Heat processing apparatus and heat processing method

A heat processing apparatus for heating a mask substrate is disclosed. A mask substrate on which a coating solution has been coated is placed on a heating plate that heats the substrate. A frame member is disposed on the heating plate so that the frame member faces a side surface of the mask substrate placed on the heating plate when the frame member is attached to the heating plate and that a clearance is formed between the frame member and the heating plate when the frame member is attached to the heating plate. The frame member suppresses heat radiated from the side surface of the substrate. As a result, the temperature uniformity of the surface of the substrate can be improved. In addition, since the clearance is formed between the frame member and the heating plate, particles do not accumulate in the region. Thus, adhesion of particles to the substrate can be suppressed.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a heat processing apparatus and a heat processing method for performing a heat process for a substrate such as a mask substrate on which for example a resist solution has been coated.

2. Description of the Related Art

When a semiconductor mask is formed in a fabrication process for a semiconductor device, a resist solution is coated on a square mask substrate. With a photo mask, the resist film is exposed and developed. As a result, a desired resist pattern is formed. As such a substrate, for example a six-inch size square glass substrate having four sides each of which is 152 mm long and having a thickness of 6.35 mm is used.

The resist solution is made by dissolving a component of a coating film in a solvent. After the resist solution is coated on a substrate, a heating process for heating the substrate at a predetermined temperature and evaporating the solvent is preformed. The heating process is performed by placing a substrate on a heating plate that has a heater. However, when a substrate has a large thickness as described above, the temperature uniformity of the surface of the substrate tends to deteriorate. In other words, when a substrate has a large thickness, heat radiated from the side surfaces of the substrate is large, therefore, there is a tendency of which the temperature of the peripheral region of the substrate is lower than the temperature of the center region. Thus, when the substrate temperature varies on the surface of the substrate, the evaporation amount of the solvent varies on the surface. As a result, the uniformity of the surface of the resist film deteriorates.

Thus, as shown inFIG. 19, a concave portion11is formed in a heating plate10. A substrate12is placed in the concave portion11. In this state, the substrate12is heated by the heating plate10. As a result, vicinity regions of the side surfaces of the substrate are heated by the heating plate10. Thus, heat radiation from the side surfaces can be suppressed. InFIG. 19, reference numeral13represents a heater. However, in such a method, particles may accumulate at corner portions of the concave portion11. It is difficult to remove these particles. In addition, there is a possibility particles adhering to the substrate12. Moreover, to form the concave portion11in the heating plate10, long time and great cost will be required. Thus, the fabrication cost of the substrate will rise.

To suppress heat radiation from the side surfaces of the substrate, the inventors of the present invention are devising a technique of which a side plate14is disposed around a substrate12placed on a heating plate10as shown inFIG. 20. As examples of such a technique, a structure of which an outer frame that is higher than an object to be processed and surrounds the object is disposed at a predetermined placement position of the object on a heating plate (refer to, for example, Japanese Patent Laid-open Publication No. 11-204428 published by Japan Patent Office), a structure of which a side plate that is equal to or higher than a mask and that surrounds it is disposed on a heating plate, and a structure of which a side heating plate disposed around a mask placed on a heating plate prevents heat radiation from side surfaces of the mask (refer to for example Japanese Patent Laid-open Publication No. 2002-100562 published by Japan Patent Office) have been proposed.

However, the publication No. 11-204428 discloses the outer frame so as to prevent air from entering the vicinity of a substrate. Thus, the outer frame is disposed on the heating place without a clearance. Likewise, the publication No. 2002-100562 discloses the structure of which the side plate and the side heating plate are disposed without a clearance as shown inFIG. 4andFIG. 6of the publication. Since the outer frame of the publication No. 11-204428 and the side plate of the publication No. 2002-100562 are disposed in such a manner that they are higher than the front surfaces of the object to be processed and the mask. Thus, as shown inFIG. 21, when particles15scatter by an air current in a processing vessel and contact the front surface of the substrate12, the particles15may cause a defect of the substrate to be processed. When the particles15enter a clearance formed between the substrate and the side plate14or the like, the particles15do not scatter, but accumulate at corner portions between the side plate14or the like and the heating plate10. As a result, there is a possibility of which the substrate12is contaminated by particles15.

SUMMARY OF THE INVENTION

The present invention is made from the foregoing point of view. An object of the present invention is to provide a technology that secures high temperature uniformity of the surface of a substrate placed on a heating plate and heated thereby.

Another object of the present invention is to provide a technology for satisfying both suppression of contamination of a substrate with particles and improvement of temperature uniformity of the surface of a substrate.

The present invention is an apparatus, for heat-processing a mask substrate, comprising a heating plate for heating the mask substrate, heating means for heating the heating plate and a frame member being detachably disposed to the heating plate so that the frame member faces a side surface of the mask substrate placed on the heating plate when the frame member is attached to the heating plate.

In such a structure, when the mask substrate is heated by the heating plate, since the frame member is disposed opposite to the side surfaces of the mask substrate, heat radiation from the side surfaces of the mask substrate can be suppressed. Thus, the temperature uniformity of the surface of the mask substrate can be improved. In addition, the frame member is detachably disposed on the heating plate. Thus, particles that accumulate between for example the frame member and each of the side surfaces of the mask substrate can be removed by detaching the frame member from the heating plate. Consequently, maintenance of the apparatus can be easily performed. In addition, contamination of the heating plate with particles can be suppressed. In this example, the mask substrate means a substrate having an exposure light passing portion and an exposure light insulating portion that are used to form a wiring pattern on a semiconductor wafer or a glass substrate for a liquid crystal device.

According to an aspect of the present invention, a clearance is formed between the frame member and the heating plate when the frame member is attached to the heating plate. In such a structure, particles can be prevented from accumulating between the frame member and the heating plate. As a result, particles can be prevented from adhering to the mask substrate.

According to an aspect of the present invention of the present invention, the frame member has a surface opposite to the side surface of the mask substrate placed on the heating plate, and the surface is curved in a concave shape and a convex shape. In such a structure, the frame member is curved in such a manner that a near portion and a far portion to the mask substrate are formed in the frame member. Thus, an appropriate portion of the side surfaces of the mask substrate can be selectively heated by the frame member. As a result, a heat radiation from the side surfaces of the mask substrate can selectively be controlled, thus high temperature uniformity of the surface of the mask substrate can be secured.

According to an aspect of the present invention, the surface is a mirror surface. Thus, heat radiated from the side surfaces of the mask substrate is reflected by the mirror surface of the frame member. As a result, the temperatures of the side surfaces of the mask substrate can be prevented from decreasing.

According to an aspect of the present invention, the surface is a rough surface. In this example, the rough surface is a surface whose surface roughness is larger than the mirror surface. For example, the rough surface has a roughness of around Ra=100 μm. Thus, heat radiation from the rough surface of the frame member increases. The heat radiation causes the side surfaces of the mask substrate to be heated. In addition, the temperatures of the side surfaces of the mask substrate can be prevented from decreasing.

According to an aspect of the present invention, the heat processing apparatus further comprises a driving mechanism for moving the frame member so that a distance between the frame member and the side of the mask substrate placed on the heating plate varies. In addition, the heat processing apparatus further comprises means for detecting a temperature of the mask substrate and a controlling portion for controlling the driving mechanism in accordance with the detected temperature. In such a structure, by having the frame member to move away from the mask substrate and approach closer to it, heat radiation from the side surfaces of the mask substrate is controlled. As a result, the temperature uniformity of the surface of the mask substrate can be improved.

According to an aspect of the present invention, the controlling portion determines whether the temperature of the mask substrate is in a rising state or in a constant state in accordance with the detected temperature, controls the driving mechanism so that the distance between the frame member and the side surface of the mask substrate placed on the heating plate becomes a first distance when the temperature of the mask substrate is in the rising state and a second distance smaller than the first distance when the temperature of the mask substrate is in the constant state.

According to an aspect of the present invention, the frame member is divided in a peripheral direction of the mask substrate placed on the heating plate. Thus, by independently controlling the positions of the divided frame members, the temperature of each portion of the mask substrate can be adjusted. As a result, the temperature uniformity of the surface of the substrate can further be improved.

According to an aspect of the present invention, the frame member has a heating mechanism for heating the frame member. Thus, since the frame member itself can be heated, the side surfaces of the mask substrate can be more securely and easily heated than the structure without the heating mechanism.

The mask substrate is a approximately square glass substrate having a side of six inches long, and the heating plate is a circular plate for heating a semiconductor wafer having a diameter of 10 inches or 12 inches.

The present invention is a heat processing method for heating a mask substrate placed on a heating plate, comprising the steps of (a) detecting a temperature of the mask substrate and (b) moving a frame member disposed facing a side surface of the mask substrate placed on the heating plate, so that a distance between the mask substrate and the frame member varies in accordance with the detected temperature.

According to the present invention, by varying the distance between the frame member and each of the side surfaces of the mask substrate in accordance with the temperature change of the mask substrate, the temperature uniformity of the surface of the mask substrate can be improved. The detection of temperature of the mask substrate includes meaning of estimation of temperature of the mask substrate as well as the detection of the temperature of the mask substrate itself.

According to an aspect of the present invention, the step (b) has the steps of: determining whether the temperature of the mask substrate is in an increasing state or in a constant state based on the detected temperature, moving the frame member so that the distance becomes a first distance when the temperature is in the increasing state and moving the frame member so that the distance becomes a second distance smaller than the first distance when the temperature is in the constant state. Thus, while the temperature of the mask substrate is in the temperature increasing state, heat radiation is promoted. In contrast, when the temperature of the mask substrate is in the temperature constant state, heat radiation is suppressed. Thus, the temperature uniformity of the surface of the mask substrate can be improved.

DESCRIPTION OF PREFERRED EMBODIMENTS

Next, a coating film forming apparatus in which a heat processing apparatus is disposed according to an embodiment of the present invention will be described.FIG. 1is a plan view showing an overall structure of the coating film forming apparatus according to the embodiment of the present invention.FIG. 2is a schematic perspective view showing the coating film forming apparatus shown inFIG. 1. In these drawings, B1represents a carrier block that loads and unloads a carrier C that accommodates for example five substrates for example mask substrates G. The carrier block B1has a carrier placing portion21and a transferring means22. The carrier C is placed on the carrier placing portion21.

Each mask substrate G is a glass substrate on which for example a semiconductor mask is formed. The mask substrate G is a six-inch size square glass substrate having four sides each of which is 152±0.5 mm long and having a thickness of 6.35 mm. The transferring means22is movable leftward, rightward, forward, and backward, liftable upward and downward, and rotatable around the vertical axis so as to take out a substrate G from the carrier C and transfer it to a processing portion B2disposed on the far side of the carrier block B1.

A main transferring means23is disposed in the middle of the processing portion B2. The main transferring means23is surrounded by a coating unit24, a developing unit25, a cleaning unit26, and shelf units U1and U2. The coating unit24and the developing unit25are disposed for example on the right viewed from the carrier block B1. The cleaning unit26is disposed on the left viewed from the carrier block B1. The shelf units U1and U2are disposed on the near side and the far side viewed from the carrier block B1. The shelf unit U1and the shelf unit U2each have units of a heating and cooling system piled in multiple tires. The coating unit24is a unit that performs a process for coating a resist solution on a substrate. The developing unit25is a unit that performs a developing process for an exposed substrate continuously soaked in a developing solution for a predetermined time period. The cleaning unit26is a unit that washes a substrate before a resist solution is coated thereon.

Each of the shelf units U1and U2are composed of a plurality of units that are piled in succession. For example, as shown inFIG. 2, a heat processing unit3, a cooling unit27, a substrate G transferring unit28, and so forth are piled in succession. The main transferring means23is liftable upward and downward, movable forward and backward, and rotatable around the vertical axis. The main transferring means23transfers a substrate G among the shelf units U1and U2, the coating unit24, the developing unit25, and the cleaning unit26. However, for simplicity, inFIG. 2, the transferring means22and the main transferring means23are omitted.

The processing portion B2is connected to an aligner B4through an interface portion B3. The interface portion B3has a transferring means29. The transferring means29is for example liftable upward and downward, movable leftward, rightward, forward, and backward, and rotatable around the vertical axis. The transferring means29transfers a substrate G between the processing portion B2and the aligner B4.

Next, a flow of a substrate G in the coating film forming apparatus will be described. First of all, a carrier C is loaded from the outside to the carrier placing portion21. The transferring means22takes out a substrate G from the carrier C. The substrate G is transferred from the transferring means22to the main transferring mechanism23through the transferring unit28of the shelf unit U1. The substrate G is successively transferred to predetermined units. For example, the cleaning unit26performs a predetermined cleaning process for the substrate G. The substrate G is heated and dried by one of the heat processing units. Thereafter, the temperature of the substrate G is adjusted to a predetermined value by one of cooling units27. One of the coating units24performs a coating process for the substrate G with a resist solution of which a component of a coating film is dissolved with a solvent.

Thereafter, one of the heat processing units performs a pre-baking process for the substrate G so as to heat it at a predetermined temperature and evaporate and remove the solvent of the resist solution from the substrate G. Thereafter, one of the cooling units27adjusts the temperature of the substrate G to a predetermined value. Thereafter, the main transferring means23transfers the substrate G to the transferring means29of the interface portion B3through the transferring unit28of the shelf unit U2. The transferring means29transfers the substrate G to the aligner B4. The aligner B4performs a predetermined exposing process for the substrate G. Thereafter, the substrate G is transferred to the processing portion B2through the interface portion B3. One of the heat processing units heats the substrate G at a predetermined temperature as a post-exposure process. Thereafter, one of the cooling units27cools the substrate G to a predetermined temperature so as to adjust the temperature of the substrate G. Thereafter, the developing unit25performs a predetermined developing process for the substrate G in such a manner that it is soaked in a developing solution. As a result, a predetermined circuit pattern has been formed on the substrate G. The substrate G is returned to the former carrier C through the main transferring means23and the transferring means22of the carrier block B1.

Next, with reference toFIG. 3, the heat processing unit3that is a heat processing apparatus according to an embodiment of the present invention will be described. The heat processing unit3coats a resist solution on a substrate G and then performs a process for removing a solvent from the resist solution. InFIG. 3, reference numeral31represents a processing container. An opening portion31ais formed for example on all the periphery of the side surfaces of the processing container so that the main transferring means23can access the inside of the processing container31through the opening portion31a. An upper portion of the opening portion31ais structured as an exhaust portion32that exhausts air from the processing container31. At a approximately center region of a ceiling portion of the processing container31is an exhaust opening32a. An exhausting means (not shown inFIG. 3) is connected to the exhaust opening32aso that atmospheric gas of the processing space can be exhausted to the outside.

A heating plate4is disposed at a predetermined position in the processing container31in such a manner that a substrate G can be transferred to and from the main transferring means23through the opening portion31a. The substrate G is placed on the heating plate4through the proximity pins41in such a manner that the substrate G slightly floats by for example around 0.5. In such a manner, the substrate G is heated by the heating plate4.

For example, as shown inFIG. 4andFIG. 5, the heating plate4is composed of a heating plate used for a heat process for a wafer having a diameter of 12 inches. In other words, the heating plate4is composed of a circular plate having a diameter of around 330 mm and a thickness of around 30 mm. The heating plate4is made of for example an aluminum alloy or stainless steel.

The heating plate4has an inner heater42that is a heating means. The heater42heats a substrate G at around 100° C. to 250° C. For example, as shown inFIG. 6, the heater42is composed of three heaters42a,42b, and42c. The heater42ais a circular plane heater42a. The heaters42band42care disposed in a concentric circle shape. The heater42ais surrounded by the heaters42band42c. The heaters42a,42b, and42care disposed in such a manner that not only a region on which the substrate G is placed, but all the surfaces of the heating plate4can be fully heated. In this example, the ring-shaped heaters42band42care disposed outside the region on which the substrate G is placed. It should be noted that the number and shape of heaters42are not limited to those of the example. In addition, the plane heater42amay be formed in a square shape. The ring-shaped heaters42band42cmay be formed in a square ring shape. The number of ring-shaped heaters may be increased or decreased. Alternatively, the substrate G may be heated by a plurality of ring-shaped heaters without use of a plane heater.

For example four supporting pins43are disposed in the heating plate4so as to transfer a substrate G to and from the main transferring means23. The supporting pins43are connected to a lifting mechanism44through a holding plate42adisposed below the heating plate4. The lifting mechanism44causes tips of the supporting pins43to protrude and recess against the front surface of the heating plate4so that the heating plate4can be lifted upward and downward.

As shown inFIG. 4andFIG. 5, a frame member5is disposed around a substrate G placed on the heating plate4in such a manner that a clearance A is formed between the frame member5and the substrate G. The frame member5is made of for example a square ring. Supporting portions51support for example a lower surface of the frame member5. As a result, the frame member5is disposed above the front surface of the heating plate4with a small clearance B. The frame member5and the supporting portions51are made of a material having heat conductivity such as an aluminum alloy.

It is preferred that the clearance A formed between each of the side surfaces of the substrate G and the inner peripheral surface of the frame member5should be set in the range from for example around 1 mm to 10 mm and that the clearance B formed between the lower surface of the frame member5and the front surface of the heating plate4should be set in the range from for example around 0.1 mm to 0.5 mm. In addition, it is preferred that a height C of the frame member5should be set to the same as or slightly smaller than the height of the front surface of the substrate G. For example, the height C from the front surface of the heating plate4to the front surface of the frame member5is set in the range from for example around 5 mm to 6 mm. A width D of the frame member5is set to for example around 10 mm.

The opening portion31aof the processing container31can be freely opened and closed with a cylindrical shutter33. The shutter33is composed of a cylindrical member33aand a horizontal piece33b. The cylindrical member33ais disposed outside the heating plate4. The horizontal piece33bis disposed at an upper end of the cylindrical member33aand protrudes inward. The shutter33is liftable downward between an open position of the opening portion31awhere the horizontal piece33bis placed in the vicinity of a lower position of the opening portion31aand a close position of a almost close position of the opening portion31awhere the horizontal piece33bis placed in the vicinity of an upper position of the opening portion31a. When the shutter33is lifted upward, it is stopped at a position where a small clearance E is formed between the upper surface of the horizontal piece33band the lower surface of the exhaust portion32. InFIG. 3, reference numeral35represents a stopper that stops the shutter33at a predetermined height.

When a substrate G is loaded into the heat processing unit3or unloaded therefrom, the shutter33is lowered and the main transferring means23is entered into the processing container31through the opening portion31a. With cooperating operations of the main transferring means23and the supporting pins43, the substrate G is transferred to and from the heating plate4. After the substrate G is placed at a predetermined position of the heating plate4, the main transferring means23is caused to retreat from the processing container31. Thereafter, the shutter33is lifted upward. As a result, the heat processing unit3is shut out with a clearance E formed between the exhaust portion32and the shutter33. In other words, while air is being exhausted in a so-called semi-closed state, the substrate G is heated at for example around 120° C. by the heating plate4.

According to the present embodiment, since the frame member5is disposed around the substrate G, the frame member5suppresses heat radiation from the side surfaces of the substrate. As a result, the temperature uniformity of the surface of the substrate can be improved. Since the frame member5and the supporting portions51have thermal conductivity, heat of the heating plate4is transferred to the frame member5through the supporting portions51. Alternatively, heat of the heating plate4is transferred to the frame member5by radiant heat of the heating plate4. As a result, the frame member5itself is heated. Since the inner peripheral surface of the frame member5is disposed only in the vicinities of the side surfaces of the substrate G, the vicinities of the side surfaces of the substrate G are heated by the frame member5. Thus, even if the thickness of the substrate G is large, heat radiation from the side surfaces of the substrate can be suppressed.

In the processing container31, an air current that flows from the clearance E formed between the shutter33and the exhaust portion32to the exhaust opening32atakes place. Thus, particles may scatter along the air current, which flows from the outside of the substrate G to the inside of the heat processing unit3. At that point, when the height of the frame member5is lower than the height of the front surface of the substrate G, since particles100collide with each of the side surfaces of the substrate G and enter the clearance A formed between each of the side surfaces and the frame member5, adhesion of the particles100to the front surface of the substrate G can be suppressed as shown inFIG. 7. In addition, since the clearance B is formed between the frame member5and the heating plate4, the particles100that enter the clearance A formed between the substrate G and the frame member5are exhausted with an exhaust current that takes place in the processing container31through the clearance B. Thus, the particles100can be prevented from accumulating at corner portions between the frame member5and the heating plate4. As a result, contamination of the substrate G with the particles can be suppressed.

In this example, since the heating plate4is a conventional circular plate that heats a wafer having a diameter of 12 inches, it is not necessary to newly prepare a heating plate that heats a square substrate having four sides each of which is six inches long. Thus, the heat processing apparatus is advantageous from a view point of cost. While one side of the six-inch size square substrate is approximately 152 mm, the diameter of the heating plate4is as large as around 330 mm. Thus, the temperature uniformity of the surface of the substrate can further be improved.

It is thought that the reason results from the following. When the substrate G is placed on the heating plate4, the shutter33is closed, and then the process is started, since the inside of the shutter33is cooled, an air current that flows from the outside of the substrate G to the inside thereof is cooled by the shutter33. In this case, if the heating plate is slightly larger than the substrate G, the cold air directly reaches the substrate G. As a result, the temperature of the outer peripheral region of the substrate G lowers. In addition, since the heating plate4radiates heat outward from the peripheral region thereof, heat radiation from the side surfaces of the substrate G is promoted. This causes the temperature of the outer peripheral region of the substrate G to lower. However, if the temperature of the heater in the peripheral region of the heating plate4is tried to be raised against the heat radiation, since the heating plate4is close to the region on which the substrate G is placed, the temperature of the peripheral region of the substrate G excessively rises. As a result, the temperature uniformity of the surface of the substrate deteriorates.

In contrast, when the size of the heating plate4is sufficiently larger than the size of a substrate G, a heater is also disposed outside the region on which the substrate G is placed, and all the heating plate4is heated, the air current cooled by the shutter33is sufficiently heated by the heating plate4until the air current reaches the substrate G. Thus, since a cold air current does not reach the substrate G, the temperature of the outer peripheral region of the substrate G can be prevented from decreasing. In addition, even if heat radiation takes place from the peripheral region of the heating plate4, the peripheral region of the heating plate4is heated so as to compensate the heat radiation. However, since the peripheral region of the heating plate4is far apart from the region on which the substrate G is placed, the heat radiation of the heating plate4does not affect the temperature of the substrate G. As a result, the temperature of the outer peripheral portion of the substrate G does not easily lower. Consequently, the temperature uniformity of the surface of the substrate G can be improved.

Next, another example of the frame member5will be described. In this example, the frame member5is structured in such a manner that an inner surface thereof (a surface opposite to the side surfaces of the substrate G) is curved.FIG. 8AandFIG. 8Bare a plan view and a perspective view, respectively, showing a frame member5A having an inner surface61(a surface opposite to each of side surfaces of a substrate G) curved in a concave surface shape. In this example, the frame member5A is structured in such a manner that a vicinity region of each corner portion of the substrate is close to the inner surface61of the frame member5A and that a vicinity region of a center portion of each side surface of the substrate G is apart from the inner surface61of the frame member5A. Thus, the vicinity of each corner portion of the substrate G is selectively heated by the frame member5A.

The frame member5A is effective when the processing temperature of the substrate G is as large as for example 200° C. or higher and heat radiation from the heating plate4is large. When the processing temperature is high, heat radiation from the four corners of the substrate G becomes large. Thus, when the corners of the substrate G are close to the frame member5A and the center regions of the side surface of the substrate G are apart from the frame member5A, the corner portions of the substrate G are selectively heated by the frame member5A. As a result, heat radiation from these regions can be suppressed. As a result, the temperature uniformity of the surface of the substrate can be improved.

FIGS. 9A and 9Bare a plan view and a perspective view, respectively, showing a frame member5B having an inner surface62curved in a convex surface shape. In the example, the inner surface of the frame member5B is formed in such a manner that a vicinity region of a center portion of each side of the substrate G is close to the inner surface62of the frame member5B and that a vicinity region of each corner portion of the substrate G is apart from the inner surface62of the frame member5B. Thus, the vicinity regions of the center portions of the sides of the substrate G can be selectively heated by the frame member5B.

The frame member5B is effective when the processing temperature of the substrate G is as low as 100° C. and the substrate G is heated by thermal conduction from the heating plate4through the proximity pins41. When the substrate G is heated by thermal conduction through the proximity pins41, the temperatures of contact regions of the proximity pins41and the substrate G become higher than the temperatures of the other regions. The proximity pins41are often disposed in the vicinity regions of the corner portions of the substrate G. Thus, the temperatures of the vicinity regions of the corner portions are higher than the temperatures of the other regions. Thus, when the vicinity regions of the corner portions of the substrate G are apart from the frame member5B and the vicinity regions of the center portions of the side surfaces of the substrate G are close to the frame member5B, heat radiation from the four corners of the substrate G becomes large and the center portions of the side surfaces of the substrate G are selectively heated by the frame member5B. As a result, the temperature uniformity of the surface of the substrate can be improved.

Alternatively, the inner surface of the frame member5(5A,5B) may be mirror surface, the inner surface of the frame member5(5A,5B) being opposite to the substrate G. In this case, heat radiated from each of the side surfaces of the substrate G is reflected by the inner surface of the frame member5and so forth. As a result, the temperature of each of the side surfaces of the substrate G can be prevented from decreasing. In addition, the inner surface of the frame member5may be a rough surface. The rough surface is a surface whose surface roughness is around Ra=100 μm. In this case, heat radiated from the inner surface of the frame member5and so forth becomes large. The radiated heat heats each of the side surfaces of the substrate G. As a result, the temperature of each of the side surfaces of the substrate G can be prevented from decreasing.

In the foregoing, when the inner surface of the frame member5A,5B is curved or formed of a mirror surface or a rough surface, the frame member5A,5B may be disposed on the heating plate4without a clearance.

Next, another example of the frame member will be described. In this example, a frame member5C is movable so that the distance between the inner surface of the frame member5C and each of the side surfaces of the substrate G placed on the heating plate4is varied. In reality, the frame member5C is composed of a four rod-shaped plates71(71a,71b,71c, and71d) that are opposite to the side surfaces of the substrate G. Each plate71is approximately horizontally movable by for example a driving mechanism73that is disposed for example below the heating plate4through for example supporting members72that pierce the heating plate4in such a manner that the inner surfaces of the plates71approach the side surfaces of the substrate G placed on the heating plate and move away therefrom.

The driving mechanism73is composed of for example a ball screw, an air cylinder, and so forth. The driving mechanism73is controlled by for example a controlling portion200in such a manner that the distance between the side surface of the substrate G and the inner surface of the frame member5C is varied in the range from for example around 1 mm to 10 mm in accordance with the processing temperature and processing time for the substrate G.

In such a structure, when the temperature of the substrate G is raised, the temperature of a peripheral region thereof tends to rise. Thus, as shown inFIG. 11A, the plate71is placed at a position apart from the side surface of the substrate G so as to prevent the temperature of the peripheral region of the substrate G from increasing. When the temperature of the substrate G is in a temperature constant state after the temperature of the substrate G has been raised, the temperature of the peripheral region thereof tends to lower. Thus, as shown inFIG. 11B, the plate71is approached to the side surface of the substrate G so as to prevent the temperature of the peripheral region thereof from decreasing. As a result, the temperature uniformity of the surface of the substrate can further be improved.

Alternatively, as shown inFIG. 12A, a frame member5D may be used. The frame member5D is composed of plates81(81a,81b,81c, and81d) to83(83a,83b,83c, and83d) of which the plates71ato71dshown inFIG. 10AandFIG. 10Bare divided into three portions each in their longitudinal directions. The divided plates81(81ato81d) to83(83ato83d) are driven by a horizontal driving mechanism so that the distance between each of the divided plates81(81ato81d) to83(83ato83d) and each of the side surfaces of the substrate G can be varied. As shown inFIG. 12B, by placing the divided plates81to83in such a manner that the distance between each of the divided plates82and the vicinity region of each side of the substrate G and the distance between each of the divided plates81and83and the vicinity region of each corner portion of the substrate G become proper values, amounts of heat radiated from the center portion of each side and each corner portion of the substrate G are controlled. Thus, since the temperature of each portion of the substrate G can be controlled. As a result, the temperature uniformity of the surface of the substrate can further be improved.

In addition, according to the present embodiment, as shown inFIG. 13, a heater91as a heating mechanism composed of a resistor heating member may be disposed in a frame member5E. The temperature of the heater91may be varied by a controlling portion (not shown inFIG. 13) in accordance with the processing temperature and processing time for the substrate G. The amount of heat radiated from the substrate G is varied in accordance with the temperature of the frame member5E. Thus, when the temperature of the frame member5E is optimally adjusted at timings of which the temperature of the substrate G is increasing, decreasing, and constant, the amount of heat radiated from the substrate G is optimally controlled. As a result, the temperature uniformity of the surface of the substrate can be improved.

In the structures shown inFIG. 10toFIG. 13, the frame members5C,5D, and5E may be disposed on the heating plate4without a clearance.

Next, examples that the inventors of the present invention conducted to confirm the effects of the present invention will be described.

FIRST EXAMPLE

A square-type substrate having four sides each of which is six inches long and having temperature sensors was placed on a circular heating plate that has a diameter of 330 mm and that is used to heat a semiconductor wafer having a diameter of 12 inches. A frame member made of an aluminum alloy was disposed around the substrate. The substrate was heated at 120° C. by the heating plate and the substrate was kept in a temperature constant state. In that state, the temperatures of the surface of the substrate were detected. At that point, the distance between each of the side surfaces of the substrate and the inner surface of the frame member was 2 mm. The height of the frame member from the front surface of the heating plate was 6 mm. The width of the frame member was 10 mm. The distance between the lower surface of the frame member and the front surface of the heating plate was 0.1 mm. In this example, a heating plate having a diameter of 330 mm was exemplified. However, it should be noted that as long as the heating plate can heat a semiconductor wafer having a diameter of at least 10 inches, the diameter of the heating plate is not limited.

In the square substrate having temperature sensors, temperature sensors were disposed at 31 positions of the surface of the substrate. In accordance with measured values of the temperature sensors, a temperature distribution on the surface of the substrate is created. The measured result is shown inFIG. 14A. The range width of the temperatures of the surface of the substrate was 1.07° C. It is clear that the smaller the range width is, the higher the temperature uniformity of the surface of the substrate becomes.

An experiment was conducted in the same condition as the first example except that a frame member was not disposed around the substrate. A temperature distribution on the surface of the substrate was created. The result is shown inFIG. 14B. The range width of the temperatures on the surface of the substrate was 1.51° C.

The heating plate was changed to a circular heating plate that has a diameter of 270 mm and that is used to heat a semiconductor wafer having a diameter of eight inches was used. In addition, the frame member was not disposed around the substrate. Except for those, an experiment was conducted in the same condition as the first example and a temperature distribution on the surface of the substrate was created. The result is shown inFIG. 14C. The range width of the temperatures on the surface of the substrate was 1.93° C.

These results show that the temperature uniformity of the surface of the substrate of each of the first example and the first comparison is higher than that of the second comparison. Thus, it is understood that it is effective to heat a square substrate that has four sides each of which is six inches long and that uses the circular heating plate used to heat a wafer having a diameter of 12 inches.

In addition, when the first example is compared with the first comparison, the graph of the first comparison shows a tendency of which the temperature in the vicinity of the center portion of the substrate is high and the temperature on the outer periphery of the substrate is low (namely, the temperature of the substrate lowers as the distance from the center portion toward the outer peripheral portion becomes large). However, the experimental result of the first example shows that the difference between the temperature at the center portion of the substrate and the temperature at the outer peripheral portion is small and that when the frame member is disposed around the substrate, the temperature uniformity of the surface of the substrate can be improved. In addition, in the structure of the first example, particles were not found between the frame member and the heating plate.

SECOND EXAMPLE

A square substrate having four sides each of which is six inches long and having temperature sensors was placed on a circular heating plate that has a diameter of 330 mm and that is used to heat a semiconductor wafer having a diameter of 12 inches. A frame member made of an aluminum alloy was disposed around a substrate. The substrate was heated at 150° C. and kept in a temperature constant state by the heating plate. In that state, the temperature on the surface of the substrate were measured. At that point, the substrate was supported by proximity pins disposed on the front surface of the heating plate in such a manner that the substrate floated on the front surface of the heating plate by 80 μm. The distance between each of the side surfaces of the substrate and the inner surface of the frame member was 2 mm. The height of the frame member from the front surface of the heating plate was 6 mm. The width of the frame member was 10 mm. The distance between the lower surface of the frame member and the front surface of the heating plate was 0.1 mm.

FIG. 15Ashows a chronological change of measured values of the temperatures of the 31 temperature sensors of the substrate. In the ranges of two temperature curves, temperature curves of the measured values of all the temperature sensors are contained. The results of an experiment conducted two times show that the range widths of the temperatures on the surface of the substrate were 0.95° C. and 1.04° C. in a time period from 400 seconds to 600 seconds after the substrate was heated and the temperature of the substrate became stable.

Except that the frame member was not disposed around the substrate, an experiment was conducted in the same condition as that of the second example.FIG. 15Bshows a chronological change of measured values of the temperatures of the temperature sensors. The range width of the temperatures on the surface of the substrate in a time period from 400 seconds to 600 seconds after the substrate was heated and the substrate temperature became stable was 1.27° C.

THIRD EXAMPLE

Except that the substrate was heated at 220° C., an experiment was conducted in the same condition as the second example.FIG. 16Ashows a chronological change of measured values of the temperatures of temperature sensors. The range width of the temperatures on the surface of the substrate in a time period from 400 second to 600 seconds after the substrate was heated and the substrate temperature became stable was 1.50° C.

Except that the frame member was not disposed around the substrate, an experiment was conducted in the same condition as that of the third example.FIG. 16Bshows a chronological change of measured values of the temperatures of the temperature sensors. The range width of the temperatures on the surface of the substrate in a time period from 400 seconds to 600 seconds after the substrate was heated and the substrate temperature became constant was 2.30° C.

When the substrate was heated at 150° C. and 220° C., the range width of the temperatures on the surface of the substrate in the structure of which the frame member was disposed is lower than that in the structure of which the frame member was not disposed. Thus, it is clear that with the frame member, high temperature uniformity of the surface of the substrate can be secured. In the structures of the second and third examples, particles were not found between the frame member and the heating plate.

Next, with reference toFIG. 17, a heat processing apparatus according to another embodiment of the present invention will be described with respect to the difference with the foregoing embodiment.

As shown inFIG. 17, according to the present embodiment, plates55A,55B,55C, and55D are detachably disposed around the substrate G placed on the heating plate4. For example, the plates55A,55B,55C, and55D are detachably disposed on the supporting members72shown inFIG. 10B. As an attaching and detaching method, the plates55A,55B,55C, and55D may be secured to the supporting members72with screws. Alternatively, the plates55A,55B,55C, and55D each may have a concave portion (not shown inFIG. 17). The concave portions of the plates55A,55B,55C, and55D may be engaged with the respective supporting members72so as to secure the plates55A to55D to the supporting members72.

Temperature sensors S1, S2, S3, and S4as means for detecting the temperatures in the vicinities of the side surfaces of the substrate G are disposed between the substrate G placed on the heating plate4and the plates55A,55B,55C, and55D, respectively. The temperature sensors S1to S4are disposed in the vicinities of the approximately center positions of the four sides of the substrate G. It should be noted that the number of temperature sensors is not limited to four. Instead, the number of temperature sensors may be eight rather than four. In addition, as the positions of the temperature sensors S1to S4, they may be in contact with the side surfaces Ga, Gb, Gc, and Gd of the substrate G. With the temperature sensors S1to S4in contact with the side surfaces Ga, Gb, Gc, and Gd, temperature information of the substrate G can be more accurately obtained than that structure without them. The detected values of the temperature sensors S1to S4are transferred to a controlling portion200. The plates55A,55B,55C, and55D are connected to the controlling portion200through the foregoing driving mechanism73. The plates55A,55B,55C, and55D are independently movable in approximately horizontal direction to the side surfaces Ga, Gb, Gc, and Gd, respectively, of the substrate G placed on the heating plate4. The heating plate4is designed to heat a semiconductor wafer having a diameter of at least 10 inches.

Next, a controlling method of the positions of the plates55A,55B,55C, and55D in accordance with the temperatures of the substrate G detected by the temperature sensors S1to S4, respectively, will be described. Before the substrate G is heated, the distances between the inner surfaces55ato55dof the plates55A to55D and the side surfaces Ga to Gd of the substrate G are set to distance d (around 5 mm).

First of all, the heating plate4starts heating the substrate G. The temperatures in the vicinities of the side surfaces Ga, Gb, Gc, and Gd of the substrate G are detected by the temperature sensors S1to S4at every predetermined time interval. The predetermined time interval can be set in the range from several seconds to several minutes.

The controlling portion200receives the detected values of the temperature sensors S1to S4at every predetermined time interval. The controlling portion200calculates temperature change amounts of the temperature sensors S1to S4at every predetermined time interval. As a result, the controlling portion200determines whether the temperatures of the side surfaces Ga, Gb, Gc, and Gd of the substrate G are in a temperature constant state, a temperature decreasing state, or a temperature increasing state.

When the temperature of the side surface Ga of the substrate G is in the temperature constant state or the temperature decreasing state, the controlling portion200rotates the ball screw of the driving mechanism73so as to move the plate55A in an arrow direction shown inFIG. 17. As a result, the inner surface55aof the plate55A approaches the side surface Ga of the substrate G. Thus, the distance d1becomes distance d2that is smaller than the distance d1.

In contrast, when the temperature of the side surface Ga of the substrate G is in temperature increasing state, the controlling portion200moves the plate55A in the arrow direction shown inFIG. 17so that the inner surface55aof the plate55A goes away from the side surface Ga of the substrate G. Thus, the distance d2becomes the distance d1.

It is not always necessary to dispose the temperature sensors S1to S4. Alternatively, the controlling portion200may control the driving mechanism73in accordance with the processing temperature at which the substrate G is processed by the heating plate4, namely, the temperature of the heating plate4itself. In this case, since the controlling portion200controls the driving mechanism73in accordance with only the temperature of the heating plate4, the controlling portion200controls the plates55A,55B,55C, and55D with the same control amount rather than independent control amounts.

According to the present embodiment, it can be determined whether the temperatures of the side surfaces Ga, Gb, Gc, and Gd of the substrate G are in the temperature constant state, the temperature decreasing state, or the temperature increasing state. When the temperature of the side surface Ga of the substrate G is in the temperature constant state or the temperature decreasing state, the plate55A can be moved so that the inner surface55aof the plate55A approaches the side surface Ga of the substrate G. In contrast, when the temperature of the side surface Ga of the substrate G is in the temperature increasing state, the plate55A can be moved so that the inner surface55aof the plate55A goes away from the side surface Ga of the substrate G (this applies to the other side surfaces Gb, Gc, and Gd of the substrate G).

Thus, by increasing heat supplied from the plate55A to the substrate G, the temperature of the side surface Ga can be concentratively raised. In contrast, by decreasing heat supplied from the plate55A to the substrate G, the temperature of the side surface Gb can be lowered. As a result, the temperature uniformity of the surface of the substrate G can be improved.

According to the present embodiment, the plates55A,55B,55C, and55D are detachably disposed around the substrate G placed on the heating plate4. In such a structure, even if particles accumulate between the plates55A,55B,55C, and55D and the side surfaces Ga, Gb, Gc, and Gd of the substrate G, by detaching the plates55A,55B,55C, and55D from the heating plate4, the particles can be removed therefrom. Thus, the heat processing unit can be easily maintained. In addition, the substrate G can be prevented from being contaminated with particles.

According to the present embodiment, the temperatures in the vicinities of the side surfaces Ga, Gb, Gc, and Gd of the substrate G are detected by the temperature sensors S1to S4at intervals of every several seconds to every several minutes. When the interval of the detection time is shortened, the temperature change of the substrate G can be quickly detected. Thus, the temperature uniformity of the surface of the substrate G can be improved.

In the foregoing description of the foregoing two embodiments, by suppressing heat radiation from the side surfaces of the substrate, the temperature the surface of the substrate can be secured. Since the amount of heat radiated from each of side surfaces of a substrate having a large thickness is large, those embodiments are especially effective for a heat process for a substrate having a thickness of for example 3 mm or more.

In addition, according to the foregoing embodiment, it is not always necessary to cause the frame member5(5A to5E) to surround all the periphery of a substrate, but part thereof. Alternatively, the frame member5(5A to5E) may have an area that does not surround the substrate. In addition, it is not always necessary to form the frame member5(5A to5E) in a ring shape. In other words, the frame member5(5A to5E) may be separated members. As shown inFIG. 18A, a frame member5F may be formed in a sharp “#” shape. Alternatively, as shown inFIG. 18B, a frame member5G may be formed in a tray shape of which a substrate G is held in the frame member5G. A part of the bottom of the frame member5G may be cut so as to form a clearance50. In addition, as shown inFIG. 18C, a heating plate40may have a protruded surface or an inclined surface on which a substrate is placed.

According to the present invention, as long as the heat processing unit performs the predetermined heat process, the heat processing unit is not limited to the foregoing structures. In other words, the heat processing unit may have a chamber type structure as well as the structure using the shutter that opens and closes the wafer loading opening. In addition, the present invention can be applied to not only a heat process for a substrate on which a resist solution has been coated, but heat processes such as a heat and dry process performed after a substrate has been washed, a post-exposure bake process performed after a wafer has been exposed, and a post-bake process performed after a substrate has been developed. The foregoing embodiment describes an apparatus that processes a square type substrate for use with a semiconductor mask. In addition, the present invention can be applied to an apparatus that processes a substrate for a flat panel display (FPD) for example a circular substrate or the like that has a large thickness and that is processed for a special purpose.

InFIG. 17, an example of which the plates55A,55B,55C, and55D are detachably disposed on the heating plate4was described. However, not only the embodiment shown inFIG. 17, but at least one example of the embodiment shown inFIG. 3toFIG. 13may have a structure of which the frame member is detachably disposed on the heating plate4.

The disclosure of Japanese Patent Application No. 2003-032603 filed Feb. 10, 2003 including Specification, Drawings and Claims are herein incorporated by reference in its entirety.