Grayscale OPC Features in Lithographic Apparatus

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Solution Overview

Problem

Conventional lithographic apparatuses face limitations in improving Optical Proximity Correction (OPC) features, which are essential for achieving precise pattern printing, as they can only utilize binary OPC features that are sub-resolution to prevent them from appearing in the developed image, restricting the ability to print features with critical dimensions less than the exposure wavelength.

Innovation Solution

The method involves generating a mask pattern with device features at a first intensity level, a background at a second intensity level, and correction features at a third intensity level between the first and second levels, using a patterning array of individually controllable elements to spatially modulate a radiation beam and project the pattern onto a substrate, allowing for the convolution of a device pattern and a correction kernel to create intermediate intensity correction features.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If binary OPC features are made sub-resolution to prevent them from appearing in the developed pattern, then the contrast in the projected image is reduced below the resist threshold, but this restricts the ability to print features with critical dimensions less than the exposure wavelength

Engineering Contradiction:

Improvecritical dimension printing capabilityVSAvoidOPC feature design flexibility

Core Design Contradiction:

Manufacturing precisionVSAdaptability or versatility

Solution Approach 1:

The patent changes the intensity parameter of OPC features from binary (0 or 1) to continuous grayscale values. This allows OPC features to have varying intensity levels between the first intensity level (device features) and second intensity level (background), enabling precise control over their contribution to the printed pattern while maintaining design flexibility for sub-wavelength critical dimensions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces grayscale intensity levels as an intermediary state between the binary extremes. These intermediate intensity OPC features act as a mediator that can subtly influence the printed pattern without appearing as distinct features, providing a nuanced control mechanism that bridges the gap between binary OPC limitations and the need for precise sub-wavelength feature printing

Inventive Principle:

Principle #24Intermediary (Mediator)

2Adaptability or versatility

If OPC features are made with intermediate intensity levels, then design flexibility and robustness are enhanced, but the mask pattern complexity increases

Engineering Contradiction:

ImproveOPC feature design flexibilityVSAvoidmask pattern complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent employs dynamically controllable spatial light modulator elements that can be individually addressed and set to different grayscale intensity levels. This dynamic control allows the system to generate complex grayscale mask patterns on-demand without requiring physically complex masks, as the complexity is managed through programmable control rather than physical structure

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 enables the creation of larger, more robust correction features with intermediate intensity levels, enhancing flexibility in design and manufacturing, and allows for the printing of features with critical dimensions comparable to the exposure wavelength, improving the precision and quality of the printed image.

Implementation Method 1

a patterning array of individually controllable elements spatially modulates the beam according to the mask pattern

Methodology Applied

Scientific EffectDiffraction: Diffraction

Implementation Method 2

a projection system having a numerical aperture to project the patterned beam of radiation onto a target portion of the substrate

Methodology Applied

Scientific EffectOptical projection: Lens

Implementation Method 3

The OPC features are intended not to appear in the developed image themselves, but to affect the shape of the pattern features so that when developed the pattern features are closer to the desired pattern

Methodology Applied

Scientific EffectOptical proximity correction:

Data Source

PatentUS7500218B2Lithographic apparatus, method, and computer program product for generating a mask pattern and device manufacturing method using same

Publication Date: 2009.03.03 ASML NETHERLANDS BV

AI summary

Grayscale Optical Proximity Correction device features are added to a mask pattern by convoluting the device features with a two-dimensional correction kernel or two one-dimensional correction kernels to generate grayscale OPC features. The resulting pattern may be used in a projection lithography apparatus having a programmable patterning means that is adapted to generate three or more intensity levels. An iterative process of simulating an aerial image that would be produced by the pattern, comparing the simulation to the desired pattern, and adjusting the OPC features may be used to generate an optimum pattern for projection.