Evaporation Source Cap Body Projections for Top-Heat State
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Solution Overview
Problem
In induction heating systems for vapor deposition, achieving a top-heat state where only the upper layer of the vapor deposition material is heated while preventing excessive heat from reaching the lower layers, which can lead to thermal decomposition, is challenging due to uniform heating by the induction heating coil.
Innovation Solution
The evaporation source features a cap body with projections on its outer surface and a smaller winding pitch induction heating coil around the cap body compared to the crucible, enhancing resistance loss and calorific value to prioritize heating the cap body and maintain a top-heat state within the crucible.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If an induction heating coil is used to heat the crucible and cap body, then heating responsiveness is improved and heat can be dissipated quickly, but the entire crucible is heated uniformly causing excessive heat at the lower part (bottom-heat state)
Solution Approach 1:
The cap body is provided with protrusions on its outer surface that have corner parts with concentrated magnetic flux, creating localized high-temperature regions at the upper part of the crucible. This non-uniform structure causes preferential heating at specific locations (upper layer) rather than uniform heating throughout, resolving the bottom-heat state problem while maintaining fast heating response
Solution Approach 2:
The protrusions with corner parts are pre-designed on the cap body to concentrate magnetic flux at the upper region before heating begins. This preliminary structural arrangement ensures that when induction heating is applied, the upper layer is preferentially heated first, establishing the desired temperature gradient before the lower layers can overheat
2Temperature
If the cap body is heated to achieve top-heat state, then the upper layer vapor deposition material is efficiently vaporized, but the corner parts of projections generate excessive resistance loss and heat
Solution Approach 1:
The corner parts of the protrusions, which naturally generate excessive heat due to concentrated magnetic flux and resistance loss, are strategically positioned and shaped to serve as localized heating zones that benefit the vaporization process. The harmful excessive heat at corners is converted into a beneficial feature by designing the protrusions to direct this heat toward the upper layer vapor deposition material, improving vaporization efficiency without causing damage to the lower layers
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 configuration effectively achieves a top-heat state by increasing resistance loss at the cap body's projections, ensuring the vapor deposition material in the lower layers is not subjected to excessive heat, thereby preventing thermal deterioration.
Implementation Method 1
the crucible and the cap body are heated by Joule heat generated by resistance loss that is caused when induction current (eddy current) flows through the crucible and the cap body
Implementation Method 2
when the induction heating coil is charged with an AC current inside the vacuum chamber in a vacuum atmosphere, the crucible and the cap body are heated by Joule heat generated by resistance loss that is caused when induction current (eddy current) flows through the crucible and the cap body
Implementation Method 3
the crucible and the cap body are heated by Joule heat generated by resistance loss that is caused when induction current (eddy current) flows through the crucible and the cap body
Implementation Method 4
resistance loss will be augmented at the corner parts (edge parts) of the projections. In other words, the calorific value improves when the magnetic flux density to work on the cap body
Implementation Method 5
it becomes possible to cause the cap body to generate heat on a priority basis so that the entire crucible inclusive of the cap body can be made into the top-heat state
Implementation Method 6
the vapor deposition material inside the crucible is heated by heat conduction from a wall part of the crucible and radiant heat from the cap body
Implementation Method 7
the vapor deposition material inside the crucible is heated by heat conduction from a wall part of the crucible and radiant heat from the cap body
Implementation Method 8
the vapor deposition material inside the crucible is not vaporized or sublimated except from an upper layer portion that faces the discharge nozzle
Implementation Method 9
the vapor deposition material inside the crucible is not vaporized or sublimated except from an upper layer portion that faces the discharge nozzle
Data Source
AI summary
There is provided an evaporation source adapted for use in a vapor deposition apparatus in which by heating, in an induction heating method, a crucible filled with a vapor deposition material, the entire crucible including a cap body attains a top-heat state. An evaporation source is provided with: a crucible filled with the vapor deposition material; a cap body to close an upper surface opening of the crucible; and an induction heating coil disposed around the crucible and the cap body. Further, the cap body is provided with a discharge part which allows the passage of the vapor deposition material evaporated or sublimated by heating. The cap body is provided on an external surface thereof with projections each having a corner part.