Conductive Grease Dry Etching for Diffractive Optical Elements
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Solution Overview
Problem
Conventional dry etching methods for manufacturing diffractive optical elements (DOEs) face instability in etching rates and depths, particularly when multiple substrates are processed simultaneously, due to variations in vacuum grease thickness affecting sheath voltage and substrate temperature.
Innovation Solution
A dry etching method using conductive grease instead of vacuum grease to maintain a stable sheath voltage, combined with the use of ICP, CCP, ECR, or NLD plasma, and substrates like ZnSe polycrystal or SiO2, ensures consistent etching rates and depths across multiple substrates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If vacuum grease is used to attach the insulative substrate to the conductor for cooling, then substrate temperature control is improved, but etching rate stability deteriorates due to thickness variations affecting sheath voltage
Solution Approach 1:
The patent changes the electrical conductivity parameter of the grease from insulative (vacuum grease) to conductive (e.g., carbon-based grease with resistivity 10-1000 Ω·cm). This parameter change allows the grease to serve dual functions: maintaining thermal contact for substrate cooling while providing electrical conductivity to stabilize sheath voltage and eliminate etching rate variations.
Solution Approach 2:
The patent employs composite materials for the grease, specifically carbon-based compounds mixed with lubricating oils or greases. This composite structure provides both the thermal conductivity needed for cooling and the electrical conductivity required for voltage stabilization, resolving the contradiction between temperature control and etching stability.
2Productivity
If multiple insulative substrates are simultaneously dry-etched to improve efficiency, then productivity is improved, but etching depth uniformity deteriorates due to variations in grease thickness among substrates
Solution Approach 1:
By changing the electrical conductivity parameter of the grease, the patent enables simultaneous processing of multiple substrates with stable etching rates. The conductive grease equalizes potential across all substrate-conductor contacts, ensuring uniform sheath voltage and etching depth even when grease thickness varies among substrates in the batch.
3Reliability
If vacuum grease is used to provide electrical contact between conductor and electrode, then electrical conductivity is improved, but substrate cooling efficiency deteriorates due to insulative properties
Solution Approach 1:
The patent uses composite materials with both thermal and electrical conductivity properties. The carbon-based grease combines the thermal conductivity of metal particles with the lubricating properties of oil or grease, enabling simultaneous electrical contact and efficient heat transfer from substrate to cooled electrode.
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 method stabilizes etching rates and depths, allowing for high-quality DOE manufacturing with excellent reproducibility and reduced substrate deformation, even when processing multiple substrates simultaneously.
Implementation Method 1
the insulative substrate is attached to the conductor by means of a conductive grease
Implementation Method 2
positive ions in plasma 9 generated as a result of application of high-frequency power by means of RF power supplies 1a, 1b collide with a surface of insulative substrate 4
Implementation Method 3
positive ions in plasma 9 generated as a result of application of high-frequency power by means of RF power supplies 1a, 1b collide with a surface of insulative substrate 4 because of intense electric field in a sheath region 10 created above insulative substrate 4
Implementation Method 4
conductor 6 is brought in electric, intimate contact with cooled electrode 7 by utilizing electrostatic attraction or the like, so that entire insulative substrate 4 is uniformly cooled through conductor 6
Data Source
AI summary
A dry etching method is provided, in which dry etching is performed in such a manner that a conductor to which an insulative substrate is attached is brought in electric, intimate contact with an electrode. In the dry etching method, the insulative substrate is attached to the conductor by means of a conductive grease. A diffractive optical element manufactured with the dry etching method is also provided.