Lithographic Scanner Control Parameter Drift Compensation

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Solution Overview

Problem

Current lithographic apparatuses face challenges in accurately controlling scanner stability and intra-field effects due to limitations in parameterization, leading to suboptimal noise suppression and inability to cover all relevant effects, resulting in production stoppages and reduced process window.

Innovation Solution

A system with a control module that periodically retrieves baseline control parameters from reference substrates to determine parameter drift, allowing for corrective action, and a different parameterization interface between the control module and the lithographic apparatus, enabling more flexible and accurate control of scanning/stepping functions.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If standard parameterization is used for scanner control, then the system can operate with established control methods, but the system cannot accurately cover all intra-field effects and achieve optimal noise suppression

Engineering Contradiction:

Improvescanner stability control precisionVSAvoidparameterization flexibility

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The control parameterization is segmented into two distinct sets: a first parameterization for the control module interface and a second parameterization for the lithographic apparatus interface. This segmentation allows each parameterization to be optimized independently - the first can capture all intra-field effects with appropriate complexity while the second maintains compatibility with existing scanner control systems, thereby resolving the contradiction between precision and adaptability

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

A conversion module acts as an intermediary between the two parameterizations. It receives control parameters from the control module in the first parameterization format, converts them to the second parameterization format, and transmits them to the lithographic apparatus. This intermediary enables the system to utilize the enhanced precision of the first parameterization while maintaining compatibility with the existing apparatus through the second parameterization

Inventive Principle:

Principle #24Intermediary (Mediator)

2Reliability

If more parameters are used to describe scanner effects, then more intra-field effects can be covered, but the system complexity increases and existing interfaces cannot accommodate the new parameterization

Engineering Contradiction:

Improvescanner stabilityVSAvoidparameterization complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The parameterization complexity is segmented by creating two distinct parameterization systems. The first parameterization can incorporate as many parameters as needed to fully describe scanner effects and achieve high reliability, while the second parameterization maintains the simplicity required by existing interfaces. The segmentation isolates complexity to where it is needed without propagating it throughout the entire system

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The conversion module creates a mapping between the two parameterizations, effectively copying and transforming parameters from the first parameterization format to the second. This copying mechanism allows the system to utilize the comprehensive parameter set of the first parameterization for reliable control while presenting a simplified interface to the existing apparatus through the second parameterization

Inventive Principle:

Principle #26Copying

3Measurement precision

If baseline measurements are periodically retrieved from reference substrates, then parameter drift can be detected and corrected, but additional measurement time and processing are required

Engineering Contradiction:

Improveparameter drift detection accuracyVSAvoidmeasurement and correction cycle time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

Reference substrates are prepared in advance with embedded metrology targets and baseline measurements are taken during initial system setup or maintenance periods. This preliminary action creates a reference database that can be used for ongoing drift detection without requiring time-consuming measurements during production cycles, thereby improving measurement precision without significant time penalty

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The system implements a feedback mechanism where baseline measurements from reference substrates are periodically compared against current production measurements. When drift is detected, correction parameters are automatically calculated and applied to the scanner control. This closed-loop feedback enables precise drift detection while minimizing time loss through automated correction rather than manual intervention

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS8947630B2Lithographic apparatus and device manufacturing method

Publication Date: 2015.02.03 ASML NETHERLANDS BV

AI summary

A method controls scanning function of a lithographic apparatus. A monitor wafer is exposed to determine baseline control parameters pertaining to the scanning function. The baseline control parameters are retrieved from the monitor wafer. Parameter drift is determined from the baseline control parameters. Compensation is performed based on the determination. A different parameterization is used for control of the scanning control module than for communication between the scanning control module and the lithographic apparatus.