JP2007027361A - Mold for imprint - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a mold for imprint for preventing pattern destruction of mold for imprint, enabling long-life of the mold for imprint, and realizing accurate transfer of pattern in the mold for imprint to form projected/recessed patterns on a resist layer coated on the substrate surface to be transferred, and also to provide a method of manufacturing the mold for in-print. <P>SOLUTION: In the mold for imprint, a buffer area is allocated in the periphery of the pattern area 172 of the mold in order to prevent pattern destruction and resultant pattern defect and generation of foreign matter of the mold 170 for imprint wherein the projected/recessed pattern formed on the mold is transferred to the resist layer coated on the substrate surface. The buffer area 173 in the mold for imprint is allocated at least to corners formed by surrounding the pattern area with straight lines. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a mold used for pattern formation using an imprint method.

  Until now, a method of optically transferring a pattern has been used to form a pattern that requires fine processing, such as a manufacturing process of a semiconductor device. As an example, a photomask in which a pattern made of an opaque material such as chromium is formed on a part of a transparent substrate such as glass is formed, and this is formed on a semiconductor substrate (hereinafter referred to as a sensitive substrate) coated with a resist. The pattern of the photomask is transferred to the sensitive substrate by placing it directly or indirectly and irradiating light from the backside of the photomask to selectively expose the resist in the light transmitting portion. It was. This technique is generally called a photolithography method. Further, in the current semiconductor device manufacturing process, a method of optically reducing a mask pattern and transferring the pattern onto a semiconductor substrate has become mainstream.

  However, in these pattern forming methods, the size and shape of the pattern to be formed greatly depend on the wavelength of light to be exposed. For example, in the manufacture of advanced semiconductor devices in recent years, the exposure wavelength used for photolithography is 150 nm or more, while the minimum line width is 90 nm or less, reaching the resolution limit due to the light diffraction phenomenon. Although super-resolution techniques such as proximity effect correction (OPC) and phase shift mask are used to increase the resolution of the resist, it is difficult to faithfully transfer the mask pattern onto the semiconductor substrate. It has become.

  Further, in the case of reduced projection exposure, since alignment accuracy is required not only in the horizontal direction of the substrate but also in the vertical direction, precise stage control (X, Y, Z, θ) of a photomask and a semiconductor substrate is required. Thus, there is a drawback that the cost of the apparatus becomes high.

  The problem of device cost that requires pattern blur due to the diffraction phenomenon of light and complicated mechanisms is not only in the manufacture of semiconductor devices, but also in the formation of various patterns such as displays, recording media, biochips, optical devices, and hot embossing. This is the same because the photolithographic method is used, and the mask pattern cannot be faithfully transferred.

  From such a background, S.M. Y. Chou et al. Propose a technique called imprinting method (or nanoimprinting method) that is very simple but suitable for mass production, and can faithfully transfer a much finer pattern than conventional methods. (Refer nonpatent literature 1).

  By the way, although there is no strict distinction between imprinting and nanoimprinting, nanometer-order methods used in the manufacture of semiconductor devices are called nanoimprint methods, and other micrometer-order methods are called imprint methods. There are many. Hereinafter, all are referred to as an imprint method.

S. Y. A conventional imprint method proposed by Chou et al. Will be described with reference to FIG. 8A to 8E are side cross-sectional views of steps showing a pattern forming method by a conventional thermal imprint method. First, a silicon substrate 101 having a silicon oxide film 102 formed on the surface is prepared, and a pattern corresponding to a negative / positive inversion image of a pattern to be finally transferred to the semiconductor substrate or the like is formed on the silicon oxide film 102 on the silicon substrate 101. Form. For example, a normal electron beam lithography technique can be used for patterning the silicon oxide film 102. Thus, an imprint mold 100 having irregularities corresponding to a negative / positive inverted image of a pattern to be transferred onto the surface of a semiconductor substrate or the like is formed (see FIG. 8A).

Next, a resist material such as PMMA is applied on the silicon substrate 111 on which a pattern is to be formed, thereby forming a resist layer 112 (see FIG. 8B). Next, the silicon substrate 111 on which the resist layer 112 is formed is heated to about 120 to 200 ° C. to soften the resist layer 112. Next, the imprint mold 100 and the silicon substrate 111 are overlapped so that the uneven surface side of the imprint mold faces the coated surface side of the resist layer of the silicon substrate 111, and pressure-bonded with a pressure of about 3 to 20 MPa ( (Refer FIG.8 (c)). Next, in a state where the imprint mold 100 is pressure-bonded to the silicon substrate 111, the temperature is lowered to about 100 ° C. or less to cure the resist layer 112, and the imprint mold is detached. As a result, a pattern corresponding to the concavo-convex pattern of the imprint mold 100 is formed on the resist layer 112 on the silicon substrate 111 (see FIG. 8D). Next, since a portion corresponding to the convex portion of the imprint mold 100 remains as a thin residual film on the silicon substrate 111, it is removed by an O ₂ RIE method (reactive ion etching using oxygen gas) (FIG. 8 (e)).

  In this way, a resist pattern is formed using the imprint method. This method is called a thermal imprint method because it involves a thermal cycle of temperature rise and cooling.

  The thermal imprint will be described. However, in the pattern forming method using the conventional thermal imprint method, there are problems to be solved in the overlay position accuracy and the strength and durability of the imprint mold. That is, as described above, the pattern forming method using the imprint method requires an extremely high pressure of about 3 to 20 MPa when the imprint mold and the substrate are pressed, and such a high pressure is applied. However, it is extremely difficult to maintain the horizontal positional accuracy between the imprint mold and the substrate. Further, when the number of times of transfer is increased at such a high pressure, there arises a problem that the imprint mold is damaged. Furthermore, because it involves a thermal cycle, the positional accuracy deteriorates due to the difference in thermal expansion coefficient between the substrate to be transferred and the mold material for imprinting, and the processing time is long due to temperature rise and cooling. appear. That is, it can be said that the fundamental problem of thermal imprinting is two points of high press pressure and high temperature.

In order to solve such a problem, Patent Document 1 proposes a pattern formation method by an optical imprint method as described below. The optical imprint will be described. 9A to 9E are side cross-sectional views of steps showing a pattern forming method by a conventional optical imprint method. Specifically, as shown in FIG. 9A, an imprint mold 120 having an uneven surface is produced by etching a substrate made of a light-transmitting material such as quartz with an electron beam lithography method or the like. To do. Next, as shown in FIG. 9B, a low-viscosity liquid photocurable resin composition (resist 112) is applied onto the silicon substrate, and as shown in FIG. The mold 120 is pressure-bonded to the photocurable resin composition (resist 112). The pressing pressure at this time may be as small as about 0.01 to 5 MPa. In this state, light is irradiated from the back surface of the imprint mold 120 to cure the photocurable resin composition (resist 112). As shown in FIG. 9D, the thin residual film of the photocurable resin (resist 112) to which the pattern of the imprint mold 120 has been transferred is removed by the O ₂ RIE method or the like. Thereby, as shown in FIG.9 (e), the resin pattern is obtained.

According to this method, since the resin is cured by a photoreaction, there is no thermal cycle (room temperature is sufficient), the processing time can be greatly shortened, and the positional accuracy is not degraded by the thermal cycle. In addition, since the photocurable resin composition is a liquid having a low viscosity, the pattern can be transferred without pressing the imprint mold to the photocurable resin composition at a high pressure like thermal imprinting. Can do. Therefore, the degradation of the positional accuracy due to the press pressure and the damage of the imprint mold are dramatically reduced. That is, optical imprinting can be said to be a technology that solves the high pressing pressure and high temperature that are the fundamental problems of thermal imprinting.

  Further, as a method for solving the problems of the strength and durability of the imprint mold in the thermal imprint, another method such as SiC mold has been proposed. The SiC mold will be described. For example, the surface of the mold for imprinting can be modified to a hard and strong material such as SiC, SiN, SiCN by plasma carburizing or plasma nitriding on the surface of the recon mold (Patent Document 2), There exists a method (refer patent document 3), such as producing mold for itself with SiC.

  However, when the imprint mold is pressure-bonded to a sensitive substrate such as a resist coated on a silicon substrate, the imprint mold and the sensitive substrate are pressure-bonded in a plane, but the entire surface of the imprint mold (all parts) It is impossible to contact the sensitive substrate at the same time. This is because the imprint mold and the sensitive substrate have a certain degree of inclination caused by the apparatus or when the imprint mold is mounted or when the sensitive substrate is mounted. For this reason, because one part of the imprint mold pattern always comes into contact with the sensitive substrate first, the imprint mold pattern part that is first contacted breaks down due to the concentration of the imprint load. There is. Normally, the pattern at the extreme end of the pattern area comes into contact first, resulting in pattern destruction. Even in the case of the imprint method under relatively low pressure conditions such as the optical imprint of the background technology 3 and the hard and strong imprint mold of the background technology 4, the imprint apparatus load concentrates on one point. The destruction of the mold pattern cannot be avoided.

  This will be described with reference to FIG. 10A to 10E are cross-sectional views illustrating a state in which a conventional imprint mold is imprinted on a sensitive substrate. A state where the imprint mold imprints on the sensitive substrate is shown. FIGS. 10A and 10B show a case of ideal imprinting, and FIGS. 10C to 10E show a case of actual imprinting. Ideally, the imprint mold is imprinted without breaking the imprint mold pattern as long as it faces the sensitive substrate parallel to the sensitive substrate (see FIG. 10A). (See FIG. 10B). However, since they are not completely parallel to each other for the above reasons (see FIG. 10C), the load concentrates on the pattern portion that first contacts the sensitive substrate by imprinting, and pattern destruction occurs ( (Refer FIG.10 (d)). Thereafter, since a load is applied up to a value set by the imprint apparatus, the inclination between the imprint mold and the sensitive substrate is corrected and parallel, so that most of the pattern is imprinted as planned (FIG. 10 ( e)). Further, when the state of the imprint mold before and after imprinting was observed, the pattern was normally formed before imprinting (see FIG. 11), but part of the pattern was destroyed after imprinting (see FIG. 11). 12). For this reason, the broken pattern portion of the imprint mold cannot be accurately transferred to the sensitive substrate, but also becomes a foreign matter or a defect due to a fragment of the imprint mold. Furthermore, since this imprint mold also has a pattern defect, it cannot be used for imprinting.

The known literature is described below.
JP 2000-194142 A JP 2004-148494 A JP 2004-160647 A Appl. Phys. Lett. , Vol. 67, p. 3314 (1995) A thorough explanation of nanoimprint technology Electric Journal, issued on November 22, 2004 P20-38

  An object of the present invention is to provide an imprint mold capable of preventing the pattern destruction of the imprint mold in the imprint method, extending the life of the imprint mold, and transferring the pattern accurately. It is to be.

  The invention according to claim 1 of the present invention is an imprint mold for transferring a concavo-convex pattern formed on a mold to a resist layer on a substrate surface, and a buffer portion is disposed in a peripheral portion of the concavo-convex pattern area of the mold. The mold for imprint characterized by these.

  The invention according to claim 2 of the present invention is the imprint mold according to claim 1, wherein the buffer portion is disposed at least at a corner portion when the uneven pattern area is surrounded by a straight line. .

  According to the present invention, in the imprint method, it is possible to prevent the pattern destruction of the imprint mold, which has been a weak point, and the occurrence of pattern defects and foreign matters due to the pattern destruction. In addition, this makes it possible to extend the life of the imprint mold, which can greatly reduce the cost.

  The best mode of the imprint mold of the present invention will be described, and the mold manufacturing method and imprint method will also be described.

  FIG. 1 is a perspective view illustrating an imprint mold in which a buffer portion is provided at a corner portion of a pattern area according to the present invention. FIG. 2 is a perspective view illustrating an imprint mold in which a buffer portion is provided on the entire outer periphery of the pattern area of the present invention. 1 and 2 show imprint molds 160 and 170 according to the present invention, in order to prevent mold pattern destruction and the occurrence of pattern defects and foreign matters, the outer peripheral portions of mold pattern areas 162 and 172. The buffer parts 163 and 173 are disposed in the slab.

  FIG. 1 shows an imprint mold 170 in which a concavo-convex pattern is formed on a support substrate 171 and a buffer portion 173 is arranged around the pattern area 172. The buffer portions 173 are arranged at the four corners of the corner portion of the peripheral portion in the rectangular transfer area including the pattern area and the peripheral portion thereof. The buffer portion 173 has a role to prevent the pattern damage of the concavo-convex shape of the imprint mold or the generation of pattern defects and foreign matters due to the imprint mold when transferring to the resist layer coated on the substrate surface of the substrate to be transferred. .

  FIG. 2 shows an imprint mold 160 in which a concavo-convex pattern is formed on a support substrate 161 and a buffer portion 163 is arranged around the pattern area 162. The buffer portion 163 is disposed on the entire surface of the periphery of the square transfer area including the pattern area and the periphery thereof. The buffer portion 163 has a role of preventing the pattern damage of the concavo-convex shape of the imprint mold or the generation of pattern defects or foreign matters due to the imprint shape when transferring to the resist layer applied on the substrate surface of the substrate to be transferred. .

  When forming the concave / convex pattern of the imprint mold by the lithography technique and the etching technique, the buffer part 163 is also formed at the same time. Therefore, the number of processes is not increased, and the height of the buffer part 163 is the pattern area 162. Since this is the same as the main pattern, the main pattern imprint is not obstructed. As an example of the arrangement of the buffer portion, there is a method of arranging an uneven pattern around the pattern area outer periphery (see FIG. 2), a method of arranging only at the corner of the pattern area (see FIG. 1), etc. There is.

  If the total area of the buffer is too large, the press pressure applied to the pattern area may not reach the expected pressure even when the maximum load of the imprint device is applied. A method (see FIGS. 1 and 2) may be selected. In fact, when the pattern area is surrounded by a straight line, for example, assuming a rectangular transfer area larger than the pattern area, the buffer section may be arranged at least at the corner of the transfer area. The buffer portion may be freely arranged, or may be arranged as shown in FIG.

  FIG. 4 is a process cross-sectional view in the case of imprinting using the imprint mold of the present invention provided with a buffer portion as shown in FIGS. 4 (a) to 4 (c) are side cross-sectional views illustrating a process in the case of imprinting using an imprint mold having a buffer portion according to the present invention. When imprinting is performed, the imprint mold 190 and the sensitive substrate (of which the silicon substrate 191 and the resist 192) are inclined are first brought into contact with the buffer portion 194 (FIG. 4B). )reference). Furthermore, in the process of pressing up to the set load of the imprint apparatus, the pattern area 193 is imprinted after the opposing surfaces of the imprint mold 190 and the sensitive substrates (191, 192) become parallel (FIG. 4 ( c)).

  According to this method, there is no pattern destruction of the uneven shape of the imprint mold, and no transfer pattern defect or foreign matter is generated due to this. Further, the imprint mold can be used repeatedly for imprinting, and the life of the mold can be extended.

  The material of the mold for imprinting of the present invention is not only a material generally used for imprinting such as silicon, quartz, nickel, diamond, SiC, but also a silicon compound, a metal such as chromium, iron, aluminum and the compound thereof, PDMS ( An organic metal compound such as polydimethylsiloxane can be used.

  The imprinting method of the present invention uses a thermal imprinting method using a thermosetting resin, a photoimprinting method using a photocurable resin, or HSQ (Hydrogen Silses Quioxane) that does not require thermosetting as a transfer material. The present invention can be applied to any imprinting method such as a room temperature imprinting method used, or a soft lithography imprinting method using a PDMS (polydimethylsiloxane) mold which is a soft material compared to an inorganic material.

  Examples of the present invention will be described below.

In the present invention, the type of imprint method is not limited, but in Example 1, a Si mold for thermal imprinting in which a buffer portion is arranged on the outer periphery of the pattern area shown in FIG. 2 was manufactured. First, a method for manufacturing the Si mold is shown in FIG. FIGS. 5A to 5D are side cross-sectional views showing the steps for manufacturing a Si mold for thermal imprinting having a buffer portion in Example 1 of the present invention. A 4-inch silicon wafer 201 was prepared as a support substrate to be a mold base. The silicon substrate 201 is coated with an electron beam resist 202 (trade name, manufactured by ZEP520 / manufactured by ZEON CORPORATION) to a thickness of 500 nm (see FIG. 5A), and is drawn and developed by an electron beam drawing apparatus to form a pattern area 203. An uneven pattern having a dot of 200 nm in diameter and a pattern 204 serving as a buffer portion 206 were formed (see FIG. 5B). The conditions at this time were a drawing dose of 100 μC / cm ² and a development time of 2 minutes.

Next, a Si pattern was formed by Si dry etching using an ICP dry etching apparatus (see FIG. 5C). The Si etching conditions were as follows: CF ₄ gas flow rate 30 sccm, Ar flow rate 50 sccm, pressure 2 Pa, ICP power 500 W, RIE power 200 W. Finally, the resist was peeled off by O ₂ plasma ashing (conditions: O ₂ flow rate 500 sccm, pressure 30 Pa, RF power 1000 W) (see FIG. 5D). The uneven Si patterns in the pattern area 205 are pillars (cylinders) having a diameter of 200 nm and a height of 200 nm, and are arranged in a lattice pattern at a pitch of 400 nm.

  The mold manufacturing technology so far is based on the conventional electron beam lithography technology and dry etching technology, and is not a special technology. However, when the mold is completed, the buffer part is created at the same time as the main pattern. Is part of the present invention. By creating simultaneously with the main pattern, the number of processes is not increased, and the height of the buffer portion is the same as that of the main pattern, so that imprinting of the main pattern is not hindered.

  FIG. 6 shows a mold produced in this example. In the imprint mold 210 of Example 1 in FIG. 6, the pattern area 212 is 25 mm square, and the transfer area 214 including the buffer pattern 213 is 50 mm square. The width of the buffer pattern 213 was 10 mm. FIG. 6A is a top view, and FIG. 6B is a side sectional view.

  Next, a Si mold for thermal imprinting in which a buffer portion was arranged at a corner portion of the pattern area shown in FIG. 1 was manufactured by the same manufacturing method as in Example 1. Since the manufacturing method is the same as that of Example 1, it is omitted. Further, in the same manner as in Example 1, in the Si pattern, pillars (cylinders) having a diameter of 200 nm and a height of 200 nm were arranged in a lattice shape at a pitch of 400 nm.

  FIG. 7 shows the mold produced in Example 2. In the imprint mold 220 of Example 2 in FIG. 7, the pattern area 222 is 25 mm square, and the pattern area 224 including the buffer pattern 223 is 50 mm square. The buffer portion pattern 223 was 10 mm square. 7A is a top view, and FIG. 7B is a side sectional view.

  Next, Example 3 shows an example in which thermal imprinting is performed by a thermal imprinting apparatus using the imprinting Si mold produced in Example 1 and Example 2. For the substrate to be imprinted, a 4-inch silicon substrate coated with a thermosetting resist OEBR-1000 (trade name, manufactured by Tokyo Ohka Kogyo Co., Ltd.) with a thickness of 350 nm is used. Was coated in advance with a fluorine-based surface treatment agent EGC-1720 (trade name, manufactured by Sumitomo 3M Co., Ltd.) as a release agent. The thermal imprinting conditions were the same for all the above-described Si molds (pre-baking 110 ° C./1 minute, press pressure 10 MPa).

  Example 3 was evaluated. When the imprinted mold pattern and the transferred resist pattern were observed with a scanning electron microscope, the mold pattern and the resist pattern were not broken, and a good transfer pattern shape was obtained. The Si mold for imprinting in Examples 1 and 2 did not cause destruction of the mold pattern or resist pattern because the buffer portion was arranged.

It is a perspective view explaining the mold for imprint which provided the buffer part in the corner part of the pattern area of this invention. It is a perspective view explaining the mold for imprint which provided the buffer part in the whole outer peripheral part of the pattern area of this invention. (A)-(b) is a perspective view explaining the mold for imprint which provided the buffer part in the peripheral part of the pattern area of this invention. (A)-(c) is a sectional side view explaining the process in the case of imprinting using the imprint mold which has a buffer part of this invention. (A)-(d) is a sectional side view which shows the preparation process of Si mold for thermal imprinting which has a buffer part in Example 1 of this invention. BRIEF DESCRIPTION OF THE DRAWINGS It is drawing explaining the imprint mold of Example 1 of this invention, (a) is a top view, (b) is a sectional side view. It is drawing explaining the mold for imprint of Example 2 of this invention, (a) is a top view, (b) is a sectional side view. (A)-(e) is a sectional side view of the process which shows the pattern formation method by the conventional thermal imprint method. (A)-(e) is a sectional side view of the process which shows the pattern formation method by the conventional optical imprint method. (A)-(e) is sectional drawing explaining a mode that the conventional mold for imprint is imprinted on the sensitive board | substrate. It is a perspective view explaining the mold for imprint before the conventional imprint. It is a perspective view explaining the mold for imprint in which destruction occurred in a part of mold pattern after the conventional imprint.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 ... Imprint mold 101 ... Silicon substrate 102 ... Silicon oxide film 111 ... Silicon substrate 112 ... Resist 120 ... Quartz mold 130 ... Imprint mold 131 ... Silicon substrate 132 ... Resist 133 ... Pattern destruction 140 ... Imprint mold 141 ... support substrate 142 ... pattern area 150 ... imprint mold 151 ... support substrate 152 ... pattern area 153 ... pattern destruction area 160 ... imprint mold 161 ... support substrate 162 ... pattern area 163 ... buffer 170 ... imprint mold 171 ... Support substrate 172 ... Pattern area 173 ... Buffer portion 180 ... Imprint mold 181 ... Support substrate 182 ... Pattern area 183 ... Buffer portion 190 ... Imprint mold 191 ... Silico Substrate 192 ... resist 193 ... pattern area 194 ... buffer section 201 ... silicon substrate 202 ... resist 203 ... pattern area (resist)
204: Buffer area (resist)
205 ... Pattern area (silicon)
206: Buffer area (silicon)
210 ... Imprint mold 211 ... Support substrate 212 ... Pattern area 213 ... Buffer portion 214 ... Transfer area 220 ... Imprint mold 221 ... Support substrate 222 ... Pattern area 223 ... Buffer portion 224 ... Transfer area

Claims (2)

  An imprint mold for transferring a concavo-convex pattern formed on a mold to a resist layer on a substrate surface, wherein a buffer portion is arranged at a peripheral portion of the concavo-convex pattern area of the mold.   The imprint mold according to claim 1, wherein the buffer portion is disposed at least in a corner portion when the uneven pattern area is surrounded by a straight line.

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