Abstract:
Disclosed is an apparatus for exposing a wafer to light, the apparatus including a light source unit having a light source for emitting light, a first cooling unit for cooling the light source unit, the first cooling unit having a gas flowpassage for a gas passing through the light source unit, and a second cooling unit for cooling the gas, the second cooling unit having a first fluid flowpassage for a first fluid which is to be heat-exchanged with the gas in the gas flowpassage at a position downstream of the light source unit with respect to the flow of the gas.

Description:
FIELD OF THE INVENTION AND RELATED ART  
       [0001]     This invention relates to an exposure apparatus having a light source which is also a heat generation source.  
         [0002]     In semiconductor exposure apparatuses, precise temperature control is required to assure precise positioning. The temperature control can be carried out in various ways such as ventilating a heat source by using a gas, precise air-conditioning based on gas circulation, removing heat from the heat source by using a liquid, and precise temperature control of an object by using a liquid. Where the heat source is outside a clean area, as in the case of heat generation from a light source or an electricity rack, an outside air is introduced and the heat is exhausted by using a blower. For temperature stabilization of the space in the clean area, a gas such as air or nitrogen is circulated as a temperature adjusting medium. The circulated and returned gas is heat-exchanged by using cooling water, and it is cooled to a temperature that enables temperature control. The gas so sufficiently cooled is then heated to a particular temperature by means of an electric heater or any other re-heating system using exhaust heat, to reduce temperature fluctuation due to external disturbance. Thereafter, the gas is precisely temperature-adjusted by means of an electric heater or a Peltier device, for example, in accordance with the temperature required individually for each portion where the temperature is to be controlled, and the gas is blown thereto.  
         [0003]     Where a cooling function unit is provided separately as the apparatus structure is very bulky, cooling water may be used in the cooling function unit, and a secondary coolant being sufficiently cooled by means of a refrigerator or a compressor may be used. In that case, after the heat transportation, heat exchanging by using a heat exchanger may be carried out. Where heat exhausting or temperature control is to be made to a liquid, the procedure is approximately the same as in the case of a gas.  
         [0004]     In semiconductor exposure apparatuses that use an Hg lamp as a light source, a special cooling mechanism is required to avoid adverse influences of heat generated from the lamp upon the temperature control. To this end, an outside air may be introduced to perform forcible ventilation to thereby lower the temperature to and under a predetermined temperature (Japanese Laid-Open Patent Application, Publication No. 11-329951).  
         [0005]     However, Hg lamps currently used as a light source have a large power of more than 4 kW, and they produce a large heat. If heat exhausting is carried out, the exhaust gas temperature will be 60° C. or higher. Discharging such high-temperature exhaust gas into a clean room environment would be very undesirable since it burdens a heavy load in respect to the factory equipment.  
       SUMMARY OF THE INVENTION  
       [0006]     It is accordingly an object of the present invention to provide a unique technique for cooling a light source unit.  
         [0007]     It is another object of the present invention to provide a unique and improved exposure apparatus and/or an exposure method by which at least one of the inconveniences described above can be removed or reduced.  
         [0008]     In accordance with an aspect of the present invention, there is provided an apparatus for exposing a wafer to light, said apparatus comprising: a light source unit having a light source for emitting light; a first cooling unit for cooling said light source unit, said first cooling unit having a gas flowpassage for a gas passing through said light source unit; and a second cooling unit for cooling the gas, said second cooling unit having a first fluid flowpassage for a first fluid which is to be heat-exchanged with the gas in the gas flowpassage at a position downstream of said light source unit with respect to the flow of the gas.  
         [0009]     In accordance with another aspect of the present invention, there is provided a device manufacturing method, comprising the steps of: exposing a substrate to light by use of an apparatus as recited above; developing the exposed substrate; and processing the developed substrate to produce a device.  
         [0010]     These and other objects, features and advantages of the present invention will become more apparent upon a consideration of the following description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0011]      FIG. 1  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a first embodiment of the present invention.  
         [0012]      FIG. 2  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a second embodiment of the present invention.  
         [0013]      FIG. 3  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a third embodiment of the present invention.  
         [0014]      FIG. 4  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a fourth embodiment of the present invention.  
         [0015]      FIG. 5  is a flow chart for explaining general procedure of semiconductor device manufacture. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0016]     Preferred embodiments of the present invention will now be described with reference to the attached drawings.  
       First Embodiment  
       [0017]      FIG. 1  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a first embodiment of the present invention. Details of the heat treatment system of the semiconductor exposure apparatus according to the first embodiment of the present invention will be explained with reference to  FIG. 1 .  
         [0018]     Denoted in the drawing at  1  is an outside air to be introduced from the outside to the inside of the apparatus as a cooling air of about 20 to 25° C. Denoted at  2  is an air filter, and denoted at  3  and  4  are outside air introducing paths, respectively. The outside air introducing path  3  functions to introduce the outside air into a lamp box outer shell  7 , while the outside air introducing path  4  serves to introduce the outside air into a lamp box inner shell  6 . Denoted at  5  is an Hg lamp which is a light source of exposure light, and the temperature thereof becomes very high. The exposure light source  5  is normally kept turned on since it takes a long time until the light quantity is stabilized after it is turned on/off. Thus, a heat exhaust gas  8  has an approximately stabilized temperature. Denoted at  6  is the lamp box inner shell, the inside thereof being at a high temperature due to heat generation from the Hg lamp  5 . Denoted at  7  is the lamp box outer shell that defines a space between it and the inner shell  6 , for heat exhaust of relatively low temperature. The outside wall of the lamp box outer shell is thermally insulated by means of a heat insulating material  15 , to reduce influence of heat to the apparatus internal structure.  
         [0019]     The heat exhaust gas  8  passing through the inside of the lam box inner shell  6  and directed toward a heat exchanger  10  has a high temperature of about 50-80° C., and the gas can not be discharged outwardly as it is. To meet this, in the heat exchanger  10 , the gas is heat-exchanged by using ejected cooling water  25  of about 25-28° C., whereby a heat exhaust gas  11  having its temperature lowered to about 40° C. or lower is provided. On the other hand, a heat exhaust gas  9  passed through the space between the outside of the lamp box inner shell  6  and the inside of the lamp box outer shell  7  has a temperature of about 30-40° C., and thus the gas is discharged as it is to the outside of the apparatus by means of an exhaust fan  12 . Here, at the exhaust fan  12 , the heat exhaust gas  9  is mixed with the heat exhaust gas  11  passed through the heat exchanger  10 , whereby a heat exhaust gas  13  is provided. This heat exhaust gas  13  is discharged outwardly of the apparatus as a factory exhaust gas  14 . The temperature of this heat exhaust gas  13  is about 40° C. or lower which is a heat exhaust gas temperature appropriate to the factory exhaust gas. Ejected water  26  having been heat-exchanged at the heat exchanger  10  is discharged to the factory side as factory ejected water  27  of about 30-40° C.  
         [0020]     Regarding production of the ejected cooling water  25 , initially, factory cooling water  16  of about 16 to 28° C. is supplied along a cooling water path  17  and it is heat-exchanged at a temperature-controlling-medium cooling device  18 , whereby ejected cooling water  19  of about 32° C. is provided. On the other hand, the temperature controlling medium  29  having been temperature-exchanged and cooled at the cooling device  18  is supplied to a cooling-water-exhaust-heat-reusing heat exchanging temperature control unit  20 , where the temperature thereof is detected and controlled by using a temperature sensor  21 . Hence, a temperature controlling medium  30  having been coarsely heated and temperature-controlled is provided. This temperature controlling medium  30  is thereafter heated and temperature-controlled again at a precise temperature controlling unit  31 .  
         [0021]     Denoted at  34  is a filter, and denoted at  32  is a temperature sensor for precision temperature control. The temperature controlling medium  33  having been precisely temperature-controlled is introduced into a temperature controlling chamber  35 A as an injected temperature controlling medium, and it deprives a temperature control subject  35  of heat. Thereafter, it is collected as an ejected temperature controlling medium, whereby a temperature controlling medium  28  is produced. The temperature controlling medium may be a gas such as air or nitrogen, for example, or a liquid such as pure water, antifreeze liquid, or fleon (Freon) series insulative liquid (cooling oil), for example. For coarse heating of the temperature controlling medium at the cooling-water-exhaust-heat-reusing heat exchanging temperature control unit  20 , the ejected cooling water  19  of 32° C. may be used to perform the heat exchange while controlling a control valve  22  on the basis of a detected value of the temperature sensor  21 . The ejected cooling water  23  having been cooled by the heat exchange and the bypassed ejected cooling water  24  are combined into ejected cooling water  25  of about 25 to 28° C. which is then heat-exchanged at the heat exchanger  10  with the high-temperature heat exhaust gas  8  inside the lamp box.  
       Second Embodiment  
       [0022]      FIG. 2  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a second embodiment of the present invention. Details of the heat treatment system of the semiconductor exposure apparatus according to the second embodiment of the present invention will be explained with reference to  FIG. 2 .  
         [0023]     In accordance with the embodiment shown in  FIG. 2 , in addition to the first embodiment, there is a second coarse heating unit  37 . The second coarse heating unit  37  uses the ejected water having been heat-exchanged at the heat exchanger  10  to coarsely heat again a portion of the temperature controlling medium  30 , having been coarsely heated and temperature-controlled. As a result of this, a temperature controlling medium  39  having been coarsely reheated and having a temperature higher than the temperature controlling medium  30  is produced.  
         [0024]     Subsequently, the temperature controlling media  30  and  39  are precisely temperature-controlled at precision temperature control units  31   b  and  31   a , respectively and individually, and then they are used to temperature-control the subjects  35   b  and  35   a  of temperature control, respectively and individually. After this, the temperature controlling media are collected by means of a circulation fan  36  (if air is used) or a circulation pump  36  (if liquid is used), whereby collected temperature controlling medium  28  is provided. The factory ejected water  27  is discharged outwardly through an ejected water path  38 .  
       Third Embodiment  
       [0025]      FIG. 3  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a third embodiment of the present invention. Details of the heat treatment system of the semiconductor exposure apparatus according to the third embodiment of the present invention will be explained with reference to  FIG. 3 .  
         [0026]     In the third embodiment shown in  FIG. 3 , the temperature controlling medium  39  coarsely reheated in the structure of the second embodiment and the branched temperature controlling medium  30  are mixed with each other by means of the provision of a bypass  40 . The mixture of the temperature controlling medium  39  and the temperature controlling-medium  30  provides a temperature controlling medium  41 . Here, the temperature of the temperature controlling medium  41  is measured by use of a temperature sensor  42 , so that the degree of opening of a two-way control valve (or three-way control valve)  43  is adjusted in accordance with the state of heat generation at the temperature-control subject  35  to perform coarse temperature adjustment.  
         [0027]     Subsequently, the coarsely temperature-controlled temperature controlling medium  41  is supplied to a precision temperature control unit  31 , where most appropriate temperature control is carried out to the temperature controlling medium  41  in accordance with the measurement by the temperature sensor  32  and the state of heat generation at the temperature control subject  35 . Then, the temperature controlling medium is used to control the temperature of the temperature control subject  35 .  
       Fourth Embodiment  
       [0028]      FIG. 4  is a schematic and diagrammatic view of a general structure of a heat treatment system in a semiconductor exposure apparatus according to a fourth embodiment of the present invention. Details of the heat treatment system of the semiconductor exposure apparatus according to the fourth embodiment of the present invention will be explained with reference to  FIG. 4 .  
         [0029]     In the fourth embodiment shown in  FIG. 4 , before it is heat-exchanged at the heat exchanger  10 , the high-temperature heat exhaust gas  8  inside the lamp box is heat-exchanged at a heat exchanger  44  by a coarsely-heated temperature controlling medium  30  whereby a high-temperature exhaust gas  45  is provided. At the cooling-water-exhaust-heat-reusing heat exchanging temperature control unit  20 , the temperature of the temperature controlling medium  39  having been reheated by the heat exchanger  44  is measured by use of a temperature sensor  21 . By adjusting the degree of opening of a two-way control valve (or three-way control valve)  22  on the basis of the temperature measurement, coarse-heating temperature control is performed so that the temperature of the temperature controlling medium  30  is held constant.  
       Fifth Embodiment  
       [0030]     Next, as a fifth embodiment, an embodiment of a semiconductor device manufacturing method which uses an exposure apparatus having a heat treatment system according to any one of the first to fourth embodiments described above, will be explained.  
         [0031]      FIG. 5  is a flow chart for explaining the overall procedure for semiconductor manufacture. Step  1  is a design process for designing a circuit of a semiconductor device. Step  2  is a process for making a mask on the basis of the circuit pattern design. Step  3  is a process for preparing a wafer by using a material such as silicon. Step  4  is a wafer process which is called a pre-process wherein, by using the thus prepared mask and wafer, a circuit is formed on the wafer in practice, in accordance with lithography. Step  5  subsequent to this is an assembling step which is called a post-process wherein the wafer having been processed at step  4  is formed into semiconductor chips. This step includes an assembling (dicing and bonding) process and a packaging (chip sealing) process. Step  6  is an inspection step wherein an operation check, a durability check an so on, for the semiconductor devices produced by step  5 , are carried out. With these processes, semiconductor devices are produced, and they are shipped (step  7 ).  
         [0032]     More specifically, the wafer process at step  4  described above includes; (i) an oxidation process for oxidizing the surface of a wafer; (ii) a CVD process for forming an insulating film on the wafer surface; (iii) an electrode forming process for forming electrodes upon the wafer by vapor deposition; (iv) an ion implanting process for implanting ions to the wafer; (v) a resist process for applying a resist (photosensitive material) to the wafer; (vi) an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above; (vii) a developing process for developing the exposed wafer; (viii) an etching process for removing portions other than the developed resist image; and (ix) a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer.  
         [0033]     In accordance with the embodiments of the present invention as described hereinbefore, the temperature of the high-temperature exhaust gas is lowered and the exhaust beat is released to the cooling water. As a result of it, the exhaust gas temperature becomes close to the normal temperature. This makes the burden to factory equipment smaller, and it reduces the influence on the clean room temperature.  
         [0034]     Furthermore, in the embodiments described above, the coarse heating function for performing precise temperature control is provided by use of heat generation of the exposure light source and without use of heating means such as a heater. The electricity power consumption of the apparatus can be smaller to save the energy.  
         [0035]     Moreover, in the embodiments described hereinbefore, in addition to the advantageous features mentioned above, through the precision improvement of coarse heating temperature control, the cost of the apparatus can be reduced significantly.  
         [0036]     While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.  
         [0037]     This application claims priority from Japanese Patent Application No. 2004-277496 filed Sep. 24, 2004, for which is hereby incorporated by reference.