JPH07295210A - Light reflection preventing material and pattern forming method - Google Patents

Abstract

(57) [Summary] (Modified) [Structure] A light antireflection material containing a quaternary ammonium compound represented by the following general formula (I). R ¹ ₄ N ⁺ -R ²
(I) Example A light reflection preventing film made of this light reflection preventing material is formed as an upper layer of a tetraethylammonium hydroxide photoresist layer, and after exposing the photoresist layer, the light reflection preventing film is removed to form a pattern. Form. [Effect] The reflected light on the surface of the photoresist layer is reduced,
It is possible to reliably prevent deterioration of pattern dimension accuracy due to optical multiple interference in the resist layer, and it is simple and highly productive.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light-reflecting material and a pattern forming method used in photolithography using a photoresist, and more particularly, even when a step is present on the substrate surface, it is possible to perform fine patterning with high accuracy. TECHNICAL FIELD The present invention relates to a light-reflecting anti-reflection material and a pattern forming method that enable patterning to be processed.

[0002]

2. Description of the Related Art Recently, as semiconductor integrated circuits have become highly integrated and highly densified, it has become necessary to improve the precision of various strict pattern dimensions in the pattern forming process.

As is well known, a method generally called photolithography is used for forming various fine patterns. A reduction projection exposure machine (stepper) is generally used as an exposure machine, but since light exposure is performed with a single wavelength, light interference occurs in the photoresist film. That is, light enters the photoresist film and is reflected from the substrate,
Although the light is reflected and passes through the interface between the photoresist and the air, the reflectance at the interface between the photoresist film and the air changes when the film thickness of the photoresist changes. In this case, the film thickness of the photolithography changes in the step portion, but there is a problem that the exposure amount changes due to the change in the film thickness, and the size changes, and the accuracy decreases. The decrease in dimensional accuracy means
Not only can an accurate pattern size not be processed, but also the dimensional accuracy of the alignment mark for alignment exposure decreases, leading to a decrease in alignment accuracy.

The light-scattering state on the substrate will be described below. As shown in FIG.
The interference of the reflected light from the interface of the resist film (2) and the interface of the resist film (2) -air occurs, but when the resist film thickness changes, the in-film interference light intensity increases or decreases. That is, strong optical interference (overexposure) or weak optical interference (underexposure) occurs depending on the variation of the resist film thickness. Since the resist film thickness varies in the step portion of the substrate surface, the overexposed portion and the underexposed portion appear periodically according to the variation of the resist film thickness. That is, when an attempt is made to form a line pattern that intersects with a step, the line width periodically fluctuates in the step portion and becomes thicker.

A multi-layer resist method or an ARC method has been proposed as a method for solving these problems caused by the unevenness of the substrate surface and performing good patterning.
However, the multi-layer resist method (Japanese Patent Laid-Open No. 51-10775, etc.) requires two or three resist layers, and then transfers the pattern to form a resist pattern serving as a mask, which requires a large number of steps and thus leads to high productivity. There is a problem of being bad. In addition, the dimensional accuracy is reduced due to the reflected light from the intermediate layer.

On the other hand, Anti Reflective
Coat; ARC method (Japanese Patent Laid-Open No. 59-93448)
Is a light absorption type antireflection film formed under the resist film, but since the antireflection film is etched after the resist pattern is formed, the dimensional accuracy is greatly reduced due to its prescription,
Since the number of etching processes is increased, productivity is also deteriorated.

Recently, as a method for solving the above problems and suppressing the light interference in the resist film, a transmission type antireflection film Anti is used.
Reflective Coat On Resis
t; ARCOR method (Japanese Patent Laid-Open No. 626252/1987) has been proposed.

The ARCOR method is a method including a step of forming a transparent antireflection film on a resist and peeling after exposure, and is a method of forming a fine pattern with high precision and alignment accuracy by the simple method. . In this case, if a low-refractive-index material perfluoroalkyl compound (perfluoroalkylpolyether, perfluoroalkylamine) is used as the antireflection film, the reflected light at the resist-antireflection film interface is significantly reduced and the dimensional accuracy is improved. To do.

However, since the perfluoroalkyl compound has a low compatibility with organic substances, CFC or the like is used as a diluting solution for controlling the coating film thickness.
As is well known, the use of CFCs is currently a problem from the viewpoint of environmental protection. Further, the above-mentioned compounds have a problem in uniform film forming property, and cannot be said to be sufficient as an antireflection film. Moreover, before development of the photoresist, the antireflection film must be peeled off with chlorofluorocarbon, so that
A system for stripping the antireflection film must be added to the conventional device, and the cost of the CFC-based solvent is considerably high, which is a major disadvantage in terms of practical use.

Here, if it is attempted to peel off the antireflection film without adding it to the conventional apparatus, it is most desirable to peel off using the developing unit. Therefore, since the solution used in the developing unit for the positive type photoresist film is the alkaline aqueous solution which is the developing solution and the pure water which is the rinse solution, the antireflection film material which can be easily peeled off with these solutions is desirable. A water-soluble or alkaline water-soluble material is required as the material for the prevention film.

The present invention has been made in view of the above circumstances, and it is possible to form a fine pattern with high precision and alignment accuracy by a simple, highly productive and reproducible method. It is an object of the present invention to provide a preventive material and a pattern forming method using the same.

[0012]

Means and operation for solving the problems] The present inventor has conducted extensive investigations to achieve the above objects, as the light reflective preventive material, the following formula _{^{(I) R 1 4 N +}} - R 2 ... (I) [wherein R ¹ is the same or different alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms or hydroxyalkyl group having 1 to 6 carbon atoms, R ² is hydroxyl group, carbon number 1 to 6 mono- or dicarboxyl group, fluoro group, hydrogenated difluoro group, chloro group, bromo group, sulfonyl group,
Represents a sulfonyl hydride group or a methylcarbonyl group. ]
It was found that an excellent antireflection effect can be provided by using a compound containing a quaternary ammonium compound represented by

That is, the quaternary ammonium compound of the above formula (I) has a high water content and is deliquescent, and the light antireflection film formed of this light antireflection material has a high water content and a high water content. Has a low refractive index of 1.33, which corresponds to a low refractive index and an ideal refractive index of 1.30.
Therefore, unlike the conventional perfluoroalkyl compound (JP-A-62-62520), it is water-soluble or alkali-water-soluble, and water can be used as a stripping solution, which is simple and easy. The inventors have found that they can be used and have completed the present invention.

Therefore, the present invention provides a light reflection preventing material comprising a quaternary ammonium compound represented by the above general formula (I) and a light reflection preventing material comprising the above light reflection preventing material as an upper layer of a photoresist layer. There is provided a pattern forming method, which comprises forming a film, exposing the photoresist layer, and then removing the light reflection preventing film.

The present invention will be described in more detail below. The antireflection material of the present invention contains a quaternary ammonium compound represented by the following general formula (I) as a main component. R ¹ ₄ N ⁺ -R ² (I) [wherein R ¹ is the same or different alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms or hydroxyalkyl group having 1 to 6 carbon atoms] , R ² is a hydroxyl group, a mono- or dicarboxyl group having 1 to 6 carbon atoms, a fluoro group, a hydrogenated difluoro group, a chloro group, a bromo group, a sulfonyl group,
Represents a sulfonyl hydride group or a methylcarbonyl group. ]

Examples of such quaternary ammonium compounds include tetraethylammonium hydroxide, tetra-n-propylammonium hydroxide, tetra-n-butylammonium hydroxide, tetramethylammonium acetate, choline hydroxide and tetramethyl. Examples include ammonium carbonate and the like.

The quaternary ammonium compound is usually
The light reflection preventing material is prepared by dissolving it in a solvent such as water or alcohol, and the concentration of the quaternary ammonium compound is preferably 0.1 to 50% by weight, particularly preferably 0.5 to 10% by weight. .

In addition to the above quaternary ammonium compound, a surface active agent, various water-soluble polymers and the like can be added to the light reflection preventing material of the present invention. In this case, examples of the surfactant include betaine-based surfactants, amine oxide-based surfactants, amine carboxylate-based surfactants, polyoxyethylene alkyl ether-based surfactants, and fluorine-based surfactants thereof. And the like, and the addition amount thereof is preferably 0.0001 to 10 parts by weight, particularly 0.01 to 1 part by weight, relative to 100 parts by weight of the quaternary ammonium compound.

Further, in order to improve the film forming property, various water-soluble polymers such as polyvinyl alcohol, polyacrylic acid, polymethacrylic acid, polyvinylpyrrolidone, polyethylene oxide, amylose, dextran, cellulose and pullulan are added to the quaternary ammonium compound. 100
3 to 300 parts by weight, preferably 30 to 1 part by weight
The addition of 00 parts by weight is optional. If the added amount is less than 3 parts by weight, the film formability may deteriorate.
If it exceeds 0 part, the antireflection effect may be lowered.

In order to form a resist pattern using the light reflection preventing material of the present invention, a known method can be adopted, and for example, the lithography process shown in FIG. 1 can be used. First, a photoresist layer 2 is formed on a substrate 1 such as a silicon wafer by a method such as spin coating, and the light reflection preventing material of the present invention is applied onto the photoresist layer 2 by a method such as spin coating. The light antireflection film 3 is formed, and the light antireflection film 3 is exposed to ultraviolet rays 4 having a wavelength of 200 to 500 nm in a desired pattern shape by a reduction projection method, that is, the portion A in FIG. The resist pattern 5 can be formed by a method of removing the light antireflection layer 3 and developing with a developing solution.

In this case, pure water can be used as the diluting liquid. Further, the removal of the light antireflection layer can be carried out by using a normal positive photoresist developing unit, and can be easily performed by rinsing with pure water.

As the light antireflection film, it is most effective to form a film having a refractive index of about 1.30 on the photoresist as a uniform film having a thickness of about 700Å. Even if the refractive index is about 1.30, it is impossible to form a coating film, or a material having poor coating film uniformity cannot obtain an antireflection effect on the entire surface of the substrate. The light reflection preventing material of the present invention is excellent in coating uniformity, and by spin coating on the photoresist layer, it is possible to suppress repelling, uneven coating, etc. and form a uniform film on the entire surface of the substrate.

Here, the light scattering reduction effect of the light reflection preventing material of the present invention will be described with reference to FIGS. Figure 2
When the resist layer 2 is simply formed on the substrate 1 as shown in FIG. 3, the incident light I _{o undergoes} considerable reflection I _r1 at the air-resist layer interface, the incident light amount is lost, and the light entering the resist layer 2 is lost. _Reflects I _r2 at the resist layer-substrate interface,
Therefore, the reflected light I _r2 is repeatedly reflected I _r3 again at the resist layer-air interface, so that multiple interference occurs in the resist layer.

On the other hand, by forming the light reflection preventing film of the present invention on the resist layer 2 as shown in FIG. 3, reflection of incident light I _{o at} the air-light reflection preventing film interface (I _r4 ), The reflection (I _r5 ) at the light antireflection film-resist layer interface can be reduced. Further, when the film thickness of the light reflection preventing film is set so that the phases of I _r6 and I _r7 are opposite to each other, the phases of the lights are opposite to each other, so that they weaken each other and the multiple interference of the lights in the resist layer 2 is suppressed. It

From the principle of antireflection, assuming that the refractive index of the resist layer with respect to the exposure light is n and the wavelength of the exposure light is λ, the refractive index n ′ of the light antireflection film is √n, and its film thickness is λ /
The reflectance (amplitude ratio) of this light antireflection film decreases as it approaches an odd multiple of 4n '. That is, since the refractive index of the phenol novolac-based resist layer is about 1.70, the optimum refractive index required for the light antireflection film is about 1.30, which corresponds to light with a wavelength of 365 nm (i-line). The optimum thickness of the thin film is an odd multiple of about 700Å. According to the light reflection preventing material of the present invention, the optimum refractive index can be brought as close as possible.

[0026]

In the conventional pattern formation by photolithography using a photoresist material, when a pattern is formed on a substrate surface having a step, the film thickness of the resist layer fluctuates in the step portion of the substrate, so that optical interference occurs. However, according to the present invention, such a problem can be solved, and a transparent light antireflection film is formed on the photoresist layer to prevent the dimensional accuracy from decreasing. It is possible to reduce the reflected light and surely prevent the deterioration of the pattern dimension accuracy due to the optical multiple interference in the resist layer, and it is simple and highly productive.

[0027]

EXAMPLES The present invention will be specifically described below by showing Examples and Comparative Examples, but the present invention is not limited to the following Examples.

[Example 1] 1.47 g of tetraethylammonium hydroxide, 0.8 g of polyvinyl alcohol having an average degree of polymerization of 1000 and a saponification degree of 88%, and 100 g of pure water were mixed to prepare a light reflection preventing material (Sample 1). ) Was made.

Dispense Sample 1 onto a 6 inch wafer, first at 300 rpm for 3 seconds, then 30
The wafer was rotated at 00 rpm for 20 seconds to form an antireflection film, and the film thickness and refractive index were measured by ellipsometry.
The results are shown in Table 1.

On the other hand, a photoresist material (THMRiP1800 manufactured by Tokyo Ohka Kogyo Co., Ltd., prebaked at a temperature of 90)
Sample 1 was dispensed on a 6-inch wafer having a different film thickness (° C., time 90 seconds), and the wafer was rotated at 300 rpm for 3 seconds and then at 3000 rpm for 20 seconds to form an antireflection film.

With an i-line stepper, one shot 4 mm square area was subjected to stepping exposure by changing the exposure amount and rinsed with pure water to remove the antireflection film. After that, the temperature 110 ℃,
Post exposure bake was performed for 90 seconds, and the temperature was adjusted to 23 using developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.).
Static paddle development was carried out at a temperature of 65 seconds for a pure water rinse.

The exposure amount at which the film is completely removed is Eth
Then, the magnitude of the optical interference effect in the photoresist film was obtained from the magnitude of the variation of Eth with respect to the variation of the photoresist film thickness.

Example 2 1.50 g of tetra-n-propylammonium hydroxide and an average degree of polymerization of 1
Polyvinyl alcohol with a saponification degree of 88% at 000 0.8
g was mixed with 100 g of pure water to prepare a light reflection preventing material (Sample 2).

Sample 2 was dispensed onto a 6 inch wafer, first at 300 rpm for 3 seconds and then 30 seconds.
The wafer was rotated at 00 rpm for 20 seconds to form an antireflection film, and the film thickness and refractive index were measured by ellipsometry.
The results are shown in Table 1.

On the other hand, a photoresist material (THMRiP1800 manufactured by Tokyo Ohka Kogyo Co., Ltd., prebaked at a temperature of 90)
Sample 2 was dispensed onto a 6-inch wafer having a different film thickness (° C., time 90 seconds), and the wafer was rotated at 300 rpm for 3 seconds and then at 3000 rpm for 20 seconds to form an antireflection film.

An i-line stepper was used to perform stepping exposure on an area of 4 mm square for one shot by changing the exposure amount, and rinse with pure water to peel off the antireflection film. After that, the temperature 110 ℃,
Post exposure bake was performed for 90 seconds, and the temperature was adjusted to 23 using developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.).
Static paddle development was carried out at a temperature of 65 seconds for a pure water rinse.

The exposure amount at which the film is completely removed is Eth
Then, the magnitude of the optical interference effect in the photoresist film was obtained from the magnitude of the variation of Eth with respect to the variation of the photoresist film thickness.

Example 3 1.60 g of tetra-n-butylammonium hydroxide and an average degree of polymerization of 10
0.8g polyvinyl alcohol with saponification degree of 88% at 00
And 100 g of pure water were mixed to prepare a light reflection preventing material (Sample 3).

Dispense Sample 3 onto a 6 inch wafer, first at 300 rpm for 3 seconds, then 30
The wafer was rotated at 00 rpm for 20 seconds to form an antireflection film, and the film thickness and refractive index were measured by ellipsometry.
The results are shown in Table 1.

On the other hand, a photoresist material (THMRiP1800 manufactured by Tokyo Ohka Kogyo Co., Ltd., prebaked at a temperature of 90)
Sample 3 was dispensed onto a 6-inch wafer having a different film thickness (° C., time 90 seconds), and the wafer was rotated first at 300 rpm for 3 seconds and then at 3000 rpm for 20 seconds to form an antireflection film.

With an i-line stepper, one shot of 4 mm square area was subjected to stepping exposure by changing the exposure amount and rinsed with pure water to remove the antireflection film. After that, the temperature 110 ℃,
Post exposure bake was performed for 90 seconds, and the temperature was adjusted to 23 using developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.).
Static paddle development was carried out at a temperature of 65 seconds for a pure water rinse.

The exposure amount at which the film is completely removed is Eth
Then, the magnitude of the optical interference effect in the photoresist film was obtained from the magnitude of the variation of Eth with respect to the variation of the photoresist film thickness.

Example 4 1.50 g of tetramethylammonium acetate, 0.8 g of polyvinyl alcohol having an average degree of polymerization of 1000 and a saponification degree of 88%, and 100 parts of pure water.
g was mixed to prepare a light antireflection material (Sample 4).

Dispense Sample 4 onto a 6 inch wafer, first at 300 rpm for 3 seconds, then 30
The wafer was rotated at 00 rpm for 20 seconds to form an antireflection film, and the film thickness and refractive index were measured by ellipsometry.
The results are shown in Table 1.

On the other hand, a photoresist material (THMRiP1800 manufactured by Tokyo Ohka Kogyo Co., Ltd., prebaked at a temperature of 90)
Sample 4 was dispensed on a 6-inch wafer having a different film thickness (° C., time 90 seconds), and the wafer was rotated at 300 rpm for 3 seconds and then at 3000 rpm for 20 seconds to form an antireflection film.

With an i-line stepper, one shot 4 mm square area was subjected to stepping exposure by changing the exposure amount and rinsed with pure water to remove the antireflection film. After that, the temperature 110 ℃,
Post exposure bake was performed for 90 seconds, and the temperature was adjusted to 23 using developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.).
Static paddle development was carried out at a temperature of 65 seconds for a pure water rinse.

The exposure amount at which the film is completely removed is Eth
Then, the magnitude of the optical interference effect in the photoresist film was obtained from the magnitude of the variation of Eth with respect to the variation of the photoresist film thickness.

Example 5 1.50 g of tetramethylammonium carbonate, 0.8 g of polyvinyl alcohol having an average degree of polymerization of 1000 and a saponification degree of 88%, and pure water 10
0 g was mixed to prepare a light antireflection material (Sample 5).

Sample 5 was dispensed onto a 6 inch wafer, first at 300 rpm for 3 seconds and then at 30 rpm.
The wafer was rotated at 00 rpm for 20 seconds to form an antireflection film, and the film thickness and refractive index were measured by ellipsometry.
The results are shown in Table 1.

On the other hand, a photoresist material (THMRiP1800 manufactured by Tokyo Ohka Kogyo Co., Ltd., prebaked at a temperature of 90)
Sample 5 was dispensed onto a 6-inch wafer having a different film thickness (° C., time 90 seconds), and the wafer was rotated first at 300 rpm for 3 seconds and then at 3000 rpm for 20 seconds to form an antireflection film.

With an i-line stepper, one shot of 4 mm square area was stepwise exposed by changing the exposure amount and rinsed with pure water to remove the antireflection film. After that, the temperature 110 ℃,
Post exposure bake was performed for 90 seconds, and the temperature was adjusted to 23 using developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.).
Static paddle development was carried out at a temperature of 65 seconds for a pure water rinse.

The exposure amount at which the film is completely removed is Eth
Then, the magnitude of the optical interference effect in the photoresist film was obtained from the magnitude of the variation of Eth with respect to the variation of the photoresist film thickness.

[0053]

[Table 1]

[Comparative Example 1] A 6-inch wafer having different film thickness of photoresist material (THMRiP1800 manufactured by Tokyo Ohka Kogyo Co., Ltd., prebaking temperature: 90 ° C., time: 90 seconds) was shot with an i-line stepper for 4 mm per shot. Stepping exposure is performed on the square area by changing the exposure amount, and then the temperature is set to 1
Post-exposure bake is performed at 10 ° C. for 90 seconds, and static paddle development is performed at a temperature of 23 ° C. for 65 seconds using developer NMD-W (manufactured by Tokyo Ohka Kogyo Co., Ltd.), and rinsed with pure water. It was

The exposure amount at which the film is completely removed is Eth
Then, the magnitude of the optical interference effect in the photoresist film was obtained from the magnitude of the variation of Eth with respect to the variation of the photoresist film thickness.

In the above Examples 1 to 5 and Comparative Example 1,
FIG. 4 shows the result of the magnitude of the fluctuation of Eth with respect to the fluctuation of the photoresist film thickness. In the figure, the dotted line is the result of Examples 1 to 5, and the solid line is the result of Comparative Example 1.

[Brief description of drawings]

FIG. 1 is a schematic view of a lithography process.

FIG. 2 is a schematic view showing light scattering when only a resist layer is formed on a substrate.

FIG. 3 is a schematic view showing light scattering when a light antireflection film of the present invention is formed on a resist layer formed on a substrate.

FIG. 4 is a graph showing the magnitude of fluctuation of Eth with respect to fluctuation of photoresist film thickness in patterns formed using the antireflection films obtained in Examples 1 to 5 and Comparative Example 1.

[Explanation of symbols]

 1 substrate 2 photoresist layer 3 light antireflection layer 4 ultraviolet rays 5 resist pattern

Claims (2)

[Claims] 1. A light antireflection material containing a quaternary ammonium compound represented by the following general formula (I). R ¹ ₄ N ⁺ -R ² (I) [wherein R ¹ is the same or different alkyl group having 1 to 6 carbon atoms, alkoxy group having 1 to 6 carbon atoms or hydroxyalkyl group having 1 to 6 carbon atoms] , R ² is a hydroxyl group, a mono- or dicarboxyl group having 1 to 6 carbon atoms, a fluoro group, a hydrogenated difluoro group, a chloro group, a bromo group, a sulfonyl group,
Represents a sulfonyl hydride group or a methylcarbonyl group. ] 2. The upper layer of a photoresist layer as claimed in claim 1.
A pattern forming method comprising: forming a light reflection preventing film made of the light reflection preventing material described above; and exposing the photoresist layer, and then removing the light reflection preventing film.