JP2008286828A - Pattern forming method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern forming method by which formation of a pattern with a thinner pattern width and a three-dimensional feature can be facilitated. <P>SOLUTION: The pattern forming method is characterized in that a resist pattern is intentionally collapsed by a developing process. By appropriately selecting the interval and thickness of a resist pattern, a fine pattern having a three-dimensional height or a fine pattern having a pattern width equal to or smaller than the resolution of exposure light can be formed in a single lithographic process. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a pattern forming method for forming a fine pattern using a resist.

  A lithography method is known as a method for forming a fine pattern. The lithography method is a technology that generates a pattern consisting of an exposed part and an unexposed part by exposing the surface of a substance coated with a photosensitive substance (resist) in a pattern and developing it. It is.

  Lithographic methods as described above are widely used in fields that require the formation of fine patterns. For example, imprint molds, photomasks, semiconductor devices, optical elements, wiring circuits, recording devices (hard disks, DVDs, etc.) ), Medical test chips (DNA analysis applications, etc.), display panels, and the like.

In the lithography method, as a resist, a method using a negative resist that is cured by exposure / a positive resist that is sparse by exposure is known.
Further, it has been proposed to use a chemically amplified resist as a highly sensitive resist for resolving a finer pattern (see Patent Document 1).

In the lithography method, as exposure light, for example, g-line (wavelength 436 nm), i-line (wavelength 365 nm), KrF excimer laser (wavelength 248 nm), ArF excimer laser (wavelength 193 nm), EUV light, X-ray, electron beam, etc. It is known to use.
It is also known that there is a limit to the pattern width that can be resolved depending on the exposure light used.

  In the lithography method, it is desired to reduce the pattern width that can be formed.

  For example, a method of resolving a pattern width equal to or smaller than the wavelength of exposure light by performing exposure on the resist a plurality of times (double exposure method) has been proposed (see Patent Document 2).

  In addition, it is desired to form fine patterns (for example, step shapes) having different three-dimensional heights using a lithography method.

  For example, in the semiconductor field, a dual damascene structure in which a specific fine three-dimensional structure pattern is formed is proposed, and it is necessary to form a pattern having a step shape (see Patent Document 3).

  For example, there is a report that the number of required steps can be reduced to nearly 1/3 by using nanoimprint technology using a three-stage mold for forming a dual damascene structure. There is a demand for a mold (see Non-Patent Document 1).

On the other hand, in the lithography method, it is known that the drawn resist pattern collapses in the development processing after exposure. At this time, it is known that the resist pattern collapses more easily as the pattern has a higher aspect ratio.
Since the collapse of the resist pattern is synonymous with the destruction of the desired pattern shape, a method has been proposed in which the collapse of the resist pattern is regarded as a problem and the collapse of the resist pattern is suppressed.

For example, a method for suppressing collapse of a resist pattern by forming a cross-linked portion on the resist surface layer has been proposed (see Patent Document 4).
JP-A-6-27673 JP 2006-121119 A JP 2003-303824 A JP 2004-085792 A “Design and fabric of of highly complex topographic nano-imprint template for dualdamascene full 3-D imprinting”, Proc. Of SPIE., Vol.5992, pp.786-794 (2005)

In the lithography method, it is desired to reduce the pattern width that can be formed.
However, there is a resolution limit depending on the wavelength of exposure light used, the resolution of the resist, and the like, and it is difficult to form a fine pattern having a pattern width equal to or less than the resolution limit.

  In the lithography method, it is desired to form fine patterns having different three-dimensional heights.

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a pattern forming method capable of reducing the pattern width and making the pattern three-dimensional.

  The inventors of the present invention diligently studied to reduce the pattern width and make the pattern three-dimensional by actively utilizing the phenomenon that the resist pattern, which has been conventionally regarded as a problem to be avoided, collapses. I found.

  The present invention according to claim 1 is a pattern forming method for forming a fine pattern using a resist, a step of applying a resist to a substrate, a step of exposing the resist and drawing a resist pattern, And a step of developing the resist pattern, wherein the step of performing the developing process is a step of intentionally collapsing the resist pattern by the developing process.

  A second aspect of the present invention is the pattern forming method according to the first aspect, wherein the resist is a negative resist.

  A third aspect of the present invention is the pattern forming method according to the first or second aspect, wherein the aspect ratio of the resist pattern to be collapsed is 3 or more. .

  A fourth aspect of the present invention is the pattern forming method according to any one of the first to third aspects, wherein the step of exposing the resist in a pattern form does not collapse the line width of the resist pattern to be collapsed. The pattern forming method is characterized in that the exposure step is performed so that the line width is narrower than the line width.

  A fifth aspect of the present invention is the pattern forming method according to any one of the first to fourth aspects, wherein the interval between the resist pattern to be collapsed and the resist pattern not to be collapsed is greater than the height of the resist pattern. And a pattern forming method.

  A sixth aspect of the present invention is the pattern forming method according to any one of the first to fourth aspects, wherein an interval between the resist pattern to be collapsed and the resist pattern not to be collapsed is equal to the height of the resist pattern. A pattern forming method characterized by the above.

  A seventh aspect of the present invention is the pattern forming method according to any one of the first to fourth aspects, wherein an interval between the resist pattern to be collapsed and the resist pattern not to be collapsed is smaller than the height of the resist pattern. And a pattern forming method.

  The present invention according to claim 8 is an imprint manufactured by forming a resist pattern using the pattern forming method according to any one of claims 1 to 7 and performing etching using the resist pattern as a mask. It is a mold.

  The present invention according to claim 9 is manufactured by forming a resist pattern using the pattern forming method according to any one of claims 1 to 7 and performing transfer processing molding on the resist pattern. It is an imprint mold.

The pattern forming method of the present invention is characterized in that the resist pattern is intentionally collapsed by a development process.
According to the configuration of the present invention, by deliberately collapsing the resist pattern, the height of the resist pattern in the direction perpendicular to the substrate can be made different between the collapsed resist pattern and the resist pattern that is not collapsed. .
In addition, by intentionally collapsing the resist pattern, the distance between the collapsed resist pattern and the resist pattern that is not collapsed can be made equal to or less than the resolution limit of exposure light.
For this reason, by appropriately selecting the resist pattern interval and the resist pattern height, it is possible to form a fine pattern with a three-dimensional height that is different in a single lithography process or a pattern width less than the resolution limit of exposure light. It is possible to form a fine pattern having

The pattern forming method of the present invention comprises:
Applying a resist to the substrate;
Exposing the resist and drawing a resist pattern;
Developing the resist pattern, and
The step of performing the development processing is a step of intentionally collapsing the resist pattern by the development processing.

  Hereinafter, the phenomenon in which the resist pattern collapses in the development processing step will be described with reference to FIGS.

FIG. 1 shows a pattern forming method using a general resist.
First, the resist layer 12 is formed on the base material 11 (FIG. 1A).
Next, a pattern is drawn on the resist layer 12 with exposure light, development processing is performed, and a resist pattern 13 is formed at a predetermined position on the substrate 11 (FIG. 1B).

  After forming the resist pattern, depending on the application, the substrate 11 may be etched using the patterned resist as a mask (FIG. 1C), and the resist may be peeled off to form the concavo-convex pattern 14 (FIG. 1). (D)).

2 and 3 are cross-sectional views showing that the resist pattern collapses due to the cohesive force of the rinsing liquid existing between the resist patterns in the pattern forming method using the resist.
When pattern formation with a high aspect ratio is performed, the resist pattern (especially a dense pattern) collapses due to the cohesive force of the rinse liquid existing between the resist patterns when the rinse liquid is dried after completion of the development process. A phenomenon occurs (FIG. 2C).
When the rinsing liquid is dried, the surface tension of the rinsing liquid 26 existing between the resist patterns 24 acts on the resist pattern. The cohesive force (pressure) p generated in the liquid 26 sandwiched between the resist patterns 24 is expressed by p = σ / R, where σ is the surface tension of the liquid 26. Here, R is the radius of curvature of the liquid surface. When the pattern is miniaturized, the space d between the resist patterns 24 is narrowed, and the curvature radius R of the liquid surface is accordingly reduced, so that the cohesive force p is increased (FIG. 3).
Therefore, the peeling force F applied to the resist pattern 24 by the cohesive force p is proportional to the aspect ratio. Therefore, when the aspect ratio of the resist pattern is high, the peeling force F exceeds the adhesive force between the resist pattern 24 and the substrate 21. The pattern collapses.
In particular, when the aspect ratio is 3 or more, the phenomenon that the resist pattern collapses is remarkable.

FIG. 4 is a cross-sectional view for explaining the phenomenon of resist pattern collapse.
FIG. 4A shows a state after exposure. Symbols in the figure represent T: pattern width, t: pattern width to be collapsed (T> t), d: pattern interval, and H: pattern height. After the exposure, baking is performed, and development processing using a predetermined developer, rinsing, and drying of the rinse solution are performed. Thereby, as shown in FIG.4 (b), the resist pattern collapsed on the base material 21 is formed.

  As shown in FIG. 4B, the space L between the lines can be expressed by L = d−H. At this time, the space L between the lines is determined by the pattern interval d at the time of pattern design and the film thickness H at the time of resist coating. Therefore, when d≈H (d> H), a fine space L between the lines is produced. I can do it.

  Further, as shown in FIG. 4B, multi-stage patterns having different heights can be formed. At this time, the difference between the first stage (the collapsed resist pattern) and the second stage (the resist pattern that is not collapsed) can be expressed as H−t. Since the step of the multi-step pattern is determined by the pattern width t at the time of pattern design and the film thickness H at the time of resist coating, a resist pattern having an arbitrary step can be designed and formed.

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

<Step of applying resist>
First, a resist is applied on a substrate on which pattern formation is desired.

The substrate may be appropriately selected depending on the application, and is not limited. For example, metal, resin, glass or the like may be used.
Further, when a silicon substrate, a quartz substrate, an SOI substrate, or the like is used as a base material, it can be suitably used for applications such as a photomask and a semiconductor.
Moreover, when using the pattern formation method of this invention for the manufacturing process of the imprint mold used for the optical imprint method, a photomask, etc., it is calculated | required that a board | substrate transmits the used exposure light. For this reason, when using as an imprint mold used for the photoimprint method or a photomask, a quartz substrate having transparency to general exposure light can be suitably used.

  The resist may be appropriately selected according to the exposure light used in the exposure process described later. Further, either a negative resist that is cured by exposure or a positive resist that is sparse by exposure may be used. Further, a chemically amplified resist may be used.

At this time, in the pattern forming method of the present invention, it is preferable to use a negative resist as the resist. When a negative resist is used, after exposure, an undercut is likely to occur between the negative resist and the base substrate, so that the pattern can be suitably collapsed.
In particular, when a chemically amplified negative resist is used, acid deactivation occurs at the base substrate interface, so that an undercut is more likely to occur, and the pattern can be suitably collapsed.

  As a resist coating method, a known thin film forming method may be used as appropriate according to the thickness of the resist to be coated. For example, the film may be formed by spin coating, die coating, spraying, or the like.

<Exposure process>
Next, the resist on the substrate is exposed to draw a resist pattern.

  The exposure light may be appropriately selected according to a desired pattern. For example, g-line, i-line, KrF excimer laser, ArF excimer laser, EUV light, X-ray, particle beam (electron beam, etc.) may be used. Further, a resist pattern may be drawn as appropriate using a known method according to the selected exposure light.

  At this time, in the pattern forming method of the present invention, the resist pattern to be collapsed preferably has an aspect ratio of 3 or more. It is known that the higher the aspect ratio of the resist pattern is, the easier it is to collapse, and the resist pattern can be suitably collapsed by setting it to a high aspect ratio.

Moreover, in the pattern formation method of this invention, it is preferable to expose so that the line width of the resist pattern to collapse may be made thin compared with the line width of the resist pattern not to collapse.
The narrower the line width, the weaker the adhesion between the resist pattern and the base substrate, so that only the resist pattern to be collapsed can be collapsed during the development process. Therefore, by controlling the line width of the resist pattern, it is possible to control the resist pattern to be collapsed and the resist pattern not to be collapsed.

In the pattern forming method of the present invention, it is preferable that the distance between the resist pattern to be collapsed and the resist pattern not to be collapsed is smaller than or equal to the height of the resist pattern.
Since the height of the resist pattern collapsed in the vertical direction of the base material is different from the height of the resist pattern that is not collapsed, the fine pattern that has a three-dimensional height that is different from the collapsed resist pattern and the resist pattern that is not collapsed. Can be formed (FIGS. 2C and 6C).

Moreover, in the pattern formation method of this invention, it is preferable that the space | interval of the resist pattern which does not collapse and the resist pattern which does not collapse is larger than the height of a resist pattern.
If the distance between the resist pattern to be collapsed and the resist pattern not to be collapsed is larger than the height of the resist pattern, the distance between the resist pattern that has collapsed and the resist pattern that is not to collapse is collapsed from the distance between the resist pattern to be collapsed and the resist pattern that is not to be collapsed. The length is obtained by subtracting the height of the resist pattern. For this reason, the interval between the collapsed resist pattern and the resist pattern that is not collapsed can be made equal to or less than the resolution limit of the used exposure light (FIG. 5C).

<Developing process>
Next, the drawn resist pattern is developed to intentionally collapse the resist pattern.

As the development process, a developer corresponding to the selected resist may be used.
In this specification, “development processing” is defined as including both a step of immersing in a developer and a step of rinsing a resist. In the rinsing step, it is sufficient if the developer / impurities can be washed, and for example, pure water, supercritical fluid, or the like may be used.

  At this time, a surfactant may be mixed in the developer / rinse solution. When a surfactant is mixed, the surface tension of the developer / rinse solution is weakened, and the resist pattern is prevented from collapsing. Therefore, by using a surfactant, the surface tension of the developer / rinse solution can be adjusted as appropriate, and the resist pattern to be collapsed and the resist pattern not to be collapsed can be controlled.

The pattern forming method of the present invention is characterized in that the resist pattern is intentionally collapsed by a development process. By intentionally collapsing the resist pattern, the resist pattern height in the vertical direction of the substrate can be made different between the collapsed resist pattern and the resist pattern that is not collapsed.
In addition, by intentionally collapsing the resist pattern, the distance between the collapsed resist pattern and the resist pattern that is not collapsed can be made equal to or less than the resolution limit of exposure light. For this reason, by appropriately selecting the resist pattern interval and the resist pattern height, it is possible to form a fine pattern with a three-dimensional height that is different in a single lithography process or a pattern width less than the resolution limit of exposure light. It is possible to form a fine pattern having

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

After forming a resist pattern using the pattern forming method of the present invention, the resist pattern can be utilized depending on the application.
Hereinafter, as an example, an embodiment in which the pattern forming method of the present invention is used for manufacturing an imprint mold will be described.

<First embodiment>
After forming a resist pattern using the pattern forming method of the present invention, etching is performed using the resist pattern as a mask to form an uneven pattern on the base substrate.
At this time, by appropriately adjusting the etching conditions, it is possible to adjust the processing speed of the resist pattern and the base substrate, and the uneven pattern having different three-dimensional heights according to the formed resist pattern was formed. An imprint mold can be manufactured.

<Second Embodiment>
After forming a resist pattern using the pattern forming method of the present invention, a concavo-convex pattern having different three-dimensional heights corresponding to the formed resist pattern is formed by performing transfer processing molding on the resist pattern. An imprint mold can be manufactured.

By performing transfer processing molding, it is possible to manufacture an imprint mold having a three-dimensional height different according to the formed resist pattern and integrally molded and having high mechanical strength. At this time, as transfer processing molding, a known transfer processing molding method may be appropriately selected and used.
For example, an imprint mold made of metal may be manufactured by performing metal plating on the resist pattern by an electroforming method or the like and peeling the base substrate and the resist pattern. Moreover, you may manufacture the imprint mold which consists of resin by laminating | stacking resin on a resist pattern and peeling a base material and a resist pattern.

  Hereinafter, an example of the implementation of the pattern forming method of the present invention and an example of manufacturing an imprint mold using the pattern forming method of the present invention will be shown. Of course, the present invention is not limited to the following examples.

<Example 1>
FIG. 5 is a cross-sectional view for explaining a resist pattern forming method of a space L between fine lines by controlling the phenomenon of resist collapse.

  First, as shown in FIG. 5A, a negative resist having a thickness of 200 nm was coated on the Si wafer 31.

Next, as shown in FIG. 5B, the electron beam 33 is irradiated to the resist 32 with an electron beam 33 at a dose of 10 μC / cm ² using an electron beam drawing apparatus, and an exposed portion 32A (T = 200 nm, t = 60 nm, d = 220 nm).

  Next, the developing process using the developer was performed for 2 minutes, the rinse was performed for 2 minutes, and the rinse solution was dried. Here, pure water was used as the rinse liquid.

As described above, a resist pattern 34 is formed on the Si wafer 31 as shown in FIG. A space pattern L between fine lines could be obtained.
In addition, a multistage shape having a pattern height of 200 nm and a pattern height of 60 nm with different heights could be obtained.

<Example 2>
FIG. 6 is a cross-sectional view for explaining a method of forming a multistage resist pattern by controlling the phenomenon of resist collapse.

A resist pattern was formed in the same manner as in Example 1.
However, the film thickness of the resist coated on the Si wafer was set to 100 nm, and the dimension of the exposed portion by the electron beam was set to T = 100 nm, t = 50 nm, and d = 100 nm.

  As described above, as shown in FIG. 6C, a multistage resist pattern was formed on the Si wafer.

<Example 3>
FIG. 7 is a cross-sectional view for explaining a nanoimprint mold manufacturing method using the pattern forming method of the present invention.

Using the multi-stage resist pattern (FIG. 7A) formed in Example 2 as a mask, anisotropic dry etching of Si was performed using an ICP dry etching apparatus to form a Si pattern having a depth of 200 nm (FIG. 7). 7 (b)).
At this time, the conditions for Si anisotropic etching were C ₄ F ₈ flow rate 30 sccm, O ₂ flow rate 30 sccm, Ar flow rate 50 sccm, pressure 2 Pa, ICP power 500 W, and RIE power 130 W.

Next, the first resist (collapsed resist pattern) was peeled off by O ₂ plasma ashing (conditions: O ₂ flow rate 500 sccm, pressure 30 Pa, RF power 1000 W) (FIG. 7C).

  Next, anisotropic dry etching of Si was performed again to form Si multi-step patterns 35 having different heights (FIG. 7D).

  From the above, an imprint mold having multi-stage patterns with different heights could be manufactured.

  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) It can be expected to be suitably used in manufacturing processes such as a plate and a light guide plate.

It is sectional process drawing which shows the general resist pattern formation method. It is a figure explaining that a resist pattern collapses. It is a figure explaining that a resist pattern collapses. It is sectional process drawing which shows an example of implementation of the pattern formation method of this invention. It is sectional process drawing which shows an example of implementation of the pattern formation method of this invention. It is sectional process drawing which shows an example of implementation of the pattern formation method of this invention. It is sectional process drawing which shows an example of implementation of the manufacturing method of the imprint mold using the pattern formation method of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Base material 12 ... Resist 13 ... Resist pattern 14 ... Concavity and convexity pattern 21 ... Base material 22 ... Resist 22A ... Exposure part 23 ... Exposure light 24 ... Resist pattern 25 ... Collapsed resist pattern 26 ... Rinse solution 31 ... Si wafer 32 ... Negative resist 32A ... Exposure part 33 ... Exposure light 34 ... Collapsed resist pattern 35 ... Multi-stage pattern

Claims (9)

In a pattern forming method for forming a fine pattern using a resist,
Applying a resist to the substrate;
Exposing the resist and drawing a resist pattern;
Developing the resist pattern, and
The pattern forming method, wherein the developing process is a process of intentionally collapsing a resist pattern by the developing process. The pattern forming method according to claim 1,
A pattern forming method, wherein a negative resist is used as the resist. The pattern forming method according to claim 1, wherein:
A pattern forming method, wherein an aspect ratio of a resist pattern to be collapsed is 3 or more. A pattern forming method according to any one of claims 1 to 3,
The pattern forming method characterized in that the step of exposing the resist in a pattern is a step of exposing the resist pattern so that the line width of the resist pattern to be collapsed is smaller than the line width of the resist pattern not to be collapsed. A pattern forming method according to any one of claims 1 to 4,
A pattern forming method, wherein a distance between a resist pattern to be collapsed and a resist pattern not to be collapsed is larger than a height of the resist pattern. A pattern forming method according to any one of claims 1 to 4,
A pattern forming method, wherein an interval between a resist pattern to be collapsed and a resist pattern not to be collapsed is equal to a height of the resist pattern. A pattern forming method according to any one of claims 1 to 4,
A pattern forming method, wherein a distance between a resist pattern to be collapsed and a resist pattern not to be collapsed is smaller than a height of the resist pattern.   An imprint mold manufactured by forming a resist pattern using the pattern forming method according to claim 1 and performing etching using the resist pattern as a mask.   The imprint mold manufactured by forming a resist pattern using the pattern formation method in any one of Claim 1 to 7, and performing transfer processing shaping | molding with respect to this resist pattern.

Images