For heater made mainly of MoSi2, glass component is generally added to MoSi2 in order to adjust resistivity and improve oxidation resistance. We have developed an MoSi2 heater using pure SiO2 as glass ingredient, resulting in a high-purity oxidation protection layer being formed on the heating element surface. This enables superior performance compared with conventional products.
The high-purity oxidation protection layer takes a great part in suppressing the oxygen permeability compared to conventional products.
This advantage results in a product with extremely long life in high-temperature thermal cycle processing conditions.
2D schematic images of oxidation protection layer on surface of heater
Comparison of reducing rate of element's diameter
It's possible to slow down reducing rate of element's diameter. Our heater gives off an initial radiant heat for a long time.
Super Clean (SC) Grade Product
MoSi2 heater has been widely used as a high-temperature specification heater in an oxidizing atmosphere.
In recent years, quality requirements for each heat-treated product such as semiconductor wafers are becoming stricter, it is necessary to suppress the evaporation of impurities from the heater surface.
To meet the demands of customers needing low impurities heat treatment environments, we developed a Super Clean (SC) grade MoSi2 heater, with no dispersion of alkaline metals or heavy metal elements even when electrically heated to high temperatures.
SEM images and EPMA analysis results of quartz inner wall
- 1Au for EPMA (Electron Probe Micro Analyzer) observation, SiO2 (Si, O) from quartz and Au evaporated for analysis are excluded.
- 2The Au was deliberately stripped off and accumulated. It is apparent that the surface of inner wall is smooth with no impurities on it.
Anti- "Pest" Grade
The conventional heater was not suitable for long-term use at 500℃ due to the "pest". However, our anti- "pest" grade heater causes hardly any "pest" with optimization of composition of glass components, even in this temperature range.
This new heater is expected for use when temperatures quickly rise and drop, and can even maintain low temperatures, something that was difficult up to now.
What is a "pest" reaction?
E. Fitzer and K. Reinmuth: Vortrag Nr. 37.6 (1968)
At temperatures of 1,000℃ and higher, MoSi2 forms an excellent anti-oxidation SiO2 layer, as Si is selected according to the formula below (Domain III) whereas at 600℃ and below, Mo and Si are oxidized simultaneously, transforming to powder. The pulverizing phenomenon is called "pest". If MoO3 is formed, further pulverization takes place due to volume expansion in forming and high evaporation pressure.
Domain Ⅰ: 2MoSi2 + 7O2 → 2MoO3 + 4SiO2
Domain Ⅲ: 5MoSi2 + 7O2 → Mo5Si3 + 7SiO2
Domain Ⅴ: 2MoSi2 + 5O2 → 2MoO3 + 4SiO
The comparison test of anti- "pest" performance Ⅰ
Thermal cycle test at room temperature and maintaining 480℃ temperature for 10 hours
The comparison test of anti- "pest" performance Ⅱ
Test furnace for continuous current test
Appearance after continuous current test at furnace temperature of 400℃
Specially Designed Heater
As customer requirements are diversifying, heater need to be made in various shapes.
We are able to propose shapes of heaters for different applications. Moreover, we can process them into special shapes that minimize the number of terminals which dissipate heat as much as possible. Accordingly, we are able to provide MoSi2 heater with uniform heating as well as energy efficiency.
(for quick heating)
(for heating substrates of various kinds)
Irregular panoramic heater
(for partial heating)
Panoramic modular heater
(with excellent heating uniformity in a cylindrical area)
These products are dealt by JX Metals Trading Co., Ltd.
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