CMP Pad Profile Control via Metrology Feedback

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Solution Overview

Problem

The CMP process faces issues with uneven wear of the polishing pad, leading to defective wafer processing due to an uneven polishing surface, which existing systems fail to effectively monitor and correct in real-time.

Innovation Solution

A closed-loop system that includes a metrology system for monitoring the thickness of the polishing pad and a conditioning disk, using sensors to create a thickness map and adjust the material removal rate to maintain uniformity, with options for sensor configuration and corrective actions based on detected variations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If the polishing pad is used continuously for wafer processing, then productivity is improved, but the polishing surface becomes uneven leading to manufacturing precision degradation

Engineering Contradiction:

Improvecontinuous wafer processingVSAvoidpolishing surface uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The system performs preliminary conditioning actions by identifying thick areas on the polishing pad before they cause significant polishing defects. The metrology system continuously monitors pad thickness and triggers conditioning disk intervention proactively, preventing uneven wear patterns from developing rather than correcting them after damage occurs.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements a closed-loop feedback mechanism where the metrology system continuously measures polishing pad thickness during wafer processing, feeds this information to the control system, which then adjusts conditioning disk operation in real-time. This feedback loop maintains polishing surface uniformity while enabling continuous productivity without manual intervention.

Inventive Principle:

Principle #23Feedback

2Manufacturing precision

If the conditioning disk is used to maintain polishing pad uniformity, then manufacturing precision is improved, but the polishing pad wears faster leading to loss of substance

Engineering Contradiction:

Improvepolishing surface uniformityVSAvoidpolishing pad material removal

Core Design Contradiction:

Manufacturing precisionVSLoss of substance

Solution Approach 1:

The system applies local quality conditioning by directing the conditioning disk selectively to specific radial positions on the polishing pad where thickness variations are detected. Rather than uniformly conditioning the entire pad surface, the system concentrates conditioning actions only on thick areas that require material removal, preserving material in areas that are already at the correct thickness.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The system uses partial action by applying conditioning only to the extent necessary - specifically to thick areas of the polishing pad. The conditioning disk operates intermittently and locally rather than continuously and uniformly, removing material only where needed to achieve uniformity without excessive material loss from areas that don't require conditioning.

Inventive Principle:

Principle #16Partial or excessive action

3Manufacturing precision

If a metrology system is implemented to monitor polishing pad thickness, then manufacturing precision is improved, but device complexity increases

Engineering Contradiction:

Improvepolishing pad thickness measurementVSAvoidsystem configuration

Core Design Contradiction:

Manufacturing precisionVSDevice complexity

Solution Approach 1:

The metrology system is designed with multi-functionality, serving both as a measurement device for thickness monitoring and as a trigger mechanism for conditioning control. The same sensor array and data processing infrastructure supports both wafer thickness measurement and polishing pad condition assessment, reducing overall system complexity despite the advanced measurement capabilities.

Inventive Principle:

Principle #6Universality (Multi-functionality)

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 system ensures a uniform polishing pad surface, extending its lifespan and preventing defective wafer processing by dynamically adjusting the material removal rate to correct uneven wear patterns, thereby optimizing wafer processing quality.

Implementation Method 1

The thickness of the polishing pad is monitored by the metrology system during the CMP processing. The metrology system can detect the thickness of all areas of the polishing surface by placing a distance sensor at a fixed distance over the polishing pad and taking distance measurements.

Methodology Applied

Scientific EffectDistance measurement:

Data Source

PatentUS8221193B2Closed loop control of pad profile based on metrology feedback

Publication Date: 2012.07.17 APPLIED MATERIALS INC

AI summary

A chemical mechanical polishing apparatus includes a metrology system that detects the thickness of the polishing pad as semiconductor wafers are processed and the thickness of the polishing pad is reduced. The chemical mechanical polishing apparatus includes a controller that adjusts the rate of material removal of a conditioning disk when areas of the polishing surface are detected that are higher or lower than the adjacent areas of the polishing pad.