E-Beam Fine Alignment via Backscatter Waveform Derivative
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Solution Overview
Problem
Current lithographic technologies face challenges in achieving precise overlay control and critical dimension uniformity as feature sizes and pitches in integrated circuits continue to shrink, particularly with the limitations of conventional scanners and photoresists, leading to increased fabrication costs and potential inability to print via openings for extremely small pitches.
Innovation Solution
The implementation of complementary e-beam lithography (CEBL) that combines optical lithography with electron beam lithography (EBL) to pattern critical layers, using pitch division techniques and electron beam direct write tools with backscatter electron detectors for real-time alignment, enabling precise patterning of vias and metal line cuts, and extending the use of current optical lithography technology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional lithographic scanners are used to pattern smaller features, then manufacturing cost is reduced and throughput is maintained, but overlay precision and critical dimension uniformity deteriorate
Solution Approach 1:
The patent divides the patterning process into two separate lithographic steps: first patterning the mandrel structures, then patterning the final features using the mandrels as templates. This segmentation allows each step to be optimized independently - the first step uses conventional lithography for high throughput, while the second step achieves higher precision through the mandrel-assisted process
Solution Approach 2:
The mandrel structures serve as intermediary elements between the conventional lithographic patterning and the final high-precision features. The mandrels are formed by conventional lithography, then used as templates to guide the formation of final features with superior precision, acting as a mediator that bridges the gap between throughput-oriented and precision-oriented processes
2Manufacturing precision
If feature sizes and pitches are reduced to increase device density, then functional unit density is improved, but overlay control and critical dimension uniformity become more difficult to maintain
Solution Approach 1:
The mandrel structures are formed in advance as preliminary patterns that define the positions and dimensions of the final features. By pre-establishing these reference structures through conventional lithography, the subsequent patterning step can achieve better critical dimension uniformity since it uses the mandrels as precise templates rather than relying solely on direct lithographic patterning at the resolution limit
3Manufacturing precision
If multiple lithographic masks are used to pattern extremely small pitches, then patterning capability is improved, but fabrication cost increases
Solution Approach 1:
The patent uses the mandrel structures as physical templates or copies that define the pattern for the final features. Instead of using multiple complex masks to directly pattern the final features, the mandrels serve as reusable templates that simplify the patterning process - the second lithographic step essentially copies the mandrel pattern to create the final features, reducing the need for multiple specialized masks
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 enhances the ability to achieve precise alignment and patterning of small features, improving throughput and reducing costs by enabling high-volume manufacturing of advanced integrated circuits with smaller feature sizes and pitches, overcoming the limitations of conventional scanners and photoresists.
Implementation Method 1
detecting a time-resolved back-scattered electron (BSE) detection response waveform
Data Source
AI summary
Lithographic apparatuses suitable for, and methodologies involving, complementary e-beam lithography (CEBL) are described. In an example, a method of fine alignment of an e-beam tool includes projecting an electron image of a plurality of apertures of an e-beam column over an X-direction alignment feature of a wafer while moving the wafer along the Y-direction. The method also includes detecting a time-resolved back-scattered electron (BSE) detection response waveform during the projecting. The method also includes determining an X-position of every edge of every feature of the X-direction alignment feature by calculating a derivative of the BSE detection response waveform. The method also includes, subsequent to determining an X-position of every edge of every feature of the X-direction alignment feature, adjusting an alignment of the e-beam column to the wafer.