Interstitial Oxygen Mapping in Semiconductor Ingots
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Solution Overview
Problem
Current methods for characterizing the oxygen content in semiconductor ingots, such as those obtained by the Czochralski method, are either expensive, time-consuming, or degrade the material's electronic properties, as they require cutting the ingot into multiple wafers and involve high-temperature annealing processes.
Innovation Solution
A method involving cutting a longitudinal section and a wafer from the ingot, performing radial and longitudinal measurements of interstitial oxygen concentration, and combining these using mathematical functions to map the oxygen distribution throughout the ingot without the need for complete wafer or slice cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the ingot is cut into numerous small plates and heat treatment is performed on all plates to map oxygen concentration, then the oxygen distribution can be determined, but the process becomes lengthy and expensive
Solution Approach 1:
The ingot characterization is divided into two independent measurement series: radial measurements on a single plate and longitudinal measurements on a single section. This segmentation allows parallel processing and eliminates the need to process numerous plates sequentially, significantly reducing characterization time while maintaining complete oxygen distribution mapping capability
Solution Approach 2:
The radial oxygen concentration profile measured on a single plate is copied and integrated with longitudinal measurements from a single section to reconstruct the complete three-dimensional oxygen distribution throughout the entire ingot. This copying approach eliminates redundant measurements on multiple plates while preserving the ability to determine oxygen concentration at any position in the ingot
2Measurement precision
If high-temperature annealing (600-900°C) is performed to measure oxygen content through thermal donors, then oxygen concentration can be determined, but significant oxygen precipitation occurs leading to decreased electronic properties
Solution Approach 1:
The measurement process uses low-temperature annealing (350-500°C) instead of high-temperature annealing (600-900°C). This parameter change in annealing temperature allows thermal donor formation for oxygen measurement while preventing significant oxygen precipitation that would degrade electronic properties such as carrier lifetime
Solution Approach 2:
The patent replaces the high-temperature thermal annealing mechanism with a low-temperature thermal donor formation mechanism. By substituting the measurement mechanism to operate at lower temperatures, the harmful side effect of oxygen precipitation and subsequent degradation of electronic properties is avoided while maintaining the ability to determine oxygen concentration
3Loss of information
If the entire ingot is cut into multiple wafers to perform oxygen characterization, then complete oxygen distribution data is obtained, but the process complexity and cost increase significantly
Solution Approach 1:
The characterization process is segmented into two independent measurements on single samples (one plate for radial profile, one section for longitudinal profile) rather than requiring processing of multiple wafers. This segmentation maintains complete oxygen distribution information while dramatically simplifying the experimental procedure and reducing process complexity
Solution Approach 2:
The patent transitions from a two-dimensional wafer-based measurement approach to a three-dimensional reconstruction approach using radial and longitudinal measurements. By measuring in different dimensional orientations (radial on plate, longitudinal on section) and mathematically integrating the data, complete oxygen distribution information is obtained with fewer physical samples and reduced 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
This approach allows for precise, rapid, and cost-effective characterization of interstitial oxygen distribution within the ingot, avoiding material degradation and reducing the complexity of existing techniques.
Implementation Method 1
The absorption of the infrared beam by the ingot allows for the determination of an average oxygen concentration within the ingot
Implementation Method 2
a silicon wafer is subjected to heat treatment to form thermal donors
Data Source
Figure 1~2B
Figure 3A~3B
Figure 3C
AI summary
The invention relates to a method for characterising the concentration of interstitial oxygen in an ingot made of a semiconducting material, which includes the following steps: cutting into the ingot a segment (11) along a longitudinal plane of the ingot and at least one wafer along a transverse plane of the ingot; taking a first series of measurements, referred to as radial measurements, of the interstitial oxygen concentration in said wafer, the radial measurements being distributed on a radius of said wafer; taking (F3) a second series of measurements, referred to as longitudinal measurements ([Oi](y)), of the interstitial oxygen concentration in the segment (11), the longitudinal measurements being distributed along the segment (11); and combining the radial measurements and the longitudinal measurements of the oxygen concentration such as to obtain the interstitial oxygen concentration in each zone of the ingot.