Semiconductor Substrate Evaluation via p-n Junction Residual Image Testing
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Solution Overview
Problem
Current methods for evaluating semiconductor substrates, particularly for CCD and CMOS image sensors, face challenges in assessing residual image characteristics without producing a device, making it difficult to achieve high yields and quality, especially due to the limitations of conventional methods in measuring in-plane distribution and the influence of metal impurities.
Innovation Solution
A method involving the formation of a p-n junction on a semiconductor substrate, followed by light irradiation and measurement of carrier generation, allowing for the evaluation of residual image characteristics on a wafer level without the need for device production, using equipment for light irradiation and carrier measurement, and optionally including heat treatment to enhance defect visibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional GOI evaluation method is used, then gate oxide film reliability is assessed, but residual image characteristics and device yields are degraded
Solution Approach 1:
The patent creates a simplified model structure (p-n junction with metal impurity) that copies the essential features of the actual device problem (residual image characteristics). This model allows evaluation of substrate quality without requiring complete device fabrication, thus resolving the contradiction between reliability assessment and device yield.
2Measurement precision
If chemical analysis is performed to detect metal impurities, then trace metals are detected, but in-plane distribution information is lost
Solution Approach 1:
The patent replaces the chemical analysis method (etching and solution analysis) with an electrical measurement method. By measuring reverse leakage current across the substrate, the system obtains both the presence and spatial distribution of metal impurities, thus resolving the contradiction between detection sensitivity and information loss.
3Measurement precision
If actual device production is performed to evaluate residual image characteristics, then accurate evaluation is achieved, but evaluation complexity and time are increased
Solution Approach 1:
The patent extracts the essential evaluation function from the complete device production process. By isolating the p-n junction formation and leakage current measurement as the core evaluation mechanism, the system achieves accurate residual image characteristics evaluation without requiring full device fabrication, thus resolving the contradiction between evaluation accuracy and process complexity.
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
Enables simple and precise evaluation of residual image characteristics on a substrate level, contributing to higher quality semiconductor substrates by standardizing carrier generation measurements and highlighting defects affecting image sensor performance.
Implementation Method 1
the principle for converting light to an electric charge (photoelectric conversion) is to form a p-n junction and have a depletion layer as a structure
Implementation Method 2
a gate oxide film is formed on a surface of a silicon wafer by thermal oxidation
Data Source
AI summary
A method for evaluating electrical characteristics of a semiconductor substrate, the method including the steps of: forming a p-n junction on a surface of the semiconductor substrate; mounting the semiconductor substrate on a wafer chuck provided with an equipment for performing light irradiation on the surface of the semiconductor substrate and an equipment for measuring the quantity of the light for the irradiation; performing light irradiation on the surface of the semiconductor substrate for a predetermined time; and measuring an amount of carriers generated after the light irradiation of the p-n junction at least after turning off the light irradiation. This provides a method for evaluating a semiconductor substrate that allows the same evaluation in a wafer state as when an actual solid-state image sensor has been formed without producing a device by using process equipment when evaluating characteristics corresponding to residual image characteristics of a wafer.