JP5359430B2 - Pattern forming method, imprint mold and photomask - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pattern forming method suitable for forming a fine three-dimensional structure pattern having a plurality of level differences. <P>SOLUTION: The pattern forming method for forming a three-dimensional structure pattern includes: a process for forming a hard mask layer on a substrate; a process for applying first anisotropic etching on the substrate by using the hard mask layer as an etching mask; a process for forming a second hard mask layer on the substrate which already has a step and further has a step by the first anisotropic etching; and a process for applying second anisotropic etching on the substrate by using the second hard mask layer as an etching mask. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

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

  Structures in which a specific fine three-dimensional structure pattern is formed on a substrate are widely used. For example, a semiconductor device, an optical element, a wiring circuit, a recording device, a medical test chip, a display panel, a microchannel, and the like can be given.

  In recent years, there has been an increasing demand for finer patterns and structures with more stages. For example, in the semiconductor field, a dual damascene structure in which a specific fine three-dimensional structure pattern is formed has been proposed.

  As a method for forming a dual damascene structure, a method using an imprint technique is known. In the imprint method, it is possible to transfer a three-dimensional structure pattern formed on a mold, so it is also possible to transfer a multi-stage structure pattern. Thereby, since the number of necessary steps can be reduced, there is an increasing demand for an imprint mold having a multistage structure (see Patent Document 1).

  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.

  Further, it is known that a resist pattern is formed for each step to be formed in a normal dual damascene structure forming step.

  In addition, as a method for manufacturing a fine three-dimensional structure pattern such as a multistage structure, a method of forming a stepped structure using valence electron lithography is known.

  In the lithography method, it is known that a drawn resist pattern collapses in a development process after exposure. It is known that the collapse of the resist pattern is more likely to occur as the pattern has a higher aspect ratio.

  For example, a method for suppressing collapse of a resist pattern by forming a bridge on the resist surface layer has been proposed (see Patent Document 2).

  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 pattern.

  However, when a resist is coated on a substrate already provided with a step, the resist cannot be coated flatly (FIG. 4). If patterning is performed on a non-flat resist film, the positional accuracy of the resist pattern is lowered. Therefore, it is difficult to form a desired resist pattern. When the resist film is thickened so that the resist film becomes flat (FIG. 5A), the resist pattern collapses because the aspect ratio of the formed resist pattern increases according to the thickness of the resist film (FIG. 5 (b)), it is difficult to obtain a desired resist pattern.

  Also, since resist is generally an insulator, when drawing with an electron beam, a negative charge is induced on the surface of the resist film by an electron beam having a negative charge, and the negative charge passes through the resist film to form a substrate. If there is a problem in that the negative charge is accumulated on the resist film surface and the electron beam is bent near the resist film surface due to the accumulated negative charge, there is a problem that the drawing position shift occurs. It is difficult to newly pattern a resist on a substrate having a step.

  When a step is formed in the insulating substrate by performing anisotropic etching on the insulating substrate using the conductive hard mask layer as an etching mask, the step is provided because the hard mask layer does not exist in the concave portion of the step. In the process of newly patterning a resist on a substrate, drawing misalignment due to accumulation of negative charges becomes a problem.

  Hereinafter, an example of a conventional pattern forming method having a typical multistage structure will be described. First, a resist is coated on the substrate 11 provided with the hard mask layer 12 to form a resist film 13 (FIG. 3A), and the resist is patterned to form a resist pattern 14 (FIG. 3B). . Next, the hard mask layer 12 is etched using the resist pattern 14 as a mask, and the substrate 11 is etched using the hard mask pattern 15 as a mask (FIG. 3C). Next, washing is performed to produce a first layer pattern (FIG. 3D). Next, a resist is coated again on the substrate 16 on which the first layer pattern is formed (FIG. 3E), and the resist is patterned (FIG. 3F). Next, the hard mask layer is etched using the resist pattern as a mask, and the substrate is etched using the hard mask pattern as a mask (FIG. 3G). Next, it is washed to produce a second layer pattern (FIG. 3 (h)). Thereby, the board | substrate 17 in which the 2nd layer pattern was formed is produced.

  In the conventional typical multi-stage pattern forming method, in the second resist patterning, since the substrate already has a step, the resist cannot be coated flatly and it is difficult to obtain a desired resist pattern. And is not suitable for forming a fine three-dimensional structure pattern.

  Further, since the Nth pattern to be formed is smaller than the (N-1) th pattern to be formed, a finer pattern must be formed as the level difference of the multistage structure increases, and a desired resist pattern is obtained. It is difficult to form a fine three-dimensional structure pattern.

  In addition, since the hard mask layer does not exist in the concave portion of the step on the substrate on which the first pattern is formed, the negative charge induced in the resist by the electron beam is not discharged in the second resist patterning step. Since negative charges are accumulated on the resist film surface, the electron beam is bent near the resist film surface due to the negative charges, and drawing displacement occurs, which is unsuitable for forming a fine three-dimensional structure pattern.

Special table 2007-521645 gazette JP 2004-085792 A

  Therefore, the present invention has been made to solve the problems of the conventional typical multi-stage pattern forming method as described above, and is suitable for forming a fine three-dimensional structure pattern having a plurality of steps. It is an object to provide a simple pattern forming method.

The invention according to claim 1 of the present invention is a pattern forming method for forming a three-dimensional structure pattern, wherein a step of forming a hard mask layer on a substrate, and a first mask on the substrate using the hard mask layer as an etching mask. Performing the anisotropic etching, forming the second hard mask layer on the substrate already provided with a step by the first anisotropic etching, and using the second hard mask layer as an etching mask. Performing a second anisotropic etching on the substrate, and forming a first pattern on the substrate and, in order, on the side of the substrate on which the first pattern is formed, 2 and forming a pattern of up to N-th from th, the line width of the N-th pattern patterned side, wherein greater than the line width of the (N-1) th pattern It is. In the present invention, N is a natural number of 2 or more.

The invention according to claim 2 of the present invention is the pattern forming method according to claim 1 , wherein the substrate is a quartz substrate, and the hard mask layer is a layer made of chromium. is there.

The invention according to claim 3 of the present invention is an imprint mold manufactured using the pattern forming method according to claim 1 or 2 .

An invention according to claim 4 of the present invention is a photomask manufactured by using the pattern forming method according to claim 1 or 2 .

  According to the present invention, the resist can be coated with sufficient flatness in the second resist patterning (FIG. 2). For this reason, the positional accuracy of resist patterning can be improved, and a desired pattern can be obtained with high accuracy. Further, in the second resist patterning, negative charges induced in the resist by the electron beam are discharged through the second hard mask layer. For this reason, negative charges are not accumulated in the resist, and drawing displacement in the second resist patterning can be prevented, and drawing can be performed with high accuracy. Moreover, it can form in order from the finest pattern in a multistage structure pattern. Therefore, it is possible to suitably form a fine three-dimensional structure pattern having a plurality of steps.

It is a figure which shows the Example of the pattern formation method of this invention. It is a figure which shows the effect in the pattern formation method of this invention. It is a figure which shows an example of 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.

  According to the configuration of the present invention, when a desired three-dimensional structure pattern is formed on a substrate, the resist can be coated with sufficient flatness in the second resist patterning step. For this reason, the positional accuracy of resist patterning can be improved.

  Moreover, accumulation of negative charges in the resist film can be suppressed by the second hard mask layer. For this reason, it is possible to prevent misalignment of the drawing in the second resist patterning, and it is possible to perform drawing with high accuracy. Therefore, it is possible to suitably form a fine three-dimensional structure pattern having a plurality of steps.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the embodiments, the same components are denoted by the same reference numerals, and redundant description among the embodiments is omitted.

  Hereinafter, the pattern formation process in the embodiment of the present invention will be described.

(Step of forming a hard mask layer on the substrate (A))
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 any conductive material having a high etching selectivity in the step (C) of performing anisotropic etching on the substrate 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. By using a layer made of chromium for the hard mask layer, accumulation of negative charges due to electron beams can be prevented in lithography using a resist in the step (B) of patterning the hard mask layer described later.

(Step of patterning hard mask layer (B))
Next, the hard mask layer is patterned. As a method for patterning the hard mask layer, a lithography method using a resist is used. For example, the hard mask layer may be patterned 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. At this time, the pattern to be patterned is desirably the finest pattern among the three-dimensional structure patterns to be formed. By forming the finest pattern first, it is possible to coat the resist with sufficient flatness in lithography using the resist in the step (E) of patterning the second hard mask layer described later. The patterning of the second hard mask can be performed easily and accurately.

(Step of performing anisotropic etching on substrate (C))
Next, anisotropic etching is performed on the substrate from the side on which the pattern of the hard mask layer 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 depending on the hard mask layer and the substrate used.

(Step (D) of forming a second hard mask layer on a substrate having a step)
Next, a second hard mask layer is formed on the substrate having a step. 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.

  The hard mask layer may be any conductive material that has a high etching selectivity in the step (F) of performing second anisotropic etching on the substrate described later with respect to the selected substrate.

  The hard mask layer is preferably a layer made of chromium. By using a chromium layer for the hard mask layer, it is possible to prevent accumulation of negative charges due to electron beams in lithography using a resist in the step (E) of patterning the second hard mask layer described later. .

(Step of patterning second hard mask layer (E))
Next, the second hard mask layer is patterned. As a method for patterning the hard mask layer, a lithography method using a resist is used. For example, by forming a resist film on the second hard mask layer, patterning the resist film to form a resist pattern, and performing etching using the resist pattern as a mask, the second hard mask layer The patterning may be performed.

(Step of performing second anisotropic etching on substrate (F))
Next, anisotropic etching is performed on the substrate from the side on which the pattern of the second hard mask layer 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 depending on the hard mask layer and the substrate used.

  Further, by repeating the steps (D) to (F), the three-dimensional structure pattern formed on the substrate can be a multi-stage (N-stage) structure pattern of three or more stages.

  When the Nth pattern is formed, the line width of the Nth pattern may be larger than the line width of the (N−1) th pattern. Thus, the resist can be coated with sufficient flatness, and the Nth patterning can be easily performed with high accuracy.

After the steps (A) to (F), the resist is peeled off, and the hard mask layer is wet peeled and washed to produce an imprint mold with high positional accuracy.
In addition, a photomask with high positional accuracy is manufactured by using a conventional technique from the patterns manufactured by the above steps (A) to (F).

  Hereinafter, the pattern forming method of the present invention will be described with reference to an example in the case of specifically producing a photoimprint mold. The pattern forming method of the present invention is not limited to the following examples.

  First, a Cr layer 22 having a Cr film thickness of 15 nm was formed on a quartz substrate 21 as a hard mask layer, and a positive resist 200 nm thickness was coated thereon to form a resist film 23 (FIG. 1A).

Next, after irradiating the resist film 23 with an electron beam at a dose of 100 μC / cm ² with an electron beam drawing apparatus, development processing using a developer, rinsing, and drying of the rinse liquid are performed, and the resist pattern 24 (FIG. 1B) was obtained. Pure water was used as the rinse liquid.

Next, the Cr layer 22 was etched by dry etching using an ICP dry etching apparatus on the mold after development to obtain a Cr pattern 25 (FIG. 1C). 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 quartz substrate 21 was etched by dry etching using an ICP dry etching apparatus. 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.

Next, the resist was stripped by O ₂ plasma ashing (conditions: O ₂ flow rate 500 sccm, pressure 30 Pa, RF power 1000 W).

Next, wet peeling cleaning of the remaining Cr pattern was performed (FIG. 1D).
From the above, a quartz substrate (one stage) 26 patterned on the quartz substrate could be formed.

  Next, a Cr film having a thickness of 15 nm was formed on the patterned quartz substrate (first stage) 26 to form a Cr layer 22 '(FIG. 1E).

  Next, a 200 nm-thick positive resist was coated on a patterned quartz substrate (one step) 26 provided with a Cr layer 22 'on the step to form a resist film 23' (FIG. 1 (f)).

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

  Next, development processing using a developing machine, rinsing, and drying of the rinsing liquid were performed to form a resist pattern 24 ′ corresponding to the second layer step on the step (FIG. 1G). 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 form a Cr pattern (FIG. 1 (h)). 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 quartz substrate was etched by dry etching using an ICP dry etching apparatus. 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.

Next, the resist was removed by O ₂ plasma ashing (conditions: O ₂ flow rate 500 sccm, pressure 30 Pa, RF power 1000 W) (FIG. 1 (i)).

  Next, wet peeling cleaning of the remaining Cr layer was performed (FIG. 1 (j)). As a result, a patterned quartz substrate (two steps) 27 could be formed.

  From the above, it was possible to manufacture an imprint mold for optical imprinting with high positional accuracy using the pattern forming method of the present 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 and the like can be expected to be used suitably.

DESCRIPTION OF SYMBOLS 11 ... Substrate 12, 12 '... Hard mask layer 13, 13', 23, 23 '... Resist film 14, 14', 24, 24 '... Resist pattern 15, 15' ... Hard mask pattern 16 ... Patterned substrate ( 1 step)
17 ... Patterned substrate (two steps)
18 ... Collapsed resist pattern 21 ... Quartz substrate 22, 22 '... Cr layer 25, 25' ... Cr pattern 26 ... Patterned quartz substrate (one stage)
27 ... Patterned quartz substrate (two steps)

Claims (4)

A pattern forming method for forming a three-dimensional structure pattern,
Forming a hard mask layer on the substrate;
Performing the first anisotropic etching on the substrate using the hard mask layer as an etching mask;
Forming a second hard mask layer on the substrate already provided with a step by the first anisotropic etching;
Performing a second anisotropic etching on the substrate using the second hard mask layer as an etching mask;
Equipped with a,
Forming a first pattern on the substrate;
Forming the second to Nth patterns in order on the side of the substrate on which the first pattern is formed,
A pattern forming method, wherein a line width of the Nth pattern is larger than a line width of the (N-1) th pattern . In the pattern forming method according to claim 1,
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 of Claim 1 or 2 . Photomask fabricated using the pattern forming method according to claim 1 or 2.

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