JPH03268417A - Resist applying method - Google Patents

Abstract

PURPOSE:To enable improving the in-plane uniformity of a resist film thickness by forming an application system, where no temperature difference exists, through setting of both resist solution and application atmosphere to the same temperature within the range of 24-30 deg.C and through application of the resist solution. CONSTITUTION:Both resist solution and application atmosphere are set to a same temperature within the range of 24-30 deg.C and the resist solution is applied subsequently. When a preset temperature exceeds 30 deg.C, not only a resist film thickness grows larger than required as the evaporation of a solvent is further activated but also the projection of the central part becomes too large. As a result, there is a possibility that an in-plane uniformity is impaired. Moreover, a surplus energy is required for heating. Therefore, a temperature higher than a preset one has little practical merit. Thus, it is possible to obtain an excellent in-plane uniformity, also when the resist solution and application atmosphere is set to the same temperature. In this manner, a resist application excellent in controllability and reproducibility can be performed with not improvement of the existing resist applicators.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a resist cloth method, and particularly to a method for improving the in-plane uniformity of resist film thickness.

[Summary of the invention]

The present invention provides a method for applying a resist solution by a spin coating method, in which both the resist solution and the coating atmosphere are heated for 24 hours.
By setting the same temperature in the range of 20°C or more and 30°C or less, the liquid level of the resist solution increases near the center of rotation due to the Weissenherck effect, thereby improving the in-plane uniformity of the resist film thickness. be.

[Prior Art] As a method for applying a resist solution onto a substrate such as a semiconductor wafer, a spin coating method has conventionally been widely applied.

The thickness of the coating film thus obtained (hereinafter referred to as resist film thickness) needs to be uniform with high precision within the wafer surface. This is because if the film thickness of the resist (especially photoresist) is non-uniform within the wafer surface, sensitivity to exposure light will be uneven and line width controllability will deteriorate. As the design rules for semiconductor devices become finer to the submicron to quarter micron level, there is a need to keep the variation range of resist film thickness within the wafer surface within approximately 30 to 50 layers. Ru. In recent years, it has become clear that the resist film thickness is sensitively affected by the temperature of the coating atmosphere, so resist coating equipment that can control the temperatures of the resist solution, substrate, coating atmosphere, and other parts has become widely used. has been done.

This resist coating device is commonly called a temperature control coater, and typically, as shown in FIG. 2, it includes surrounding means for shielding the resist coating environment from the external environment;
a spin coating means, an intake and exhaust means, which are housed within the surrounding means;
It is composed of temperature/humidity control means, resist solution supply means, and the like.

The enclosing means is composed of a downflow type chamber (1) in which air whose temperature and humidity are controlled flows from above to below, and the upper part of which is supplied with temperature and humidity controlled air (2). air into the chamber (1)
An air supply duct (3) is opened for introducing the air into the interior. The temperature and humidity controlled air sent from the air supply duct (3) is further removed from dust by an air filter (4) and then supplied into the chamber (1). The rotary coating means includes a chuck (8) that is coaxially attached to the rotating shaft (7) of the motor (12) and rotatably holds the substrate (5) such as a semiconductor wafer by fixing the substrate (5). Chuck (8
) is arranged to surround the outer periphery of the substrate (5) to prevent the resist solution from scattering as the substrate (5) rotates.
6) etc. At the bottom of the cup (6),
Splashes of resist solution (11), solvent vapor, etc. are removed from the chamber (
1) Exhaust duct (9) for suctioning and removing the air inside
) is provided. A resist solution supply pipe (lO) is opened above the center of the substrate (5) to discharge the resist solution (11) while controlling its temperature.

The resist solution supply pipe (10) has a double structure, as shown in an enlarged view of its tip in FIG. Water jacket (15) filled with water (14)
is surrounded by. The tip including the nozzle (16) is removably screwed into the main body so that it can be removed and cleaned at any time.

By the way, when the coating atmosphere and the resist solution are set at the same temperature and the resist film is discharged near the center of rotation of the substrate and spin coating is performed, the resist film tends to be thicker at the outer periphery than at the center of the substrate. be. This is because the linear velocity is higher at the outer periphery than at the center of the substrate, so the amount of evaporation of the solvent in the resist solution at the outer periphery is relatively large, increasing the viscosity of the resist solution and causing it to flow. This is because it becomes difficult.

Therefore, in the past, the temperature of the resist solution was adjusted to one level lower than the temperature of the coating atmosphere by taking advantage of the fact that the temperature of the resist solution and the temperature of the coating atmosphere could be controlled independently in a temperature control coater.
It is set about ~3'C higher. According to this method,
Since the temperature of the resist solution immediately after being discharged at the center of the substrate is higher than the ambient temperature, evaporation of the solvent is promoted and the resist film thickness at the center increases, improving in-plane uniformity. be able to.

[Problem to be solved by the invention]

However, as is clear from Figure 3, the resist? f
The tip of the I liquid supply pipe (10) is a water jacket)
Since it is not surrounded by (15), even if the temperature of the resist solution is set slightly higher than the temperature of the coating atmosphere as described above, the temperature of the resist film thickness will gradually decrease at the tip. Put it away. Also, a relatively narrow force,
The existence of a temperature difference of 1 to 3°C within the pipe (6) makes it difficult to control the temperature of the coating atmosphere. For these reasons, it is currently difficult to achieve high in-plane uniformity.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for solving these problems and improving the in-plane uniformity of resist film thickness using a coating system that does not have a temperature difference.

(Means for Solving the Problems) A resist coating method according to the present invention is proposed in order to achieve the above-mentioned object, and is a method of coating a resist solution on a rotating substrate. This method is characterized in that the resist solution is applied while the coating atmosphere is set to the same temperature within the range of 24° C. or more and 30° C. or less.

[Effect]

Non-uniformity in which the resist film thickness is thinner at the center of the substrate (and thicker at the periphery), that is, the in-plane distribution of resist i thickness, is generally determined by the temperature balance between the resist solution and the coating atmosphere, as described above. However, upon investigation by the present inventor, it became clear that in-plane distribution may occur even when these two temperatures are the same.Moreover, this It has been found that the in-plane distribution is noticeable when the set temperature is relatively low, but becomes less noticeable when the set temperature is relatively high.

This is considered to be because the contribution of the Weissenberg effect increases when the temperature is high.

The Weissenberg effect is that when a rod placed vertically in a viscoelastic fluid or a disk immersed in the fluid is rotated,
This is a phenomenon in which the fluid surface near the center of rotation bulges as it rotates. This is because when the viscoelastic fluid undergoes shear deformation,
This is because, in addition to tangential stress due to viscosity, normal stress is generated due to large deformation due to elastic displacement, and this normal stress tightens the fluid in the normal direction (direction perpendicular to the displacement direction). It is thought that a similar phenomenon occurs in the resist solution on the rotating substrate.

Now, when the internal energy is U and the entropy is S, the stress τ when the sample is equiregressively stretched (that is, temperature T=constant) by di is given thermodynamically by the following equation.

τ-(θU/θjriy T(θS/θff1)tHere, (θU/aj2)y represents the energy elasticity that appears due to intermolecular force, atomic force, etc., and -T(θS/θf
)y represents entropic elasticity that appears in relation to the arrangement of chain polymers. In the case of linear polymers such as resist materials, the energy elasticity is negligibly small, so the stress τ can be expressed only in terms of entropic elasticity as follows.

τ--T(θS/θff1)t When considering spin coating of resist solution, (θS
/θf)t is a negative value. This is because the orientation direction of the resist molecules is aligned due to the stress generated as the substrate rotates, so that the entropy S decreases. In other words,
As the temperature rises, the stress that tightens the resist material toward the center of rotation increases, causing the liquid level near the center of rotation to rise.

〔Example〕

Hereinafter, preferred embodiments of the present invention will be described based on experimental results.

In this example, the temperature control coater shown in FIG. 2 was a Clean Track Markm manufactured by Tokyo Electron.
-V type, a 5-inch wafer as the substrate, and a novolanque positive type photoresist (manufactured by Tokyo Ohka Kogyo Co., Ltd., trade name TSMR-V3) as the resist. Relative humidity: 50% 1 Application atmosphere temperature: 19-25
Change the rotation speed at constant speed by 4oo
As o r p m, the in-plane distribution of resist film thickness under each set temperature was investigated. The temperature of the resist solution was the same as the temperature of the coating atmosphere.

The results are shown in Figure 1. In the figure, the N axis has a thick resist film)
, the horizontal axis represents measurement points obtained by dividing the diameter of the wafer at predetermined intervals using numbers. However, the distance between each measurement point is 1, 2, 5.
and 5mm between No. 12 and No. 13, all other parts are 1
0 mm, and position No. 7 is the center of the wafer. This figure shows that when the set temperature is relatively low, the center of the wafer becomes concave, but as the temperature rises, the in-plane uniformity gradually improves, and good results are obtained above 24°C. It is clear that the Furthermore, as the temperature increases, the evaporation of the solvent is promoted and the viscosity of the resist solution increases, so the overall thickness of the resulting resist film also increases.

In conventional general resist coating, the temperature of the coating atmosphere is set to 2.
It has been carried out at a temperature of 2 to 23°C, but as is clear from FIG. 1, the in-plane uniformity is insufficient. Therefore,
Efforts have been made to make the temperature of the resist solution slightly higher than the ambient temperature, but according to the present invention, even if the temperature of the resist solution and the coating atmosphere are the same, the Weissenberg effect occurs in the central region. is raised, and in-plane uniformity is improved.

In the present invention, the upper limit of the set temperature is 30°C. If the set temperature exceeds 30'C, the resist film thickness will become larger than necessary due to more active evaporation of the solvent, and the bulge in the center may become too large, which may actually impair in-plane uniformity. This is because there are few practical advantages, such as additional energy required for heating.

〔Effect of the invention〕

As is clear from the above explanation, if the present invention is applied, excellent in-plane uniformity can be achieved even when the resist solution and coating atmosphere are set the same, so existing resist coating equipment can be used. It becomes possible to perform resist coating with excellent controllability and reproducibility without making any improvements.

FIG. 3 is a schematic cross-sectional view showing a typical configuration of a warm coater used in the resist coating method of FIG.

Claims (1)

[Claims] A resist coating method in which a resist solution is coated on a rotating substrate, wherein both the resist solution and the coating atmosphere are kept at a temperature of 24°C or higher and 30°C.
A resist coating method characterized by coating a resist solution at the same temperature within the following range.