JP5049461B2 - Heat treatment equipment - Google Patents

Description

  The present invention relates to a heat treatment apparatus in which a thermoelectric conversion element is arranged inside a housing.

  In the rapid thermal processing equipment (RTP: Rapid Thermal Processer) used when heat-treating semiconductor wafers in the semiconductor manufacturing process, halogen lamps are placed above and below the housing, and process tubes are placed between these halogen lamps. (For example, refer to Patent Document 1). In this high-speed heat treatment apparatus, a semiconductor wafer as an object to be processed is housed in a transparent quartz glass process tube, and heat treatment is performed by heating by radiating heat from a halogen lamp. Further, the upper wall and the lower wall of the housing are made of a highly heat conductive material, and are configured by a reflector plate having a mirror-like radiant heat reflecting surface formed on the inner surface. And these reflectors are formed with a cold water passage inside to perform water cooling. Therefore, this rapid thermal processing apparatus prevents the heat radiated from the halogen lamp from being reflected by the radiant heat reflecting surface of the reflector plate and leaking outside when the halogen lamp is heated and soaked. The semiconductor wafer can be heated quickly by efficiently heating. Further, when the temperature is lowered when the halogen lamp is turned off, the reflecting plate made of the high thermal conductivity material is cooled by the water cooling method, so that the semiconductor wafer can be quickly cooled by efficiently dissipating heat.

  However, the high-speed heat treatment apparatus has a problem that energy loss becomes excessive because the process of temperature increase and decrease is repeated at high speed.

  In a general heating furnace, in order to suppress the same energy loss as described above, a thermoelectric conversion module is arranged on the furnace wall, and the heat released through the furnace wall is converted into electric power to recover the energy. There was a case to do.

However, in such a heating furnace, the thermoelectric conversion module is arranged outside the furnace wall made of a heat insulating material (see, for example, Patent Document 2). There was a problem that sufficient energy could not be recovered by the thermoelectric conversion module. In addition, the thermoelectric conversion module cannot be expected to have a sufficient heat insulation effect, and if the thermoelectric conversion efficiency becomes higher due to future improvements, the cooling effect becomes rather high. When the thermoelectric conversion module is placed via the thermoelectric conversion module, energy is recovered by the thermoelectric conversion module even during temperature rise and soaking, and heating and cooling are performed at the same time. There arises a problem of wasting energy by the loss due to efficiency. That is, since the thermoelectric conversion module attempts to recover energy without distinction between temperature rising / soaking and temperature falling, there arises a problem that sufficient energy cannot be recovered or energy is wasted. Such a problem also applies to a heating furnace in which a thermoelectric conversion module is embedded in a part of the outer layer of the furnace wall (see, for example, Patent Document 3).
Japanese Patent Publication No. 6-40027 JP 2002-171776 A Japanese Patent Laid-Open No. 10-190073

  In the present invention, the low temperature side surface of the thermoelectric conversion element is brought into close contact with the inner side surface of the housing provided with the cooling means, and the radiation heat reflecting film is formed on the high temperature side surface of the thermoelectric conversion element, so that the temperature rises from the temperature rise. Thus, it is an object of the present invention to provide a heat treatment apparatus capable of sufficiently maintaining the heat inside the housing and recovering energy efficiently.

According to the first aspect of the present invention, there is provided a heat treatment apparatus in which a heating means for heating mainly by radiant heat irradiation and a process tube for storing an object to be processed are disposed inside a housing having a cooling means . Power is output based on the temperature difference between the high temperature side surface and the low temperature side surface, with part or all of the inner surface side having one surface as the high temperature side surface and the opposite surface to the low temperature side surface. Is disposed so as to cover the inner surface of the housing with the low-temperature surface facing the inner surface of the housing, and faces the inside of the thermoelectric conversion element. A radiant heat reflective film (5) is formed on the surface.

The invention of claim 2 is characterized in that the thermoelectric conversion elements are stacked from the inner side surface of the housing toward the inside of the housing to form a plurality of layers .
According to a third aspect of the present invention, the thermoelectric conversion element comprises the plurality of layers by combining a plurality of modules having a thermoelectric conversion function, and the plurality of modules have the same thermoelectric conversion characteristics. It is characterized by that.
According to a fourth aspect of the present invention, the thermoelectric conversion element forms the plurality of layers by combining a plurality of modules having a thermoelectric conversion function, and the plurality of modules are good thermoelectric conversion at least at a low temperature. A low-temperature characteristic element having characteristics and a high-temperature characteristic element having favorable thermoelectric conversion characteristics at a high temperature, wherein the low-temperature characteristic element is more in the housing than the high-temperature characteristic element in the plurality of layers. It is arrange | positioned in the layer nearer to the inner surface of.

  According to the first aspect of the present invention, the inside of the furnace is heated by the radiant heat from the heating means at the time of temperature rise and soaking, but the surface on the high temperature side that becomes the inner surface of the thermoelectric conversion element disposed on the inner surface of the housing The radiant heat is reflected by the radiant heat reflection film, so that the inside of the furnace is kept warm enough to prevent the heating efficiency from becoming too low, and the temperature difference from the low temperature side surface in close contact with the cooling surface of the housing Thus, the heat energy flowing from the high temperature side surface can be efficiently recovered. In addition, since the low temperature side of the thermoelectric conversion element is maintained at a low temperature by being cooled by the cooling means, if the heat in the housing is transferred to the high temperature side of the thermoelectric conversion element by heat conduction when the temperature is lowered, the thermoelectric conversion is efficiently performed. Thus, not only can heat energy be converted into electric power and recovered, but also the temperature in the housing can be quickly lowered. Such energy recovery is also performed at the time of temperature rise and soaking, but the heating means that the ratio of heat lost by heat conduction decreases as the heating means with a higher ratio by radiant heat reduces the heating efficiency. Things will also be less. In addition, when the temperature drops, this heating means stops heating, and the radiant heat is only due to residual heat, so even if a radiant heat reflecting film is formed on the inner surface of the thermoelectric conversion element, the heat dissipation efficiency is particularly greatly reduced. There is nothing to do.

  Hereinafter, the best embodiment of the present invention will be described with reference to FIGS.

  In the present embodiment, a rapid heat treatment apparatus used when heat treating a semiconductor wafer in a semiconductor manufacturing process will be described. As shown in FIG. 1, this rapid thermal processing apparatus includes a halogen lamp 2 disposed above and below a housing 1 and a process tube 3 disposed between the upper and lower halogen lamps 2. The process tube 3 is a transparent quartz glass tube, and the end on the left side in the figure is opened and the end on the right side in the figure is closed so that only the intake port 3a and the exhaust port 3b communicate with each other. It has become. The process tube 3 accommodates the semiconductor wafer W inside, and the inside of the process tube 3 can be hermetically sealed by closing the opening end on the left side of the housing 1 with the opening / closing lid 1a. Further, by replacing the gas through the intake port 3a and the exhaust port 3b, an arbitrary processing gas can be filled into the process tube 3, and the pressure inside the process tube 3 can also be adjusted.

  The halogen lamp 2 is a straight tube incandescent lamp in which halogen gas is sealed. A plurality of halogen lamps 2 are arranged vertically and horizontally above and below the process tube 3 in the housing 1. Therefore, when these halogen lamps 2 are turned on, radiant heat passes through the process tube 3 and is irradiated to the semiconductor wafer W from above and below to be heated.

  The housing 1 surrounds the process tube 3 and the halogen lamp 2 so as to be sealed inside, and supports the process tube 3 and the halogen lamp 2. The upper wall and the lower wall have cooling jackets 1b, 1b is arranged. The cooling jacket 1b is made of a thick metal plate having high thermal conductivity, and a chilled water passage 1c is formed therein as shown in FIG. 2 (the chilled water passage 1c is not shown in FIG. 1). In the cold water passage 1c, cooling water is always sent and circulated from an external water cooling device (not shown), so that the cooling jacket 1b is cooled by water cooling, and the inner surface (the cooling jacket 1b on the upper wall is the lower surface, The cooling jacket 1b on the lower wall is the cooling surface.

In the heat treatment apparatus of the present invention, a process tube 3 is disposed in a space formed by a housing 1, upper and lower cooling jackets (1b, 1b), and an opening / closing lid 1a, and a thermoelectric conversion module is disposed inside the jacket (1b, 1b). 4, 4... Are arranged, and a radiant heat reflecting film 5 is formed on the inner wall of these electrothermal conversion modules (FIGS. 1 and 2).

The inner surface of the upper and lower cooling jackets 1b of the housing 1 is in close contact with the low temperature side surfaces of a large number of thermoelectric conversion modules 4 (hereinafter, thermoelectric conversion elements are referred to as thermoelectric conversion modules (elements) 4) . The thermoelectric conversion module 4 is a tile plate-shaped thermoelectric conversion element, and since one surface having a large area is a low temperature side surface and the other surface is a high temperature side surface, the inside of the housing 1 has this high temperature side surface. Will be exposed. A radiant heat reflecting film 5 is formed on the high temperature side surface of these thermoelectric conversion modules 4. The radiant heat reflective film 5 is a film having an extremely high radiant heat reflectivity with an inner surface as a mirror surface. Such a radiant heat reflective film 5 can be formed by evaporating, for example, a metal layer (Au or the like) on the high temperature side surface of the thermoelectric conversion module 4. Radiant heat is electromagnetic waves in the infrared (including far-infrared) region and in the peripheral wavelength region including visible light. When this radiant heat is absorbed by a substance, it generates heat. However, since the radiant heat reflecting film 5 reflects most of the radiant heat, the heat due to the radiant heat is hardly transmitted to the high temperature side surface of the thermoelectric conversion module 4. However, the heat inside the housing 1 is transmitted to the high-temperature side surface of the thermoelectric conversion module 4 through the radiant heat reflection film 5 by heat conduction by contacting the high-temperature gas that is convected. A base layer having high thermal conductivity is formed between the inner surface of the cooling jacket 1b and the thermoelectric conversion module 4 or between the high temperature side surface of the thermoelectric conversion module 4 and the radiant heat reflection film 5. The base layer can buffer the stress caused by the difference in thermal expansion.

  The thermoelectric conversion module 4 is a thermoelectric conversion element that generates electric power by thermoelectrically converting thermal energy due to a temperature difference between them into electrical energy by raising the temperature on the high temperature side rather than the low temperature side. And the some thermoelectric conversion module 4 closely_contact | adhered to the inner surface of each cooling jacket 1b is appropriately connected in series or in parallel, and outputs the thermoelectrically converted electric power to the outside. As shown in FIG. 3, the thermoelectric conversion module 4 of the present embodiment has a large number of p-type semiconductors and n-type semiconductors arranged alternately, and ceramic plates 42 and 42 from both the high temperature side and the low temperature side. Is sandwiched between. The thermoelectric conversion material 41 is a material that performs thermoelectric conversion by the Seebeck effect based on the temperature difference between both ends. Here, the thermoelectric conversion material 41 is a p-type semiconductor having a positive thermoelectromotive force and an n-type semiconductor having a negative thermoelectromotive force. By combining these, high electromotive force can be obtained efficiently. The ceramic plate 42 is an insulating substrate and has a relatively good thermal conductivity. In these ceramic plates 42 and 42, conductive patterns 43 and 43 are formed on the inner surface of the ceramic plates 42 and 42 in contact with the thermoelectric conversion material 41, respectively, and these conductive patterns 43 and 43 form a thermoelectric conversion composed of a p-type semiconductor and an n-type semiconductor. The material 41 is connected in series. Therefore, even if the output voltage (electromotive force) of each thermoelectric conversion material 41 is very small, the output voltage of the thermoelectric conversion module 4 as a whole has a practical magnitude obtained by adding the output voltages of these thermoelectric conversion materials 41. be able to.

  In addition, although the case where all the thermoelectric conversion materials 41 are connected in series is shown in the thermoelectric conversion module 4, a plurality of thermoelectric conversion materials 41 are connected in series, and these series connection sets are further connected in parallel. You can also The reason why the ceramic plates 42 and 42 having relatively poor thermal conductivity are used in the thermoelectric conversion module 4 is to insulate the conductive patterns 43 and 43 that connect a large number of thermoelectric conversion materials 41. In place of the plates 42, 42, other insulating materials having better thermal conductivity can be used. For example, if the material is extremely thin such as an oxide film, a material having a somewhat poor thermal conductivity is used. You can also. Further, the thermoelectric conversion module 4 may be housed in, for example, a metal package having good thermal conductivity so that the inside is sealed.

The thermoelectric conversion module 4 may be composed of only a single module, but as shown in FIG. 4, a plurality of modules 4 a stacked from the high temperature side to the low temperature side can also be used. That is, in FIG. 4, configured by the module 4a of the n layer thermoelectric conversion module 4 is composed of the first layer L ₁ ~ n-th layer L _n. Further, an interlayer insulation / stress relaxation layer 4b is interposed between the modules 4a of each layer. The connection between the plurality of stacked modules 4a is arbitrary regardless of whether they are connected in series or parallel.

The modules 4a of the respective layers can be stacked using the same thermoelectric conversion material. For example, it is assumed that a certain module 4a has thermoelectric conversion characteristics as shown in FIG. Here, the temperature T _H is the highest temperature on the high temperature side of the entire thermoelectric conversion module 4, the temperature T _C is the lowest temperature on the low temperature side, and the temperature T _M is an intermediate temperature between them. The figure of merit Z (T) indicates the high thermoelectric conversion performance at the temperature T. Therefore, this module 4a exhibits the maximum figure of merit near the temperature T _M , and the figure of merit decreases at both the higher temperature T _H and the lower temperature T _C. When the thermoelectric conversion module 4 is configured with such a module 4a alone, as shown in Equation 1,
Electric power proportional to the area of the trapezoid indicated by the hatching rising to the right in FIG. 5 can be output. On the other hand, when the thermoelectric conversion module 4 is configured by arranging two identical modules 4a in the first layer and the second layer, as shown in Equation 2,
It is possible to output power proportional to the area of the two trapezoids indicated by the left-upward hatching in FIG. Therefore, even if the same module 4a is used, it is possible to increase the thermoelectric conversion efficiency by configuring the thermoelectric conversion module 4 by stacking a plurality of modules in accordance with the performance index characteristics.

Moreover, the module 4a of each said layer can also be comprised combining what used a different thermoelectric conversion material. For example, it is assumed that two types of modules 4a have thermoelectric conversion characteristics as shown in FIG. That is, one module 4a is for low-temperature characteristics showing a high performance index between the temperature T _C and the temperature T _M , and the other module 4a is a high performance index between the temperature T _M and the temperature T _H. For high temperature characteristics. Moreover, the thermoelectric conversion efficiency between the temperature T _C and the temperature T _H becomes extremely poor with only one of these modules 4a. If the thermoelectric conversion module 4 is configured by arranging the module 4a for high temperature characteristics in the first layer and the module 4a for low temperature characteristics in the second layer, the temperature T _C on the low temperature side and the high temperature side not only it is possible to widen the temperature range for the temperature T _H, by utilizing the best thermoelectric conversion material in the temperature range of each layer respectively, it will also be able to further increase the thermoelectric conversion efficiency.

Table 1 exemplifies thermoelectric conversion materials that can be used for the module 4a.
Among these thermoelectric conversion materials, those based on oxides are stable even in high-temperature air, and have the advantage that the inside of the module 4a does not need to be airtight.

  According to the rapid thermal processing apparatus having the above configuration, the semiconductor wafer W is heated by the radiant heat from the lit halogen lamp 2 at the time of temperature rise and soaking, but the radiant heat reflection film 5 on the high temperature side surface of the thermoelectric conversion module 4. Since this radiant heat is reflected, the inside of the housing 1 is also kept warm enough to prevent the heating efficiency from becoming too low. Moreover, this rapid thermal processing apparatus uses a cooling jacket 1b for the housing 1 compared to the case where the housing 1 is a furnace wall made of a heat insulating material. Since the heat leaked to the outside is converted into electric power by the thermoelectric conversion module 4 and recovered, there is no particular waste of heat energy.

  In addition, since the heat in the housing 1 is efficiently conducted to the high temperature side surface of the thermoelectric conversion module 4 when the temperature is lowered, the thermoelectric conversion module 4 effectively converts thermal energy into electric power. Can be recovered. Moreover, since the halogen lamp 2 is turned off when the temperature is lowered, the radiant heat reflection film 5 on the high temperature side surface of the thermoelectric conversion module 4 does not hinder the temperature drop in the housing 1. That is, the halogen lamp 2 is completely turned off except in the case of a gradual temperature lowering process or the like, so that it hardly emits radiant heat, and the process tube 3, the semiconductor wafer W, the processing gas, etc. Although radiant heat is emitted, it is little compared with the radiant heat emitted when the halogen lamp 2 is turned on. Therefore, even if these radiant heats are interrupted by the radiant heat reflecting film 5, the heat radiation efficiency is not particularly lowered. Rather, the housing 1 is much quicker than when the housing 1 is made of a furnace wall made of a heat insulating material. It becomes possible to perform heat dissipation.

  In the above embodiment, the thermoelectric conversion module 4 including a single module or the thermoelectric conversion module 4 in which a plurality of modules 4a are stacked is used as the thermoelectric conversion element. However, an element that performs thermoelectric conversion by the Seebeck effect is shown. Any configuration may be used as long as it is.

  In the above embodiment, the cooling jackets 1b and 1b are arranged only on the upper wall and the lower wall of the housing 1. However, the arrangement of the cooling jacket 1b is arbitrary, and the entire housing 1 is formed by the cooling jacket 1b. It is also possible to configure. Furthermore, the thermoelectric conversion element may be disposed on the entire inner surface of the cooling jacket 1b or may be disposed only in a partial region. Furthermore, if the cooling jacket 1b is disposed in a part of the housing 1, the adjacent wall portion and the like are also cooled. Therefore, the thermoelectric conversion element may be disposed in close contact with the inner side surface. Furthermore, in the above embodiment, the cooling means of the cooling jacket 1b is water-cooled, but the type of the refrigerant is arbitrary, and can be air-cooled by providing cooling fins on the outside. It can also be done.

  Moreover, although the case where the inside of the process tube 3 was heated with the halogen lamp 2 was shown in the said embodiment, another infrared lamp etc. can also be used. Furthermore, since any heating means that mainly heats by radiant heat may be used, a heat plate in which a heater is embedded in a metal plate, a ceramic heater that generates heat from the plate material itself, a conductive plate that is heated by electromagnetic induction heating, etc. There may be, and the kind of this heating means is arbitrary. Further, the heating means is not limited to heating the internal semiconductor wafer W from the outside of the process tube 3, and may be one that performs heating inside the process tube 3. Furthermore, for example, the process tube itself can be made of glassy carbon, and the process tube itself can be used as a heating means by heating by electromagnetic induction heating from the outside.

  In the above-described embodiment, the rapid thermal processing apparatus that performs thermal processing on the semiconductor wafer W has been described. However, the workpiece is not limited to the semiconductor wafer W. Furthermore, in the above-described embodiment, the rapid thermal processing apparatus has been described. However, any thermal processing apparatus may be used as long as the heating unit and the process tube are arranged inside the housing having the cooling unit.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional side view showing a structure of a rapid thermal processing apparatus according to an embodiment of the present invention. 1 shows an embodiment of the present invention, and shows the structure of a furnace wall of a rapid thermal processing apparatus, and is a partially enlarged longitudinal sectional side view of part A in FIG. 1. 1 shows an embodiment of the present invention and is a longitudinal sectional side view showing a structure of a thermoelectric conversion module. FIG. 1 shows an embodiment of the present invention, and is a longitudinal sectional side view showing a configuration when a thermoelectric conversion module has a multilayer structure. FIG. It is one which shows one Embodiment of this invention, Comprising: It is a graph which shows the thermoelectric conversion characteristic of a thermoelectric conversion module. 1 is a graph showing one embodiment of the present invention and showing thermoelectric conversion characteristics of thermoelectric conversion modules for low temperature characteristics and high temperature characteristics.

DESCRIPTION OF SYMBOLS 1 Housing 1b Cooling jacket 2 Halogen lamp 3 Process tube 4 Thermoelectric conversion module 4a Module 5 Radiation heat reflective film

Claims (4)

In a heat treatment apparatus in which a heating means for heating mainly by irradiation of radiant heat and a process tube for storing an object to be processed are arranged inside a housing provided with a cooling means.
A part or all of the inner surface side of the housing has one surface as a high temperature side surface and the opposite surface of the one surface as a low temperature side surface, based on a temperature difference between the high temperature side surface and the low temperature side surface. The thermoelectric conversion element for collecting the output electric power is arranged so as to cover the inner side surface of the housing with the low temperature side surface facing the inner side surface of the housing,
A heat treatment apparatus , wherein a radiant heat reflection film (5) is formed on a surface of the thermoelectric conversion element facing the inside of the housing . 2. The heat treatment apparatus according to claim 1 , wherein the thermoelectric conversion element forms a plurality of layers by being laminated from an inner side surface of the housing toward an inside of the housing . The thermoelectric conversion element constitutes the plurality of layers by combining a plurality of modules having a thermoelectric conversion function,
  The heat treatment apparatus according to claim 2, wherein each of the plurality of modules has the same thermoelectric conversion characteristics.   The thermoelectric conversion element constitutes the plurality of layers by combining a plurality of modules having a thermoelectric conversion function,
  The plurality of modules include at least a low-temperature characteristic element having a good thermoelectric conversion characteristic at a low temperature and a high-temperature characteristic element having a good thermoelectric conversion characteristic at a high temperature. The heat treatment apparatus according to claim 2, wherein the heat treatment apparatus is disposed in a layer closer to an inner surface of the housing than the element for high temperature characteristics.