Metal Pattern Inspection Using Pulsed Voltage and Focused Ion Beam
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional methods for inspecting wiring defects, such as disconnections, result in low contrast between defective and non-defective regions due to similar electrical potentials, making it difficult to locate disconnections accurately.
Innovation Solution
Apply a pulsed voltage to the metallic pattern on a substrate and use a focused ion beam to scan in a raster mode, creating distinct patterns on the secondary charged particle image based on voltage changes, allowing for clear identification of disconnections and short circuits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a conventional DC voltage is applied to the metallic pattern for inspection, then the electrical potential on the surface becomes uniform, but the contrast between defective and non-defective regions becomes low making it difficult to locate disconnections
Solution Approach 1:
The patent applies a pulsed voltage that periodically changes in level with time to the metallic pattern. This periodic voltage creates corresponding periodic changes in the electrical potential on the surface, which generate a time-varying secondary charged particle signal. By synchronizing the detection with the voltage pulse timing, the system can distinguish between regions that respond to the pulsed voltage (non-defective) and regions that do not (defective), thereby achieving high contrast imaging for disconnection detection.
2Productivity
If the voltage cycle is made longer to match the scanning cycle, then the image resolution improves, but the detection speed decreases and time consumption increases
Solution Approach 1:
The patent employs a pulsed voltage with a cycle period shorter than the scanning cycle. This allows multiple voltage pulses to be applied during a single scanning cycle, enabling the system to capture multiple frames of secondary charged particle images. By processing these multiple frames, the system achieves both high inspection speed and accurate disconnection detection without requiring the voltage cycle to match the slower scanning cycle.
3Measurement precision
If a pulsed voltage with short cycle is applied, then the inspection speed increases, but the electrical potential stability decreases affecting image quality
Solution Approach 1:
The patent utilizes feedback by synchronizing the detection of secondary charged particles with the timing of the pulsed voltage application. The system detects the time-varying signal generated by the pulsed voltage and uses this temporal information to identify disconnections. This feedback mechanism allows the system to maintain high measurement precision even with the rapidly changing electrical potential, as the detection is locked to the voltage pulse timing rather than relying on potential stability.
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
Facilitates precise localization of disconnections and short circuits by generating contrasting patterns on the secondary charged particle image, reducing the time required for detection and enabling efficient repair through CVD film formation or sputtering techniques.
Implementation Method 1
scanning an inspection region on the inspection target substrate where the metallic pattern is formed using a focused ion beam cyclically in a raster scan mode to produce a secondary charged particle image of the inspection region as a function of intensities of secondary charged particles ejected from the inspection target substrate
Implementation Method 2
A pulsed voltage which changes in level with time is applied to the metallic pattern. A cycle of the pulsed voltage is selected to be shorter than a scanning cycle in which the focused ion beam is swept in a vertical or a horizontal direction
Data Source
AI summary
A metal pattern inspection method which applies a pulsed voltage to a metallic pattern, sets a cycle of the pulsed voltage to be shorter than a scanning cycle in which a focused ion beam is swept, indicating only a region of a secondary charged particle image corresponding to a portion of the metallic pattern which is isolated by a wire breakage and to which the pulsed voltage is applied in the form of a first pattern created as a function of surface electrical potentials changing in level with time, detecting, as a disconnection, a boundary between the first pattern and a second pattern created as a function of surface electrical potentials not changing in level with time, and determining whether there is a breaking of or a short circuit in the metallic pattern based on the presence or absence of the disconnection.