CMP Slurry Chelation for Semiconductor Erosion Control

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Solution Overview

Problem

In semiconductor manufacturing, CMP techniques face challenges with excessive polishing leading to dishing or erosion, which can cause short-circuits between wirings, and existing methods struggle to effectively suppress these issues while maintaining high polishing rates.

Innovation Solution

A method involving a basic CMP slurry with metal ions, followed by the addition of an organic acid that chelates these ions, is used to polish semiconductor wafers, adjusting the polishing rate to match that of the insulating layer and reducing erosion, and a washing process with organic acid to remove residual metal ions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If excessive polishing is performed to avoid metallic material remnants, then completeness of material removal is improved, but dishing or erosion occurs

Engineering Contradiction:

Improvecompleteness of material removalVSAvoiddishing or erosion

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent changes the chemical composition parameters of the CMP slurry by adding organic acids (oxalic acid, citric acid, or malonic acid) to the basic slurry containing metal ions. This parameter change modifies the slurry's chemical properties to reduce its aggressiveness, allowing complete material removal without causing dishing or erosion. The organic acid concentration is specifically controlled at 0.01-5 wt% to achieve the optimal balance between removal completeness and surface integrity.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent creates a composite CMP slurry by combining basic slurry containing metal ions with organic acids. This composite formulation integrates the metal ions' ability to remove metallic materials with the organic acids' ability to suppress dishing and erosion, achieving both complete material removal and surface protection simultaneously.

Inventive Principle:

Principle #40Composite materials

2Productivity

If CMP slurry containing metal ions is used to remove metallic material layer, then polishing rate is improved, but metal ion contamination on wafer surface occurs

Engineering Contradiction:

Improvepolishing rateVSAvoidmetal ion contamination

Core Design Contradiction:

ProductivityVSObject-generated harmful factors

Solution Approach 1:

The patent converts the harmful effect of metal ion contamination into a beneficial process by adding organic acids that chelate with metal ions. The chelation reaction binds metal ions in the slurry, preventing them from contaminating the wafer surface while maintaining the slurry's polishing capability. This transforms the potential harm of metal ion release into a controlled chemical interaction that protects the wafer.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The organic acid acts as an intermediary substance between the metal ions and the wafer surface. It binds to metal ions through chelation, serving as a mediator that prevents direct contact between metal ions and the wafer, thereby eliminating contamination while preserving the polishing function.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If basic CMP slurry is used for polishing, then polishing efficiency is maintained, but erosion of insulating film increases

Engineering Contradiction:

Improvepolishing efficiencyVSAvoiderosion control

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The patent modifies the chemical parameters of the CMP slurry by introducing organic acids at controlled concentrations (0.01-5 wt%). This parameter adjustment reduces the slurry's erosive effect on the insulating film while preserving its polishing efficiency on metallic layers, achieving selective polishing with reduced damage.

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

This approach significantly reduces erosion and dishing, maintains high polishing efficiency, and prevents metal ion contamination on the wafer surface, enhancing the reliability of semiconductor devices.

Implementation Method 1

adding an organic acid which chelates the metal ions to the basic CMP slurry

Methodology Applied

Scientific EffectChelation:

Implementation Method 2

the surface of the wafer is slid on a polishing pad while the wafer surface is pressed against the pad, thereby chemically and mechanically polishing the wafer surface

Methodology Applied

Scientific EffectChemical mechanical polishing:

Data Source

PatentUS7413989B2Method of manufacturing semiconductor device

Publication Date: 2008.08.19 KIOXIA CORP

AI summary

A semiconductor wafer including an underlying layer including an insulating film having at least one recess therein and a metallic material layer formed over a top surface of the underlying layer and filling the recess, on a semiconductor substrate, is subjected to a polishing treatment while supplying a basic CMP slurry containing metal ions on the semiconductor wafer to at least partially remove the metallic material layer. Then, an organic acid which chelates the metal ions is added to the basic CMP slurry, and polishing is conducted, using the organic acid-added CMP slurry, until a surface of the insulating film is exposed.