JPH0613302A - Resist coater and resist coating method - Google Patents

Abstract

PURPOSE:To coat a resist in uniform thickness on the upper and lower parts of stepped sections by providing a means for applying centrifugal force horizontally from the center of board surface to its periphery on the board surface and a means for applying centrifugal force vertically to the board surface and optimizing the intensity of the two centrifugal forces and its applying time. CONSTITUTION:A first rotating means 19 generates centrifugal force directing horizontally from the center to periphery on a board 10 and flows the applied resist 12 from upper side to lower side on a stepped section 21. A second rotating means 20 applied centrifugal force vertically on the board 10 and flows the resist 12 from lower side to upper side on the section 21. First, the resist 12 is dripped on the center of the board by means of a nozzle 14 and only the means 19 is driven to spread the resist 12 wholely on the board 10. Next, both the means 19 and 20 are simultaneously driven for a specified time. Thus, even if there are any stepped sections on the surface for coating resist, the resist can be applied in uniform thickness on upper and lower sides of the stepped sections.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a resist coating apparatus and a resist coating method in photolithography.

[0002]

2. Description of the Related Art Resist coating is a part of a photolithography process, and is an essential technique in a wafer manufacturing process typified by current semiconductor devices. In a typical resist coating device, the resist is dropped onto the wafer,
After that, there is a spin coater in which a wafer is rotated and the resist is uniformly applied onto a substrate by utilizing the centrifugal force.

FIG. 5 is a schematic perspective view showing a main part of a spin coater. Reference numeral 43 in the drawing denotes a rotor, and a rotary table 41 is fixed to the upper surface of the rotor 43, and a disk-shaped substrate 40 is placed at the center of the rotary table 41. Further, a nozzle 44 for dropping the resist 42 is provided above the turntable 41.

Next, a method of applying a resist using this spin coater will be described. First, the substrate 40 is placed on the turntable 41, and then the resist 4 is passed through the nozzle 44.
2 is dropped on the central portion of the substrate 40, and the turntable 41 is rotated to rotate the substrate 40. When the substrate 40 rotates, the resist 42 spreads from the central portion to the peripheral portion of the substrate 40 due to centrifugal force, and by keeping the rotation for a certain period of time, the resist 42 can be uniformly applied to the entire substrate surface.

In a wafer manufacturing process for manufacturing a semiconductor device, film formation, photolithography and etching are repeated many times, and a step is formed during the manufacturing process, and it is necessary to apply a resist to the step. Come out. FIG. 6 is a cross-sectional view showing a case where the substrate 30 having the step portion 31 is coated with a resist by applying a centrifugal force in the direction of arrow M using a spin coater. A step portion 31 and a resist layer 32b are formed on the upper surface of the substrate 30, and a resist layer 32a is further formed on the upper surface of the step portion 31.

The thickness L _a1 of the resist layer 32a formed on the upper surface of the step portion 31 and the thickness L _b1 of the resist layer 32b directly formed on the upper surface of the substrate 30 are compared to obtain L _a1 . In comparison, L _b1 is thicker.

On the other hand, FIGS. 7 (a) to 7 (c) are sectional views showing an exposure / development process which is a part of the photolithography process, and FIGS. 7 (a) to 7 (c) show different exposure conditions. Is shown. FIG. 7A shows a case where the exposure amount is optimum, FIG. 7B shows a case where the exposure amount is larger than the optimum exposure amount, and FIG. 7C shows a case where the exposure amount is smaller than the optimum exposure amount. Shown respectively. Reference numeral 30 in the drawing denotes a substrate. On the upper surface of the substrate 30, resist layers 32b and 32c (a portion including a solid line and a broken line) are formed before development, and a mask is provided above the resist layers 32b and 32c. 35 is fixed, and the pattern on the mask 35 is transferred to the resist layers 32b and 32c by exposure. After that, development is performed, and the resist layer 32b corresponding to the desired pattern is formed.
Only the solid line part is selectively left. When the exposure is performed at the optimum exposure amount, a desired pattern is formed as shown in FIG. 7A, and when the exposure amount is larger than the optimum exposure amount, the mask is formed as shown in FIG. 7B. The resist layer 32b is protected by the pattern and is exposed to light, leaving a pattern smaller than the desired pattern. When the exposure amount smaller than the optimum exposure amount is performed, the exposure is not completely performed until the substrate 30 is reached.
A pattern larger than the desired pattern is left as shown in FIG.

Therefore, when exposing a resist, it is necessary to irradiate an optimum exposure amount, and a thick resist is irradiated with a large exposure amount according to the thickness, and a thin resist is irradiated with a small exposure amount according to the thickness. Further, since the appropriate exposure amount has a certain width, an appropriate pattern can be obtained by performing the exposure within the range of this width.

At present, the exposure amount condition after coating a resist on a substrate having a step portion can be mainly classified into three types. This will be described with reference to FIGS. 8, 9 and 10. 8, 9 and 10 are sectional views showing the case where the substrate 30 in the state shown in FIG. 6 is exposed and developed, and the exposure conditions are different in FIG. 8, FIG. 9 and FIG. ing.

8 (a), 9 (a) and 10 (a) show the steps of exposing and developing the resist on the step portion 31, and FIGS. 8 (b) and 9 (b). FIG. 10B shows a process of exposing and developing the resist on the substrate 30.

A step portion 31 is formed on the upper surface of the substrate 30 in FIGS. 8A, 9A and 10A, and resist layers 32a and 32a ₁ are formed on the step portion 31.
(A portion including a solid line and a broken line) is formed, and a mask 35 is fixed above the resist layers 32a and 32a ₁ .
The pattern on the mask 35 is exposed to expose the resist layer 32.
a, 32a ₁ . After that, development is performed, and only the resist layer 32a (solid line portion) corresponding to the desired pattern is selectively left.

Resist layers 32b and 32b ₁ are formed on the upper surface of the substrate 30 shown in FIGS. 8B, 9B and 10B.
(A portion including a solid line and a broken line) is formed, and a mask 35 is fixed above the resist layers 32b and 32b ₁ .
The pattern on the mask 35 is exposed to expose the resist layer 32.
b, 32b ₁ . After that, development is performed, and only the resist layer 32b (solid line portion) corresponding to the desired pattern is selectively left.

The exposure condition in FIG. 8 is set to an optimum exposure amount for the film thickness of the resist layer 32a on the step portion 31. Therefore, the pattern of the resist layer 32a having the optimum shape can be obtained. On the other hand, as shown in FIG. 6, the thickness of the resist 32b on the substrate 30 is equal to that of the resist layer 32a on the step portion 31.
Since the resist 32b is thicker than the above, the resist 32b is underexposed and the pattern of the resist layer 32b having an optimum shape cannot be obtained.

The exposure condition in FIG. 9 is set to an optimum exposure amount for the film thickness of the resist layer 32b on the substrate 30.
Therefore, the pattern of the resist layer 32b having the optimum shape can be obtained. On the other hand, as shown in FIG. 6, since the thickness of the resist layer 32a on the step portion 31 is smaller than the thickness of the resist layer 32b on the substrate 30, the exposure amount becomes excessive and the resist 32a protected by the mask is exposed. _The wraparound exposure is performed up to _one portion, and the pattern of the resist layer 32a having an optimum shape cannot be obtained.

The exposure condition in FIG. 10 is set to an intermediate value between the optimum exposure amount for the resist layer 32a on the step portion 31 and the optimum exposure amount for the resist layer 32b on the substrate 30. In this case, the shape of the resist layer 32a on the step portion 31 and the shape of the resist layer 32b on the substrate 30 are substantially the same, and the patterns of the resist layers 32a and 32b are also substantially the same.

Therefore, conventionally, in the pattern of the resist layer 32a on the step portion 31 and the pattern of the resist layer 32b on the substrate 30, when the pattern of the resist layer 32a on the step portion 31 is more important, it is shown in FIG. The exposure and development are performed, and when the pattern of the resist layer 32b on the substrate 30 is more important, the exposure and development shown in FIG. 9 are performed, and the pattern of the resist layer 32a on the step 31 and the substrate 30 are performed. If the pattern of the resist layer 32b is as important as the above, the means shown in FIG. 10 such as exposure and development is taken.

[0017]

When resist is applied to the substrate 30 having the step portion 31 formed by using the conventional resist coating apparatus as shown in FIG. 5, the resist reduces the surface area due to surface tension and the substrate Since it flows from the center on the periphery 30 to the periphery, the thickness of the resist layer 32a applied on the step portion 31 and the thickness of the resist 32b applied on the substrate 30 below the step portion 31 are inevitably different from each other.

For this reason, the pattern of the resist layer 32a on the step portion 31 and the pattern of the resist layer 32b on the substrate 30 are not affected by exposure and development under any of the exposure conditions of FIG. 8, FIG. 9 and FIG. At the same time, there was a problem that it was not optimal.

That is, it is possible to form the resist pattern in an appropriate shape even if the resist thicknesses are slightly different, but when the resists having greatly different thicknesses are applied, the optimum exposure conditions for both are set. There was a problem that it could not be set.

This problem becomes more serious as the difference in thickness between the resist layer 32a and the resist layer 32b increases. The present invention has been made in view of the above problems, and a resist coating apparatus capable of coating a resist with an equal thickness on an upper portion of a step and a lower portion of the step, and a resist having an optimum shape in an exposure / development process. It is an object of the present invention to provide a resist coating method capable of obtaining the above pattern.

[0021]

In order to achieve the above object, a resist coating apparatus according to the present invention comprises means for fixing a substrate and centrifugal force in the horizontal direction from the center to the periphery of the substrate surface. And a second rotating means for applying a centrifugal force in a direction perpendicular to the substrate surface.

The resist coating method according to the present invention is
The method further comprises the steps of dripping the resist onto the substrate and thereafter applying a centrifugal force in the horizontal direction to the substrate surface from the center of the substrate surface to the periphery and applying a centrifugal force in the vertical direction to the substrate surface. There is.

[0023]

When the centrifugal force is applied from the center of the substrate surface to the periphery only in the horizontal direction to the substrate surface, the resist flows from the center of the substrate to the periphery and finally spreads over the entire surface of the substrate. Therefore, when the resist is applied to the substrate having the step portion by applying the centrifugal force, it is more stable to reduce the surface area of the resist due to the surface tension. Therefore, as shown in FIG. Substrate 30
It is smaller than the unevenness formed by the stepped portion 31 of the surface. The resist layers 32a and 32b spread while keeping the surface unevenness smaller than the unevenness formed by the step portion 31, the resist layer 32a on the step portion 31 becomes thin, and the resist layer 32b below the step portion 31 becomes thick.

On the other hand, FIG. 4 is a cross-sectional view showing a case where a centrifugal force is applied in the direction perpendicular to the substrate surface after resist application. A step 31 and a resist layer 32b are formed on the upper surface of the substrate 30.
And the resist layer 3 is formed on the upper surface of the step portion 31.
2a is formed.

The thickness L _a2 of the resist layer 32a formed on the upper surface of the step portion 31 and the substrate 30 below the step portion 31.
Comparing with the thickness L _b2 of the resist layer 32b formed on the upper surface of L _b2 , L _b2 is thinner than L _a2 .
This is because a centrifugal force is applied in the direction of arrow S in the figure, so that the resist layers 32a and 32b are acted on from the bottom to the top of the step portion 31. At this time, if the centrifugal force is larger than the surface tension, the thickness of the resist layer 32a on the step portion 31 becomes thicker and the thickness of the resist layer 32b on the substrate 30 becomes thinner.

As described above, the centrifugal force from the center of the substrate surface toward the periphery to the substrate surface in the horizontal direction has a function of causing the resist applied on the substrate having the step portion to flow downward from the step portion. On the other hand, the centrifugal force in the direction perpendicular to the substrate surface has the effect of flowing the resist from the bottom to the top of the step.

When these two centrifugal forces are applied to the substrate simultaneously or independently, and the magnitude of the centrifugal force or the time of applying the centrifugal force is changed, the thickness of the resist above the step and the bottom of the step are changed. The thickness of the resist on the substrate can be adjusted to be thick or thin.

Further, by optimizing the magnitudes of the two centrifugal forces and the time during which the centrifugal force is applied, it is possible to make the resist film thicknesses above and below the step portion equal.
Such control of the resist film thickness can be performed by the rotation speed and rotation time of the rotating means.

[0029]

Embodiments of a resist coating apparatus and a resist coating method according to the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic perspective view showing a resist coating apparatus according to the embodiment. Reference numeral 11 in the drawing denotes a disc-shaped turntable, and the radius of the turntable 11 is 2.5 inches. A small hole (not shown) is formed on the surface of the turntable 11 so that the substrate 10 can be vacuum-sucked. In addition, the turntable 11 includes a fixing portion 18 for mechanically fixing the substrate 10.
have. Further, a rotor 13 is arranged below the center of the turntable 11, and a cylindrical stator 15 serving as a drive source for rotating the rotor 13 is provided on the rotor 13.
, A rotor 16 is connected to the side surface of the stator 15, and a stator 17 that is a drive source for rotating the rotor 16 is connected to the other end of the rotor 16. Further, a nozzle 14 for dropping the resist 12 is arranged above the turntable 11.

The first rotating means 19 is composed of a motor composed of a rotor 13 and a stator 15, and the rotating table 11 is rotated in the direction of the arrow by this motor to move from the center of the substrate 10 to the periphery and to the substrate 10. It is designed to give centrifugal force in the horizontal direction.

The second rotating means 20 is composed of a motor composed of a rotor 16 and a stator 17, and a centrifugal force is applied to the substrate 10 in the vertical direction by the motor.

Next, a resist coating method using the resist coating apparatus will be described.

A Si wafer having a diameter of 3 inches was used as the substrate 10, and a step portion was formed on the substrate 10. The stepped portion was formed depending on the presence / absence of a resist by applying a resist on the substrate 10 to perform exposure and a phenomenon.

FIG. 2 shows the substrate 10 having the step portion 21. The step portion 21 made of resist has a side of 50 μm.
The squares of m had a thickness of 10 μm, the gap between the step portions 21 was 50 μm, and about 400,000 step portions 21 were formed so as to cover the entire surface of the substrate 10. First, the substrate 10 is vacuum-adsorbed by a small hole on the surface of the turntable 11 and the substrate 1
The end portion of 0 is mechanically fixed by the fixing portion 18 so as to be fixed on the turntable 11. Next, the resist 12 was dropped from the nozzle 14 to the center of the substrate, and then the substrate was rotated in three steps. At this time, when the conventional spin coater was used, the resist was rotated at 2000 rpm at 3 rpm.
By holding for 0 seconds, the resist thickness becomes 5.4μ.
The viscosity of m was used. As the first step, only the first rotating means 19 was driven to rotate the substrate 10 horizontally at 300 rpm for 5 seconds to spread the resist on the entire surface of the substrate 10. In the second step, for the purpose of spreading the resist further thinly, only the first rotating means 19 is driven, and 300r
It was kept for 30 seconds at a rotation speed of more than pm. As a third step, the first rotating means 19 and the second rotating means 20 were simultaneously driven for 30 seconds in order to equalize the thickness of the resist on the step portion 21 and the thickness of the resist on the substrate 10. The rotation speed of the first rotation means 19 at this time was made the same as the rotation speed of the first rotation means 19 in the second stage.

The thickness of the resist on the step portion 21 and the substrate 10
The thickness of the above resist was measured by SEM, and Table 1 below shows the number of rotations of the first rotating means 19, the number of rotation of the second rotating means 20, the thickness of the resist on the step portion 21 and the resist on the substrate 10. The thickness difference is the value obtained by subtracting the thickness of the resist on the step portion 21 from the thickness of the resist on the substrate 10, and the unit is μm.

[0036]

[Table 1]

As is apparent from Table 1, the first rotating means 1
When the number of rotations of No. 9 increases, the difference in thickness increases, whereas on the other hand, when the number of rotations of the second rotating means 20 increases, the difference in thickness decreases and tends to become negative eventually.
When the rotation speed of the first rotating means exceeded 2000 rpm, the difference in thickness did not become zero even if the rotation speed of the second rotating means was increased to 1000 rpm. However, the first rotating means 1
When the rotation speed of 9 is 1000 rpm and 1500 rpm, when the rotation speed of the second rotating means 20 is increased, the difference in thickness changes from plus to minus, and the condition that the difference in thickness becomes zero during that time is I was able to confirm that it exists. Therefore, as shown in FIG. 3, the thickness L _a3 of the resist layer 12a formed on the step portion 21 and the substrate 10
In order to find a condition that the thickness L _b3 of the resist layer 12b formed above is the same, the number of rotations is finely changed, and the number of rotations of the first rotating means 19 where the difference in thickness becomes zero, The number of rotations of the second rotating means 20 and the thickness of the resist at that time are shown in Table 2 below.

[0038]

[Table 2]

As is clear from Table 2, there are various conditions under which the difference between the thickness of the resist 12a on the step portion 21 and the thickness of the resist 12b on the substrate 10 under the step portion 21 becomes zero. It can be said that the resist thicknesses are different and the resist thickness depends on the rotation speed of the first rotating means 19. Therefore, by changing the rotation speed of the first rotating means 19 in the second and third steps of the resist coating process and the rotation speed of the second rotating means 20 in the third step, the step portion 21 is moved up and down. It was also confirmed that the film thickness can be adjusted while keeping the difference in the resist thickness at 0.

According to the above embodiment, the resist is applied such that the thickness of the resist layer 12a on the step portion 21 and the thickness of the resist layer 12b on the substrate 10 are equal even if there is the step portion 21. Therefore, the patterns of the resist layers 12a and 12b can be formed into an optimum shape during exposure and development.

[0041]

As described above in detail, in the resist coating apparatus according to the present invention, the means for fixing the substrate and the first centrifugal force in the horizontal direction from the center to the periphery of the substrate surface are applied to the substrate surface. Since the rotating means and the second rotating means for applying a centrifugal force in the direction perpendicular to the substrate surface are provided, even if there is a step on the resist application surface, the thickness of the resist on the step and the area below the step are reduced. The resist can be applied so that the resist has a uniform thickness.

Further, in the resist coating method according to the present invention, a step of dropping the resist onto the substrate and thereafter applying a centrifugal force in a horizontal direction to the substrate surface from the center of the substrate surface to the periphery thereof and vertical to the substrate surface. Since it includes a step of applying a centrifugal force in the direction, even if there is a step on the resist application surface, the resist is easily applied so that the thickness of the resist on the step is equal to the thickness of the resist below the step. can do. Therefore, the resist pattern can be formed into an optimum shape during exposure and development.

[Brief description of drawings]

FIG. 1 is a schematic perspective view showing an embodiment of a resist coating apparatus according to the present invention.

FIG. 2 is a plan view including a partially enlarged portion showing a substrate having a step portion used in the embodiment.

FIG. 3 is a cross-sectional view showing a case where resist is applied to a substrate having a step portion formed by using the resist applying apparatus according to the embodiment.

FIG. 4 is a cross-sectional view showing a case where a centrifugal force is applied in the direction perpendicular to the substrate surface after resist application.

FIG. 5 is a schematic perspective view showing a main part of a conventional resist coating apparatus.

FIG. 6 is a cross-sectional view showing a case where resist is applied to a substrate having a step portion using a conventional resist coating apparatus.

7A to 7C are cross-sectional views showing the steps of exposure and development which are one of the photolithography steps, and the exposure conditions are different in FIGS. 7A to 7C.

8A is a sectional view showing exposure and development of a resist on a step portion, and FIG. 8B is a sectional view showing exposure and development of a resist on a substrate.

9A is a sectional view showing exposure and development of a resist on a step portion, and FIG. 9B is a sectional view showing exposure and development of a resist on a substrate.

10A is a sectional view showing exposure and development of a resist on a step portion, and FIG. 10B is a sectional view showing exposure and development of a resist on a substrate.

[Explanation of symbols]

 10 Substrate 19 First Rotating Means 20 Second Rotating Means

Claims (2)

[Claims] 1. A means for fixing a substrate, a first rotating means for applying a centrifugal force in a horizontal direction to the substrate surface from a center of the substrate surface to a periphery, and a centrifugal force for applying a centrifugal force in a direction vertical to the substrate surface. A resist coating apparatus comprising: a second rotating unit. 2. A step of applying a centrifugal force in a horizontal direction to the substrate surface from the center of the substrate surface to a periphery thereof after dropping the resist on the substrate, and a step of applying a centrifugal force in a vertical direction to the substrate surface. A method of applying a resist, which is characterized in that