JP4957139B2 - Mold manufacturing method - Google Patents

Description

The present invention relates to a method for producing a mold used for nanoimprinting.

  In the field of manufacturing semiconductors and the like, photolithography is used as a method for efficiently producing a fine resist pattern. In addition, establishment of a technique capable of accurately forming a nano-order pattern that is difficult with current photolithography technology is desired. However, when forming a pattern having a concavo-convex shape using conventional photolithography, it is necessary to go through a process with a large number of steps and types of materials used.

  In view of this, nanoimprint lithography (hereinafter referred to as NIL) in which a resist pattern is formed by an imprint mold, that is, a mold, has been proposed.

In NIL, transfer is performed using a flat plate mold in which a substrate such as silicon or quartz is etched and an uneven pattern is formed on the surface of the substrate. On the other hand, since high throughput is required, a mechanism for performing NIL in a short time by rotating a mold using a cylindrical (roller type) mold instead of a flat plate mold has been proposed (for example, “Patent” Reference 1 ”).
Japanese Patent Laid-Open No. 2005-5284

  In the roller mold, a material such as nickel (Ni) or resin is used because it is easily processed into a cylindrical mold.

  However, a mold made of nickel (Ni) or resin has a problem that it is difficult to obtain high processing accuracy during NIL.

The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a mold manufacturing method that has high processing accuracy and can be used as a roller mold .

In order to achieve the above-mentioned object, the present invention provides a method for producing a mold used for snanoimprinting,
A step (a) of forming a pattern made of minute irregularities on a substrate surface of a material to be a pattern portion, a step (b) of thinning the pattern portion, and the thinned pattern portion is a cylindrical portion or a polygonal column. And a step (c) provided on the outer periphery of the part.

  The step (a) includes, for example, a step of forming a pattern forming layer on the surface of the substrate, a step of forming a pattern composed of irregularities on the pattern forming layer, and a mask of the pattern forming layer on which the pattern is formed. The method includes a step of etching the substrate to form a pattern composed of irregularities on the substrate to form a pattern portion.

  In the step (b), when the back grinding, etching, blasting, slicing, or the substrate is composed of two or more layers, the pattern portion is formed into a thin film by separating the layer other than the surface having irregularities on the surface. Turn into.

According to the present invention, it is possible to provide a mold manufacturing method that has high processing accuracy and can be used as a roller mold .

  Hereinafter, a mold 1 and a method for manufacturing the mold 1 according to an embodiment of the present invention will be described in detail based on the drawings. The mold 1 has a cylindrical shape or a polygonal column shape. Here, the cylindrical mold 1 will be described as an example.

FIG. 1 is a schematic view of the mold 1, and FIG. 2 is a cross-sectional view of the mold 1 taken along line NN in FIG. As shown in FIG. 1, the mold 1 includes a cylindrical portion 5 and a pattern portion 3 having an uneven pattern formed on the cylindrical surface of the cylindrical portion 5. The cylindrical portion 5 is a portion that becomes the core of the mold 1. The pattern portion 3 is a plate-like member that forms the cylindrical shape of the mold 1.
As shown in FIG. 2, in the mold 1, a plurality of pattern portions 3 are joined to the outer peripheral surface of the cylindrical portion 5. The mold 1 is used for nanoimprinting.

  3 and 4 are diagrams showing each step of the method for manufacturing the mold 1.

  FIG. 3A shows the substrate 11 constituting the pattern portion 3 of the mold 1. An uneven pattern is formed on the substrate 11. The material of the substrate 11 is silicon (Si), aluminum (Al), titanium (Ti), quartz, other glass, chromium (Cr), silicon carbide (SiC), silicon nitride (SiN), or the like. In order to form a fine concavo-convex pattern, it is desirable that the substrate 11 be silicon (Si) because a nano-order processing apparatus is easily available. In the following description, the substrate 11 uses silicon (Si).

  First, as shown in FIG. 3B, a pattern formation layer 13 such as a resist is formed on the surface of the substrate 11. The pattern formation layer 13 is a layer necessary for producing a concavo-convex pattern on a substrate, and is finally removed. For example, when the pattern forming layer 13 is a resist, the pattern forming layer 13 can be formed by a method such as spin coating or spray coating. Next, the surface of the pattern forming layer 13 corresponding to the pattern to be formed is irradiated with an electron beam or the like to be exposed. Examples of the exposure method include exposure using an electron beam, exposure using a laser drawing machine, exposure using ultraviolet light using a mask, and the like.

  Next, as shown in FIG. 3C, processing such as development is performed to form a pattern 15a on the surface of the pattern forming layer 13. Further, the substrate 11 is etched using the pattern forming layer 13 on which the pattern 15a is formed as a mask to form a pattern 15b on the substrate 11 and the pattern forming layer 13 (FIG. 3D).

Etching may be either dry etching or wet etching. In the case of dry etching, as the etching gas, generally, a fluorine-based gas such as CF ₄ , SF ₆ , or CHF ₃ , a chlorine-based gas such as Cl ₂ or CCl ₄ , a bromine-based gas such as HBr, or the like is used.
In the case of wet etching, potassium hydroxide (KOH), tetramethylammonium hydroxide (TMAH), or hydrofluoric acid (mixed liquid of hydrofluoric acid and nitric acid) is used as the chemical solution. When KOH or TMAH is used as a chemical solution for wet etching, if the substrate to be etched is a single crystal, the side wall that appears by etching becomes a facet surface. At that time, the facet plane differs depending on the crystal orientation of the used substrate and the shape of the etched pattern 15a. The depth varies depending on the plane orientation and etching time.

  Next, as shown in FIG. 3E, when the pattern forming layer 13 is peeled off, a pattern 15 c that is a set of fine irregularities is formed on the substrate 11.

Next, a layer of the coating material 17 is formed on the substrate 11 (FIG. 3F). The coating material 17 is for preventing damage to the substrate 11 due to polishing or cutting when the substrate 11 on which the pattern 15c is formed is thinned. Examples of the coating material 17 include a tape and a resin (for example, wax).
The tape is, for example, a resin tape with an adhesive on the protective surface side, and the surface on which the pattern 15c is formed is protected by attaching the tape to the substrate 11.
The resin is applied to the surface of the substrate 11 on which the pattern 15c is formed. It is necessary to apply a resin having a sufficient thickness so as to sufficiently withstand polishing in a process described later.
Further, a steel plate or the like may be attached to the surface of the substrate 11 on which the pattern 15c is formed. When a steel plate is attached, an adhesive such as a resin is used.

  Next, the substrate 11 is thinned (FIG. 4A). The thinning is performed in order to make the substrate 11 curved so that it can be easily curved. That is, the substrate 11 needs to be processed sufficiently thin so that it can be attached to the cylindrical surface of the cylindrical portion 5. Examples of the thinning method include back grinding, etching, blasting, slicing, and separation of a thin film layer.

As described later, the back grinding grinds and cuts the substrate 11 with an abrasive. Etching is dry etching or wet etching, and is a method of cutting the substrate 11 using chemicals or plasma. Blasting is a method of physically cutting the substrate 11 with high-pressure fine particles. Slicing is a method of thinning the substrate 11 by physical cutting.
In the case where the substrate is composed of two or more layers, it can be considered that the substrate is composed of a pattern portion having irregularities and a support substrate that supports the pattern portion. Therefore, by separating the pattern portion from the support substrate, the same effect as that obtained by thinning the substrate can be obtained as in the other methods described above. That is, a thin film is used in place of the substrate 11, and the thin film is fixed using a support substrate, and the thin film is processed to be uneven. After processing the irregularities, the support substrate is removed, and only the thin film portion is cylindricalized.

As a thinning method, back grinding is desirable.
The thinned substrate 11 needs to be sufficiently thin with respect to the radius of the cylindrical portion 5 and be able to withstand bending.

Next, the thinning of the substrate 11 by back grinding will be described in more detail with reference to FIG.
The back grinding is performed using the grinder 20. As shown in FIG. 5, the grinder 20 includes a rotating unit 21 and a surface plate 25. The substrate 11 on which the coating material 17 is formed is fixed to the rotating unit 21. The rotating unit 21 rotates in the A direction. There is an abrasive 23 between the surface plate 25 and the substrate 11, and the rear surface of the substrate 11, that is, the surface opposite to the surface on which the pattern 15 c is formed is polished by this abrasive 23.

  As the abrasive 23, for example, diamond fine particles or slurry (microparticulate ceramic) is used. The surface plate 25 may also rotate. Further, instead of the surface plate 25 and the abrasive 23, a polishing plate having irregularities on the surface may be used.

  As described above, the substrate 11 is thinned to become a sufficiently thin substrate 11 capable of withstanding bending when being bonded to the cylindrical portion 5.

  Next, as shown in FIG. 4B, the coating material 17 is separated from the substrate 11 to obtain the pattern portion 3. The separation method differs depending on the type of the coating material 17, but is generally removed by a chemical that dissolves the coating material 17. Moreover, when this is a case of a tape, there exists a thing with which adhesive force weakens by irradiation of UV light.

  Here, if necessary, the outer shape of the substrate 11 is processed. That is, for example, processing such as processing the circular substrate 11 into a square. The processing of the outer shape is performed by a method such as dicing or etching. Dicing is a cutting method that physically cuts, and there are a blade method and a laser method.

Next, as shown in FIG. 4C, the thinned pattern portion 3 is bent along the cylindrical surface of the cylindrical portion 5, joined to the cylindrical portion 5, and attached. Here, when the mold 1 is used for thermal imprinting, it is necessary to consider the thermal expansion coefficient of the cylindrical portion 5.
Examples of the bonding method include bonding with an adhesive, bonding with a eutectic metal, siloxane bonding via an oxide film, and direct bonding by surface activation.

  An auxiliary layer made of a material other than silicon may be formed between the pattern portion 3 and the cylindrical portion 5. In some cases, a bonding layer is formed by the bonding as described above to serve as an auxiliary layer. The presence or absence of an auxiliary layer does not matter, but it is preferable that there is no auxiliary layer.

  In the case of FIG.2 and FIG.4 (c), the some pattern part 3 is bonded together to the cylindrical part 5. FIG. It is desirable that the joint between the pattern portions 3 is smooth or recessed from the pattern to be transferred.

  FIG. 6 is a diagram illustrating a bonding state of the pattern unit 3. As shown in FIG. 6A, when the pattern portion 3a and the pattern portion 3b are joined, if the seam 27 is convex, the seam 27 is transferred to the transfer surface when the mold 1 is rotated and transferred. Pressure.

Therefore, when joining the pattern part 3c and the pattern part 3d, the joint 27 is made concave. Thereby, it is possible to prevent the joint 27 from coming into contact with the transfer surface due to the rotation of the mold 1. As described above, when the plurality of pattern portions 3 are bonded to the cylindrical portion 5, it is desirable that the joints between the pattern portions 3 be smooth or concave.
Further, as shown in FIG. 6B, a gap may be provided between the patterns 3e and 3f.

  As mentioned above, the mold 1 as shown in FIG. 2 is produced by bonding the pattern portion 3 having the uneven pattern to the cylindrical portion 5.

FIG. 10 is a diagram showing the mold 1a when the auxiliary layer 12 is present. As shown in FIG. 10, the substrate 11 is attached to the cylindrical portion 5 via the auxiliary layer 12.
Here, the pattern unit 3 includes a substrate 11 (pattern forming layer) and an auxiliary layer 12.

  In the above-described embodiment, the plurality of pattern portions 3 are attached to the cylindrical portion 5, but one pattern portion 3 may be attached to the cylindrical portion 5.

  In addition, the order of the formation of the uneven pattern and the thinning process may be reversed. The coating material 17 can also be separated after the pattern portion 3 is attached to the cylindrical portion 5.

According to the present embodiment, the mold 1 can be cylindrical (roller type), and a pattern composed of irregularities can be transferred by the rotation of the mold 1, so that imprinting can be performed at high speed.
Moreover, a fine pattern can be transferred by using silicon.

  The mold 1 is mainly used for pattern transfer by heat, that is, thermal imprint. In thermal imprinting, the cylindrical mold 1 is brought into contact with an object to which a pattern is to be transferred, and imprinting is performed by rotating about a shaft. Thereby, compared with the conventional method of pressing and releasing, imprinting can be performed at high speed.

  The mold 1 can also be used for optical imprinting if the material to which the pattern is transferred is transparent. In this case, the resist is cured by applying ultraviolet light or the like from the back side of the object to be transferred, that is, the side opposite to the mold 1.

  Next, an embodiment of the present invention will be described with reference to FIGS. 7 and 8 are diagrams showing a process of manufacturing the mold 45 in the embodiment.

FIG. 7A is a plan view of the single crystal silicon substrate 31 that is the material of the mold 45, and FIG. 7B is a side view of the single crystal silicon substrate 31.
Two single crystal silicon substrates 31 having a diameter of 200 mm and a thickness of 725 μm were prepared. First, a resist 33 was applied to the surface of the single crystal silicon substrate 31 (FIG. 7C). Next, the electron beam B was irradiated (FIG. 7D), and the pattern 35a was drawn (FIG. 7E). The pattern 35 was a 300 nm hole.
Next, a pattern 35b was formed on the substrate 31 by dry etching (FIG. 7F). A mixed gas of HBr and O ₂ was used as the etching gas. The etching time was set so that the etching depth at this time was 200 nm.

Next, the resist 33 was removed, and a polishing tape 37 was applied as a coating material on the single crystal silicon substrate 31 to protect the pattern surface (FIG. 7G).
Next, the single crystal silicon substrate 31 was polished to obtain two types of single crystal silicon substrates 31 having a thickness of 100 μm and 50 μm (FIG. 8A). A back grinder was used for polishing.

  Next, as shown in FIG. 8 (b), the single crystal silicon substrate 31 was pasted as a pattern portion 41 on the cylindrical portion 43 with the tape 37 being stuck. As the substrate cylindrical portion 43, one having a radius of 32 mm and a length of 200 mm was used. At this time, the pattern portion 41 having a thickness of 50 μm could be attached to the cylindrical portion 43. However, the pattern part 41 having a thickness of 100 μm was crushed during bending. In the following, damage and breakage due to bending of a silicon substrate will be described in more detail.

FIG. 9 shows an outline of a test relating to the bendability of the silicon substrate 51. The silicon substrate 51 that was used had a surface orientation of (100) and a notch in the <110> direction.
Similar to the above, three silicon substrates 51 each having a diameter of 200 mm and a thickness of 50 μm and a silicon substrate 51 having a diameter of 200 mm and a thickness of 100 μm were prepared. The bending directions were <110>, <100>, and <-110>, respectively, and they were wound around a cylindrical portion 53 having a radius of 32 mm and a length of 200 mm.

FIG. 9A is a front view showing a state in which the silicon substrate 51 is wound around the cylindrical portion 53, and FIG. 9B is a side view thereof. FIG. 9A is an arrow view from the H direction in FIG. 9A and 9B, the silicon substrate 51 is aligned with three types of plane orientations <110>, <100>, and <-110> in the direction of the arrow D, and the cylindrical surface of the cylindrical portion 53 And bent like C. The bending widths E ₁ and E ₂ were set to the same length, and the bending width E ₁ (= E ₂ ) when the silicon substrate 51 was damaged was recorded. Table 1 shows the results of the above tests.

In Table 1, the thickness indicates the thickness of the silicon substrate 51. The plane orientation in the bending direction D is the plane orientation of the substrate 51 in accordance with the bending direction D shown in FIG. Bending width E ₁ shows the bending width E ₁ when the silicon substrate 51 is damaged. When bent by breakage did not occur, the bent width E ₁ is 0.

As can be seen from the results in Table 1, no breakage occurred when the thickness was 50 μm and the bending direction was <100>. That is, the silicon substrate 51 could be wound once around the cylindrical portion 53 having a radius of 32 mm. The silicon substrate 51 having a thickness of 100 μm was all damaged in the middle and could not be wound.
As described above, the silicon substrate 51 with a thickness of 50 μm can be attached to the cylindrical portion 53 with a radius of 32 mm, but the object has the same outer shape such as material, crystallinity, and thickness. However, since the ease of breakage differs depending on the bending direction, it is necessary to consider the bending direction when applying.

  Further, during the test, the entire silicon substrate 51 does not have a constant curvature, and stress is applied in the vicinity of the cylindrical portion 53, so that the silicon substrate 51 may actually be wound around a cylindrical portion having a smaller radius than the cylindrical portion 53 used in this experiment. There is.

  From the results of the above test, in the mold 1, the thickness of the pattern portion 3 needs to be sufficiently smaller than the circumferential radius of the cylindrical portion 5.

  As mentioned above, although preferred embodiment, such as a mold concerning the present invention and a manufacturing method of a mold, was described, referring to an accompanying drawing, the present invention is not limited to this example. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

  For example, in the above-described example, the cylindrical mold 1 has been described, but a polygonal column-shaped mold 1 may be used. However, in this case, when transfer is performed using a mold, the axis serving as the center of rotation moves up and down depending on whether the transfer surface of the mold 1 is in contact with the object to be transferred or the corner of the polygon is in contact. . Therefore, it is necessary to control the contact pressure during rotation in order to prevent compression or breakage when the corner contacts the object. Further, when the polygon has a large number of corners, the shape is close to a circle, and the shake of the axis is reduced, but the area per pattern portion 3 is reduced. In that case, it is necessary to consider increasing the bottom area of the polygon.

Perspective view of mold 1 Cross section of mold 1 The figure which shows each process in the manufacturing method of the mold 1 The figure which shows each process in the manufacturing method of the mold 1 The figure which shows the grinder 20 The figure which shows joining of the some pattern part 3 The figure which shows the manufacturing process of the mold 45 in an Example. The figure which shows the manufacturing process of the mold 45 in an Example. The figure which shows arrangement | positioning of the single crystal silicon substrate 51 and the cylindrical part 53 in an Example. The figure which shows joining of the pattern part 3 and the cylindrical part 5 in case there exists the auxiliary layer 12

Explanation of symbols

DESCRIPTION OF SYMBOLS 1, 1a ......... Mold 3 ......... Pattern part 5 ......... Cylinder part 11 ......... Substrate 12 ......... Auxiliary layer 13 ......... Pattern forming layer 15 ......... Pattern 17 ......... Coating material 20 ... …… Grinder 21 ……… Rotating part 23 ……… Abrasive 25 ……… Surface plate 31 ……… Single crystal silicon substrate

Claims (6)

A method for producing a mold used for nanoimprinting,
A step (a) of forming a pattern consisting of minute irregularities on a substrate surface of a material to be a pattern portion;
A step (b) of thinning the pattern portion;
Providing the thinned pattern part on the outer periphery of the cylindrical part or the polygonal column part (c);
A method for manufacturing a mold, comprising: The step (a)
Forming a pattern forming layer on the surface of the substrate;
Forming a pattern composed of irregularities on the pattern forming layer;
Etching the substrate using the pattern forming layer on which the pattern is formed as a mask, forming a pattern composed of irregularities on the substrate, and forming a pattern portion;
Method for producing a mold according to claim 1, characterized by including the. At least the pattern unit manufacturing method for a mold according to claim 1, characterized in that the silicon as a material. In the step (b), when the back grinding, etching, blasting, slicing, or the substrate is composed of two or more layers, the pattern portion is thinned by separating the layer other than the surface having irregularities on the surface. The method for producing a mold according to claim 1, wherein: Wherein step (c), the outer periphery of the cylindrical portion or polygonal portion, one or mold fabrication method of claim 1, wherein the plurality of patterns is characterized in that it is provided to be joined. The mold manufacturing method according to claim 5 , wherein adjacent pattern portions are bonded to each other so that a joint is smooth or concave at the bonding portion between the plurality of pattern portions.

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