Abstract:
An apparatus for forming a coating film comprising, a coating unit for forming a coating film by applying a coating solution onto a substrate, and a curing unit for curing the coating film by applying a heating and a cooling to the substrate, in which, the curing unit comprises a heating chamber having a hot plate for heating substrates having the coating solution applied thereon one by one, a cooling chamber communicated with the heating chamber and having a cooling plate for cooling the substrates processed with heat, an inert gas supply mechanism for supplying an insert gas to the heating chamber and the cooling chamber, and an evacuation mechanism for evacuating each of the heating chamber and the cooling chamber.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to an apparatus for forming a coating film (coating film formation apparatus) by coating a solution for an interlayer dielectric film on a substrate in a manufacturing process of a semiconductor device, and an apparatus for curing the coating film for the interlayer dielectric film on the substrate. 
     The manufacturing process for a semiconductor device includes a step of forming an interlayer dielectric film (hereinafter referred to as “ILD”) in accordance with a Spin on Dielectric (hereinafter referred to as “SOD”) system. The interlayer dielectric film formation methods in accordance with the SOD system include a Sol-Gel method, a SiLK method, SPEED FILM method, and a FOx method. In each of these methods, a solution for forming the interlayer dielectric film is spin-coated on a substrate. The film thus coated is cured by annealing in the SiLK method, SPEED FILM method, and FOx method except the Sol-Gel method. 
     In such an annealing process, a plurality of wafers having a coating film thereon are loaded into a heating furnace in lots. After heating at a high temperature for a predetermined time, the wafers are unloaded from the heating furnace in lots, transferred to a cooling unit by way of a transfer passage, and cooled to a predetermined temperature. 
     However, the annealing (thermosetting) is performed in a batch since the wafers of a single lot are heated in a furnace of a high temperature. Therefore, it is impossible to accurately control temperature of the wafers one by one. 
     In addition, although the annealing treatment is performed in an inert gas ambient, it is difficult to control the concentration of the inert gas when the semiconductor wafer is transferred to a cooling unit after the heating process. In other words, it is difficult to maintain a low oxygen concentration. As a result, the interlayer dielectric film may be oxidized. For these reasons, it has been strongly desired that the wafers are annealed one by one by a single-wafer processing method using a hot plate while preventing oxidation of the interlayer dielectric film. 
     However, since the interlayer dielectric film is annealed at a high temperature, a temperature sensor used in a hot plate of a conventional apparatus and an inter-lock sensor for preventing an excessive temperature increase cannot be used. Therefore, if the annealing is performed by the hot plate, it is difficult to control temperature. In addition, even if only the annealing is performed by a single wafer processing method, it is impossible to overcome an oxidation problem of the interlayer dielectric film. 
     BRIEF SUMMARY OF THE INVENTION 
     An object of the present invention is to provide an apparatus for forming a coating film and an apparatus for curing the coating film capable of controlling substrates one by one when the substrates having a coating film thereon are cured while preventing oxidation of the coating film efficiently. 
     According to the present invention, there is provided an apparatus for forming a coating film comprising; 
     a coating unit for forming a coating film by applying a coating solution onto a substrate; and 
     a curing unit for curing the coating film by applying a heating and a cooling to the substrate. 
     The curing unit comprises 
     a heating chamber having a hot plate for heating substrates having the coating solution applied thereon, one by one; 
     a cooling chamber communicated with the heating chamber and having a cooling plate for cooling the substrates processed with heat; 
     an inert gas supply mechanism for supplying an insert gas to the heating chamber and the cooling chamber; and 
     an evacuation mechanism for evacuating the heating chamber and the cooling chamber. 
     It is preferable that the apparatus further comprise, a power source for supplying a power to the hot plate; a first and second temperature sensors for detecting temperature of the hot plate; setting means for setting a first specified temperature which is an upper limit of a temperature range suitable for curing the coating solution and for setting a second specified temperature which is higher than the first specified temperature, a controller and a temperature controller for controlling the power supply such that when temperature detected by the first temperature sensor exceeds the first specified temperature, power supply to the hot plate is terminated, and when the temperature detected is lower than the first specified temperature, power supply to the hot plate is initiated; and an excessive temperature increase detector for terminating power supply to the hot plate when temperature detected by the second temperature sensor exceeds the second specified temperature and maintaining an OFF state of power supply. 
     In this case, it is desirable that the apparatus further comprise, a relay connected to each of the temperature controller, controller, excessive temperature increase detector and hot plate, for opening and closing a power supply circuit from the power source to the hot plate, that the controller output an opening signal to the relay when power supply to the hot plate is terminated, and that the excessive temperature increase detector output an opening signal to the relay when power supply to the hot plate is terminated. 
     According to the present invention, there is provided an apparatus for curing a coating film comprising; 
     a heating chamber having a hot plate for heating substrates coated with a coating solution, one by one; 
     a cooling chamber communicating with the heating chamber, for cooling the substrate processed with heat; 
     an inert gas supply mechanism for supplying an inert gas to the heating chamber and the cooling chamber; and 
     an evacuation mechanism for evacuating the heating chamber and the cooling chamber; 
     According to the present invention, since an inert gas is supplied to each of the heating chamber and cooling chamber, the heating and cooling can be performed continuously under an atmosphere low in oxygen concentration and the coating film can be sufficiently prevented from being oxidized. 
     Furthermore, the temperature of the hot plate is detected by using two different temperature sensors and the temperature of the hot plate is controlled on the basis of these detection temperatures. Even if the temperature of the hot plate increases to a high temperature region which a conventionally-employed apparatus cannot control, a thermocouple can control it. In addition, power supply to the hot plate is mechanically terminated by the excessive temperature increase detector. Therefore, it is possible to prevent an excessive increase in temperature of the hot plate. Note that a thermocouple and a platinum resistance temperature sensor may be preferably used as the temperature sensor. 
     A shutter is provided for blocking the heating chamber and the cooling chamber in the curing unit. Therefore, it is possible to prevent thermal interference between these chambers. 
     Furthermore, it is preferable that the heating chamber have a ring shutter surrounding an outer periphery of the substrate placed on the hot plate during heating and a lifting mechanism for moving the ring shutter upward and downward. With this constitution, uniformity in temperature of the substrate over the entire surface can be further improved. 
     In the apparatus for forming a coating film according to the present invention, the curing unit for curing a coating film has a heating chamber for heating a substrate and a cooling chamber for cooling a substrate processed with heat, are provided so as to communicate with each other. In addition, an inert gas is supplied to each of the heating chamber and the cooling chamber. Therefore, the heating and the cooling can be continuously performed under an atmosphere low in oxygen concentration and the coating film is fully prevented from being oxidized. 
     According to the present invention, wafers are processed one by one in a heating chamber. It is therefore possible to accurately control the wafers one by one. In addition, heat can be kept applying uniformly to the entire surface of the wafer in the hating process. Furthermore, due to the single wafer processing, the wafers can be controlled one by one unlike a conventional case in which the wafers are controlled in lots. It is therefore possible to improve the threshold of the wafer in the heating process. 
     Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING 
     The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention, and together with the general description given above and the detailed description of the preferred embodiments given below, serve to explain the principles of the invention. 
     FIG.  1 A and FIG. 1B are schematic plan views respectively showing an upper stage and a lower stage of a coating film formation apparatus (Spin on Dielectric system) according to an embodiment of the present invention; 
     FIG. 2 is a side view of the coating film formation apparatus (SOD system) according to an embodiment of the present invention; 
     FIG. 3 is a side view of two process unit groups formed by stacking a plurality of process units in multiple layers and installed in the coating film formation apparatus (SOD system); 
     FIG. 4 is a schematic plan view of a curing apparatus (Dielectric Oxygen Density Controlled Cure and Cooling-off unit: DCC unit) according to an embodiment of the present invention; 
     FIG. 5 is a schematic sectional view of the DCC unit shown in FIG. 4, with a block diagram of the peripheral structural elements; 
     FIG. 6 is a perspective view of a ring shower nozzle of the curing apparatus (the DCC unit); 
     FIG. 7 is a flow chart of curing process (annealing); 
     FIG. 8 is a control circuit of the curing apparatus (the DCC unit) according to an embodiment of the present invention; and 
     FIG. 9 is a flow chart for temperature control of the hot plate for use in the curing apparatus (DCC unit). 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Now, various preferable embodiments of the present invention will be explained with reference to the accompanying drawing. 
     As shown in FIGS. 1A and 1B, the SOD system of an embodiment of the present invention has a process section  1 , a side cabinet  2 , and a carrier station (CSB)  3 . 
     In a front surface of an upper stage of the process section  1 , a solvent exchange unit (DSE)  11  and a first coating unit (SCT)  12  are arranged as shown in FIG.  1 A and FIG. 2. A coating solution supply source (not shown) storing a high-viscosity coating solution is placed in the first coating unit (SCT)  12 . Note that the solvent exchange unit (DSE)  11  and the first coating unit (SCT)  12  have temperature controlling means for controlling temperature of a solvent and the high-viscosity coating solution, respectively. 
     In a front surface of the lower stage of the process section  1 , a second coating unit (SCT)  13  and a chemical unit  14  are arranged as shown in FIGS. 1B and 2. A coating solution supply source (not shown) storing a low-viscosity coating solution is placed in the second coating unit (SCT)  13 . A tank (not shown) of the chemical unit  14  stores a chemical agent, pure water, or the like. 
     At a center of the process section  1 , process unit groups  16 ,  17  formed by stacking a plurality of process units vertically in multiple stages, are arranged as shown in FIGS. 1A and 1B. A transfer mechanism  18  for transporting a wafer W is interposed between these process unit groups  16 ,  17 . 
     As shown in FIG. 3, the process unit group  16  is constituted of a hot plate unit (LHP)  19  for heating low-temperature, two DCC process units  20 , and two aging units (DAC)  21  stacked in the order mentioned from above. The process unit group  17  is constituted of two hot plate units (OHP)  22  for heating high-temperature, a hot plate unit (LHP)  23  for heating high-temperature, two cooling plate units (CPL)  24 , a transfer unit  25 , and a cooling plate unit (CPL)  26  stacked in the order mentioned from above. Note that the transfer unit (TRS)  25  can serve as a stand-by portion for the cooling plate. 
     In the upper stage of the side cabinet  2 , a plurality of bubblers (bubble generators)  27  and a trap (TRAP)  28  are arranged. The trap is used for cleaning an exhausting gas. On the other hand, in the lower stage of the side cabinet  2 , a power supply source  29 , a chemical agent chamber  30 , and a drain  31  are arranged. The agent chamber  30  stores a chemical agent such as hexamethyldisilazane (HMDS) or ammonia. 
     The bubbler  27  has a tank (not shown) for storing ammonia water (NH 4 OH) and a porous nozzle (not shown) formed at the bottom of the tank. The porous nozzle is connected to a gas supply source (not shown) so that ammonia gas (NH 3 ) is supplied to the porous nozzle. When ammonia gas is supplied to the porous nozzle, it is blown into the ammonia water in the tank, generating water vapor containing a hydroxyl group (OH — ). The water vapor is supplied to the process unit group  16 . Note that the bubbler  27  is desirably arranged near the process unit group  16  including a heat process unit for preventing the generated water vapor from causing condensation. The side cabinet  2  is desirably arranged at the longest possible distance from the carrier station (CSB)  2  so that the side cabinet  2  is not influenced by ammonia or HMDS. 
     Now, we will briefly explain the case where the interlayer dielectric film is formed on the wafer W using the SOD system in accordance with, for example, the Sol-Gel method. 
     The wafer W is transferred from the carrier station (CSB)  3  to the transfer unit (TRS)  25 . The wafer W is transferred by the transfer mechanism  18  to the cooling plates (CPL)  24 ,  26 . After controlled in temperature there, the wafer W is transferred to the coating units (SCT)  12 ,  13 , in which a coating solution having colloidal tetraethoxy silane (TEOS; Si(OC 2 H 5 ) 4 ) dispersed in an organic solvent such as an ethanol solution is coated on the wafer W. Thereafter, the sol on the wafer W is changed into gel in the aging unit (DAC)  21  and then, the solvent is exchanged in the solvent exchange (DSE)  11 . Thereafter, the wafer W is appropriately heated by the hot plates (LHP)  19 ,  23  and the hot plates (OHP)  22  and returned to the carrier station (CSB)  3  by the transfer mechanism (TCP)  25 . Note that, in the case of the Sol-Gel method, the curing performed in the DCC unit  20  is not required. 
     Next, we will explain the case where the interlayer dielectric film is formed by the SiLK method, the SPEED FILM method, or the FOx method using the SOD system. 
     The wafer W is transferred to the cooling plate units (CPL)  24 ,  26  by the transfer mechanism  18  and cooled there. The wafer W is then transferred to the coating unit (SCT)  13  in which a low-viscosity coating solution is used. After the low-viscosity coating solution is applied onto the wafer W, the wafer W is heated by the hot plates (LHP)  19 ,  23 , cooled in the cooling plate units (CPL)  24 ,  26 , and coated with a high-viscosity coating solution in the first coating unit (SCT)  12 . Thereafter, the wafer W is heated in the low temperature hot plate units (LHP)  19 ,  23 , heated in the hot plate unit (OHP)  22 , and loaded into the DCC unit  20 . In the DCC unit  20 , the wafer W is heated and cooled under an atmosphere containing oxygen in a low amount. In this manner, the interlayer dielectric film is cured. 
     Now, referring to FIGS. 4-7, the DCC unit  20  serving as a curing apparatus will be explained. 
     As shown in FIGS. 4 and 5, the DCC unit  20  has a heating chamber  41  and a cooling chamber  42 . The heating chamber  41  has a hot plate  43  whose temperature can be set at 200 to 470° C. The hot plate  43  has a first temperature sensor  62  and a second temperature sensor  64  buried therein to check temperature of the hot plate  43 . The first temperature sensor  62  is connected to a circuit of the temperature controller  66 . The second temperature sensor  64  is connected to a circuit of an excessive temperature increase detector  65 . This embodiment employs a platinum (Pt) resistance temperature sensor as the first temperature sensor  62  and employs a platinum-platinum rhodium thermocouple as the second temperature sensor  64 . Note that the resistance temperature sensor or the thermocouple may be used as the first and second temperature sensors  62 ,  64 . 
     The heating chamber  41  and cooling chamber  42  are arranged side by side. The both chambers  41  and  42  are communicated with each other through a loading port  52  in order to load/unload the wafer W therethrough. 
     The DCC process unit  20  has the first and second gate shutters  44 ,  45  and a ring shutter  46 . The first gate shutter  44  is attached to a loading port  44   a  of the heating chamber  41 . When the first gate shutter  44  is opened, the loading port  44   a  is automatically opened to load/unload the wafer W into the heating chamber  41  by the main transfer mechanism  18 . The second gate shutter  45  is provided at the loading port  52  between the heating chamber  41  and the cooling chamber  42 . The second gate shutter  45  is movably supported by a cylinder mechanism  49 . When the shutter  45  is moved down, a loading port  52  is opened. When the shutter  45  is moved up, the loading port  52  is closed. 
     As shown in FIG. 4, the ring shutter  46  is provided so as to surround the hot plate  43 . The ring shutter  46  and the hot plate  43  are substantially concentrically arranged. The ring shutter  46  and the hot plate  43  keep substantially the same distance to each other. The rod of the ring shutter  46  is connected to the second gate shutter  45  by members  45   a . Both shutters  45 ,  46  are moved up and down together by the cylinder  49 . 
     As shown in FIG. 6, numerous holes  46   b  are formed in an inner peripheral surface of the ring shutter  46 . These holes  46   b  are communicated with a gas reservoir (header) of the ring shutter  46 . The gas reservoir (not shown) is communicated with a N 2  gas supply source  71  (FIG. 5) via a plurality of gas supply tubes  46   b . When N 2  gas is supplied from the N 2  gas supply source  71  to the gas supply tubes  46   b , N 2  gas is blown out uniformly from individual holes  46   b . Note that the gas blow-out holes  46   b  are formed in order for the gas to blow out virtually horizontally. 
     Furthermore, three lift pins  47  are formed on an upper surface of the hot plate  43  (wafer mounting surface) so as to protrude or retreat from the upper surface. The lift pins  47  are connected to a rod of a cylinder  48  via a member and thus supported by the cylinder  48 . Note that a shielding board screen may be interposed between the hot plate  43  and the ring shutter  46 . 
     Three cylinder mechanisms  48 ,  49 ,  50  are arranged in a lower portion of the heating chamber  41 . The cylinder mechanism  48  moves the lift pins  47  upward and downward. The cylinder mechanism  49  moves the ring shutter  46  and the second gate shutter  45  upward and downward. The cylinder mechanism  50  moves the first gate shutter  44  upward and downward. 
     As shown in FIG. 5, N 2  gas is supplied to the heating chamber  41  from the N 2  gas supply source  71  through the ring shutter  46  and exhausted through an upper exhaust pipe  51 . The N 2  gas supply source  71  and an exhaust unit  73  are controlled together by a controller  60  shown in FIG.  8 . The inner pressure of the heating chamber  41  is controlled at, for example, 50 ppm or less, by the balance between the gas supply from the N 2  gas supply source  71  and the gas release by the exhaust unit  73 . As described, an atmosphere low in oxygen concentration can be maintained by attaining a low inner pressure of the heating chamber  41 . 
     The heating chamber  41  and the cooling chamber  42  are communicated with each other through the loading port  52 . A cooling plate  53  for mounting and cooling the wafer W is movably supported by a horizontal cylinder mechanism  55  along a guide plate  54 . The horizontal cylinder mechanism  55  is communicated with a pressurized air supply source  76  serving as a driving source. The cooling plate  53  is loaded into the heating chamber  41  through the loading port  52  by the cylinder mechanism  55 , receives the wafer already heated by the hot plate  43  in the heating chamber  41  from the lift pins  47 , and load it into the cooling chamber  42 . After the wafer W is cooled, the wafer W is returned onto the lift pins  47 . 
     Note that the cooling plate  53  is set at a temperature within the range of, for example, 15 to 25° C. Temperature of the wafer W to be subjected to the cooling process falls within the range of 200 to 470° C. 
     N 2  gas is introduced into the cooling chamber  42  from the N 2  gas supply source  72  through an upper supply tube  56  and exhausted therefrom through a lower exhaust pipe  57  by an exhaust unit  74 . The N 2  gas supply source  72  and the exhaust unit  74  are controlled together by the controller  60  shown in FIG.  8 . The inner pressure of the cooling chamber  42  is controlled at, for example, 50 ppm or less by the balance between the gas supply from the N 2  gas supply source  72  and the gas release by the exhaust unit  74 . As described, a low-oxygen concentration of the atmosphere can be maintained by attaining a low inner pressure of the cooling chamber  42 . 
     Note that an oxygen sensor  75 a is attached to an exhaust passage  51  of the heating chamber  41  and an exhaust passage  57  of the cooling chamber  42  to detect oxygen concentrations of chambers  41 ,  42  by an oxygen concentration detector  75 . The oxygen concentration detector  75  sends an oxygen concentration detection signal to the controller  60 . 
     In the DCC unit  20 , a coating film of the wafer W is heated and cooled in accordance with the steps shown in FIG.  7 . 
     First, the first gate shutter  44  is opened to transfer the wafer W from the main transfer mechanism  18  onto the three lift pins  47  in the heating chamber  41  (Step S 1 ). At this time, exchange of the wafers W is not performed. 
     Then, the first gate shutter  44  is closed. The ring shutter  46  and the second gate shutter  45  move up, with the result that the wafer W is surrounded by the ring shutter  46  (Step S 2 ). At this time, supply of N 2  gas into the heating chamber  41  is initiated (Step S 3 ). The atmosphere of the heating chamber  41  is maintained at a low-oxygen concentration (e.g., 50 ppm or less) by charging the heating chamber  41  with N 2  gas. 
     Thereafter, the lift pins  47  are moved down and the wafer W is placed near the hot plate  43 . The wafer W is heated under the atmosphere low in oxygen concentration (e.g., 50 ppm or less) (Step S 4 ). The heating temperature is, for example, 200 to 470° C. At this time, the heating process performed in the heating chamber  41  is not the one performed in a heating furnace but heat radiation using the hot plate  43 . Since the hot plate  43  is surrounded by the ring shutter  46 , the wafer W is heated uniformly over an entire surface. Since the heating chamber  41  and the cooling chamber  42  are blocked by the second gate shutter  45 , the cooling chamber  42  can be prevented from being thermally influenced. 
     After the heating process is completed, the ring shutter  46  and the second gate shutter  45  are moved down and the lift pins  47  are moved up (Step S 5 ). At this time, while supply of the inner gas such as N 2  gas to the heating chamber  41  is terminated, supply of the inert gas such as N 2  gas to the cooling chamber  42  is initiated. The oxygen concentration of the atmosphere within the cooling chamber  42  is maintained low (e.g. 50 ppm or less) by charging the cooling chamber  42  with the inert gas. 
     Thereafter, the cooling plate  53  is moved into the heating chamber  41  and receives the wafer W from the lift pins  47  (Step S 6 ), and then, the lift pins  47  are moved down (Step S 7 ). 
     Subsequently, the cooling plate  53  is returned to the cooling chamber  42  and the second gate shutter  45  is moved up. The oxygen concentration of the cooling chamber  42  is controlled at, e.g., 50 ppm or less while the oxygen concentration is monitored, at the same time, the wafer W is cooled under the atmosphere low in oxygen concentration (Step S 8 ). The cooling temperature at this time is, for example, 200-400° C. Since the wafer is cooled under the low oxygen atmosphere, oxidation of the interlayer dielectric film is effectively prevented. After completion of the cooling process, the supply of N 2  gas to the cooling chamber  42  is terminated. 
     Thereafter, the second gate shutter  45  is moved down and the cooling plate  53  is loaded into the heating chamber  41  (Step S 9 ). Then, the lift pins  47  are moved up to return the wafer W from the cooling plate  53  to the lift pins  47  (Step S 10 ). 
     After the wafer W is transferred, the cooling plate  53  is returned to the cooling chamber  42  and simultaneously the first gate shutter  44  is opened (Step S 11 ). Thereafter, the wafer W is returned to the main transfer mechanism  18  (Step S 12 ). In this way, the heating process and cooling process are completed. 
     When the interlayer dielectric film formed on the wafer W is cured, the heating process and cooling process are performed in a single unit in which the heating chamber and cooling chamber are communicated each other, under the atmosphere low in oxygen concentration. Therefore, oxidation of the interlayer dielectric film can be sufficiently prevented. 
     The wafers are not heated in a batch, namely, in a furnace, but heated one by one. Therefore, it is possible to accurately control temperature of the wafers one by one. It is further possible to maintain the temperature uniformly over the entire surface when heating. Furthermore, the hating process is carried out by use of the hot plate  43  while using the ring shutter  46 . Therefore, the uniformity in temperature over the entire wafer while heating, can be greatly improved. Furthermore, since the wafers are processed one by one, it is possible to control the wafers one by one although the wafers are conventionally controlled in lots. As a result, the yield can be improved. 
     Then, how to control the DCC unit  20  will be explained. 
     In the DCC unit  20 , the wafer W is heated by the hot plate  43  in the heating chamber  41  up to a temperature within the range of 200-470° C. Since the heating temperature is higher than that used in conventional apparatus, it is difficult to control the hot plate in accordance with the conventionally employed temperature controlling method. More specifically, the temperature of the hot plate  43  is measured by a temperature sensor. However, the temperature controller usually used for the temperature sensor is capable of controlling temperature up to about 500° C. In such a high temperature range, a temperature switch conventionally used as an interlock sensor cannot be used. As a result, when the hot plate is raised in temperature excessively in the DCC unit  20 , it is difficult to control temperature of the hot plate in accordance with the conventionally-employed method. Since the processing is performed at a high temperature, operation of a driving system must be monitored. 
     Taking this into consideration, the temperature of the hot plate  43  is controlled in the DCC unit  20 , as shown in FIGS. 8 and 9. 
     In FIG. 8, the controller  60  controls the entire DCC unit  20 . To the controller  60 , an I/O board  61  is connected. To the I/O board  61 , a temperature sensor  62  for measuring temperature of the hot plate  43  is connected via a temperature controller  66 . To the temperature controller  66 , an alternating current source  70  (200V) and a solid relay (SSR)  67  are connected. The solid relay (SSR)  67  is responsible for opening and closing a power supply route to the hot plate  43 . The alternating current source  70  is responsible for supplying power to the hot plate  43 . 
     Furthermore, a thermocouple  64  is provided to measure the temperature of the hot plate  43  even if the temperature of the hot plate  43  exceeds 500° C. which is the uppermost measurement limit of the temperature controller  66 . The thermocouple  64  corresponds to the second temperature sensor. The output from the thermocouple  64  is connected to the I/O board  61  by way of an excessive temperature increase detector  65 . To the I/O board  61 , a relay  63  is connected for opening/shutting a power supply route between and the hot plate  43  and the alternating current source  70  for supplying power to the hot plate on the basis of a signal from the excessive temperature increase detector  65 . 
     In this control system, at normal operation time, the signal (temperature detection signal) based on the temperature of the hot plate  43  measured by the temperature sensor  62  is input into the controller  60  by way of the I/O board  61 . At the same time, power is supplied from the power source  70  to the hot plate  43  while the solid relay (SSR)  67  and the relay  63  are closed. As a result, the hot plate  43  is heated. At this time, since output from the power source  70  is controlled by the controller  60 , the temperature of the hot plate  43  is controlled. 
     On the other hand, when the temperature detection signal indicating that the temperature of the hot plate  43  is a first specified temperature of about 490° C. or more is input into the controller  60 , an opening signal is output from the controller  60  to the temperature controller  66  by way of the I/O board  61 . As a result, the solid relay (SSR)  67  is opened by the signal from the temperature controller  66 . In this manner, power is shut off from the power source  70  to the hot plate  43 . 
     When the power supply from the power source  70  to the hot plate  43  is shut off, temperature of the hot plate  43  decreases. When the temperature of the hot plate  43  is fixed to about 490° C. or less (the first specified temperature), a stop signal is output from the controller  60  to the solid relay (SSR)  67  by way of the I/O board  61  and the temperature controller  66  to close the solid relay (SSR)  67 . As a result, power supply from the power source  70  to the hot plate  43  is initiated again. 
     More specifically, when the temperature of the hot plate  43  reaches the first specified temperature of about 490° C. or more, the hot plate  43  is protected by the interlock mechanism on the basis of software. When the temperature of the hot plate  43  is fixed to about 490° C. or less, the heating process can be immediately initiated. 
     On the other hand, when the thermocouple (second temperature sensor)  64  detects that the temperature of the hot plate  43  is increased to a second specified temperature of about 500° C. or more, the excessive temperature increase detector  65  sends a detection signal directly to the I/O board  61  without passing through the controller  60 . The signal is further sent to the relay  63 . 
     As described, when the excessive temperature increase detector  65  detects, on the basis of the signal from the thermocouple  64 , that the temperature of the hot plate  43  reaches the second specified temperature of about 500° C. or more, a stop signal is sent to the relay  63  through the I/O board  61 . As a result, power supply from the power source  70  to the hot plate  43  is forcibly terminated and this state is maintained until the power source is shut off. When the temperature of the hot plate  43  reaches the second specified temperature of about 500° C. or more, the interlock mechanism prevents the temperature of the hot plate  43  from excessively increasing. Note that the I/O board  61  sends a signal for informing the excessive temperature increase to the controller  60  on the basis of the excessive temperature increase detection signal sent to the I/O board  61 . 
     Furthermore, an alarm mechanism  68  is connected to the controller  60 . In the case where the controller  60  receives the signal meaning that the temperature of the hot plate exceeds the first specified temperature of about 490° C., from the temperature sensor  62  through the I/O board  61  and the case where the controller  60  receives the signal meaning that the temperature sent from the excessive temperature increase detector  65  to the I/O board  61  exceeds the second specified temperature of about 500° C., a signal is sent from the controller  60  to the alarm mechanism  68  to generate the alarm. 
     As shown in FIG. 8, the controller  60  also controls the driving system  69  of the DDC process unit  20 . When individual elements of the driving system  69  are not operated in accordance with the instruction from the controller  60 , an alarm is generated from the alarm mechanism  68 . For example, when the controller  60  recognizes that the operation is not initiated even if three seconds have passed after an operation-initiation signal is output from the controller  60  to the lift pins  47 , the ring shutter  46  or the gate shutters  44 ,  45  of the heating chamber  41 , a signal is sent from the controller  60  to the alarm mechanism  68  to generate an alarm. Similarly, a signal is also sent from the controller  60  to an alarm mechanism  68  to generate an alarm when the operation is not initiated even if four or five seconds have passed after the operation-initiation signal is output from the controller  60  to the cooling plate  53  of the cooling chamber  42 . 
     Incidentally, a sensor (not shown) is provided for detecting the cases where a chamber plate is removed and set incorrectly. When the controller  60  receives the signal for ill-fitting of the chamber plate from the sensor, an alarm signal is sent to the alarm mechanism  68  to generate an alarm. In such a case, if the chamber plate is reset correctly, the alarm is automatically released. 
     Next, referring to FIG. 9, we will explain how to control the hot plate when an abnormality in temperature takes place. 
     First, the temperature of the hot plate  43  is measured by the temperature sensor  62 . A signal is sent from the temperature sensor  62  to the controller  60  by way of the temperature controller  66  and the I/O board  61  (Step S 21 ). Then, it is determined whether or not the temperature of the hot plate  43  is about 490° C. or more on the basis of the signal received by the controller  66  (Step S 22 ). When the temperature of the hot plate is the first specified temperature of about 490° C. or more, an opening signal is output from the controller  60  to the solid relay (SSR)  67  by way of the I/O board  61  and the temperature controller  66 . As a result, the solid relay (SSR)  67  is opened to thereby shut off the power supply from the power source  70  to the hot plate  43  (Step S 23 ). At the same time, an alarm is generated from the alarm mechanism  68 . On the other hand, when the temperature of the hot plate is less than about 490° C. of the first specified temperature, the measurement of the temperature is continued while the solid relay (SSR)  67  is maintained close. 
     After the power supply from the power source  70  to the hot plate  43  is shut off by detecting that the temperature of the hot plate exceeds the first specified temperature of about 490° C., then the temperature of the hot plate  43  is further measured by the temperature sensor  62  (Step S 24 ). Then, it is determined whether or not the temperature of the hot plate  43  is decreased and fixed to the first specified temperature of about 490° C. or less (Step S 25 ). When the temperature of the hot plate is fixed to about 490° C. or less, a stop signal is output from the controller  60  to the solid relay (SSR)  67  by way of the I/O board  61  to the temperature controller  66 . As a result, the solid relay (SSR)  67  is closed to initiate power supply from the power source  70  to the hot plate  43  (Step S 26 ). On the other hand, while the temperature of the hot plate is not yet fixed to about 490° C. or less, the solid relay (SSR)  67  is maintained open. 
     Even if the temperature of the hot plate  43  increase to the first specified temperature of about 490° C. or more, it is possible to prevent the temperature of the hot plate  43  from further increasing by the interlock mechanism on the basis of software. When the temperature of the hot plate  43  is decreased to less than about 490° C. by removing problems, the normal temperature control system can immediately work. 
     When the temperature of the hot plate  43  increases in excess of the first specified temperature of about 490° C. or more for some reason, temperature control is performed as follows: 
     First, when the temperature of the hot plate  43  increases to the first specified temperature of about 490° C. or more, control of temperature is performed on the basis of data measured by the thermocouple  64 . This is because about temperature of 490° C. or more does not fall within a controllable temperature range by the temperature controller  66  (Step S 31 ). Then, the excessive temperature increase detector  65  determines whether or not the temperature of the hot plate  43  measured by the thermocouple  64  is the second specified temperature of about 500° C. or more (Step S 3 ). When the temperature of the hot plate is about 500° C. or more, the signal for temperature measured by the thermocouple  64  is sent from the excessive temperature increase detector  65  to the I/O board  61  and then sent directly to the relay  63  without passing through the controller  60  (Step S 33 ). When the temperature of the hot plate  43  once increases to about 500° C. or more which is the second specified temperature, power supply from the power source  70  to the hot plate  43  is forcibly shut off. The shut off state is maintained until the power source is shut off, and simultaneously, an alarm is generated from the alarm mechanism  68 . On the other hand, when the temperature of the hot plate  43  is less than about 500° C., the thermocouple continuously measures the temperature. 
     As described, if the temperature of the hot plate  43  increases in excess of the second specified temperature of about 500° C. or more, it is possible to prevent the hot plate  43  from being heated excessively since power supply is forcibly terminated mechanically (in hardware). 
     As mentioned in the foregoing, the apparatus has dual interlock mechanisms, one is in software and the other is in hardware. Therefore, it is possible to prevent excessive heating of the hot plate  43  while the temperature of the hot plate  43  is appropriately controlled at a relatively high temperature. 
     The power supply route to the hot plate  43  is opened or closed at the solid relay (SSR)  67  or the relay  63 . Therefore, when the hot plate  43  is excessively heated, the power supply to the hot plate  43  can be completely shut off. Furthermore, when the power supply to the hot plate  43  is terminated, an alarm is generated by the alarm mechanism  68 . It is therefore possible for an operator to immediately know that the temperature of the hot plate  43  is too high. Thus, the operator can immediately take appropriate procedures to deal with it. 
     Furthermore, an inert gas such as N 2  gas is supplied to each of the heating chamber  41  and the cooling chamber  42  and simultaneously exhausted therefrom. It is therefore possible to treat a wafer in the atmosphere low in oxygen concentration while another wafer is load/unload. 
     The present invention is not limited to the aforementioned embodiments and may be modified in various ways. For example, the substrate to be processed is not limited to a semiconductor wafer. Other substrates including an LCD substrate may be used. The coating film is not limited to the interlayer dielectric film. Any film may be applicable as long as the film is required to be cured by heating after coating in an atmosphere low in oxygen concentration. 
     According to the present invention, the heating process and the cooling process can be continuously performed in an atmosphere low in oxygen concentration. As a result, oxidization of the coating film can be sufficiently prevented. Since the wafers W are processed one by one in the heating chamber, it is possible to accurately control the temperature of the wafers one by one. As a result, the heating process can be applied uniformly to the entire surface of the wafer. Since the wafers are processed one by one, the wafers can be controlled one by one unlike a conventional method in which the wafers are controlled in lots. Consequently, the yield can be improved. 
     Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.