Charged Particle Beam Device Interferometer Height Measurement
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Solution Overview
Problem
Charged particle beam devices face challenges in achieving high-resolution and rapid inspection of semiconductor wafers and masks, particularly in detecting defects at the nanometer scale, due to instability in focusing and working distance during the inspection process.
Innovation Solution
A method and device that utilize an interferometer to determine the z-position of a sample by passing a reflected light beam through the objective lens assembly, allowing for precise focusing and stable working distance adjustment, thereby enhancing the accuracy and speed of charged particle beam inspection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a charged particle beam is used to inspect semiconductor wafers at high resolution, then small defects can be detected, but the inspection process becomes time-consuming and reduces production throughput
Solution Approach 1:
The system performs preliminary focus adjustment and working distance stabilization using the interferometer before the actual inspection process begins. This preliminary action ensures that the charged particle beam is optimally focused on the wafer surface, eliminating the need for time-consuming focus adjustments during inspection and thereby maintaining high production throughput while achieving high-resolution defect detection
2Productivity
If the inspection process is accelerated to increase throughput, then production efficiency improves, but focus stability and working distance control deteriorate
Solution Approach 1:
The interferometer continuously monitors the working distance between the objective lens assembly and the wafer surface in real-time during the inspection process. This feedback mechanism allows the system to maintain optimal focus conditions even at high inspection speeds, ensuring that focus stability is preserved while achieving high throughput by eliminating the need for slow, iterative focus adjustments
3Measurement precision
If manual focus adjustment is used to achieve accurate focus, then inspection accuracy improves, but the complexity of operation increases and time is lost
Solution Approach 1:
The system performs automatic focus adjustment using the interferometer to measure the working distance and control the position of the objective lens assembly or wafer stage. This self-service mechanism eliminates the need for manual focus adjustment by operators, achieving high focus accuracy while simplifying operation and reducing the time required for focus setup
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 enables more precise and efficient inspection by ensuring accurate focus and stable working distance, improving the detection of small defects and increasing production throughput in semiconductor technology.
Implementation Method 1
an interferometer arranged to receive a reflected light beam which passes through the bore of the objective lens assembly
Data Source
AI summary
A method of operating a charged particle beam device is disclosed, including focusing a charged particle beam onto a sample with an objective lens assembly; passing a reflected light beam through a bore of the objective lens assembly to an interferometer; and interferometrically determining a z-position of the sample with the interferometer. A charged particle beam device is disclosed, including a charged particle beam generator which has a charged particle source. A charged particle path for the charged particle beam extends through a bore of an objective lens assembly toward a sample stage. An interferometer is arranged to receive a reflected light beam which passes through the bore of the objective lens assembly.