Electric heating – Heating devices – Combined with container – enclosure – or support for material...
Reexamination Certificate
2003-09-04
2004-11-09
Pelham, Joseph M (Department: 3742)
Electric heating
Heating devices
Combined with container, enclosure, or support for material...
C219S390000, C362S308000
Reexamination Certificate
active
06815645
ABSTRACT:
TECHNICAL FIELD
This invention relates to a heat ray reflecting material capable of efficiently reflecting heat ray radiated from an exothermic body, and a heating apparatus using the same.
BACKGROUND ART
Manufacturing process for semiconductor wafers and device fabrication process using the semiconductor wafers include processes in which the semiconductor wafers are heated to several-hundred to thousand-and-several-hundred degree centigrade, and for which a various types of annealing furnaces such as those based on resistance heating system (heater heating system), lamp heating system and so forth are used depending on purposes.
For example, in order to manufacture a silicon single crystal wafer, which is a representative semiconductor wafer, a silicon single crystal ingot is pulled using a single crystal pulling apparatus. In the pulling of the single crystal ingot, a quartz crucible in which polysilicon is charged is surrounded by a heater, and the crucible is heated to a temperature as high as 1,420° C. so as to fuse the polysilicon as a source material. After the silicon single crystal thus produced is processed to obtain the wafers, removal of damage, diffusion of impurities, vapor phase growth of semiconductor films and so forth are also carried out under heated atmosphere, where a variety of heating apparatuses are used therefor. Also in the field of compound semiconductor, heating apparatuses are used for vapor phase growth or liquid phase growth of semiconductor films, and other annealing processes.
In order to raise the heating efficiency, the annealing apparatuses used for the above-described annealing are generally configured so that heat insulating materials are disposed around the exothermic body such as the aforementioned heater or lamp so as to prevent heat from dissipating to the externals. In more simplified heating apparatuses, the heat insulating material may sometimes omitted for size reduction.
Disposition of the heat insulating material, however, not only increases the size of the heating apparatus but also needs a longer time additionally for heating of the heat insulating material because of a large heat capacity thereof, and still also for cooling after completion of the annealing. Disposition of a forced cooling apparatus based on water cooling, air cooling or the like further increases the size of the apparatus. Moreover, heat absorbed by the heat insulating material is of course less contributable to heating of the works, and this worsens the energy efficiency. It is a matter of course that the apparatus using no heat insulating material further suffers from more waste dissipation of the energy.
A subject of this invention is therefore to provide a heat ray reflecting material capable of reflecting heat ray emitted from an exothermic body in an extremely efficient manner, and a heating apparatus capable of efficiently raising or lowering the temperature by concentrating heat ray emitted from an exothermic body towards the works by using the heat ray reflecting material.
DISCLOSURE OF THE INVENTION
To solve the aforementioned subject, a heat ray reflecting material of the invention is such as being capable of reflecting heat ray in a specific wavelength band, being a stack of a plurality of element reflecting layers comprising materials having transparent properties to the heat ray, wherein, in the element reflecting layers, two adjacent layers are composed of a combination of materials differed from each other in refractive indices to the heat ray, while keeping difference between the refractive indices of 1.1 or larger.
The heat ray reflecting material of the invention is configured based on a combination of the element reflecting layers respectively having transparent properties to the heat ray, differed from each other in refractive indices to the heat ray, and keeping difference between the refractive indices of 1.1 or larger. By composing the heat ray reflecting material based on the combination of the element reflecting layers ensuring a large difference in the refractive indices therebetween, the heat ray can be reflected at an extremely high reflectivity. Because a high reflectivity can be achieved only by a limited range of increase in the number of stacking of the element reflecting layers, the heat ray reflecting material can be manufactured at low costs. Difference in the refractive indices less than 1.1 inevitably lowers the reflectivity, and increase in the number of cycles of the stacking intended for an improved reflectivity raises the costs. The difference in the refractive indices between the element reflecting layers to be combined is preferably kept at 1.2 or more, more preferably 1.5 or more, and still more preferably 2.0 or more.
While “having transparent properties” herein can be defined as a status that an object has a property of allowing electromagnetic wave such as light to pass therethrough, transparent property in this invention is preferably such as ensuring a transmissivity of the heat ray to be reflected of as large as 80% or more for the thickness to be adopted. The transmissivity less than 80% may increase the absorption ratio of the heat ray, and may prevent the heat ray reflecting material of the invention from fully exhibiting the effect of reflecting the heat ray. The transmissivity is preferably 90% or more, and more preferably 100%. A transmissivity of 100% herein means a transmissivity which can be considered as almost 100% within a range of measurement limit (e.g., within ±1% error) in general methods of measuring transmissivity.
Next, a heating apparatus according to a first aspect of this invention comprises a container having a work housing space formed therein; a heat source for heating a work in the work housing space; and a heat ray reflecting member having a heat reflecting surface thereof composed of the heat ray reflecting material of this invention, so as to allow the heat ray generated in the work housing space to reflect on the heat reflecting surface to thereby change the direction thereof towards the work.
A heating apparatus according to a second aspect of this invention comprises at least an annealing chamber for carrying out annealing; an exothermic body disposed outside the annealing chamber; and a heat ray reflecting member surrounding the exothermic body and the annealing chamber and having a heat reflecting surface thereof composed of the heat ray reflecting material of this invention.
By applying the heat ray reflecting member composed of the heat ray reflecting material of this invention to a heating apparatus, and by using the member as a substitute, for example, for a part of or entire portion of the heat insulating material, delay in the heating or cooling speed of the annealing apparatus ascribable to heat capacity of the heat insulating material can be improved, and this enables more rapid heating and cooling as compared with those for the conventional apparatus. It is also possible to expand a length of uniform heating as compared with that for the conventional annealing apparatus. It is still also possible to achieve down-sizing and energy-saving effects of the apparatus because energy of the heat ray from the exothermic body can efficiently be concentrated to the work.
The specific wavelength band of the heat ray selected from a range of 1 to 10 &mgr;m can cover wavelength ranges of heat ray necessary for heat processing in various applications, and can promise the effect of this invention. Although applicable fields of the heating apparatus of this invention are not specifically limited, one possible example is like the followings. In order to manufacture a silicon single crystal wafer which is a representative semiconductor wafer, first a silicon single crystal ingot is pulled using a single crystal pulling apparatus. In the pulling of the single crystal ingot, a quartz crucible in which polysilicon is charged is surrounded by a heater, and the crucible is heated to a temperature as high as 1,420° C. or above. The invention is applicable to this heating apparatus. I
Pelham Joseph M
Shin-Etsu Handotai & Co., Ltd.
Snider Ronald R.
Snider & Associates
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