US20050109992A1

US20050109992A1 - Photoresist cleaning solutions and methods for pattern formation using the same

Info

Publication number: US20050109992A1
Application number: US10/996,636
Authority: US
Inventors: Won Lee; Geun-su Lee; Sam Kim
Original assignee: Hynix Semiconductor Inc
Current assignee: SK Hynix Inc
Priority date: 2003-11-25
Filing date: 2004-11-23
Publication date: 2005-05-26
Also published as: KR20050050367A; KR100682188B1; US20070269752A1; US7364837B2

Abstract

Disclosed are photoresist cleaning solutions, which are used to clean semiconductor substrates before or after an exposing step when photoresist patterns are formed. Methods for forming patterns using the same are also disclosed. The cleaning solutions include H₂O and a nonionic surfactant compound represented by Formula 1. By spraying the disclosed cleaning solutions on a surface of the semiconductor substrate before or after exposing step to form a photoresist pattern, the desired pattern only is obtained and unnecessary patterns generated in undesired regions by ghost images are avoided as excess acid generated by the photoacid generator is neutralized and removed and damage to unexposed portions of the photoresist polymer is avoided.

wherein R₁and R₂are independently H, C₁-C₂₀alkyl, C₅-C₂₅alkyl aryl or C₁-C₁₀ester; m is 1 or 2; n is an integer ranging from 10 to 300; and o is 0 or 1.

Description

BACKGROUND

1. Technical Field
Photoresist cleaning solutions for rinsing semiconductor substrates before or after an exposing step during photoresist pattern formation are disclosed. More specifically, photoresist cleaning solutions are disclosed which comprise H₂O and a nonionic surfactant compound as an additive. Methods for forming a photoresist pattern using the same are also disclosed.
2. Description of the Related Art
Conventional methods for forming photoresist patterns on a semiconductor substrate comprise forming an underlying layer on a semiconductor substrate, forming a photoresist film on the underlying layer, and then exposing the photoresist film to light and developing the exposed film to obtain a photoresist pattern on a part of the underlying layer to be exposed. When a positive-type photoresist film is used, the photoresist film of the exposed region is removed by a developing solution to form the photoresist pattern.
When a photoacid generator is irradiated by a light source, it generates acid. After exposure to the light source, main chains or branched chains of polymer matrix react with the generated acid and are decomposed or cross-linked, so that the polarity of the polymer matrix is considerably altered. This alteration in polarity of the polymer matrix results in solubility differences between the exposed and the unexposed portions of the polymer in the developing solution. As a result, the exposed portions that have reacted with the acid dissolve in the developing solution and are removed.
Meanwhile, acid is also generated from the photoresist film in the unexposed area by ghost images formed in undesired regions during exposing step. The amount of acid generated by the ghost images is relatively small compared to the acid generated in the exposed area. However, the protecting group of the polymer compound in the photoresist can be detached during the baking step by small amounts of acid, so that the unexposed photoresist is dissolved in the developing solution and an undesired pattern is formed in the unexposed area. Therefore, a solution to this problem of acid damage to the unexposed photoresist polymers is needed.

SUMMARY OF THE DISCLOSURE

Photoresist cleaning solutions are provided that avoid undesired photoresist patterns caused by ghost images. The disclosed cleaning solutions neutralize or wash out small amount of acid generated in an area of a photoresist film that is not exposed to light. The cleaning solutions can be used before or after the exposing step to prevent diffusion of generated acid. Methods for forming a photoresist pattern using the disclosed photoresist cleaning solution are also disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photograph illustrating a photoresist pattern obtained from Comparative Example.
FIG. 2 is a photograph illustrating a photoresist pattern obtained from Example 3.
FIG. 3 is a photograph illustrating a photoresist pattern obtained from Example 4.

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

Photoresist cleaning solutions are disclosed comprising H₂O as a primary ingredient and a nonionic surfactant compound represented by Formula 1 as an additive:

wherein

- R₁and R₂are independently H, C₁-C₂₀alkyl, C₅-C₂₅alkyl or C₁-C₁₀ester;
- m is 1 or 2;
- n is an integer ranging from 10 to 300; and
- o is 0 or 1.

Preferably, R₁and R₂are independently H, C₁-C₁₂alkyl, C₁₂-C₂₀alkyl aryl or C₁-C₈ester; and n is an integer ranging from 50 to 150. R₁and R₂are more preferably independently selected from the group consisting of H, octyl, octyl phenyl, nonyl, nonyl phenyl, decyl, decyl phenyl, undecyl, undecyl phenyl, dodecyl and dodecyl phenyl. A specific example for the compound of Formula 1 is polyethylene glycol or polyethylene glycol monolaurate.
H₂O as a primary ingredient in the cleaning solutions is preferably distilled water.
Also, the photoresist cleaning solutions may further comprise an alcohol.
The alcohol is preferably selected from the group consisting of C₁-C₁₀alkyl alcohol and C₁-C₁₀alkoxyalkyl alcohol. Preferably, the C₁-C₁₀alkyl alcohol is selected from the group consisting of methanol, ethanol, propanol, iso-propanol, n-butanol, sec-butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol, 2,2-dimethyl-1-propanol. Also, the C₁-C₁₀alkoxyalkyl alcohol is preferably selected from the group consisting of 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 1-methoxy-2-propanol, 3-methoxy-1,2-propanediol and mixtures thereof.
When the disclosed photoresist cleaning solutions are used after the exposure step, they neutralize or wash out the small amount of acid generated in unexposed, undesirable or ghost image regions of the photoresist film. In addition, when the cleaning solutions are applied before the exposing step, acid generated after the exposing step diffuses slowly due to a thin water screen formed on the surface of the photoresist film, and small amounts of a photoacid generator may be washed out so that amount of generated acid is reduced in the subsequent exposure step.
In the disclosed photoresist cleaning solutions, the content of the nonionic surfactant compound of Formula 1 preferably ranges from 0.001 to 1 wt %, more preferably, from 0.005 to 0.05 wt %, based on total weight of the solution.
When the compound of Formula 1 is used in the amount of less than 0.001 wt %, the solution does not clean the photoresist film efficiently and patterns are formed in the undesired regions. When the compound of Formula 1 is used in the amount exceeding 1 wt %, the compound of Formula 1 may react with the photoresist, resulting in pattern deformation.
In the disclosed photoresist cleaning solutions, the content of the alcohol preferably ranges from 0 to 10 wt %, preferably from 0 to 5 wt %. The alcohol is optional and need not be used at all. However, when an alcohol is used, it is preferably used in the amount of at least 0.01 wt %.
When an alcohol is used in an amount greater than 10 wt %, the alcohol may dissolve the photoresist, resulting in pattern collapse.
The disclosed cleaning solutions are prepared by filtering a mixture solution comprising H₂O, the compound of Formula 1 and an alcohol with 0.2 μm filter.
A disclosed method for forming a photoresist pattern on a semiconductor substrate comprise conducting a photoresist cleaning step using a disclosed cleaning solution before or after the exposing step in addition to the conventional pattern formation process comprising exposing and developing steps.
An embodiment of a disclosed pattern formation method comprises:

- (a) coating a photoresist on the surface of an underlying layer formed on a semiconductor substrate to form a photoresist film;
- (b) soft-baking the photoresist film;
- (c) exposing the photoresist film to light;
- (d) cleaning the photoresist film using a disclosed cleaning solution;
- (e) post-baking the photoresist film; and
- (f) developing the photoresist film to form a photoresist pattern.

Herein, part (d) is performed by spraying the cleaning solutions from upper portion of a spin apparatus while spinning the semiconductor substrate.
As described above, by washing the photoresist film with the cleaning solutions after the exposing step, acid generated in small amounts on undesired regions of the photoresist film surface is neutralized or washed.
In another embodiment, a method for forming a photoresist pattern comprises:

- (a) coating a photoresist on the surface of an underlying layer formed on a semiconductor substrate to form a photoresist film;
- (b) cleaning the photoresist film using a disclosed cleaning solution;
- (c) soft-baking the photoresist film;
- (d) exposing the photoresist film to light;
- (e) post-baking the photoresist film; and
- (f) developing the photoresist film to form a photoresist pattern.

Part (b) is performed by spraying the cleaning solutions from upper portion of a spin apparatus while spinning the semiconductor substrate.
When the photoresist film is washed with the cleaning solutions before exposing acid generated after the exposing step diffuses slowly due to a thin water screen formed on the surface of the photoresist film and small amount of a photoacid generator in a photoresist composition can be washed out so that amount of acid to be generated is reduced in the subsequent exposing step.
In the above method, the cleaning the photoresist film using the photoresist cleaning solutions may be further performed after part (d) and before part (e).
Preferably, the baking step is performed at a temperature ranging from 70 to 200° C.
Preferably, exposing is performed using the exposure light selected from the group consisting of KrF (248 nm), ArF (193 nm), VUV (157 nm), EUV (13 nm), E-beam, X-ray and ion beam, and at an exposure energy ranging from 0.1 to 50 mJ/cm².
The developing step is performed using an alkali developing solution, preferably TMAH aqueous solution a concentration ranging from 0.01 to 5 wt %.
Additionally, there is provided a semiconductor device fabricated using the above-described method.
The disclosed cleaning solutions and pattern formation methods will now be described in greater detail by referring to the following examples, which are not intended to limit the scope of this disclosure.

EXAMPLE 1

Preparation of Cleaning Solutions (1)

0.1 g of polyethylene glycol having an average molecular weight of 4,600, and 1,000 g of H₂O were mixed and stirred for 1 minute. The resulting mixture was filtered through 0.2 μm filter to obtain a cleaning solution composition of the present invention.

EXAMPLE 2

Preparation of Cleaning Solutions (2)

0.1 g of polyethylene glycol monolaurate having an average molecular weight of 3,900, 30 g of ethanol and 970 g of H₂O were mixed and stirred for 1 minute. The resulting mixture was filtered through 0.2 μm filter to obtain a cleaning solution composition of the present invention.

COMPARATIVE EXAMPLE 1

Formation of Photoresist Pattern (1)

An underlying layer was formed on a silicon wafer treated with hexamethyldisilazane (HMDS), and TarF-7a-39 product of TOK Co., Ltd., a methacrylate-type photosensitizer, was spin-coated on the surface of the underlying layer to form a photoresist film at thickness of 3,500A. Then, the photoresist film was soft-baked in an oven at 130° C. for 90 seconds. After soft-baking, the photoresist film Was exposed to light using an ArF laser exposure device, and then post-baked in the oven at 130° C. for 90 seconds. When the post-baking was completed, the silicon wafer was dipped and developed in a 2.38 wt % aqueous tetramethylammonium hydroxide (TMAH) solution for 30 seconds to obtain a 150 nm contact hole pattern. However, it was found that patterns were also formed in undesired regions (see FIG. 1).

EXAMPLE 3

Formation of photoresist pattern (2)

An underlying layer was formed on a silicon wafer treated with HMDS, and TarF-7a-39 product of TOK Co., Ltd., a methacrylate-type photosensitizer, was spin-coated on the surface of the underlying layer to form a photoresist film at thickness of 3,500 Å. Then, the photoresist film was soft-baked in an oven at 130° C. for 90 seconds. After soft-baking, the photoresist film was exposed to light using an ArF laser exposure device, and 100 mL of the cleaning solution composition obtained from Example 1 was sprayed on the photoresist film from upper portion of a spin device while the silicon wafer was spun on a spin device.
Then, the photoresist film was post-baked in the oven at 130° C. for 90 seconds, and then developed in a 2.38 wt. % aqueous TMAH solution for 30 seconds to obtain a 150 nm contact hole pattern (see FIG. 2). As a result, it was found that no pattern was formed in the undesired regions in comparison with FIG. 1.

EXAMPLE 4

Formation of Photoresist Pattern (3)

An underlying layer was formed on a silicon wafer treated with HMDS, and TarF-7a-39 produced by TOK Co., Ltd., a methacrylate-type photosensitizer, was spin-coated as on the surface of the underlying layer to form a photoresist film at thickness of 3,500 Å. Then, the photoresist film was soft-baked in an oven at 130° C. for 90 seconds. After soft-baking, the photoresist film was exposed to light using an ArF laser exposure device, and 100 mL of the cleaning solutions from Example 2 was sprayed on the photoresist film from upper portion of a spin device as the silicon wafer was spun on a spin device.
Then, the photoresist film was post-baked in the oven at 130° C. for 90 seconds, and then developed in a 2.38 wt % aqueous TMAH solution for 30 seconds to obtain a 150 nm contact hole pattern (see FIG. 3). As a result, it was found that no pattern was formed in the undesired regions in comparison with FIG. 1.
As described above, the disclosed photoresist cleaning solutions comprising H₂O and a nonionic surfactant compound represented by Formula 1 as an additive, were sprayed on a semiconductor substrate before or after an exposure process for formation of photoresist pattern, thereby preventing the formation of unnecessary patterns generated in undesired regions by eliminating the acid damage to the unexposed polymer matrix.

Claims

1. A photoresist cleaning solution comprising H₂O and a nonionic surfactant compound represented by Formula 1:

wherein

R₁and R₂are independently H, C₁-C₂₀alkyl, C₅-C₂₅alkyl aryl or C₁-C₁₀ester;

m is 1 or2;

n is an integer ranging from 10 to 300; and

o is 0or 1.

2. The photoresist cleaning solutions according to claim 1, wherein R₁and R₂are independently H, C₁-C₁₂alkyl, C₁₂-C₂₀alkyl aryl or C₁-C₈ester; and n is an integer ranging from 50 to 150.

3. The photoresist cleaning solutions according to claim 2, wherein R₁and R₂are independently selected from the group consisting of H, octyl, octyl phenyl, nonyl, nonyl phenyl, decyl, decyl phenyl, undecyl, undecyl phenyl, dodecyl and dodecyl phenyl.

4. The photoresist cleaning solutions according to claim 1, wherein the compound of Formula 1 is polyethylene glycol or polyethylene glycol monolaurate.

5. The photoresist cleaning solutions according to claim 1, wherein the nonionic surfactant compound of Formula 1 is present in an amount ranging from 0.001 to 1 wt % based on total weight of the solution.

6. The photoresist cleaning solutions according to claim 5, wherein the content of the nonionic surfactant compound of Formula 1 is from 0.005 to 0.05 wt % based on total weight of the solution.

7. The photoresist cleaning solutions according to claim 1, further comprising an alcohol.

8. The photoresist cleaning solutions according to claim 7, wherein the alcohol is present from 0.01 to 10 wt % based on total weight of the solution.

9. The photoresist cleaning solutions according to claim 8, wherein the alcohol is present from 0.01 to 5 wt % based on total weight of the solution.

10. The photoresist cleaning solutions according to claim 8, wherein the alcohol is selected from the group consisting of C₁-C₁₀alkyl alcohol and C₁-C₁₀alkoxyalkyl alcohol.

11. The photoresist cleaning solutions according to claim 10, wherein the C₁-C₁₀alkyl alcohol is selected from the group consisting of methanol, ethanol, propanol, isopropanol, n-butanol, sec-butanol, t-butanol, 1-pentanol, 2-pentanol, 3-pentanol and 2,2-dimethyl-1-propanol.

12. The photoresist cleaning solutions according to claim 10, wherein the C₁-C₁₀alkoxyalkyl alcohol is selected from the group consisting of 2-methoxyethanol, 2-(2-methoxyethoxy)ethanol, 1-methoxy-2-propanol and 3-methoxy-1,2-propanediol.

13. A photoresist cleaning solutions comprising one or more of polyethylene glycol and polyethylene glycol monolaurate in an amount ranging from 0.001 to 1 wt %; an alcohol in an amount ranging from 0 to 10 wt %, respectively and H₂O.

14. The photoresist cleaning solutions according to claim 13, wherein the alcohol is ethanol.

15. The photoresist cleaning solutions according to claim 13, wherein each of polyethylene glycol and polyethylene glycol monolaurate is present in an amount ranging from 0.005 to 0.05 wt %, and the alcohol is present in an amount ranging from 0 to 5 wt %.

16. A method for forming a photoresist pattern, comprising:

(a) coating a photoresist on the surface of an underlying layer formed on a semiconductor substrate to form a photoresist film;

(b) soft-baking the photoresist film;

(c) exposing the photoresist film to light;

(d) post-baking the photoresist film; and

(e) developing the photoresist film to form a photoresist pattern, wherein the method further comprises cleaning the photoresist film using the photoresist cleaning solutions of claim 1 after part (a) and before part (b) or after part (c) and before part (d).

17. The method according to claim 16, wherein the exposure light source is selected from the group consisting of KrF (248 nm), ArF (193 nm), VUV (157 nm), EUV (13 nm), E-beam, X-ray and ion beam.

18. A semiconductor device fabricated using the method of claim 16.