area on the back side of a wafer, polishing a peripheral area on the back side of the wafer, buffing the central area, and buffing the peripheral area. The process can significantly reduce scratch-related wafer breakage, can correct focus spots on wafers, and can replace cleaning processes that use chemical etchants. Polishing and buffing can include polishing and buffing the bevel region. Further improvements include polishing with abrasive pads having a soft backing, polishing or buffing with pads having relatively soft abrasive particles, polishing or buffing with abrasive pads made from abrasive particles that have been sorted and selected for regularity of shape, irrigating the surface being polished or buffed with an aqueous solution that includes a friction-reducing agent, and buffing with abrasive pads having 20 k or finer grit or non-abrasive pads.