JPH05217842A - Formation of hole pattern - Google Patents

Abstract

PURPOSE:To make it possible to make in a negative resist film a fine hole pattern which has an excellent size controllability and has the side wall not too much tapered. CONSTITUTION:In the first process, a negative resist film 12 is formed on a substrate 11. In the second process, a shielding pattern 21 of a photo mask 20 is transferred to the resist film by exposure. And, in the third process, the exposed negative resist film 12 is developed and a hole pattern 13 is formed in the negative resist film 12. In this method, the shielding pattern 21 of the photo mask 20 is formed in the size to correspond to 1.1-1.5 times the hole pattern 13 to be formed. As for the exposure, overexposure is performed.

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 hole pattern formed in a resist film in a photolithography process in a semiconductor device manufacturing process.

[0002]

2. Description of the Related Art In a photolithography technique for forming a contact hole having a design dimension of 0.35 μm or less, krypton fluoride (KrF) excimer laser light (wavelength 248 nm) is used as an exposure light beam. A negative resist is usually used to perform the exposure with the KrF excimer laser light.

[0003]

However, as shown in FIG. 4, when the hole pattern 42 is formed in the resist film 41 made of a negative resist, the shape of the hole pattern 42 is small on the opening side and large on the bottom side. It becomes so-called reverse taper. Further, in order to suppress the standing wave effect, when a negative resist having a relatively high absorptance of exposure light rays is used, the inverse taper of the hole pattern 42 is further increased.
As described above, when the hole pattern 42 has an inverse taper, the dimension of the hole pattern 42 changes when the resist film 41 is thinned during the dry etching, and the film to be etched 4 is etched.
The size of the contact hole 44 formed in No. 3 varies. For this reason, the size conversion difference between the light-shielding pattern (not shown) of the photomask and the contact hole 44 becomes large, so that the dimensional controllability of the contact hole 44 deteriorates. Further, since the tapered state of the hole pattern 42 cannot be observed from above the hole pattern 42 with an optical microscope (not shown), quality control of the hole pattern 42 cannot be performed.

An object of the present invention is to provide a method for forming a hole pattern having excellent dimensional controllability.

[0005]

The present invention has been made to achieve the above object. That is, it is a method of forming a hole pattern in a negative resist film, in which a negative resist film is formed on a substrate in a first step, and then in a second step, the size of the hole pattern to be formed is adjusted. 1.
After the light-shielding pattern of the photomask is transferred to the negative resist film by overexposure using a photomask having light-shielding formed to have a size of 1 to 1.5 times,
In the third step, the exposed negative resist film is developed to form a hole pattern in the negative resist film.

[0006]

In the above method, an image of a light-shielding pattern having a high contrast is formed on the negative resist film by performing overexposure. Further, by forming the light-shielding pattern of the photomask to have a size 1.1 to 1.5 times the size of the hole pattern to be formed, over-exposure results in a hole pattern having a predetermined size. Further, in the hole pattern formed by the above method, the inclination angle of the side wall becomes more vertical than that in the hole pattern formed by using a normal photomask with a normal exposure amount. Therefore, the dimensional conversion difference of the hole pattern formed by the above method becomes small.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of the present invention will be described with reference to the process chart of FIG. In the drawing, as an example, a method for forming a contact hole resist mask will be described. As shown in (1) of FIG. 1, the substrate 11 is made of, for example, a silicon substrate. First, in the first step, the negative resist film 12 is formed on the upper surface of the substrate 11 by, for example, 0.7 by a normal resist coating technique.
It is formed to a thickness of μm. The aforementioned negative resist film 12, a relatively large ones (for example absorption coefficient 0.92 .mu.m ^{- 1} about one) is the absorption coefficient of exposure light is used. Then, the negative resist film 12 is prebaked. As the prebaking conditions, for example, the prebaking temperature is set to 90 ° C. and the prebaking time is set to 90 seconds.

Next, as shown in FIG. 1B, exposure is performed in the second step. In this exposure, the photomask 20 is irradiated with the exposure light beam 31, and the light shielding pattern 21 of the photomask 20 is transferred to the negative resist film 12 through the reduction exposure system 32. In the figure, the shaded area shown by the broken line is the exposed area. As the exposure light beam, for example, krypton fluoride (KrF) excimer laser light (having a wavelength of 248 nm) is used. The reduction exposure system 32 has, for example, an aperture ratio of 0.3.
7 is used. The size of the light shielding pattern 21 of the photomask 20 is 1.1 to 1.5 times the size of the hole pattern (13) to be formed. For example, the photomask 20 when the reduction ratio of the reduction exposure system 32 is 5: 1 will be described as an example. When the size of the hole pattern (13) to be formed is set to 0.4 μm, the size of the light shielding pattern 21 of the photomask 20 is, for example, about 1.3 times the size of the hole pattern (13) to be formed.
Eight times 0.55 μm square is formed. In the above exposure,
An exposure amount larger than the normal exposure amount is applied to the negative resist film 12
Perform overexposure to irradiate. This overexposure is performed, for example, at about 50% to 100% increase over the normal exposure amount.
Then, post-exposure bake (post-exposure bake) processing is performed after the exposure. As the processing conditions, for example, the temperature is set to 110 ° C. and the baking time is set to 90 seconds.

As a result of such overexposure, the light intensity distribution on the negative resist film 12 becomes as shown in (3) of FIG. The vertical axis of FIG. 3C shows the light intensity, and the horizontal axis shows the position corresponding to the surface of the negative resist film 12 shown in FIG. In the light intensity distribution I shown in the figure, the light intensity is Io in the exposed portion and the light intensity is 0 in the unexposed portion.
become. Further, the change in contrast becomes large at the position corresponding to the edge of the light shielding pattern 21. Therefore, the light shielding pattern 2 formed on the negative resist film 12
The image of 1 has a high contrast.

Thereafter, as shown in (4) of FIG. 1, in the third step, a normal developing process is performed to form a hole pattern 13 in the negative resist film 12. The development processing conditions are, for example, 10 minutes of paddle development. Thus, the contact hole resist mask 10 formed by forming the hole patterns 13 in the negative resist film 12 is completed.

The hole pattern 13 formed as described above
Has a side wall inclination angle θ of approximately 85 ° to 90 °. Further, the dimension w of the hole pattern 13 is a designed dimension that is almost aimed. In the above forming method, the negative resist film 12 is formed on the upper surface of the substrate 11. However, a film (not shown) such as a film to be etched is formed on the substrate 11, and the negative resist film is formed on the film. It is also possible to form 12.

In the above forming method, when the light shielding pattern 21 is formed to be smaller than 1.1 times the dimension w of the hole pattern 13, the inclination angle θ of the side wall of the hole pattern 13 becomes smaller than 85 °. When the light shielding pattern 21 is formed to have a size larger than 1.5 times the dimension w of the hole pattern 13 to be formed, the dimension of the hole pattern 13 does not reach a desired design dimension even if overexposure is performed. Further, since the depth of focus of exposure becomes shallow, focusing becomes difficult.

Next, the relationship between the exposure amount of the krypton fluoride excimer laser light (wavelength is 248 nm) and the inclination angle of the side wall of the hole pattern will be described with reference to FIG. In the figure, the vertical axis represents the exposure amount E, and the horizontal axis represents the inclination angle θ of the side wall of the hole pattern.
As shown in the drawing, the inclination angle θ of the side wall of the hole pattern is increased as the exposure amount E is increased regardless of whether the light-shielding pattern dimension of the photomask is 2.0 μm □ or 2.75 μm □.
Will grow. For exposure, an apparatus having a reduction exposure system with a reduction ratio of 5: 1 was used. For example, when the light-shielding pattern size of the photomask is 2.0 μm □, the exposure amount is 90 m.
At J / cm ² or more, the side wall inclination angle θ is 85 ° to 90 °. The light-shielding pattern size of the photomask is 2.75μ.
In the case of m □, when the exposure amount is 140 mJ / cm ² or more, the inclination angle θ of the side wall is 85 ° to 90 °. Note that the normal exposure amount for reducing the light-shielding pattern size to 5: 1 is 60 mJ /
cm ² .

Next, the relationship between the exposure amount of the krypton fluoride excimer laser light (wavelength is 248 nm) and the size of the hole pattern will be described with reference to FIG. 3 using the size of the light shielding pattern of the photomask as a parameter. In the figure, the vertical axis indicates the exposure amount E, and the horizontal axis indicates the hole pattern dimension w. As shown in FIG. 3, the light-shielding pattern dimension of the photomask is 2.0 μm □
In both cases of 2.75 .mu.m.quadrature., The dimension w of the hole pattern decreases as the exposure amount E increases. For exposure, an apparatus having a reduction exposure system with a reduction ratio of 5: 1 was used.
For example, to form a hole pattern having a sidewall pattern inclination angle of 85 ° to 90 ° and a diameter of 0.4 μm, 2.75
Using a photomask with a μm □ light-shielding pattern,
The exposure dose may be set to 140 mJ / cm ² . Further, for example, to form a hole pattern having a sidewall pattern inclination angle of 85 ° to 90 ° and a diameter of 0.3 μm, 2.0 μm
The exposure amount may be set to 90 mJ / cm ² using a photomask having a light-shielding pattern □. Note that the normal exposure amount for reducing the light-shielding pattern size to 5: 1 is 60 mJ.
/ Cm ² .

As described above, the size of the light-shielding pattern of the photomask is made larger than the size of the hole pattern to be formed, and the overexposure is performed, so that the diameter of 0.3 μm, which has been conventionally difficult to form. The hole pattern can be formed with the side wall inclination angle of the hole pattern being 90 ° or close to 90 °.

[0016]

As described above, according to the present invention,
Since exposure is performed by overexposure, exposure with high contrast can be performed. Therefore, the shape of the hole pattern is hardly tapered. In addition, the size of the light-shielding pattern of the photomask is 1.1 times the size of the hole pattern to be formed.
The size of the hole pattern can be formed to a predetermined size because it is formed to a size corresponding to double to 1.5 times and overexposure is performed using the photomask. Therefore, it becomes possible to form a fine hole pattern of, for example, about 0.3 μm or less in the negative resist film.

[Brief description of drawings]

FIG. 1 is a process drawing of an example.

FIG. 2 is a relationship diagram between an exposure amount and a side wall inclination angle of a hole pattern.

FIG. 3 is a relationship diagram between an exposure amount and a hole pattern size.

FIG. 4 is an explanatory diagram of a problem.

[Explanation of symbols]

 11 substrate 12 negative resist film 13 hole pattern 20 photomask 21 light-shielding pattern

Claims (1)

[Claims] 1. A first step of forming a negative resist film on a substrate, a second step of transferring a light-shielding pattern of a photomask to the negative resist film by exposure, and the exposed negative resist film. Is subjected to a developing treatment to form a hole pattern in the negative type resist film, and the size of the light-shielding pattern of the photomask is set to the size of the hole pattern to be formed. A method for forming a hole pattern, which is characterized in that the hole pattern is formed to a size of 1.1 to 1.5 times and the exposure is performed by overexposure.