JPH07307277A - Forming method of antireflection film and forming method of fine pattern - Google Patents

Abstract

PURPOSE:To prevent contamination by carbon, etc., and to provide not only an antireflection film having an excellent antireflection effect and manufacture thereof but also a dry etching method (that is, the forming method of a fine patter) fitted to the antireflection film. CONSTITUTION:A heat-resistant ceramic film such as a sialon film is used as an antireflection film 103 in a method, in which the antireflection film 103 employed when a photosensitive film 104 applied onto a substrate 101 is exposed is formed. The antireflection film 103 can be formed by at least using a gas containing silicon and a gas containing nitrogen. The optical constant of the antireflection film 103 can be changed by altering the partial pressure rate of the gas containing silicon and the gas containing nitrogen at that time. The antireflection film can be shaped through a plasma CVD method such as a magnetic-field mu-wave plasma CVD method.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a semiconductor integrated circuit, and more particularly to a method for forming an antireflection film and a method for forming a fine pattern used in the lithography process.

[0002]

2. Description of the Related Art Wiring technologies are becoming more and more miniaturized and multi-layered in accordance with higher density of devices.
However, high integration may be a factor that reduces the reliability of the device. This is because the progress of miniaturization and multilayering of the wiring makes the step of the interlayer insulating film large and steep, and the processing accuracy of the wiring formed on the step becomes large.
This is to reduce reliability. Therefore, in order to improve the resolution while extending the life using the current lithography technology, first, it is necessary to improve the flatness of the interlayer insulating film. This is becoming important from the viewpoint of a decrease in the depth of focus due to the shortening of the wavelength of lithography.

Another important problem is how to suppress the reflection from the base to maintain the resolution of the resist. Therefore, a technique of forming a so-called antireflection film under the resist is becoming mainstream. One of the candidates for this antireflection film is an amorphous carbon film containing hydrogen (aC: H film). This aC: H film is described, for example, in the proceedings of the 40th Joint Lecture on Applied Physics, page 559. This film can be easily formed by a conventional plasma CVD method and is attracting attention as an effective antireflection film.

[0004]

However, since this antireflection film contains carbon, when it is used in an actual manufacturing process, there is a fear of contamination by the carbon.
In addition, since it is a film of a single composition (Hydrogen is included,
This is not intentionally added), and there is a problem that the optical constant cannot be controlled in a wide range.

Further, this type of antireflection film cannot be dissolved in a solvent and must be subjected to a predetermined patterning by etching. At that time, wet etching which may lower the resolution can be used. Instead, a vigorous dry etching method is used. Since the above antireflection film is a compound mainly composed of carbon, oxygen may be used as an etching gas, but there is a problem that the resist is also etched.

Therefore, an antireflection film which does not have the above-mentioned carbon contamination and which can control a wide range of optical constants, a manufacturing method thereof, and an appropriate etching method (that is, a fine pattern forming method) suitable for the film. ) Was required.

The present invention has been made in view of the above circumstances, and an antireflection film which has a good antireflection effect by eliminating contamination by carbon and the like, a manufacturing method thereof, and a dry film suitable for the antireflection film. An object is to provide an etching method (that is, a method for forming a fine pattern).

[0008]

Means for Solving the Problems As a result of earnest studies on a good antireflection film suitable for forming a fine pattern, the present inventor has already filed a patent application in order to eliminate carbon contamination. As proposed in Japanese Unexamined Patent Publication No. 4-359750, it has come to be considered that an antireflection film which mainly contains silicon and contains nitrogen so that its optical constant can be widely controlled is preferable.

As a result of further consideration of this point, the present inventor found that the sialon film (SIALON film) already proposed by the present inventor in Japanese Patent Application Nos. 5-088488 and 5-131591. I came to think that it should be used. The sialon film is composed of silicon, aluminum, oxygen and nitrogen.
It is an oxynitride-based ceramic consisting of elements and has excellent mechanical strength, oxidation resistance, corrosion resistance, and insulation properties.
It is an inorganic compound that is expected to have various uses as an engineering ceramic in recent years. A liquid phase epitaxy method has been generally used as a method for forming a sialon film, but for example, the 39th Japan Society of Applied Physics Association Lecture Meeting (1992).
Spring Annual Meeting) Preliminary Lecture Collection, page 440, abstract number 30p-
ZW-6 with microwave plasma CVD (ECR-CV
As the film formation by the method D) is reported, the vapor phase growth method has also been tried. As a result, the reproducibility, uniformity, film quality, etc. of film formation are greatly improved.

Further, the present inventor has previously proposed by the present applicant as an optimum method for anisotropically processing these antireflection films without using so-called CFCs (Japanese Patent Laid-Open No. 4-084).
427) Dry etching with a gas containing a large amount of sulfur in the molecule (hereinafter referred to as “sulfur process”)
I came up with the idea of using.

That is, a method of forming an antireflection film according to the present invention is a method of forming an antireflection film used when exposing a photosensitive film coated on a substrate, wherein heat resistant ceramics is used as the antireflection film. It is characterized by using.
The antireflection film may be composed of a compound ceramic containing at least silicon. Further, the antireflection film can be formed using at least a gas containing silicon and a gas containing nitrogen. In this case, the optical constant of the antireflection film can be changed by changing the partial pressure ratio between the gas containing silicon and the gas containing nitrogen.

The antireflection film may be made of sialon. The antireflection film containing sialon is preferably formed by a plasma CVD method such as a magnetic field microwave plasma CVD method. A method of forming a fine pattern according to the present invention comprises a step of forming an antireflection film on an object to be formed with a fine pattern, a step of forming a photosensitive film on the antireflection film, And exposing the photosensitive film to a predetermined pattern, and etching the antireflection film using the photosensitive film as a mask.

The etching is preferably dry etching using low temperature plasma of a gas containing at least sulfur. As the gas containing sulfur, S ₂ F ₂ , S
F ₂ , SF ₄ , S ₂ F ₁₀ , S ₃ Cl ₂ , SCl ₂ , S ₂ Br ₂ ,
It is preferable to use at least one gas selected from SBr ₂ and S ₃ Br ₂ .

As the gas containing sulfur, S ₂ F ₂ , SF
₂ , SF ₄ , S ₂ F ₁₀ , S ₃ Cl ₂ , SCl ₂ , S ₂ Br ₂ , SB
It is also possible to use a gas in which at least one first gas selected from r ₂ and S ₃ Br ₂ and at least one _second gas selected from H ₂ , H ₂ S and a silane compound are mixed.

As the gas containing sulfur, S ₂ F ₂ , SF
₂ , SF ₄ , S ₂ F ₁₀ , S ₃ Cl ₂ , SCl ₂ , S ₂ Br ₂ , SB
A gas in which a gas containing nitrogen is mixed with at least one kind of first gas selected from r ₂ and S ₃ Br ₂ may be used. The etching is preferably dry etching performed at a temperature equal to or lower than the temperature at which sulfur and its compound sublime. The etching at that time is preferably 0 ° C. or higher, but may be 0 ° C. or lower.

[0016] It is preferable that the etching is performed so as to continuously etch the underlying object to be processed, following the etching process of the antireflection film.

[0017]

The sialon film is known as heat-resistant ceramics, and as described in the invention already proposed by the present inventor, if a gas plasma CVD apparatus containing at least Al, Si, O, N is used. , Can be easily formed.
Since the gas composition does not contain carbon, it is possible to avoid the above-mentioned problem of contamination by carbon. In addition, by changing the partial pressure ratio of the gas containing silicon and the gas containing nitrogen in the gas composition, the above-mentioned Japanese Patent Application No. 4-3597.
As described in 50, the optical constant of the sialon film can be easily controlled. In addition, this sialon is known as an engineering ceramics that is rich in mechanical strength, and after being used as an antireflection film on an Al film, it can be used as a life-prolonging layer of the Al film, and the purpose is to prevent reflection. The step of removing the film can be omitted. Further, since it has heat resistance even if it is not removed and remains, there is no problem even if there is a thermal process in a later step.

As a method of etching the antireflection film without using CFC, the sulfur process described above is used, whereby the gas containing sulfur is easily dissociated in the low temperature plasma to form a halogen radical as an etchant. , And produce sulfur as a deposit. Of course, the halogen radical contributes to the etching of the sialon antireflection film, and the sulfur as a deposit is deposited on the side wall of the object to be etched, which contributes to anisotropic processing.

Furthermore, by adding a hydrogen compound that complements the halogen radicals, a system with a strong deposition can be obtained, and anisotropy can be suitably achieved even in a system in which so-called side etching is remarkable. it can. Further, by adding a gas containing nitrogen to the above-mentioned gas containing sulfur, polythiazyl (SN) having a stronger deposition property can be obtained.
_{Since x} can be formed and deposited as a sidewall, anisotropy can be suitably achieved even in a system in which so-called side etching is remarkable.

Moreover, the deposit of sulfur or the deposit of sulfur compound formed by these gases is about 1 in the former case.
In the latter case, the latter can be sublimated without any trace by simply heating it to about 180 ° C. Therefore,
The deposits can be removed by a simple method called heating without using CFC gas, and particles will not be a problem.

Of the components of the sialon film, aluminum and silicon have a slightly higher vapor pressure of the halogen compound, but are easily etched by etching at a temperature of 0 ° C. or higher and lower than the sublimation temperature of the sulfur film. Is possible. Furthermore, since the halogen radicals that are dissociated from the gas containing sulfur serve as etchants for the components of aluminum and the polycide film, it is possible to easily etch these films subsequent to the etching of the antireflection film.

[0022]

EXAMPLES Specific examples of the present invention will be described below. The present invention is not limited to the following examples and can be variously modified within the scope of the present invention. Example 1 Hereinafter, a method for forming an antireflection film according to an example of the present invention will be described.

Prior to the description of the actual antireflection film forming process and etching process, the magnetic field microwave plasma apparatus used to carry out the present invention will be described with reference to FIG. FIG. 1 shows a magnetic field microwave plasma CVD apparatus used for carrying out the present invention. This device will be briefly described. The microwave 2 generated by the magnetron 1 is transferred to a reaction chamber 5 surrounded by a quartz bell jar 4 through a waveguide 3 and installed so as to surround the reaction chamber 5. The solenoid coil 6 generates a microwave frequency (2.45 GHz) and a magnetic field (8.75 × 10 ^-2 T) that causes so-called ECR discharge, thereby generating a gas plasma 7.

The substrate 8 is transported and set by a transport means (not shown) so as to be placed on the susceptor 9. A cooling pipe 10 is attached to the susceptor 9, and a coolant circulates from a chiller (not shown) through the cooling pipe 10 to cool the susceptor 9 and thus the substrate 8. The gas is introduced into the bell jar 4 through the gas introduction pipe 11 and is exhausted from the exhaust pipe 12 by an exhaust system (not shown).

This plasma CVD apparatus can be used for both the formation of the antireflection film and the etching process. However, in actual field implementation, it is preferable to use a dedicated device for each in order to avoid cross contamination between processes.

An example in which an antireflection film is actually formed by using the method of the present invention will be shown below with reference to FIG. In Figure 2,
Descriptions of portions not related to the essence of the present invention are omitted, and the drawings are also simplified in comparison with an actual device. As shown in FIG. 2A, a polycide film 102 having a film thickness of 200 nm was formed on a substrate 101 composed of, for example, a single crystal silicon substrate by a normal low pressure CVD method. The polycide film 102 is not particularly limited, but is composed of a laminated film of a polysilicon film and a tungsten silicide film.
Here, in an actual device, on the substrate 101, an element isolation region (LOCOS) by selective oxidation, a gate oxide film,
Although a diffusion layer and the like are formed, they are omitted in the drawing.

After that, the magnetic field μ using the apparatus shown in FIG.
A sialon film (thickness: 30 nm) as the antireflection film 103 was formed by the wave plasma CVD method under the conditions shown in Table 1 below. Note that in FIG. 2A, the resist film 104 is also illustrated for the purpose of explaining the etching for forming a fine pattern in the next step.

[0028]

[Table 1] Gas flow rate: AlBr ₃ / SiH ₄ / H ₂ / N ₂ O / Ar =
10/10/30/50/20 SC Pressure: 1.33Pa Temperature: 400 ° C Microwave: 350W Here, since AlBr ₃ is a solid at room temperature, it is shown in FIG. Reaction chamber 5 shown
Introduced in. The ion density achieved by the plasma CVD apparatus shown in FIG. 1 is on the order of 1 × 10 ¹¹ ions / cm ³ . The dissociation of the source gas highly proceeds in this high density plasma.

When plasma CVD was performed under the above conditions, a sialon film (antireflection film 103) having excellent mechanical strength and heat resistance was formed on the surface of the polycide film 102. The optical constant of this sialon film is such that the refractive index n is 1.0 to 1.0 when i-line or light with a shorter wavelength is used.
It was 5.5, and the extinction coefficient k was 0.0 to 1.5, and it was confirmed that the antireflection effect was excellent.

Example 2 In this example, an antireflection film was formed in the same manner as in Example 1 except that the conditions for forming the antireflection film were changed. In this example, the partial pressure ratio of the silane gas and the nitrous oxide gas was changed in order to change the optical constant.

As in the first embodiment, on the substrate 101,
For example, the polycide film 102, which is a laminated film of tungsten silicide and a polysilicon film, is formed with a thickness of 200 nm by a normal low pressure CVD method. Then, as the antireflection film 103, a 30 nm sialon film was formed by the magnetic field microwave plasma CVD method using the apparatus shown in FIG. 1 under the conditions shown in Table 2 below.

[0032]

[Table 2] Gas flow rate: AlBr ₃ / SiH ₄ / H ₂ / N ₂ O / Ar =
10/10/30/50/20 SC Pressure: 1.33 Pa Temperature: 400 ° C. Microwave: 350 W Under these conditions, plasma CVD is performed to improve the mechanical strength and heat resistance of the surface of the polycide film 102. An excellent sialon film (antireflection film 103) was formed.

In this embodiment, since the partial pressure of the silane gas is increased as compared with the first embodiment, it is possible to form an antireflection film having a large value for both n and k as compared with the first embodiment. it can. Example 3 In this example, after the antireflection film was formed by the method of Example 1 or 2, the antireflection film was etched to obtain a fine pattern. In the present embodiment as well, description of parts that are not related to the essence of the present invention will be omitted, and the drawings will also be simplified as compared to the actual device.

As shown in FIG. 2A, an antireflection film was formed on the polycide film 102 by the method of Example 1 or 2, and then a resist film 104 was formed as a photosensitive film. Next, the resist film 104 is exposed by using a stepper having a short wavelength light such as i-line (λ = 365 nm) or KrF excimer laser (λ = 248 nm) as a light source, and the resist film 104 is subjected to photolithography processing. Was processed into a predetermined pattern. Resist film 104
Underneath, is an antireflection film 10 made of a sialon film.
Since 3 is formed, the standing wave effect of the resist film 104 can be minimized and the resist film 104 can be processed into a fine pattern with high accuracy. The standing wave effect means that the incident light incident on the resist and the reflected light from the resist / base substrate interface due to the incident light cause interference in the resist. The antireflection film 103 is used for the limitation.

Next, using the resist film 104 as a mask,
The antireflection film 103 was etched under the following conditions shown in Table 3 using the apparatus shown in FIG. In order to avoid cross contamination, a plasma CVD apparatus for forming the antireflection film 103 and a plasma CVD apparatus for etching the antireflection film 103 should use different apparatuses even if they have the same configuration. Is preferred.

[0036]

[Table 3] Gas flow rate: S ₂ F ₂ = 30 SCCM Pressure: 1.33 Pa Temperature: 10 ° C Microwave: 850 W (2.45 GHz) RF bias: 30 W At this time, etching proceeds with fluorine radicals, and FIG.
As shown in (b), the sulfur film (sulfur alone film or sulfur compound film) 105 was formed only on the side wall of the antireflection film 103, and the ion energy was adjusted so that the side wall protection effect could be exhibited.

Then, it was heated to 100 ° C. At this time,
The sulfur film 105 was removed. Example 4 In this example, the antireflection film was etched for forming a fine pattern in the same manner as in Example 3 except that the etching conditions were changed.

In the present embodiment as well, description of parts that are not related to the essence of the present invention will be omitted, and the drawings will also be simplified in comparison with the actual device. As shown in FIG.
As shown in (a), an antireflection film is formed on the polycide film 102, and then the resist film 1 is formed as a photosensitive film.
04 was formed. Next, for example, i-line (λ = 365n
m) or KrF excimer laser (λ = 248 nm) or the like as a light source using a stepper having a resist film 1
04 was exposed, and the resist film 104 was processed into a predetermined pattern by photolithography. Since the antireflection film 103 made of a sialon film is formed below the resist film 104, the standing wave effect of the resist film 104 is minimized and the resist film 1 is highly accurately formed.
04 could be processed into a fine pattern.

Next, using the apparatus shown in FIG. 1, the antireflection film 103 was etched under the following conditions shown in Table 4.

[0040]

[Table 4] Gas flow rate: S ₂ F ₂ / H ₂ = 30/5 SCCM Pressure: 1.33 Pa Temperature: 30 ° C Microwave: 850 W (2.45 GHz) RF bias: 30 W At this time, as in Example 3 Then, the etching proceeds with the fluorine radicals, and as shown in FIG.
The sulfur film 105 was formed only on the side wall of the, and the ion energy was adjusted so that the side wall protection effect could be exhibited. Moreover, the incorporation of excessive fluorine radicals by hydrogen radicals allows the sulfur film 105 as the side wall protective film to be thin, and the etching temperature can be raised, contributing to energy saving.

Then, it was heated to 100 ° C. At this time,
As in the case of Example 3, the sulfur film 105 was also removed. Example 5 In this example, the antireflection film was etched for forming a fine pattern in the same manner as in Example 3 except that the etching conditions were changed.

In the present embodiment as well, the description of parts not related to the essence of the present invention will be omitted, and the drawings will also be shown in a simplified manner in comparison with the actual device. As shown in FIG.
As shown in (a), an antireflection film is formed on the polycide film 102, and then the resist film 1 is formed as a photosensitive film.
04 was formed. Next, for example, i-line (λ = 365n
m) or KrF excimer laser (λ = 248 nm) or the like as a light source using a stepper having a resist film 1
04 was exposed, and the resist film 104 was processed into a predetermined pattern by photolithography. Since the antireflection film 103 made of a sialon film is formed below the resist film 104, the standing wave effect of the resist film 104 is minimized and the resist film 1 is highly accurately formed.
04 could be processed into a fine pattern.

Next, using the apparatus shown in FIG. 1, the antireflection film 103 was etched under the following conditions shown in Table 5.

[0044]

[Table 5] Gas flow rate: S ₂ F ₂ / N ₂ = 30/5 SCCM Pressure: 1.33 Pa Temperature: 50 ° C Microwave: 850 W (2.45 GHz) RF bias: 30 W In this embodiment, nitrogen is added. As a result, a more stable deposition of the polythiazyl film was caused by polymerizing the sulfur radicals in which the nitrogen radicals dissociate from the sulfur halide. Therefore, since the side attack of excessive fluorine radicals is small, the etching temperature can be raised, which contributes to energy saving.

In this embodiment, following the etching of the antireflection film 103, the underlying polycide film 102 was etched as shown in FIG. 2C. The conditions were as shown in Table 6 below using a sulfur-based gas.

[0046]

[Table 6] Gas flow rate: S ₂ F ₂ = 30 SCCM Pressure: 1.33 Pa Temperature: -10 ° C Microwave: 850 W (2.45 GHz) RF bias: 30 W After that, heating was performed at 200 ° C. At this time, the sulfur film 105 formed on the sidewalls of the polycide film 102 and the antireflection film 103 was also removed.

The present invention is not of course limited to the above-mentioned embodiment, and its configuration, conditions and the like can be changed as appropriate without departing from the spirit of the present invention. For example, the plasma CVD apparatus used in the method of the present invention is not limited to the magnetic field microwave plasma CVD apparatus, and ICP (Inductive coupled plasma) CVD
Equipment, helicon wave plasma CVD equipment, TCP (Transf
ormer coupled plasma) CVD equipment, parallel plate electrode type C
A VD device or other plasma CVD method may be used.

The lower layer film on which the antireflection film is formed is not limited to the polycide film, but may be a polysilicon film, an aluminum alloy film, an aluminum film, a tungsten film,
The silicide film or an insulating film such as an interlayer insulating film is not particularly limited.

[0049]

As described above, according to the present invention, it is possible to form an antireflection film made of a compound containing no carbon, which has been a bottleneck in the prior art, and to perform etching processing without using CFCs. In addition, since the anisotropic shape can be secured, a highly precise fine pattern can be formed, and the semiconductor integrated circuit can be manufactured by a highly reliable process.

[Brief description of drawings]

FIG. 1 is a schematic view of a magnetic field microwave plasma CVD apparatus used for carrying out the present invention.

2A to 2C are schematic cross-sectional views showing a process of forming an antireflection film and an etching process.

[Simple explanation of symbols]

1; Magnetron 101; Substrate 2; Microwave 102; Polycide film 3; Waveguide 103; Sialon antireflection film 4; Quartz bell jar 104; Resist film 105; Sulfur film (sidewall protective film) 5; Reaction chamber 6; Solenoid coil 7 Gas plasma 8; substrate 9; susceptor 10; cooling pipe 11; gas introduction pipe 12; exhaust pipe

Claims (13)

[Claims] 1. A method of forming an antireflection film used when exposing a photosensitive film applied on a substrate, wherein heat resistant ceramics is used as the antireflection film. . 2. The antireflection film is a compound ceramic containing at least silicon.
The method for forming an antireflection film as described in 1. 3. The method for forming an antireflection film according to claim 1, wherein the antireflection film is formed by using at least a gas containing silicon and a gas containing nitrogen. 4. The antireflection film according to claim 3, wherein the optical constant of the antireflection film is changed by changing the partial pressure ratio between the gas containing silicon and the gas containing nitrogen. Method. 5. The method for forming an antireflection film according to claim 1, wherein the antireflection film is sialon. 6. The antireflection film is a magnetic field μ-wave plasma CV
The method for forming an antireflection film according to claim 1, wherein the antireflection film is formed by the D method. 7. A step of forming an antireflection film on an object to be processed on which a fine pattern is to be formed, a step of forming a photosensitive film on the antireflection film, and exposing the photosensitive film. A method for forming a fine pattern, comprising: a step of etching the photosensitive film into a predetermined pattern; and a step of etching the antireflection film using the photosensitive film as a mask. A method for forming a fine pattern, wherein a gas containing at least sulfur is used when etching the film. 8. The method for forming a fine pattern according to claim 7, wherein the etching is dry etching using low temperature plasma of a gas containing at least sulfur. 9. The gas containing sulfur is S ₂ F ₂ , SF
₂ , SF ₄ , S ₂ F ₁₀ , S ₃ Cl ₂ , SCl ₂ , S ₂ Br ₂ , S
9. The method for forming a fine pattern according to claim 7, wherein at least one gas selected from Br ₂ and S ₃ Br ₂ is used. 10. The gas containing sulfur is S ₂ F ₂ , S
F ₂ , SF ₄ , S ₂ F ₁₀ , S ₃ Cl ₂ , SCl ₂ , S ₂ Br ₂ , S
A gas obtained by mixing at least one first gas selected from Br ₂ and S ₃ Br ₂ and at least one _second gas selected from H ₂ , H ₂ S and a silane compound is used. The method for forming a fine pattern according to claim 7. 11. The gas containing sulfur is S ₂ F ₂ , S
F ₂ , SF ₄ , S ₂ F ₁₀ , S ₃ Cl ₂ , SCl ₂ , S ₂ Br ₂ , S
The method for forming a fine pattern according to claim 7, wherein a gas in which a gas containing nitrogen is mixed with at least one first gas selected from Br ₂ and S ₃ Br ₂ is used. 12. The method for forming a fine pattern according to claim 7, wherein the etching is dry etching performed at a temperature not higher than the temperature at which sulfur and its compounds sublime. 13. The etching according to claim 7, wherein the etching is performed so as to continuously etch the object to be processed which is the base, following the etching process of the antireflection film. Method for forming fine pattern.