CMP System Closed-Loop Control for Polishing Pad Roughness

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Solution Overview

Problem

The existing chemical mechanical polishing (CMP) processes face challenges in maintaining uniform removal rates across semiconductor wafers due to variations in polishing pad surface roughness, leading to thickness variations within and between wafers, and require extensive resource-intensive tuning to optimize pad conditioning.

Innovation Solution

A CMP system equipped with a sensor to non-contactly measure the surface roughness of the polishing pad, a controller to adjust polishing conditions in real-time, and a conditioner to recondition the pad, ensuring uniform surface roughness and consistent removal rates through closed-loop control.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If pad conditioning is performed to maintain polishing pad characteristics, then polishing rate and quality are improved, but extensive resource-intensive tuning is required to optimize conditioning

Engineering Contradiction:

Improvepolishing quality uniformityVSAvoidconditioning recipe development time

Core Design Contradiction:

Manufacturing precisionVSLoss of time

Solution Approach 1:

The system employs real-time surface roughness sensing during polishing operations, creating a closed-loop feedback mechanism that automatically adjusts conditioning parameters. The sensor continuously monitors pad surface roughness and provides data to the controller, which modifies conditioning intensity and duration dynamically, eliminating the need for extensive manual recipe development while maintaining optimal polishing quality.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The polishing system performs self-optimization through automated feedback control, where the controller autonomously adjusts conditioning parameters based on real-time sensor data without requiring external intervention or extensive manual tuning. The system serves itself by automatically adapting to pad wear and surface condition changes, reducing resource-intensive manual optimization efforts.

Inventive Principle:

Principle #25Self-service

2Reliability

If real-time monitoring of polishing pad surface roughness is implemented, then uniformity and consistency are improved, but device complexity increases

Engineering Contradiction:

Improvewafer-to-wafer uniformityVSAvoidsystem complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

A non-contact optical sensor serves as an intermediary between the polishing pad surface and the control system. This sensor indirectly measures surface roughness without physically contacting the pad, avoiding complex mechanical measurement systems while providing reliable real-time data for closed-loop control, thereby maintaining wafer-to-wafer uniformity without excessive system complexity.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The system replaces complex mechanical surface measurement mechanisms with non-contact optical sensing. Instead of using tactile probes or mechanical stylus systems that would increase device complexity, the patent employs optical methods to detect surface roughness, simplifying the overall system architecture while maintaining high measurement accuracy for reliability.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Device complexity

If traditional polishing processes are used without real-time monitoring, then device complexity is reduced, but thickness variations within and between wafers increase

Engineering Contradiction:

Improvesystem simplicityVSAvoidthickness uniformity

Core Design Contradiction:

Device complexityVSManufacturing precision

Solution Approach 1:

The system implements feedback control where real-time surface roughness measurements from the sensor are continuously fed back to the controller, which automatically adjusts conditioning parameters. This closed-loop mechanism maintains thickness uniformity across wafers by dynamically compensating for pad wear and surface condition changes, achieving high manufacturing precision without requiring complex manual intervention systems.

Inventive Principle:

Principle #23Feedback

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 solution enhances wafer-to-wafer and lot-to-lot uniformity, reduces rework rates, extends pad life, and decreases the time and resources needed for conditioning recipe development, thereby improving yield and reducing costs.

Implementation Method 1

a sensor to non-contactly measure the surface roughness of the polishing pad

Methodology Applied

Scientific EffectOptical detection: Reflection

Data Source

PatentUS20230390882A1System, control method and apparatus for chemical mechanical polishing

Publication Date: 2023.12.07 TAIWAN SEMICONDUCTOR MANUFACTURING CO LTD

AI summary

Disclosed are a chemical mechanical polishing apparatus, a control method for the chemical mechanical polishing apparatus and a chemical mechanical polishing system. In one embodiment, the chemical mechanical polishing apparatus includes a polishing pad, a sensor, a polishing head and a conditioner. The sensor is configured to obtain surface roughness of the polishing pad. The polishing head is located above the polishing pad and configured to polish a wafer which is push against the polishing pad. The conditioner is located on the polishing pad and configured to recondition the polishing pad, wherein the conditioner is operated according to at least one polishing condition, and the polishing condition is tuned according to the surface roughness of the polishing pad.