JP3554381B2 - Method for forming coating film and spin coating device - Google Patents

Description

[0001]
[Industrial applications]
The present invention relates to a method and a spin coating apparatus for forming a coating film in which generation of particles is suppressed, and more particularly, to improving the cleaning efficiency of a coating liquid on an outer peripheral portion of a wafer and particles by the coating liquid attached to the outer peripheral portion of the wafer. The present invention relates to a method for forming a coating film and a spin coating device, in which generation of particles is suppressed, which can prevent the occurrence of particles and can form a coating film having high in-plane uniformity without steps.
[0002]
[Prior art]
In a manufacturing process of a semiconductor integrated circuit, as a manufacturing process using a coating film, for example, a coating process of a photoresist solution in a photolithography technology, a coating process of a solution containing a silicon compound as a main component in a planarization technology, such as an SOG process, or the like There is. Conventionally, such a coating film is formed by a method such as spin coating, spray coating, and dip coating. In general, a spin coating method is used. Hereinafter, a spin coating device used in the spin coating method and a coating method thereof will be described.
[0003]
FIG. 6 is a conceptual diagram of an example of a conventional spin coating device. The spin coating device 40 includes a rotary shaft 12 that is rotated at a high speed by a motor or the like (not shown), a wafer holding table 14 attached to a tip of the rotary shaft 12 for mounting and fixing a wafer, a photoresist, A dropping nozzle 16 provided directly above the center (center of rotation) of the wafer holding table 14 for dropping a coating solution such as SOG, and a catching solution or solvent scattered from the surface of the wafer 22 by high-speed rotation And a coating liquid receiving cup 20 disposed so as to cover the side part and the lower part of the wafer holding table 14 through the rotating shaft 12. In the figure, a wafer 22 is displayed on the wafer holder 14 for explanation.
[0004]
Using the spin coating apparatus 40, the wafer 22 is placed and fixed on the wafer holding table 14 by, for example, vacuum suction, and the wafer holding table 14 is rotated at a predetermined speed via the rotating shaft 12 by a motor (not shown) or the like. The coating liquid is dropped from the dropping nozzle 16 to the center of the surface of the wafer 22 while being rotated at a high speed, and the coating liquid dropped on the surface of the wafer 22 is uniformly spread by centrifugal force to form a thin film. By applying a heat treatment at the preceding and following temperatures to cure, a coating film can be formed on the surface of the wafer 22. Note that this coating step may be repeated several times in order to form a coating film having a predetermined thickness, particularly when the coating film is thick.
[0005]
However, in the above-described method for forming a coating film, when the coating liquid is uniformly thinned on the surface of the wafer 22, excess coating liquid scatters on the wall surface of the coating liquid receiving cup 20, and It adheres to the back and side walls. This is a problem in that, for example, by performing a heat treatment in a post-process of semiconductor manufacturing, the coating liquid adhered to the back surface and the side wall of the wafer 22 is hardened, and then is broken or peeled off, thereby causing particles to be generated. there were. For this reason, as shown in FIG. 7, after the coating liquid is thinned on the surface of the wafer 22, an organic solvent is sprayed on the coating liquid adhering to the outer peripheral portion of the wafer 22 to wash and remove it.
[0006]
However, when an organic solvent is sprayed on the outer peripheral portion of the wafer 22 in order to wash and remove the coating liquid attached to the outer peripheral portion of the wafer 22, as shown in FIG. 8, due to the difference in solubility between the coating liquid and the organic solvent, At the interface between the organic solvent and the coating solution on the outer periphery of the wafer 22 to which the organic solvent is sprayed, a raised portion 42 of the coating solution exceeding the crack generation limit of the cured coating film after the heat treatment is formed. The raised portion 42 of the coating liquid, like the coating liquid adhering to the back surface and the side wall of the wafer 22 described above, causes particles to be generated in a later step of semiconductor manufacturing, and has a problem of lowering the product yield. . Further, there is also a problem that the volatility of the organic solvent is affected by the degree of the holding heat of the wafer 22 and the cleaning effect is also varied.
[0007]
[Problems to be solved by the invention]
An object of the present invention is to examine various problems based on the conventional technique, and to wash an outer peripheral portion of a wafer in which a coating liquid is thinned by a spin coating method with an organic solvent when cleaning the outer peripheral portion with an organic solvent. By spraying a liquid cooling solvent on the interface with the solvent, the thickness of the raised portion of the coating liquid formed on the outer peripheral portion of the wafer is set to 0.5 μm or less, thereby preventing the generation of particles in the subsequent process. It is an object of the present invention to provide a method and a spin coating apparatus for forming a coating film in which the generation of particles is suppressed, which can improve the product yield and improve the cleaning efficiency at the outer peripheral portion of the wafer.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a coating liquid for forming a coating film from above on the center of the coating surface while rotating the semiconductor wafer about a central axis perpendicular to the coating surface of the semiconductor wafer as a rotation axis. And spreading the coating liquid on the surface to be coated by centrifugal force to make the film thinner, and spraying an organic solvent on the thinner coating film on the outer peripheral portion of the semiconductor wafer to clean and flatten the coating solution. In forming the applied coating film,
Applying at the time of spraying of the organic solvent, by spraying surfactant in the liquid cooling solvent and said organic solvent and said coating liquid, the height difference of the coating film surface and forming a coating film is 0.5μm or less It is intended to provide a method for forming a film .
Further, the present invention, while rotating the semiconductor wafer about a central axis perpendicular to the coating surface of the semiconductor wafer as a rotation axis, while dropping a coating liquid for coating film formation from above to the center of the coating surface, A coating liquid is spread on the surface to be coated by centrifugal force to be thinned, and an organic solvent is sprayed on the thinned coating film on the outer peripheral portion of the semiconductor wafer to be washed to form a flattened coating film. In doing so,
A method for forming a coating film, wherein a liquid cooling solvent is sprayed on an interface between the coating liquid and the organic solvent when the organic solvent is sprayed .
[0009]
Here, the spraying of the liquid cooling solvent is preferably performed near the tip of a nozzle for spraying the organic solvent, and at an interface between the coating solution and the organic solvent from an inlet provided on the semiconductor wafer side. .
[0010]
Further, it is preferable that the spraying of the liquid cooling solvent is performed by attaching a scattering prevention plate for preventing scattering of at least the organic solvent and the coating liquid sprayed to the spray nozzle of the organic solvent.
Further, the present invention provides a wafer holding table for mounting and fixing a wafer, rotating around a rotation axis, a drip nozzle for dropping a coating liquid on an application surface of the fixed wafer, and the fixed wafer. A spin coating device having a dedicated nozzle for spraying an organic solvent on the outer periphery of the spin coating device,
The dedicated nozzle is provided at a tip portion of the dedicated nozzle, an organic solvent discharge port for discharging the organic solvent, and a side wall near the tip portion, which is opened to the fixed wafer side, and the coating liquid and And a cooling solvent discharge port for discharging a liquid cooling solvent sprayed to an interface with an organic solvent .
[0011]
Effect of the Invention
The method and the spin coating apparatus for forming a coating film in which generation of particles is suppressed according to the present invention, use a spin coating method to thin the coating liquid on the surface of the wafer, and then apply the organic liquid to the coating liquid attached to the outer peripheral portion of the wafer. When the solvent is sprayed and washed, the difference between the solubility of the coating solution and the organic solvent prevents the formation of a raised portion of the coating solution at the interface between the coating solution and the organic solvent. An organic solvent is sprayed on the outer periphery, and a liquid cooling solvent is sprayed on the interface between the coating solution and the organic solvent to cool them.
Therefore, according to the method for forming a coating film in which generation of particles is suppressed and the spin coating device of the present invention, the viscosity of the cooled coating solution (the volatilization rate of the organic solvent contained in the coating solution) is reduced, and Further, since the volatilization rate of the sprayed organic solvent is also reduced, the difference in solubility between the coating solution and the organic solvent can be eliminated. For this reason, it is possible to prevent the formation of a rising portion of the coating liquid at the interface between the coating liquid and the organic solvent at the outer peripheral portion of the wafer, and it is also possible to improve the cleaning efficiency at the outer peripheral portion of the wafer. Further, since the liquid cooling solvent is directly sprayed, the raised portion of the outer peripheral portion of the wafer can be suppressed even by the flow pressure of the liquid cooling solvent. That is, since no raised portion is formed on the outer peripheral portion of the wafer, it is possible to prevent the generation of particles in a subsequent process, and it is also possible to improve the cleaning efficiency of the outer peripheral portion of the wafer, thereby improving the product yield. .
[0012]
【Example】
Hereinafter, a method for forming a coating film in which generation of particles is suppressed and a spin coating device according to the present invention will be described in detail based on preferred embodiments shown in the accompanying drawings.
[0013]
FIG. 1 is a conceptual diagram of an embodiment of a spin coating apparatus according to the present invention to which the method for forming a coating film in which generation of particles is suppressed according to the present invention is applied. The spin coating apparatus 10 includes a rotary shaft 12 that is rotated at a high speed by a motor or the like (not shown), a wafer holding table 14 attached to a tip of the rotary shaft for mounting and fixing a wafer, In order to spray an organic solvent and a liquid cooling solvent onto the outer peripheral portion of the wafer, a dedicated nozzle 18 provided directly above the outer peripheral portion of the wafer is provided. And a coating liquid receiving cup 20 disposed so as to cover the side and lower part of the wafer holding base 14 through the rotating shaft 12 in order to receive the coating liquid or the solvent scattered from the wafer surface by the high-speed rotation. ing. In the figure, a wafer 22 is displayed on the wafer holder 14 for explanation.
[0014]
FIG. 2 is a perspective view of an embodiment of the above-described dedicated nozzle. The dedicated nozzle 18 has a nozzle 28 having a discharge port 24 for the organic solvent at the tip and a lower portion of the side wall near the tip, that is, a nozzle 28 having a discharge port 26 for the liquid cooling solvent at the wafer 22 side. And a scattering prevention plate 30 provided in the vicinity. The dedicated nozzle 18 is provided with a liquid cooling solvent supply pipe (not shown) in a pipe of a solvent supply nozzle 28 connected to an organic solvent source (not shown). It is an integrated nozzle with a structure facing it. In this integrated type nozzle, since there is a temperature difference between the organic solvent and the liquid cooling solvent, the outside of the liquid cooling solvent supply pipe in the nozzle is covered with a heat insulating material or the like, so that the organic solvent and the liquid cooling solvent are removed. It is desirable to separate them from each other in terms of temperature.
[0015]
Here, the nozzle 28 is arranged so that the flow path of the organic solvent and the liquid cooling solvent is directed outward and downward at the outer peripheral portion of the wafer 22. However, the flow path is determined by curving the nozzle 28 as illustrated. preferable. Although an integrated nozzle may be used as in the illustrated example, if the liquid cooling solvent can be supplied to the interface between the organic solvent and the coating liquid on the wafer 22, the organic solvent and the liquid cooling solvent are discharged using separate nozzles. You may do it.
[0016]
When the organic solvent or the liquid cooling solvent is sprayed on the wafer 22 rotating at a high speed, the scattering prevention plate 30 applies the coating liquid thinned on the surface of the wafer 22 or the organic solvent or the liquid cooling solvent to the wafer 22. It is preferably provided to prevent scattering at the center. In the case where the integrated nozzle 28 is used as in the illustrated example, in order to direct the flow path of the liquid cooling solvent discharged from the discharge port opened at the lower part of the side wall of the nozzle 28 to the outside and below the outer periphery of the wafer 22, The anti-scattering plate 30 is preferably curved toward the base end of the nozzle 28, and its lower portion is preferably flat so that the distance from the wafer 22 is substantially constant. Is not particularly limited.
[0017]
Using this spin coating apparatus 10, a wafer 22 is placed and fixed on the wafer holding table 14 by, for example, vacuum suction, and the wafer holding table 14 is rotated at a predetermined speed via a rotating shaft 12 by a motor (not shown) or the like. For example, the wafer is rotated at a high speed of 2000 rpm or more, and a dropping nozzle 16 is applied to the center of the surface of the wafer 22 from an organic SOG solution containing a silicon compound as a main component, an inorganic SOG solution, a resist solution, and a polyimide resin solution (PIQ solution ), And the coating liquid dropped on the surface of the wafer 22 is uniformly stretched by centrifugal force to form a thin film.
[0018]
Here, while the wafer 22 is being rotated at a high speed, the above-described dedicated nozzle 18 is used to form an outer peripheral portion including the back surface and the side wall of the wafer 22, for example, a region extending from the outer peripheral edge of the wafer 22 to about 7 mm in the center direction. Is sprayed with an organic solvent such as IPA (isopropyl alcohol), ethanol, methanol, cyclohexanone, lactic acid (EL: ethyl lactate), and γ-butyrolactone to wash the outer periphery of the wafer 22. At the same time, a liquid cooling solvent such as liquid nitrogen (N ₂ ) or liquid helium (He) is sprayed onto the interface between the coating liquid and the organic solvent to directly locally cool the outer peripheral portion of the wafer 22.
[0019]
By performing the local cooling, the viscosity of the coating liquid on the outer peripheral portion of the wafer 22 is reduced, and the volatilization rate of the organic solvent sprayed on the outer peripheral portion of the wafer 22 is also suppressed. By eliminating the difference in solubility at the interface with the organic solvent, it is possible to prevent a raised portion from being formed on the outer peripheral portion of the wafer 22 and to improve the cleaning ability of the outer peripheral portion of the wafer 22. At the same time, by spraying the liquid cooling solvent directly on the outer peripheral portion of the wafer 22, the interface between the coating solution and the organic solvent whose solubility is no longer different due to the fluid pressure can be suppressed, and the coating liquid on the outer peripheral portion of the wafer 22 can be prevented. It is possible to prevent a raised portion from being formed at the interface with the organic solvent. Here, the thickness of the raised portion is preferably, for example, 0.5 μm or less so as not to cause generation of particles in the subsequent manufacturing steps.
[0020]
If the difference in solubility at the interface between the coating solution and the organic solvent at the outer periphery of the wafer 22 can be eliminated and the raised portion at the outer periphery of the wafer 22 can be reduced to 0.5 μm or less, the type of the liquid cooling solvent used and the direct local The time for cooling, the cooling temperature, the flow pressure, etc. are not particularly limited, but as the liquid cooling solvent, for example, liquid nitrogen or liquid helium can be used, and the time for directly performing local cooling is the time for the liquid cooling solvent to be used. Although it differs depending on the type, it is usually 3 seconds or less, preferably 2 to 3 seconds. If the difference in solubility between the coating solution and the organic solvent can be eliminated by cooling to about 20 ° C., the overall temperature distribution of the wafer 22 will be affected and the in-plane of the coating film will be affected. It preferred since there is no damaging one property. Further, the flow pressure of the liquid cooling solvent is such that, when the difference in solubility between the coating liquid and the organic solvent is eliminated, the raised portion at the outer peripheral portion of the wafer 22 can be reduced to 0.5 μm or less according to the viscosity thereof. It is preferable to select an appropriate one.
[0021]
Finally, a heat treatment is performed at a temperature of about 400 ° C., so that a coating film can be formed on the surface of the wafer 22. In the case where this coating step is repeated several times to form a coating film having a predetermined thickness, the outer peripheral portion of the wafer 22 is washed and the local cooling is performed each time before the heat treatment is performed. Is preferred.
[0022]
Next, taking a case where a wiring interlayer film (interlayer insulating film) is planarized as an example, the method of forming a coating film and the spin coating device of the present invention, in which generation of particles is suppressed, will be described in more detail based on embodiments. Will be described.
[0023]
(Example 1)
First, as shown in FIG. 3A, a silicon oxide film 32 is formed on the surface of the wafer 22, and an aluminum (Al) -based alloy layer for forming a lower wiring is formed on the silicon oxide film 32 by 1.0 μm. After this, the aluminum oxide wiring was formed by selective etching to form an aluminum wiring, and a plasma oxide film was formed on the surface of the aluminum wiring to a thickness of 0.8 μm.
Subsequently, as shown in FIG. 3B, a coating liquid containing a silicon compound as a main component (OCD-Type-7, 12000-T, manufactured by Tokyo Ohka Kogyo Co., Ltd.) is spin-coated on the plasma oxide film 36. The coating method, that is, high-speed rotation at 2000 rpm using the spin coating apparatus 10 shown in FIG. 1, the coating liquid is dropped from the dropping nozzle 16, and the wafer 22 is formed into a coating film 38 having a thickness of 1.2 μm. Was thinned over the entire surface.
[0024]
Almost at the same time, as shown in FIG. 4, using the dedicated nozzle 18 shown in FIG. 2, the outer peripheral portion including the back surface and the side wall of the wafer 22, specifically, from the outer peripheral edge of the wafer 22 to 7 mm in the center direction. The area is cleaned by spraying an organic solvent (IPA), and a liquid cooling solvent (liquid nitrogen) is sprayed onto the interface between the coating liquid and the organic solvent to directly locally cool the outer peripheral portion of the wafer 22 and then to apply a nitrogen atmosphere. The coating film was completed by heating at 425 ° C. in an annealing furnace. The flow time of the liquid cooling solvent (liquid nitrogen) was changed by setting the spraying time of the organic solvent and the liquid cooling solvent to 3 seconds, setting the temperature of the outer peripheral portion of the cooled wafer 22 to 5 to 23 ° C. (atmospheric temperature 25 ° C.). By doing so, the relationship between the liquid cooling solvent and the thickness of the raised portion of the outer peripheral portion of the wafer 22 was examined.
[0025]
Here, FIG. 5 shows the relationship between the flow rate of the liquid cooling solvent and the thickness of the raised portion of the outer peripheral portion of the wafer when a coating film is formed by applying the method for forming a coating film in which generation of particles is suppressed according to the present invention. FIG. This graph shows the result of measuring the thickness of the raised portion of the coating film formed in the above-described embodiment at the outer peripheral portion of the wafer 22 using a contact-type step measuring device. As shown in this graph, the thickness of the raised portion of the outer peripheral portion of the wafer 22 decreases according to the flow rate of liquid nitrogen, and when the flow rate of liquid nitrogen is set to 0.8 kgf / cm ² or more, 0.5 μm It turned out that the following.
[0026]
In the above-described embodiment, the semiconductor integrated circuit having the two-layer wiring structure is described. However, the method of forming a coating film in which generation of particles is suppressed and the spin coating apparatus according to the present invention are applied to a multi-layer wiring of three or more layers. The present invention is also applicable to a semiconductor integrated circuit having a structure. Further, as the liquid cooling solvent, liquid nitrogen, liquid helium, or the like can be used, or these may be used in combination. Further, the embodiment using the annealing furnace as the heat treatment has been described, but other than this, for example, lamp heating, heater heating, microwave induction heating, and a combination thereof may be used as the heating means. .
[0027]
【The invention's effect】
As described in detail above, the method for forming a coating film in which generation of particles is suppressed and the spin coating device according to the present invention use the spin coating method to thin the coating liquid on the wafer surface, When spraying an organic solvent onto the applied coating liquid and washing it, a liquid cooling solvent is directly sprayed on the interface between the coating liquid and the organic solvent to cool these coating liquids and the organic solvent and eliminate the difference in solubility. In addition, by suppressing the raised portion formed on the outer peripheral portion of the wafer due to the fluid pressure, the raised portion is prevented from being formed on the outer peripheral portion of the wafer, and the cleaning efficiency of the outer peripheral portion of the wafer is improved. Therefore, according to the method and the spin coating apparatus for forming a coating film in which generation of particles is suppressed according to the present invention, a raised portion is not formed on the outer peripheral portion of the wafer, so that a coating film with high in-plane uniformity can be formed. As a result, particles are not generated in the subsequent process, and the cleaning efficiency at the outer peripheral portion of the wafer is improved, so that the product yield can be improved.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of one embodiment of a spin coating apparatus of the present invention to which a method of forming a coating film in which generation of particles is suppressed according to the present invention is applied.
FIG. 2 is a perspective view of one embodiment of a dedicated nozzle used in the method of forming a coating film in which generation of particles is suppressed according to the present invention.
FIGS. 3A and 3B are cross-sectional process diagrams of one embodiment illustrating a method of manufacturing a semiconductor device using a coating film.
FIG. 4 is a schematic cross-sectional view of one embodiment illustrating a method for forming a coating film in which generation of particles is suppressed according to the present invention.
FIG. 5 is a view showing a relationship between a flow rate of liquid nitrogen and a thickness of a raised portion on a peripheral portion of a wafer when a coating film is formed by applying the method for forming a coating film in which generation of particles is suppressed according to the present invention. It is a graph of an example.
FIG. 6 is a conceptual diagram of an example of a conventional spin coating device.
FIG. 7 is a perspective view of one embodiment of a spin coating apparatus to which a conventional method for cleaning a coating liquid adhering to an outer peripheral portion of a wafer is applied.
FIG. 8 is a cross-sectional view of an example showing a raised portion of the outer peripheral portion of a wafer formed when a conventional method for cleaning a coating liquid adhering to the outer peripheral portion of a wafer is applied.
[Explanation of symbols]
10, 40 Rotary coating device 12 Rotary shaft 14 Wafer holder 16 Dropping nozzle 18 Dedicated nozzle 20 Coating liquid receiving cup 22 Wafer 24, 26 Discharge port 28 Nozzle 30 Scatter prevention plate 32 Silicon oxide film 34 Aluminum-based wiring 36 Plasma oxide film 38 coating film 42 swelling part

Claims (5)

While rotating the semiconductor wafer around a central axis perpendicular to the coating surface of the semiconductor wafer as a rotation axis, a coating solution for forming a coating film is dropped from above onto the center of the coating surface, and the coating solution is coated with the coating solution. While spreading the surface by centrifugal force to make it thinner, in forming a flattened coating film by cleaning by spraying an organic solvent on the thinned coating film on the outer peripheral portion of the semiconductor wafer,
During the spraying of the organic solvent, a liquid cooling solvent is sprayed on an interface between the coating solution and the organic solvent to form a coating film having a height difference of 0.5 μm or less on the surface of the coating film. Method of forming a film. While rotating the semiconductor wafer around a central axis perpendicular to the coating surface of the semiconductor wafer as a rotation axis, a coating solution for forming a coating film is dropped from above onto the center of the coating surface, and the coating solution is coated with the coating solution. While spreading the surface by centrifugal force to make it thinner, in forming a flattened coating film by cleaning by spraying an organic solvent on the thinned coating film on the outer peripheral portion of the semiconductor wafer,
A method for forming a coating film, wherein a liquid cooling solvent is sprayed on an interface between the coating solution and the organic solvent when the organic solvent is sprayed. 3. The method according to claim 1, wherein the spraying of the liquid cooling solvent is performed near an end of a nozzle for spraying the organic solvent, and at an interface between the coating solution and the organic solvent from an inlet provided on the semiconductor wafer side. The method for forming a coating film according to the above. The method for forming a coating film according to claim 3, wherein the spraying of the liquid cooling solvent is performed by attaching a scattering prevention plate for preventing scattering of at least the organic solvent and the coating liquid sprayed to the spray nozzle of the organic solvent. A wafer holding table for mounting and fixing a wafer and rotating about a rotation axis, a drip nozzle for dropping a coating liquid on a coating surface of the fixed wafer, and an organic solvent on an outer peripheral portion of the fixed wafer. Spin coating device having a dedicated nozzle for spraying
The dedicated nozzle is provided at a tip portion of the dedicated nozzle, an organic solvent discharge port for discharging the organic solvent, and a side wall near the tip portion, which is opened to the fixed wafer side, and the coating liquid and And a cooling solvent discharge port for discharging a liquid cooling solvent sprayed to an interface with an organic solvent .

Images