Electric resistance heating devices – Heating devices – Continuous flow type fluid heater
Patent
1993-08-05
1996-09-24
Jeffery, John A.
Electric resistance heating devices
Heating devices
Continuous flow type fluid heater
F24H 110
Patent
active
055599249
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a fluid heater for resonance-heating a fluid to be heated by radiant heat. More particularly, the invention relates to a fluid heater capable of appropriately carrying out heating and temperature control, such as heating and temperature control of etching solution and resist removing solution after cleaning wafers made of silicon or the like in processes for manufacturing semiconductor devices, and heating and temperature control of oils for foodstuffs while the fluid to be heated is being supplied.
BACKGROUND ART
An example of an appropriate use of a fluid heater is described with reference to a temperature control unit for a semiconductor wafer treating solution shown in FIG. 10. In FIG. 10, a treating bath 100 is filled with treating solution 200. The treating solution 200 is forced to flow in a teflon piping 400 by a pump 300, heated by a fluid heater 500, filtered by a filter 600 to remove foreign substances contained in the treating solution, and returned to the treating bath 100. The temperature of the treating solution 200 in the treating bath 100 is detected by a sensor 700, and the controller 800 controls the fluid heater 500 so that the detected temperature approaches a preset temperature. In FIG. 10, numeral 510 denotes a box which incorporates the fluid heater 500, and numeral 900 denotes semiconductor wafers.
FIGS. 11(A) and 11(B) are respectively a perspective view and a sectional view of a conventional fluid filter. Specifically, a plurality of electric heaters 2 are provided on an external periphery of a fluid heating pipe unit 1 to heat fluid C introduced from an inlet pipe 31 and discharged through an outlet pipe 32. In this example, the fluid heater 2 comprises, in order from the inside, a fluid heating pipe unit 1, a clearance 7, an electric heater 2 formed with eight parallel members such as nichrome wire, kanthal wire and others, and insulation material 4.
In this case, the above described conventional fluid heater includes a problem as described below. The fluid heater heats fluid by radiant heat and, in this case, a temperature increasing rate of fluid to be heated by radiant heat is proportional to an energy density of absorption wavelength band of heated fluid (penetration energy in a unit time in a unit area) if a radiation area is fixed, and is proportional to the radiation area if the energy density is fixed. In other words, the energy density needs to be increased or the radiation area needs to be expanded in order to raise the heating rate.
By the way, the higher the temperature of the electric heater 2 is, the higher the energy density can be increased according to the Stefan-Boltzmann law. However, unless the energy is absorbed only by the fluid heating pipe unit 1 when the electric heater 2 is set to a high temperature, the temperature of the electric heater 2 rises, resulting in melting loss. Otherwise, even though the radiation area is expanded by increasing the number of members of the electric heater 2, the electric heater 2 is short-circuited, resulting in melting loss. In addition, part of the radiant heat is radiated outwardly from the external periphery of the electric heater 2 and absorbed by the insulation material 4 and therefore it does not contribute to the heating of the fluid.
On the other hand, the radiation area can be expanded to raise the heating rate but a larger fluid heating pipe unit 1 is required and the fluid heater needs to be a larger size. It is difficult to conduct heat to the portion of the fluid which flows in the central part of the fluid heating pipe unit 1, and consequently the heating rate is not raised.
Particularly in manufacturing semiconductor wafers, chemical solutions such as super-aqua-ammonia, sulfuric acid, hydrochloric acid and hydrofluoric acid are heated up to approximately 50.degree.-150.degree. C. in the fluid heater 500 for use in cleaning, etching and removing resist, but technologies in relation to corrosion resistance of the fluid heater 500 and a low degree of contam
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patent: 2589566 (1952-03-01), Neth et al.
patent: 4797535 (1989-01-01), Martin
patent: 5054107 (1991-10-01), Batchelder
patent: 5271086 (1993-12-01), Kamiyama
Kadotani Kan-ichi
Kubota Kazuhiko
Ohaku Mitsuru
Jeffery John A.
Kabushiki Kaisha Komatsu Seisakusho
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