JPH1032162A - Antireflection film for resist use and method of forming resist pattern using this - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce irregularities in the line width of an antireflection film for resist use and the like in a microscopic processing using a photolithography technique and to enhance the processing accuracy of the film by a method, wherein the antireflection film is constituted of an amorphous carbon film having a specified hydrogen concentration. SOLUTION: A polycrystalline silicon film 14a and a tungsten silicide film 14b are formed on a silicon oxide film 12 and a gate oxide film 13. Then, a silicon oxide film 15 is formed on the film 14b and an amorphous carbon film 16, which is used as an antireflection film, is formed on the film 15 by an ECR plasma CVD method. Then, an N-type resist film 17 is formed on the film 16. When this film 16 is formed by the ECR plasma CVD method, a substrate bias voltage is changed, whereby a hydrogen concentration in the film 16 is controlled. That is, by setting the substrate bias voltage in about -50V or lower, the film 16 having 25% or lower in hydrogen concentration is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for selectively exposing and patterning a resist film by photolithography.
The present invention relates to a resist antireflection film used as a base layer of a resist film and a method of forming a resist pattern using the same.

[0002]

2. Description of the Related Art In order to improve the degree of integration in an LSI (Large Scale Integrated Circuit), it is necessary to miniaturize components and wiring of a semiconductor element. In order to achieve such miniaturization, it is necessary to improve the processing line width and processing accuracy in photolithography and to increase the resolution. In order to improve such resolution, it is necessary to shorten the wavelength of light for exposing the resist film. For example, it has been studied to shorten the wavelength of irradiation light from g-line to i-line (365 nm) of ultraviolet light. I have. Further, KrF excimer laser light (248n
m), the use of ArF excimer laser light (193 nm) as irradiation light is being studied.

A gate electrode of a thin film transistor is patterned by such a photolithography method. The gate electrode is formed of a silicon semiconductor, a refractory metal silicide such as tungsten silicide, a refractory metal such as tungsten, or the like. Often done. Since these materials have high reflectance in the ultraviolet region, when exposure is performed using ultraviolet light, ultraviolet light is reflected on the surface of the thin film serving as a gate electrode, and the resist film is also exposed to the reflected light. For this reason, there has been a problem that a large variation occurs in the processing line width and the processing accuracy is reduced.

FIG. 9 is a cross-sectional view for explaining the exposure of a resist film by such reflected light. A silicon oxide film 2 for element isolation is formed on a substrate 1.
A gate oxide film 3 is formed between the silicon oxide films 2. On the silicon oxide film 2 and the gate oxide film 3,
A gate electrode layer 4 having a laminated structure of a polycrystalline silicon film and a tungsten silicide film is formed. On this gate electrode layer 4, a resist film 5 is provided.

[0005] A patterning mask 6 is provided above the resist film 5, and a hole 6 a of the patterning mask 6 is provided.
Then, ultraviolet light such as i-ray is irradiated, and the resist film 5 is selectively exposed. At this time, as described above, the gate electrode layer 4 reflects ultraviolet light and the like with a high reflectance,
Ultraviolet light is reflected on the surface of the gate electrode layer 4, and the region 5a to which the ultraviolet light should not be irradiated is also irradiated with the ultraviolet light. As a result, the gate line width becomes narrow or the line width varies.

As a method for solving such a problem, a method has been proposed in which an antireflection film is provided on the gate electrode layer to prevent reflection during exposure. JP-A-6-342744 and JP-A-6-342744 disclose such an antireflection film.
No. 69123 proposes to use an amorphous carbon film.

[0007]

In the above publication,
Although the amorphous carbon film is formed by a sputtering method, the amorphous carbon film formed by these methods is:
Although having an antireflection effect, it was still insufficient. The use of an amorphous carbon film as a resist anti-reflection film has been studied, but it was not known in detail what kind of amorphous carbon film is suitable as a resist reflection film. .

SUMMARY OF THE INVENTION It is an object of the present invention to provide a resist reflection film made of an amorphous carbon film which can significantly reduce the line width variation and the like and improve the processing accuracy in fine processing with a line width of 0.35 μm or less by photolithography. An object of the present invention is to provide a method of forming a resist pattern and a resist pattern using the same.

[0009]

The resist anti-reflection film of the present invention is characterized in that it is made of amorphous carbon having a hydrogen concentration of 25% or less. In the present invention, the hydrogen concentration is preferably 23% or less, more preferably 21% or less. By setting the hydrogen concentration in such a range, it is possible to remarkably reduce variations in line width and the like in forming a resist pattern and increase processing accuracy.

In the present invention,% of the hydrogen concentration is represented by atomic%.
, For example, secondary ion mass spectrometry (SIMS)
Can be measured. In the present invention, when exposure is performed using i-line, the thickness of the amorphous carbon film is 5
It is preferable that it is in the range of 0 to 75 nm. By setting the thickness within such a range, a resist pattern with higher processing accuracy can be formed.

The method of forming a resist pattern according to the present invention is a method of forming a resist pattern by exposing a partial region of a resist film provided above a thin film in order to pattern the thin film provided above the substrate. The method includes the steps of forming the resist reflective film of the present invention on a thin film, forming a resist film on the resist reflective film, and exposing a partial region of the resist film.

The amorphous carbon film serving as the resist anti-reflection film can be formed by, for example, a plasma CVD method. A high frequency voltage is applied to the substrate or the substrate holder so that a negative self-bias voltage is generated on the substrate. By forming the film while forming the film, an amorphous carbon film having the above hydrogen concentration range can be formed. As the plasma CVD method,
In particular, the ECR plasma CVD method is preferable. The self-bias voltage is preferably about -50 V or less,
More preferably, the voltage is about -80 V or less. Generally, an amorphous carbon film having a lower hydrogen concentration can be formed as the self-bias generated on the substrate is lower.

In the present invention, the hydrogen concentration of the amorphous carbon film may be a hydrogen concentration within a predetermined range in the film thickness direction. For example, the hydrogen concentration distribution may change in the film thickness direction. . Therefore, a gradient structure of the hydrogen concentration may exist in the film thickness direction. In such a case, it is preferable that the hydrogen concentration be lower on the resist film side than on the substrate side, because the lower the hydrogen concentration is, the higher the antireflection effect is.

The resist anti-reflection film of the present invention prevents reflection of short-wavelength light such as i-line, and has a line width of, for example, 0.35 μm.
It is possible to remarkably reduce variations in line width and thinning of line width in fine processing of m or less, and to remarkably increase processing accuracy in photolithography technology.

[0015]

2 to 4 are cross-sectional views for explaining an embodiment according to a method for forming a resist pattern according to the present invention, and show a pattern forming method for patterning a gate electrode of a MOSFET. As shown in FIG. 2A, a silicon oxide film 12 for element isolation is formed on a silicon substrate 11. The silicon oxide film 12
It is formed only in a specific region by the selective oxidation method, and is formed to have a thickness of 400 nm.

Next, a gate oxide film 13 is formed in an active region where a transistor is to be formed. The gate oxide film 13 is formed to a thickness of 7 nm by a dry oxidation method at 800 ° C. On the silicon oxide film 2 and the gate oxide film 3, a 100-nm-thick polycrystalline silicon film 14a and a 100-nm-thick tungsten silicide film 14b are formed by low-pressure CVD. The polycrystalline silicon film 14a and the tungsten silicide film 14
A gate electrode layer is formed from the composite film of b.

Next, a silicon oxide film 15 is formed on the tungsten silicide film 14b to a thickness of 150 nm by a low pressure CVD method. This silicon oxide film 1
Reference numeral 5 serves as a patterning mask when the underlying gate electrode layer is processed by dry etching.

Next, an amorphous carbon film 16 serving as an antireflection film is formed on the silicon oxide film 15. In the present embodiment, the amorphous carbon film 16 is formed by an ECR to be described later.
It is formed by a plasma CVD method. In the formation by the ECR plasma CVD method, the self-bias generated on the substrate is changed in a range of 0 V to -150 V, and the film thickness is changed in a range of 0 nm to 100 nm.

Next, a negative resist film 17 is applied on the amorphous carbon film 16 so as to have a thickness of 1000 nm, and a resist film 17 is formed. Next, as shown in FIG. 2B, a mask 18 is disposed above the resist film 17 and the resist film 17 is exposed by irradiating the resist film 17 with an i-line exposure device. The i-line is selectively irradiated to the resist film 17 through the holes 18a of the mask 18. As a result, a non-exposed area 17a of the resist film 17 and other exposed areas are formed.

Next, as shown in FIG. 3C, the resist film in other regions is removed so as to leave only the non-exposed regions 17a of the resist film. Next, the non-exposed area 1 of the resist film
Using the mask 7a as a mask, the amorphous carbon film 16, the silicon oxide film 15, the polycrystalline silicon film 14a as the gate electrode layer, and the tungsten silicide film 14b are sequentially etched by dry etching. Thereby, as shown in FIG. 3D, the non-exposed area 17a of the resist film is formed.
Are removed from the area other than the area corresponding to. Thus, a gate electrode layer 14c, a silicon oxide film 15a, an amorphous carbon film 16a, and a resist film 17 are formed on the gate oxide film 13.
a is patterned. Next, by exposing to an oxygen plasma atmosphere, the resist film 17a and the amorphous carbon film 16a are removed, and as shown in FIG. 4E, a state is formed in which the gate electrode 14c is formed on the channel region. .

FIG. 5 is a schematic sectional view showing an example of an ECR plasma CVD apparatus used for forming an amorphous carbon film in the above embodiment. Hereinafter, this ECR plasma apparatus will be described.

Referring to FIG. 5, inside a vacuum chamber 108, a plasma generation chamber 104 and a reaction chamber in which a substrate 113 is installed are provided. One end of a waveguide 102 is attached to the plasma generation chamber 104, and a microwave supply unit 101 is provided at the other end of the waveguide 102. Microwaves generated by the microwave supply means 101 are guided to the plasma generation chamber 104 through the waveguide 102 and the microwave introduction window 103. In the plasma generation chamber 104, argon (A
r) A discharge gas introduction pipe 105 for introducing a discharge gas such as a gas is provided. In addition, the plasma generation chamber 10
4, a plasma magnetic field generator 106 for guiding plasma to the reaction chamber is provided.

In the reaction chamber in the vacuum chamber 108, a drum-shaped substrate holder 112 is installed so as to be rotatable around a rotation axis perpendicular to the paper surface of FIG. , A motor not shown is connected. On the outer peripheral surface of the substrate holder 112, a plurality of (in this embodiment, 24) substrates 113 are mounted at equal intervals. The substrate holder 112 has a high-frequency power source 1
10 are connected.

A metallic cylindrical shield cover 114 is provided around the substrate holder 112 at a distance of about 5 mm from the substrate holder 112. This shield cover 114 is connected to a ground electrode. When a film is formed, the shield cover 114 is connected to the substrate holder 112 and the vacuum chamber 10 other than where the film is formed by a high frequency (RF) voltage applied to the substrate holder 112.
8 is provided to prevent the occurrence of a discharge between them.

The shield cover 114 has an opening 115
Are formed. The plasma drawn from the plasma generation chamber 104 passes through the opening 115 and is emitted to the substrate 113 mounted on the substrate holder 112. In the vacuum chamber 108, a reaction gas introduction pipe 116 is provided. This reaction gas introduction pipe 116
Is located above the opening 115.

FIG. 6 is a plan view showing the vicinity of the tip of the reaction gas introduction pipe 116. Referring to FIG. 6, a reaction gas introduction pipe 116 has a gas introduction part 116a for introducing CH ₄ gas from the outside into the vacuum chamber, and a gas introduction part 1
Outgassing portion 116b connected vertically to 16a
It is composed of The gas discharge portion 116b is disposed perpendicular to the rotation direction A of the substrate holder 112, and is provided so as to be located upstream of the opening 115 in the rotation direction. In the gas discharge part 116b,
A plurality of holes 117 are formed in a direction of about 45 degrees downward. In this embodiment, eight holes 117 are formed. The interval between the holes 117 is formed so as to gradually decrease from the center toward both sides. By forming the holes 117 at such intervals, the gas introduction portions 116a
CH ₄ gas introduced from the holes 117 is almost uniformly released from the holes 117, respectively.

Using the above-described ECR plasma CVD apparatus, an amorphous carbon film 16 shown in FIG. 2 is formed as follows. First, the inside of the vacuum chamber 108 is 10 ⁻⁵ to 1.
After exhausting to 0 ^-7 Torr, the substrate holder 112 is
Rotate at a speed of rpm. Next, the discharge gas introduction pipe 10
5 to supply Ar gas at 5.7 × 10 ⁻⁴ Torr, and from the microwave supply means 101 to 2.45 GH.
A microwave of z, 100 W is supplied to radiate the Ar plasma formed in the plasma generation chamber 104 to the surface of the substrate 113. At the same time, CH
While supplying ₄ gases at 1.3 × 10 ⁻³ Torr, RF power of 13.56 MHz is applied to the substrate holder 112 from the high frequency power supply 110.

The RF power applied to the substrate holder 112 is changed so that the self-bias voltage (substrate bias voltage) generated on the substrate becomes -50 V, -100 V, and -150 V to form an amorphous carbon film. For comparison, an amorphous carbon film is formed without applying RF power to the substrate holder 112, that is, so that the substrate bias voltage becomes 0V. The thickness of the amorphous carbon film is 60
nm.

FIG. 7 is a diagram showing the hydrogen concentration in the amorphous carbon film when the substrate bias voltage is formed at 0 V, -50 V, -100 V, and -150 V as described above. Here, the hydrogen concentration is measured by SIMS. As shown in FIG. 7, when the substrate bias is 0 V, the hydrogen concentration in the film is 30%. Assuming that the substrate bias voltage is −50 V, −100 V, and −150 V, the hydrogen concentrations in the film are 23%, 20%, and 15%, respectively. Therefore, in the ECR plasma CVD apparatus, the hydrogen concentration in the amorphous carbon film can be controlled by changing the substrate bias voltage. It can be seen that under the conditions of this embodiment, an amorphous carbon film having a hydrogen concentration of 25% or less can be formed by setting the substrate bias voltage to about -50 V or less.

FIG. 8 shows a substrate bias voltage of -50 V, -1.
FIG. 4 is a diagram showing variations in gate line width (gate length) when the amorphous carbon film is formed by changing the thickness of the amorphous carbon film from 0 to 100 nm under the respective conditions of 00V and -150V. That is, the variation in the width α of the gate electrode 14c shown in FIG. The gate line width is 0.3
It is 5 μm. As is apparent from FIG. 8, the lower the substrate bias voltage, the smaller the variation in gate line width. The smallest variation occurs when the thickness of the amorphous carbon film is 60 nm. Therefore, it can be seen that the variation is relatively small in the range of the thickness of the amorphous carbon film of 50 to 75 nm. When a resist film is provided directly on the gate electrode layer without using the anti-reflection film, the variation of the gate line width is 0.10 μm with respect to the gate line width of 0.35 μm. Therefore, the variation of the gate line width is 28.5%.

FIG. 1 is a diagram showing the relationship between the hydrogen concentration in the amorphous carbon film and the variation in gate line width. In addition,
Here, the thickness of the amorphous carbon film is 60 nm. As is clear from FIG. 1, the variation in the gate line width decreases as the hydrogen concentration decreases, and the variation in the gate line width sharply decreases when the hydrogen concentration becomes 25% or less. Therefore, by setting the hydrogen concentration to 25% or less, an amorphous carbon film having an excellent antireflection effect can be obtained.

As described above, the substrate bias voltage is set to -5.
I-line (wavelength 365 n) of an amorphous carbon film (60 nm thick) formed by changing the voltage to 0 V, -100 V, and -150 V
Table 1 shows the real part (refractive index) n and the imaginary part (extinction coefficient) k of the complex refractive index with respect to m).

[0033]

[Table 1]

From the refractive index n and the extinction coefficient k shown in Table 1, it can be seen that the amorphous carbon film of this embodiment exhibits an excellent antireflection effect on i-line. In the above embodiment, the resist pattern is formed by exposing using an i-ray having a wavelength of 365 nm.
The light absorption effect can be obtained even in a short wavelength region of 365 nm or less. Therefore, the wavelength is 248 nm.
KrF excimer laser, ArF with wavelength of 193 nm
Even when a resist pattern is formed using an excimer laser, variations in line width and the like can be reduced, as in the above-described embodiment.

Further, in the above embodiment, an example was shown in which the gate electrode was formed of a laminated film of a tungsten silicide film and a polycrystalline silicon film. However, the present invention is not limited to this. The same effect can be obtained when a single layer of a polycrystalline silicon film is used or when another electrode material such as tungsten and titanium silicide is used.

Further, in the above embodiment, an example was described in which the silicon oxide film was formed between the gate electrode layer and the antireflection film. However, the present invention is not limited to this, and the present invention is not limited to this. The present invention can be applied to a case where a silicon oxide film is not formed between the prevention films, and the same effect can be obtained.

[0037]

By using the resist antireflection film of the present invention, for example, i-line, KrF excimer laser, A
In fine processing with a line width of 0.35 μm or less using light of a short wavelength such as an rF excimer laser, variations in line width and the like can be significantly reduced, and a resist pattern with high processing accuracy can be formed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relationship between a hydrogen concentration in an amorphous carbon film and variations in gate line width.

FIG. 2 is a cross-sectional view showing a step of forming a resist pattern and patterning a gate electrode by using the resist reflection film of the embodiment according to the present invention.

FIG. 3 is a cross-sectional view showing a step of forming a resist pattern and patterning a gate electrode using the reflective film for resist of the embodiment according to the present invention.

FIG. 4 is a cross-sectional view showing a step of forming a resist pattern and patterning a gate electrode by using the resist reflection film of the embodiment according to the present invention.

FIG. 5 is a schematic configuration diagram showing an ECR plasma CVD apparatus.

6 is a plan view showing the vicinity of an opening of the ECR plasma CVD apparatus shown in FIG.

FIG. 7 is a diagram showing a relationship between a self-bias voltage (substrate bias voltage) generated on a substrate and a hydrogen concentration in an amorphous carbon film.

FIG. 8 is a diagram showing the relationship between the thickness of the amorphous carbon film, the substrate bias voltage, and the variation in the gate line width.

FIG. 9 is a cross-sectional view for explaining an abnormal pattern shape due to reflected light when forming a resist pattern.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 ... Substrate 12 ... Silicon oxide film 13 ... Gate oxide film 14a ... Polycrystalline silicon film 14b ... Tungsten silicide film 14c ... Gate electrode 15 ... Silicon oxide film 16 ... Amorphous carbon film (anti-reflection film) 17 ... Resist film 18 …mask

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Makoto Akizuki 2-5-5 Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Keiichi Ueda 2-5-1 Keihanhondori, Moriguchi-shi, Osaka No. 5 Sanyo Electric Co., Ltd.

Claims (7)

[Claims] 1. An anti-reflection film for a resist, comprising an amorphous carbon film having a hydrogen concentration of 25% or less. 2. The film thickness of the amorphous carbon film is 50-7.
2. The anti-reflection film for a resist according to claim 1, wherein the thickness is within a range of 5 nm. 3. The anti-reflection film for resist according to claim 1, wherein the anti-reflection film for resist is an anti-reflection film used when patterning a resist using i-line. 4. A method for forming a resist pattern by exposing a partial region of a resist film provided above a thin film for patterning the thin film provided above the substrate, wherein the resist pattern is formed on the thin film. Forming a resist anti-reflection film according to any one of claims 1 to 3, forming the resist film on the resist anti-reflection film, exposing a partial region of the resist film; Forming a resist pattern. 5. The resist according to claim 4, wherein the amorphous carbon film serving as the resist anti-reflection film is formed by applying a high frequency voltage to the substrate by a plasma CVD method so as to generate a negative self-bias voltage. Pattern formation method. 6. The method according to claim 5, wherein the plasma CVD method is an ECR plasma CVD method. 7. The method according to claim 5, wherein the self-bias voltage is about −50 V or less.