Double-Beam Thermoreflectance for Wafer Conductive Path Inspection
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Solution Overview
Problem
Existing wafer-level testing methods for integrated circuit devices are time-consuming and limited in detecting small electrical defects, particularly resistant conductive paths, and existing charge-induced voltage contrast electron beam inspection techniques are expensive and slow, making them unsuitable for wafer mapping.
Innovation Solution
A Double Beam Thermoreflectance Spectroscopy (DBTRS) system using a pump laser to heat a target test area and a probe laser to detect reflectance changes, enabling continuous scanning and mapping of wafer conductivity, with thermal conductivity differences indicating different electrically conductive states.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If charge-induced voltage contrast electron beam inspection is used, then measurement precision for electrical defects is improved, but device complexity and cost increase significantly
Solution Approach 1:
The patent replaces the complex electron beam inspection system with an optical measurement system. Instead of using charged particles (electrons) to detect electrical defects, the invention uses laser beams (optical radiation) to heat test areas and detect thermal conductivity differences, thereby substituting a mechanical/electrical inspection method with a simpler optical one.
Solution Approach 2:
The patent introduces thermal conductivity as an intermediary property to detect electrical defects. Instead of directly measuring electrical properties with complex equipment, the system uses laser heating and measures thermal response as an intermediate indicator that reflects the underlying electrical conductivity state, simplifying the measurement process.
2Measurement precision
If charge-induced voltage contrast electron beam inspection is used, then measurement precision for electrical defects is improved, but productivity decreases due to slow inspection speed
Solution Approach 1:
The patent enables continuous scanning and mapping of wafers by moving the laser beam continuously across the wafer surface. The pump laser can be continuously focused on different test areas while the wafer remains stationary, allowing uninterrupted inspection progress and maintaining continuous useful action throughout the inspection process.
Solution Approach 2:
The patent performs preliminary heating of the test area using the pump laser before the probe laser measures the thermal response. This preliminary action prepares the test area in advance, allowing for rapid sequential measurements across multiple test areas without waiting for cooling periods between measurements.
3Productivity
If conventional wafer-level testing methods are used, then productivity is improved, but measurement precision for small electrical defects deteriorates
Solution Approach 1:
The patent applies local quality by focusing the laser beam on specific small test areas (such as individual vias or contact holes) rather than scanning the entire wafer uniformly. This localized heating and measurement approach allows high-resolution detection of small electrical defects while maintaining the ability to process multiple locations sequentially for high throughput.
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
Provides a high-throughput optical method for detecting electrical conductivity defects, allowing for continuous scanning and mapping of semiconductor wafers, identifying open, resistive, or shorted conductive paths with improved efficiency and cost-effectiveness compared to existing techniques.
Implementation Method 1
a pump laser to heat a target test area
Implementation Method 2
the first laser beam heating the conductive target test area
Implementation Method 3
a probe laser to detect reflectance changes
Implementation Method 4
Double Beam Thermoreflectance Spectroscopy (DBTRS) system using a pump laser to heat a target test area and a probe laser to detect reflectance changes
Implementation Method 5
thermal conductivity differences indicating different electrically conductive states
Implementation Method 6
identifying open, resistive, or shorted conductive paths
Data Source
AI summary
A method and system of detecting a conductive path state of a conductive target test area interconnect structure on a semiconductor wafer substrate, the method including directing a pump laser and probe laser incident on an exposed surface of a conductive target test area, the pump laser heating the conductive target test area which is interconnected to an underlying interconnect structure of a semiconductor wafer substrate. Measuring the intensity of the probe laser reflected by the exposed surface of the conductive target test area, and using the measured intensity of the reflected probe laser to determine a conductive path state of the conductive target test area and the underlying interconnect structure.