Electron Microscope Two-Stage Irradiation for High Aspect Ratio Hole Imaging
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
In high aspect ratio memory holes, secondary electrons or reflected electrons from the bottom surface are difficult to detect due to asymmetrical charging of the side walls, making it challenging to observe the bottom surface using a scanning electron microscope.
Innovation Solution
The electron microscope employs a two-stage irradiation process, first neutralizing the charge on the sample surface and then using a random or alternating scan pattern to irradiate the hole bottom with an electron beam, reducing the impact of sidewall charging and enhancing electron detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the periphery or side wall of the memory hole is irradiated with an electron beam, then the sample surface is charged, but the secondary electron or reflected electron receives an asymmetrical force from the charge and is difficult to exit from the memory hole
Solution Approach 1:
The patent applies preliminary action by performing a first irradiation process that scans the electron beam across the upper end opening of the memory hole before the actual imaging process. This preliminary scanning neutralizes the charge accumulation on the side walls, preventing the asymmetrical charging that would otherwise deflect secondary electrons and reflected electrons away from the detector. By preparing the charge state in advance, the patent ensures that subsequent electron detection is not compromised by charging effects.
Solution Approach 2:
The patent converts the harmful charging effect into a beneficial neutralization process. The electron beam, which initially causes harmful asymmetrical charging when irradiating the side walls, is instead used in a controlled scanning manner to neutralize the charge on the upper end opening and side walls. This transforms the electron beam from a source of harm into a tool for eliminating the harmful charging effect, allowing secondary and reflected electrons to exit the memory hole unimpeded.
2Productivity
If the aspect ratio of the memory hole becomes higher, then the degree of integration increases, but the secondary electron or reflected electron from the bottom surface is difficult to reach an upper end opening
Solution Approach 1:
The patent performs preliminary scanning of the upper end opening with the electron beam before imaging the bottom surface. This preliminary action neutralizes charge accumulation on the side walls that would otherwise create asymmetrical forces preventing electrons from the bottom surface from reaching the upper opening. By preparing the charge environment in advance, the patent enables electron detection even in high aspect ratio structures.
Solution Approach 2:
The patent employs periodic action through the two-stage irradiation process: a first irradiation process that scans the upper end opening periodically to neutralize charge, followed by a second irradiation process that images the bottom surface. This periodic neutralization ensures that charge accumulation does not build up to levels that would prevent electron detection, maintaining measurement precision even as aspect ratio and integration density increase.
3Measurement precision
If a two-stage irradiation process is used to neutralize charge and image the hole bottom, then electron detection is improved, but the imaging process becomes more complex
Solution Approach 1:
The patent applies universality by using the same electron beam and detector system to perform both the charge neutralization function (first irradiation process) and the imaging function (second irradiation process). The electron beam serves multiple purposes: it neutralizes charge during scanning and also provides the signal for imaging the bottom surface. This multi-functionality reduces the need for additional specialized equipment, thereby limiting the increase in device complexity despite the two-stage process.
Solution Approach 2:
The first irradiation process serves as a preliminary preparation step that enables the second imaging process to succeed. By neutralizing the charge on the upper end opening and side walls beforehand, the patent removes the primary obstacle to electron detection. This preliminary action simplifies the overall process logic: prepare the charge state, then image, rather than requiring complex real-time charge compensation mechanisms during imaging.
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 method allows for accurate imaging of the hole bottom by minimizing electron deflection and improving the signal-to-noise ratio, enabling effective observation of high aspect ratio patterns.
Implementation Method 1
irradiating the sample with an electron beam and detecting a secondary electron or reflected electron generated from the sample
Implementation Method 2
irradiating the sample with an electron beam and detecting a secondary electron or reflected electron generated from the sample
Implementation Method 3
a first irradiation process of specifying a position of a hole bottom by scanning the sample with the charged particle beam
Data Source
AI summary
An electron microscope includes a stage on which a sample is capable of being placed, a beam generator, a detector, a display, and a controller. The beam generator emits a charged particle beam with which the sample is irradiated. The detector detects a secondary electron or an electron generated from the sample by irradiation with the charged particle beam. The display displays an image of the sample based on a signal from the detector. The controller executes a first irradiation process of specifying a position of a hole bottom by scanning the sample with the charged particle beam when capturing an image of the hole bottom of a hole provided in the sample, and executes a second irradiation process of imaging a shape of the hole bottom by irradiating the hole bottom with the charged particle beam via the hole.