Photomask Absorbing Layer Segmentation for CD Uniformity
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
As semiconductor device feature sizes shrink below the wavelength of light used in photolithography, the manufacturing of photomasks becomes challenging due to sensitivity in critical dimension (CD) uniformity and image fidelity, particularly in maintaining line width roughness (LWR) and tilting angles, which affects production yield and pattern transfer precision.
Innovation Solution
A multiple-deposition technique is employed for an absorbing layer on a transparent substrate, using electroless plating or atomic layer deposition (ALD) to form a conformal and uniform first absorbing layer, followed by a thicker second absorbing layer, which improves stability, reduces processing time, and enhances CD uniformity and image fidelity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a single absorbing layer is deposited on the photomask substrate, then the manufacturing process is simple, but the critical dimension uniformity and image fidelity are poor
Solution Approach 1:
The absorbing layer is divided into multiple sub-layers (first absorbing layer and second absorbing layer) with different thicknesses and materials. The first absorbing layer has a thickness of 50-200 nm and the second absorbing layer has a thickness of 20-50 nm, creating a segmented structure that improves critical dimension uniformity while managing complexity through functional differentiation.
Solution Approach 2:
The patent employs composite material structure by combining different absorbing materials in multiple layers. The first absorbing layer uses materials such as chromium, molybdenum, or tungsten, while the second absorbing layer uses different materials to achieve optimal image fidelity and critical dimension control, resolving the contradiction between precision and complexity.
2Manufacturing precision
If the absorbing layer thickness is increased to improve pattern fidelity, then line width roughness increases, but if thickness is decreased then pattern transfer precision deteriorates
Solution Approach 1:
The total absorbing layer thickness is segmented into two distinct layers with different thickness ranges. The first absorbing layer (50-200 nm) provides the primary absorption function while the second absorbing layer (20-50 nm) fine-tunes the pattern fidelity. This segmentation allows optimization of each layer's thickness to minimize line width roughness while maintaining pattern transfer precision.
Solution Approach 2:
The patent optimizes the thickness parameters of each absorbing layer independently. By setting the first absorbing layer thickness between 50-200 nm and the second absorbing layer thickness between 20-50 nm, the solution changes the thickness parameters to achieve the optimal balance between pattern transfer precision and line width roughness control.
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 results in improved critical dimension uniformity, reduced line width roughness, and better image fidelity, leading to increased production yield and enhanced device performance by maintaining precise pattern transfer during photolithography.
Implementation Method 1
using electroless plating or atomic layer deposition (ALD) to form a conformal and uniform first absorbing layer
Implementation Method 2
using electroless plating or atomic layer deposition (ALD) to form a conformal and uniform first absorbing layer
Data Source
AI summary
A method of manufacturing a photomask includes depositing a first absorbing layer over a substrate, patterning the first absorbing layer using a photoresist, and depositing a conformal second absorbing layer along surfaces of the first absorbing layer.