Liquid-Metal Schottky Wafer Evaluation for Large-Diameter Defect Mapping
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Solution Overview
Problem
Existing methods for evaluating crystal defects in semiconductor wafers are inadequate for large-diameter wafers and unsuitable for mass production, as they require cutting samples and stacking electrodes, making it difficult to assess point defects across the entire surface effectively.
Innovation Solution
A semiconductor wafer evaluation apparatus using a liquefied metal (mercury) Schottky electrode that contacts the wafer, applies voltage intermittently to compensate for parasitic inductance and capacitance, and evaluates point defects based on electrostatic capacity changes, allowing for non-destructive evaluation of the entire wafer surface without cutting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a Schottky electrode is formed by cutting a sample and stacking a metal electrode, then point defect evaluation can be performed, but the evaluation process becomes complex and unsuitable for mass production
Solution Approach 1:
The invention extracts the essential function of the Schottky electrode (forming a junction with the semiconductor wafer) without requiring the complex preparation process of cutting and stacking. By using a liquid metal that can be directly applied to the wafer surface, the invention separates the electrode formation step from the sample preparation step, thereby simplifying the overall evaluation process while maintaining measurement precision
Solution Approach 2:
The invention replaces the mechanical process of cutting and stacking solid metal electrodes with a liquid metal application process. The liquid metal can be dispensed and formed into electrodes through fluid handling rather than mechanical machining, significantly reducing process complexity and enabling automated mass production evaluation
2Measurement precision
If the existing evaluation method is used, then point defects can be evaluated, but it is difficult to apply to large-diameter semiconductor wafers
Solution Approach 1:
The liquid metal Schottky electrode system is designed to be universally applicable to semiconductor wafers of various sizes. The liquid metal can be dispensed in controlled amounts and allowed to spread or be formed into appropriate electrode patterns suitable for different wafer diameters, making the evaluation method scalable from small to large wafers without requiring different equipment or procedures
3Measurement precision
If voltage is continuously applied during evaluation, then measurement can be performed, but parasitic inductance and capacity affect measurement accuracy
Solution Approach 1:
The invention applies voltage periodically or intermittently rather than continuously during the measurement process. This periodic application of voltage allows the measurement system to capture the electrostatic capacity characteristics at specific phases of the cycle while minimizing the impact of parasitic inductance and capacity, which manifest as continuous interference. The timing of voltage application is synchronized with the measurement sampling to optimize signal-to-noise ratio
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 easy and non-destructive evaluation of crystal defects across the entire semiconductor wafer surface, including carrier lifetime assessment, facilitating efficient semiconductor wafer manufacturing by providing real-time quality control.
Implementation Method 1
A contact maker where a metal (Schottky electrode) liquefied at room temperature makes contact with a semiconductor wafer
Implementation Method 2
a means for compensating for parasitic inductance and parasitic capacity
Data Source
AI summary
A semiconductor wafer evaluation apparatus brings a contact maker (mercury liquefied at room temperature), as a Schottky electrode, into contact with a semiconductor wafer, intermittently applies a voltage from a pulse power supply, and evaluates the state (kinds, density) of point defects by an evaluation means based on the status of the electrostatic capacity of the semiconductor wafer. In this manner, the state (kinds, density) of the point defects in the plane of a large-diameter semiconductor wafer is directly evaluated using a large table.