JP2004087934A - Resist coating method and resist coating apparatus - Google Patents

Abstract

A resist coating apparatus and a resist coating method capable of uniformly applying a resist to a bottom portion, a wall portion, and a top edge portion of a deep groove pattern having a depth of 30 μm or more formed on a surface of a Si wafer using a spray coating method. It is to provide.
A resist coating apparatus according to the present invention includes a chuck and a spin motor for suction-fixing and rotating a Si wafer having a stepped pattern formed on a surface thereof, and an electromagnetic induction coil for heating the Si wafer. A coater cup 8 having a discharge nozzle 12 for spraying the resist 13 in a mist on the Si wafer 1, preventing the resist 13 from being scattered around the resist 13 by the resist spray by the discharge nozzle 12, and discharging an excess resist; An infrared radiation thermometer 11 for measuring the surface temperature of the Si wafer 1 and an electromagnetic induction coil control device for receiving a signal from the infrared thermometer 11 and controlling the electromagnetic induction coil 9 to adjust the temperature of the Si wafer 10 to form a uniform resist film on the step pattern.
[Selection diagram] Fig. 1

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a resist coating method and a resist coating apparatus for coating a resist on a wafer surface having a deep pattern groove formed on the wafer surface, particularly in a photolithography process in a semiconductor manufacturing process.
[0002]
[Prior art]
In recent years, a Micro Electro Mechanical System (MEMS) has been spotlighted, and the technical development of a resist exposure method (photolithography) in a silicon substrate etching process corresponding to miniaturization and complexity has become an urgent need. I have.
[0003]
In particular, it has been proposed to form a new pattern or wiring by making a pattern groove deeper with the miniaturization of the pattern shape and increasing integration, applying a resist to the wall surface or the bottom surface thereof, and performing additional etching. However, if a deep groove pattern having a depth of about 30 μm or more is filled with a resist, there is a problem that light of photolithography is blocked and a deep portion cannot be exposed. Therefore, it is necessary to apply the resist thinly and uniformly. is there. Many such coating methods have been proposed.
[0004]
Conventionally, as a method of forming a resist film on the wafer surface in the photolithography process, a spin coating method of forming a uniform film by centrifugal force by dropping a resist on the surface of the wafer center while rotating the wafer, and a low-speed A spray coating method is widely used in which a mist-like resist is sprayed from the outer peripheral side to the center of the wafer while rotating to form a uniform thin film on almost the entire surface.
[0005]
In the spin coating method, the viscosity of the resist is important because the resist is spread by a centrifugal force of rotation to form a uniform film. Since this viscosity is highly dependent on temperature, a method has been proposed in which the resist dropped on the wafer surface is controlled to a predetermined temperature in order to maintain the predetermined viscosity.
[0006]
(1) In JP-A-11-276972, in order to keep a resist at a predetermined temperature, a part of the resist is pooled before discharging and the temperature is controlled, or the coater cup covering the entire wafer rotating mechanism is controlled in temperature. And a technique for controlling the temperature of a motor flange of a wafer rotating mechanism. However, in this method, since there are many temperature control parts, there is a problem that the equipment is inevitably increased in size and complexity, the cost cannot be reduced, and the temperature of the wafer surface cannot be measured. .
[0007]
(2) Japanese Patent Application Laid-Open No. 10-261579 discloses that a heated high-pressure gas is sprayed on the back surface of a wafer to adjust the temperature of the wafer body. However, it seems that it is very difficult to keep the resist at a constant viscosity because the resist containing a large amount of volatile components is dried by warm air, and it is difficult to keep the wafer and the rotating mechanism at a predetermined temperature with warm air. It can be determined that it is difficult.
[0008]
Therefore, in the spin coating method, when the pattern grooves formed on the wafer surface are relatively shallow, about 30 μm or less, filling the grooves to form a flat resist-coated surface can also be performed by the above method. It is possible. However, even if the temperature of the resist is adjusted, it is impossible to cope with a pattern having a deep groove depth by the spin coating method.
[0009]
Therefore, a spray coating method is rapidly spreading in recent years. The spray coating method is a method in which a resist is formed into a fine mist and sprayed onto a wafer surface, and the thickness of the resist can be adjusted relatively easily. Therefore, it is effective for a pattern having a fine and complicated shape. However, when a new pattern or wiring is to be formed on the wall surface or bottom surface of the pattern groove, it is necessary to apply the resist evenly on these surfaces. However, conventionally, in the spray coating method, there is no means for heating the wafer and no means for keeping the resist at a predetermined temperature, and the fixing time depends on the evaporation rate of the volatile solvent contained in the resist, so that it is difficult to control the fixing time. There were problems such as. That is, in a deep groove pattern or the like, there is a problem that a large amount of resist easily accumulates at the corner of the bottom surface, and conversely, at the top edge of the groove, the resist flows before being fixed and is not attached.
[0010]
[Problems to be solved by the invention]
FIG. 3A shows an enlarged sectional view of a pattern portion of a Si substrate on which a resist is applied by a spin coating method. In the spin coating method, since the pattern portion formed on the Si substrate is buried due to the nature of the coating method and the resist becomes flat, as described above, the portion where the depth of the groove is 30 μm or more is exposed to light of an exposure machine. There is a problem that does not penetrate.
[0011]
On the other hand, FIG. 3B is an enlarged cross-sectional view of a pattern portion of a Si substrate on which a resist is applied by a spray coating method. In the spin coating method, too, it is difficult to control the fixing time of the resist as described above. Particularly, at the bottom corner of the groove pattern, a large amount of the resist easily accumulates because the resist attached to the wall flows down. In such a portion, there was a problem that the resist flowed before being fixed and was not adhered.
[0012]
Therefore, as shown in the enlarged sectional view of the pattern portion of the Si wafer shown in FIG. 3C, the bottom portion, the wall portion, and the top portion of the deep groove pattern having a depth of 30 μm or more formed on the surface of the Si wafer by using the spray coating method. An object of the present invention is to provide a resist coating apparatus and a resist coating method that can uniformly apply a resist to an entire area including an edge portion.
[0013]
[Means for Solving the Problems]
In order to achieve the above object, a resist coating apparatus according to the present invention comprises a rotating means for fixing and rotating a wafer substrate and a spray for spraying a resist on the wafer substrate in a mist state. Means for heating a wafer substrate through a contact portion between the rotating means and the wafer substrate. Thereby, the surface temperature of the wafer can be heated to a predetermined temperature. By heating the wafer, the vaporization rate of the volatile solvent contained in the resist applied to the wafer surface by the spray coating method can be controlled. Therefore, it is possible to prevent the resist from flowing into a groove pattern or the like provided on the wafer, prevent spots from being applied, and the like, and realize a uniform resist thickness.
[0014]
Further, as described in claim 2, the resist coating apparatus of the present invention controls the wafer heating means by receiving a signal from the temperature measuring means for measuring a surface temperature of the wafer and a signal from the temperature measuring means. It is preferable that the apparatus further comprises a temperature controller for adjusting the temperature of the wafer. This makes it possible to more easily control the surface temperature of the wafer to a predetermined temperature. By controlling the temperature of the wafer, the evaporation rate of the volatile solvent contained in the resist applied to the wafer surface by the spray coating method Can be controlled more easily. Therefore, it is possible to prevent the resist from flowing into a groove pattern or the like provided on the Si wafer, prevent spots on the coating, and the like, and realize a more uniform resist thickness.
[0015]
Further, as described in claim 3, the heating means includes a chuck made of a magnetic material for fixing a wafer on the surface of the wafer rotating means, and an electromagnetic induction coil installed in a portion located below the chuck. It is preferable to be comprised by. Thereby, by supplying electric power to the electromagnetic induction coil, the lines of magnetic force generated on the surface of the electromagnetic induction coil generate an eddy current passing through the inside of the chuck, and generate heat by the internal resistance of the chuck made of a magnetic material, The wafer is heated. Therefore, since the chuck on which the wafer is fixed can be directly heated, the heating efficiency and responsiveness are good, and the temperature of the wafer can be easily controlled by controlling the amount of electric power supplied to the electromagnetic induction coil. Further, since the electromagnetic induction coil can be installed without contact with the rotating chuck, a heating means having a simple structure can be configured. Furthermore, since the electromagnetic induction heating method is not a direct fire, it is possible to safely use a resist containing a large risk of ignition or explosion.
[0016]
The temperature measuring means measures the heated surface of the wafer with an infrared radiation thermometer, feeds back the temperature above the temperature to the temperature control means, performs processing, and controls the amount of power supplied to the electromagnetic induction coil. I have. Thereby, since the surface temperature of the wafer fixed to the rotating chuck can be directly measured with high accuracy, highly accurate temperature control can be performed. Furthermore, temperature measurement and temperature control of the wafer surface can be performed with a simple configuration.
[0017]
According to a fourth aspect of the present invention, the resist coating apparatus surrounds the wafer substrate fixed to the rotating means, prevents the resist from being scattered by the resist spraying means, and receives and discharges excess resist. It is preferable to further include Thus, when excess resist is generated, the excess resist scattered in the outer peripheral direction due to the centrifugal force of the wafer collides with the inner wall of the shielding means surrounding the outer periphery of the wafer, moves to the bottom side of the shielding means, and moves to the apparatus. Since it is discharged outside, there is no fear that the peripheral device is stained by the excess resist.
[0018]
Further, when such a shielding means is provided, as described in claim 5, the heating means comprises: a chuck made of a magnetic material for fixing a wafer on the surface of the wafer rotating means; It is desirable that the device be configured with a donut-shaped electromagnetic induction coil buried in a portion located below and in a portion located in the center of the coater cup, which is the shielding means, in order to reduce the size and simplicity of the device configuration. .
[0019]
In order to achieve the above object, a resist coating method of the present invention controls the surface temperature by heating the wafer to a predetermined temperature using the resist coating apparatus according to any one of claims 1 to 5. And spraying the resist while controlling the rate at which volatile components contained in the sprayed resist are vaporized by a change in the temperature of the wafer surface. According to this method, the wafer surface can be maintained at a predetermined temperature, so that the viscosity of the resist whose coating state depends on the temperature is substantially constant and the thickness of the resist can be controlled uniformly. Further, the wafer is a Si wafer substrate on which a pattern having a step on the surface is formed as described in claim 7, and in particular, the pattern formed on the wafer is described in claim 8. When performing resist coating on a complicated pattern formed on the wafer surface, such as when the groove is a deep groove pattern with a groove depth of 30 μm or more, the wafer surface temperature is applied to the top edge and wall surface of the groove. If the temperature is set higher than the predetermined temperature and the resist is dried quickly, it is possible to prevent run-off, so that a uniform resist film can be formed on the top edge portion or wall surface portion of the groove.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Next, embodiments of the present invention will be described in detail with reference to the drawings.
[0021]
FIG. 1 is an overall configuration diagram including a partial cross section showing one embodiment of a resist coating apparatus according to the present invention. FIG. 2 is a schematic diagram illustrating the heating principle of the Si wafer according to the present invention.
[0022]
First, the overall configuration of a resist coating apparatus according to the present invention will be described with reference to FIG. The Si wafer is made of a magnetic material having a vacuum evacuation groove 2 formed radially from the center toward the outer periphery (in this embodiment, after processing the general structural rolled steel SS400, the surface is made of tetrafluoroethylene resin). Is used, but the present invention is not limited to this. The chuck 3 is installed by vacuum suction. At the center of the lower surface of the chuck 3, an insulation / heat insulation flange 4 for the purpose of insulation and heat insulation is fixed. In this embodiment, a machinable ceramic having a high heat insulating effect is used, but the material is not particularly limited as long as it can be insulated and heat insulated. The insulating / insulating flange 4 is fixed to the tip of the rotating shaft 6 of the spin motor 5 so that there is no run-out during rotation. A vacuum suction port 7 for vacuum suction of the Si wafer 1 into the chuck 3 is provided at the center of the spin motor 5, the rotating shaft 6 and the insulating / heat insulating flange 4. A coater cup 8 is provided so as to surround the Si wafer 1 and the chuck 3. A donut-shaped electromagnetic induction coil 9 is embedded inside the coater cup 8 and on the temporary surface of the chuck 3 so as not to contact the rotating chuck 3. A discharge port 17 is provided on the bottom surface of the coater cup 8. A power supply cable for supplying electric power is drawn out of the electromagnetic induction coil 9 and connected to the electromagnetic induction coil control device 10. Further, a signal cable of an infrared radiation thermometer 11 installed above the position where the Si wafer 1 is disposed and measuring the surface temperature of the Si wafer 1 is also connected to the electromagnetic induction coil control device 10. Above the position where the Si wafer 1 is disposed, a discharge nozzle 12 that is movable in the in-plane radial direction of the Si wafer is provided so that a mist-like resist 13 can be sprayed on the Si wafer.
[0023]
Next, a heating method using the electromagnetic induction coil 9 will be described with reference to FIG. When electric power is supplied to the electromagnetic induction coil 9, lines of magnetic force 14 are generated in the space between the upper and lower surfaces of the electromagnetic induction coil 9 from the center to the circumference. The spin chuck 3 is installed above the electromagnetic induction coil 9, and since the material is a magnetic material, the chuck 3 becomes a yoke, and the magnetic force lines 14 pass through the inside. Therefore, an eddy current 15 is generated inside the chuck 3 in a circumferential direction within the plane. Then, since the material of the chuck 3 has electric resistance, the eddy current 15 changes to heat and the chuck 3 generates heat.
[0024]
Next, a method for applying a resist by using the resist coating apparatus according to one embodiment of the present invention will be described.
[0025]
First, the Si wafer 1 is placed almost on the upper surface of the spin chuck 3 and fixed to the chuck 3 by vacuum suction. Next, the switch of the spin motor 5 is turned on, and the Si wafer 1 is rotated in the rotation direction 16. In this embodiment, the number of revolutions is set to 100 rpm, but can be varied depending on the film thickness accuracy. Next, the power supply of the electromagnetic induction coil control device 10 is turned on, and the set temperature of the temperature controller is set to a predetermined heating temperature of the Si wafer 1. In this embodiment, the set temperature is set to 60 ° C. to 80 ° C., but the temperature is not limited to this range. Next, the power of the infrared radiation thermometer 11 is turned on, and the temperature of the surface of the Si wafer is measured. At this time, the infrared radiation thermometer 11 is set in advance so that the lens is focused on the surface of the Si wafer 1, and the infrared emissivity is also corrected so as to meet the surface of the Si wafer. Next, the temperature signal of the infrared radiation thermometer 11 is fed back to the electromagnetic induction coil control device 10, and power is supplied to the electromagnetic induction coil 9 while comparing the set temperature with the Si wafer surface temperature. When electric power is supplied to the electromagnetic induction coil 9, the chuck 3 generates heat according to the principle described in the above-described heating method, and the Si wafer 1 that is fixed in close contact with the chuck 3 is heated. Next, when the surface temperature of the Si wafer 1 reaches the set temperature and the temperature is stabilized, the discharge nozzle 12 sprays the resist 13 from the outer peripheral portion to the central portion of the Si wafer 1 while spraying the resist 13. Move about 1 radius. At this time, the resist coating amount is several hundred microliters / second. After the resist 13 is applied to the surface of the Si wafer 1, if excess resist is generated, the resist 13 is scattered in the outer peripheral direction due to the centrifugal force of the Si wafer 1. The scattered surplus resist collides with the inner wall of the coater cup 8 and accumulates on the bottom surface and is discharged from the discharge port 17 to the outside of the apparatus. On the other hand, the resist 13 applied to the Si wafer 1 heated to a predetermined temperature is heated, and the volatile solvent in the resist is vaporized and adheres to the wafer 1. In other words, if the heating temperature of the resist 13 is controlled, the evaporation rate of the volatile solvent can be controlled, so that the fixing rate of the resist 13 can be controlled. Therefore, if the set temperature is accurately adjusted (in this embodiment, the resolution is 0.5 ° C.), as shown in FIG. 3C, the resist can be almost uniformly applied to the top edge, the wall, and the bottom.
[0026]
In the above embodiment, the wafer to be used is a Si wafer. However, in the present invention, the wafer is not particularly limited to the Si wafer, and can be applied to other various wafers. Further, the present invention can be suitably used in a wafer on which a pattern having a step on the surface is formed, particularly when the pattern formed on the wafer is a deep groove pattern having a groove depth of 30 μm or more. However, it is needless to say that the present invention can be applied to resist application to a wafer on which such a pattern is not formed.
[0027]
Further, in the above-described embodiment, the wafer heating means is constituted by the chuck 3 made of a magnetic material and the electromagnetic induction coil 9 disposed below the chuck 3. It is not limited to this as long as it can heat the wafer substrate through the contact portion between the means and the wafer substrate.For example, microwave, high frequency, far infrared rays or infrared rays, Any material that can directly or indirectly heat the site (chuck 3) can be used. If electrical connection to the rotating body is required, for example, a known rotary switch may be used.
[0028]
Further, in the above embodiment, the wafer is fixed to the rotating means by the vacuum suction of the chuck 3, but the wafer fixture (chuck) in the rotating means is not limited to the one by the vacuum suction. , And other types.
[0029]
Further, the configuration of the other parts in the resist coating apparatus according to the present invention is not limited to those in the above-described embodiment, and replacement, addition, improvement, and the like can be performed within a range that can achieve the object of the present invention. This will be easily understood by those skilled in the art.
[0030]
【The invention's effect】
As described above, according to the resist coating apparatus of the present invention, since the surface temperature of the Si wafer can be controlled to a predetermined temperature, the volatile solvent contained in the resist applied to the upper surface of the Si wafer by the spray coating method Can control the vaporization temperature. Therefore, it is possible to prevent the resist from flowing into a groove pattern or the like provided on the Si wafer, prevent spots from being applied, and the like, and realize a uniform resist thickness. Further, if the heating means is constituted by a chuck made of a magnetic material and an electromagnetic induction coil installed at a portion located below the chuck, the spin chuck which vacuum-adsorbs the Si wafer can be directly heated, so that the heating efficiency and the response can be improved. It is possible to easily control the temperature of the Si wafer by controlling the amount of electric power supplied to the electromagnetic induction coil with good performance. In addition, since it can be installed without contact with the rotating spin chuck, a heating means having a simple structure can be configured. Further, since the electromagnetic induction heating method has no ignition point, it is possible to safely use a resist containing a large amount of a volatile solvent having a risk of ignition or explosion.
[0031]
As described above, according to the resist coating apparatus of the present invention, the surface temperature of the Si wafer vacuum-adsorbed to the rotating chuck can be directly and accurately measured, so that highly accurate temperature control is possible. Further, temperature measurement and temperature control of the Si wafer surface can be performed with a simple configuration.
[0032]
Further, according to the resist coating method of the present invention, the surface of the Si wafer can be maintained at a predetermined temperature. Can be uniformly controlled. Furthermore, when applying resist to a complicated pattern formed on the surface of the Si wafer, the surface temperature of the Si wafer should be set higher than a predetermined temperature for the top edge and wall surface of the groove, and the resist should be dried quickly. In this case, it is possible to provide a method capable of forming a uniform resist film on a top edge portion or a wall surface portion of the groove because the flow-down can be prevented.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram including a partial cross section showing an embodiment of a resist coating apparatus according to the present invention.
FIG. 2 is a schematic diagram illustrating a heating principle of a Si wafer according to the present invention.
3A and 3B are enlarged cross-sectional views of a pattern portion of a Si wafer. FIG. 3A shows an example of resist coating by a conventional spin coating method, FIG. 3B shows an example of resist coating by a conventional spray coating method, and FIG. 3A and 3B respectively show resist coating example states according to the embodiment of the present invention.
[Explanation of symbols]
REFERENCE SIGNS LIST 1 Si wafer 2 Vacuum suction groove 3 Chuck 4 Insulating / insulating flange 5 Spin motor 6 Rotating shaft 7 Vacuum suction port 8 Coater cup 9 Electromagnetic induction coil 10 Electromagnetic induction coil controller 11 Infrared radiation thermometer 12 Discharge nozzle 13 Resist 14 Magnetic force line 15 Eddy current 16 Wafer rotation direction 17 Outlet

Claims (8)

Rotating means for fixing and rotating the wafer substrate; spraying means for spraying the resist on the wafer substrate in a mist state; and wafer heating means for heating the wafer substrate through a contact portion between the rotating means and the wafer substrate. A resist coating apparatus. The apparatus further includes a temperature measurement unit that measures a surface temperature of the wafer, and a temperature control unit that receives a signal from the temperature measurement unit and controls the wafer heating unit to adjust the temperature of the wafer. The resist coating apparatus according to claim 1, wherein 2. The heating device according to claim 1, wherein the heating unit includes a chuck made of a magnetic material for fixing the wafer on the surface of the wafer rotating unit, and an electromagnetic induction coil installed in a portion located below the chuck. Or the resist coating apparatus according to 2. 4. The apparatus according to claim 1, further comprising a shielding unit surrounding the wafer substrate fixed to the rotating unit, preventing scattering of the resist by the resist spraying unit, and receiving and discharging the excess resist. 3. The resist coating apparatus according to 1. The heating means is embedded in a chuck made of a magnetic material for fixing the wafer on the surface of the wafer rotating means, and in a portion located below the chuck and in a central portion of the coater cup which is the shielding means. 5. The resist coating device according to claim 4, wherein the resist coating device is configured by a donut-shaped electromagnetic induction coil. The resist was sprayed while controlling the surface temperature by heating the wafer to a predetermined temperature using the resist coating apparatus according to any one of claims 1 to 5, and sprayed with a change in the wafer surface temperature. A resist coating method, wherein the coating is performed by controlling the rate at which volatile components contained in the resist are vaporized. The method according to claim 6, wherein the wafer is a Si wafer substrate on which a pattern having a step on a surface is formed. The method according to claim 7, wherein the pattern formed on the wafer is a deep groove pattern having a groove depth of 30 μm or more.

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