JP2011091124A - Optical imprint method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical imprint method that measures a remaining film thickness of a dummy pattern so as to recognize a remaining film amount after imprint without cutting an effective region, to allow the same substrate, whose remaining film thickness is actually measured, to advance to etching being the next process, to feedback the remaining film amount to the etching conditions, and consequently, to reliably achieve stable processing. <P>SOLUTION: The optical imprint method uses a mold that has a pattern formed in an effective region, and a dummy pattern formed outside the effective region and having at least the same depth as that of the pattern. At least after the dummy pattern on the mold is transferred on a photosetting resist on a substrate, the remaining film thickness of the resist layer is measured from the depth corresponding to the dummy pattern. The remaining film on the resist layer corresponding to the pattern is removed on the basis of the measured remaining film thickness. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an optical imprint method, and more particularly to an optical imprint method using a pattern forming mold for transferring a mold having a desired pattern to a resist layer.

  In recent years, nanoimprint technology has attracted attention as a fine processing technology for transferring a fine structure on a mold onto a substrate to be transferred. This nanoimprint technology has a resolution on the order of several nanometers, and as a next-generation semiconductor technology, it is possible to process a three-dimensional structure at the wafer level, so a wide range of manufacturing technologies such as optical elements such as photonic crystals and biochips. Application to the field is expected.

  Such a nanoimprint method is a method in which a mold on which a pattern to be transferred is formed is pressed (pressed) against an imprint material (resist) layer applied on a substrate, and then a pattern formed on the resist layer on the mold. Several methods have been proposed in the past, such as a thermal imprint method mainly using a thermoplastic resist as an imprint material and a photo imprint method using a photo-curable resist. In Patent Document 1 as one of them, a concavo-convex pattern can be formed on a resist coated on a substrate, and the resist on which the concavo-convex pattern is formed is then applied to a substrate by a technique such as etching. An optical imprint method used as a mask for formation has been proposed.

  FIG. 9 is a cross-sectional view showing each step of a processing method using a conventional optical imprint method. As shown to (a) of the figure, the photocurable resist 2 is apply | coated to the board | substrate 1 of a to-be-processed object. Then, as shown in FIG. 5B, the substrate 1 and the mold 3 are aligned and pressed. Next, as shown in (c) of the figure, the photocurable resist 2 is cured by irradiating UV light from the UV light source 4. And as shown to (d) of the figure, the mold 3 and the photocurable resist 2 are peeled (release). Next, as shown in FIG. 5E, the remaining film 5 is removed by etching. Then, as shown in FIG. 5F, the substrate 1 to be processed is etched using the photocurable resist 2 from which the remaining film 5 has been removed as a mask.

  Here, when the remaining film shown in FIG. 5E is gradually removed, if the remaining film 5 is thick, the etching time becomes longer, and the pattern formed during the etching cannot be maintained and the shape is deteriorated. Problems arise. For example, as shown in FIG. 10, not only the pattern bottom 6 but also the pattern side wall 7 is etched during the etching in the step of removing the remaining film, as compared with the state before the etching shown in FIG. After the etching shown in FIG. 10B, there is a problem that the pattern width is narrowed from W1 to W2 (W1> W2). Therefore, it is desirable that the thickness of the remaining film be as thin and uniform as possible, but in that case, it is easily affected by warpage and waviness of the substrate and mold, and the thickness of the remaining film varies from imprint to imprint. It tends to occur. In this case, it is possible to adjust the etching conditions according to the thickness of the remaining film, but in this case, it is necessary to grasp the actual remaining film thickness of the substrate to be etched before etching. In other words, it is very important to grasp the amount of the remaining film before etching and determine the conditions for the next step.

  Therefore, in Patent Documents 2 and 3, the shape of the convex portion of the mold pattern is a rounded shape. Alternatively, it has been proposed to make the residual film uniform and thin by means such as defining the surface roughness, but how is the residual film thickness of the resist pattern transferred in the state before the actual etching? Means for grasping whether the residual film is formed is not mentioned, and it is not known whether the residual film before etching the residual film has a desired thickness.

  However, when actually measuring the residual film before etching, if the desired pattern pitch is a very narrow pitch of several tens to several hundreds of nanometers and the pattern depth is deep, the amount of the residual film is nondestructively transferred to the substrate. It is difficult to measure from the top. In general, a method is used in which an effective area of a substrate to which desired irregularities are transferred is cut by means such as dicing, the cross section is observed with an SEM or the like, and the dimension is measured from the cross section image. In this case, the substrate once the effective region has been cut cannot proceed to the remaining film etching, which is the next process, and the remaining film cannot be measured on the substrate that actually proceeds the etching process. Therefore, the residual film measurement substrate and the substrate that actually proceeds with the etching process are different. Even if imprinting is performed under the same conditions when the transfer pattern is a very fine pattern of several tens to several hundreds of nanometers, characteristics such as warpage and waviness of the substrate itself, inclination when the substrate is chucked on the imprint apparatus, etc. In some cases, the amount of the remaining film may change due to a slight difference. In this case, it is necessary to change the etching conditions according to the amount of the remaining film, but such a countermeasure cannot be performed. In particular, when the yield is not stable at the prototype stage of development or at the beginning of production, if there is a defect in the shape or characteristic evaluation in the evaluation after proceeding with all the processes once, about the board where the actual defect occurred Since the amount of remaining film in the processing process cannot be grasped, the amount of remaining film at the time of imprinting has a problem rather than the desired thickness. There is also a problem that it is impossible to isolate whether a defect has occurred and it takes a very long time to deal with it.

  The present invention is for solving these problems, by measuring the remaining film thickness of the dummy pattern, it is possible to grasp the amount of remaining film after imprinting without cutting the effective area, An optical imprint method that can proceed to the next process, etching, the same substrate where the remaining film thickness is actually measured, feed back the remaining film amount to the etching conditions, and realize stable processing. Can be provided.

  In order to solve the above problems, in the optical imprinting method of the present invention, a mold having a pattern formed in an effective region and a dummy pattern formed outside the effective region and having at least the same depth as the pattern. Use. After transferring at least the dummy pattern in the mold onto the photocurable resist on the substrate, the remaining film thickness of the resist layer is measured from the depth corresponding to the dummy pattern. Then, the remaining film in the resist layer corresponding to the pattern is removed based on the measured remaining film thickness. Therefore, by measuring the remaining film thickness of the dummy pattern outside the effective area of the mold, it is possible to grasp the remaining film amount after imprinting without cutting the effective area. As a result, the same substrate where the remaining film thickness was actually measured can be advanced to the next process, etching, and the amount of remaining film can be fed back to the etching conditions, ensuring stable processing. Of course, if a problem occurs in the final product, the cause can be dealt with quickly.

  Further, the surface area of the effective area where the pattern is formed and the surface area outside the effective area where the dummy pattern is formed are calculated, and the resist application amount when transferring the pattern and the dummy pattern is adjusted according to the surface area ratio. Therefore, even if the pattern pitch differs between the pattern and the dummy pattern, the remaining film thickness can be made the same, and by measuring the remaining film thickness in the dummy pattern, it is possible to reliably destroy the substrate. In addition, the remaining film thickness in the effective region can be grasped.

  Furthermore, the dummy pattern formed on the mold is transferred, and after measuring the remaining film thickness of the transferred dummy pattern, the pattern formed on the mold is transferred. Therefore, it is possible to prevent the resist fluidity from being different depending on the difference in pitch between the pattern and the dummy pattern, the substrate and the mold being inclined, and the difference in the thickness of the remaining film from occurring.

  Also, based on the result of measuring the residual film thickness of the dummy pattern, the resist coating amount is calculated so that the residual film has a desired thickness when the pattern is transferred, and the photocurability of the calculated resist coating amount is calculated. A resist is applied to the effective area of the pattern. Therefore, the resist coating amount at the time of pattern imprinting can be adjusted, and a desired remaining film thickness can be realized.

  Further, the mold is arranged so that the pattern direction of the dummy pattern crosses perpendicularly to the cutting position when cutting the chip as a product into a chip. Therefore, the remaining film thickness can be measured and grasped without cutting the effective area where the pattern is formed. Moreover, since the dummy pattern is formed so as to cross perpendicularly to the cutting position when cutting out each chip as a product from the substrate, the remaining film thickness can be obtained by observing the cross section without unnecessary cutting. .

  In addition, since the pattern shape of the dummy pattern is the same as the pattern shape of the effective area on which the pattern is formed, the residual film difference between the pattern and the dummy pattern at the time of transfer can be reduced, and the remaining film thickness of the dummy pattern By measuring the thickness, the remaining film thickness in the effective region can be reliably predicted.

  According to the optical imprinting method of the present invention, after transferring at least the dummy pattern in the mold onto the photocurable resist on the substrate, the residual film thickness of the resist layer is measured from the depth corresponding to the dummy pattern. Then, the remaining film in the resist layer corresponding to the pattern is removed based on the measured remaining film thickness. Therefore, the amount of remaining film after imprinting can be grasped without cutting the effective area, the same substrate on which the remaining film thickness is actually measured can be advanced to the next etching process, and the amount of remaining film can be reduced. It is possible to provide an optical imprint method that can be fed back to the etching conditions and can realize stable processing reliably.

It is a figure which shows the structure of the mold for pattern formation in the optical implant method of this invention. It is sectional drawing which shows the structure of an optical imprint apparatus. It is sectional drawing which shows the process of the optical imprint method which concerns on one embodiment of this invention. It is sectional drawing which shows another process of the optical imprint method of this Embodiment. It is a fragmentary sectional view which shows a mode when a board | substrate and a mold incline and a difference arises in the thickness of a remaining film in the same board | substrate. It is a fragmentary sectional view which shows the side part of the dummy pattern of the mold made into the taper structure previously. It is a top view which shows another structure of the mold for pattern formation in the optical implant method of this invention. It is a top view which shows the pattern arrangement | positioning which looked at the board | substrate after transcribe | transferring using the mold of FIG. 7 from the application surface side of the photocurable resist. It is sectional drawing which shows each process of the processing method using the conventional optical imprint method. It is sectional drawing which shows the process of removing the remaining film gradually in the conventional optical imprinting method.

  FIG. 1 is a diagram showing the configuration of a pattern forming mold in the optical implant method of the present invention. 4A is a plan view, and FIG. 4B is a cross-sectional view taken along the line A-A ′ in FIG. The method for producing the mold for forming the pattern shown in the figure is not limited, but it was produced by forming a desired concavo-convex pattern on a transparent quartz substrate by plasma etching. As shown in FIG. 1 (a), the effective region 11 of the pattern forming mold 10 used in the optical implant method of the present invention has irregularities of the line and space pattern 12 having a pitch of 200 nm, a line width of 100 nm, and a depth of 200 nm. Is formed. On the other hand, dummy patterns 14 are arranged at four locations in the non-effective area 13 other than the effective area 11. The dummy pattern 14 has a pitch of 10 μm and a line width of 5 μm. However, as can be seen from FIG. 1B, the depth of the dummy pattern 14 is set to 200 nm, which is the same as the line and space pattern 12 in the effective region 11.

  FIG. 2 is a cross-sectional view showing the configuration of the optical imprint apparatus. In the figure, the same reference numerals as those in FIG. 1 denote the same components. In the optical imprint apparatus 20 shown in the figure, a substrate 24 as a workpiece is vacuum-sucked and fixed by a wafer chuck 23 placed on a wafer stage 22 placed on a vibration isolation table 21. On the other hand, the mold 10 is held by a fixing jig 25 on the opposite side of the substrate 24. Further, a UV light source 26 for curing the resist is disposed on the back side of the mold 10. On the other hand, a dispenser 27 for applying a resist and an optical interference type film thickness meter 28 for measuring a residual film are attached to an arm 29 that can move between the mold 10 and the substrate 24 in a parallel direction. Can be moved.

  FIG. 3 is a cross-sectional view showing the steps of the optical imprint method according to the embodiment of the present invention. In the figure, the same reference numerals as those in FIGS. 1 and 2 denote the same components. Each cross-sectional view is an enlarged view of a portion surrounded by a dotted line in FIG. First, as shown in FIG. 3A, the dispenser 27 in the optical imprint apparatus 20 of FIG. 2 is moved to a desired position on the substrate 24 of the workpiece, and the photocurable resist 30 on the substrate 24 is moved. Apply. Here, in the pattern-forming mold 10, the line and space pattern 12 of the effective region 11 and the dummy pattern 14 of the non-effective region 13 have different pattern pitches, that is, different surface areas. The application amount is calculated so as to be the same, and the application amount of the photocurable resist 30 in the effective area 11 and the non-effective area 13 is adjusted, and the dispenser 27 is controlled to apply. Although there are mainly a spin coating method and a dispense (inkjet) method for applying the photocurable resist 30 in the photoimprint method, it is difficult to adjust the coating amount depending on the location of the substrate 24 in the spin coating method. With the dispensing method used in the present embodiment, the coating amount of the photocurable resist 30 can be changed between the effective region 11 and the non-effective region 13 by controlling the coating amount of the photocurable resist 30. Then, as shown in FIG. 3B, the substrate 24 and the mold 10 are pressed, and then the photocurable resist 30 is cured by light irradiation from a UV light source (not shown). Next, as shown in FIG. 3C, the mold is moved above the mold 10 to release the photocurable resist 30 from the mold 10. Then, as shown in FIG. 3D, the optical interference film thickness meter 28 is moved onto the dummy pattern 14 in the ineffective area 13 to measure the thickness of the remaining film in the dummy pattern 14 in the ineffective area 13. To do. In the present embodiment, the thickness of the remaining film of the dummy pattern 14 is measured in contact with the optical interference film pressure gauge 28 that can narrow the beam spot diameter to 5 μm.

  As described above, the coating amount of the photocurable resist 30 is adjusted so that the remaining film in the line and space pattern 12 in the effective area 11 after imprinting and the dummy pattern 14 in the ineffective area 13 are the same. Therefore, the thickness of the remaining film in the line and space pattern 12 in the effective region 11 can be grasped without destroying the substrate 24. Therefore, the substrate 24 itself, whose thickness of the remaining film is known, can be advanced to the next process (not shown), and the thickness of the remaining film can be reflected in the etching conditions at that time. As a result, stable machining can be realized reliably, and even if a defect occurs after etching, the cause can be quickly dealt with. The shape of the dummy pattern 14 in the present invention only needs to be the same as the line and space pattern of the effective area in the pattern depth. In the case of the optical interference type film thickness meter used in this form, a line width of at least a minimum spot diameter of 5 μm is sufficient. In addition, the measurement of the remaining film may be performed after the substrate 24 is detached from the imprint apparatus 20, but in that case, care must be taken that foreign matter adheres to the substrate 24 at the time of measurement. When the thickness measurement of the remaining film can be performed in the imprint apparatus 20 as in the present embodiment, it is not necessary to handle the substrate 24 for the measurement, and the possibility of foreign matter adhesion as described above is reduced. Can do. Further, as in the present embodiment, by providing a plurality of dummy patterns and measuring the thicknesses of the remaining films, the unevenness in transfer during imprinting caused by the inclination of the substrate 24 or the mold 10 is grasped. be able to. In the present embodiment, four dummy patterns 14 are provided in the non-effective area 13 on the outer periphery of the effective area 11.

  FIG. 4 is a cross-sectional view showing another process of the optical imprint method according to the present embodiment. Here, the imprint apparatus 20 of FIG. 2 was used as in FIG. First, as shown in FIG. 4A, a photocurable resist 30 is applied only to a region of the substrate 24 corresponding to the dummy pattern 14 in the ineffective region 13, and as shown in FIG. First, the substrate 24 and a mold (not shown) are pressed to transfer the dummy pattern 14, and the thickness of the remaining film of the dummy pattern 14 is measured by the optical interference type film thickness meter 28. Then, as shown in FIG. 4C, based on the measurement result of the remaining film thickness of the dummy pattern 14, the photo-curing property in which the coating amount is adjusted so that the effective area 11 has a desired film thickness. A resist 30 is applied, and the line and space pattern 12 of the effective area 11 is transferred as shown in FIG.

  Here, when patterns with different pitches are mixed, such as a line-and-space pattern in the effective area in the mold and a dummy pattern in the ineffective area, if the imprint is performed under the same conditions, the pattern with the larger pitch and the main pattern In the case of the embodiment, the photocurable resist is more likely to flow in the dummy pattern. Therefore, as shown in FIG. 5, the substrate 24 and the mold 10 may be inclined and a difference may occur in the thickness of the remaining film within the same substrate. As a result, even if the thickness of the remaining film of the dummy pattern is measured, it becomes impossible to accurately grasp the thickness of the remaining film in the effective region. Therefore, in this embodiment, the same substrate and mold are used, and both are removed from the wafer chuck 23 and the fixing jig 25 of the optical imprint apparatus in FIG. Since the line and space pattern is imprinted separately, the thickness of the dummy pattern remaining film in the ineffective region does not occur without the inclination based on the pitch difference between the dummy pattern and the line and space pattern as described above. By measuring the thickness, it is possible to accurately grasp the remaining film of the line and space pattern in the effective region.

  In addition, after measuring the thickness of the remaining film, the amount of photocurable resist applied can be adjusted based on the result, and the line and space pattern can be transferred to the effective area. The thickness of the remaining film of the line and space pattern can be arbitrarily controlled as appropriate. In the present embodiment, as shown in FIGS. 4C and 4D, when the line and space pattern is transferred to the effective area, the photo-curable resist in which the dummy pattern is already formed is cured in the ineffective area. Therefore, when transferring the line-and-space pattern to the effective area, there is a concern that the dummy pattern of the mold collides with the already cured photo-curable resist, and the pattern of the dummy pattern portion is broken. Actually, the substrate 24 and the mold 10 are in a chucked state, and the fixed state is not changed. Further, as shown in FIG. 6A, the photocurable resist is reduced by the curing shrinkage at the time of solidification. Since there is a space portion 31 in the mold and the photo-curing resist that has already been cured by the pattern, it does not collide. As shown in FIG. 6 (b), when the dummy pattern is transferred to the side surface portion of the dummy pattern in advance and the dummy pattern is transferred, the thickness of the dummy pattern is determined in advance from the desired remaining film thickness in the effective region. By reducing the thickness of the remaining film, the above-described space portion 31 can be surely formed, and collision between the dummy pattern and the already cured photocurable resist can be prevented.

  FIG. 7 is a plan view showing another configuration of the mold for pattern formation in the optical implant method of the present invention. In the figure, the same reference numerals as those in FIG. 1 denote the same components. As shown in the figure, the mold 10 has four ineffective areas 13 in which dummy patterns 14 are formed at positions protruding from the rectangular area of the effective area 11 in which the line and space pattern 12 is formed. Has been.

  FIG. 8 is a plan view showing a pattern arrangement when the substrate after being transferred using the mold of FIG. 7 is viewed from the coated surface side of the photocurable resist. In this example, the product is arranged as nine chips in one substrate 24 so that the product can be cut out. 8A is a cutting position when each chip is cut out from the substrate 24, and one chip surrounded by a dotted line in FIG. 8B is shown in FIG. Cutting is as shown in (b). Since the pattern of the dummy pattern in the non-effective area is formed so as to be orthogonal to the cut surface, as shown in FIG. 8B, the dummy pattern of the non-effective area 13 in each chip. The cut surface of the dummy pattern is exposed at the time of cutting. That is, in the present embodiment, when the product chip is cut out from the substrate 24, the cut surface of the dummy pattern is exposed, and by observing the cut surface with an SEM or the like, the remaining film of the effective region is not cut. Can be measured. In this case, since the effective area is not cut, it is possible to proceed to the next process such as etching as it is. Furthermore, the cross-sectional shape after etching can also be confirmed without cutting the effective region. In this embodiment, since the thickness of the remaining film is measured by cross-sectional observation, there is no restriction on the pattern shape, and it can be made exactly the same shape as the pattern in the effective region. In other words, measure the residual film of the dummy pattern without having to consider the difference in the residual film between the dummy pattern in the non-effective area and the pattern shape of the line and space pattern in the effective area. It is possible to accurately grasp the remaining film of the line and space pattern in the effective area.

  In the present invention, it is sufficient that dummy patterns are formed in the effective area and the ineffective area outside the effective area on the same mold, and the in-mold layout is limited to that shown in the above embodiment. Needless to say, there is nothing to do.

  The present invention is not limited to the above-described embodiment, and various modifications, substitutions, and applications are possible as long as they are described in the scope of the claims.

10; mold, 11; effective area,
12; line and space pattern; 13; non-effective area;
14; dummy pattern, 20; optical imprint apparatus,
21; slow shaking table, 22; wafer stage,
23; Wafer chuck, 24; Substrate, 25; Fixing jig,
26; UV light source, 27; dispenser, 28; optical interference film thickness meter,
29; arm, 30; photo-curable resist, 31; space portion.

JP 2000-194142 A JP 2008-287805 A JP 2009-004066 A

Claims (6)

A photocurable resist is applied on a substrate of a workpiece, and then a pattern forming surface of a mold composed of a light transmissive member on which a desired uneven pattern is formed is brought into contact with the back surface of the pattern forming surface of the mold. In the photoimprint method of transferring the pattern of the mold to a resist layer coated on a substrate by irradiating light from the side to cure the photocurable resist,
Using the mold having the pattern formed in the effective region and the dummy pattern formed outside the effective region and having at least the same depth as the pattern, at least the dummy pattern is a photocurable resist on the substrate. After the transfer, the residual film thickness of the resist layer is measured from the depth corresponding to the dummy pattern, and the residual film in the resist layer corresponding to the pattern is removed based on the measured residual film thickness. An optical imprint method characterized by the above.   Calculate the surface area of the effective area where the pattern is formed and the surface area outside the effective area where the dummy pattern is formed, and adjust the resist coating amount when transferring the pattern and the dummy pattern according to the surface area ratio The optical imprint method according to claim 1, wherein:   The dummy pattern formed on the mold is transferred, and after measuring the remaining film thickness of the transferred dummy pattern, the pattern formed on the mold is transferred. 3. The optical imprint method according to 1 or 2.   Based on the result of measuring the residual film thickness of the dummy pattern, the resist coating amount is calculated so that the residual film has a desired thickness when the pattern is transferred, and the photo-curing of the calculated resist coating amount is performed. 4. The optical imprint method according to claim 3, wherein a resist is applied to an effective area of the pattern.   The said mold is arrange | positioned so that the pattern direction of the said dummy pattern may cross | intersect orthogonally to the cutting-out position when cutting out to a chip | tip as a product from a board | substrate, The any one of Claims 1-4 characterized by the above-mentioned. Optical imprint method.   6. The optical imprint method according to claim 5, wherein a pattern shape of the dummy pattern is the same pattern as a pattern shape of an effective area on which the pattern is formed.

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