Cooling and Drying Subsystems for Resist Distortion Control

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Solution Overview

Problem

Semiconductor metrology processes face challenges in reducing resist distortion during electron beam measurements, particularly at the 193 nm node, where shrinkage occurs due to electron beam exposure, affecting the accuracy of critical dimension measurements and requiring methods that minimize distortion without compromising image resolution or increasing electron beam damage risks.

Innovation Solution

The implementation of a cooling subsystem and/or a drying subsystem coupled to an electron beam metrology tool to control the temperature and moisture levels near the specimen, thereby reducing resist distortion during measurements. The cooling subsystem uses Peltier elements or liquid nitrogen to alter the specimen's temperature, while the drying subsystem heats the specimen to evaporate moisture, reducing distortion without affecting the electron beam's energy settings.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If electron beam metrology is used to measure resist features, then measurement precision is improved, but resist distortion occurs due to electron beam exposure

Engineering Contradiction:

Improvecritical dimension measurement accuracyVSAvoidresist feature dimensional accuracy

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent applies preliminary action by pre-cooling the resist or pre-heating to remove moisture before electron beam measurement. This preparatory temperature control prevents the resist from undergoing thermal expansion or shrinkage during the measurement process, thereby eliminating the source of dimensional distortion while maintaining measurement precision

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent changes the temperature parameter of the resist by implementing active thermal control during electron beam measurement. By maintaining the resist at a controlled temperature (cooling or heating), the physical and chemical properties of the resist are stabilized, preventing beam-induced dimensional changes and ensuring both measurement and manufacturing precision

Inventive Principle:

Principle #35Parameter changes

2Manufacturing precision

If electron beam energy is reduced to minimize resist distortion, then resist feature distortion is reduced, but image resolution deteriorates

Engineering Contradiction:

Improveresist feature dimensional accuracyVSAvoidimage resolution

Core Design Contradiction:

Manufacturing precisionVSIllumination intensity

Solution Approach 1:

The patent changes the temperature parameter independently of the electron beam energy parameter. By controlling the resist temperature during measurement, the patent allows maintenance of optimal electron beam energy for high resolution while preventing beam-induced thermal effects that cause distortion. This decoupling of temperature control from beam energy enables simultaneous optimization of both resolution and dimensional accuracy

Inventive Principle:

Principle #35Parameter changes

3Measurement precision

If electron beam current is increased to improve signal-to-noise ratio, then measurement precision is improved, but resist distortion increases

Engineering Contradiction:

Improvesignal-to-noise ratioVSAvoidresist feature dimensional accuracy

Core Design Contradiction:

Measurement precisionVSManufacturing precision

Solution Approach 1:

The patent introduces temperature as an independent control parameter to counteract the harmful effects of high beam current. By actively controlling the resist temperature during measurement, the patent enables use of higher beam currents for improved signal-to-noise ratio while preventing the associated increased distortion through thermal stabilization

Inventive Principle:

Principle #35Parameter changes

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 effectively minimizes resist distortion, enhances measurement accuracy, and maintains image resolution and throughput, while avoiding electron beam damage to other structures on the wafer, without requiring significant modifications to the electron column.

Implementation Method 1

The cooling subsystem uses Peltier elements or liquid nitrogen to alter the specimen's temperature

Methodology Applied

Scientific EffectPeltier effect: Peltier Effect

Implementation Method 2

the drying subsystem heats the specimen to evaporate moisture

Methodology Applied

Scientific EffectEvaporation: Evaporation

Data Source

PatentUS7304302B1Systems configured to reduce distortion of a resist during a metrology process and systems and methods for reducing alteration of a specimen during analysis

Publication Date: 2007.12.04 KLA TENCOR TECHNOLOGY CORP

AI summary

Various systems configured to reduce distortion of a resist during a metrology process are provided. The systems include an electron beam metrology tool configured to measure one or more characteristics of one or more resist features formed on a specimen. The electron beam metrology tool may be configured as a scanning electron microscope. The resist may be designed for exposure at a wavelength of about 193 nm. One system includes a cooling subsystem configured to alter a temperature of the specimen during measurements by the tool such that the resist feature(s) are not substantially distorted during the measurements. Another system includes a drying subsystem that is configured to reduce moisture proximate the specimen during measurements by the electron beam metrology tool such that the resist feature(s) are not substantially distorted during the measurements. An additional system may include both the cooling subsystem and the drying subsystem.