Single Pole Aperture Plates for Overlay Metrology
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Solution Overview
Problem
Existing semiconductor lithography processes face challenges in accurately measuring extremely scaled patterns due to signal crosstalk and impact from neighboring patterns, leading to inadequate overlay control in semiconductor manufacturing.
Innovation Solution
The use of single pole 'X' and 'Y' aperture plates for diffraction pattern measurement, which can be used exclusively or in sequence with an 'X-Y' aperture plate, to collect X-axis and Y-axis diffraction data independently or simultaneously, mitigating signal crosstalk and allowing for reliable overlay error measurement without segment pitch limitations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional aperture plates are used for diffraction pattern measurement, then measurement can be performed, but signal crosstalk from neighboring patterns degrades measurement precision
Solution Approach 1:
The aperture plate is divided into multiple isolated poles (e.g., four poles arranged in a cross pattern) instead of a continuous aperture. Each pole independently transmits diffraction orders from specific gratings, spatially separating the measurement signals and eliminating crosstalk between adjacent patterns while maintaining measurement capability for each individual grating.
2Productivity
If tight pattern pitch is used to increase device density, then productivity improves, but signal from neighboring patterns impacts measurement accuracy
Solution Approach 1:
The segmented aperture plate with isolated poles allows each pole to independently measure diffraction from its corresponding grating without interference from neighboring patterns. This enables accurate overlay measurement even when gratings are closely spaced for high device density, as the physical separation of aperture regions prevents signal mixing.
3Speed
If X-axis and Y-axis diffraction measurements are performed simultaneously, then measurement speed improves, but signal crosstalk between axes degrades measurement precision
Solution Approach 1:
The aperture plate features spatially separated poles oriented along different axes (e.g., horizontal poles for X-axis measurements, vertical poles for Y-axis measurements). This geometric segmentation allows simultaneous collection of diffraction signals from both axes without crosstalk, as each pole group is physically isolated and collects signals only from its designated orientation.
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 improved overlay error measurement and target design tolerance, effectively addressing the limitations of existing techniques by reducing X- and Y-signal crosstalk and allowing for accurate measurement of aggressively scaled patterns.
Implementation Method 1
a radiation beam is directed through the first metal aperture plate to irradiate a composite grating disposed on a substrate, where the radiation beam directed through the first metal aperture plate provides a first diffraction pattern
Data Source
AI summary
A method for performing DBO measurements utilizing apertures having a single pole includes using a first aperture plate to measure X-axis diffraction of a composite grating. In some embodiments, the first aperture plate has a first pair of radiation-transmitting regions disposed along a first diametrical axis and on opposite sides of an optical axis that is aligned with a center of the first aperture plate. Thereafter, in some embodiments, a second aperture plate, which is complementary to the first aperture plate, is used to measure Y-axis diffraction of the composite grating. By way of example, the second aperture plate has a second pair of radiation-transmitting regions disposed along a second diametrical axis and on opposite sides of the optical axis. In some cases, the second diametrical axis is substantially perpendicular to the first diametrical axis.