JPH0822944A - Formation of resist pattern - Google Patents

Abstract

PURPOSE:To prevent the generation of an undissolved part of a photoresist film at the time of developing of the film and to prevent a defective formation of a resist pattern. CONSTITUTION:A photoresist is applied on a wafer 1, which is inclined to form a resist pattern, and a photoresist film is formed. After a prebaking in a high-temperature tank 5, the wafer 1 is dipped in temperature-controlled pure water 7 for a prescribed time, such as five minutes or so. After that, the wafer 1 is immediately spin dried, is performed any exposure using ultraviolet rays and is dipped in ah alkaline aqueous solution 10, which is a developing solution for five minutes. Thereby, full water content is secured at the time of the exposure of the ultravilet rays and the generation of an undissolved part of the photoresist film at the time of developing of the photoresist film can be prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a resist pattern in a photolithography process for a semiconductor device or the like, and more particularly to measures for preventing defective formation of the resist pattern.

[0002]

2. Description of the Related Art Conventionally, formation of a resist pattern using a photoresist film has been indispensable in the manufacturing process of semiconductor devices, especially in the photolithography process. For this reason, the resist pattern forming technique is an important technique and is being developed in terms of materials and forming method. For example, as a photoresist material, a bisazide-based photoresist, which is a negative resist, has been conventionally used.
Since it is swollen by a developing solution, there is a limit to use it for fine processing, and at present, an orthodiazonaphthoquinone photoresist, which is a positive resist, is mainly used.

This orthodiazonaphthoquinone type photoresist is a mixture of orthodiazonaphthoquinone-5-sulfonic acid ester and novolak resin. The novolak resin is soluble in an alkaline aqueous solution, but it becomes insoluble when it is mixed with orthodiazonaphthoquinone-5-sulfonic acid ester. As shown in FIG. 4, when orthodiazonaphthoquinone-5-sulfonic acid is exposed to ultraviolet light having a wavelength of about 400 nm, the diazo group is lost and water is absorbed to form a carboxylic acid soluble in an alkaline aqueous solution. by this,
The portion irradiated with ultraviolet light is dissolved by the developing solution (alkali aqueous solution) to form a pattern of the photoresist film.

[0004]

By the way, in a light emitting diode or a semiconductor laser in which a mesa shape is provided on the substrate surface, or an OEIC in which a light emitting element is formed on a part of the substrate surface, a large step difference of several tens of μm exists on the substrate surface. Its shape is steep. For this reason, when patterning is performed on a wafer that is a substrate in the manufacturing process, a technique for performing patterning while completely covering the step portion with the photoresist film is important. That is, since the photoresist film thickness becomes extremely thin at the edge portion of the step, there is a possibility that the photoresist may have a film breakage and the edge portion may not be covered. In order to prevent this problem, it is effective to form a thick film having a thickness of 10 μm or more using a high-viscosity photoresist. However,
At that time, there is a problem that an undissolved portion of the photoresist film remains in a portion where the photoresist is originally dissolved and removed during development, resulting in defective formation of the resist pattern.

Then, as a result of analyzing the cause, it was presumed that it was due to lack of water during the development of the photoresist film. That is, as shown in FIG. 4, water is required in addition to ultraviolet light in order for the positive resist to become soluble in the developer which is an alkaline aqueous solution. On the other hand, after applying the photoresist to the semiconductor substrate, it is necessary to perform pre-baking in order to volatilize the solvent, but at this time, water is evaporated. However, when forming a pattern on a flat wafer surface, a low-viscosity photoresist is used, so the coating thickness is about several μm, and the water necessary for the reaction is quickly absorbed even after prebaking, and ultraviolet light and moisture are absorbed. And are sufficiently secured. Therefore, under such conditions, there was little risk of causing a problem of insufficient development. However, if the photoresist film becomes thicker to cover the abrupt steps or the viscosity of the photoresist solution becomes higher, the UV light exposure will be insufficient when the water content is not sufficiently absorbed after prebaking. Seems to be done.

The present invention has been made in view of the above problems, and an object thereof is to provide a method for forming a resist pattern by providing a means for securing moisture necessary for exposure of a prebaked photoresist film. The purpose is to eliminate defective formation of a resist pattern due to insufficient water content.

[0007]

In order to achieve the above object, the means of the invention of claim 1 is, as a method of forming a resist pattern, a photoresist is applied on a substrate to form a photoresist film. This is a method of providing a step, a step of pre-baking the photoresist film, and a step of humidifying the photoresist film after performing the pre-baking step.

The means taken by the invention of claim 2 is the method of claim 1.
In the invention, the method of applying a photoresist is a method of forming a photoresist film having a thickness of 10 μm or more.

The means taken by the invention of claim 3 is the method of claim 1.
Alternatively, in the invention of 2), an orthodiazonaphthoquinone photoresist is used as the photoresist.

The means taken by the invention of claim 4 is, in the invention of claims 1, 2 or 3, required in the humidifying step to allow water to permeate the whole photoresist film into pure water. It is a method of soaking for a time.

According to the invention of claim 5, in the invention of claim 1, 2 or 3, in the humidifying step, water is dropped on the photoresist film while rotating the substrate.

The means taken by the invention of claim 6 is the method of exposing the photoresist film to water vapor in the humidifying step in the invention of claims 1, 2 or 3.

[0013]

By the above method, in the first aspect of the invention, the moisture is retained in the photoresist film by the humidification after prebaking. Then, since the exposure to the ultraviolet light is performed in this state, the ultraviolet light and the moisture necessary for the exposure of the photoresist film are sufficiently secured, and the generation of the undissolved portion of the photoresist film due to the lack of the moisture, that is, the resist pattern. Formation defects are prevented.

According to the second aspect of the present invention, when the thickness of the photoresist film is 10 μm or more, it is difficult for moisture to permeate the entire area of the photoresist film during development of the photoresist film, and the photoresist film is caused by the lack of moisture. However, in such a case, sufficient water content is secured in the photoresist film and defective formation of the resist pattern is prevented.

According to the third aspect of the present invention, even when the orthodiazonaphthoquinone-5-sulfonic acid ester, which is a component of the positive resist which is apt to cause defective formation of the resist pattern, is used as the photoresist, the moisture required for the exposure is not sufficient. By being held, the reaction at the time of exposure to ultraviolet rays becomes reliable, and defective formation of the resist pattern is prevented.

In the invention of claim 4, it is possible to humidify the photoresist film without using a device dedicated to the humidifying step, and the humidifying step is simply performed.

In the fifth aspect of the present invention, the humidification of the photoresist film and the removal of excess water are performed at the same time, so that the number of steps can be reduced and the inline design of the steps can be easily performed.

According to the sixth aspect of the present invention, since the water is applied to the photoresist film without giving excess water, the step of removing the water is not necessary and the humidifying condition is controlled gently.

[0019]

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

(First Embodiment) First, the first embodiment will be described with reference to FIG. 1A to 1G are diagrams showing a resist pattern forming process in the first embodiment.

First, as shown in FIG. 1A, the wafer 1 which is a substrate on which a resist pattern is to be formed is divided into three layers.
While rotating in the arrow direction at 000 rpm, a photoresist solution is dropped from the resist dropping nozzle 3 onto the wafer 1 to form a photoresist film 2 by spin coating. In this example, a photoresist solution having a viscosity of 1300 cp was spin-coated at 3000 rpm for 20 seconds to obtain a photoresist film 2 having a film thickness of about 12 μm.

Next, as shown in FIG. 1B, the wafer 1 is placed on the wafer carrier 4 and the high temperature bath 5 under predetermined conditions is set.
I pre-baked it.

After that, as shown in FIG. 1C, the wafer 1 set on the wafer carrier 4 is immersed in pure water 7 whose temperature is controlled in the constant temperature bath 6. At this time, if the immersion time is short, the pattern formation is incomplete where the film thickness is thick such as the bottom of the step. On the contrary, if it is long, moisture is absorbed more than necessary and the adhesiveness of the photoresist film 2 is deteriorated. At times, adverse effects such as peeling of the photoresist film 2 become significant. Therefore, in this embodiment, the immersion time is set to 5 minutes as a time period in which pure water sufficiently penetrates the entire area of the photoresist film 2 and is not additionally absorbed.

Thereafter, as shown in FIG. 1 (d), the wafer 1 is immediately rotated to remove water on the surface of the wafer 1 to dry it, and then, as shown in FIG. 1 (e), irradiated with ultraviolet light. Exposure is performed.

Next, as shown in FIG. 1 (f), the developing tank 1
Development is carried out by immersing in an alkaline aqueous solution 10 which is a developer in 1 for 5 minutes. After that, as shown in FIG. 1G, post-baking is performed in the high temperature tank 5, and the resist pattern forming step is completed.

As a result, when the humidification is not carried out, there is a portion where the photoresist film is not completely dissolved at the time of development although the exposure is carried out by the ultraviolet light in the conventional process.
Although the resist pattern was formed poorly, in this embodiment, the resist pattern could be formed almost completely without forming an undissolved portion of the photoresist film during development. That is, even when a high-viscosity thick film positive resist (particularly 10 μm or more) is used when forming a photoresist pattern on a substrate having a large step, the water content in the photoresist film 2 during exposure to ultraviolet light is increased. It is possible to effectively prevent the generation of undissolved portions during development due to the lack of. In particular, the first embodiment has an advantage that the humidifying process can be easily performed by using the existing device without the device dedicated to the humidifying process.

(Second Embodiment) Next, a second embodiment will be described with reference to FIG. The first embodiment has an advantage that the humidifying step can be easily performed, but requires two steps of dipping in pure water and removing pure water.

Therefore, in the second embodiment, as shown in FIG.
As shown in (f), humidification and removal of pure water can be performed simultaneously in one step.

First, as shown in FIGS. 2 (a) and 2 (b),
Similar to the steps shown in FIGS. 1A and 1B of the first embodiment, a photoresist solution is applied on the wafer 1 to form a photoresist film 2, and then prebaking is performed.

Next, as shown in FIG. 2C, while rotating the wafer 1 at 3000 rpm as in the spin coating in the photoresist solution coating step,
Pure water is dropped from the pure water nozzle 12 onto the surface of the wafer 1. As a result, the photoresist film 2 is humidified, and at the same time, excess water is removed and removed. The time for dropping the pure water was 5 minutes for the same reason as in the first embodiment.

Then, FIGS. 1 (e) to 1 (g) of the first embodiment.
Similarly to the step shown in FIG. 2, the photoresist film 2 is exposed to ultraviolet light (see FIG. 2D), and after development (FIG. 2).
(See (e)) and post bake (see FIG. 2 (f)).

Therefore, in the second embodiment, the humidification and the removal of pure water can be simultaneously performed in one process, and the same device as that used in the photoresist coating process can be used. There is an advantage that the inline process design can be performed easily.

(Third Embodiment) Next, a third embodiment will be described with reference to FIGS. First, above
In the second embodiment, since the pure water and the photoresist are brought into direct contact with each other, excess pure water must be removed. Further, since the humidification is performed rapidly, the adhesiveness of the photoresist is deteriorated by the excessive humidification. In order to avoid this, it is necessary to strictly control the temperature of pure water and the humidification time during humidification. Therefore, the purpose of the third embodiment is to omit the step of removing water and to relax the control of humidifying conditions.

First, as shown in FIGS. 3 (a) and 3 (b),
Similar to the steps shown in FIGS. 1A and 1B of the first embodiment, the photoresist is applied to form the photoresist film 2.
After forming, the pre-baking is performed.

Next, as shown in FIG. 3C, the wafer carrier 4 on which the wafer 1 is placed is placed in the constant temperature and humidity bath 16. A high temperature tank 15 filled with pure water 14 is arranged in the constant temperature and humidity tank 16, and the pure water 14 is heated to about 80 ° C. in the high temperature tank 15. In this embodiment,
The wafer 1 was placed in a constant temperature and constant humidity tank 16 together with pure water 14 for about 10 minutes and humidified.

Then, FIGS. 1 (e) to 1 (g) of the first embodiment.
After the photoresist film 2 is exposed to ultraviolet light (see FIG. 3D) and the photoresist film 2 is developed (see FIG. 3E), as in the step shown in FIG. Post-baking is performed (see FIG. 3F), and the photoresist pattern forming process is completed.

In the third embodiment, the humidification can be performed by exposing the photoresist to a high humidity condition.
Since water vapor in the gas state is used, it is not necessary to remove excess water after humidification, which has the advantage of simplifying the process. Further, since the humidification is also performed gently, the time control for not giving excessive water can be loosened.

Although water vapor is generated by heating the pure water 15 in the high temperature bath 14 in the third embodiment, the present invention is not limited to this embodiment.
For example, it goes without saying that it is also effective to install the wafer in a thermo-hygrostat in which water vapor is generated from pure water by using other means such as ultrasonic waves.

[0039]

As described above, according to the invention of claim 1, as a method of forming a resist pattern, the photoresist film is humidified after application and prebaking of the photoresist film. The ultraviolet light and water necessary for the above-mentioned exposure can be sufficiently secured, and the defective formation of the resist pattern due to the lack of water can be effectively prevented.

According to the invention of claim 2, since the invention of claim 1 is applied to the case where the thickness of the photoresist film is 10 μm or more, it is difficult for water to permeate and the photoresist film due to lack of water is formed. Even in the case of a thick photoresist film in which an undissolved portion is likely to occur, defective formation of the resist pattern can be prevented.

According to the invention of claim 3, claim 1 or 2
Since the invention described above is applied to the case where the photoresist is orthodiazonaphthoquinone-5-sulfonate, the defective formation of the resist pattern can be prevented even when the positive photoresist is used.

According to the invention of claim 4, in the invention of claim 1, 2 or 3, by immersing the photoresist film in pure water for at least a time necessary for water to permeate the entire photoresist film. Since the photoresist film is humidified, the photoresist film can be humidified without using a device dedicated to the humidification process, and thus the humidification process can be simplified.

According to the fifth aspect of the present invention, in the first, second or third aspect of the present invention, the humidification is performed by dropping water onto the photoresist film while rotating the substrate. The film can be humidified and excess water can be removed at the same time, so that the number of steps can be simplified and the inline design of steps can be facilitated.

According to the invention of claim 6, in the invention of claim 1, 2 or 3, since the photoresist film is humidified by exposing the photoresist film to water vapor, the moisture is removed. It is possible to omit the steps and ease the control of the humidification conditions.

[Brief description of drawings]

FIG. 1 is a diagram showing a process of forming a resist pattern according to a first embodiment.

FIG. 2 is a diagram showing a resist pattern forming process according to a second embodiment.

FIG. 3 is a diagram showing a resist pattern forming process according to a third embodiment.

FIG. 4: Orthodiazonaphthoquinone irradiated with UV and H2
FIG. 4 is a reaction diagram showing a chemical change of carboxylic acid by O.

[Explanation of symbols]

 1 Semiconductor Substrate 2 Photoresist Film 3 Resist Dripping Nozzle 4 Wafer Carrier 5 High Temperature Tank 6 Constant Temperature Tank 7 Pure Water 10 Developer 11 Development Tank 12 Pure Water Nozzle 14 Pure Water 15 High Temperature Tank 16 Constant Temperature and Humidity Tank

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G03F 7/16 501 501 7/38 501

Claims (6)

[Claims] 1. A step of applying a photoresist on a substrate to form a photoresist film, a step of prebaking the photoresist film, and a step of humidifying the photoresist film after performing the prebaking step. And a resist pattern forming method. 2. The method of forming a resist pattern according to claim 1, wherein in the step of applying the photoresist, a photoresist film having a thickness of 10 μm or more is formed. 3. The method for forming a resist pattern according to claim 1, wherein an orthodiazonaphthoquinone photoresist is used as the photoresist. 4. The method for forming a resist pattern according to claim 1, 2 or 3, wherein in the moisturizing step, the photoresist film is immersed in pure water for a time necessary for water to permeate the entire photoresist film. A method for forming a resist pattern, comprising: 5. The method of forming a resist pattern according to claim 1, 2, or 3, wherein in the humidifying step, water is dropped onto the photoresist film while rotating the substrate. Method. 6. The method of forming a resist pattern according to claim 1, 2, or 3, wherein the photoresist film is exposed to water vapor in the humidifying step.