Silicon Substrate Recombination Lifetime Measurement Stabilization

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Solution Overview

Problem

Existing methods for measuring recombination lifetime in silicon substrates, such as the microwave photoconductivity decay method, face challenges in accurately evaluating metal contamination and crystal defects due to variations in measurement values over time, particularly when using chemical passivation processing with alcoholic iodine solutions, which require labor-intensive corrections.

Innovation Solution

Implementing ultraviolet protection processing during chemical passivation and measurement of silicon substrates, either in a light-shielded environment or using UV-cut materials like polyethylene bags, to stabilize the recombination lifetime measurement values and reduce time-dependent changes.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If chemical passivation processing with alcoholic iodine solution is used to suppress surface recombination, then measurement speed is improved, but measurement value stability deteriorates due to time-dependent changes

Engineering Contradiction:

Improvemeasurement speedVSAvoidmeasurement value stability

Core Design Contradiction:

ProductivityVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by performing ultraviolet protection processing before the chemical passivation processing. Specifically, the silicon substrate is protected from ultraviolet light exposure prior to and during the chemical passivation with alcoholic iodine solution. This preliminary protective measure prevents the photochemical reactions that would otherwise cause time-dependent changes in measurement values, allowing rapid measurement without correction while maintaining stability.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary element - ultraviolet protection (either UV-blocking material or light-shielded environment) - that mediates between the chemical passivation process and the silicon substrate. This intermediary prevents ultraviolet light from reaching the substrate during passivation, thereby preventing the harmful photochemical reactions while allowing the beneficial chemical passivation to proceed, resolving the contradiction between speed and stability.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Measurement precision

If correction formula method is used to compensate for time-dependent changes, then measurement precision is improved, but measurement time and labor increase

Engineering Contradiction:

Improvemeasurement accuracyVSAvoidmeasurement time

Core Design Contradiction:

Measurement precisionVSLoss of time

Solution Approach 1:

The patent extracts and removes the cause of measurement value changes - ultraviolet light exposure - from the measurement process. By eliminating the ultraviolet light factor that necessitates correction, the patent removes the need for time-consuming correction formula applications and repeated measurements, thereby improving productivity while maintaining precision through direct stabilization of the measurement values.

Inventive Principle:

Principle #2Taking out (Extraction)

3Reliability

If heat oxidation treatment is used to suppress surface recombination, then surface recombination suppression is improved, but metal contamination and crystal defects may be introduced

Engineering Contradiction:

Improvesurface recombination suppressionVSAvoidmetal contamination and crystal defects

Core Design Contradiction:

ReliabilityVSObject-affected harmful factors

Solution Approach 1:

The patent employs chemical passivation with alcoholic iodine solution as a disposable, non-thermal alternative to heat oxidation. This chemical method provides effective surface recombination suppression without requiring high-temperature processing, thereby avoiding the introduction of metal contamination and crystal defects associated with thermal processes, while maintaining the necessary surface passivation quality for accurate measurements.

Inventive Principle:

Principle #27Cheap short-living objects (Disposable)

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 allows for high-accuracy, rapid evaluation of metal contamination and crystal defects in silicon substrates, ensuring consistent measurement results and reducing the impact of ultraviolet light on chemical reactions.

Implementation Method 1

performing ultraviolet protection processing of protecting at least the silicon substrate from ultraviolet rays

Methodology Applied

Scientific EffectUltraviolet absorption: Absorption (EM radiation)

Implementation Method 2

the measurement of a recombination lifetime by a microwave photoconductivity decay method (μ-PCD method) has been widely used

Methodology Applied

Scientific EffectPhotoconductivity: Photoconductivity

Implementation Method 3

This change is detected as a change with time in reflected microwave power

Methodology Applied

Scientific EffectMicrowave radiation: Microwave Radiation

Data Source

PatentUS9530702B2Method for measuring recombination lifetime of silicon substrate

Publication Date: 2016.12.27 SHIN ETSU HANDOTAI CO LTD

AI summary

Provided is a method of measuring a recombination lifetime of a silicon substrate, which is capable of evaluating metal contamination and crystal defects in a silicon substrate manufacturing process and a device manufacturing process with high accuracy. The method includes: measuring a recombination lifetime of a silicon substrate after subjecting a surface of the silicon substrate to chemical passivation processing; and performing ultraviolet protection processing of protecting at least the silicon substrate from ultraviolet rays during a period from the chemical passivation processing to a time when the measurement of the recombination lifetime is completed.