JP4322482B2 - Method for forming fine resist pattern and method for manufacturing semiconductor device - Google Patents

Description

[0001]
[Technical field to which the invention belongs]
The present invention relates to a method for manufacturing a semiconductor device, and more particularly to a method for forming a fine resist pattern having a high aspect ratio.
[0002]
[Prior art]
In recent years, semiconductor devices have become increasingly highly integrated, and along with this, miniaturization of resist patterns has been progressing rapidly. Further, when patterning the base film, resistance to dry etching (resistance to CF gas) is required for the resist pattern as usual. For this reason, a resist thickness on the order of several hundred nm is required in the single-layer resist process.
[0003]
Hereinafter, a conventional resist pattern forming method will be described with reference to FIGS.
9 to 11 are cross-sectional views for explaining a conventional method for forming a fine resist pattern, and FIGS. 12 to 14 are cross-sectional views for explaining a conventional method for forming a fine resist pattern having a high aspect ratio. FIG.
First, as shown in FIG. 9, a resist 12 is formed by spin-coating a resist on a base film 11 finally patterned by etching.
Next, as shown in FIG. 10, the resist 12 is irradiated with exposure light 13 to form an exposed portion 12 </ b> A in the resist 12. Then, baking is performed. As a result, a chemical amplification reaction occurs in the exposed portion 12A.
Next, development processing using a predetermined developing solution, rinsing, and drying of the rinsing solution are performed. As a result, a resist pattern 14 is formed on the base film 11 as shown in FIG.
[0004]
As described above, the resist pattern etching resistance is required to have an appropriate performance with respect to the desired miniaturization of the resist pattern. For this reason, the aspect ratio of the resist pattern required after the development processing tends to increase more and more. In the 70 nm node generation, when the required resist film thickness is, for example, 300 nm, the aspect ratio exceeds 4.
Conventionally, as shown in FIGS. 12 to 14, a high aspect ratio resist pattern has been formed in the same manner as the forming method shown in FIGS. 9 to 11.
[0005]
[Problems to be solved by the invention]
However, when a line resist pattern having an aspect ratio exceeding 4 is formed, as shown in FIG. 14, when the rinsing liquid is dried after completion of the development processing step, the cohesive force due to the capillary force of the rinsing liquid existing between the resist patterns. Therefore, there is a problem that the line resist pattern (particularly a dense pattern) collapses.
FIG. 15 is a cross-sectional view for explaining the cohesive force of the rinsing liquid existing between the resist patterns.
As shown in FIG. 15, when the rinsing liquid is dried, the surface tension of the rinsing liquid 16 existing between the resists 12 acts on the line resist pattern. The cohesive force (pressure) p generated in the liquid 16 sandwiched between the resists 12 is represented by p = σ / R, where σ is the surface tension of the liquid 16. Here, R is the radius of curvature of the liquid surface.
When the dense line pattern is miniaturized, the space d between the lines (resist 12) is narrowed, and the curvature radius R of the liquid surface is accordingly reduced, so that the cohesive force p is increased. The peeling force F applied to the resist 12 by the cohesive force p is proportional to the aspect ratio. Therefore, when the aspect ratio of the resist pattern is 4 or more, the peeling force F exceeds the adhesive force between the resist 12 and the substrate (underlayer film 11). End up. For this reason, as described above, the resist pattern 15 collapses.
[0006]
In order to suppress the cohesive force of the rinsing liquid, use of a rinsing liquid having a small surface tension or a supercritical drying method for eliminating the interface between the liquid phase and the gas phase has been proposed. However, these have not yet been adopted in actual processes because of the problem of treating organic waste liquid and the need to introduce large-scale equipment.
[0007]
Therefore, in order to prevent the resist pattern from collapsing, the cohesive force generated between the resists must be reduced or a physical force larger than the cohesive force is required.
[0008]
The present invention has been made to solve the above-described conventional problems, and aims to prevent resist collapse caused by the cohesive force of liquid existing between resists and to form a fine resist pattern with a high aspect ratio. To do.
Another object of the present invention is to form a fine pattern using a high aspect ratio fine resist pattern as a mask.
[0009]
[Means for solving the problems]
The method for forming a fine resist pattern according to the invention of claim 1 includes a step of forming a resist containing a polyhydroxystyrene-based polymer on a base film,
Irradiating the resist with exposure light;
Irradiating the resist with light having a wavelength of 180 nm to 200 nm by an energy amount of 10 to 30 mJ / cm ² to form a crosslinked part on the surface layer of the resist; and
A development step for carrying out a development treatment after completion of the cross-linking portion forming step;
A step of removing the cross-linked portion after completion of the development processing;
It is characterized by including.
[0013]
The method for forming a fine resist pattern according to the invention of claim 2 is the formation method of claim 1 ,
The cross-linked portion is removed by oxygen-based plasma treatment.
[0014]
The method for forming a fine resist pattern according to the invention of claim 3 is the formation method of claim 1 or 2 ,
The development step includes
A step of rinsing with a rinsing liquid after completion of the development processing;
Drying the rinse solution;
It is characterized by including.
[0015]
According to a fourth aspect of the present invention, there is provided a method for manufacturing a semiconductor device, comprising: using a fine resist pattern formed by the formation method according to any one of the first to third aspects as a mask; An etching process is included.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and the description thereof may be simplified or omitted.
[0017]
Embodiment 1 FIG.
1 to 6 are cross-sectional views for explaining a method for forming a high aspect ratio fine resist pattern according to the first embodiment of the present invention.
First, as shown in FIG. 1, a resist 2 is spin-coated on the base film 1 so as to have a film thickness of about 300 nm. Here, the resist 2 has strong absorption with respect to a wavelength in a specific region, and is, for example, a chemically amplified resist containing a polyhydroxystyrene-based polymer.
And after apply | coating the resist 2, it heat-processes for 60 second at the temperature of about 100 degreeC.
[0018]
Next, as shown in FIG. 2, an exposure process of irradiating the resist 2 with the electron beam 3 is performed to form an exposed portion 2 </ b> A in the resist 2. Thereafter, heat treatment is performed at a temperature of about 110 ° C. for 90 seconds. Thereby, a chemical amplification reaction occurs in the exposed portion 2A of the resist 2. The exposure process was performed using a variable rectangular electron beam exposure apparatus. The exposure process is not limited to the electron beam exposure, and may be light exposure that irradiates exposure light.
[0019]
Next, as shown in FIG. 3, light 6 having a wavelength region that has a high absorption rate with respect to the resist 2 and does not cut the main chain of the polymer contained in the resist 2 is applied to the surface of the resist 2 with a predetermined amount of energy. Irradiate only. By this light irradiation, a photocrosslinking reaction occurs in the exposed portion 2A and the unexposed portion of the resist 2, and a crosslinked portion 7 that is insoluble in an alkali developer (described later) is formed on the outermost layer of the resist 2.
Here, for example, when a chemically amplified resist containing a polyhydroxystyrene-based polymer is used as the resist 2, the light 6 having a wavelength of 180 nm to 200 nm is irradiated by an energy amount of 10 to 30 mJ / cm ² . The wavelength and energy amount of the irradiation light 6 will be described below.
First, the wavelength of irradiation light will be described.
FIG. 7 is a diagram showing the transmittance with respect to the wavelength of a resist containing a polyhydroxystyrene-based polymer. That is, it is a diagram showing the relationship between the wavelength of irradiation light and the transmittance of resist. The resist film thickness is 100 nm.
As shown in FIG. 7, there is a strong absorption band in the vicinity of a wavelength of 190 nm. In this absorption band, the transmittance of the resist is 1% or less. This is absorption of light by π electrons of the benzene ring present in the polymer contained in the resist, and the absorption is very high in the wavelength range of 180 nm to 200 nm. Therefore, by irradiating the light 6 having a wavelength of 180 nm to 200 nm that can obtain this high absorption, the irradiated light 6 can act only on the outermost surface of the resist, and only a depth of several nm upper layer of the resist can be crosslinked. It becomes. The light 6 in this wavelength region does not cut the polymer main chain contained in the resist 2.
Next, the energy of irradiation light will be described.
FIG. 8 is a diagram showing a sensitivity curve with respect to light energy of a resist containing a polyhydroxystyrene-based polymer. Specifically, the relationship between the irradiation energy of the irradiation light and the change in the resist film thickness after the development processing in the case where irradiation with light 6, baking, and development processing is performed after resist coating is shown. As shown in FIG. 8, the resist film thickness is not reduced in the irradiation energy region of 10 to 30 mJ / cm ² . That is, by irradiating light 6 in this energy region, the resist is insoluble in alkali. This indicates that a cross-linking reaction between polymers occurs in this energy region. Therefore, it is possible to cause a crosslinking reaction in the resist by irradiating the light 6 with an energy amount of 10 to 30 mJ / cm ² .
[0020]
Next, as shown in FIG. 4, wet development is performed for 60 seconds using a commonly used alkaline developer (for example, a 2.38% tetramethylammonium hydroxide aqueous solution). In this development processing, since the cross-linked portion 7 formed on the outermost layer of the resist 2 is weakly cross-linked, the developer penetrates into the resist 2 and an alkali dissolution contrast is obtained. And after rinsing using a rinse liquid, a rinse liquid is dried.
[0021]
Finally, as shown in FIG. 5, plasma treatment using oxygen or a mixed gas plasma containing oxygen (hereinafter referred to as “oxygen-based plasma”) 8 is performed to form a bridge portion 7 formed on the outermost layer of the resist 2. Remove. As a result, a fine resist pattern 4 having a high aspect ratio is formed on the base film 1 as shown in FIG. Here, the plasma treatment was performed using a single wafer ashing apparatus.
[0022]
As described above, in the first embodiment, the surface of the resist 2 is irradiated with light 6 before the development process, so that the cross-linking portion 7 is formed on the outermost layer of the resist 2 and then the development process is performed.
Therefore, the resist pattern after the development processing is bridged by the bridge portion 7 whose uppermost layer is insoluble in the alkaline developer. Therefore, the exposed portion 2A is removed by the development process, but the crosslinked portion 7 remains without being removed. For this reason, when the rinse solution is dried after the development process, a physical force larger than the cohesive force of the rinse solution is obtained, and the resist pattern can be prevented from collapsing. That is, a fine resist pattern with a high aspect ratio can be formed by the method according to the first embodiment. In addition, a fine pattern can be formed by etching the base film 1 using this high aspect ratio fine resist pattern.
In the first embodiment, the polymer contained in the resist 2 is irradiated with the irradiation light 6 in the wavelength region having a high absorption rate. Therefore, it is possible to cause a crosslinking reaction only in the outermost layer of the resist 2. For this reason, the crosslinking rate of the resist 2 can be kept low, and the alkaline developing aqueous solution can permeate into the resist 2 through the crosslinking portion 7 during the development processing, and an alkali dissolution contrast is obtained. Further, since the cross-linked portion 7 of the resist outermost layer has a weak cross-linked structure, it can be easily removed by a short-time oxygen-based plasma treatment performed after development.
The fine resist pattern forming method according to the first embodiment can be performed using an existing semiconductor manufacturing apparatus. Therefore, since no new equipment introduction cost is generated, an increase in the manufacturing cost of the semiconductor device can be suppressed.
[0023]
In the first embodiment, the plasma processing is performed by the single wafer ashing apparatus, but may be performed by the single wafer dry etching apparatus. In this case, the plasma treatment and the dry etching of the base film 1 performed following the plasma treatment can be performed continuously in the same chamber, and the throughput can be improved.
[0024]
【The invention's effect】
According to the present invention, resist collapse due to the cohesive force of liquid existing between resists can be prevented, and a fine resist pattern having a high aspect ratio can be formed.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view for explaining a fine resist pattern forming method according to a first embodiment of the present invention (No. 1).
FIG. 2 is a cross-sectional view for explaining the fine resist pattern forming method according to the first embodiment of the present invention (No. 2).
FIG. 3 is a cross-sectional view for explaining the fine resist pattern forming method according to the first embodiment of the present invention (No. 3).
FIG. 4 is a cross-sectional view for explaining the fine resist pattern forming method according to the first embodiment of the present invention (No. 4).
FIG. 5 is a cross-sectional view for explaining the fine resist pattern forming method according to the first embodiment of the present invention (No. 5).
FIG. 6 is a cross-sectional view for explaining the fine resist pattern forming method according to the first embodiment of the present invention (# 6).
FIG. 7 is a diagram showing transmittance with respect to wavelength of a resist.
FIG. 8 is a diagram showing a sensitivity curve with respect to light energy of a resist.
FIG. 9 is a cross-sectional view for explaining a conventional resist pattern forming method (No. 1).
FIG. 10 is a cross-sectional view for explaining a conventional resist pattern forming method (No. 2).
FIG. 11 is a cross-sectional view for explaining a conventional resist pattern forming method (No. 3).
FIG. 12 is a cross-sectional view for explaining a conventional resist pattern forming method (No. 4).
FIG. 13 is a cross-sectional view for explaining a conventional resist pattern forming method (No. 5).
FIG. 14 is a cross-sectional view for explaining a conventional resist pattern forming method (No. 6).
FIG. 15 is a cross-sectional view showing the surface tension of a rinsing liquid existing between resist patterns.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Base film 2 Resist 2A Exposure part 3 Electron beam, exposure light 4 Fine resist pattern 6 Irradiation light 7 Bridge | crosslinking part 8 Oxygen type plasma

Claims (4)

Forming a resist containing a polyhydroxystyrene-based polymer on the base film;
Performing an exposure process on the resist;
Irradiating the resist with light having a wavelength of 180 nm to 200 nm by an energy amount of 10 to 30 mJ / cm ² to form a crosslinked part on the surface layer of the resist; and
A development step for carrying out a development treatment after completion of the cross-linking portion forming step;
A step of removing the cross-linked portion after completion of the development step;
A method for forming a fine resist pattern, comprising:   The forming method according to claim 1,
  A method for forming a fine resist pattern, wherein the cross-linked portion is removed by oxygen-based plasma treatment.   In the formation method of Claim 1 or 2,
  The development step includes
  A step of rinsing with a rinsing liquid after completion of the development processing;
  Drying the rinse solution;
  A method for forming a fine resist pattern, comprising:   4. A method of manufacturing a semiconductor device, comprising: a step of dry etching a base film with a fluorocarbon plasma using a fine resist pattern formed by the formation method according to claim 1 as a mask. Method.

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