Reticle Reduced Transmission Regions Defocus Detection
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Solution Overview
Problem
Current lithography processes face challenges in accurately detecting defocus conditions during semiconductor fabrication, leading to pattern errors and reduced production yield due to the inability to distinguish between plus and minus defocus conditions, which affects the focus position and pattern quality.
Innovation Solution
A reticle with reduced transmission regions is introduced, where specific regions with a lower optical transmission factor are created in the glass plate using high-energy lasers to scatter light, allowing for asymmetric light patterns that enable differentiation between focus conditions without the need for opaque materials on both sides of the reticle, thereby providing feedback for adjusting the focus.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If opaque materials are used on both sides of the reticle to detect defocus conditions, then the ability to distinguish between plus and minus defocus conditions is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The patent extracts the defocus detection function from the traditional dual-sided opaque material structure and implements it using a single-sided reduced transmission region. This simplifies the reticle structure by removing the need for opaque materials on both sides while maintaining the ability to detect defocus conditions.
Solution Approach 2:
The patent applies local quality by creating a specific region with reduced transmission properties in the glass plate rather than using opaque materials throughout. This localized modification allows defocus detection while preserving light transmission in other areas, reducing overall device complexity.
2Manufacturing precision
If reduced transmission regions are created using high-energy lasers to scatter light, then the manufacturing precision of asymmetric light patterns is improved, but the use of energy and manufacturing complexity increase
Solution Approach 1:
The patent changes the transmission parameter of the glass plate by creating regions with reduced transmission properties through laser treatment. This parameter modification enables asymmetric light patterns necessary for defocus detection while using a single high-energy laser process instead of multiple manufacturing steps.
3Ease of manufacture
If traditional symmetric reticle patterns are used, then the manufacturing process is simpler, but the ability to detect focus position and distinguish defocus conditions is lost
Solution Approach 1:
The patent introduces asymmetry into the reticle design by creating a reduced transmission region that is not symmetrically positioned relative to the light path. This asymmetric structure causes different light transmission patterns for plus and minus defocus conditions, enabling focus detection while maintaining relatively simple manufacturing processes.
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 solution allows for precise measurement and adjustment of focus positions, improving pattern quality and reducing production errors by enabling the detection of plus or minus defocus conditions, thus enhancing the accuracy and efficiency of the lithography process.
Implementation Method 1
specific regions with a lower optical transmission factor are created in the glass plate using high-energy lasers to scatter light
Data Source
AI summary
A reticle for a semiconductor lithography process includes a glass plate having regions with a reduced optical transmission factor. The regions may include arrays of elements comprising defects such as cracks or voids which are formed by laser pulses. The regions may be adjacent to openings in an opaque material at the bottom of the reticle to shield the openings from a portion of the light which illuminates the reticle from the top. As a result, the light which exits the reticle and is used to pattern a substrate has an asymmetric intensity. This allows the substrate to be patterned with an inspection mark which indicates whether a defocus condition exists, and whether there is a positive or negative defocus condition. Related methods use a reticle to form a pattern on a substrate and for adjusting a focus condition using a reticle.