Pattern formation method

Abstract

In the pattern formation method, a resist film is formed on a substrate, and a barrier film is formed on the resist film. Thereafter, with a liquid provided on the barrier film, pattern exposure is performed by selectively irradiating the resist film with exposing light through the barrier film. After the pattern exposure, the barrier film is exposed to a water displacing agent, and then, the resist film having been subjected to the pattern exposure is developed, so as to remove the barrier film and to form a resist pattern made of the resist film.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A, 1B, 1C and 1D are cross-sectional views for showing procedures in a pattern formation method according to Embodiment 1 of the invention;

FIGS. 2A, 2B and 2C are cross-sectional views for showing other procedures in the pattern formation method of Embodiment 1;

FIGS. 3A, 3B, 3C and 3D are cross-sectional views for showing procedures in a pattern formation method according to Embodiment 2 of the invention;

FIGS. 4A, 4B, 4C and 4D are cross-sectional views for showing other procedures in the pattern formation method of Embodiment 2;

FIGS. 5A, 5B, 5C and 5D are cross-sectional views for showing procedures in a conventional pattern formation method;

FIGS. 6A and 6B are cross-sectional views for showing other procedures in the conventional pattern formation method; and

FIG. 7 is a graph for explaining control of solubility of a resist in the pattern formation method of this invention.

DETAILED DESCRIPTION OF THE INVENTION

Embodiment 1

A pattern formation method according to Embodiment 1 of the invention will now be described with reference to FIGS. 1A through 1D and 2A through 2C.

First, a positive chemically amplified resist material having, for example, the following composition is prepared:

Base polymer: poly((norbornene-5-methylene-t-	2	g
butylcarboxylate) (50 mol %) - (maleic anhydride)
(50 mol %))
Acid generator: triphenylsulfonium trifluoromethane sulfonate	0.05	g
Quencher: triethanolamine	0.002	g
Solvent: propylene glycol monomethyl ether acetate	20	g

Next, as shown in FIG. 1A, the aforementioned chemically amplified resist material is applied on a substrate 101 so as to form a resist film 102 with a thickness of 0.35 μm.

Then, as shown in FIG. 1B, by using a barrier film material having the following composition, a barrier film 103 having a thickness of 0.03 μm is formed on the resist film 102 by, for example, spin coating:

Base polymer: polyvinyl hexafluoroisopropyl alcohol 1 g
Solvent: n-butyl alcohol         20 g

Next, as shown in FIG. 1C, the resultant barrier film 103 is baked with a hot plate at a temperature of 120° C. for 90 seconds, so as to improve the denseness of the barrier film 103.

Then, as shown in FIG. 1D, an immersion liquid 104 of water is provided between the barrier film 103 having been baked and a projection lens 106 by, for example, a puddle method. In this state, pattern exposure is carried out by irradiating the resist film 102 through the liquid 104 and the barrier film 103 with exposing light 105 of ArF excimer laser with NA of 0.68 having passed through a mask (not shown).

After the pattern exposure, as shown in FIG. 2A, the liquid 104 disposed on the barrier film 103 is removed, and subsequently, a water displacing agent 107 of liquid paraffin is sprayed onto the barrier film 103 for 10 seconds, thereby exposing the surface of the barrier film 103 to the water displacing agent 107.

Next, as shown in FIG. 2B, together with the barrier film 103 having been exposed to the water displacing agent 107, the resist film 102 having been subjected to the pattern exposure is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake).

Thereafter, the barrier film 103 is removed and the resultant resist film 102 is developed with a 2.38 wt % tetramethylammonium hydroxide developer. Thus, a resist pattern 102a made of an unexposed portion of the resist film 102 and having a line width of 0.09 μm is formed in a good shape as shown in FIG. 2C.

In this manner, according to Embodiment 1, in the surface treatment with the water displacing agent 107 shown in FIG. 2A, the surface of the barrier film 103 formed on the resist film 102 is exposed to the paraffin, that is, the water displacing agent 107, and hence, a droplet remaining on the barrier film 103 is incorporated into the paraffin. As a result, the droplet remaining on the barrier film 103 is easily evaporated to be removed. Thus, the droplet remaining on the barrier film 103 can be prevented from permeating into the resist film 102 through the barrier film 103, and hence, the acid generator or the like included in the resist film 102 is never extracted. In other words, the expected performance of the resist film 102 can be kept, resulting in forming the resist pattern 102a in a good shape.

Embodiment 2

A pattern formation method according to Embodiment 2 of the invention will now be described with reference to FIGS. 3A through 3D and 4A through 4D.

First, a positive chemically amplified resist material having, for example, the following composition is prepared:

Base polymer: poly((norbornene-5-methylene-t-	2	g
butylcarboxylate) (50 mol %) - (maleic anhydride)
(50 mol %))
Acid generator: triphenylsulfonium trifluoromethane sulfonate	0.05	g
Quencher: triethanolamine	0.002	g
Solvent: propylene glycol monomethyl ether acetate	20	g

water displacing agent, the resist film 202 having been subjected to the pattern exposure is baked with a hot plate at a temperature of 105° C. for 60 seconds (post exposure bake).

Next, as shown in FIG. 4C, the barrier film 203 is removed with, for example, a 0.05 wt % tetramethylammonium hydroxide aqueous solution (a diluted alkaline developer). Thereafter, the resultant resist film 202 is developed with a 2.38 wt % tetramethylammonium hydroxide developer. Thus, a resist pattern 202a made of an unexposed portion of the resist film 202 and having a line width of 0.09 μm is formed in a good shape as shown in FIG. 4D.

In this manner, according to Embodiment 2, in the surface treatment with the water displacing agent 207 shown in FIG. 4A, the surface of the barrier film 203 formed on the resist film 202 is exposed to the isoparaffin, that is, the water displacing agent 207, and hence, a droplet remaining on the barrier film 203 is incorporated into the isoparaffin. As a result, the droplet remaining on the barrier film 203 is easily evaporated to be removed. Thus, the droplet remaining on the barrier film 203 can be prevented from permeating into the resist film 202 through the barrier film 203, and hence, the acid generator or the like included in the resist film 202 is never extracted. In other words, the expected performance of the resist film 202 can be kept, resulting in forming the resist pattern 202a in a good shape.

In each of Embodiments 1 and 2, the barrier film for preventing direct contact, with the resist film, of the immersion liquid provided on the resist film is provided, and the barrier film of each embodiment is never mixed with the paraffin or the like used as the water displacing agent. However, if the resist film is directly exposed to the water displacing agent without providing the barrier film of each embodiment on the resist film, the resist film and the water displacing agent are mixed with each other, and hence, the thus formed resist pattern is in a defective shape.

Next, as shown in FIG. 3A, the aforementioned chemically amplified resist material is applied on a substrate 201 so as to form a resist film 202 with a thickness of 0.35 μm.

Then, as shown in FIG. 3B, by using a barrier film material having the following composition, a barrier film 203 having a thickness of 0.07 μm is formed on the resist film 202 by, for example, the spin coating:

Base polymer: polyacrylic acid 1 g
Solvent: isobutyl alcohol      20 g

Next, as shown in FIG. 3C, the resultant barrier film 203 is baked with a hot plate at a temperature of 120° C. for 90 seconds, so as to improve the denseness of the barrier film 203.

Next, as shown in FIG. 3D, an immersion liquid 204 of an aqueous solution including 5 wt % of cesium sulfate (Cs₂SO₄) is provided between the baked barrier film 203 and a projection lens 206 by, for example, the puddle method. In this state, pattern exposure is carried out by irradiating the resist film 202 through the liquid 204 and the barrier film 203 with exposing light 205 of ArF excimer laser with NA of 0.68 having passed through a mask (not shown).

After the pattern exposure, as shown in FIG. 4A, the barrier film 203 is exposed to a water displacing agent 107 of liquid isoparaffin for 20 seconds by, for example, the puddle method.

Then, as shown in FIG. 4B, the water displacing agent 207 is removed by a shaking treatment, and thereafter, together with the barrier film 203 having exposed to the

Furthermore, the barrier film materials described in the respective embodiments are merely examples, and as a base polymer, that is, the principal component of the barrier film material, may be polyvinyl alcohol, polyacrylic acid or polyvinyl hexafluoroisopropyl alcohol.

Moreover, the thickness of the barrier film is 0.03 μm through 0.07 μm in each embodiment. However, the thickness is not limited to this range but the lower limit of the thickness of the barrier film is a thickness capable of preventing a component of the resist film from eluting into the immersion liquid or preventing the immersion liquid from permeating into the resist film, and the upper limit of the thickness is a thickness that does not prevent transmission of the exposing light and can be easily removed. Also, the barrier film is subjected to the thermal treatment after its formation in each embodiment, but such a thermal treatment of the barrier film is not always necessary but may be appropriately performed depending upon the composition, the thickness and the like of the barrier film.

Also in Embodiment 1, cesium sulfate may be included in the immersion liquid as in Embodiment 2 for increasing the refractive index of the liquid. The compound thus included in the liquid is not limited to cesium sulfate but may be phosphoric acid (H₃PO₄). Furthermore, a surface active agent may be added to the liquid.

Although the exposing light is ArF excimer laser in each embodiment, the exposing light is not limited to it but may be KrF excimer laser, Xe₂ laser, F₂ laser, KrAr laser or Ar₂ laser instead.

Furthermore, the puddle method is employed for providing the liquid onto the barrier film in each embodiment, which does not limit the invention, and for example, a dip method in which the whole substrate is dipped in the liquid may be employed instead.

Moreover, the composition of the chemically amplified resist described in each embodiment is merely an example and the chemically amplified resist may have another composition. Although a positive chemically amplified resist is used for forming the resist film in each embodiment, the present invention is applicable also to a negative chemically amplified resist. Furthermore, the invention is applicable not only to a chemically amplified resist but also to a general resist.

As described so far, according to the pattern formation method of this invention, a fine pattern can be formed in a good shape through the immersion lithography, and the invention is useful for, for example, a pattern formation method employing the immersion lithography.

Claims

1. A pattern formation method comprising the steps of: forming a resist film on a substrate;forming a barrier film on said resist film;performing pattern exposure by selectively irradiating said resist film with exposing light through said barrier film with a liquid provided on said barrier film;exposing said barrier film to a water displacing agent after the pattern exposure; andremoving said barrier film and forming a resist pattern made of said resist film by developing said resist film having been subjected to the pattern exposure after exposing said barrier film to said water displacing agent.

2. The pattern formation method of claim 1, wherein said water displacing agent is paraffin or isoparaffin.

3. The pattern formation method of claim 1, wherein a spraying method or a puddle method is employed in the step of exposing said barrier film to a water displacing agent.

4. The pattern formation method of claim 1, further comprising, after the step of exposing said barrier film to a water displacing agent, a step of subjecting said resist film to a thermal treatment.

5. The pattern formation method of claim 1, wherein said barrier film includes a polymer made of polyvinyl alcohol, polyacrylic acid or polyvinyl hexafluoroisopropyl alcohol.

6. The pattern formation method of claim 1, further comprising, after the step of forming a barrier film and before the step of performing pattern exposure, a step of subjecting said barrier film to a thermal treatment.

7. The pattern formation method of claim 1, wherein said liquid is water.

8. The pattern formation method of claim 1, wherein said liquid is an acidic solution.

9. The pattern formation method of claim 8, wherein said acidic solution is a cesium sulfate aqueous solution or a phosphoric acid aqueous solution.

10. The pattern formation method of claim 1, wherein said exposing light is KrF excimer laser, Xe2 laser, ArF excimer laser, F2 laser, KrAr laser or Ar2 laser.

11. A pattern formation method comprising the steps of: forming a resist film on a substrate;forming a barrier film on said resist film;performing pattern exposure by selectively irradiating said resist film with exposing light through said barrier film with a liquid provided on said barrier film;exposing said barrier film to a water displacing agent after the pattern exposure;removing said barrier film after exposing said barrier film to said water displacing agent; andforming a resist pattern made of said resist film by developing said resist film having been subjected to the pattern exposure after removing said barrier film.

12. The pattern formation method of claim 11, wherein said water displacing agent is paraffin or isoparaffin.

13. The pattern formation method of claim 1, wherein a spraying method or a puddle method is employed in the step of exposing said barrier film to said water displacing agent.

14. The pattern formation method of claim 11, further comprising, after the step of exposing said barrier film to a water displacing agent, a step of subjecting said resist film to a thermal treatment.

15. The pattern formation method of claim 1, wherein said barrier film includes a polymer made of polyvinyl alcohol, polyacrylic acid or polyvinyl hexafluoroisopropyl alcohol.

16. The pattern formation method of claim 11, further comprising, after the step of forming a barrier film and before the step of performing pattern exposure, a step of subjecting said barrier film to a thermal treatment.

17. The pattern formation method of claim 11, wherein said liquid is water.

18. The pattern formation method of claim 1, wherein said liquid is an acidic solution.

19. The pattern formation method of claim 18, wherein said acidic solution is a cesium sulfate aqueous solution or a phosphoric acid aqueous solution.

20. The pattern formation method of claim 1, wherein said exposing light is KrF excimer laser, Xe2 laser, ArF excimer laser, F2 laser, KrAr laser or Ar2 laser.