This invention relates to a coating apparatus and a coating method of coating a substrate with a chemical such as a resist.
Conventionally, as a technique of coating a substrate such as a semiconductor wafer (hereinafter, wafer), a glass substrate for a liquid crystal display and a substrate for a color filter, with a chemical, a spin coating method has been widely used in order to make substantially uniform the thickness of a coated film and to make thinner the same.
Given herein as an example to describe the spin coating method is a case where a resist liquid is applied to a wafer. At first, in a chamber including a spin chuck on which a wafer can be placed, air is supplied from an upper part of the chamber, and the air is discharged from a lower part of the chamber. Thus, a down flow of air for preventing scattering of particles is formed in the chamber. Following thereto, a wafer is placed on the spin chuck, and the wafer is horizontally held. Thereafter, a resist liquid is supplied to a central portion of the wafer, from a nozzle disposed above the wafer, while the wafer is being rotated via the spin chuck at about 2000 rpm about the vertical axis.
The resist liquid that has been supplied onto the wafer is spread out by a centrifugal force from the central portion of the wafer W to a circumferential portion thereof. Then, by reducing the rotational speed of the wafer to, e.g., 100 rpm, the spread-out resist liquid is leveled. After this leveling, the rotational speed of the wafer is increased to, e.g., about 2500 rpm, so that the excessive resist liquid on the wafer is spun off and removed. In addition, since a solvent contained in the resist liquid on the wafer is exposed to an airflow which is generated on the wafer by the rotation of the same, almost all of the solvent is evaporated within about 10 seconds from the time when the rotational speed was increased after the leveling. After the solvent was evaporated, the wafer is continuously rotated for a while, e.g., for about 1 minute from the time when the resist liquid was supplied. Thus, the resist liquid is dried, and a resist film is formed on the wafer.
Recently, there has been technical demand for improving such a coating method. In particular, further reduction in thickness of the coated film and reduction in time period required for the coating process have been desired. In the aforementioned spin coating method, in order to achieve the reduction in thickness of the coated film and also the reduction in the process period, it can be considered to increase the rotational speed of the substrate. However, when a resist liquid is applied to a large wafer, such as a 12-inch wafer, an increase in the rotational speed of the wafer may invite, as shown in
These wrinkles are called “windmill-like tracks”. The “windmill-like tracks” are generated because non-uniformity of airflow-speed in the circumferential direction of the substrate, which is caused at an area where a speed-boundary layer of the air on the substrate changes from a laminar flow to a transition flow, is transferred to the resist-film thickness through an evaporation step. This airflow-speed non-uniformity is a scientifically famous phenomenon called “Ekman spin”. This phenomenon, which is described in detail in J. Appl. Phys. 77(6), 15 (1995), pp. 2297-2308, is a natural phenomenon that appears when the Re (Reynolds) number of a rotating substrate exceeds a certain value. The Re number is calculated by the following expression (1) in which a distance from the center of the substrate is r (mm), an angular speed of the substrate is ω (rad/s), and a coefficient of kinematic viscosity of a gas around the substrate is ν (mm2/s).
Re number=rω2/ν (1)
On the surface of a wafer which is being rotated, for example, a laminar flow is formed at an area where the Re number<80000, a transition flow is formed at an area where 80000<Re number<3×105, and a turbulent flow is generated at an area where the Re number>3×105.
As shown in the expression (1), the Re number increases in proportion to r. Thus, as shown in
When the resist liquid is exposed to the turbulent flow at the step in which the solvent is evaporated, the solvent on the surface of the resist liquid is evaporated too fast. In this case, there is formed a so-called “crust-like structure” in which a thin film of a polymer of the resist liquid is formed on the surface of the coated resist film, with the solvent remaining below the thin film. In this case, there is a possibility that the thickness of the overall structure is larger than the thickness of the area on which the laminar flow is formed.
In view of the above, the Re number has to be decreased in order to widen an area on which the resist film can have the uniform thickness.
On the other hand, the value of a coefficient of kinematic viscosity ν of a gas can be calculated from the following expression (2). In the expression (2), μ represents a coefficient of viscosity (Pas·s) of a gas around a wafer, and ρ represents a density (kg/m3) of the gas.
ν=μ/ρ (2)
In the expression (1), when the angular speed of the wafer is kept constant, the radius of the laminar flow, i.e., the value of the r in the expression (1) when the Re number takes 80000, is decreased by decreasing the value of the ν. Namely, as shown in
Thus, in order to widen the area on which the thickness of the resist film can be made uniform, the value of the gas coefficient of kinematic viscosity ν is preferably increased. In order to increase the value of the ν, it is preferable to use a gas of a lower value of the density ρ, which is understandable from the expression (2).
When the spin coating method is performed, with a view to preventing scattering of the coating liquid, a cup having an opened upper part is generally located around a substrate placed on a spin chuck. JP5-283331A discloses a coating apparatus adapted to perform a rotational coating in which the upper part of such a cup is covered with a lid, and an air in the space surrounded by the cup and the lid is replaced with an He (helium) gas. As another coating apparatus, JP5-283331A and JP61-150126A respectively disclose a coating apparatus adapted to perform a rotational coating in which there is disposed a lid at a position several millimeters above a substrate placed on a spin chuck, such that the lid is opposed to the substrate so as to cover the overall surface of the substrate, and an air in the space between the substrate and the lid is replaced with a gas such as an He gas or the like whose density is lower than that of the air. With the use of the coating apparatuses described in these publications to replace the air around the substrate with an He gas, the value of the ν can be increased as much as about 9 times.
In addition, JP3-245870A discloses a coating apparatus adapted to perform a rotational coating in which a down flow of a mixed gas formed of an He gas and an air is formed in a chamber in which a spin chuck is installed, so that an air in the chamber is replaced with the mixed gas.
However, in the coating apparatus described in JP5-283331A in which the air in the space surrounded by the lid and the cup is replaced with an He gas, a time lag may occur between a time point at which the supply of the He gas is started and a time point at which a sufficient amount of the He gas is stored so as to lower the gas density in the space surrounded by the lid and the cup.
In addition, in order to rapidly discharge a mist-like coating liquid that has been scattered with the rotation of the substrate, the general rotational coating apparatus is equipped, in the vicinity of a rotating substrate, with a gas-discharging mechanism capable of discharging the gas (mist) at a volume of displacement (exhaustion) not less than 1 m3/min.
Thus, when a coating process is performed by the rotational coating apparatus described in JP5-283331A, it is necessary, before the coating process, to replace an atmosphere in the space surrounded by the cup and the lid with an He gas, and further it is necessary to continue the supply of the He gas at a flow rate corresponding to the volume of displacement during the coating process. That is, a required amount of the He gas throughout the coating process is increased, which results in increase in cost.
With respect also to the coating apparatus described in JP3-245870A, it is necessary to supply the mixed gas containing an He gas into the whole chamber. Thus, similar to the coating apparatus described in JP5-283331A, a time lag may occur before the mixed gas is fully supplied, and thus an increasing amount of the He gas to be used may increase the cost.
As described in JP5-283331A and JP61-150126A, when the lid that covers the overall surface of the rotating substrate is provided, there is a possibility that the coating liquid that has been scattered and made misty by the rotation of the substrate adheres to the lid and becomes particles, and that the particles fall thereform and adhere onto the substrate. In order to remove such adherend of the lid, so as to prevent the adhesion of the particles to the substrate, the lid has to be washed. However, such a washing process requires additional cost. Moreover, since the lid covers the overall surface of the substrate, the aforementioned down flow cannot be formed around the substrate. Thus, there still remains a possibility that particles are scattered around the substrate.
In view of the aforementioned problems and in order to solve them effectively, we accomplished the present invention. Accordingly, an object of the present invention is to provide a coating apparatus and a coating method wherein generation of windmill-like tracks is effectively inhibited by enlarging an area in which a laminar flow is formed, when a spin coating with a chemical is conducted to a substrate.
The coating apparatus of the present invention is a coating apparatus comprising: a substrate-holding part that holds a substrate horizontally; a chemical nozzle that supplies a chemical to a central portion of the substrate horizontally held by the substrate-holding part; a rotation mechanism that causes the substrate-holding part to rotate in order to spread out the chemical on a surface of the substrate by a centrifugal force, for coating the whole surface with the chemical; a gas-flow-forming unit that forms a down flow of an atmospheric gas on the surface of the substrate horizontally held by the substrate-holding part; a gas-discharging unit that discharges an atmosphere around the substrate; and a gas nozzle that supplies a laminar-flow-forming gas to the surface of the substrate, the laminar-flow-forming gas having a coefficient of kinematic viscosity larger than that of the atmospheric gas; wherein the atmospheric gas or the laminar-flow-forming gas are supplied to the central portion of the substrate.
Herein, to supply the laminar-flow-forming gas to the surface of the substrate is not limited to the supply of the gas to the substrate from vertical directions, but includes the supply of the gas from diagonal directions, and further includes the supply of the gas from horizontal directions along the surface of the substrate.
According to the above invention, when the surface of the substrate, which has been spin-coated with the chemical, is spin-dried, while forming the down flow of the atmospheric gas, by supplying the laminar-flow-forming gas having a coefficient of kinematic viscosity larger than that of the atmospheric gas, the laminar-flow-forming gas is mixed into the gas flow of the atmospheric gas spreading outward along the surface of the substrate. Thus, the coefficient of kinematic viscosity of the gas flow formed on the surface of the substrate is increased. Since a radius of a laminar flow to be formed on the surface of the substrate is in proportion to the coefficient of kinematic viscosity of the gas, a laminar-flow area on the surface of the substrate is widened. Thus, generation of windmill-like tracks on the surface of the substrate can be restrained to thereby perform an improved coating process.
In addition, since the supply of the laminar-flow-forming gas to the surface of the substrate is performed by the nozzle, the consumption of the laminar-flow-forming gas can be reduced, as compared with an art for replacing the whole atmosphere, in which the substrate is placed, with the laminar-flow-forming gas, and thus a long time period for replacing the gas can be saved. In addition, since the substrate is located in the down flow of the atmosphere, and the atmosphere is discharged from around the substrate, there can be eliminated the problem associated with a method in which a lid is provided above the substrate to form a closed space. Namely, there is no possibility that mist scattered form the substrate adheres to the lid and becomes particles.
In the present invention, for example, the gas nozzle has a gas ejecting part that opens in a radial direction of the substrate from a position above the central portion of the substrate. Alternatively, the gas nozzle has a gas ejecting part consisting of a large number of holes arranged in a radial direction of the substrate from a position above the central portion of the substrate.
Preferably, the gas nozzle has a porous body. In addition, preferably, a flow rate ejected from the gas nozzle is larger at an area closer to a peripheral edge of the substrate. For example, preferably, depending on the position, by a distance thereof from the central portion of the substrate in the direction toward the peripheral portion thereof, the flow rate of the gas being ejected from the gas nozzle is larger in a stepwise or continuous manner.
In addition, for example, the gas nozzle is configured to supply the laminar-flow-forming gas both to the central portion of the substrate and to an area of the substrate apart from the central portion thereof. Alternatively, the gas nozzle is configured to supply the laminar-flow-forming gas to an area of the substrate apart from the central portion thereof, and the central portion of the substrate is adapted to be exposed to the down flow of the atmospheric gas.
In addition, for example, a second gas nozzle is provided independently from the gas nozzle, the second gas nozzle being configured to supply a laminar-flow-forming gas or the atmospheric gas to the central portion of the substrate.
Alternatively, the coating method of the present invention is A coating method of a substrate with a chemical, the coating method comprising: a step of causing a substrate-holding part to hold a substrate horizontally; a step of discharging an atmosphere around the substrate while forming a down flow of an atmospheric gas on a surface of the substrate held by the substrate-holding part; a coating step, by supplying a chemical from a chemical nozzle to a central portion of the substrate, causing the substrate-holding part to rotate, and thus spreading out the chemical on the surface of the substrate by a centrifugal force for coating the whole surface with the chemical; and a drying step, by supplying a laminar-flow-forming gas from a gas nozzle to the surface of the substrate under a state wherein the substrate is caused to rotate, and supplying the atmospheric gas or the laminar-flow-forming gas to the central portion of the substrate, so as to dry the chemical, after the coating step, the laminar-flow-forming gas having a coefficient of kinematic viscosity larger than that of the atmospheric gas.
In this method, a timing at which the laminar-flow-forming gas is supplied to the surface of the substrate and the atmospheric gas or the laminar-flow-forming gas are supplied to the central portion of the substrate is, for example, the same as or prior to a timing at which the substrate starts to rotate with a rotation number suitable for drying the chemical.
As an embodiment of the present invention, a coating apparatus 2 which coats a wafer W as a substrate with a resist (liquid) as a chemical (liquid) is explained.
The reference number 31 depicts a spin chuck as a substrate holder, disposed in the housing 20. The spin chuck 31 is capable of sucking and absorbing a central portion of a rear surface of a wafer W so as to hold the wafer W horizontally. The spin chuck 31 is connected to a drive part 33 through a shaft part 32. With holding a wafer W, the spin chuck 31 can be rotated about a vertical axis and can be moved upward and downward, through the drive part 33.
The reference number 34 depicts a cup having an upper opening, which is disposed on an outside of a peripheral edge of a wafer W held by the spin chuck 31 to surround the wafer W. An upper part of a side peripheral wall of the cup 34 is inclined inward. On a bottom side of the cup 34, a liquid-receiving part 35 of a recessed shape is disposed below the peripheral edge of the wafer W to cover all the circumference of the wafer W. The liquid-receiving part 35 is divided into an outside area and an inside area. Formed in a bottom part of the outside area is a drain port 36 for discharging a stored resist.
Two gas-discharging ports 37 and 38 are formed in a bottom part of the inside area. Ends on a branched side of a gas-discharging pipe 39 are connected to each of the gas-discharging ports 37 and 38. The other end on a merged side of the gas-discharging pipe 39 is connected to a gas-discharging unit 30, such as an air displacement pump, via a valve V1. Thus, by adjusting an opening degree of the valve V1, for example, a gas in the cup 34 can be discharged at a volume of displacement between 1 m3/min and 3 m3/min. When the gas is discharged by opening the valve V1, an He gas which has been ejected onto the wafer W and an air which has been supplied around the wafer W flow into the gas-discharging pipe 39 via the gas-discharging ports 37 and 38 so as to be removed from the housing 20, which is described below. In addition, along with the thus formed discharged-gas current, a mist-like resist, which has been scattered by the rotation of the wafer W, can be discharged from the drain port 36 through the liquid-receiving part 35.
A circular plate 3A is located below the wafer W held by the spin chuck 31. Further, a ring member 3B having a chevron cross-section is provided so as to surround an outside of the circular plate 3A. Furthermore, disposed on an outer edge of the ring member 3B is an end plate 3C which is extended below to enter the outside area of the liquid-receiving part 35. Thus, a resist falling from the wafer W can be moved along the surfaces of the ring member 3B and the end plate 3C so as to be guided into the outside area of the liquid-receiving part 35.
Next, structures of nozzles disposed in the housing 20 are described also with reference to
In
The reference number 51 depicts a gas nozzle that ejects an He gas as a laminar-flow-forming gas to a wafer W. Also with reference to
Connected to the gas inlet port 52 of the gas nozzle 51 is one end of a gas supply pipe 54. The other end of the gas supply pipe 54 is connected, via a valve V3 and a gas-flow-rate control part 55, to a gas supply source 56 in which an He gas is stored. By opening the valve V3, the He gas flows from the gas supply source 56 into the gas supply pipe 54. While a flow rate of the He gas is being controlled by the gas-flow-rate control part 55, the He gas flows into the gas channel 53 of the gas nozzle 51. The He gas, which has flown into the gas channel 53, flows into the gas channel 503 of the body part 501 and moves outward the nozzle 51 through the gas channel 503. As described above, the gas channel 503 is formed to have the mesh structure in the whole body part 501. Thus, as shown by the arrows in
As shown in
The ejecting position for the He gas is not limited to the above position. A center of the gas nozzle 51 in a longitudinal direction thereof may be set to be positioned above the central portion of the wafer W. However, it is necessary that the He gas is supplied to the central portion of the wafer W during an initial stage of a step of drying the resist, e.g., for about 10 seconds after the start of the drying step, which is described below. An air flowing downward toward the wafer W spirally flows, by a centrifugal force of the wafer W, from the central side of the wafer W toward the peripheral side of the wafer W. When an He gas is ejected to the center of the wafer W, the ejected He gas merges into the air flow and runs through toward the peripheral side of the wafer W. Thus, a layer of a mixed gas containing the air and the He gas is formed all over the surface of the wafer W. A coefficient of kinematic viscosity of this layer is higher than a coefficient of kinematic viscosity of the sole air. Therefore, generation of transition flow on the wafer W can be restrained.
When the gas nozzle 51 is moved to the position at which the He gas is ejected, a height h from a lower end of the nozzle 51 to the surface of the wafer W, which is shown in
As shown in
In addition, although not shown, a gas-discharging part that discharges any gas in the housing 20 is disposed at a lower part of the housing 20. As described above, an air is supplied from the filter 61, and the gas-discharging part discharges, independently from the gas-discharging unit 30, the air at a predetermined flow rate, for example, so that a down flow of the air can be formed in the housing 20.
Next, an operation of the coating apparatus 2 in this embodiment is described with reference to
At first, the valves V4 and V1 are opened, and an air is discharged from the gas-discharging part at the lower part of the housing 20, so that down flows of the air are formed in the housing 20 which are indicated by the solid arrows in
Subsequently, the wafer W held on the spin chuck 31 is rotated through the drive part 33 about a vertical axis at 2000 rpm, for example. Thus, the down flow of the air falling upon the wafer W is spirally spread out on the rotating wafer W toward the peripheral portion thereof because of the centrifugal force. Then, the valve V2 is opened, so that a resist 4A supplied from the resist supply nozzle 41 is ejected to the central portion of the wafer W. The resist 4A that has been supplied to the wafer W is spread out from the central portion of the wafer W toward the peripheral portion thereof by a so-called spin coating for extending the resist by the centrifugal force (
After the overall surface of the wafer W is covered with the resist 4A, the valve V2 is closed so that the supply of the resist 4A from the resist supply nozzle 41 is stopped, and the rotational speed of the spin chuck 31 is lowered to, e.g., 100 rpm. Thus, leveling of the coated resist 4A (to level the coated resist so as to make uniform a thickness thereof) is performed. In addition, at this time, the resist supply nozzle 41 is retracted via the drive part 46 from the position above the center of the wafer W, and the gas nozzle 51 is moved to the aforementioned He-gas ejecting position (
After the movement of the gas nozzle 51, the valve V3 is opened, and, while a flow rate of an He gas to be supplied from the He-gas supply source 56 to the gas supply pipe 54 is being controlled by the flow-rate control part 55, the He gas is ejected in a shower-like manner from the peripheral surface of the porous body as the gas nozzle 51. The He gas is supplied in the radial direction of the wafer W including the central portion thereof, at a flow rate of, e.g., 40 L/min. Simultaneously with the ejection of the He gas or slightly after the ejection thereof, the rotational speed of the wafer W is increased to, e.g., 2600 rpm, so that the resist 4A is spun out and dried (see,
After a time sufficient for the solvent in the resist to be evaporated has passed, e.g., after further 10 seconds have passed, the valve V3 is closed to stop the supply of the He gas, while the rotation of the wafer is maintained as it is (see,
The coating apparatus 2 in this embodiment performs the spin coating of the resist on the surface of the wafer W. Then, in order to dry the resist film, while forming the down flow of the air, the coating apparatus 2 supplies the He gas as a laminar-flow-forming gas, which has a coefficient of kinematic viscosity larger than that of the air, in the radial direction of the wafer W including the center of the surface thereof, before the wafer W is rotated at the rotational speed (2600 rpm in this embodiment) suitable for drying the resist film. Thus, the He gas is mixed into the air flowing downward toward the central portion of the wafer W and spreading out along the surface of the wafer W from the central portion to the peripheral portion thereof, and the thus mixed gas is diffused all over the surface of the wafer W. Therefore, the coefficient of kinematic viscosity of the gas flow on the surface of the wafer W becomes 1.5 to 4 times larger than that of the sole air. Since a radius of the laminar-flow area formed on the surface of the wafer W is in proportion to a coefficient of kinematic viscosity of the gas, the laminar-flow area is widened so that even a 12-inch wafer can be completely covered within the laminar-flow area.
In addition, the solvent of the resist film actively evaporates immediately after the rotational speed of the wafer W is increased to the rotational speed for drying. At the same time, in the spiral flow flowing along the surface of the wafer W, a gas flow close to the surface of the wafer W is formed by the gas supplied to the central portion of the wafer W, and there is stacked, on the gas flow, another gas flow of the gas supplied to a portion on an outside of the central portion of the wafer W. Thus, a finished condition of the resist film is generally determined by the flow of the gas supplied to the central portion of the wafer W immediately after the rotational speed of the wafer W reaches the rotational speed for drying. In this embodiment, when the wafer starts to rotate at the rotational speed for drying, the He gas has been supplied to the central portion of the wafer W. Thus, generation of windmill-like tracks on the surface of the wafer W can be effectively restrained, to thereby realize an improved coating process. Namely, according to this embodiment, even when a larger wafer W is used, generation of windmill-like track can be restrained or avoided.
Further, since the supply of the laminar-flow-forming gas to the surface of the wafer W is performed by the gas nozzle, consumption of the gas can be reduced as compared with a case in which the whole atmosphere, where the wafer W is placed, is replaced with the He gas or the like. In addition, a long time period for the replacement of the gas can be saved. Moreover, the wafer W is located in the down-flow atmosphere, and the air around the wafer W is discharged. Thus, there can be eliminated the problem associated with a method in which a lid is disposed above the wafer W so as to form a closed space, i.e., there is no possibility that mists scattered from the wafer W adhere to the lid to become particles.
Furthermore, since the gas nozzle 51 is configured to eject a gas through the porous body (voids formed by the porous body serve as a gas ejecting part), the He gas can be uniformly supplied to the surface of the wafer W in a shower-like manner. Thus, a pressure distribution of the He gas on the surface of the wafer W can be made uniform. Also for this reason, the dried resist film can have a smooth surface, which improves a finish of drying.
The atmospheric gas stored in the supply source 64 is not limited to the air. For example, a nitrogen gas or an Ar (argon) gas may be stored, and a down flow of the nitrogen gas or the Ar gas may be formed in the housing 20.
In addition, the gas ejected from the gas nozzle 51 as the laminar-flow-forming gas may be any gas that has a coefficient of kinematic viscosity larger than that of another gas 30 used as the atmospheric gas. Thus, for example, a gas such as hydrogen may be used in place of the He gas. In addition, as the laminar-flow-forming gas, a mixed gas formed of an He gas and an air, or a mixed gas formed of an He gas and a nitrogen gas, may be used.
In the above-described embodiment, the He gas is supplied when the rotational speed of the wafer W is increased, after the resist that has been supplied to the wafer W is leveled. However, as long as the layer of the mixed gas including the He gas and the air is formed on the surface of the wafer W before almost all the solvent is evaporated after the rotational speed of the wafer W was increased after the leveling, the effect of the present invention can be achieved. Thus, it is possible to start the ejection of the He gas to the wafer W in the course of the leveling and to stop the ejection after almost all the solvent is evaporated. However, as in the above embodiment, the case in which the rotational speed of the wafer W is increased for the drying step after the leveling and then the ejection of the He gas is started at the time when or immediately before the drying step is started, is preferable to the case in which the ejection of the He gas to the wafer W is started during the leveling. This is because an effect caused by the He gas on a temperature of the wafer W can be restrained, so that there can be obtained a resist film having a more improved in-plane uniformity.
Suppose that a planar area (size) of the wafer W to be coated is S1 and a projection area of the nozzle 51 on the wafer when the He gas is supplied to the wafer W is S2, the projection area S2 equals to an area of the lower end surface of the nozzle 51, in the case of this embodiment. The smaller a ratio of S2 relative to S1 (S2/S1) is, the less adhesion of the resist, which has been scattered and made misty during the rotational coating process, can be caused. Namely, since the resist can be prevented from falling on the wafer W as particles, a smaller ratio of S2 relative to S1 (S2/S1) is preferred. Thus, even when the value of S2 is increased, S2/S1 is preferably not more than ½.
As the gas nozzle, it is preferable to use the gas nozzle 51 made of a porous body, as described above. However, gas nozzles having structures shown in
The gas nozzle for supplying an He gas may be a gas nozzle 7 having a structure as shown in
As shown in
Alternatively, the gas nozzle may have a structure as shown in
Alternatively, the gas nozzle may have a structure as shown in
Herein, at a position further from the central portion of the wafer W and thus closer to the peripheral portion thereof, the length of the wafer W in the circumferential direction is greater. Thus, in order to uniformize a density of the He gas within the plane of the wafer W, it is preferable to make larger the flow rate of the He gas depending on the position, by a distance thereof from the central portion of the wafer W toward the peripheral portion thereof. To be specific, it is preferable to supply an He gas to the wafer W by means of a gas nozzle 8 as shown in
In addition, a gas nozzle 83 as shown in
In addition, as shown in
In order to increase the ejection flow rate of the He gas at the position closer to the peripheral side of the wafer W, it is adoptable to, for example, make each gas nozzle such that the hole of the ejecting part arranged closer to the peripheral side has a greater diameter, in addition to adoption of the structure in which the holes of the same bore arranged closer to the peripheral side have a greater arrangement density. Furthermore, in place of the aligned small holes, there may be formed a slit extending in a longitudinal direction of the gas supply part (e.g., gas supply part 72). In this case, in order to increase the ejection flow rate of the He gas at the position closer to the peripheral side of the wafer W, a width of the slit is preferably enlarged in a stepless or stepwise manner toward the peripheral edge of the wafer W.
Alternatively, in the gas nozzles 83 and 85 shown in
In addition, when an He gas is supplied to the wafer W by the aforementioned gas nozzle 65, the supply position of the He gas may be moved from the central portion toward the peripheral portion. Specifically, as shown in
Not limited to the case in which a resist is supplied to a substrate to deposit thereon a film, the coating apparatus 2 in this embodiment may be used when a substrate is coated with a chemical containing a precursor of an insulation film so as to deposit on the substrate the insulation film such as a silicon oxide film. Namely, the coating apparatus 2 in this embodiment can be widely applied to any case in which a substrate is coated with a general chemical.
In Example 1, there was prepared a coating apparatus in which, in place of a resist, an oil liquid formed by mixing a commercially available liquid ink and a commercially available neutral detergent (trade name: mama lemon) at a ratio of 1:1 was stored in a supply source 44, and the thus formed oil liquid in place of a resist was supplied from a liquid supply nozzle 41 to a wafer W. The other structures of the coating apparatus are the same as those of the aforementioned coating apparatus 2.
In accordance with the procedure for applying a resist in the aforementioned embodiment, the oil liquid was applied onto a wafer W, and an oil film was formed by the oil liquid.
As the wafer W, a 300-mm wafer (12-inch wafer) was used (all the wafers W used in the following examples have a diameter of 300 mm). As a gas nozzle for ejecting an He gas, the gas nozzle 65 as shown in
The thus formed oil film was evaluated, and neither windmill-like track nor ejection trajectory of the He gas was observed on the surface.
Next, as Example 2, an oil film was formed by supplying an oil liquid to a wafer W, in the same manner as Example 1, with the use of the gas nozzle 74 as shown in
In Example 2, there were performed a coating process with a value of the flow rate Qin of the He gas to be supplied to the wafer W being set at 19 L/min, and a coating process with a value of the flow rate Qin being set at 38 L/min, and thus formed oil films were evaluated. When the flow rate Qin was set at 19 L/min, windmill-like tracks were formed on the oil film. On the other hand, when the flow rate Qin was 38 L/min, neither windmill-like track nor ejection trajectory of the He gas was observed on the oil film.
Next, as Example 3, with the use of the gas nozzle 7 as shown in
As shown in
Next, as Example 4-1, by using the coating apparatus 2 shown in the aforementioned embodiment, an ArF resist film was deposited on a wafer W in accordance with substantially the same procedure as in the above embodiment. At the drying step after the leveling of the dropped resist, as shown in
In addition, as Example 4-2, a resist film was deposited on a wafer W in accordance with substantially the same procedure as in the above Example 4-1. However, as shown in
Next, as Example 4-3, a resist film was deposited on a wafer W in substantially the same manner as the above Examples 4-1 and 4-2. In Example 4-3, the gas nozzle 92 was used in place of the gas nozzle 51. The gas nozzle 92 has the same structure as that of the gas nozzle 51, excluding that the peripheral wall of the gas nozzle 92 is longer than that of the gas nozzle 51. As shown in
Further, as Example 4-4, a film-deposition process of a resist film was performed similarly to Example 4-3, by using the gas nozzle 92 similar to Example 4-3. However, as shown in
Following thereto, as Comparative Example 4-1, a resist film was deposited on a wafer W by using the coating apparatus 2, similarly to Example 4-1. However, as shown in
In addition, as Example 4-2, as shown in
In Examples 4-1 to 4-3, as shown in
In Example 4-4, as shown in
As to the wafers W of Comparative Examples 4-1 and 4-2, as shown in
Thus, it was confirmed that, from Examples 4-1 to 4-4 and Comparative Examples 4-1 and 4-2, by supplying an He gas to the area including the central portion, the coefficient of kinematic viscosity of the gas in the vicinity of the surface of the wafer W was raised and the area in which the laminar flow was formed was enlarged, so that formation of windmill-like tracks could be prevented, while the area in which the resist film of a uniform thickness was formed could be widened.
Further, as apparent from Examples 4-1 to 4-4, the ejection trajectory of the He gas 93 in Examples 4-1 to 4-3 can be improved by adjusting the distance between the gas nozzle 51 and the wafer W. The ejection trajectory 93 was formed because a large amount of the He gas was supplied to the central portion to apply a pressure thereto. Thus, it is considered that the ejection trajectory 93 can be improved by adjusting the flow rate of the He gas.
Further, resist films were deposited on wafers W with the use of the coating apparatus 2, with the timing of starting supply of an He gas and the timing of stopping the supply of the He gas being changed.
As shown in the graph, the resist was dropped on the wafer W that was being rotated at the rotational speed of 2000 rpm. After 3 seconds had passed from the dropping of the resist, the rotational speed of the wafer W was decreased to 100 rpm so as to perform the leveling of the resist for 10 seconds. Thereafter, the rotational speed of the wafer W was increased to 2600 rpm so as to perform the drying of the resist for 60 seconds. Similarly to the above embodiment, by using the gas nozzle 51 as a gas nozzle, an He gas was radially ejected from the central portion of the wafer W to the peripheral portion thereof. The flow rate of the He gas at the drying step was 40 L/min. The distance between the lower end of the gas nozzle 51 and the wafer W, which is indicated by h in
Under the conditions as described above, as Example 5-1, the ejection of the He gas was started 5 seconds after the start of the leveling, and the ejection of the gas was stopped 10 seconds after the start of the drying step. As Example 5-2, the He gas was ejected simultaneously with the start of the leveling step, and the supply of the He gas was stopped 10 seconds after the start of the drying step. As Example 5-3, the He gas was ejected 5 seconds before the start of the leveling step, and the supply of the He gas was stopped 10 seconds after the start of the drying step. As Example 5-4, the He gas was ejected simultaneously with the start of the drying step, and the supply of the He gas was stopped 5 seconds after the start of the ejection thereof. As Example 5-5, the He gas was ejected simultaneously with the start of the drying step, and the supply of the He gas was stopped 10 seconds after the start of the ejection thereof. As Example 5-6, the He gas was ejected simultaneously with the start of the drying step, and the supply of the He gas was stopped 15 seconds after the start of the ejection thereof.
The results were as follows. In Examples 5-1 to 5-3 and Examples 5-5 and 5-6, as shown in
Next, in the coating apparatus 2, resist films were deposited on wafers W in accordance with the procedure as described above, with the height of the gas nozzle 51 (height indicated by h in
The table of
Following thereto, in order to confirm the effect of the present invention, films were deposited in Comparative Example 7-1 and Examples 7-1 to 7-3.
Next, as Comparative Example 7-1, as shown in
Subsequently, as Example 7-1, films were deposited on wafers W at various rotational speeds in accordance with the same procedure and under the same process conditions as those of Comparative Example 7-1, excluding that the flow rate of the He gas was set at 30 L/min.
In addition, as Example 7-2, as shown in
Further, as Example 7-3, as shown in
The results of Comparative Example 7-1 and Examples 7-1 to 7-3 are shown in the table of
From the result of Example 7-2, it can be understood that, even when the He gas is not supplied to the central portion of the wafer W as in the aforementioned Examples 6-1 to 6-4, the He gas can restrain the generation of windmill-like tracks. That is to say, under a state in which a laminar flow is formed in a space above the center of the wafer W and the surface of the wafer is filled with an atmospheric gas (e.g., air) without the He gas, it is considered that the generation of windmill-like tracks can be restrained by supplying the He gas from a position more upstream (closer to the center of the wafer) than a position where a transition flow is generated.
In the surfaces of the wafers W in the aforementioned Comparative Example 4-1 and Comparative Example 4-2, as shown in
In addition, as in Example 7-3, when the He gas is supplied from the gas nozzle 95 and the nozzle 101 to the different positions of the wafer W, i.e., to the central portion and the area outside the central portion in this example, parameters, such as the distances from the gas nozzle 95 and the nozzle 101 for supplying the He gas to the wafer W, and the flow rates of the gas supplied from the respective nozzles, can be independently adjusted. Thus, uniformity of the film-thickness of the resist can be more improved. Accordingly, there can be restrained formation of the ejection trajectory of the He gas 93 on the central portion of the wafer W, which was seen in Examples 4-1 to 4-3. As clearly understood from Example 7-2, an air in place of the He gas may be ejected from the gas nozzle 101.
Next, the wafers W processed in Example 6-3 and Example 7-3 at the same rotational speed (2200 rpm) were selected, and the film thicknesses of the resist on the wafers W were measured.
The flow rates of the He gas shown in the above-described Examples and Comparative Examples were measured by a simple (portable) flowmeter for measuring flow rates of an air and an N2 gas. Thus, the actual flow rates of the He gas are considered to be about 1.4 times larger than the flow rates as has been shown.
Number | Date | Country | Kind |
---|---|---|---|
2005-362076 | Dec 2005 | JP | national |
2006-126802 | Apr 2006 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2006/325060 | 12/15/2006 | WO | 00 | 6/13/2008 |