JPH07226396A - Pattern forming method - Google Patents

Abstract

PURPOSE:To form a pattern with a high precision by using low etching strength resist corresponding to a short wavelength region exposure light and facilitate the fine processing by a semiconductor device. CONSTITUTION:A reflection-proof film forming layer 13 made of organic material is formed on the upper surface of a foundation layer 12. The reflection-proof film forming layer 13 is subjected to a heat treatment at 250 deg.C to a form a reflection-proof film 14. A resist film 15 is formed on the upper surface of the reflection-proof film 14 and an aperture pattern 16 is formed in the resist film 15 by lithography using an excimer laser. The reflection-proof film 14 is subjected to anisotropic etching by using the resist film 15 as a mask. The foundation layer 12 is subjected to anisotropic etching by using the reflection- proof film 14 as a mask under the etching conditions to have the etching selection ratio such as reflection-proof film:foundation layer =1:5.5-7.0. With this constitution, a pattern 18 is formed in the foundation layer regardless of the etching strength of the resist film.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a pattern in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In the manufacturing process of semiconductor devices, the wavelength of exposure light used in lithography is narrowed and the band thereof is narrowed along with the miniaturization of element structures. In pattern exposure using such exposure light, a standing wave is easily formed in the height direction of the resist by the exposure light reflected by the underlayer.

Therefore, for example, as shown in FIG. 2, the pattern forming method for forming a contact hole in the insulating layer 22 formed on the semiconductor substrate 21 is as follows. First, as shown in FIG. 2A, an antireflection film 23 is formed on the upper surface of the insulating layer 22 forming the contact hole, and a resist film 24 is formed on the upper surface of the antireflection film 23. Then, the resist film 24 is patterned by lithography using exposure light in the ultraviolet region such as KrF excimer laser light. Then Fig. 2 (2)
As shown in FIG. 2, the antireflection film 24 is etched using the patterned resist film 24 as a mask, and then, as shown in FIG.
As shown in (3), the insulating layer 22 is etched using the resist film 24 as a mask.

In the above pattern forming method, the antireflection film 2
3 prevents the exposure light from being reflected during lithography, so that no standing wave is formed in the resist film 24. Therefore, a fine pattern is formed on the resist film by lithography using the exposure light in the ultraviolet region.

[0005]

However, the above pattern forming method has the following problems. That is, when the pattern forming method is performed, it is necessary to use, as the resist film, a photosensitive composition that is transparent to exposure light in the short wavelength region such as the KrF excimer laser light. However, since such a resist film has low etching resistance, it does not function sufficiently as an etching mask. For this reason, the dimensional conversion difference between the pattern formed on the resist film and the pattern formed on the underlayer by lithography becomes large, and it is not possible to perform highly accurate pattern formation on the underlayer. This is a factor that hinders fine processing during element formation.

[0006] Therefore, an object of the present invention is to provide a pattern forming method which solves the above problems, thereby enabling fine processing at the time of element formation in a semiconductor device manufacturing process.

[0007]

The pattern forming method of the present invention that achieves the above object is performed in the following procedure. First, an antireflection film is formed on a base layer forming a pattern. Then, a resist film is formed on the upper surface of the antireflection film, and the resist film is patterned by lithography. Next, the antireflection film is anisotropically etched using the patterned resist film as a mask. After that, the underlying layer is anisotropically etched using the antireflection film as a mask. The anisotropic etching of the base layer is performed under the etching conditions that the etching selection ratio is antireflection film: base layer = 1: 5.5 to 7.0. The antireflection film is formed by heating the antireflection film forming layer made of an organic material applied on the underlayer at a temperature of 250 ° C to 350 ° C.

[0008]

In the above pattern forming method, since the underlayer is etched by using the antireflection film as a mask, the pattern formation is performed without being influenced by the etching resistance of the resist film. At this time, since the underlayer is anisotropically etched with the above selection ratio, the underlayer is etched with no size conversion difference with respect to the antireflection film. Further, the antireflection film formed as described above has an antireflection function against exposure light, and has the above etching selectivity and etching resistance with respect to the underlying layer.

[0009]

EXAMPLE A pattern forming method of an example of the present invention will be described with reference to FIG. In the first embodiment, the silicon oxide film formed on the upper surface of the substrate made of silicon has a thickness of 0.3 μm.
The case will be described as an example in which a contact hole having an opening diameter of 1 is formed by patterning. First, as shown in FIG. 1A, a silicon oxide film for patterning contact holes is formed as a base layer 12 on the upper surface of a substrate 11 made of silicon. The silicon oxide film to be the base layer 12 is formed by the CVD method to have a film thickness of 400 nm, for example.

Then, an antireflection film forming layer 13 made of a polysulfone-based organic material is formed on the upper surface of the underlayer 12 by using the following method.
Spin coating to a film thickness of 0 nm. Then, the antireflection film forming layer 13 is heat-treated at a temperature of 250 ° C. to form the antireflection film 14.

Next, as shown in FIG. 1B, a resist film 15 made of, for example, a chemically amplified photosensitive composition is applied on the upper surface of the antireflection film 14 so as to have a thickness of 840 nm. The resist film 15 is formed of a material having a good lithographic property with respect to exposure light in a short wavelength region such as KrF excimer laser light.

Then, the resist film 15 is subjected to lithography using, for example, the KrF excimer laser light as the exposure light. As a result, the resist film 15
Then, the opening pattern 16 having the opening diameter r ₁ = 0.3 μm is formed.

Then, as shown in FIG. 1C, the antireflection film 14 is anisotropically etched by reactive ion etching (RIE) using the resist film 15 as a mask. Then, the opening pattern 17 is formed in the antireflection film 14. In this etching, the etching conditions are set so that the etching selection ratio is resist film 15: antireflection film 14 = 1: 0.3 to 1.4. As the etching gas, for example, a fluorine-based gas or an argon-based gas is used.

Then, for example, when oxygen (O ₂ ) / trifluoromethane (CHF ₃ ) is used as the etching gas, the gas pressure in the etching atmosphere is 5 to 10 Pa,
Etching temperature 10 ~ 30 ℃, PF power 1000
˜1300 W, etching gas flow rate O ₂ / CHF ₃ =
Etching is carried out at a setting of 5-40 / 50-80 sccm. When etching is performed as described above, the etching selection ratio is as follows: resist film 15: antireflection film 14 = 1:
It will be about 0.3.

For example, when O ₂ / Ar is used as the etching gas, the gas pressure in the etching atmosphere is 1 to 4 Pa, the etching temperature is 10 to 30 ° C., and the etching gas flow rate is O ₂ / Ar = 25. Etching is performed by setting / 25 sccm. When etching is performed as described above, the etching selectivity becomes about resist film 15: antireflection film 14 = 1: 1.

Next, as shown in FIG. 1D, the underlayer 12 is anisotropically etched using the antireflection film 14 as a mask. In this anisotropic etching, the etching conditions are set so that the etching selection ratio is antireflection film 14: underlayer 12 = 1: 5.5 to 7.0. For example, O ₂ / CHF
_When a fluorine-based etching gas such as ₃ is used, the etching is performed in the same manner as the etching of the antireflection film 14. By the above etching, the pattern 18 to be the contact hole is formed in the base layer 12.

In the above pattern forming method, the resist film 1
The antireflection film 14 formed on the lower surface of the substrate 5 prevents the exposure light from being reflected during the lithography. Therefore, it becomes possible to perform exposure using exposure light in a short wavelength region such as KrF excimer laser light, and a fine opening pattern 16 having an opening diameter r ₁ = 0.3 μm is formed in the resist film 15. The resist film 15 is used as a mask to etch the antireflection film 14 at an etching selection ratio of 1: 0.3 to 1.4.
Since the etching is performed in step ₁ , an opening pattern 17 having a smaller dimensional conversion difference than the opening diameter r ₁ of the opening pattern 16 formed in the resist film 15 is formed in the antireflection film 14. The antireflection film 14 is formed by heating the antireflection film forming layer 15 made of a polysulfone-based organic material at 250 ° C., and has high etching resistance. Therefore, the antireflection film 14 sufficiently functions as an etching mask when anisotropically etching the underlayer 12. Further, during etching, a sidewall protective film made of a sulfur compound is formed on the etching sidewall, so that a good anisotropic shape is maintained. Since the underlayer 12 is anisotropically etched using the antireflection film 14 as a mask, the pattern formation on the underlayer 12 is performed without being affected by the etching resistance of the resist film 15. Then, an opening-shaped pattern 18 having a small dimensional conversion difference with respect to the opening pattern 17 formed in the antireflection film 14 is formed in the base layer 12.

Therefore, the underlying layer 12 has an opening pattern 1 formed in the resist film 15 by lithography.
A pattern 18 having a small dimensional conversion difference from that of 6 is formed.
Here, an opening pattern 16 having an opening diameter r ₁ = 0.3 μm is formed in the resist film 15, and an opening diameter r ₂ is formed in the underlayer 12.
= 0.33 μm, the pattern 18 was formed. It was confirmed that in the conventional method, the dimensional conversion difference was improved as compared with the case where the pattern having the opening diameter = 0.38 μm was formed in the underlayer. Further, the variation in the dimensional conversion difference is ± 0.030 μm in the conventional method, but is improved to ± 0.024 μm in the above-described embodiment.

In the next embodiment, the case where a pattern is formed on the underlayer 12 made of, for example, polysilicon will be described as an example. In this case, the antireflection film 14 and the resist film 1
5. Anisotropic etching of the antireflection film 14 using the opening pattern 16 formed in the resist film 15 and the resist film 15 as a mask is performed in the same manner as in the above-described embodiment.

Then, as shown in FIG. 1D, in the anisotropic etching of the underlayer 12 using the antireflection film 14 as a mask, the etching selection ratio is the same as that described above.
4: Etching conditions are set so that the underlying layer 12 = 1: 5.5 to 7.0. For example, when a chlorine-based gas such as chlorine (Cl ₂ ) / hydrogen bromide (HBr) gas is used as the etching gas, the gas pressure in the etching atmosphere is 13 to 40 Pa and the etching temperature is 10 to 30.
° C., 300～800W the RF power, the etch gas flow rate Cl ₂ / HBr = 50~80 / 50~80sccm
Set to and perform etching.

As a result, the opening pattern 18 having a good dimensional conversion difference is formed in the base layer 12 made of polysilicon, as in the above embodiment.

In the above two embodiments, the case where the underlayer 12 is a single layer has been described. However, the pattern forming method of the present invention is not limited to this, and is also applicable to the case where the underlayer 12 has a multilayer structure of two or more layers. In this case, the underlayer 1
It is also possible to use a resist film as 2.

[0023]

As described above, according to the pattern forming method of the present invention, by using the antireflection film having high etching resistance as the etching mask of the underlayer,
The pattern can be formed in the underlayer regardless of the etching resistance of the resist film. For this reason, it is possible to form a pattern with high dimensional accuracy by using a resist film corresponding to exposure light in a short wavelength region, which generally has low etching resistance. Therefore, fine processing of the element becomes possible in the manufacturing process of the semiconductor device.

[Brief description of drawings]

FIG. 1 is a schematic sectional view illustrating an example.

FIG. 2 is a schematic sectional view illustrating a conventional example.

[Explanation of symbols]

 12 Underlayer 13 Antireflection Film Forming Layer 14 Antireflection Film 15 Resist Film 18 Pattern

Claims (3)

[Claims] 1. A step of forming an antireflection film on a base layer for forming a pattern, a step of forming a resist film on an upper surface of the antireflection film, and then patterning the resist film by lithography, and the pattern. Patterning, which comprises a step of anisotropically etching the antireflective film with a masked resist film as a mask, and a step of anisotropically etching the underlayer with at least the antireflective film as a mask. Method. 2. The pattern forming method according to claim 1, wherein the anisotropic etching of the underlayer is performed under an etching condition that an etching selection ratio is an antireflection film: an underlayer = 1: 5.5 to 7.0. A method for forming a pattern, which is characterized by being performed. 3. The pattern forming method according to claim 1 or 2, wherein the antireflection film is a heat treatment of an antireflection film forming layer made of an organic material applied on the underlayer at a temperature of 250 ° C. to 350 ° C. A method for forming a pattern, which comprises: