Silicon Wafer Surface Stabilization for Minority Carrier Diffusion Length Measurement
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Solution Overview
Problem
The surface of silicon wafers is unstable immediately after surface treatment, making it difficult to obtain accurate measurements of minority carrier diffusion length using the surface photovoltage method, and it is challenging to determine how long the wafer must be left to stabilize for reliable data.
Innovation Solution
Irradiating the surface-treated silicon wafer with ultraviolet radiation in an oxygen-containing atmosphere to rapidly stabilize the surface, forming a thin oxide film and allowing for immediate and reliable measurement of minority carrier diffusion length.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of time
If the wafer surface is measured immediately after surface treatment, then measurement time is reduced, but measurement accuracy deteriorates due to surface instability
Solution Approach 1:
The patent applies preliminary action by irradiating the wafer surface with ultraviolet light immediately after surface treatment to stabilize the surface before measurement. This preliminary stabilization step prevents surface instability from affecting subsequent measurements, allowing accurate diffusion length measurements to be performed without waiting hours for natural stabilization.
Solution Approach 2:
The patent changes the physical state of the wafer surface by applying ultraviolet irradiation, which modifies surface properties to achieve stability. This parameter change (from unstable to stabilized surface state) enables immediate accurate measurement without the traditional waiting period, resolving the contradiction between speed and accuracy.
2Reliability
If the wafer is left standing for a prescribed period after surface treatment, then measurement reliability is improved, but productivity deteriorates due to extended measurement time
Solution Approach 1:
The patent performs preliminary surface stabilization using ultraviolet irradiation immediately after surface treatment. This preliminary action ensures the surface is stable before measurement begins, eliminating the need for extended standing periods and thereby maintaining high measurement throughput while ensuring reliable results.
Solution Approach 2:
The patent replaces the passive mechanical waiting process (letting the wafer stand for hours) with an active physical treatment (ultraviolet irradiation). This substitution actively stabilizes the surface rather than passively waiting for natural stabilization, dramatically reducing the time required while maintaining measurement reliability.
3Difficulty of detecting and measuring
If surface treatment is performed to enable SPV measurement, then measurement capability is improved, but surface stability deteriorates immediately after treatment
Solution Approach 1:
The patent introduces ultraviolet irradiation as an intermediary treatment between surface treatment and measurement. This intermediary step stabilizes the surface that was destabilized by the initial surface treatment, enabling both SPV measurement capability and surface stability to coexist without contradiction.
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 method enables rapid and highly reliable measurement of minority carrier diffusion length by stabilizing the wafer surface soon after treatment, reducing measurement time and improving data accuracy.
Implementation Method 1
irradiating the surface-treated silicon wafer with ultraviolet radiation in an oxygen-containing atmosphere to rapidly stabilize the surface, forming a thin oxide film
Implementation Method 2
This surface treatment produces band bending near the surface. In this state, minority carriers excited by irradiation through the silicon surface by light having an energy level greater than the band gap of the silicon can be collected at the surface by the electric field caused by band bending
Implementation Method 3
minority carriers excited by irradiation through the silicon surface by light having an energy level greater than the band gap of the silicon can be collected at the surface by the electric field caused by band bending, producing a surface photovoltage (SPV)
Implementation Method 4
when the silicon wafer surface is irradiated with light to dissociate pairs (such as Fe—B pairs) forming between dopants and contaminant metals
Data Source
AI summary
A method of measuring a diffusion length of a minority carrier in a silicon wafer by a surface photovoltage method including irradiating the surface-treated silicon wafer with ultraviolet radiation in an oxygen-containing atmosphere, and measuring a diffusion length of a minority carrier in a silicon wafer by a surface photovoltage method.