JP5343345B2 - Pattern formation method, imprint mold, photomask - Google Patents

Description

  The present invention relates to a method for forming a fine three-dimensional structure pattern, and an imprint mold / photomask manufactured using the pattern forming method.

  Structures in which a specific fine three-dimensional structure pattern (for example, a multi-stepped shape) is formed on a base material (for example, glass, resin, metal, silicon, etc.) are widely used. For example, semiconductor devices, optical elements, wiring circuits, recording devices (such as hard disks and DVDs), medical testing chips (such as DNA analysis applications), display panels, and microchannels can be used.

In addition, it is known that a method for forming a fine three-dimensional structure pattern is used for manufacturing an imprint mold for transferring a fine three-dimensional structure pattern.
In addition, it is known that a Levenson-type photomask used as a phase shift mask for resolving a pattern with a small line width forms a step-shaped pattern on a transparent substrate.

  In recent years, such applications have greatly expanded, and demands for finer patterns and structures with a larger number of stages are increasing.

  For example, in the semiconductor field, a dual damascene structure in which a specific fine three-dimensional structure pattern is formed has been proposed. At this time, in a normal dual damascene structure forming step, it is known to form a resist pattern for each step to be formed.

  As a method for forming a dual damascene structure, for example, a method is proposed in which the first layer step is coated with BARC (Bottom Anti Reflection Coating) or the like to eliminate the step and then pattern formation is performed again (see Patent Document 1). ).

  As a method for forming a dual damascene structure, for example, a method using a nanoimprint technique using a three-stage mold is known (see Non-Patent Document 1). Thereby, since there is a report that the number of necessary steps can be reduced to nearly 1/3, there is an increasing demand for an imprint mold having a multistage structure.

  Further, as a method for manufacturing the above-described specific fine three-dimensional structure pattern (for example, a multi-step staircase shape), a method of forming a staircase structure using charged particle beam lithography is known.

  For example, a method of forming a resist stepwise by controlling an electron beam dose in electron beam lithography has been proposed (see Non-Patent Document 2).

  In the lithography method, it is known that a drawn resist pattern collapses in a development process after exposure. At this time, it is known that the resist pattern collapses more easily as the pattern has a higher aspect ratio.

For example, a method for suppressing collapse of a resist pattern by forming a crosslinked portion on the resist surface layer has been proposed (see Patent Document 2).
JP 2003-303824 A JP 2004-085792 A Proc. of SPIE. , Vol. 5992, pp. 786-794 (2005) Jpn. J. et al. Appl. Phys. , Vol. 39, pp. 6831-6835 (2000)

  In the formation of a fine three-dimensional structure pattern, it is known to perform resist patterning a plurality of times in accordance with the three-dimensional structure pattern.

However, it is difficult to newly perform resist patterning on a substrate that already has a step because of the following reasons. It goes without saying that the greater the depth of the step, the higher the difficulty.
1. When a resist is coated on a stepped substrate, if the thickness of the resist film is equal to or less than the step, the resist film on the convex portion becomes thin and a flat resist film cannot be obtained. . For this reason, it is difficult to obtain a desired resist pattern (FIG. 2).
2. When the resist film is sufficiently thick so that the resist film becomes flat, the aspect ratio of the formed resist pattern increases according to the thickness of the resist film, so that the resist pattern collapses. For this reason, it is difficult to obtain a desired resist pattern (FIG. 3).

  Therefore, the present invention has been made to solve the above-described problem, and an object thereof is to provide a pattern forming method suitable for forming a fine three-dimensional structure pattern having a plurality of steps.

The present invention according to claim 1 is a pattern forming method for forming a fine three-dimensional structure pattern, wherein a hard mask layer having the same size as the substrate is formed on the substrate, and a resist is applied to the hard mask layer. And a step of forming a hard mask pattern having a size smaller than that of the hard mask layer by resist development and etching of the hard mask layer, and resist coating and resist development on the hard mask pattern formed from the hard mask layer And a step of forming a step in the hard mask pattern by etching the hard mask pattern, and anisotropic etching is performed on the substrate using the hard mask pattern having the step as an etching mask to form a two-step pattern on the substrate. And a step of forming It is that the pattern forming method.

  A second aspect of the present invention is the pattern forming method according to the first aspect, wherein the three-dimensional structural pattern has a dimension width of 100 nm or less.

  According to a third aspect of the present invention, there is provided the pattern forming method according to the first or second aspect, wherein the substrate is a quartz substrate and the hard mask layer is a layer made of chromium. And a pattern forming method.

  A fourth aspect of the present invention is an imprint mold manufactured by using the pattern forming method according to any one of the first to third aspects.

  A fifth aspect of the present invention is a photomask manufactured by using the pattern forming method according to any one of the first to third aspects.

The pattern forming method of the present invention is characterized in that a hard mask layer is formed, a step is provided in the hard mask layer, and anisotropic etching is performed on the substrate using the hard mask layer as an etching mask.
According to the configuration of the present invention, when a desired three-dimensional structure pattern is formed on a substrate, the hard mask layer is a material having a high etching selectivity with respect to the substrate, and therefore, a hard mask corresponding to the three-dimensional structure pattern to be formed. The depth of the layer step can be made smaller than the desired three-dimensional structure pattern.
For this reason, when patterning for forming a step, the depth of the step to be formed can be reduced, and the occurrence of resist pattern collapse can be suppressed. Therefore, it is possible to suitably form a fine three-dimensional structure pattern having a plurality of steps.

Hereinafter, an example of a conventional pattern forming method having a typical multistage structure will be described.
First, a resist is coated on a substrate provided with a hard mask layer (FIG. 1A), and the resist is patterned (FIG. 1B).
Next, the hard mask layer is etched using the resist pattern as a mask, and the substrate is etched using the hard mask layer as a mask (FIG. 1C).
Next, washing is performed to produce a first layer pattern (FIG. 1D).
Next, a resist is coated again on the substrate on which the first layer pattern is formed (FIG. 1E), and the resist is patterned (FIG. 1F).
Next, the hard mask layer is etched using the resist pattern as a mask, and the substrate is etched using the hard mask layer as a mask (FIG. 1G).
Next, it is washed to produce a second layer pattern (FIG. 1 (h)).

In the pattern forming method of the conventional typical multi-stage structure, when patterning the second layer step, if the resist thickness is equal to or less than the first layer step, a resist corresponding to the corner of the convex portion of the pattern is formed. It becomes thin, a flat resist layer cannot be obtained, and it is difficult to obtain a desired resist pattern, which is unsuitable for forming a fine three-dimensional structure pattern (FIG. 2).
In addition, when the resist is thickened so as to fill the first step (FIG. 3A), the resist film has a thick film thickness with respect to the desired pattern width, so the aspect ratio of the resist pattern becomes large. The resist pattern collapses and it is difficult to obtain a desired resist pattern, which is unsuitable for forming a fine three-dimensional structure pattern (FIG. 3B).

The pattern forming method of the present invention is made in order to solve the problems of the conventional typical multi-stage pattern forming method as described above.
The pattern forming method of the present invention is characterized in that a hard mask layer is formed, a step is provided in the hard mask layer, and anisotropic etching is performed on the substrate using the hard mask layer as an etching mask.
According to the configuration of the present invention, when a desired three-dimensional structure pattern is formed on a substrate, the hard mask layer is a material having a high etching selectivity with respect to the substrate, and therefore, a hard mask corresponding to the three-dimensional structure pattern to be formed. The depth of the layer step can be made smaller than the desired three-dimensional structure pattern.
For this reason, when patterning for forming a step, the depth of the step to be formed can be reduced, and the occurrence of resist pattern collapse can be suppressed. Therefore, it is possible to suitably form a fine three-dimensional structure pattern having a plurality of steps.

  Hereinafter, the pattern forming method of the present invention will be described.

<Process for forming a hard mask layer on a substrate>
First, a hard mask layer is formed on a substrate. As a method for forming the hard mask layer, a known thin film forming method may be used as appropriate depending on the material selected for the hard mask layer. For example, a sputtering method or the like may be used.

  You may select a board | substrate suitably according to a use. For example, a silicon substrate, a quartz substrate, a sapphire substrate, an SOI substrate, or the like may be used.

  The hard mask layer may be made of a material having a high etching selectivity in a <process for performing anisotropic etching> to be described later with respect to the selected substrate.

  The substrate is preferably a quartz substrate, and the hard mask layer is preferably a layer made of chromium. The quartz substrate is transmissive to general exposure light, particularly when the pattern forming method of the present invention is used for manufacturing processes such as an imprint mold used in the photoimprint method and a photomask. Is preferred. At this time, by using a layer made of chromium as the hard mask layer for the quartz substrate, the etching selectivity of the hard mask layer to the substrate can be set high under general etching conditions.

<Step of forming a step in the hard mask layer>
Next, a step is formed in the hard mask layer. As a method for forming the step of the hard mask layer, a lithography method using a resist is used. For example, a step may be formed on the hard mask layer by forming a resist film on the hard mask layer, patterning the resist film to form a resist pattern, and performing etching using the resist pattern as a mask. good.
Since the hard mask layer is a material having a high etching selectivity with respect to the substrate, the step of the hard mask layer corresponding to the three-dimensional structure pattern to be formed can be made smaller than the desired three-dimensional structure pattern. For this reason, resist pattern collapse can be suppressed.

  At this time, the step formed on the hard mask layer is not limited to two steps, and may have more steps. By making the steps of the hard mask layer multi-stage, the three-dimensional structure pattern formed on the substrate can be a multi-stage structure pattern of two or more stages.

  Further, the depth of the three-dimensional structure pattern of the substrate finally formed can be controlled by the depth of the step in the hard mask layer. The depth of the finally formed three-dimensional structure pattern of the substrate is determined by the step depth of the hard mask layer and the etching selectivity of the hard mask layer to the substrate.

<Process for performing anisotropic etching on substrate>
Next, anisotropic etching is performed from the side where the hard mask layer having a step is formed. As the etching, a known etching method may be used as appropriate, and for example, dry etching, wet etching, or the like may be performed. Etching conditions may be adjusted as appropriate according to the hard mask layer / substrate used.

In addition, the pattern forming method of the present invention shows a special effect when the dimension width of the three-dimensional structure pattern includes 100 nm or less.
In general, the aspect ratio of a resist pattern is represented by a ratio of a resist pattern height to a resist pattern dimension width. For this reason, even if the thickness of the resist film is the same, the resist pattern has a higher aspect ratio as the resist pattern dimension width is smaller. It is also known that the resist pattern collapse occurs as the resist pattern has a higher aspect ratio. Therefore, in particular, when the resist pattern dimension width is 100 nm or less, the aspect ratio of the resist pattern becomes high, so the problem of resist pattern collapse cannot be ignored.
When the dimension width of the three-dimensional structure pattern includes a pattern width of 100 nm or less, the corresponding resist pattern needs to have a dimension width of 100 nm or less. In particular, when a three-dimensional structure pattern having a plurality of steps is formed, the conventional method uses a resist in order to form a flat resist film in the formation of the three-dimensional structure pattern after the second layer step. It was necessary to apply a thick film. For this reason, when the three-dimensional structure pattern after the second layer step has a dimension width of 100 nm or less, the aspect ratio of the resist pattern cannot be kept low, and the occurrence of the resist pattern collapse is remarkable.
According to the present invention, when a desired three-dimensional structure pattern is formed on a substrate, the hard mask layer is a material having a high etching selectivity with respect to the substrate, and therefore the hard mask layer corresponding to the three-dimensional structure pattern to be formed is formed. The step can be made smaller than the desired three-dimensional structure pattern. For this reason, even in a fine three-dimensional structure pattern, even if the minimum dimension width is a multi-stage pattern with a size of 100 nm or less, the aspect ratio of the resist pattern to be formed can be lowered, and the occurrence of resist pattern collapse is suppressed. In addition, a three-dimensional structure pattern can be formed.

  From the above, the pattern forming method of the present invention can be carried out.

  Hereinafter, the pattern forming method of the present invention will be described with reference to FIG. 4 while giving an example in the case of producing an optical imprint mold. As a matter of course, the pattern forming method of the present invention is not limited to the following examples.

  First, as shown in FIG. 4A, a positive resist having a thickness of 200 nm was coated on a quartz substrate having a Cr film having a thickness of 15 nm as a hard mask layer.

Next, as shown in FIG. 4B, after the electron beam is irradiated to the resist at a dose of 100 μC / cm ² with an electron beam lithography apparatus, development processing using a developer, rinsing, and rinsing liquid are performed. Was dried. Here, pure water was used as the rinse liquid.

Next, the Cr film was etched by dry etching using an ICP dry etching apparatus on the developed mold. At this time, Cr etching conditions were Cl ₂ flow rate 40 sccm, O ₂ flow rate 10 sccm, He flow rate 80 sccm, pressure 30 Pa, ICP power 300 W, and RIE power 30 W.

Next, the resist was stripped by O ₂ plasma ashing (conditions: O ₂ flow rate 500 sccm, pressure 30 Pa, RF power 1000 W) (FIG. 4C).
From the above, the first step was formed in the Cr film.

  Next, as shown in FIG. 4D, a positive resist having a thickness of 200 nm was coated on a quartz substrate provided with a Cr film having a step.

Next, the electron beam was irradiated to the resist film with an electron beam at a dose of 100 μC / cm ² using an electron beam drawing apparatus.

  Next, development processing using a developing solution, rinsing, and drying of the rinsing solution were performed to form a resist pattern corresponding to the second layer step on the step of the Cr film (FIG. 4E). At this time, pure water was used as the rinse liquid.

Next, the Cr film was etched by dry etching using an ICP dry etching apparatus to produce a step in the Cr film (FIG. 4F).
At this time, Cr etching conditions were Cl ₂ flow rate 40 sccm, O ₂ flow rate 10 sccm, He flow rate 80 sccm, pressure 30 Pa, ICP power 300 W, and RIE power 30 W.
Further, the Cr film was dry-etched to a depth of 6 nm.

Next, the quartz substrate was etched by dry etching using an ICP dry etching apparatus to produce a first-layer quartz step (FIG. 4G), and a second-layer quartz step was produced.
At this time, the etching conditions for quartz were C ₄ F ₈ flow rate 10 sccm, O ₂ flow rate 10 to 25 sccm, Ar flow rate 75 sccm, pressure 2 Pa, ICP power 200 W, and RIE power 550 W.
Further, the total depth was 500 nm, and the first layer was dry-etched with quartz up to 300 nm.

Next, wet peeling cleaning of the remaining Cr layer was performed (FIG. 4 (h)).
As mentioned above, the imprint mold for optical imprints was able to be manufactured using the pattern formation method of this invention.

  The pattern forming method of the present invention is expected to be used in a wide range of fields where a fine pattern is required. For example, imprint molds, photomasks, semiconductor devices, optical elements, wiring circuits (such as dual damascene wiring circuits), recording devices (such as hard disks and DVDs), medical testing chips (such as DNA analysis applications), displays (diffusion) Plate, light guide plate, etc.), microchannels, etc., can be expected to be used suitably.

It is a figure which shows an example in the conventional pattern formation method. It is a figure which shows the problem in the conventional pattern formation method. It is a figure which shows the problem in the conventional pattern formation method. It is a figure which shows an example of implementation of the pattern formation method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Quartz substrate 12 ... Cr layer 13 ... Resist film 14 ... Resist pattern 15 ... Cr pattern 16 ... Quartz pattern (one step)
17 ... Quartz pattern (two steps)
18 ... Collapsed resist pattern 19 ... Stepped Cr pattern

Claims (5)

In a pattern forming method for forming a fine three-dimensional structure pattern,
Forming a hard mask layer having the same size as the substrate on the substrate;
The etching of the resist coating and the resist developing and the hard mask layer to the hard mask layer, forming a small hard mask pattern of said hard mask layer than the size,
Forming a step in the hard mask pattern by applying a resist to the hard mask pattern formed from the hard mask layer, developing the resist, and etching the hard mask pattern;
Performing anisotropic etching on the substrate using the hard mask pattern having the step as an etching mask, and forming a two-step pattern on the substrate;
A pattern forming method comprising: The pattern forming method according to claim 1,
What is claimed is: 1. A pattern forming method comprising: a three-dimensional structure pattern having a dimension width of 100 nm or less. The pattern forming method according to claim 1, wherein:
The substrate is a quartz substrate,
The pattern forming method, wherein the hard mask layer is a layer made of chromium.   The imprint mold manufactured using the pattern formation method in any one of Claim 1 to 3. A photomask manufactured using the pattern forming method according to claim 1.

Images