Optical Coating Stack With Sm Oxide Buffer for High-Rate MgF2 Deposition
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Solution Overview
Problem
Existing sputtering methods for forming fluoride layers on metal oxides in optical devices result in optical absorption and degradation due to reaction between the sputter material and substrate, leading to unsatisfactory optical performance, especially at high deposition rates.
Innovation Solution
A buffer layer of samarium oxide or ytterbium oxide is introduced between the metal oxide substrate and the magnesium fluoride layer to suppress optical absorption, using reactive sputtering to form a continuous film with controlled reaction conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high-rate sputter deposition is used to increase productivity, then film deposition speed increases, but optical absorption occurs at the interface between the fluoride layer and substrate
Solution Approach 1:
A buffer layer made of metal oxide (such as silicon oxide, aluminum oxide, or magnesium oxide) is introduced as an intermediary between the fluoride layer and the substrate. This buffer layer prevents direct contact between fluorine and the substrate, thereby suppressing optical absorption at the interface while allowing high-rate sputter deposition to proceed. The buffer layer acts as a protective mediator that resolves the harmful interaction between fluorine and the substrate.
Solution Approach 2:
The buffer layer is formed on the substrate surface before depositing the fluoride layer. This preliminary action prepares the substrate surface by creating a protective metal oxide layer that will prevent subsequent harmful reactions during fluoride deposition. By performing this protective action in advance, the system enables high-rate deposition without interface absorption issues.
2Productivity
If the distance between target and substrate is decreased to speed up deposition, then film deposition rate increases, but charged particle damage to substrate and film increases
Solution Approach 1:
The buffer layer serves as a mediator that protects the substrate from charged particle damage. By placing this protective layer between the substrate and the plasma environment, the buffer absorbs or mitigates the harmful effects of charged particles while allowing the deposition process to continue at high rates with reduced damage to both substrate and fluoride layer.
3Productivity
If input power is increased to increase plasma density and speed up deposition, then film deposition rate increases, but reaction between sputter material and substrate material becomes harder to control
Solution Approach 1:
The buffer layer of metal oxide acts as a controlled intermediary that regulates the interaction between fluorine and the substrate. Even when high input power is used to increase deposition rate, the buffer layer provides a stable, controlled interface that prevents uncontrolled reactions between fluorine and the substrate materials, thereby maintaining manufacturing precision alongside high productivity.
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 solution achieves high optical transmittance and reduced absorption in the visible light region, enhancing the performance of optical devices by stabilizing the interface and preventing film degradation.
Implementation Method 1
A sputtering method is a method of forming films by sputtering a material in an atomic state using charged particles, such as a plasma
Implementation Method 2
A sputtering method is a method of forming films by sputtering a material in an atomic state using charged particles, such as a plasma
Implementation Method 3
a step of forming a samarium oxide layer or an ytterbium oxide layer on a base member having a surface formed of a metal oxide by reactive sputtering using a metal target formed of samarium or ytterbium
Data Source
AI summary
An optical device includes, in sequence, a surface formed of a metal oxide, a samarium oxide-containing layer in contact with the surface formed of a metal oxide, and a magnesium fluoride-containing layer in contact with the samarium oxide-containing layer so as to suppress optical absorption resulting from high-rate sputter deposition of a magnesium fluoride-containing layer on a surface formed of a metal oxide.