JP2002280294A - Substrate and method of forming photoresist layer - Google Patents

Abstract

(57) Abstract: A photoresist is formed flat on a substrate used for contact exposure to improve adhesion with a mask. SOLUTION: The height of a peripheral portion b on the surface of a substrate 11 is
The photoresist 12 is gradually lowered toward the periphery b1 of 1
Is applied by a spin coating method. As a result, the highest position a1 of the photoresist 12 becomes lower than the height a of the flat portion inside the peripheral portion. As a result, the protrusions and the like of the photoresist at the peripheral portion, which have occurred up to now, are eliminated, and a photoresist having a flat surface can be formed. Therefore, in the contact exposure, the adhesion to the mask is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a method for forming a photoresist layer on a substrate, wherein the photoresist is formed flat on the substrate.

[0002]

2. Description of the Related Art As a substrate used for forming a semiconductor integrated circuit or a semiconductor device, a silicon or compound semiconductor sliced into a thin and circular shape (called a wafer) is widely used. . Then, a photoresist having a predetermined viscosity dissolved in an organic solvent is applied on the substrate, a pattern of a mask is transferred to the photoresist, and the photoresist having the pattern formed is used as a mask for the substrate. To form a pattern. As a method of applying the photoresist,
A spin coating method of applying a photoresist by dripping a photoresist from a nozzle provided on the substrate while rotating the substrate at a predetermined speed at a high speed is mainly used. By this spin coating method, a resist is applied to a uniform thickness on the substrate.

A method of exposing a photoresist is a g-ray (43
6 nm), i-line (365 nm), or even shorter wavelength excimer lasers (248 nm, 193 nm) and other exposure light sources and projection optical systems are commonly used for reduction exposure, but recently, due to the diffraction limit in reduction exposure, Research on near-field exposure that forms a nanometer-order fine pattern on a substrate by exposing and developing a photoresist using near-field light that permeates through an aperture with a diameter sufficiently smaller than the wavelength of the irradiated light as a light source Has been made. In the case of near-field exposure, exposure is performed by bringing a mask into contact with a photoresist (contact exposure).

[0004]

Since the near-field light has a small propagation depth, the thickness of the photoresist cannot be increased as in the case of reduced exposure, and is applied only to a thickness within a range where the near-field light can reach. Can not. It has been confirmed that when a photoresist is applied by using the spin coating method as described above, the thickness of the photoresist becomes thicker at the peripheral portion of the substrate or a projection of the photoresist occurs due to the influence of surface tension. For this reason, when performing close contact exposure by near-field exposure, there is a problem that adhesion between the mask and the photoresist is poor, and a highly accurate fine pattern is formed and its reproducibility is poor. In addition, vacuum contact (hard contact) to firmly adhere by blowing air from the back side of the substrate and vacuuming.
In the case of the above, there is a similar problem. Further, there is a problem that the substrate is warped due to the protrusion of the resist or the like. Therefore, in particular, in contact exposure in which exposure is performed by bringing a photoresist and a mask into close contact with each other, it is required that there be no protrusion or the like of the photoresist at the peripheral portion of the substrate.

SUMMARY OF THE INVENTION In view of the above circumstances, an object of the present invention is to provide a substrate on which a photoresist can be formed flat in a plane, and a method for forming a photoresist layer on the substrate to flatten the photoresist. Things.

[0006]

The substrate of the present invention is a substrate having a surface coated with a photoresist by spin coating, wherein the height of the periphery of the surface of the substrate gradually decreases toward the periphery. It is characterized by having become.

According to a first method of forming a photoresist layer of the present invention, a photoresist is applied on a substrate by a spin coating method, and the photoresist is applied to a region above the photoresist and inside the periphery of the substrate. A shielding plate of a size to cover is installed, and at least a part of the photoresist at the peripheral edge is removed in the depth direction, and the upper surface of the photoresist at the peripheral edge is removed by the partial removal, thereby forming an area inside the peripheral edge. Is lower than the upper surface of the photoresist.

In a second method of forming a photoresist layer according to the present invention, a photoresist is applied by spin coating to a substrate having a peripheral portion whose surface gradually decreases toward the peripheral portion. In a region above the photoresist and inside the periphery of the substrate, a shielding plate large enough to cover the region is provided, and the photoresist at the periphery is at least partially removed in the depth direction. By removing the portion, the upper surface of the photoresist at the peripheral portion is made lower than the upper surface of the photoresist in a region inside the peripheral portion.

The photoresist at the periphery may be removed by reacting the photoresist with a reactive gas plasma.

[0010] The photoresist at the peripheral portion may be removed by sputter etching by irradiation with inert gas ions.

Further, the photoresist on the peripheral portion may be removed by sputter etching by irradiation of chemically active gas ions.

Further, the shielding plate may be brought into close contact with the photoresist.

[0013]

According to the substrate of the present invention, since the height of the peripheral portion of the substrate surface gradually decreases toward the peripheral edge, a photoresist is applied onto the substrate by spin coating. However, in the photoresist at the peripheral portion, the photoresist rises or protrudes at a position lower than the upper surface of the photoresist in the region inside the peripheral portion, and the surface of the photoresist becomes flat in the region inside the peripheral portion. For this reason, in the contact exposure in which the exposure is performed by bringing the mask and the photoresist into close contact, the adhesion between the mask and the photoresist is improved.

According to the first method of forming a photoresist layer of the present invention, a photoresist is applied onto a substrate by spin coating, and the photoresist is applied to a region above the photoresist and inside the periphery of the substrate. A shielding plate large enough to cover the region is installed, and at least a part of the photoresist at the peripheral portion is removed in the depth direction. By making the area lower than the upper surface of the photoresist, there is no protrusion or the like on the surface of the photoresist, and the flat photoresist in the area inside the periphery becomes the uppermost surface. For this reason,
In particular, in the case of contact exposure using near-field light, since the adhesion between the photoresist and the mask is improved, a highly reliable fine pattern can be obtained with high yield and good reproducibility.

Further, according to the second method of forming a photoresist layer of the present invention, a photoresist is formed by spin coating on a substrate in which the height of the surface of the peripheral portion gradually decreases toward the peripheral portion. Apply, in a region above the photoresist and inside the periphery of the substrate, a shielding plate of a size to cover the region is installed, and at least a part of the photoresist at the periphery is removed in the depth direction, With this partial removal,
By lowering the upper surface of the photoresist at the peripheral portion to be lower than the upper surface of the photoresist in a region inside the peripheral portion,
The surface of the photoresist inside the peripheral portion can be more reliably set as the uppermost surface.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings.

A substrate according to an embodiment of the present invention will be described. FIG. 1 is a cross-sectional view showing a state where a photoresist is applied on a circular substrate.

As shown in FIG. 1, a photoresist 12 used for contact exposure is spun on a substrate 11 in which the height of the surface of the peripheral portion (region b in the figure) gradually decreases toward the peripheral edge b1. It is applied by a coating method.

In the substrate 11 according to the present embodiment, since the height of the surface of the peripheral portion (region b) gradually decreases toward the peripheral edge b1, the peripheral portion of the photoresist 12 applied by the spin coating method is used. The highest point (a1) of the portion (region b) is located at a position lower than the upper surface (a) of the photoresist 12 in the region inside the peripheral portion, and the surface is flattened in the region inside the peripheral portion by spin coating. Is formed.

FIG. 4 shows a conventional substrate coated with a photoresist by a spin coating method.
FIG. 4 shows a cross-sectional view when performing contact exposure. FIG. 4A shows a normal contact exposure (contact exposure).
(B) shows the state of vacuum contact exposure (hard contact exposure) by spraying from the back surface of the substrate with air or an inert gas such as N ₂ and evacuation. In the case of FIG. 4A, the projections surrounded by the broken lines hinder the photoresist and the mask from adhering well. In the case of FIG. 4B, similarly, it can be seen that the protrusions at the peripheral edge are in the way, and the adhesion between the photoresist and the mask is poor at the portion surrounded by the broken line.

Therefore, by using the substrate as in the present invention, unlike the conventional contact exposure, poor contact at the peripheral portion does not occur, and the mask can be brought into good contact with the photoresist 12, and the yield can be increased. A highly reliable pattern can be obtained.

Next, a method for forming a photoresist layer according to the first embodiment of the present invention will be described. FIG. 2 is a schematic sectional view showing a state where a substrate is installed in a reaction chamber of a dry etching apparatus.

As shown in FIG. 2, the present dry etching apparatus is a general parallel plate type etching apparatus, in which a plus electrode plate 1 and a minus electrode plate 2 are arranged in parallel, and RF (high frequency) A high frequency voltage can be applied by the power supply 3. A substrate 21 on which a photoresist 22 is applied by a spin coating method is provided on the positive electrode plate 1, and a shielding plate 23 is disposed on the substrate 21 in close contact therewith.

The photoresist 22 is applied by a spin coating method.
Can be seen. The shielding plate 23 has a size to cover an area inside the area (peripheral edge) where the projection is formed.

In the method of forming a photoresist layer according to the present embodiment, the substrate 21 is placed on the positive electrode plate 1 and inert gas ions or chemically active gas ions are supplied from the negative electrode plate 2 by the RF power source 3. The electrode plate 1 is accelerated and irradiated, and the projections a of the photoresist 22 are partially removed by sputter etching. The etching is performed until the upper surface of the photoresist 22 in the peripheral region becomes lower than the upper surface of the photoresist 22 in the region covered with the shielding plate 23. Alternatively, all the photoresist on the periphery may be removed.

Instead of removing the photoresist 22 by sputter etching by irradiating gas ions,
It may be removed by reacting the photoresist 22 with a reactive gas plasma.

Before carrying the substrate 21 coated with the photoresist 22 into the reaction chamber of the etching apparatus,
It can be placed on the photoresist or it can be
After carrying the substrate 21 coated with 22 into the reaction chamber, the shielding plate held by the movable holding unit may be set before etching.

The shielding plate 23 can be made of a silicon wafer or the like. Further, it is preferable that the corner of the surface of the shielding plate 23 that is in contact with the photoresist 22 has a large curvature so as not to damage the photoresist 22 when it comes into contact with the photoresist 22.

Next, a method for forming a photoresist layer according to a second embodiment of the present invention will be described. FIG. 3 is a schematic configuration diagram showing a state where a substrate is installed in a reaction chamber of a dry etching apparatus. In the present embodiment, the shielding plate 23
Is different from the above-described first embodiment in that it is used in a non-contact manner, and the same elements as those in the above-described first embodiment are denoted by the same reference numerals and description thereof is omitted.

As shown in FIG. 3, a substrate 21 'on which a photoresist is applied by a spin coating method is provided on the positive electrode plate 1, and a shielding plate 23 is provided thereon with holding portions 24 and 24'. Thus, the substrate 21 'is held in a non-contact state.

In the method of forming a photoresist layer according to the present embodiment, the substrate 21 'coated with the photoresist is placed on the positive electrode plate 1 and the potential of the shield portion b and the potential of the shield plate 23 are reduced to zero. Then, the photoresist on the peripheral portion a not shielded by the shielding plate 23 is removed. As in the first embodiment, the method of removing the photoresist may be any of sputter etching by irradiation of inert gas ions or chemically active gas ions, or reactive gas plasma.

The arm portion 24 'of the holding portion is desirably thin enough so as not to hinder removal of the photoresist located below the arm portion.

In the present embodiment, the case where the holding portions 24 and 24 'are integrated with the plus electrode plate 1 has been described. The photoresist may be removed while rotating the plate 1. Alternatively, the structure of the positive electrode may be such that only the region on which the wafer rides can be rotated. Thereby, the removal of the photoresist located below the holding portion at the peripheral portion is not insufficient, and the photoresist can be uniformly removed at the peripheral portion.

In the above two embodiments of the photoresist forming method, the electrode structure of the etching apparatus is described as a parallel plate type. However, the present invention is not limited to this. Alternatively, an ion shower type may be used.

In the above two embodiments of the photoresist forming method, a conventional substrate is used as the substrate.
A substrate in which the height of the peripheral portion is gradually reduced toward the peripheral edge of the substrate may be used. Thus, when the photoresist is first applied, it is possible to prevent the upper surface of the photoresist at the peripheral portion from being higher than the resist inside the peripheral portion, and it is possible to ensure that it by etching.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a substrate of the present invention.

FIG. 2 is a schematic sectional view of an etching apparatus showing a photoresist layer forming method according to the first embodiment of the present invention.

FIG. 3 is a schematic configuration diagram of an etching apparatus showing a photoresist layer forming method according to a second embodiment of the present invention.

FIG. 4 is a cross-sectional view showing a conventional contact exposure mode.

[Explanation of symbols]

 1 Positive electrode 2 Negative electrode 3 RF power supply 11 Substrate 12 Photoresist 23 Shield plate

Claims (7)

[Claims] 1. A substrate having a surface coated with a photoresist by spin coating, wherein a height of a peripheral portion of the surface of the substrate gradually decreases toward the peripheral edge. substrate. 2. A photoresist is applied on a substrate by spin coating, and a shielding plate large enough to cover the photoresist is provided in an area above the photoresist and inside the periphery of the substrate. Removing at least a portion of the photoresist at the peripheral portion in the depth direction, and making the upper surface of the photoresist at the peripheral portion lower than the upper surface of the photoresist at a region inside the peripheral portion by partially removing the photoresist. A method of forming a photoresist layer. 3. A photoresist is applied by a spin coating method on a substrate in which the height of the surface of the peripheral portion is gradually reduced toward the peripheral portion. In a region inside the portion, a shielding plate large enough to cover the region is installed, and the photoresist at the peripheral portion is at least partially removed in the depth direction, and the photoresist at the peripheral portion is removed by partially removing the photoresist. Wherein the upper surface of the photoresist is lower than the upper surface of the photoresist in a region inside the peripheral portion. 4. The method according to claim 2, wherein the photoresist on the peripheral portion is removed by reacting a reactive gas plasma with the photoresist. 5. The method according to claim 2, wherein the photoresist at the peripheral portion is removed by sputter etching by irradiating inert gas ions. 6. The photoresist layer forming method according to claim 2, wherein the photoresist on the peripheral portion is removed by sputter etching by irradiating chemically active gas ions. 7. The method for forming a photoresist layer according to claim 2, wherein the shielding plate is brought into close contact with the photoresist.