JP3806660B2 - Vacuum drying apparatus and vacuum drying method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a reduced-pressure drying apparatus and a reduced-pressure drying method for drying, for example, an interlayer insulating film, a substrate coated with a coating liquid for a protective film of a device, a resist liquid, or the like on a surface, and drying the coating liquid.
[0002]
[Prior art]
As one of the semiconductor manufacturing processes, there is a process of forming a coating film by applying a predetermined coating solution on a substrate such as a semiconductor wafer in order to form an interlayer insulating film or a protective film of a semiconductor device. This treatment is performed, for example, by applying a coating solution containing polyimide and a solvent to the substrate surface and evaporating the solvent to form a coating film made of a polyimide component.
[0003]
As the solvent contained in the coating solution, a low-volatility solvent such as a high-boiling thinner is used. Therefore, after the coating solution is applied to the wafer, it is subjected to a vacuum drying treatment in a vacuum drying unit for drying in a short time. It is a good idea. As shown in FIG. 15, for example, the conventional vacuum drying unit is provided with a hermetic container 1 including a lid 11 and a placement unit 12. In addition, an exhaust port 13 is provided in the ceiling portion of the lid 11 and a vacuum pump 15 is connected through an exhaust path such as a pipe 14 so that the inside of the sealed container 1 can be decompressed. . Further, a rectifying plate 16 is provided in the sealed container 1 so as to be movable up and down so that the evaporation component from the coating liquid forms a uniform exhaust flow on the surface of the wafer W.
[0004]
In such a vacuum drying unit, the wafer W that has been subjected to the above-described coating process is first placed on the placement unit 12, and the rectifying plate 16 is set at a predetermined height position so as to face the wafer W. Next, the temperature of the wafer W is adjusted to, for example, 30 ° C. by a temperature adjusting means (not shown) provided in the mounting portion 12 and the vacuum pump 15 is operated to depressurize the hermetic container 1, so that the current plate 16 and the wafer are reduced. The solvent in the coating solution evaporates (drys) while forming an exhaust flow that spreads outward with W, and a coating film is formed on the surface of the wafer W by the remaining polyimide component.
[0005]
[Problems to be solved by the invention]
By the way, in the case of the above-mentioned reduced-pressure drying method, the liquid film of the coating liquid in the region extending, for example, 5 mm inward from the peripheral edge of the wafer W, for example, from the peripheral edge of the substrate before the vacuum drying treatment is applied to the surface of the wafer W. Due to the effect of surface tension with the condensing force of the liquid, the corners are rounded as shown in FIG. When the coating liquid in such a state is dried under reduced pressure, the solvent evaporates from the surface on the side peripheral side in addition to the upper side in the coating liquid at the peripheral portion. That is, the evaporation of the solvent in the peripheral portion of the coating solution having a larger evaporation surface area than that in the inner region is performed more actively than the coating solution in the inner region. Here, when the solvent evaporates from the coating solution, the coating solution on the surface of the wafer W is deprived of the heat of vaporization by the evaporating solvent, the liquid temperature on the surface of the coating solution is lowered, and the surface tension is increased. Since the difference in evaporation amount due to the evaporation surface area and the difference in surface tension generated between the peripheral portion and the inner region are combined, the coating liquid is drawn to the peripheral portion side, so that FIG. As shown, there is a concern that a coating film having a raised peripheral edge may be formed.
[0006]
The present invention has been made on the basis of such circumstances, and an object of the present invention is to suppress an increase in the surface tension of the peripheral portion in a vacuum drying apparatus for drying a substrate coated with a coating liquid on the surface in a vacuum state. Another object of the present invention is to provide a technique capable of performing vacuum drying treatment with high in-plane uniformity.
[0007]
[Means for Solving the Problems]
The reduced-pressure drying apparatus of the present invention is a reduced-pressure drying apparatus for drying a substrate coated with a coating liquid on the surface in a reduced pressure state.
An airtight container in which a substrate placement portion for placing a substrate is provided;
Opposite the surface of the substrate placed on the substrate placement portion through a gap, provided to exhaust the gas in the gap toward the outside, the size is approximately the same as or larger than the substrate A current plate,
A first heating unit provided on each of the current plates and provided in a region facing the peripheral edge of the substrate, and provided inside the first heating unit and surrounded by the first heating unit. A second heating unit,
A substrate temperature adjusting means provided on the substrate mounting portion for adjusting the temperature of the substrate;
A vacuum exhaust means for decompressing the inside of the airtight container,
The second heating unit is set to a temperature lower than that of the first heating unit .
[0008]
Further, on the lower surface of the rectifying plate, for example, a heat equalizing plate may be provided for continuously changing the temperature from the first heating unit corresponding to the heat insulating unit to the second heating unit. Furthermore, the peripheral edge of the substrate may be a region extending from 5 to 15 mm inward from the outer peripheral edge of the substrate, for example.
[0009]
According to the present invention, it is possible to form a coating film while suppressing a decrease in the temperature of the peripheral edge that occurs during evaporation of the solvent during drying under reduced pressure. That is, since the increase in the surface tension at the peripheral edge of the substrate can be suppressed, the coating solution is not drawn toward the peripheral edge, and a reduced-pressure drying process is performed to form a coating film having a uniform thickness. That is, a vacuum drying process with high in-plane uniformity can be performed.
[0010]
The reduced-pressure drying apparatus of the present invention is a reduced-pressure drying apparatus for drying a substrate coated with a coating liquid on the surface in a reduced pressure state.
An airtight container in which a substrate placement portion for placing a substrate is provided;
A ventilation resistor that is opposed to the surface of the substrate placed on the substrate placement unit via a gap, and the air permeability of the region facing the peripheral edge of the substrate is smaller than the air permeability of the region inside the region; and
A rectifying plate provided opposite to the ventilation resistor via a gap so as to exhaust the gas containing the evaporation component from the coating solution that has passed through the ventilation resistor toward the outer side thereof,
A substrate temperature adjusting means provided on the substrate mounting portion for adjusting the temperature of the substrate;
And a reduced pressure exhaust means for reducing the pressure in the airtight container.
[0011]
The separation distance between the substrate placed on the substrate placement portion and the ventilation resistor may be set to 0.5 mm, for example, and the separation distance between the ventilation resistor and the current plate is, for example, 0.5 mm. You may make it set to. Furthermore, the peripheral edge portion of the substrate may be, for example, a region extending from 10 mm ± 5 mm inward from the outer peripheral edge of the substrate.
[0012]
According to the present invention, since a part of the evaporation component collides with the ventilation resistor provided to face the peripheral area of the substrate and returns to the surface side of the coating liquid, the coating liquid in the peripheral area It is difficult for the solvent component evaporated from the above to escape upward. For this reason, the evaporation amount of the solvent component is suppressed, and the difference in evaporation state between the peripheral edge portion and the inner region is reduced. As a result, variation in the surface tension of the coating solution in the plane of the substrate can be suppressed, so that the coating solution is not attracted to the peripheral edge side, and a reduced-pressure drying process is performed to form a coating film having a uniform thickness. That is, a vacuum drying process with high in-plane uniformity can be performed.
[0013]
The reduced-pressure drying method of the present invention is a reduced-pressure drying method for drying a substrate having a coating solution coated on the surface under reduced pressure,
Placing the substrate on a substrate placement portion provided in an airtight container; and
Next, a step of positioning a rectifying plate having a size substantially equal to or larger than that of the substrate so as to face the surface of the substrate placed on the substrate placement unit via a gap,
In the rectifying plate, the set temperature of the first heating unit provided in the region facing the peripheral edge of the substrate is provided inside the first heating unit and surrounded by the first heating unit. A step of making the temperature higher than the set temperature of the obtained second heating unit;
A step of evacuating the gas in the gap toward the outside of the rectifying plate by decompressing the inside of the hermetic container, and evaporating the solvent component contained in the coating liquid.
[0014]
Moreover, the reduced-pressure drying method of the present invention is a reduced-pressure drying method for drying a substrate having a coating solution coated on the surface under reduced pressure,
Placing the substrate on a substrate placement portion provided in an airtight container; and
A ventilation resistor that faces the surface of the substrate placed on the substrate placement part through a gap and that the air permeability of the region facing the peripheral edge of the substrate is smaller than the air permeability of the region inside the region. A step of positioning
A step of positioning the rectifying plate on the upper side of the ventilation resistor so as to face the ventilation resistor via a gap;
By depressurizing the inside of the airtight container, the vaporized component from the coating liquid at the peripheral edge of the substrate is allowed to pass through the ventilation resistor, and the gas in the gap between the ventilation resistor and the rectifying plate is exhausted toward the outside of the rectifying plate. And evaporating the solvent component contained in the coating liquid.
DETAILED DESCRIPTION OF THE INVENTION
First, before describing the vacuum drying apparatus of the present invention, an example of a coating film forming apparatus in which the vacuum drying apparatus is incorporated will be described with reference to FIGS. In the figure, reference numeral 21 denotes a cassette station, for example, a delivery for transferring the wafer W between the cassette placement part 22 for placing a cassette C containing 25 wafers W and the placed cassette C. Means 23 are provided. A processing unit S1 surrounded by a casing 24 is connected to the back side of the delivery means 23. A main conveying means 25 is provided at the center of the processing unit S1, and a plurality of coating units 3 are provided on the right side, for example, as viewed from the back so as to surround this, and a heating / cooling system is provided on the left side, near side, and back side. Shelf units U1, U2, and U3 are stacked in multiple stages.
[0015]
The shelf units U1, U2, and U3 are configured by combining various units for performing pre-processing and post-processing of the coating unit 3, and the coating liquid is applied to the surface by the coating unit 3. The wafer W is dried under a reduced pressure atmosphere, and a reduced pressure drying unit that is a reduced pressure drying apparatus that volatilizes the solvent contained in the coating solution, a heating unit that heats (bakes) the wafer W, a cooling unit that cools the wafer W, etc. Is included. As for the shelf unit U3, a delivery unit including a delivery table for delivering the wafer W is also incorporated. The main transfer means 25 described above is configured to be movable up and down and back and forth and to rotate around the vertical axis, for example, and between the units constituting the coating unit 3 and the shelf units U1, U2, and U3, the wafer W It is possible to deliver.
[0016]
The flow of the wafer W of this apparatus will be described. First, the cassette C in which the wafer W is stored from the outside is placed on the cassette placing portion 22, and the wafer W is taken out from the cassette C by the transfer means 23, and heated / cooled. It is delivered to the main transport means 25 via a delivery unit that is one of the shelves of the unit U3. Next, after the hydrophobic treatment is performed in the processing section of one shelf of the unit U3, the coating liquid is applied by the coating unit 3. Thereafter, the wafer W is transferred to a vacuum drying unit, and a coating film is formed by a vacuum drying process. The wafer W on which the coating film is formed is heated by the heating unit and then cooled to a predetermined temperature by the cooling unit. Thereafter, the wafer W is returned into the cassette C on the cassette mounting portion 22.
[0017]
Here, in the above-described coating unit 3 in the preceding stage of the reduced pressure drying method according to the present invention, for example, a coating liquid i formed by mixing a polyimide component that forms a coating film after drying and a solvent such as high boiling thinner is applied to the surface of the wafer W. An example of a coating method for coating will be briefly described with reference to FIG. The coating method is a so-called spiral type coating method. In the substrate processing space of the coating unit 3, when the wafer W held horizontally by the substrate holding unit 31 is rotated in the circumferential direction, the surface of the wafer W is coated. The coating liquid i is linearly supplied while moving at a predetermined speed in the radial direction (X direction in the figure) of the wafer W, which is set to face the center and for supplying the coating liquid i. To do. In this manner, the coating liquid i is applied to the wafer W in the manner of a so-called spiral stroke.
[0018]
Next, an embodiment of the reduced pressure drying apparatus according to the present invention will be described. As shown in FIG. 4, the reduced pressure drying apparatus includes a mounting table 4 that is a substrate mounting unit for mounting, for example, an 8-inch wafer W coated with the coating liquid i. The mounting table 4 is embedded with a substrate temperature adjusting means 41 for adjusting the temperature of the mounted wafer W, for example, a heating part made of a resistance heating element. The mounting table 4 and the substrate temperature adjusting means 41 A temperature control plate is configured. More specifically, the substrate holding protrusion 42 is located at a position corresponding to the peripheral edge on the back surface side of the wafer W so that the wafer W is placed with a slight gap from the surface of the mounting table 4, for example, about 0.1 mm. Is provided. Further, when the wafer W is carried into and out of the mounting table 4, the substrate support pins 43 penetrate the mounting table 4 in the vertical direction so as to move up and down while supporting the back surface of the wafer W from below and project by the lifting mechanism 44. The wafer W is configured to be freely sunk, and is configured such that the wafer W is mounted on the mounting table 4 by the cooperative action of the main transfer means 25 and the substrate support pins 43. In the drawing, reference numeral 45 denotes a bellows for preventing the decompressed state in the airtight container 40 from being broken through the through hole of the substrate support pin 43.
[0019]
On the upper side of the mounting table 4, a lid 5 is provided so as to be movable up and down by a lid lifting mechanism (not shown). The lid 5 rises when the wafer W is carried in and out, and descends when drying under reduced pressure, and the lid 5 and the mounting table 4 form an airtight container 40. Further, an exhaust port 51 is provided near the center of the ceiling of the lid 5, and the exhaust port 51 is connected to a vacuum pump 53, which is a decompression exhaust unit, via an exhaust path, for example, a pipe 52. A valve 54 and a pressure adjusting unit 55 in the airtight container 40 are provided.
[0020]
Further, on the upper side of the mounting table 4, for example, the temperature adjusting unit is included so as to face the surface of the wafer W mounted on the mounting table 4. A circular rectifying plate 6 having a thickness of 5 mm is provided. Here, the term “substantially the same size as the wafer W” refers to, for example, a size that covers the device formation region of the wafer W but is slightly smaller than the wafer W. As shown in FIG. 5 in detail, the first heating unit 61, for example, the ring is provided so as to face at least a peripheral part of the wafer W, for example, an area extending from the outer peripheral edge of the wafer W to the inner side, for example, 10 mm wide. A planar surface heater is provided. Further, a second heating unit 62, for example, a circular planar heater is provided inside the first heating unit 61 so that the outer peripheral edge thereof is surrounded by the first heating unit 61. Here, each planar heater is configured as a sandwich structure in which a resistance heating element formed in the above shape is sandwiched from above and below by an aluminum plate.
[0021]
Further, between the inner periphery of the first heating unit 61 and the outer periphery of the second heating unit 62, for example, a ring-shaped heat insulating member 63 having a width of 5 mm is provided, and the outer periphery of the first heating unit 61. For example, a ring-shaped heat insulating member 64 having a width of 5 mm is provided. Here, for example, glass wool is used for the heat insulating members 63 and 64. Furthermore, on the lower surface of the rectifying plate 6, a soaking plate 65, for example, an aluminum foil having a thickness of 0.1 mm, is coated for soaking the temperature of the region heated by each heating unit in-plane. Furthermore, an exterior plate 66 is provided on the upper surface side of the rectifying plate 6.
[0022]
Returning to FIG. 4, the rectifying plate 6 is supported by support members 67 at, for example, three places on the exterior plate 66. These support members 67 pass through the lid 5, and one of the support members 67 a is connected to the lifting / lowering means 68 using a ball screw mechanism, and the remaining support members 67 are positioned so that the rectifying plate 6 is not displaced from side to side. It serves as a guide bar for alignment. The rectifying plate 6 is moved up and down by the lifting and lowering means 68 and can be adjusted to a predetermined height position with high accuracy.
[0023]
Further, reference numeral 7 in the figure denotes a control unit, and when the control unit 7 performs the drying process of the wafer W under reduced pressure, the first heating unit 61 and the second heating unit 62 are brought to a predetermined temperature in a sequence as will be described later. Each has a function of controlling, and a function of controlling the elevating means 68 and the pressure adjusting unit 55, respectively.
[0024]
The process of performing vacuum drying using such a vacuum drying apparatus will be described with reference to FIGS. As shown in FIG. 6, first, at time t <b> 1, with the lid 5 raised, the wafer W coated with the coating liquid i by the above-described method is loaded by the main transfer means 25, and further the substrate support pins 43. Is placed on the mounting table 4 by the cooperative action. Next, the lid 5 is lowered to form an airtight container 40 surrounding the periphery of the wafer W. Subsequently, the rectifying plate 6 is lowered, and the lower surface of the rectifying plate 6 is set to a height position L1 that is 2 mm away from the surface of the wafer W, for example. Further, the wafer W is heated from the back surface side by the substrate temperature adjusting means 41 and set to a predetermined temperature, for example, a temperature higher than 23 ° C. which is a set temperature of the clean room, for example, 30 ° C. Next, when the valve 52 is opened and vacuum exhausting is started by the vacuum pump 53, the heating operation of the first heating unit 61 and the second heating unit 62 is performed, and the first heating unit 61 is, for example, 90 ° C. In addition, the second heating unit 62 is set to 30 ° C., for example. At this time, the pressure P in the airtight container 40 rapidly decreases from the atmospheric pressure atmosphere P0.
[0025]
Thereafter, for example, at time t2 30 seconds after time t1, the pressure in the hermetic container 40 becomes P1, and the solvent in the coating liquid i on the surface of the wafer W starts to violently evaporate. An exhaust flow that flows from the center side toward the outer side through a slight gap with the rectifying plate 6 is formed. Here, in order to prevent the solvent from boiling and roughening the surface of the coating film, the pressure P in the hermetic container 40 is adjusted by the pressure adjusting unit 55 and gradually decreases near the vapor pressure of the solvent.
[0026]
FIG. 7 shows the temperature of the coating liquid i and the surface of the rectifying plate 6 when the solvent is violently evaporated as described above. FIG. 7A is a longitudinal sectional view of the wafer W and the rectifying plate 6, and temperature distribution diagrams showing temperatures at positions corresponding to the sectional view are FIGS. 7B and 7C, respectively. The solid line indicates the temperature of the coating liquid i, and the one-dot oblique line indicates the temperature of the surface of the rectifying plate 6. First, as shown in FIG. 7B, in the rectifying plate 6 during the heating operation, the heat of the first heating unit 61 and the second heating unit 62 is transferred to the adjacent soaking plates 65, and each The heating parts 61 and 63 are soaked. The surface of the soaking plate 65 has a peripheral portion that is a region formed by the first heating unit 61 at 90 ° C., and a region that is inside the peripheral portion that is a region that is formed by the second heating unit 62 is 30. It becomes ℃. Here, since the first heating unit 61 and the second heating unit 62 are thermally separated by the heat insulating member 63, it is possible to suppress the mutual interference by the temperature control, and the portion corresponding to the heat insulating member 63. As for the temperature of the soaking plate 65, a temperature gradient is formed over the temperature of the peripheral portion and the temperature of the inner region.
[0027]
The coating liquid i on the wafer W is heated by receiving radiant heat from the rectifying plate 6 in which such a temperature distribution is formed, and the coating liquid i at the peripheral part receives radiant heat from the first heating unit 61 and is, for example, 35 to 35. The region inside the peripheral edge at 40 ° C. receives the radiant heat of the second heating unit 62 and becomes 27 ° C. to 30 ° C., for example. Then, as the solvent evaporates, the surface temperature of the rectifying plate 6 decreases due to heat dissipation, and the coating liquid i is deprived of heat of vaporization and the liquid temperature decreases, and the liquid temperature at the peripheral edge where evaporation is active is in the center. Will fall faster than.
[0028]
Thus, for example, at time t4 when the solvent evaporates and most of the solvent is completely evaporated, as shown in FIG. 7C, the temperature of the peripheral edge of the rectifying plate 6 is 35 to 40 ° C. 6 is 25 ° C., the region inside the peripheral edge of the coating liquid i is, for example, 25 ° C., and the peripheral edge of the coating liquid i is the same as the inner area. A slightly lower temperature, for example 25 ° C. After that, when a coating film made of a polyimide component contained in the coating liquid i is formed on the surface of the wafer W, the evaporated solvent atmosphere and air remaining in the hermetic container 40 are exhausted, and the pressure in the hermetic container 40 is again increased from P2. When the pressure decreases rapidly and reaches a predetermined pressure P3 at time t4, the valve 52 is closed and the reduced pressure exhaust is stopped. Thereafter, an inert gas such as nitrogen is supplied to the hermetic container 40 by an air supply means (not shown). At time t5, the pressure P of the hermetic container 40 is returned to the atmospheric atmosphere P0, and the wafer W is unloaded. Then, the vacuum drying process is completed.
[0029]
In such an embodiment, the coating liquid i on the surface of the wafer W is heated by the radiant heat of the rectifying plate 6 in which the temperature of the peripheral portion is high and the temperature of the inner region is set low. That is, the coating liquid i at the peripheral portion is set to a high temperature in advance so as to meet the liquid temperature difference caused by the difference in the evaporation state of the solvent in the inner region. Even in such a case, the peripheral portion having a large evaporation area is more actively evaporated than the inner region, and the temperature of the coating liquid is lowered by the heat of vaporization. However, since the liquid temperature at the peripheral portion is set to be high in advance, the coating film is not formed while increasing the temperature difference between the peripheral portion and the inner region as in the prior art. The coating film can be formed while reducing the liquid temperature difference between the portion and the central portion. For this reason, the surface tension of the coating liquid i is uniform between the peripheral portion and the inner region, and the coating liquid i at the peripheral portion does not attract the liquid inside, or even if it is attracted, the degree is small. A coating film can be formed. As a result, a coating film with high uniformity in film thickness can be formed.
[0030]
Further, in this embodiment, as described above, the configuration is not limited to heating from the upper side of the wafer W by radiant heat. For example, the first heating unit 61 and the second heating unit 61 are added to the substrate temperature adjusting unit 41 as shown in FIG. It is good also as a structure which assigned the role of the heating part 62. FIG. Even in this case, the coating liquid is heated through the wafer W, the temperature of the peripheral portion can be made higher than the temperature inside thereof, and the same effect as in the above case can be obtained.
[0031]
Next, another embodiment of the vacuum drying apparatus of the present invention will be described with reference to FIG. Note that other configurations of the vacuum drying apparatus that are the same as those in the above-described embodiment are denoted by the same reference numerals in the drawing and description thereof is omitted. The reduced-pressure drying apparatus of this embodiment is a circular ventilation resistor having a thickness approximately the same as or larger than that of the wafer W that can pass the solvent component evaporated from the coating solution to the back side thereof, for example, 10 mm. 8 is provided so that it can be moved up and down by the lifting means 82 while being supported by the support member 81 so as to face the surface of the wafer W mounted on the mounting table, and is controlled by the control unit 7. . Here, a material selected from ceramics, for example, is used for the ventilation resistor 8. On the upper side of the ventilation resistor 8, for example, a circular rectifying plate 9 having a size equal to or larger than that of the wafer W, for example, a thickness of 3 mm, is provided so as to be lifted and lowered by a lifting and lowering means 68.
[0032]
The ventilation resistor 8 includes a ring-shaped first ventilation resistor 83 so as to face at least a peripheral portion of the wafer W, for example, a region extending from the outer peripheral edge of the wafer W toward the inside thereof, for example, a width of 10 mm. . Inside the first ventilation resistor 83, another ventilation resistor, for example, a circular second ventilation resistor 84 is provided so that the outer peripheral edge thereof is surrounded by the first ventilation resistor 83. Yes. Here, for the first ventilation resistor 83 and the second ventilation resistor 84, for example, the first ventilation resistor 83 is less air permeable than the second ventilation resistor 84 using members having different porosity. Configured as follows.
[0033]
In this case, as shown in FIG. 10, the ventilation resistor 8 is first set at a distance L2 from the surface of the wafer W, for example, at a height of 0.5 mm, and then the rectifying plate 9 is separated from the upper surface of the ventilation resistor 8. The distance L3 is set to a height position of 0.5 mm, for example, and the vacuum drying process is performed.
[0034]
In this embodiment, the solvent component evaporated from the coating solution at the peripheral edge of the wafer W collides with the ventilation resistor and is returned to the surface side of the coating solution. Is smaller than the area. For this reason, in the peripheral area, the amount of evaporation from the surface of the coating liquid i upward is suppressed compared to the inner area, and the difference in evaporation state between the peripheral area and the inner area is reduced. As a result, the variation in surface tension in the plane of the wafer W is suppressed and the reduced-pressure drying process is performed, so that the phenomenon that the coating film on the peripheral edge rises is alleviated and the in-plane uniformity of the film thickness is increased. Although the separation distances L2 and L3 are 0.5 mm, in order to make the invention easy to understand, they are written wider than actual in FIG.
[0035]
Further, in this embodiment, the ventilation resistance of the second ventilation resistor 64 is made zero without being limited to the configuration in which the ventilation resistor 8 including the first ventilation resistor 83 and the second ventilation resistor 84 is provided. The configuration may be such that the ventilation resistance of the first ventilation resistor 63 is infinite, and in this case as well, the air permeability in the region facing the peripheral edge of the substrate (wafer W) is higher than the air permeability inside the region. It is equivalent to small. For example, as shown in FIG. 11A, a ring-shaped ventilation resistor 8 including only the first ventilation resistor 63 is provided, so that the ventilation resistance of the second ventilation resistor 64 is reduced to zero. Alternatively, a baffle plate 85 having the same shape as the first ventilation resistor 83, that is, an infinite ventilation resistance, may be provided as shown in FIG. 11 (b). Even in such a configuration, the concentration gradient of the solvent component from the surface of the coating liquid i in the peripheral area to the upper side becomes gentle, and the difference in evaporation state from the inner area of the peripheral area becomes small. The same effect can be obtained.
[0036]
Furthermore, in this embodiment, the separation distances L2 and L3 are not limited to 0.5 mm, and may be set within a range of 0.5 to 30 mm. Here, how to set the separation distances L2 and L3 is preferably determined by conducting an experiment in advance according to the component of the coating liquid i to be used.
[0037]
As another embodiment of the present invention, for example, a coating liquid having a predetermined liquid temperature is applied in the coating unit 3, and the liquid temperature of the coating liquid on the wafer W carried into the reduced-pressure drying apparatus is determined by the substrate temperature adjusting means 41. For example, the temperature may be set to be 3 to 5 ° C lower than the set temperature, for example, 25 to 27 ° C.
[0038]
In this case, as shown in FIG. 12A, the heating operation of the substrate temperature adjusting means 41 is performed before the wafer W is loaded, and the temperature adjusting plate constituted by the mounting table 4 and the substrate temperature adjusting means 41 is provided. The temperature is adjusted in advance to the set temperature, for example, 30 ° C., and then the wafer W is loaded and a reduced-pressure drying process is performed.
[0039]
In this embodiment, as shown in FIG. 12B, the coating liquid applied to the loaded wafer W is heated through the wafer W from the temperature control plate substantially uniformly in the plane. However, since the edge of the coating liquid is rounded due to the surface tension and the amount of the liquid is small, the temperature rises to a higher temperature than the coating liquid in the inner region. In this way, vacuum drying is performed in a state where the liquid temperature difference between the peripheral edge and the inner area is formed, and the liquid temperature difference between the peripheral edge where evaporation is active and the inner area where evaporation is not active is reduced during vacuum drying. However, since the coating film can be formed, the same effects as those described above can be obtained.
[0040]
Furthermore, in the present invention, the temperature of the wafer W may be set lower than, for example, the temperature of a clean room in which the reduced pressure drying apparatus is provided. In this case, the current plate is thermally cooled, but even in such a case, the surface tension of the coating liquid i can be made uniform in the surface, so that the coating film having a uniform film thickness can be obtained. Can be obtained.
[0041]
Furthermore, the present invention can be applied to a substrate other than a semiconductor wafer as a substrate to be processed, such as an LCD substrate or a reticle substrate for a photomask, and a resist other than an interlayer insulating film or a device protective film. It can also be applied to film formation.
[0042]
【Example】
Next, examples performed to confirm the effects of the present invention will be described.
Example 1
This example is Example 1 in which the vacuum drying process was performed on the wafer W coated with the coating liquid using the vacuum drying apparatus according to the first embodiment. First, a coating solution containing polyimide and a high boiling thinner was applied to the surface of an 8-inch size (diameter 200 mm) wafer W by the coating method shown in FIG. Next, the wafer W is carried into a vacuum drying apparatus, the lid body 5 is lowered to form the airtight container 40, and then the wafer W is heated to 23 ° C. by the substrate temperature adjusting means 41, and the current plate 6 Was set at a height position where the gap with the surface of the wafer W was 10 mm. Subsequently, the first heating unit 61 was set to 100 ° C., the second heating unit 62 was set to 23 ° C., and the vacuum pump was operated to perform a reduced pressure drying process.
[0043]
(Example 2)
This example is Example 2 when the first heating unit 61 is set to a different set temperature from that of Example 1. Here, the first heating unit 61 was set to 70 ° C., and the others were subjected to reduced-pressure drying treatment in the same manner as in Example 1.
[0044]
Example 3
This example is Example 3 when the first heating unit 61 is set to a different set temperature from Example 1 and Example 2. Here, the first heating unit 61 was set to 50 ° C., and the others were subjected to reduced-pressure drying treatment as in Example 1.
[0045]
(Comparative Example 1)
This example is Comparative Example 1 when the first heating unit 61 and the second heating unit 62 are not heated. The same treatment as in Example 1 was performed except that the heating was not performed.
[0046]
(Consideration of Example 1 and Comparative Example 1)
The state of the film thickness of the coating film formed in Example 1 and Comparative Example 1 is shown in FIG. As is clear from this result, the coating film formed in Example 1 has less swelling of the coating film in the peripheral portion than Comparative Example 1 in which heating was not performed. That is, it was confirmed that by performing the heating operation of the rectifying plate 6, the difference in the surface tension of the coating liquid between the peripheral edge portion and the inner region thereof was alleviated, and the reduced-pressure drying treatment could be performed.
[0047]
(Consideration of Example 1, Example 2 and Example 3)
The state of the film thickness of the coating film formed by Example 1, Example 2, and Example 3 is shown in FIG. As is clear from this result, the rising of the peripheral edge of the coating film to be formed is relaxed as the set temperature of the first heating unit 61 increases, and it is confirmed that the more preferable set temperature is 70 to 100 ° C. It was. In the present invention, the set temperature may be set higher than 100 ° C., but is preferably set to 100 ° C. or less for the reason that the film thickness at the peripheral edge can be reduced.
[0048]
【The invention's effect】
As described above, according to the present invention, in the reduced pressure drying apparatus for drying the substrate coated with the coating liquid on the surface in a reduced pressure state, the surface tension of the coating liquid during drying is made uniform, and the in-plane uniformity is improved. High vacuum drying treatment can be performed.
[Brief description of the drawings]
FIG. 1 is a perspective view showing an example of a coating apparatus incorporating a vacuum drying apparatus according to the present invention.
FIG. 2 is a plan view showing an example of a coating apparatus incorporating a reduced-pressure drying apparatus according to the present invention.
FIG. 3 is an explanatory diagram showing a state in which a liquid film of a coating liquid to be subjected to a vacuum drying process is formed.
FIG. 4 is a longitudinal sectional view showing a vacuum drying apparatus according to the first embodiment of the present invention.
FIG. 5 is a perspective view showing a current plate used in the vacuum drying apparatus according to the first embodiment.
FIG. 6 is a process diagram showing a reduced-pressure drying process of the reduced-pressure drying apparatus according to the first embodiment.
FIG. 7 is an explanatory diagram for explaining a temperature distribution during reduced-pressure drying of the reduced-pressure drying apparatus according to the first embodiment.
FIG. 8 is an explanatory diagram illustrating another temperature adjustment unit according to the first embodiment.
FIG. 9 is a longitudinal sectional view showing a vacuum drying apparatus according to a second embodiment of the present invention.
FIG. 10 is an explanatory diagram showing a state of a coating film when dried under reduced pressure using the reduced pressure drying apparatus according to the second embodiment.
FIG. 11 is an explanatory diagram showing a state of a coating film when dried under reduced pressure using another ventilation resistor according to the second embodiment.
FIG. 12 is an explanatory diagram showing a vacuum drying method according to a third embodiment.
FIG. 13 is a characteristic diagram showing an example performed for confirming the effect of the present invention.
FIG. 14 is a characteristic diagram showing an example carried out to confirm the effect of the present invention.
FIG. 15 is an explanatory view showing a conventional vacuum drying apparatus.
FIG. 16 is an explanatory diagram showing a state of a coating film when a conventional vacuum drying apparatus is used.
[Explanation of symbols]
W Wafer 4 Mounting table 40 Airtight container 41 Substrate temperature adjusting means 5 Lid 51 Exhaust port 53 Vacuum pump 6 Current plate 61 First heating part 62 Second heating part 63 Heating member 68 Lifting means 7 Control part 8 Ventilation resistor 83 1st ventilation resistor 84 2nd ventilation resistor 9 Current plate

Claims (11)

In a vacuum drying apparatus for drying a substrate coated with a coating liquid on the surface in a vacuum state,
An airtight container in which a substrate placement portion for placing a substrate is provided;
Opposite the surface of the substrate placed on the substrate placement portion through a gap, provided to exhaust the gas in the gap toward the outside, the size is approximately the same as or larger than the substrate A current plate,
A first heating unit provided on each of the current plates and provided in a region facing the peripheral edge of the substrate, and provided inside the first heating unit and surrounded by the first heating unit. A second heating unit,
A substrate temperature adjusting means provided on the substrate mounting portion for adjusting the temperature of the substrate;
A vacuum exhaust means for decompressing the inside of the airtight container,
The reduced-pressure drying apparatus, wherein the second heating unit is set to a temperature lower than that of the first heating unit . Vacuum drying apparatus according to claim 1, wherein a heat insulating member is provided between the first heating portion and the second heating portion. The reduced-pressure drying apparatus according to claim 1 or 2 , wherein a soaking plate for continuously changing the temperature change of the heat insulating portion is provided on the lower surface of the rectifying plate. In a vacuum drying apparatus for drying a substrate coated with a coating liquid on the surface in a vacuum state,
An airtight container in which a substrate placement portion for placing a substrate is provided;
A ventilation resistor that is opposed to the surface of the substrate placed on the substrate placement unit via a gap, and the air permeability of the region facing the peripheral edge of the substrate is smaller than the air permeability of the region inside the region; and
A rectifying plate provided opposite to the ventilation resistor via a gap so as to exhaust the gas containing the evaporation component from the coating solution that has passed through the ventilation resistor toward the outer side thereof,
A substrate temperature adjusting means provided on the substrate mounting portion for adjusting the temperature of the substrate;
A vacuum drying apparatus comprising: a vacuum exhaust means for decompressing the inside of the airtight container. The reduced pressure drying apparatus according to claim 4, wherein the ventilation resistor is made of ceramics having a gap. The vacuum drying apparatus according to claim 4 or 5, wherein a separation distance between the substrate placed on the substrate placement unit and the ventilation resistor is set to 0.5 to 30 mm. The reduced-pressure drying apparatus according to any one of claims 4 to 6, wherein a separation distance between the ventilation resistor and the current plate is set to 0.5 to 10 mm. The reduced pressure drying apparatus according to any one of claims 4 to 7, wherein the ventilation resistor is provided in a ring shape only in a region corresponding to a peripheral portion of the substrate. The reduced-pressure drying apparatus according to any one of claims 1 to 8, wherein the peripheral portion of the substrate is a region extending from 5 to 15 mm inward from the outer peripheral edge of the substrate. In a vacuum drying method for vacuum drying a substrate having a coating liquid applied to the surface,
Placing the substrate on a substrate placement portion provided in an airtight container; and
Next, a step of positioning a rectifying plate having a size substantially equal to or larger than that of the substrate so as to face the surface of the substrate placed on the substrate placement unit via a gap,
Adjusting the temperature of the substrate placed on the substrate placement unit to a predetermined temperature;
In the rectifying plate, the set temperature of the first heating unit provided in the region facing the peripheral edge of the substrate is provided inside the first heating unit and surrounded by the first heating unit. A step of making the temperature higher than the set temperature of the second heating unit
A vacuum drying method comprising: a step of exhausting the gas in the gap toward the outside of the rectifying plate by depressurizing the inside of the hermetic container, and evaporating a solvent component contained in the coating liquid. In a vacuum drying method for vacuum drying a substrate having a coating liquid applied to the surface,
Placing the substrate on a substrate placement portion provided in an airtight container; and
A ventilation resistor that faces the surface of the substrate placed on the substrate placement part through a gap and that the air permeability of the region facing the peripheral edge of the substrate is smaller than the air permeability of the region inside the region. A step of positioning
A step of positioning the rectifying plate on the upper side of the ventilation resistor so as to face the ventilation resistor via a gap;
By reducing the pressure inside the hermetic container, the vaporized component from the coating liquid at the peripheral edge of the substrate is passed through the ventilation resistor, and the gas in the gap between the ventilation resistor and the rectifying plate is exhausted toward the outside of the rectifying plate, And a step of evaporating a solvent component contained in the coating solution.

Images