JPH088163A - Pattern formation method - Google Patents

Abstract

PURPOSE:To suppress collapse phenomena even in case of forming a fine resist pattern by using the final rinse liquid lower in surface tension than normal pure water at least at the final stage of the rinse after developing a photoresist film. CONSTITUTION:Selective exposure is applied to a wafer 2, w.here a resist film is made on a substrate, according to the specified pattern, and then this wafer 2 is retained on the stage 13 of a processor 1. While rotating the wafer 2, developer is supplied from a nozzle 6 for supply of developer so as to perform development. Then, while rotating the wafer 2, the supply of pure water at normal temperature is started from a nozzle 7 for supply of pure water at normal temperature so as to wash away the developer. It is supplied with pure water where an interface activator lower in surface tension than the pure water at normal temperature as the final rinse liquid from the nozzle 8 for supply of the final rinse liquid. Then, the supply of this rinse liquid is stopped, and the number of revolutions of the wafer 2 is raised to dry the water 2.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pattern forming method in which a photoresist coating film is developed and then washed to form a desired resist pattern. This is for accurately forming a resist pattern.

[0002]

2. Description of the Related Art In a semiconductor device, a finer pattern is required as the data integration degree thereof increases. Specifically, 4M DRAM is 0.80 μm, 16M DRAM is 0.50 μm, 64M
0.35 μm for DRAM and 0.
A circuit pattern having a fine minimum processing dimension such as 25 μm is required.

In order to carry out such fine processing, in the photolithography process, the wavelength of the exposure light used has been shortened, and the research on the photoresist material has been advanced, and the results have been achieved.

Further, in order to improve the weak adhesion between the substrate and a phenol novolac resin, which is a typical base resin of the photoresist material as described above, the surface of the substrate is made hydrophobic by hexamethyldisilazane (HMDS). The technology of applying the chemical conversion is also in practical use. This is because when a hydrophobic photoresist coating film is formed on a hydrophilic substrate, the resist pattern easily collapses or peels off due to development processing or cleaning processing. It is intended to enhance the adhesion to the coating film.

As described above, by applying various techniques, fine processing of about 0.25 μm corresponding to 256 MDRAM is becoming possible.

[0006]

However, 256
After the MDRAM, that is, in the pattern formation of 0.25 μm or less, the collapse phenomenon of the resist pattern becomes a problem again.

The collapse phenomenon of the resist pattern is caused by the surface tension when the rinse liquid between the resist patterns is dried.
Lecture number A-3-4, announced in July 1993. That is, when pure water at room temperature having a very high surface tension is used as the rinse liquid, as shown in FIG.
When the pure water 32 at room temperature moves between the resist patterns 31 on the substrate 30 in the a direction, the resist patterns 31
A strong attractive force in the b direction is generated between them. Therefore, when the pure water 32 at room temperature is removed, as shown in FIG.
The resist pattern 31 is destroyed. The attractive force generated between the resist patterns 31 is considered to be proportional to the surface tension of the rinse liquid and inversely proportional to the pattern interval. Therefore, the finer the pattern, the more easily the resist pattern collapses.

Therefore, the present invention has been proposed in view of such conventional circumstances, and an object thereof is to provide a pattern forming method capable of suppressing the collapse phenomenon even when forming a finer resist pattern. .

[0009]

A pattern forming method according to the present invention is proposed to achieve the above-mentioned object, and is applied to a wafer on which a photoresist coating film subjected to selective exposure is formed. And a developing step of developing the photoresist coating film, and a rinsing step of removing the developing solution by using a final rinse solution having a surface tension lower than that of pure water at room temperature at least in the final stage of rinsing. When,
A desired resist pattern is formed through a drying step of drying the wafer.

Pure water is the most effective cleaning solution for the developing solution, but pure water at room temperature has a very large surface tension.
Therefore, in the present invention, it is intended to reduce the surface tension of the rinse liquid existing on the wafer by using a final rinse liquid having a surface tension lower than that of pure water at room temperature at least in the final stage of the rinse. .

For this purpose, pure water at room temperature is used as the rinse liquid at the beginning of the rinse process, and then pure water at the normal temperature is switched to the final rinse liquid, and pure water at room temperature is used from the middle of the rinse process to the final stage of the rinse. A method of continuing to use water and the final rinse liquid together with a method in which the pure water at room temperature and the final rinse liquid are used together for a certain period of time during the rinse process, and then the supply of pure water at normal temperature is stopped to make a final rinse at the final stage of the rinse process. A method of using the liquid alone may be used. Further, if the developer can be sufficiently washed, pure water at room temperature and the final rinse liquid may be used together throughout the rinse process, or the final rinse liquid may be used alone throughout the rinse process. Good.

The final rinse liquid preferably has a surface tension lower than that of pure water at room temperature and has high compatibility with pure water at room temperature, and hot pure water heated to a temperature higher than room temperature,
Pure water containing a surfactant, various organic solvents having compatibility with pure water, and the like can be used.

For example, the surface tension of pure water at room temperature (23 ° C.) is 72.3 dyn / cm, whereas the surface tension of warm pure water heated to 90 ° C. is reduced to 60.7 dyn / cm. In addition, the surface tension of pure water containing a surfactant can be significantly reduced depending on the type and concentration of the surfactant. In the organic solvent, for example, the surface tension of ethyl alcohol is 24.1 dyn / cm,
When spin drying is performed on a wafer that holds ethyl alcohol alone, the minimum processing dimension is 0.12.
It is expected that the collapse of the resist pattern of about μm can be suppressed. In addition to ethyl alcohol, methyl alcohol, isopropyl alcohol, dimethylformamide, tetrahydrofuran, dimethyl sulfoxide and the like can be used.

When the final rinse liquid is used as described above, it may be dried by a conventionally known drying method such as spin drying after the rinse step.

The final rinse liquid is under a vapor-liquid phase equilibrium established by bringing the vapor of a compound that gives a minimum boiling point in a mixed system with pure water into contact with the pure water layer held on the wafer. The mixed solution prepared on the wafer may be used. In this case, if the wafer is heated above the azeotropic point, it is not necessary to perform spin drying. Specifically, after development, the developer is thoroughly washed with pure water, and then a vapor of a compound that gives a minimum boiling point in a mixed system with pure water is supplied to mix under vapor-liquid phase equilibrium. By preparing the liquid, even if the wafer is heated to a temperature lower than 100 ° C., the water on the wafer can be vaporized. Lamp heating is suitable for heating the wafer.

Examples of the compound that gives a minimum boiling point in a mixed system with pure water include methyl alcohol, ethyl alcohol and isopropyl alcohol. Ethyl alcohol having a boiling point of 78.3 ° C. shows a minimum boiling point of 78.15 ° C. at 89.43 mol% of ethyl alcohol in a mixed system with pure water under the atmospheric pressure, and isopropyl alcohol having a boiling point of 82.4 ° C. , In a mixed liquid with pure water,
Under atmospheric pressure, it has a minimum boiling point of 80.1 ° C. with isopropyl alcohol 91.32 vol%. It is possible to vaporize the mixed solution at the lowest temperature (azeotropic point) by preparing the mixed solution to have the composition of an azeotropic mixture. However, in the present invention, the mixed solution is not always required. It is sufficient that it can be vaporized without adjusting the composition of the azeotropic mixture. The mixed solution may be vaporized at a lower temperature by reducing the pressure of the atmosphere.

By the way, the structure of the wafer on which the pattern is formed by applying the present invention is not limited at all.
For example, the photoresist coating film may be composed of a novolak-based positive photoresist material containing a sensitizer such as an azide-based photoresist, or may be a positive photoresist film composed of an alkali-soluble resin, a dissolution inhibitor, and a photo-acid generator. A chemically amplified resist material such as a three-component system, a positive-type two-component system comprising an alkali-soluble resin having a protected phenolic hydroxyl group, and a photoacid generator may be used.

[0018]

When the present invention is applied, the collapse phenomenon of the resist pattern in the drying process can be suppressed. This is because the surface tension of the rinsing liquid held on the wafer is small at the time when the rinsing step is completed, so that the attractive force generated during drying can be suppressed to be small.

In particular, when a mixed solution of a vapor of a compound which gives a minimum boiling point in a mixed system with pure water and pure water on the wafer is vaporized by heating the wafer, spin drying is not required, and therefore, the wafer is not dried. Pure water does not move between resist patterns and hardly generates attractive force due to surface tension between patterns.

Therefore, when the rinsing step and the drying step after development are performed by applying the present invention, fine resist
The next step such as etching using the resist pattern as a mask can be accurately performed without destroying the pattern. Further, this also makes it possible to further miniaturize the circuit pattern.

[0021]

EXAMPLES Specific examples to which the pattern forming method according to the present invention is applied will be described below.

Example 1 In this example, pure water containing a surfactant was used as the final rinse liquid, and after the photoresist coating development process, the rinse liquid supplied to the wafer was kept at room temperature during the rinse process. In this example, the desired resist pattern is formed by switching from pure water to pure water to which a surfactant has been added, and then spin drying.

Here, a series of processes in the developing process, the rinsing process, and the drying process were performed by the processing apparatus 1 shown in FIG. The processing apparatus 1 includes a stage 3 for chucking a wafer 2, a spindle 4 connected to the stage 3, a motor 5 for rotating the spindle 4, a developing solution supply nozzle 6, a room temperature pure water supply nozzle 7, and a final rinse solution. It is composed of a supply nozzle 8. Further, there are provided a developing cup 9 for preventing scattering of the developing solution, pure water, and final rinse solution shaken off from the wafer 2, and a drain port 10 for removing the shaken off liquid to the outside of the system. . Each supply pipe (not shown) for supplying any of the developing solution, pure water, and final rinsing solution to each nozzle is provided with a valve to control the start / stop of supply of the liquid to each nozzle. It is made possible.

In order to actually perform the treatment, the KrF excimer is applied to the wafer 2 on which the resist coating film made of the chemically amplified resist material (trade name: XP8843 manufactured by Shipley Co., Ltd.) is formed on the substrate in advance. This wafer 2 was held on the stage 3 of the above-mentioned processing apparatus 1 after being selectively exposed by a laser stepper according to a predetermined pattern having a line width of 0.25 μm. And, this wafer 2 is 30 rpm
While rotating at, the developing solution supply nozzle 6 supplies a developing solution manufactured by Tokyo Ohka Kogyo Co., Ltd. under the trade name NMD-W (containing 2.38% of tetramethylammonium hydroxide), and this developing solution is applied to the wafer surface. After coating, the supply of the developing solution was stopped, the rotation of the wafer 2 was stopped, and the development was performed for about 30 seconds.

Thereafter, while the wafer 2 was rotated at 1000 rpm, the supply of the room temperature pure water from the room temperature pure water supply nozzle 7 was started to wash away the developing solution. After about 10 seconds,
The supply of pure water at room temperature is stopped, and the pure water to which the surfactant has been added as the final rinse liquid is started to be supplied from the final rinse liquid supply nozzle 8. After about 10 seconds, the surfactant is added. The supply of purified water was stopped. Subsequently, the rotation speed of the wafer 2 was increased to 3000 rpm, and pure water containing a surfactant was shaken off to dry the wafer 2.

By the above processing, a 0.25 μm resist pattern could be formed without being destroyed or peeled off.

Example 2 In this example, hot deionized water heated to 90 ° C. was used as the final rinse liquid, pure water at room temperature and hot deionized water were used together during the rinse step, and after a certain period of time, the rinse step was performed. In the final stage, the above hot pure water is used alone.

In the present embodiment, hot pure water heated to 90 ° C. is supplied from the final rinse liquid supply nozzle 8 instead of supplying pure water containing a surfactant. A processing apparatus having the same configuration as that used in Example 1 was used.

Then, the steps up to the developing process of the wafer 2 are carried out in the same manner as in Example 1, and then, while the wafer 2 is rotated at 1000 rpm, the supply of the pure water at the normal temperature from the pure water supply nozzle 7 at the normal temperature is started. Then, after 10 seconds, the supply of hot pure water heated to 90 ° C. from the final rinse liquid supply nozzle 8 was also started. Then, after about 2 seconds, while the hot pure water was continuously supplied, the supply of the pure water at room temperature was stopped, and when the wafer was covered with the hot pure water, the supply of the hot pure water was also stopped. Subsequently, the number of rotations of the wafer 2 was increased to 3000 rpm, and this warm pure water was shaken off to dry the wafer 2.

By the above processing, a 0.25 μm resist pattern could be formed without collapse or peeling.

Example 3 In this example, ethyl alcohol was used as the final rinsing liquid, pure water at normal temperature and ethyl alcohol were used together during the rinsing process, and after being used for a certain period of time, ethyl alcohol was used in the final stage of the rinsing process. This is an example of using alcohol alone.

In this example, the final rinse liquid supply nozzle is used in the example 1 except that ethyl alcohol is supplied instead of the pure water containing the surfactant. A processing apparatus having the same configuration as that used was used.

Then, Example 1 is performed up to the wafer developing step.
Then, the supply of pure water at room temperature was started while the wafer was rotated at 1000 rpm, the developing solution was washed off for 10 seconds, and then the supply of ethyl alcohol as the final rinse solution was also started. After about 2 seconds, while continuing to supply the hot pure water, the supply of pure water at room temperature was stopped, and when the wafer was coated with ethyl alcohol, the supply of ethyl alcohol was also stopped. Then, the number of rotations of the wafer is set to 300.
The speed was increased to 0 rpm, and the ethyl alcohol was shaken off to dry the wafer.

By the above processing, a 0.25 μm resist pattern could be formed without collapse or peeling.

Example 4 In this example, as a final rinse liquid, a mixture prepared on the wafer in a vapor-liquid phase equilibrium state in which vapor of isopropyl alcohol and pure water held on the wafer are in contact with each other. This is an example using a solution.

Here, a series of processes in the developing process, the rinsing process, and the drying process were performed by the processing apparatus 11 shown in FIG. This processing apparatus 11 includes a stage 3 for chucking a wafer 2, a spindle 4 connected to the stage 3, a motor 5 for rotating the spindle 4, a developing solution supply nozzle 6, a room temperature pure water supply nozzle 7, and isopropyl alcohol. Nozzle 1 for supplying steam
8. Further, an IR lamp 20 for heating the wafer 2
Consists of. The developing cup 19 is a hermetically sealed container and is provided with a drain port 10 for exhausting and draining liquid.

In this processing apparatus 11, not only the start / stop of the supply of the developing solution and the pure water at room temperature can be controlled, but also the start / stop of the supply of isopropyl alcohol vapor from the vapor supply nozzle 18 and the IR lamp 20. The start / stop of heating can also be controlled.

To carry out the actual processing, the same steps as in Example 1 were carried out until the developing step and the step of washing away the developing solution with pure water at room temperature for 10 seconds, and then the pure water at room temperature was supplied. At the same time, the rotation of the wafer 2 was stopped, and a pure water film was formed on the wafer 2. Next, the isopropyl alcohol vapor was supplied from the vapor supply nozzle 18, and the wafer 2 was heated by the IR lamp 20.

At this time, the mixed solution is prepared on the wafer under the vapor-liquid phase equilibrium established by the contact between the vapor of isopropyl alcohol and the pure water layer held on the wafer. In a mixed system of isopropyl alcohol and pure water, isopropyl alcohol 91.3
Since the minimum boiling point is 80.1 ° C. at 2 vol%, when the wafer is heated to 80.1 ° C. or higher, the mixed solution on the wafer 2 is vaporized.

Therefore, by the above operation, the water on the wafer 2 is vaporized and the wafer 2 is dried without spin drying, and the 0.25 μm resist pattern is destroyed,
It could be formed without peeling.

The present invention is not limited to the one shown in the above embodiment. For example, in Example 1, deionized water prepared in advance was used as the final rinse liquid. However, deionized water at room temperature was supplied during the entire rinse process. A surfactant may be added to pure water. This is, for example, to connect a supply pipe for supplying a surfactant to the pure water supply nozzle 7 at room temperature or in the middle of the supply pipe connected to the nozzle 7 and to start / stop the supply of the surfactant. Can be controlled by a valve. In addition, the final rinse liquid supplied in Examples 2 and 3 is not used together with pure water at room temperature during the rinsing process, but is supplied at the same time when the supply of pure water at room temperature is stopped. Good. Furthermore, in Example 4, the pressure inside the closed system was reduced, and the azeotropic point was lower than that under atmospheric pressure.
The mixed solution may be vaporized.

[0042]

As is apparent from the above description, when the pattern forming method according to the present invention is applied, the collapse phenomenon of the resist pattern is suppressed and the photoresist coating film can be finely patterned.

Therefore, when the present invention is applied to the photolithography step in the semiconductor device manufacturing process, the reliability of fine pattern formation by excimer laser lithography can be greatly improved. Further, since further fine processing becomes possible, the contribution to high integration of the semiconductor device is extremely large.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of a processing apparatus used in a pattern forming method according to the present invention.

FIG. 2 is a schematic diagram showing another configuration example of a processing apparatus used in the pattern forming method according to the present invention.

FIG. 3 is a schematic perspective view showing a state in which pure water at room temperature moves between resist patterns.

FIG. 4 is a schematic perspective view showing a state in which pure water at room temperature is removed and the resist pattern is collapsed.

[Explanation of symbols]

 1, 11 Processing device 2 Wafer 3 Stage 4 Spindle 5 Motor 6 Developer supply nozzle 7 Normal temperature pure water supply nozzle 8 Final rinse solution supply nozzle 9, 19 Development cup 10 Drain port 18 Vapor supply nozzle 20 IR lamp

Claims (8)

[Claims] 1. A developing step of supplying a developing solution to a wafer on which a photoresist coating film subjected to selective exposure is formed to develop the photoresist coating film, and a surface tension higher than that of pure water at room temperature. A pattern forming method for forming a desired resist pattern through a rinsing step of removing the developing solution by using a low final rinsing solution at least in the final stage of rinsing, and a drying step of drying the wafer. 2. The pattern forming method according to claim 1, wherein the final rinse liquid is used together with pure water at room temperature during the rinse step. 3. The pattern forming method according to claim 1, wherein the final rinse liquid is used alone in the final stage of the rinse step. 4. The pattern forming method according to claim 1, wherein the final rinse liquid is used throughout the rinse process. 5. The final rinse liquid is warm pure water heated to a temperature higher than room temperature.
5. The pattern forming method according to claim 4. 6. The pattern forming method according to claim 1, wherein the final rinse liquid is pure water added with a surfactant. 7. The pattern forming method according to claim 1, wherein the final rinse liquid is an organic solvent. 8. The final rinse liquid is a gas phase formed by bringing vapor of a compound that gives a minimum boiling point in a mixed system with pure water into contact with a pure water layer held on a wafer.
2. The pattern forming method according to claim 1, which is a mixed solution prepared on the wafer under liquid phase equilibrium.