JP5242635B2 - Coating method and coating apparatus - Google Patents

Description

  The present invention relates to a coating method and a coating apparatus for forming a coating film such as a photoresist film on a substrate, and particularly to a technique for improving the uniformity of the film thickness of the coating film.

  In a photolithography process in a semiconductor device manufacturing process, a resist coating process for coating a resist solution on a semiconductor wafer (hereinafter referred to as “wafer”) to form a resist film, and an exposure process for exposing the resist film to a predetermined pattern A developing process for developing the exposed resist film is sequentially performed, and a predetermined resist pattern is formed on the wafer.

  In the resist coating process, a resist solution is supplied from the nozzle to the center of the rotating wafer surface, and the resist solution is diffused radially outward by centrifugal force so that the entire surface of the wafer is covered with the resist solution. A so-called spin coating method is often used.

  With the recent further miniaturization of the circuit of a semiconductor device, the resist film has been made thinner in the resist coating process. Further, the resist solution is expensive, and it is necessary to reduce the amount used as much as possible.

  When an extremely thin resist film is formed, higher in-plane film thickness uniformity is required. However, if the supply amount of the resist solution is reduced, it becomes difficult to obtain sufficient in-plane film thickness uniformity. For example, it is assumed that a resist solution having a thickness of about 100 nm is formed by supplying 0.5 ml or less of a resist solution to a 12-inch wafer. In this case, even if the application conditions (wafer rotation speed, resist solution supply timing, etc.) are optimized, a film thickness difference of about 1 nm occurs in the wafer surface. This difference in film thickness is not a problem for conventional thick resist films, but cannot be ignored for ultra-thin resist films that have been demanded in recent years. If the resist film thickness is non-uniform, the optical path length of the exposure during the exposure process will be non-uniform, making it difficult to perform a uniform exposure process in the surface.

JP-A-7-78743 JP-A-10-261579

  The present invention makes it possible to adjust the distribution of the coating film thickness in the substrate surface even when a thin coating film is formed by reducing the supply amount of the coating liquid, and the coating film having a high in-plane film thickness uniformity. The present invention provides a technique that makes it possible to form

  According to the first aspect of the present invention, a coating liquid is applied to the central portion of the substrate, the substrate is rotated, and the entire surface of the substrate is covered with the coating liquid. The coating liquid coating process And a drying step of rotating the substrate in a state where supply of the coating solution is stopped and drying the coating solution, and in the drying step, specifying the radial direction of the substrate from the back side of the substrate A method for forming a coating film is provided which locally adjusts the temperature in the above range.

  Preferably, the local adjustment of the temperature is started as soon as the entire surface of the substrate is covered with the coating solution.

  In a preferred embodiment, in the coating film forming method, the coating liquid applied to the surface of the substrate is flattened by rotating the substrate at a rotational speed lower than the rotational speed of the substrate in the coating liquid coating step. The coating liquid application step, the planarization step, and the drying step are sequentially performed in this order, and the transition from the planarization step to the drying step is the rotation speed of the substrate. The local adjustment of the temperature is started when or after the drying process is started.

  The local adjustment of the temperature can be performed by spraying a temperature control fluid locally in a specific range in the radial direction of the back surface of the substrate. Preferably, the temperature control fluid is a gas such as air or an inert gas. When using gas as a temperature control fluid, the temperature of the said gas can be made into the range of 30 to 40 degreeC, for example. The temperature control fluid is sprayed by using a temperature control fluid nozzle that has a discharge port that opens near the back surface of the substrate and blows the temperature control fluid locally in a specific range in the radial direction of the back surface of the substrate. it can.

  The local adjustment of the temperature can also be performed by locally irradiating a heat ray to a specific range in the radial direction of the back surface of the substrate. Examples of the heat rays include infrared LED light and laser light.

  According to the second aspect of the present invention, the spin chuck that holds and rotates the substrate, the coating liquid nozzle that supplies the coating liquid to the surface of the substrate held by the spin chuck, and the spin chuck A cup provided so as to surround the substrate, an exhaust mechanism for sucking the inside of the cup to form an air flow in the cup, and a specific range in the radial direction of the substrate from the back side of the substrate held by the spin chuck And a temperature adjusting means provided so as to locally adjust the temperature of the coating apparatus.

  According to a third aspect of the present invention, a spin chuck for holding and rotating a substrate, a coating liquid nozzle for supplying a coating liquid to the substrate held by the spin chuck, and a substrate held by the spin chuck A temperature adjusting means provided so as to be able to locally adjust the temperature in a specific range in the radial direction of the substrate from the back side, a coating liquid supply mechanism for supplying the coating liquid to the coating liquid nozzle, and at least the above In a coating apparatus comprising a spin chuck, a control unit comprising a computer for controlling operations of the coating liquid supply mechanism and the temperature adjusting means, at least operations of the spin chuck, the coating liquid supply mechanism and the temperature adjusting means are controlled. A computer-readable recording medium storing a program for executing the program, wherein the program is stored in the computer By executing the control, the computer controls the spin chuck, the coating liquid supply mechanism, and the temperature adjusting means to supply the coating liquid from the coating liquid nozzle to the center of the substrate, and to rotate the substrate by the spin chuck. A coating liquid coating process in which the entire surface of the substrate is covered with a coating liquid; and after the coating liquid coating process, the substrate is held by the spin chuck in a state where supply of the coating liquid from the coating liquid nozzle is stopped. There is provided a recording medium that performs a drying process of rotating and drying the coating liquid, and performing the local temperature adjustment by the temperature adjusting means in the drying process.

  According to the present invention, the thickness distribution of the coating film can be adjusted by locally adjusting the temperature in a specific range in the radial direction of the substrate from the back side of the substrate in the drying step of drying the coating liquid. . Thereby, the in-plane uniformity of the thickness of the coating film can be improved.

It is a top view which shows the outline of a structure of a coating-development processing system. It is a front view of a coating and developing treatment system. It is a rear view of a coating and developing treatment system. It is a schematic longitudinal cross-sectional view which shows the structure of a resist coating apparatus. It is a schematic cross-sectional view which shows the structure of a resist coating device. It is a flowchart which shows the main processes of a resist coating process. It is a graph which shows the rotational speed of the wafer in each process of a resist coating process with the supply timing of a prewetting liquid and a resist liquid, and the spraying timing of temperature control gas. It is a graph which shows an experimental result. It is the schematic which shows the modification of a temperature control nozzle. It is the schematic which shows the 1st example using a heat ray irradiation apparatus as a temperature control means. It is the schematic which shows the 2nd example using a heat ray irradiation apparatus as a temperature control means.

Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.
First, the overall configuration of a coating and developing treatment system in which a coating apparatus for coating a resist on a substrate is incorporated will be described with reference to FIGS.

  As shown in FIG. 1, the coating and developing treatment system 1 includes, for example, a cassette station 2 for loading and unloading a plurality of wafers W from the outside to the coating and developing treatment system 1 in cassette units, and sheets in a photolithography process. A configuration in which a processing station 3 including a plurality of various processing apparatuses that perform predetermined processing in a leaf type and an interface station 5 that transfers the wafer W between the exposure apparatus 4 adjacent to the processing station 3 are integrally connected. have.

  The cassette station 2 is provided with a cassette mounting table 10, and a plurality of cassettes C can be mounted on the cassette mounting table 10 in a row in the X direction (vertical direction in FIG. 1). The cassette station 2 is provided with a wafer transfer device 12 that can move on the transfer path 11 along the X direction. The wafer transfer device 12 is also movable in the arrangement direction (Z direction; vertical direction) of the wafers W accommodated in the cassette C, and can selectively access a plurality of wafers W in the cassette C. Further, the wafer transfer device 12 can rotate around the vertical axis (θ direction), and can access each processing device of a third processing device group G3 of the processing station 3 described later to transfer the wafer W. .

  The processing station 3 includes, for example, five processing device groups G1 to G5 in which a plurality of processing devices are arranged in multiple stages. On the negative side in the X direction (downward in FIG. 1) of the processing station 3, the first processing device group G1 and the second processing device group G2 are sequentially arranged from the cassette station 2 side to the interface station 5 side. Has been placed. On the positive side of the processing station 3 in the X direction (upward in FIG. 1), the third processing device group G3, the fourth processing device group G4, and the fifth processing device group G3 are directed from the cassette station 2 side to the interface station 5 side. The processing device group G5 is arranged in order. A first transfer device 20 is provided between the third processing device group G3 and the fourth processing device group G4. The first transfer device 20 can selectively access each device in the first processing device group G1, the third processing device group G3, and the fourth processing device group G4 to transfer the wafer W. A second transport device 21 is provided between the fourth processing device group G4 and the fifth processing device group G5. The second transfer device 21 can selectively access each device in the second processing device group G2, the fourth processing device group G4, and the fifth processing device group G5 to transfer the wafer W.

  As shown in FIG. 2, the first processing apparatus group G1 includes a liquid processing apparatus that performs processing by supplying a predetermined liquid to the wafer W, for example, resist coating apparatuses 30, 31, and 32 as coating apparatuses, and exposure processing. Bottom coating apparatuses 33 and 34 for forming an antireflection film for preventing reflection of light at the time are stacked in five stages in order from the bottom. In the second processing unit group G2, liquid processing units, for example, development processing units 40 to 44 for supplying a developing solution to the wafer W and performing development processing are stacked in five stages in order from the bottom. In addition, chemical chambers 50 and 51 for supplying various processing liquids to the liquid processing apparatuses in the processing apparatus groups G1 and G2 are provided at the bottom of the first processing apparatus group G1 and the second processing apparatus group G2. Are provided.

  For example, as shown in FIG. 3, in the third processing unit group G3, a temperature control device 60 for adjusting the temperature of the wafer W by placing the wafer W on a temperature control plate, and a transition for transferring the wafer W are provided. The apparatus 61, the temperature control apparatuses 62 to 64, and the heat processing apparatuses 65 to 68 that heat-process the wafer W are stacked in nine stages in order from the bottom.

  The fourth processing unit group G4 includes, for example, a temperature control unit 70, pre-baking units 71 to 74 that heat-treat the wafer W after the resist coating process, and post-bake units 75 to 79 that heat-process the wafer W after the development process. They are stacked in 10 steps in order.

  In the fifth processing unit group G5, a plurality of heat treatment apparatuses for heat-treating the wafer W, for example, temperature control apparatuses 80 to 83, and post-exposure bake apparatuses 84 to 89 for heat-treating the wafer W after exposure are arranged in 10 stages in order from the bottom. It is piled up.

  As shown in FIG. 1, a plurality of processing devices are arranged on the positive side in the X direction of the first transfer device 20. For example, an adhesion device 90 for hydrophobizing the wafer W as shown in FIG. , 91 are stacked in two steps in order from the bottom. As shown in FIG. 1, a peripheral exposure device 92 that selectively exposes only the edge portion of the wafer W, for example, is disposed on the positive side in the X direction of the second transfer device 21.

  In the interface station 5, for example, as shown in FIG. 1, a wafer transfer apparatus 101 that moves on a transfer path 100 extending in the X direction and a buffer cassette 102 are provided. The wafer transfer apparatus 101 is movable in the Z direction and is also rotatable in the θ direction, and is relative to the exposure apparatus 4 adjacent to the interface station 5, the buffer cassette 102, and the fifth processing apparatus group G5. The wafer W can be transferred by accessing.

  Note that the exposure apparatus 4 in the present embodiment is an immersion exposure apparatus, and a wafer, such as a pure water liquid film, is retained on the surface of the wafer W, with the pure water liquid film interposed therebetween. The resist film on the surface can be exposed. However, the exposure apparatus 4 may perform other types of exposure.

  Next, the configuration of the resist coating apparatuses 30 to 32 will be described with reference to FIGS. Since the configurations of the resist coating apparatuses 30 to 32 are substantially the same, the configuration of the resist coating apparatus 30 will be described as a representative.

  As shown in FIG. 4, the resist coating apparatus 30 includes a casing 120, and a spin chuck 122 serving as a rotation holding unit that holds and rotates the wafer W is provided in the center of the casing 120. The spin chuck 122 has a horizontal upper surface 122a, and a suction port (not shown) for sucking, for example, the wafer W is provided on the upper surface. The wafer W can be sucked and held on the spin chuck 122 by suction from this suction port.

  The spin chuck 122 has a chuck drive mechanism 124 having a rotation drive source such as a rotation motor (not shown), and can be rotated at a predetermined speed by the chuck drive mechanism 124. Further, the chuck driving mechanism 124 is provided with a lifting drive source such as an air cylinder, and the spin chuck 122 can move up and down.

  Around the spin chuck 122, there is provided a cup 130 that receives and collects the liquid scattered or dropped from the wafer W. The cup 130 includes an inner cup body 131, an intermediate cup body 132, an outer cup body 133, and a plate-shaped cup base 134 provided so as to close the bottom opening of the inner cup body 131. The rotating shaft 122b of the spin chuck 122 passes through the cup base 134.

  An annular space 132a is defined at the bottom of the intermediate cup body 132, and an exhaust pipe 135 is inserted into the annular space 132a. An exhaust mechanism (EXH) 136 schematically shown in the drawing is connected to the exhaust pipe 135 so that the annular space 132a can be sucked. The exhaust mechanism 136 can be configured by connecting a means for making the suction flow rate variable, for example, a pipe line provided with a variable damper to an exhaust duct of a factory. Further, a drainage pipe 137 is connected to an opening provided in the bottom wall of the intermediate cup body 132 that partitions the annular space 132a. The drainage pipe 137 is connected to a waste liquid system (DR) 138.

  A fan filter unit (FFU) 126 that forms a downflow DF of clean gas, for example, clean air, is provided in the upper part of the casing 120. An exhaust passage 127 that exhausts the atmosphere in the casing 120 is connected to the lower portion of the casing 120.

  When the annular space 132a is sucked by the exhaust mechanism 136, an air flow indicated by an arrow on the right side of FIG. 4 is generated. When the processing liquid is supplied to the wafer W supported and rotated by the spin chuck 122, the processing liquid scatters radially outward in the form of droplets or mist by centrifugal force. Such a droplet or mist rides on the air flow indicated by the arrow on the right side of FIG. 4 and is smoothly guided to the annular space 132a so that it does not reattach to the wafer W. Most of the liquid introduced into the annular space 132a is separated from the air current when the direction of the air current changes in the annular space 132a, and is discharged through the drain pipe 137. Further, part of the mist and gas introduced into the annular space 132 a are exhausted through the exhaust pipe 135.

  A space BS surrounding the back surface of the wafer W is formed by the inner inclined surface 131 a of the inner cup body 131 and the upper surface 134 a of the cup base 134. When the wafer W rotates, the gas in the vicinity of the wafer W is moved, and a relatively weak air flow called a back flow from the center of the wafer W toward the peripheral edge of the wafer is generated in the space BS. The backflow BF flows out from the narrowed gap between the upper horizontal surface 131b of the inner cup body 131 and the back surface of the wafer W. For this reason, while the wafer W is rotating, gas, liquid (mist, etc.), contaminant particles, etc. hardly enter the space BS. Even when the wafer W is not rotating, the annular space 132 a is always sucked by the exhaust mechanism 136. For this reason, airflow generated in the cup 130 caused by suction, in particular, the influence of the airflow generated in the space sandwiched between the outer surface 131c of the inner cup body 131 and the inner surface 132b of the intermediate cup body 132, is caused by the inner cup body 131. Gas, liquid (mist, etc.), contaminant particles, etc. hardly enter the space BS from the narrowed gap between the upper horizontal surface 131b and the back surface of the wafer W.

  Needless to say, since the cup 130 is a rotating body in a geometric sense, the airflow is substantially uniformly generated in the circumferential direction. The airflow is shown only on the right side of FIG. 4 in order to avoid complication of the drawing.

  The shape of the cup is not limited to the above, and for example, a cup described in Japanese Patent Application Laid-Open No. 2004-207573 relating to another patent application filed by the present applicant may be used. In the cup described in Japanese Patent Application Laid-Open No. 2004-207573, gas, liquid (mist, etc.), contaminant particles, etc. are also generated in the space (BS) from the narrowed gap between the upper surface of the inner cup body and the back surface of the wafer W. It is configured to prevent entry. Such a configuration is not essential in the installation of the temperature control nozzle described later, but is preferable in that the temperature control nozzle can be designed only for the purpose of temperature control.

  As shown in FIG. 5, a rail 140 extending along the Y direction (left and right direction in FIG. 5) is formed on the X direction negative direction (downward direction in FIG. 5) side of the cup 130. For example, the rail 140 is formed from the outer side of the cup 130 in the Y direction negative direction (left direction in FIG. 5) to the outer side in the Y direction positive direction (right direction in FIG. 5). Two arms 141 and 142 are attached to the rail 140.

  A resist nozzle 143 that discharges a resist solution is supported on the first arm 141. The first arm 141 is movable on the rail 140 by a nozzle driving unit 144 shown in FIG. As a result, the resist nozzle 143 can move from the standby unit 145 installed on the outer side of the cup 130 on the positive side in the Y direction to above the center of the wafer W in the cup 130, and further on the surface of the wafer W It can move in the radial direction of W. The first arm 141 can be moved up and down by a nozzle driving unit 144 and the height of the resist nozzle 143 can be adjusted. The first arm 141 and the nozzle drive unit 144 constitute a resist nozzle moving mechanism. Note that the resist nozzle moving mechanism and standby unit 145 are not shown in FIG.

  As shown in FIG. 4, a supply pipe 147 communicating with a resist solution supply source (PR) 146 is connected to the resist nozzle 143. The resist solution supply source 146 stores a resist solution for ArF immersion exposure. For example, the resist solution is adjusted to a low viscosity (for example, 2 cp or less) for forming a thin resist film, for example, a resist film of 150 nm or less. The supply pipe 147 is provided with a valve 148. By opening and closing the valve 148, the discharge of the resist solution from the resist nozzle 143 can be stopped. The resist solution supply source 146, the supply pipe 147 and the valve 148 constitute a resist solution (coating solution) supply mechanism for supplying the resist solution to the resist nozzle 143.

  A prewetting nozzle 150 is supported on the second arm 142. The second arm 142 is movable on the rail 140 by the nozzle driving unit 151 shown in FIG. 5, and the prewetting nozzle 150 is moved from the standby unit 152 provided on the outer side of the cup 130 in the Y direction negative direction. The wafer can be moved to the upper part of the center of the wafer W in the cup 130. Further, the second arm 142 can be moved up and down by the nozzle driving unit 151, and the height of the pre-wet nozzle 150 can be adjusted. The second arm 142 and the nozzle driving unit 151 constitute a pre-wet nozzle moving mechanism. Note that the pre-wet nozzle moving mechanism and standby unit 152 are not shown in FIG.

  As shown in FIG. 4, a supply pipe 154 communicating with a prewetting liquid supply source (PWT) 153 is connected to the prewetting nozzle 150. The prewetting liquid supply source 153 stores a resist solvent such as OK73 (a mixed solution of propylene glycol monomethyl ether (PGME) and propylene glycol monomethyl ether acetate (PGMEA), manufactured by Tokyo Ohka Kogyo Co., Ltd.) as the prewetting liquid. ing. The prewetting liquid is also called prewetting thinner. The supply pipe 154 is provided with a valve 155. By opening and closing the valve 155, the discharge of the prewetting liquid from the prewetting nozzle 150 can be stopped. The prewetting liquid supply source 153, the supply pipe 154 and the valve 155 constitute a prewetting liquid supply mechanism for supplying the prewetting liquid to the prewetting nozzle 150.

  The relationship between each nozzle and each arm is not limited to that shown in the figure. For example, the resist nozzle 143 and the prewetting nozzle 150 can be supported by a common arm.

  A plurality of temperature adjusting gases, for example, hot air, are blown onto the back surface of the wafer W, and two temperature adjusting nozzles 160 (only one is shown in FIG. 4 for simplification of the drawing) are attached to the cup base 134. Yes. The two temperature control nozzles 160 are provided at positions obtained by equally dividing the circumference around the rotation center of the spin chuck 122 by the number of temperature control nozzles (in this example, equal to two) in plan view. The radial position (the distance from the rotation center of the spin chuck 122) of the two temperature control nozzles 160 is the same. A supply source 161 of clean gas, for example, clean air, is connected to the temperature control nozzle 160 via a pipe line 162. The pipe line 162 is provided with a heater 163 for heating the air flowing in the pipe line 162 to a predetermined temperature, and a valve 164 for supplying and stopping the supply of air. An inert gas such as nitrogen gas can be used as the clean gas. A temperature control gas supply mechanism that supplies temperature control gas to the temperature control nozzle 160 is configured by the air supply source 161, the pipe line 162, and the heater 163.

  The clean air supply source 161 can be constituted by a fan unit with a filter, for example. The heater 163 can be, for example, a tape heater wound around a metal pipe constituting the pipe line 162. The valve 164 may be a simple on-off valve, but may be a valve having a flow rate adjusting function.

  The temperature control nozzle 160 can be in the form of a slit nozzle having a rectangular opening, for example. As a non-limiting example, the temperature control nozzle 160 in the form of a slit nozzle has one end positioned 75 mm from the wafer center in plan view, a long side of 60 mm, and a short side of 2 mm. The temperature control nozzle 160 is capable of blowing the temperature control gas locally on a relatively narrow intended region of the wafer W without being affected by the backflow BF described above. ) The distance between 160a and the back surface of the wafer W is preferably 2 to 30 mm, for example, and more preferably 3 to 10 mm. It is preferable that the temperature control gas collides with the back surface of the wafer W substantially perpendicularly so that the area other than the temperature control target area of the wafer W is not affected by heat. For this reason, the angle formed by the axis 160b (see FIG. 4) of the opening of the temperature control nozzle 160 and the normal of the back surface of the wafer W is preferably 30 degrees or less, and more preferably 10 degrees or less. .

  In one exemplary embodiment, the clean air supply source 161 and the heater 163 are configured such that air at 30 ° C. to 40 ° C. is blown from the temperature control nozzle 160 toward the wafer back surface at a flow rate of 30 to 50 l / min. Performance is defined. However, various parameters such as the radial position of the temperature control nozzle, the temperature and flow rate of air discharged from the temperature control nozzle 160, the shape of the temperature control nozzle 160, and the interval between the discharge port 160a of the temperature control nozzle and the wafer back surface. It is desirable to determine the details by experiment.

  The rotation operation of the spin chuck 122 by the above-described chuck driving mechanism 124, the movement operation of the resist nozzle 143 by the nozzle driving unit 144, the discharge operation of the resist solution of the resist nozzle 143 by the valve 148, and the movement of the pre-wet nozzle 150 by the nozzle driving unit 151. The operation, the operation of discharging the prewetting liquid from the prewetting nozzle 150 by the valve 155, the operation of the clean air supply source 161 for discharging the temperature control gas, the heater 163, the valve 164, etc. are schematically shown in FIG. Part (CNTL) 170. The control unit 170 is configured by a computer including, for example, a CPU and a memory, and the resist coating process in the resist coating apparatus 30 can be realized by executing a program stored in the memory, for example. Various programs for realizing the resist coating process in the resist coating apparatus 30 are stored in a storage medium M such as a computer-readable CD, and are installed in the control unit 170 from the storage medium M. Is used.

  Next, a coating process performed by the resist coating apparatus 30 configured as described above will be described together with a wafer processing process performed by the entire coating and developing processing system 1.

  First, unprocessed wafers W are taken out one by one from the cassette C on the cassette mounting table 10 by the wafer transfer device 12 shown in FIG. 1 and sequentially transferred to the processing station 3. The wafer W is transferred to the temperature control device 60 belonging to the third processing device group G3 of the processing station 3, and the temperature is adjusted to a predetermined temperature. Thereafter, the wafer W is transferred to, for example, the bottom coating device 34 by the first transfer device 20 to form an antireflection film. Thereafter, the wafer W is sequentially transferred to, for example, the heat processing apparatus 65 and the temperature control apparatus 70 by the first transfer apparatus 20, and predetermined processing is performed in each processing apparatus. Thereafter, the wafer W is transferred by the first transfer device 20 to one of the plurality of resist coating devices 30 to 32, for example, the resist coating device 30.

  Regarding a series of steps of the coating process in the resist coating apparatus, refer to FIG. 6 which is a flowchart showing the main steps of the coating process in the resist coating apparatus 30 and FIG. 7 which is a graph showing the rotation speed of the wafer W in each process. explain.

  First, the shutter 129 of the carry-in / out port 128 provided in the casing 120 is opened, and the wafer W is loaded into the resist coating device 30 by a transfer arm (not shown), and then the wafer W is loaded into the spin chuck 122 as shown in FIG. Adsorbed and held.

  Next, the prewetting nozzle 150 in the standby unit 152 is moved above the central portion of the wafer W by the second arm 142.

  With the wafer W stopped, the valve 155 is opened, and a prewetting liquid is supplied from the prewetting nozzle 150 to the center of the wafer (prewetting liquid discharging step S1 in FIG. 6). Thereafter, as shown in FIG. 7, the wafer W is rotated by the spin chuck 122 at a first speed V <b> 1 of about 500 rpm, for example, and the prewetting liquid on the wafer W is diffused over the entire surface of the wafer W, The entire surface is wetted by the prewetting liquid (prewetting liquid diffusion step S2 in FIG. 6). During the prewetting liquid diffusion step S <b> 2, the prewetting nozzle 150 is retreated from the wafer W, and the first nozzle 141 moves the resist nozzle 143 in the standby unit 145 to above the center of the wafer W.

  Thereafter, the valve 148 is opened, and the discharge of the resist solution from the resist nozzle 143 is started as shown in FIG. 7, and the resist solution starts to be supplied to the central portion of the wafer W. Thus, the resist solution coating process S3 is started. In the resist solution coating step S3, the rotation speed of the wafer W is increased from the first speed V1 to a high second speed V2 of about 2000 to 4000 rpm, for example. The rotation of the wafer W at the first speed V1 before the start of the resist solution coating step S3 is gradually accelerated so that the speed continuously and smoothly fluctuates thereafter. At this time, the acceleration of the rotation of the wafer W gradually increases from, for example, zero. At the end of the resist solution coating step S3, the rotation acceleration of the wafer W is gradually reduced, and the rotation speed of the wafer W smoothly converges to the second speed V2. Thus, at the time of the resist solution coating step S3, the rotation speed of the wafer W varies from the first speed V1 to the second speed V2 so as to change in an S shape on the graph of FIG. In the resist solution coating step S <b> 3, the resist solution supplied to the central portion of the wafer W is diffused over the entire surface of the wafer W by centrifugal force, and the resist solution is applied to the surface of the wafer W.

  In addition, you may continue discharge of the resist liquid by the resist nozzle 143 in resist liquid application | coating process S3 to the middle of planarization process S4. At this time, when the discharge of the resist solution is terminated, the resist nozzle 143 may be moved to shift the discharge position of the resist solution from the central portion of the wafer W.

  When the resist solution coating step S3 is continued for a predetermined time and completed, the rotation of the wafer W is decelerated to a low speed, for example, a third speed V3 of about 300 rpm as shown in FIG. 7, and the resist solution on the wafer W is leveled. Is planarized (planarization step S4 in FIG. 6). The planarization step S4 is performed for about 1 second, for example.

  When the flattening step S4 is continued for a predetermined time and completed, the rotation of the wafer W is accelerated to a fourth speed V4 of about 1500 rpm, for example, as shown in FIG. 7, and the resist solution on the wafer W is dried. (Drying step S5 in FIG. 6). The drying step S5 is performed for about 20 seconds, for example. Thus, a thin resist film (photoresist film) is formed on the surface of the wafer W. In the drying step S5, air at a predetermined temperature, for example, 30 ° C. to 40 ° C. is blown from the temperature control nozzle 160 to the back surface of the wafer W at a predetermined flow rate, for example, 30 to 50 l / min, and the back surface of the wafer W is locally heated. The As a result, the thickness of the resist film finally obtained after the drying step S5 is made uniform.

  After the drying of the wafer W is completed, the rotation of the wafer W is stopped, the wafer W is unloaded from the spin chuck 122, and a series of resist coating processes are completed. In addition, after the drying step S5, EBR (edge bead removal) processing and / or BR (back rinse) processing and drying processing after these EBR / BR processing can be executed as necessary. Description of is omitted.

  After the resist coating process, the wafer W is transferred to the pre-baking device 71 by the first transfer device 20 and pre-baked, for example. Subsequently, the wafer W is sequentially transferred to the peripheral exposure device 92 and the temperature adjustment device 83 by the second transfer device 21 and subjected to predetermined processing in each device. Thereafter, the wafer W is transferred to the exposure apparatus 4 by the wafer transfer apparatus 101 of the interface station 5 and subjected to immersion exposure. Thereafter, the wafer W is transferred to, for example, a post-exposure bake device 84 by the wafer transfer device 101, baked after exposure, and then transferred to the temperature adjustment device 81 by the second transfer device 21 to adjust the temperature. Thereafter, the wafer W is transferred to the development processing apparatus 40, and the resist film on the wafer W is developed. After the development, the wafer W is transferred to the post-baking device 75 by the second transfer device 21 and post-baked. Thereafter, the wafer W is transferred to the temperature control device 63 and the temperature is adjusted. Then, the wafer W is transferred to the transition device 61 by the first transfer device 20, and returned to the cassette C by the wafer transfer device 12, and a series of wafer processing is completed.

  In addition, regarding the resist saving technique due to the variation of the wafer rotation speed at the time of resist application in the series of steps S1 to S5, the patent application and the inventor are partly common and the assignee (applicant) is a common patent. This is described in detail in Japanese Patent Application No. 2008-131495, Japanese Patent Application No. 2009-279476.

  Next, advantages of the above embodiment will be described with reference to experimental results.

  A resist film was formed on the wafer W using the resist coating apparatus shown in FIGS. In the drying step S5, the temperature control gas was discharged from the temperature control nozzle 160 as an example, and the temperature control gas was not discharged as a comparative example.

  After the resist film was formed, the thickness distribution of the resist film was measured. The result is shown in the graph of FIG. The vertical axis of the graph is the resist film thickness, and the horizontal axis is the distance from the wafer center. Black squares (♦) are comparative examples, and white squares (□) are examples. The arrow in the graph indicates the spray position of the temperature control gas (specifically, the center position of the temperature control nozzle). From the graph, it is clear that the film thickness distribution width is reduced in the example. Further, the 3σ value of the film thickness, which is an index of statistical variation, was 1.00 nm in the comparative example, but 0.55 nm in the example. That is, a large improvement in the film thickness distribution width was observed.

  The inventor considers the difference between the comparative example and the example as follows.

  In the comparative example, the film thickness is large at the wafer central part and the peripheral part, and small at the part between the central part and the peripheral part (hereinafter referred to as “intermediate part”). The reason is considered as follows. In the case of the spin coating method, since the centrifugal force acting on the resist solution at the center of the wafer is small, the film thickness is considered to be large. The centrifugal force acting on the resist solution is large at the peripheral edge of the wafer. However, on the other hand, it is considered that the concentration of the resist solution is increased when it reaches the peripheral portion due to volatilization of the solvent contained in the resist solution in the process of diffusing the resist solution from the central portion to the peripheral portion. It is done. It is presumed that the effect of increasing the concentration of the resist solution is greater than the effect of centrifugal force, which may be one of the causes for increasing the film thickness at the peripheral portion. Further, the wafer that has been rotating at a high speed in the final stage of the resist solution coating step S3 is rapidly decelerated with the start of the flattening step S4, so that the resist that is about to scatter from the periphery of the wafer may flow back inward in the radial direction. It is thought to be the cause. In addition, the heat transfer flow in the contact portion between the wafer and the spin chuck, the solvent vaporization heat distribution in each portion of the wafer, and the like are also considered. It is considered that the film thickness distribution is caused by various factors intertwined as described above.

  In the example, in the drying step S5, the temperature control gas is blown in the vicinity of the portion where the film thickness is relatively small in the comparative example. Thereby, the film thickness of the part which sprayed temperature control gas and its vicinity (it calls a "temperature control area | region" for convenience) increases. The reason is considered as follows. In the drying step S5, a part of the resist solution existing on the wafer at the end of the planarization step S4 is shaken off to the outside of the wafer by centrifugal force. That is, in the drying step S5, the resist solution moves outward in the radial direction due to centrifugal force. At this time, if the temperature control gas is blown to the temperature control region, the wafer temperature in the temperature control region increases, and as a result, the volatilization of the solvent contained in the resist solution in the temperature control region is promoted, and the resist solution in the temperature control region increases. The concentration is higher than the concentration of the resist solution in the other region. Since the high-concentration resist solution has a high viscosity, even if the wafer is rotated at a relatively high rotation (drying step S5, for example, 1500 rpm), it is difficult to move outward in the radial direction. To do. On the other hand, the resist solution is shaken off at the periphery of the wafer while the movement of the resist solution moving from the radial direction is reduced. As a result, it is considered that the film thickness at the wafer middle portion increases and the film thickness at the wafer peripheral portion decreases. In any case, by performing local heating with the temperature control gas in the drying step S5, the film thickness in the vicinity of the portion where the temperature control gas is blown tends to increase.

  Note that the temperature control gas spray intentionally causes a temperature change in the wafer surface and locally adjusts the degree of volatilization of the solvent in the resist, thereby finely adjusting the film thickness distribution. . Accordingly, if spraying of the temperature control gas is started too early, the film thickness may be uneven. Therefore, it is preferable to spray the temperature control gas after the resist solution has diffused over the entire wafer surface at the earliest. Further, as in the above-described embodiment, the planarization step S4 for further uniformizing the thickness of the resist solution film is performed by rotating the wafer at a low speed between the resist solution application step S3 and the drying step S5. In this case, it is preferable to start blowing the temperature-controlled gas after the planarization step is completed, simultaneously with the start of the drying step S5 or after a predetermined time has elapsed after the start.

  The above embodiment can be modified in various ways.

  For example, although two temperature control nozzles are provided in the above embodiment, the present invention is not limited to this, and only one or three or more nozzles may be provided. The shape of the discharge port of the temperature control nozzle is not limited to a rectangle, and may be another shape such as a perfect circle, an ellipse, an ellipse, or a rhombus.

  As schematically shown in FIG. 9A, temperature control nozzles (160A, 160B) may be provided at different radial positions (distances from the spin chuck rotation center) r1, r2, respectively. In this case, the temperature adjustment gas supply mechanism is configured to be able to individually control the supply of the temperature adjustment gas to the temperature adjustment nozzle 160A and the temperature adjustment nozzle 160B. In FIG. 9A, symbol “We” indicates the peripheral edge of the wafer, “122ae” indicates the peripheral edge of the upper surface 122a of the spin chuck 122, and “O” indicates the rotation center of the wafer W and the spin chuck.

  As schematically shown in FIG. 9B, a plurality of small-diameter temperature control nozzles (160-1 to 160-n) are provided at different positions in the radial direction, and temperature control gas is supplied to each temperature control nozzle. Valves (164-1 to 164-n) to be controlled may be provided. In this case, select an open valve (164-1 to 164-n) (for example, when applying the first resist, open 164-1 to 164-3 and apply the second resist). The temperature control region can be adjusted by opening (164-2 to 164-4).

  The temperature control nozzle may be movable so that the radial position of the temperature control nozzle can be changed. For example, as shown in FIG. 9C, a guide 166 is provided on the cup base 134, and a linear actuator 167 that moves the temperature adjustment nozzle 160 ′ is provided along the guide 166. The temperature control nozzle side end of the pipe line 162 can be constituted by a flexible tube 162 '.

  If the temperature control region can be changed as shown in FIGS. 9A to 9C, it is convenient when it is necessary to change the temperature control region when the coating apparatus 30 performs various types of coating processes. .

  In the above embodiment, the gas is blown from the temperature control nozzle to the wafer W, but what is blown to the wafer W may be a fluid such as a gas, a liquid, or a gas-liquid mixture. In the above embodiment, the wafer W is locally heated, but may be cooled.

  In the above embodiment, the local temperature adjustment of the wafer W is performed by spraying the temperature-controlled gas. However, the present invention is not limited to this, and the wafer W is locally irradiated with heat rays. It is also possible to adjust the temperature. FIG. 10 schematically shows an example in which a heat ray irradiation device is provided on the back side of the wafer instead of providing the temperature control nozzle. In the example shown in FIG. 10, infrared LED200 is provided as a heat ray irradiation apparatus. The infrared LED 200 is supplied with power from the power source 201. The power source 201 is controlled by a control unit (170) not shown in FIG. When a liquid processing nozzle such as a bevel cleaning nozzle is provided on the wafer back side space (BS) side, the infrared LED 200 and the electrical components (wiring, terminals, etc.) connected thereto are not corroded by the processing liquid. Covering with a suitable shield 202 is preferred. Note that a portion of the shield 202 facing the back surface of the wafer W may be provided with an infrared light transmissive shield 202a.

  Further, instead of the infrared LED 200, a laser irradiation device may be provided as schematically shown in FIG. In this case, a laser light source 210 is provided outside the wafer back surface side space (BS), and laser light generated by the laser light source 210, for example, low-power infrared laser light, is guided to the back surface of the wafer W by the optical fiber 211. it can.

  In the case of the embodiment using the heat ray irradiation apparatus shown in FIGS. 10 and 11, the temperature distribution of the wafer W is adjusted by irradiating the wafer with heat rays in the drying process, as in the embodiment using the temperature control nozzle described above. By doing so, the film thickness distribution of the resist film can be adjusted. In the case of using the heat ray irradiation device, the temperature adjustment region can be configured to be changeable as in the case of using the temperature adjustment nozzle. For example, similarly to the temperature control nozzle shown in FIGS. 9A and 9B, the light projecting side ends of the plurality of infrared LEDs 200 or the plurality of optical fibers 211 are arranged at different positions in the radial direction. Alternatively, the rear surface of the wafer W may be irradiated with heat rays from the light emitting side end portion of the selected infrared LED 200 or optical fiber 211. Further, for example, by using a guide / linear actuator similar to that shown in FIG. 9C, the light emitting side end of the infrared LED 200 or the optical fiber 211 can be moved in the radial direction.

  In the case where a heat ray irradiation apparatus is used, the wafer W can be heated substantially without being affected by the air flow in the wafer backside space (BS), and precise output control is performed by pulse control or the like. This is advantageous in that the amount of heat applied to the wafer W can be precisely adjusted. On the other hand, depending on the atmosphere in the wafer back surface side space (BS), the light irradiation portion may be contaminated, and it may be necessary to periodically clean the light irradiation portion. In this respect, the embodiment using the temperature control nozzle which does not have such a fear is more advantageous.

  In the above embodiment, the coating liquid is a resist liquid. However, the present invention is not limited to this, and the technology according to the above embodiment can be applied to coating liquids other than the resist liquid, for example, an antireflection film, SOG. The present invention can also be applied to application of a coating liquid for forming a (Spin On Glass) film or an SOD (Spin On Dielectric) film. The application target is not limited to the wafer W, and may be another substrate other than the wafer, such as an FPD (flat panel display) or a photomask mask reticle.

  The above embodiments are useful in various coating processes in semiconductor device manufacturing.

Claims (10)

Supplying a coating liquid to the center of the substrate and rotating the substrate, and a coating liquid coating step for covering the entire surface of the substrate with the coating liquid;
A flattening step of flattening the coating liquid applied to the surface of the substrate by rotating the substrate at a rotation speed lower than the rotation speed of the substrate in the coating liquid coating process after the coating liquid coating process; ,
After the planarization step, in a state of stopping the supply of the coating solution, the substrate is rotated at a high rotational speed than the rotational speed of the substrate in the planarization step, a drying step of drying the coating solution, the Prepared,
In the drying step, a temperature in a specific range in the radial direction of the substrate from the back side of the substrate is locally adjusted, and this local adjustment of the temperature is started when or after the drying step is started. The coating film formation method characterized by the above-mentioned. The local adjustment of the temperature, characterized by being carried out by blowing locally the temperature control fluid to a particular range of radial back surface of the substrate, coating film forming method according to claim 1. The coating film forming method according to claim 2 , wherein the temperature control fluid is a gas. The coating method according to claim 3 , wherein the temperature of the gas is in the range of 30 ° C. to 40 ° C. 2. The coating film forming method according to claim 1 , wherein the local adjustment of the temperature is performed by locally irradiating a heat ray to a specific range in a radial direction of the back surface of the substrate. The coating film forming method is executed by a coating apparatus having a spin chuck that holds and rotates the substrate, and a cup that is provided so as to surround the substrate held by the spin chuck. A space surrounded by the substrate held by the spin chuck and a part of the cup is formed, and a peripheral portion of the back surface of the substrate held by the spin chuck and a portion of the cup facing the same. During the execution of the coating film forming method, an air flow that prevents the flow of fluid or microparticles from the outside of the space into the space through the gap is generated in the cup. characterized in that it is formed, a coating film forming method according to any one of claims 1 to 5. A spin chuck that holds and rotates the substrate;
A coating liquid nozzle for supplying a coating liquid to the surface of the substrate held by the spin chuck, a cup provided to surround the substrate held by the spin chuck,
An exhaust mechanism for sucking the inside of the cup and forming an air flow in the cup;
Temperature adjusting means provided so as to be able to locally adjust the temperature in a specific range in the radial direction of the substrate from the back side of the substrate held by the spin chuck;
A coating liquid supply mechanism for supplying the coating liquid to the coating liquid nozzle;
A control unit that controls at least the operation of the spin chuck, the coating liquid supply mechanism, and the temperature adjusting means,
The controller is
A coating liquid coating step of supplying the coating liquid from the coating liquid nozzle to the center of the substrate and rotating the substrate by the spin chuck to cover the entire surface of the substrate with the coating liquid;
After the coating liquid coating step, the spinner rotates the substrate at a rotation speed lower than the rotation speed of the substrate in the coating liquid coating step to flatten the coating liquid coated on the surface of the substrate. Conversion process,
After the planarization step, with the supply of the coating solution from the coating solution nozzle stopped, the substrate is rotated at a rotational speed higher than the rotational speed of the substrate in the planarization step by the spin chuck, and the coating is performed. A drying step of drying the liquid;
Is executed,
In the drying step, the local temperature adjustment by the temperature adjusting means is performed , and the local temperature adjustment is controlled to start when or after the drying step is started. An applicator characterized by. The temperature adjusting means has a discharge port that opens near the back surface of the substrate held by the spin chuck, and the temperature adjusting fluid that blows the temperature adjusting fluid locally in a specific range in the radial direction of the back surface of the substrate The coating apparatus according to claim 7 , comprising a nozzle. The coating apparatus according to claim 7 , wherein the temperature adjusting unit includes a heat ray irradiating device that irradiates a heat ray locally in a specific range in the radial direction of the back surface of the substrate held by the spin chuck. A spin chuck for holding and rotating the substrate, a coating liquid nozzle for supplying a coating liquid to the substrate held by the spin chuck, and a specific range in the radial direction of the substrate from the back side of the substrate held by the spin chuck Temperature adjusting means provided so as to locally adjust the temperature of the coating liquid, a coating liquid supply mechanism for supplying the coating liquid to the coating liquid nozzle, at least the spin chuck, the coating liquid supply mechanism, and the temperature In a coating apparatus comprising a control unit comprising a computer for controlling the operation of the adjusting means, at least a computer-readable program storing a program for controlling the operations of the spin chuck, the coating liquid supply mechanism, and the temperature adjusting means A recording medium,
By executing the program by the computer, the computer controls the spin chuck, the coating liquid supply mechanism, and the temperature adjusting means,
A coating liquid coating step of supplying the coating liquid from the coating liquid nozzle to the center of the substrate and rotating the substrate by the spin chuck to cover the entire surface of the substrate with the coating liquid;
After the coating liquid coating step, the spinner rotates the substrate at a rotation speed lower than the rotation speed of the substrate in the coating liquid coating step to flatten the coating liquid coated on the surface of the substrate. Conversion process,
After the planarization step, with the supply of the coating solution from the coating solution nozzle stopped, the substrate is rotated at a rotational speed higher than the rotational speed of the substrate in the planarization step by the spin chuck, and the coating is performed. A drying step of drying the liquid;
As well as
In the drying step, the local temperature adjustment by the temperature adjusting means is performed , and control is performed so that the local temperature adjustment is started when or after the drying step is started. A recording medium characterized by the above.

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