Local Pre-dose for LSI Pattern Edge Charging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Scanning electron microscopes face challenges in capturing accurate images of complex LSI patterns due to fluctuations in contrast and resolution caused by electron beam scanning direction, leading to inaccurate two-dimensional shape measurements and potential pattern damage during pre-dosing.
Innovation Solution
A sample observing method that selectively designates areas around pattern edges for local pre-dosing using the electron beam, controlling the initial charged state to minimize secondary electron return and optimize image capture, regardless of scanning direction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If interlace scanning is used to capture images of LSI patterns, then the scanning process can be completed, but contrast fluctuation and resolution variation occur depending on scanning direction
Solution Approach 1:
The patent applies preliminary action by performing pre-dose irradiation before actual image capture. The control unit determines areas requiring pre-dose based on pattern information, and irradiates these areas with electron beams at lower acceleration voltages (50-300 V) to establish optimal initial charged states, preventing contrast fluctuation and resolution variation during subsequent scanning
2Reliability
If pre-dose is applied to the entire observation area, then secondary electron return is reduced, but pattern damage occurs and throughput decreases
Solution Approach 1:
The patent applies local quality by selectively applying pre-dose only to specific areas around pattern edges where charging effects are most problematic. The control unit identifies these areas using pattern information and edge detection algorithms, then applies localized electron beam irradiation with controlled dose amounts, avoiding unnecessary irradiation to other areas and preventing pattern damage while maintaining detection reliability
Solution Approach 2:
The patent applies partial action by using lower acceleration voltages (50-300 V) for pre-dose compared to normal imaging voltages, and by controlling the pre-dose amount to be sufficient for charge control but not excessive to cause damage. This partial application of electron beam energy achieves the desired effect with reduced harmful impacts
3Productivity
If electron beam scans parallel to insulator pattern, then continuous irradiation occurs, but positive charge intensifies and secondary electrons return to sample surface
Solution Approach 1:
The patent applies preliminary action by pre-irradiating areas parallel to insulator patterns with electron beams at lower acceleration voltages before normal scanning. This establishes negative charged states that counteract the positive charge buildup during continuous scanning, preventing secondary electron return and maintaining detection efficiency throughout the scanning process
4Reliability
If local pre-dose area is designated around pattern edges, then secondary electron return is minimized, but additional processing steps are required
Solution Approach 1:
The patent applies self-service by using the SEM's own pattern recognition and control capabilities to automatically identify areas requiring pre-dose. The control unit uses stored pattern information and real-time edge detection to determine pre-dose areas, eliminating the need for external manual designation and integrating the process into the existing SEM workflow
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 high-accuracy pattern profile capture in complex LSI patterns with minimal throughput reduction and reduced pattern damage, improving image resolution and detection efficiency while maintaining scanning direction independence.
Implementation Method 1
electron beams emitted from an electron gun are deflected by a scanning deflector so that a secondary electron, reflecting electron and backscatter electron generated from the sample surface are detected
Implementation Method 2
the positive charge 303 on the sample surface is intensified because of continuous scanning with respect to the insulator portion
Implementation Method 3
the secondary electron 304 generated by the electron beam irradiation tends to be returned to the sample surface
Data Source
AI summary
Provided is a sample observing method wherein the effect on throughput is minimized, and a pattern profile can be obtained at high accuracy even in a complicated LSI pattern, regardless of the scanning direction of an electron beam. In the sample observing method, the presence or absence of an edge parallel to a scanning direction (707) of an electron beam is judged regarding an edge (708) of a pattern to be observed (S702); if the edge is present, an area in the vicinity of the pattern edge is designated as a local pre-dose area (709) (S703); a local pre-dose of an electron beam is performed, so that the initial charged state is controlled not to return secondary electrons generated by irradiation of an electron beam when an image is captured, to the surface of a sample.