Optical Endpoint Detection for CMP Uniformity

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Solution Overview

Problem

Chemical mechanical polishing (CMP) processes face challenges in achieving uniform material removal rates across different materials and patterns, leading to issues like dishing and erosion, which affect the electrical conductivity and planarity of semiconductor devices.

Innovation Solution

The use of a measurement signal to assess material removal status across various radial positions on the substrate, allowing for more accurate determination of the endpoint of the polishing process, thereby reducing the need for additional over-polish time and minimizing device non-uniformities.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If CMP process is used to remove excess metal and planarize surface, then material removal and planarity are improved, but dishing and erosion occur affecting electrical conductivity

Engineering Contradiction:

ImproveplanarityVSAvoiddishing and erosion

Core Design Contradiction:

Manufacturing precisionVSObject-affected harmful factors

Solution Approach 1:

The patent implements real-time optical monitoring during CMP that continuously measures the substrate surface and feeds this information back to the control system. This feedback mechanism detects the onset of dishing and erosion early, allowing the system to adjust polishing parameters dynamically to prevent these harmful effects while maintaining planarity.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically changes polishing parameters such as downforce, rotational speed, and slurry flow rate based on real-time surface condition measurements. By adjusting these parameters during the process, the system optimizes material removal rate while minimizing dishing and erosion that would otherwise degrade electrical conductivity.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If over-polishing is performed to ensure complete metal removal, then reliability is improved, but device non-uniformities and leakage currents increase

Engineering Contradiction:

Improvecomplete metal removalVSAvoidleakage currents and non-uniformities

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The optical monitoring system provides real-time feedback on metal layer thickness and removal status, enabling precise endpoint detection. This feedback control allows the system to stop polishing exactly when metal removal is complete, eliminating the need for over-polishing that would otherwise cause dielectric erosion and subsequent leakage currents.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The patent replaces traditional mechanical endpoint detection methods with optical measurement techniques. This substitution enables non-contact, real-time monitoring of the polishing process, providing precise detection of the endpoint without the mechanical interference and delay associated with conventional methods.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Productivity

If different materials are polished simultaneously, then productivity is improved, but removal rate uniformity deteriorates

Engineering Contradiction:

Improvesimultaneous material removalVSAvoidremoval rate uniformity

Core Design Contradiction:

ProductivityVSManufacturing precision

Solution Approach 1:

The system applies different polishing conditions to different regions of the substrate simultaneously. By using an array of sensors and actuators, the system can locally adjust downforce and slurry delivery based on the specific material being polished at each location, maintaining uniform removal rates across different materials while preserving overall productivity.

Inventive Principle:

Principle #3Local quality

Solution Approach 2:

The patent implements dynamic control of polishing parameters during the process. The system continuously monitors removal rates and adjusts operational parameters in real-time to compensate for differences between materials, enabling simultaneous polishing of multiple materials with uniform removal rates that would otherwise require sequential processing.

Inventive Principle:

Principle #15Dynamics

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 enhances process control and reduces the risk of leakage currents and non-uniformities by providing precise endpoint detection and adapting process parameters for improved substrate uniformity.

Implementation Method 1

a detection system configured to provide a probe signal and to receive a response to the probe signal

Methodology Applied

Scientific EffectOptical reflection: Reflection

Data Source

PatentUS8152595B2System and method for optical endpoint detection during CMP by using an across-substrate signal

Publication Date: 2012.04.10 ADVANCED MICRO DEVICES INC

AI summary

In a polishing process, the characteristics of the removal process may be monitored at different lateral positions to identify the clearance of the various device regions with a high degree of reliability. Consequently, upon forming sophisticated metallization structures, undue over-polishing may be avoided while at the same time providing reduced leakage currents due to enhanced material removal.