EUV Blank Mask Conductive Mesh for Registration Error Correction
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Solution Overview
Problem
In extreme ultraviolet (EUV) lithography, existing methods struggle to correct mask registration errors due to the conductive layer covering the backside surface of reflection type photo masks, which prevents laser irradiation for deformation.
Innovation Solution
A blank mask design featuring a conductive layer with a checkerboard or mesh shape on the backside surface of the substrate, allowing light penetration for registration error correction, and an insulation layer that transmits light, enabling accurate alignment and attachment to an electrostatic chuck.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a conductive layer is formed on the entire backside surface of the mask substrate to enable electrostatic chuck attachment, then the attachment reliability is improved, but the ability to correct mask registration errors by laser irradiation deteriorates because the conductive layer blocks light
Solution Approach 1:
The conductive layer is segmented into a mesh pattern rather than being continuous, creating light transmission paths while maintaining electrical conductivity for electrostatic chuck attachment. This segmentation allows laser beams to pass through to correct mask registration errors while the conductive mesh maintains sufficient electrical contact for reliable attachment.
Solution Approach 2:
Different regions of the mask substrate backside have different properties: the conductive mesh provides electrical conductivity in specific locations while leaving other regions transparent for light transmission. This local differentiation allows simultaneous achievement of attachment reliability and registration error correction capability.
2Stability of the object's composition
If the conductive layer is made opaque to ensure good electrical contact with the electrostatic chuck, then the attachment stability is improved, but the light transmission for registration error correction is blocked
Solution Approach 1:
The conductive layer is designed as a mesh structure with inherent porosity, allowing light to pass through the gaps while the conductive material provides electrical contact. The mesh configuration maintains electrical stability while enabling light transmission for registration error correction.
Solution Approach 2:
The conductive layer functions as a composite structure combining electrical conductivity with optical transparency through its mesh geometry. This composite approach allows the layer to simultaneously provide stable electrical contact and transmit light for laser-based registration error correction.
3Reliability
If the entire backside surface is covered with conductive material, then the electrostatic chuck attachment is reliable, but the overlay accuracy correction capability is lost due to blocked laser irradiation
Solution Approach 1:
The conductive layer is divided into a mesh pattern that segments the backside surface, creating transparent corridors for laser beams to reach the mask substrate. This segmentation preserves electrical connectivity while enabling optical access for overlay accuracy correction.
Solution Approach 2:
The mesh conductive layer acts as an intermediary structure that mediates between the requirement for electrical contact and the need for light transmission. It provides a compromise solution that satisfies both electrostatic attachment reliability and laser-based correction capability.
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 design enables reliable correction of mask registration errors and improves the overlay accuracy of EUV photo masks by allowing light penetration through the conductive layer, enhancing the fabrication of high-precision semiconductor devices.
Implementation Method 1
The electrostatic chuck may be used to support the photo mask even when the circuit patterns of the photo mask are formed or the photo mask is handled during the lithography process
Implementation Method 2
the mask registration errors may be corrected by irradiating a laser onto a back side surface of a photo mask to deform a mask substrate
Data Source
AI summary
A blank mask includes a substrate having a first surface and a second surface which are opposite to each other. The substrate includes a trench having a predetermined depth from the second surface. A reflection layer is disposed on the first surface of the substrate to reflect extreme ultraviolet (EUV) rays. An absorption layer is disposed on the reflection layer opposite to the substrate to absorb EUV rays. A conductive layer is disposed in the trench to expose portions of the substrate. The conductive layer includes first conductive lines and second conductive lines intersecting the first conductive lines, and the exposed portions of the substrate are two dimensionally arrayed to have island shapes.