JP3988452B2 - Method for forming a thin film on a substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for forming a thin film to a substrate which can spread efficiently and simply viscous fluid in an arbitrary form. <P>SOLUTION: The substrate mounted on a table and a nozzle are relatively moved in a direction parallel with a main surface of the substrate, and the viscous fluid is discharged from the nozzle, thereby spreading a thin film on a main surface of the substrate. Between the substrate and the nozzle, a mask having an aperture of a pattern form which is to be spread on the main surface of the substrate is arranged fixedly to the substrate. The main surface of the mask and a discharge port of the nozzle are relatively moved in a state of noncontact. From the nozzle, the viscous fluid is discharged on the main surface of the substrate through the aperture of the mask, thereby forming the thin film of a pattern form to be spread. <P>COPYRIGHT: (C)2003,JPO

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for forming a thin film on a substrate, and more particularly to a method for forming a thin film by applying a viscous fluid such as a resist on a substrate such as a circular semiconductor wafer.
[0002]
[Prior art]
As a method for forming a resist on the surface of a semiconductor wafer, for example, as disclosed in Japanese Patent Laid-Open No. 4-96228, a liquid resist is dropped from a nozzle at the center of the surface of a semiconductor wafer while rotating the semiconductor wafer at about 4000 rpm using a spin coater. Liquid resist is spread and applied over the entire surface of the semiconductor wafer by centrifugal force, and after a short period of time, the solvent is evaporated from the applied resist film to reduce fluidity, and then the rotational speed is reduced to about 2000 rpm to reduce the flow rate from the nozzle. There is one in which a solvent is dropped to dissolve and remove the liquid resist that has risen around the wafer edge due to an edge effect such as surface tension.
[0003]
The liquid resist that swells around the wafer edge due to the edge effect generates a large amount of gas from the coating film due to the heat treatment in the next process, which causes problems in circuit formation.
[0004]
Therefore, the film thickness that has risen around the periphery by the solvent is dissolved and removed.
[0005]
[Problems to be solved by the invention]
In the spin coater, in order to obtain a uniform coating film, it is necessary to drop several times to several tens of times the required amount of liquid resist, which is wasteful.
[0006]
Further, in dissolving and removing the peripheral portion, it is difficult to reliably remove only the film thickness portion of the peripheral portion due to the mismatch between the applied resist film and the solvent components. This is due to the type and flow characteristics of the liquid resist and the type and flow characteristics of the solvent. The liquid resist and the solvent are mixed at the interface, and a chemical reaction is caused depending on the combination. For this reason, a circuit pattern located slightly closer to the center from the peripheral edge of the wafer becomes unusable as a coating film defect, leading to a decrease in productivity.
[0007]
As a method for obtaining a uniform coating film without waste, there is one in which a substrate and a nozzle are relatively moved in a direction parallel to the main surface of the substrate to discharge a viscous fluid from the nozzle.
[0008]
In this technique, an oblong shape or a single-character porous nozzle in which a large number of discharge ports are arranged in a row can be applied to a rectangular, parallelogram or rhombus pattern.
[0009]
However, since discharge occurs simultaneously from a large number of discharge ports, in order to apply to a pattern other than a rectangle, parallelogram, or rhombus, a valve is provided corresponding to the large number of discharge ports, and the valve is opened and closed according to the pattern. This complicates apparatus and control.
[0010]
It is possible to prepare a nozzle with a fine discharge port for the width of the pattern and apply it with a single stroke, but in a so-called relative movement path that makes a U-turn, the relative movement stops at the U-turn location. As a result, excessive discharge occurs. Therefore, it is necessary to stop the discharge at the U-turn portion or to remove the excess like a spin coater.
[0011]
SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a method for forming a thin film on a substrate, which can easily apply a viscous fluid to an arbitrary shape without waste.
[0012]
[Means for Solving the Problems]
The method of the present invention that achieves the above object is characterized in that a substrate and a nozzle placed on a table are relatively moved in a direction parallel to the main surface of the substrate, and a viscous fluid is discharged from the nozzle to discharge the main substrate. In the case of applying a thin film on the surface, a mask having a pattern-shaped aperture to be applied on the main surface of the substrate between the substrate and the nozzle is fixedly arranged on the substrate, and the main surface of the mask and the nozzle outlet In a non-contact state, and a viscous fluid is discharged from the nozzle through the mask opening onto the main surface of the substrate to form a thin film having a pattern shape to be applied. In the relative movement, a parallel movement is performed so as to maintain the distance between the position of the mask main surface and the nozzle outlet.
[0013]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to FIGS.
[0014]
FIG. 1 is a schematic perspective view showing a resist film forming apparatus 100 according to this embodiment.
[0015]
In the figure, 1 is a stand, 2 is a suction table lifting motor, 3 is a power transmission shaft, 4 is a suction table, 5 is a mask having an opening 5a, 6 is a resist (viscous fluid) storage cylinder (container), 7 Is a nozzle communicating with the storage cylinder 6, 8 is a resist filled in the storage cylinder 6, and 10 is a semiconductor wafer on which a resist film is to be formed. The discharge port of the nozzle 7 is circular and is sufficiently smaller than the diameter of the semiconductor wafer 10.
[0016]
The suction table 4 is provided on the gantry 1 of the coating device 100, and the power generated by the lifting motor (M) 2 is converted into a force that moves in the vertical direction via the power transmission shaft 3, and along a guide (not shown). The suction table 4 moves in the vertical direction. Note that the same operation is possible even if an air cylinder or the like is used as the power source instead of the lifting motor 2.
[0017]
The semiconductor wafer 10 is placed on the suction table 4 having a number of suction holes (not shown), and then the back surface can be sucked and fixed by the vacuum source V. The mask 5 is fixed to the gantry 1 via a support frame (not shown). After the semiconductor wafer 10 is fixed to the suction table 4 by suction, the suction table 4 is moved upward by the lifting motor 2 and fixed on the back surface of the mask 5. It has a configuration.
[0018]
A storage cylinder 6 is held above the semiconductor wafer 10 and the mask 5 by a holding arm (not shown) fixed to the gantry 1. The storage cylinder 6 is moved in the X-axis direction and Y-axis by a linear motion element or servomotor (not shown). Driven in the direction and Z-axis direction. The inside of the storage cylinder 6 is filled with a resist 8 discharged from a nozzle 7 on a semiconductor wafer 10. The resist 8 is discharged from a nozzle 7 provided at the lower end by injecting compressed air through an air pipe connected to the upper end of the storage cylinder 6 and pressurizing the resist 8.
[0019]
The pressure of the compressed air is the film thickness to be applied onto the semiconductor wafer 10 when the lower end discharge port of the nozzle 7 is set relative to the surface of the semiconductor wafer 10 and moved relative to the film thickness to be applied onto the semiconductor wafer 10. Is assumed to be obtained.
[0020]
Next, resist film formation on the semiconductor wafer 10 will be described with reference to FIGS.
[0021]
As shown in FIG. 2A, first, the semiconductor wafer 10 is placed at a desired position on the suction table 4 by a transfer robot or the like. At this time, the suction table 4 is separated from the mask 5, and the distance may be such that it does not interfere when the semiconductor wafer 10 is placed. Further, when the semiconductor wafer 10 is placed, positioning by image recognition or the like may be performed.
[0022]
On the back surface of the mask 5, a counterbore hole 5h having a size slightly larger than the outer shape of the semiconductor wafer and the same as or slightly smaller than the thickness of the semiconductor wafer is provided so that the semiconductor wafer 10 and the mask 5 are in contact with each other. . This is to ensure that the semiconductor wafer 10 and the mask 5 can contact each other. An opening 5a having a size smaller than the outer shape of the semiconductor wafer 10 and having a thickness that matches the desired coating thickness is provided. Here, the hole size is determined by the circuit size and arrangement of the semiconductor wafer 10. Even when the semiconductor wafer 10 has an orientation flat, the opening size may be slightly smaller along the orientation flat. The opening 5a is aligned with a pattern for forming a resist film on the semiconductor wafer 10. Therefore, the semiconductor wafer 10 has a shape in which the peripheral edge is trimmed by the opening peripheral edge portion 5 p of the mask 5.
[0023]
Next, as shown in FIG. 2B, the suction table 4 is moved upward to a position where the back surface of the mask 5 is in contact with the semiconductor wafer 10 and the suction table 4.
[0024]
The mask 5 and the semiconductor wafer 10 maintain a fixed relationship so that they do not move relative to each other in the X and Y axial directions.
[0025]
Next, the nozzle 7 is moved in the X-axis and Y-axis directions so as to move onto the mask 5 slightly away from the end of the semiconductor wafer 10, and the lower end of the nozzle 7 is brought close to the surface of the mask 5. The storage cylinder 6 is moved downward in the Z-axis direction, and the nozzle 7 is moved to the application start point. The discharge port of the nozzle 7 is not in contact with the surface of the mask 5, but the distance from the lower end discharge port of the nozzle 7 to the surface of the mask 5 is very close.
[0026]
Furthermore, the compressed air P adjusted to the above-mentioned desired pressure is applied to the storage cylinder 6 at the application start point.
[0027]
Subsequently, as shown in FIG. 2C, the nozzle 7 is moved relative to the semiconductor wafer 10 in parallel with the storage cylinder 6 so as to maintain a distance from the position of the main surface of the mask 7 of the nozzle 7. In this state, the semiconductor wafer 10 is moved in a straight line so as to cross or traverse.
[0028]
The resist 8 is not discharged where the discharge port of the nozzle 7 and the surface of the mask 5 are close to each other. This is because even if the resist 8 is about to be discharged from the nozzle 7, the discharge is prevented by receiving a reaction force from the surface of the mask 5. Moreover, even if there is ejection, the reaction force is acting so little that the surface of the mask 5 is thinly applied.
[0029]
At the opening 5a, there is a distance between the discharge port of the nozzle 7 and the surface of the semiconductor wafer 10 (the distance between the discharge port of the nozzle 7 and the surface of the semiconductor wafer 10 is a distance about the desired film thickness). The reaction force is not transmitted to the resist 8 in the storage cylinder 6, and the resist 8 is discharged onto the semiconductor wafer 10.
[0030]
When the nozzle 7 reaches the mask 5 again and the nozzle 7 and the surface of the mask 5 come close to each other, the reaction force is transmitted and the ejection is automatically stopped. Therefore, as shown in FIG. 2C, the applied resist 11 is on the surface of the semiconductor wafer 10, and there is no resist on the surface of the mask 5.
[0031]
FIG. 3 shows a situation in which the resist is automatically discharged and applied in accordance with the shape of the opening 5a.
[0032]
The discharge start end S and end E of the resist are automatically determined by the opening 5a.
[0033]
When the nozzle 7 is shifted at a pitch L in accordance with the diameter of the nozzle 7 and reciprocated linearly moved, a resist film can be formed in the shape of the opening 5a. If the pitch L is too small, the interface will protrude in a convex shape. If the pitch L is too large, the interface will be dented or the surface of the semiconductor wafer 10 will be exposed. Therefore, the optimum coating pitch for the resist fluidity, in other words, the pitch at which the interface between the straight lines has the same film thickness as other parts even if adjacent straight lines are drawn, is determined at this optimal pitch. It is good to reciprocate.
[0034]
After the end of the discharge, as shown in FIG. 2D, the application of the compressed air P to the storage cylinder 6 is stopped, the Z axis is driven, and the nozzle 7 and the storage cylinder 6 are attached to the mask 5 or the arm of the transfer robot. After moving upward and retracting to a position where there is no interference, the suction table 4 is moved downward, and the mask 5 and the semiconductor wafer 10 are pulled apart. The separation speed at this time, that is, the downward movement speed of the adsorption table 4 is determined by the fluidity (viscosity, sagging property) of the resist 8. For example, a material having a relatively high viscosity has a high speed, In the case of a material having a low viscosity, the film thickness at the peripheral edge of the semiconductor wafer 10 can be kept uniform as in other parts by moving at a low speed.
[0035]
Next, another embodiment shown in FIG. 4 will be described.
[0036]
In FIG. 4, the mask 5 has an annular groove 5b having a depth D3 around the opening 5a. The discharge port of the nozzle 7 is not in contact with the surface of the mask 5, but the distance D <b> 1 from the lower end discharge port of the nozzle 7 to the surface of the mask 5 is very close. The distance D <b> 2 from the lower end discharge port of the nozzle 7 to the surface of the semiconductor wafer 10 is the film thickness of the resist 8 desired to be formed on the semiconductor wafer 10.
As indicated by the arrows, the storage cylinder 6 and the nozzle 7 are moved relative to the mask 5 and the semiconductor wafer 10 while pressurizing the resist in the storage cylinder 6 with compressed air. In this embodiment, the nozzle 7 passes through the groove and then reaches the opening 5a.
[0037]
When the nozzle 7 is positioned on the mask 5, no resist is discharged. Although discharge occurs at the annular groove 5b, the discharge of the resist stops because it is on the mask 5 again.
At this time, the resist not only receives a reaction force, but also rubs off the resist hanging from the discharge port with the corners of the groove 5b and the upper surface serving as edges. Then, it reaches the opening 5a and starts discharging. At this point, since the resist at the lower end of the nozzle 7 is scraped off and is in a clean state, the discharge shape onto the semiconductor wafer 10 does not rise at the starting end. At the peripheral edge of the opening in the moving direction, the distance from the surface of the mask 5 is abruptly narrowed. The further annular groove tb functions as a groove at the preceding position when the nozzle 7 reciprocates.
[0038]
The present invention is not limited to the above embodiment, and may be implemented in the following form.
[0039]
That is, if an inclined surface facing the semiconductor wafer 10 side is provided on the peripheral edge of the opening of the mask 5 and is overhanged when viewed from the semiconductor wafer 10 side, the resist coming out of the nozzle 7 is exposed from the upper surface of the mask 5. The resist can be discharged in a form in which the resist is cut between the semiconductor wafer 10 and the upper surface of the mask 5 without flowing on the inclined side surface of the peripheral edge of the hole.
[0040]
Further, the nozzles may be arranged side by side as shown in FIGS. In these cases, the resist can be discharged with a small number of relative movements.
[0041]
In the nozzle 71 of FIG. 5, the discharge hole 71a has a long and narrow slit shape. It is a rectangle or an ellipse. An ellipse may be used. The nozzle 72 of FIG. 6 has a shape in which a plurality of minute ejection holes 72a having a circular shape, an elliptical shape, or the like are arranged in a horizontal row at regular intervals.
[0042]
In the discharge holes 71a and 72a, the nozzles 71 and 72 move relative to the semiconductor wafer 10 as shown in FIG. Discharge does not occur in response to a reaction force at a location close to the upper surface. Therefore, although the valve is not operated, the selective discharge is automatically performed by the opening 5a, and the resist can be discharged and applied in the shape of the opening.
[0043]
The viscous fluid discharged from the nozzle is not limited to a resist, and the substrate to be applied is not limited to a semiconductor wafer. Moreover, the pattern to be discharged is also arbitrary, and may be used for applying a rectangular, parallelogram, or rhombus pattern.
[0044]
【The invention's effect】
As described above, according to the present invention, a viscous fluid can be applied to an arbitrary shape without waste.
[Brief description of the drawings]
FIG. 1 is a perspective view showing a resist film forming apparatus according to an embodiment of the present invention.
FIG. 2 is a schematic view of an operation when a resist is applied to a semiconductor wafer by the resist film forming apparatus shown in FIG.
3 is a perspective view for explaining a situation when a resist is discharged and applied to a semiconductor wafer by the resist film forming apparatus shown in FIG. 1. FIG.
FIG. 4 is a diagram for explaining a situation in which a resist is discharged using a mask according to another embodiment of the present invention.
FIG. 5 is a diagram showing a nozzle shape according to another embodiment of the present invention.
FIG. 6 is a diagram showing a nozzle shape according to another embodiment of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Stand 2 Suction table raising / lowering motor 3 Power transmission source 4 Suction table 5 Mask 6 Storage cylinder 7 Nozzle 8 Resist 10 Semiconductor wafer 11 Discharge applied resist 100 Resist film forming apparatus

Claims (4)

With respect to the substrate placed on the table, the nozzle is relatively moved in a direction parallel to the main surface of the substrate, and a viscous fluid is discharged from the nozzle to form a thin film on the main surface of the substrate.
A mask having a pattern-shaped opening to be applied on the main surface of the substrate between the substrate and the nozzle is fixedly arranged with respect to the substrate, and an interval between the main surface of the mask and the discharge port of the nozzle is set. The discharge port of the nozzle is not in contact with the main surface of the mask, and the viscous fluid is held at an interval at which the viscous fluid cannot be discharged from the discharge port of the nozzle. A method of forming a thin film on a substrate, wherein the thin film has a pattern shape to be applied by discharging a viscous fluid onto the main surface of the substrate through the opening of the mask from the discharge port of the nozzle.   2. The substrate according to claim 1, wherein the distance between the main surface of the substrate and the discharge port of the nozzle is substantially equal to the thickness of the viscous fluid applied to the main surface of the substrate. Thin film forming method.   2. The method of forming a thin film on a substrate according to claim 1, wherein the nozzle is relatively moved in a direction of opening of the mask through a groove provided on a main surface of the mask.   The thing of Claim 1 WHEREIN: The space | interval of the discharge port of the said nozzle and the main surface of the said board | substrate is set so that it may become the space | interval similar to the film thickness of the said viscous fluid to apply | coat to the said board | substrate, A method for forming a thin film on a substrate, characterized in that the pressure applied to the container in which the viscous fluid is discharged is set to a pressure at which the viscous fluid can be discharged from the discharge port of the nozzle at the mask opening.

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