JPH0954438A - Photoresist pattern and its forming method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a photoresist pattern in which a pattern showing high verticality of side faces cap be maintained even when the pattern is large in size, and to obtain its forming method. SOLUTION: A positive resist 5a is formed on a base layer 1 and a chemically amplified crosslinked negative resist pattern 2a having a line length L4 and high verticality of side faces is formed on the side wall around the positive resist 5a. Even when the pattern is baked, the chemically amplified crosslinked negative resist pattern 2a maintains the high verticality and the positive resist 5a which has a large volume hardly shrinks by baking. Therefore, the photoresist pattern 6 can maintain high verticality of side faces.

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 photoresist pattern, and more particularly to a photoresist pattern using a chemically amplified cross-linked negative resist and a method for forming the same.

[0002]

2. Description of the Related Art In a semiconductor device manufacturing process, an underlying layer such as a semiconductor substrate is selectively processed by etching or ion implantation. In the case of performing such processing, first, for the purpose of selectively protecting the processed portion of the underlayer, a composition that is exposed to actinic rays such as ultraviolet rays, X-rays, and electron beams, a so-called photosensitive resist film (hereinafter referred to as resist) (Name) is formed on the underlayer.

When the actinic ray is an ultraviolet ray or an X-ray, a mask is used, and when the actinic ray is an electron beam, a photoresist pattern is formed on the underlayer by direct drawing. The resist is classified into a positive type and a negative type. The former is a resist in which an exposed portion is dissolved in a developing solution but the unexposed portion is not dissolved, and the latter is a resist having reverse characteristics. At present, positive resists are generally used in the manufacture of semiconductor devices, and those consisting of a photosensitizer composed of a naphthoquinonediazide compound and a base resin composed of an alkali-soluble resin such as a novolak resin are mainly used. .

By the way, in recent years, semiconductor devices with higher performance
With high integration, high-energy ion implantation and high-precision etching are required, and further high precision is required for miniaturization of circuit patterns and transfer of circuit patterns designed on a mask. In particular, when ion implantation with high energy is performed, if the resist film is thin, ions are injected into the underlying layer below the resist, so that a thicker film than usual is required. However, as the film thickness increases, it becomes difficult to obtain a high resolution and a good shape, that is, a pattern shape in which the verticality of the edge portion is high.

Therefore, first, a method of forming a conventional photoresist pattern composed only of a positive resist (hereinafter referred to as positive resist) and a photoresist pattern composed only of a negative resist (hereinafter referred to as negative resist) will be described. explain. First, a conventional method of forming a photoresist pattern composed of only positive resist will be described with reference to FIGS. First, referring to FIG. 11, positive resist 5 is applied on underlayer 1 and prebaked at 85 ° C. for 70 seconds. In this case, the positive resist 5 is formed with a film thickness of, for example, about 5 μm.

Referring to FIG. 12, a stepper (reduction projection exposure apparatus) for irradiating and exposing the i-line (wavelength 365 nm) as the exposure light 4 is used to form a desired photoresist pattern. The exposure light 4 is transmitted through the photomask 3 to the positive resist 5 with, for example, exposure energy 800.
Irradiate at mJ / cm ² .

Next, referring to FIG. 13, a post exposure bake (hereinafter abbreviated as PEB) is performed at 120 ° C.
For 90 seconds.

After that, development is performed using an alkaline aqueous solution (2.38% by weight of tetramethylammonium hydroxide) to form a photoresist pattern 5b as shown in FIG.
To form

Here, as a specific example of the photoresist pattern shown in FIG. 14, a partial enlarged view of a photoresist pattern 5b formed by using a commercially available i-line positive resist is shown in FIG. In the photoresist pattern shown in FIG. 15, the positive resist 5 formed on the underlayer 1
The inclination width L3 of the side wall portion of b increases as the size of the positive resist pattern in the surface direction of the underlayer 1 increases, and the inclination width L3 is about 1.8 μm for a photoresist pattern having a pattern size of 1000 μm or more. This is because the positive resist (composed of the photosensitizer made of the above-mentioned naphthoquinonediazide compound and the base resin made of an alkali-soluble resin such as a novolak resin) absorbs exposure light in the film and is closer to the resist surface. This is because the intensity of the exposure light becomes weaker nearer the back surface of the resist.

Therefore, when high-energy ion implantation is performed, ions do not pass through the portion where the film thickness of the slope is relatively large,
Since ions may pass through the relatively thin portion, there is a portion where ions are implanted into the underlying layer 1 and a portion where ions are not implanted under the inclination. Therefore, the substantial pattern dimension L1 is
It becomes longer than the desired pattern dimension L2 by a maximum of the inclination width L3.

Further, in this description, the case where the film thickness of the positive resist 5 is about 5 μm has been described, but when the film thickness of the positive resist 5 exceeds about 2 μm, the inclination width L
3 starts to increase, and generally in a positive resist, the larger the pattern size, the larger the inclination width.

As described above, the photoresist pattern formed only of the positive resist has a disadvantage that the larger the pattern dimension, the larger the inclination of the side wall portion.

Next, a method of forming a photoresist pattern composed only of a chemically amplified cross-linked negative resist as a conventional negative resist will be described with reference to FIGS.
First, referring to FIG. 16, a chemically amplified cross-linked negative resist 2 is applied on underlayer 1 and prebaked at 110 ° C. for 70 seconds. In this case, the chemically amplified cross-linked negative resist 2
Is formed to have a film thickness of, for example, about 5 μm.

Next, referring to FIG. 17, a stepper for irradiating and exposing the i-line as the exposure light 4 is used to expose the exposure light 4 through the photomask 3 to a shape other than a desired photoresist pattern shape. The chemically amplified negative resist 2 is irradiated with an exposure energy of 110 mJ / cm ² , for example.

Next, referring to FIG.
Perform at 120 ° C. for 120 seconds.

Thereafter, development is carried out using an alkaline aqueous solution (2.38% by weight of tetramethylammonium hydroxide) to form a photoresist pattern 2 as shown in FIG.
b is formed.

Similarly to the positive resist, the larger the pattern size of the photoresist pattern 2b is, the larger the inclination width L3 of the side wall portion of the photoresist pattern 2b becomes.
Even with a photoresist pattern of 00 μm or more, its inclination width is about 0.85 μm, which is less than half that of the positive resist. This phenomenon is caused by a contraction phenomenon as described later.

As described above, the chemically amplified cross-linking negative resist has an advantage that a photoresist pattern having higher verticality can be formed than the positive resist. This is because
This is because the chemically amplified cross-linking negative resist has high transparency, so that even with a thick film, there is almost no attenuation of the light intensity of the exposure light from near the resist surface to near the back surface.

However, in this chemically amplified cross-linked negative resist, as shown in FIG. 20, when baking is performed after development, shrinkage of the photoresist pattern 2b further occurs, and the inclination width L3 of the sidewall portion of the photoresist pattern 2b is developed. It has the disadvantage of being larger than immediately after. As an example,
When baking is performed at 150 ° C. for 90 seconds after the development, the inclination width L3 is about 0.2 μm larger than that before the baking. Therefore, when the baking is performed three times, the inclination width of the edge of the photoresist pattern 2b becomes 1.05 μm.

Therefore, when high-energy ion implantation is performed, ions do not pass through the portion where the film thickness of the slope is relatively thick,
Since ions may pass through the relatively thin portion, there is a portion where ions are implanted into the underlying layer 1 and a portion where ions are not implanted under the inclination. Therefore, the substantial pattern dimension L1 is
It becomes shorter than the desired pattern dimension L2 by a maximum of the inclination width L3.

Next, the contraction mechanism of the chemically amplified negative resist will be described in detail. The chemically amplified cross-linking negative resist described here is composed of a novolak resin as a base resin, a melamine compound that acts as a cross-linking agent, and a photo-acid generator. When such a chemically amplified cross-linking negative resist is irradiated with predetermined light, an acid is generated from the photo-acid generator in the resist. Then, when PEB is applied, a crosslinking reaction occurs between the crosslinking agent and the base resin using an acid as a catalyst to insolubilize it in the developing solution. Cause the contraction phenomenon. As a matter of course, the larger the pattern size of the photoresist pattern, the greater the amount of shrinkage, and the greater the inclination width of the side wall portion. Furthermore, the cross-linking reaction is promoted by the remaining acid even after the baking after the development, so that the inclination width of the side wall of the photoresist becomes large depending on the volume of the photoresist.

On the other hand, the positive resist does not cause a chemical reaction such as a cross-linking type reaction, and therefore has an advantage that it does not shrink even if baked after development.

[0023]

As described above, the photoresist pattern formed only of the positive resist has a problem that the larger the pattern dimension, the larger the inclination of the side wall portion thereof.

Further, even with a photoresist pattern composed only of a chemically amplified cross-linking negative resist, there is a problem that when baking is carried out after development, the larger the pattern size, the larger the inclination of the side wall portion.

The present invention has been made to solve the above problems, and an object thereof is to obtain a photoresist pattern capable of maintaining a highly vertical pattern shape even if the pattern dimension is large, and a method for forming the same. To do.

[0026]

According to a first aspect of the present invention, there is provided a positive resist pattern formed on an underlayer and a side wall portion around the positive resist pattern, and an edge is formed. And a chemically amplified cross-linked negative resist pattern having a line width that can be maintained substantially vertical.

In the problem solving means according to claim 2 of the present invention, the line width is 5 μm or less.

The problem solving means according to claim 3 of the present invention is
A step of preparing an underlayer, a step of applying a chemically amplified crosslinkable negative resist on the underlayer, and a step of selectively removing the chemically amplified crosslinkable negative resist to form a contour portion of a desired photoresist pattern shape. And a step of leaving a chemically amplified cross-linking negative resist pattern having a line width shape capable of maintaining the edges substantially vertical, and applying a positive resist on the underlayer exposed by the removal of the negative resist. And a step of selectively removing the positive resist outside the contour portion of the shape of the desired photoresist pattern.

In the problem solving means according to claim 4 of the present invention, the line width is 5 μm or less.

[0030]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1. FIG. 1 is a diagram showing a photoresist pattern according to the first embodiment of the present invention. In FIG. 1, 1 is a base layer, 2a is a chemically amplified cross-linking negative resist pattern composed of a novolak resin as a base resin, a melamine compound acting as a cross-linking agent and a photo-acid generator, and 5a is a positive resist (positive resist). Pattern). A photoresist pattern 6 is composed of the chemically amplified cross-linking negative resist 2a and the positive resist 5a.

As shown in FIG. 1, the positive resist 5a is formed on the underlayer 1, and a chemically amplified cross-linking negative resist pattern 2a is formed on the side wall portion around the positive resist 5a. Chemically amplified cross-linked negative resist pattern 2
The line width L4 of a is a line width with high verticality (that is, the edge can be kept substantially vertical).

As described above, in this embodiment, most of the photoresist pattern is formed by the positive resist, and the side wall portions around the positive resist are formed by the chemically amplified cross-linking negative resist pattern having a high vertical line width. Therefore, since the positive resist does not shrink due to baking, shrinking of the photoresist pattern including the positive resist having a large area or the positive resist having a long pattern size even in a small area does not substantially occur due to PEB or baking after development. As a result, the photoresist pattern is not deformed, and the pattern shape having high verticality can be maintained.

Embodiment 2 FIG. In the second embodiment, the line width L of the chemically amplified cross-linked negative resist pattern 2a shown in FIG.
The smaller the value of 4, the higher the verticality. When the line width L4 is 5 μm or less, the amount of shrinkage due to baking is small, so that the chemically amplified cross-linked negative resist pattern 2a having higher verticality can be obtained. As a specific example, a third embodiment described later
Even if the baking is performed 5 times, the inclination width of the edge of the formed photoresist pattern 6 is only about 0.1 μm, and the positive resist 5a occupying a large volume hardly undergoes thermal contraction. The pattern 6 is not deformed, and almost perfect verticality is maintained.

As described above, in this embodiment, the line width L4 is 5 μm.
By setting the following, a higher verticality of the photoresist pattern can be obtained.

Embodiment 3 FIG. 2 to 9 are process diagrams showing a method of forming a photoresist pattern according to the third embodiment of the present invention.

First, referring to FIG. 2, an underlayer 1 is prepared, and a chemical amplification composed of a novolak resin as a base resin, a melamine compound acting as a crosslinker, and a photoacid generator is prepared on the underlayer 1. Apply cross-linkable negative resist 2 and
Pre-bake at 10 ° C. for 70 seconds. In this case, the film thickness of the chemically amplified cross-linked negative resist 2 is, eg, about 5 μm.

Next, referring to FIG. 3, as the exposure light 4, i
A stepper for irradiating a line to expose is used, and the exposure light 4 is exposed to the exposure energy 11 through the photomask 3 in which only the outline of the desired photoresist pattern is drawn.
Irradiate at 0 mJ / cm ² .

Next, referring to FIG. 4, PEB is heated to 100 ° C.
For 120 seconds.

Next, referring to FIG. 5, an alkaline aqueous solution (2.38 wt% tetramethylammonium hydroxide).
Chemically amplified cross-linked negative resist 2 developed by using
Are selectively removed to form a chemically amplified cross-linking negative resist pattern 2a having a shape of only a contour portion of a desired photoresist pattern and a shape of a line width having high verticality.
At the same time, the base layer 1 is exposed.

Next, referring to FIG. 6, the exposed underlayer 1
A positive resist 5 is applied on top and prebaked at 85 ° C. for 70 seconds. Also in this case, the film thickness of the positive resist 5 is set to about 5 μm.

Next, referring to FIG. 7, using a stepper, exposure light 4 is exposed through a photomask 3 having a desired pattern size, for example, an exposure energy of 800 mJ.
/ Cm ² irradiation.

Next, referring to FIG. 8, PEB is heated to 120 ° C.
For 90 seconds.

Next, referring to FIG. 9, a positive resist 5a is formed on the exposed underlayer 1 by developing using an alkaline aqueous solution. The photoresist pattern 6 is completed by the chemically amplified cross-linking type negative resist pattern 2a and the positive resist 5a.

Then, as shown in FIG. 10, the completed photoresist pattern 6 is baked at 150 ° C. for 9 days after development.
Perform for 0 seconds. Even if the above baking is performed 5 times, the inclination width of the edge of the formed photoresist pattern 6 is only about 0.1 μm, and the positive resist 5a, which occupies a large volume, does not substantially undergo thermal contraction. Deformation of the photoresist pattern 6 does not occur, and the edge maintains almost perfect verticality.

The photoresist pattern forming method according to the present embodiment described above may be combined with the conventional photoresist pattern forming method. For example, the method of forming a photoresist pattern according to the present embodiment is used for a pattern having a relatively large area or a pattern having a relatively small area and a long pattern size. The photoresist pattern forming method is used. In that case, the photoresist pattern forming method according to the present embodiment and the conventional photoresist pattern forming method may be performed at the same time.

In this embodiment, about 5 μm is used as an example of the film thickness of the positive resist and the chemically amplified cross-linking negative resist, but other film thicknesses may be used. As described in the related art, since the inclination width L3 starts to increase when the thickness of the positive resist exceeds about 2 μm, it is effective for the photoresist pattern requiring the thickness of about 2 μm or more. Is.

As described above, in the present embodiment, it is possible to form a photoresist pattern capable of maintaining a pattern shape having high verticality even if the pattern dimension is large.

[Brief description of drawings]

FIG. 1 is a sectional view showing a photoresist pattern according to a first embodiment of the present invention.

FIG. 2 is a process diagram showing a method for forming a photoresist pattern in a third embodiment of the present invention.

FIG. 3 is a process drawing showing the method for forming a photoresist pattern in the third embodiment of the present invention.

FIG. 4 is a process chart showing a method for forming a photoresist pattern in a third embodiment of the present invention.

FIG. 5 is a process chart showing a method for forming a photoresist pattern in a third embodiment of the present invention.

FIG. 6 is a process chart showing a method for forming a photoresist pattern in a third embodiment of the present invention.

FIG. 7 is a process chart showing the method for forming a photoresist pattern in the third embodiment of the present invention.

FIG. 8 is a process drawing showing the method for forming a photoresist pattern in the third embodiment of the present invention.

FIG. 9 is a process chart showing the method for forming a photoresist pattern in the third embodiment of the present invention.

FIG. 10 is a process diagram of performing post-development baking on the completed photoresist pattern.

FIG. 11 is a process chart showing a method for forming a photoresist pattern when a conventional positive resist is used.

FIG. 12 is a process drawing showing a method for forming a photoresist pattern when a conventional positive resist is used.

FIG. 13 is a process chart showing a method for forming a photoresist pattern when a conventional positive resist is used.

FIG. 14 is a sectional view showing a photoresist pattern when a conventional positive resist is used.

FIG. 15 is a sectional view showing a photoresist pattern when a conventional commercially available positive resist is used.

FIG. 16 is a process drawing showing a method for forming a photoresist pattern when a conventional negative resist is used.

FIG. 17 is a process chart showing a method for forming a photoresist pattern when a conventional negative resist is used.

FIG. 18 is a process chart showing a method for forming a photoresist pattern when a conventional negative resist is used.

FIG. 19 is a process chart showing a method for forming a photoresist pattern when a conventional negative resist is used.

FIG. 20 is a process diagram of performing a post-development bake on a photoresist pattern when using a conventional completed negative resist.

[Explanation of symbols]

1 underlayer, 2 chemically amplified cross-linked negative resist, 2a
Chemically amplified cross-linked negative resist pattern, 3 photomask, 4 exposure light, 5 positive resist, 6 photoresist pattern.

Claims (4)

[Claims] 1. A positive resist pattern formed on an underlayer, and a chemically amplified cross-linking type formed on a side wall portion around the positive resist pattern and having a line width capable of maintaining an edge substantially vertical. A photoresist pattern including a negative resist pattern. 2. The photoresist pattern according to claim 1, wherein the line width is 5 μm or less. 3. A step of preparing an underlayer, a step of applying a chemically amplified crosslinkable negative resist on the underlayer, and a step of selectively removing the chemically amplified crosslinkable negative resist,
A step of leaving a chemically amplified cross-linking negative resist pattern having a line width shape that can maintain the edges substantially vertical and that has a shape of only the outline of the desired photoresist pattern, and is exposed by removing the negative resist. A step of applying a positive resist on the underlying layer, and a step of selectively removing the positive resist outside the contour portion of the shape of the desired photoresist pattern,
A method for forming a photoresist pattern, comprising: 4. The method of forming a photoresist pattern according to claim 3, wherein the line width is 5 μm or less.