EUV Multilayer Mirror Cs Interlayer Diffusion Barrier
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Multilayer mirrors used in EUV lithography face challenges due to interlayer diffusion, which reduces the sharpness of interfaces and affects optical performance, particularly at the interfaces between materials like B and La, leading to reduced reflectivity for EUV radiation with wavelengths around 6.9 nm.
Innovation Solution
A multilayer mirror design incorporating alternating layers of U, Th, or La with B4C, separated by a Cs interlayer in solid form, which prevents chemical reaction and diffusion, maintaining interface sharpness and enhancing reflectivity for EUV radiation in the 6.4 nm to 7.2 nm range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multilayer mirrors with alternating layers of metal (La, U, Th) and B or B compound (B4C, B9C) are used to reflect EUV radiation, then reflectivity for EUV radiation is improved, but interlayer diffusion occurs reducing interface sharpness and adversely affecting optical performance
Solution Approach 1:
An interlayer comprising Cs in substantially solid form is introduced between the metal layer (La, U, or Th) and the B or B compound layer (B4C, B9C, or B). This Cs interlayer acts as a diffusion barrier that prevents chemical interaction and atomic diffusion between the adjacent metal and boron layers, thereby maintaining sharp interfaces while preserving the reflective properties of the multilayer mirror structure.
2Strength
If high chemical reactivity is present between B and La at the interface, then chemical bonding occurs, but this leads to formation of LaB6 and reduction in interface sharpness
Solution Approach 1:
The Cs interlayer is positioned between the La layer and the B or B compound layer to physically separate them and prevent direct chemical contact. This intermediary layer blocks the formation of LaB6 compounds at the interface, maintaining the desired sharp interface between the functional layers while still allowing the multilayer structure to achieve high reflectivity through constructive interference of EUV radiation.
3Force
If heavy La atoms arrive at the surface of light B layer atoms with high kinetic energy, then implantation occurs up to depth of around 2 nm, but this reduces interface sharpness
Solution Approach 1:
The Cs interlayer serves as a protective barrier that absorbs and dissipates the kinetic energy of incoming La atoms before they can penetrate into the B or B compound layer. By placing this intermediary layer between the two functional layers, the patent prevents La atom implantation and maintains the sharp interface definition required for optimal optical performance.
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
The use of Cs interlayers stabilizes the interface and maintains reflectivity, reducing power losses and improving optical performance by preventing interlayer diffusion, thus enhancing the capability to print smaller features in EUV lithography.
Implementation Method 1
Such a multilayer mirror reflects the EUV radiation according to Bragg's Law
Implementation Method 2
at least one of the first layers is separated from the second layer by an interlayer disposed between the at least one of the first layers and the second layer, the interlayer comprising Cs in substantially solid form
Data Source
AI summary
A multilayer mirror constructed to reflect radiation having a wavelength in the range of 6.4 nm to 7.2 nm. The multilayer mirror has alternating layers, including a first layer and a second layer. The first and second layers are selected from the group consisting of: U, or a compound or nitride thereof, and B4C layers; Th, or a compound or nitride thereof, and B4C layers; La, or a compound or nitride thereof, and B9C layers; La, or a compound or nitride thereof, and B4C layers; U, or a compound or nitride thereof, and B9C layers; Th, or a compound or nitride thereof, and B9C layers; La, or a compound or nitride thereof, and B layers; U, or a compound or nitride thereof, and B layers; C, or a compound or nitride thereof, and B layers; Th, or a compound or nitride thereof, and B layers.