Brightness Correction Function for Detector Non-Linearity Compensation

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Solution Overview

Problem

Existing methods for determining object characteristics, such as position and line width on semiconductor substrates, are hindered by non-linearities in detectors and light sensors, leading to significant residual errors despite efforts to reduce fluctuations in exposure time and brightness.

Innovation Solution

A method that applies a correction function to brightness measuring results to ensure they are proportional to the impinging light, compensating for non-linearities and reducing residual errors, thereby enabling reproducible measurements.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If a detector or light sensor is used to measure brightness, then brightness measurement is achieved, but non-linearities in the detector cause residual errors in object characteristic determination

Engineering Contradiction:

Improvebrightness measurement accuracyVSAvoidreproducibility of object characteristics

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent applies a correction function that transforms the non-linear brightness measuring results into corrected values that are proportional to the impinging light. This parameter transformation compensates for detector non-linearities and enables reproducible measurements of object characteristics such as position and line width, directly resolving the contradiction between achieving brightness measurement and maintaining measurement reliability

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The correction function acts as a feedback mechanism that compensates for the non-linear response of the detector. By applying the correction function to the brightness measuring results, the system feedback-adjusts the measurements to eliminate the influence of detector non-linearities, thereby improving the reproducibility of object characteristic determinations

Inventive Principle:

Principle #23Feedback

2Adaptability or versatility

If exposure time or light source brightness is varied, then measurement flexibility is improved, but residual errors increase due to detector non-linearities

Engineering Contradiction:

Improvemeasurement flexibilityVSAvoidobject characteristic accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The correction function transforms brightness measuring results obtained under varying exposure times or light source conditions into corrected values that are proportional to the actual light intensity. This allows flexible variation of exposure parameters while maintaining measurement precision, as the correction function compensates for the non-linear detector response to different brightness levels

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 results in smaller residual errors and more accurate, reproducible determination of object characteristics, making measurements independent of detector non-linearities and light source variations.

Implementation Method 1

imaging an object onto a detector by means of an imaging optics

Methodology Applied

Scientific EffectOptical imaging: Lens

Implementation Method 2

detecting the object thereon

Methodology Applied

Scientific EffectPhotoelectric effect: Photoelectric Effect

Data Source

PatentUS7939789B2Method for reproducibly determining geometrical and/or optical object characteristics

Publication Date: 2011.05.10 VISTEC SEMICON SYST

AI summary

A method for reproducibly determining object characteristics is disclosed. Herein an object is imaged onto a detector by means of an imaging optics and detected thereon. A correction function k is applied to a brightness measuring result N originally detected by a detector in such a way, that a corrected brightness measuring result N′ is proportional to a brightness I impinging on the detector.