Blanking Control Circuit for Electron Beam Measurement
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Solution Overview
Problem
Measurement and inspection devices face challenges in achieving accurate measurements of deep grooves and deep holes on semiconductor substrates due to limitations in electron beam acceleration voltage, leading to reduced CD and positional accuracy.
Innovation Solution
The device incorporates a blanking unit with a first and second blanking electrode, along with a blanking control circuit that generates variable positive and negative voltages based on the electron beam's acceleration voltage, allowing for a wide range of voltage compatibility and reducing noise influences on the electron beam's stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the acceleration voltage of the electron beam is increased to measure deep grooves and deep holes, then measurement accuracy is improved, but the device must accommodate a wider range of acceleration voltages which increases device complexity
Solution Approach 1:
The blanking electrode voltage is made dynamically adjustable to match different electron beam acceleration voltages. The control circuit generates appropriate blanking voltages based on the selected acceleration voltage, allowing the system to adapt to various measurement conditions without requiring multiple fixed configurations.
Solution Approach 2:
The system changes the blanking electrode voltage parameter according to the acceleration voltage setting. By varying the blanking voltage in proportion to the acceleration voltage, the device maintains optimal performance across a wide range of acceleration voltages, resolving the contradiction between measurement accuracy and device complexity.
2Device complexity
If a single blanking electrode is used, then device complexity is reduced, but the electron beam cannot be properly blanked at high acceleration voltages leading to reduced measurement accuracy
Solution Approach 1:
The blanking function is segmented into two separate blanking electrodes instead of using a single electrode. This segmentation allows each electrode to handle specific voltage ranges effectively, with the first electrode handling lower voltages and the second electrode handling higher voltages, thereby maintaining measurement accuracy across the full voltage range.
Solution Approach 2:
The control circuit dynamically selects and activates the appropriate blanking electrode based on the acceleration voltage setting. This dynamic switching enables the system to use the optimal electrode for each voltage level, achieving proper beam blanking without requiring both electrodes to be constantly active, thus balancing complexity and performance.
3Stability of the object's composition
If voltages are applied to blanking electrodes to cancel noise, then electron beam stability is improved, but the control circuit complexity increases
Solution Approach 1:
The control circuit uses feedback from the acceleration voltage setting to automatically generate the appropriate blanking voltages. This feedback mechanism ensures that the blanking electrodes receive the correct voltage levels to cancel noise without requiring manual adjustment or complex external control systems.
Solution Approach 2:
The control circuit is designed to automatically generate the necessary blanking voltages based on the acceleration voltage selection, making the noise cancellation function self-regulating. This self-service approach reduces the need for additional complex control mechanisms while maintaining electron beam 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
This configuration enables the measurement and inspection device to maintain high accuracy across various electron beam acceleration voltages, reducing the impact of circuit noise and disturbance on the electron beam's stability and precision.
Implementation Method 1
a first blanking electrode, which includes two electrodes that sandwich an irradiation position on a plane perpendicular to an irradiation direction of an electron beam in a center and that face each other in a direction perpendicular to the plane
Implementation Method 2
an electron beam (electron ray) is irradiated onto an object wafer (sample) while being scanned, and energy such as secondary electrons thus generated are detected
Data Source
AI summary
A low noise blanking unit corresponds to a wide range of acceleration voltages (from several times higher than related voltages to low acceleration voltages) of an electron beam. A blanking unit of the measurement and inspection device includes a blanking control circuit, in which (i) an upper and a lower blanking electrodes are arranged in the irradiation direction of an electron beam; electrodes on the reverse sides of two opposing electrodes in each of the blanking electrodes arranged in the same direction are connected with the ground, (ii) when blanking is ON, positive voltages are output to remaining electrodes of the upper blanking electrode and negative voltages are output to remaining electrodes of the lower blanking electrode, and (iii) when the blanking is OFF, the same ground reference signal is output to the remaining electrodes of the upper blanking electrode and to the remaining electrodes of the lower blanking electrode.