Patent Publication Number: US-2011062632-A1

Title: Template with identification mark and method of manufacturing the same

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2009-214810, filed Sep. 16, 2009; the entire contents of which are incorporated herein by reference. 
     FIELD 
     Embodiments described herein relate generally to a template with an identification mark to be used when forming patterns by using step and flash imprint lithography (SFIL), and a method of manufacturing the same. 
     BACKGROUND 
     Recently, SFIL is attracting attention as a pattern transfer technique of micropatterning semiconductor integrated circuits. SFIL is sometimes unable to perform accurate pattern transfer due to, e.g., wear corresponding to the use frequency, clogging of pattern recesses, and breakage. Therefore, a general procedure is to prepare a plurality of templates having the same shape, and switch templates in accordance with a defined number of times of use, or the occurrence of transfer defects. 
     In a method using electron-beam lithography in the manufacture of templates, however, a very long writing time is necessary to manufacture only one template. 
     Accordingly, a general approach is to prepare a plurality of templates having the same shape by manufacturing a plurality of child templates by imprinting by using a template manufactured by electron-beam lithography as a parent template, and form patterns on a substrate by using the child template. 
     On the other hand, in the manufacturing process of forming patterns by using SFIL, a certain unique mark that makes a template to be used identifiable is desirably given to the template in order to manage the type, log, and the like of the template. In a method of marking an ID by additionally processing a template after it is manufactured, however, dust produced during the additional processing may adhere on patterns, or the work of the additional processing itself may damage patterns on the template. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view showing an outline of the arrangement of a template with an identification mark according to the first embodiment; 
         FIG. 2  is a sectional view taken along a line A-A′ in  FIG. 1 , which explains the outline of the arrangement of the template with an identification mark according to the first embodiment; 
         FIG. 3  is a plan view showing the outline of the arrangement of the template with an identification mark according to the first embodiment; 
         FIG. 4  is a sectional view showing the structure of a processing stage for additionally processing the template; 
         FIG. 5  is a plan view showing the structure of the processing stage for additionally processing the template; 
         FIG. 6  is a sectional view showing the way the template is additionally processed by using a laser processor; 
         FIGS. 7A ,  7 B, and  7 C are sectional views showing the shapes of engraved patterns; 
         FIGS. 8A ,  8 B,  8 C, and  8 D are sectional views showing pattern transfer steps using SFIL; 
         FIGS. 9A ,  9 B,  9 C,  9 D, and  9 E are sectional views showing steps of manufacturing a pattern formation template by using electron-beam lithography; and 
         FIG. 10  is a plan view showing an outline of the arrangement of a template with an identification mark according to the second embodiment. 
     
    
    
     DETAILED DESCRIPTION 
     In general, according to one embodiment, a template with an identification mark for use in SFIL includes a pattern formation template including a main pattern region where a desired pattern is formed as a convex/concave pattern on the upper surface of a light-transmitting substrate, and an identification mark that is formed on the lower surface of the substrate to partially overlap the main pattern region, and makes the template identifiable. 
     The embodiments will be explained below with reference to the accompanying drawing. 
     First Embodiment 
       FIG. 1 ,  FIG. 2 , and  FIG. 3  are views for explaining an outline of the arrangement of a template with an identification mark according to the first embodiment.  FIG. 1  is a perspective view,  FIG. 2  is a sectional view taken along a line A-A′ in  FIG. 1 , and  FIG. 3  is a plan view in which the template is viewed from the lower surface. 
     As shown in  FIG. 1  and  FIG. 2 , the surface of a substrate  11  made of a light-transmitting material such as quartz is divided into a main pattern region  12  for forming a desired pattern, and a peripheral region  13  surrounding the main pattern region  12 . In the main pattern region  12 , a desired pattern such as an LSI pattern is formed as a convex/concave pattern. A portion of the peripheral region  13  is entirely etched to make the surface lower than the main pattern region  12 . Note that it is not always necessary to make a portion of the peripheral region  13  lower than the main pattern region  12 , and the whole peripheral region  13  may have the same height as that of the main pattern region  12 . 
     As shown in  FIG. 3 , a unique identification mark  15  for identifying the type, log, and the like of a template is formed on the lower surface of the substrate  11 . The mark  15  is, e.g., a character string, and formed by partially engraving the lower surface of the substrate  11 . Also, the mark  15  is formed in a position interfering with the main pattern region  12 , i.e., in a region partially overlapping the main pattern region  12 . Note that reference numeral  16  in  FIG. 3  indicates a transmitted image of the pattern formed on the upper surface of the template. 
     A method of manufacturing the template with an identification mark according to the first embodiment will be explained below. 
     In the first embodiment, after a pattern formation template for use in SFIL is manufactured, an identification mark that makes the template identifiable is marked on the lower surface of the template by using a laser processor. More specifically, the identification mark is formed in a region including a part of or the whole region where a projected pattern exists on the lower surface side when viewed from the upper surface side on which the pattern is formed on the template. 
     Note that the existing techniques are used as a method of manufacturing the pattern formation template and a pattern formation method using SFIL, and these methods will be described later. 
     First, a pattern formation template on which a desired pattern is formed is prepared. Then, as shown in  FIG. 4 , a template  10  is held on a processing stage  20  with the pattern formation surface facing up. That is, the template  10  is placed on the processing stage  20  having an opening slightly smaller than the template  10  with the lower surface of the template  10  facing down. Note that a holding jig  30  is brought into contact with only the lower surface side when viewed from the pattern formation surface of the template  10 . 
     Note also that an O-ring is formed as the template holding jig  30  on the surface of the processing stage  20  so as to airtightly seal the opening of the processing stage  20  with the template  10  being placed on it. That is, it is desirable to adjust the shape and function of the holding jig  30  so that the template lower surface as a surface to be processed and the template upper surface on which the pattern exists are isolated as much as possible. 
     For example, the holding jig  30  shown in  FIG. 5  has a shape obtained by forming a highly elastic resin having no air permeability into a rectangular ring slightly smaller than the outer circumference of the template  10 , and the template  10  to be additionally processed is placed on the holding jig  30  with the lower surface of the template  10  facing down. Accordingly, the holding jig  30  is brought into tight contact with the template  10  by its own weight, and improves the isolation between the upper and lower surfaces of the template  10 . 
     After the template  10  is held on the processing stage  20  as described above, as shown in  FIG. 6 , the lower surface side of the substrate  11  of the template  10  is irradiated with laser light by using a laser processor  40 , thereby selectively processing the surface shape of the lower surface of the substrate  11 . In this manner, the identification mark  15  that makes the template  10  identifiable is formed. 
     In this embodiment, the mark  15  is formed by engraving the lower surface of the substrate  11  by the laser light. In this process, the bottom of the engraved portion is desirably processed to have a surface roughness with which the light transmittance of a mark portion formed by the engraving and that of a non-mark portion are almost the same. The “light” herein mentioned is the same as light to be emitted to cure a photocurable resin when forming a pattern by SFIL by using the template  10 . 
     More specifically, as shown in  FIG. 7A , to avoid unwanted scattering and attenuation, the processed side surfaces are desirably vertical, and the processed bottom surface is desirably parallel to the upper surface. This is so because if the side surfaces incline as shown in  FIG. 7B , or if the bottom surface is roughened as shown in  FIG. 7C , light to be used in SFIL is irregularly reflected or scattered, so the existence of the mark  15  exerts an adverse effect on the pattern. 
     Next, the position of the mark  15  that is formed by the additional processing and makes the template  10  identifiable will be explained. The mark  15  formed by the additional processing is generally transparent to the irradiating light for curing the photocurable resin, which is used in the pattern formation step using SFIL. Therefore, the existence of the mark  15  does not obstruct the curing of the photocurable resin. Accordingly, the position of the mark  15  may interfere with the main pattern region where the pattern to be transferred is formed. As shown in  FIG. 3 , therefore, the identification mark  15  is formed by the additional processing so that a part of or the whole mark  15  is included in a region (on the lower surface) corresponding to the region where the transfer target pattern is formed on the template upper surface. 
     When a pattern is formed on a substrate by SFIL using the template with an identification mark on which the mark  15  capable of identification is formed, the pattern on the template  10  can be formed on a desired substrate without any influence of the mark formed by the additional processing. Since the identification mark  15  can be given with a sufficient space being secured, detailed management of the template  10  is possible. 
     An example of SFIL using the template with an identification mark will be explained below.  FIGS. 8A ,  8 B,  8 C, and  8 D illustrate an example of the procedure of a pattern formation method using SFIL. 
     First, as shown in  FIG. 8A , a semiconductor substrate  50  as a target of pattern processing is coated with a photocurable resin composition  51 . Subsequently, a necessary template  70  is selected by checking the identification mark  15  from among a plurality of prepared templates  70  with identification marks. As shown in  FIG. 8B , the selected template  70  is pushed against the photocurable resin composition  51 . The substrate is left to stand in this state until the photocurable resin  51  fills recesses of the template  10  by capillary phenomenon. 
     Then, as shown in  FIG. 8C , the lower surface side of the template  70  is irradiated with light (e.g., an i line of 365 nm) emitted from a light source  60 , thereby curing the photocurable resin composition  51 . Finally, as shown in  FIG. 8D , the template  70  is separated from the substrate  50 . Consequently, a pattern is formed by the cured resin on the substrate  50  such that projections and recesses are inverted from those of the pattern formed on the template  70 . A pattern can be formed on the substrate  50  by performing processing such as etching by using the pattern of the resin composition  51  as a mask. 
     An example of a method of manufacturing a pattern formation template by using electron-beam lithography will be explained below.  FIGS. 9A ,  9 B,  9 C,  9 D, and  9 E illustrate an example of the procedure of manufacturing a pattern formation template for use in SFIL. 
     First, as shown in  FIG. 9A , a template substrate  91  for manufacturing a template is prepared. Synthetic quartz is generally used as the material of the template substrate  91 . This is so because the photocurable resin is cured by irradiating the pattern lower surface with light in the photocurable resin curing step, so the material must be transparent to the irradiating light. Subsequently, a Cr film  92  is formed on the surface of the template substrate  91  by sputtering, and the surface of the Cr film  92  is coated with a resist  93  sensitive to an electron beam. 
     Then, as shown in  FIG. 9B , an electron-beam exposure apparatus is used to write a desired pattern on the prepared template substrate  91 , and selectively expose the resist  93  as a template substrate surface layer to light. As shown in  FIG. 9C , the template substrate  91  having undergone the writing process is developed, and the resist  93  is removed from the portions exposed to the electron beam, thereby forming a resist pattern. 
     Subsequently, as shown in  FIG. 9D , the Cr film  92  is etched by, e.g., RIE (Reactive Ion Etching) by using the pattern of the resist  93  as a mask, and the remaining resist  93  is removed by a separating process. 
     As shown in  FIG. 9E , the quartz substrate  91  is engraved to a desired depth by, e.g., RIE by using the patterned Cr film  92  as a mask. After that, the Cr film  92  on the surface is removed, thereby manufacturing a pattern formation template  90  having the desired pattern formed into a convex/concave pattern on the template substrate  91 . 
     The above-mentioned pattern formation procedure using SFIL is performed by using the pattern formation template  90  manufactured following the procedure as described above. Consequently, the pattern formed on the template  90  is transferred onto a desired substrate by the cured photocurable resin with projections and recesses of the pattern being inverted. After that, processing such as etching is performed on the substrate by using the photocurable resin pattern formed on the substrate as a mask. This makes it possible to form the desired pattern on the substrate without any influence of the identification mark  15  formed by additional processing. 
     The template manufacturing method using electron-beam lithography disclosed in the above-mentioned template manufacturing procedure requires a very long writing time to write a pattern by using an electron beam. For example, a writing time of about a month is required to write a pattern in which a 65 mm×65 mm region is filled with lines and spaces at a half pitch of 20 nm, by using a presently widely used Gaussian-beam lithography apparatus having an acceleration voltage of 100 keV. 
     In this embodiment, therefore, after the template  90  is manufactured by electron-beam lithography, the template  90  is used as a parent template to manufacture a plurality of child templates by the imprinting method as shown in  FIGS. 8A ,  8 B,  8 C, and  8 D, or a plurality of grandchild templates are further manufactured from the child templates, thereby preparing a plurality of templates  10  having the same shape. A pattern is formed on a substrate by using the child template or grandchild template. 
     The formation of the above-mentioned identification mark  15  is effective in manufacturing a large number of templates  10  as described above. That is, after the template  10  to be used in SFIL is manufactured, the manufactured template  10  is additionally processed to form the identification mark  15  that makes the template  10  identifiable, on a surface other than the pattern formation surface. Since the surface other than the pattern surface is additionally processed, it is possible to minimize the risk that the additional processing inflicts damage to the pattern portion. Also, pattern processing by imprinting is not affected even when the mark  15  is formed in a position that three-dimensionally interferes with the pattern position. This makes it possible to increase the degrees of freedom of the mark position and mark size. 
     In this embodiment as described above, the pattern formation template  10  can be identified regardless of whether it is a child template or grandchild template, without inflicting any damage to the pattern formed on the template  10 . This facilitates production management. In addition, since the formation region of the identification mark  15  is wider than that in the conventional method, the template  10  can be given more information than that in the conventional method. This makes the management more detailed than that in the conventional method. 
     Second Embodiment 
       FIG. 10  is a plan view showing an outline of the arrangement of a template with an identification mark according to the second embodiment. Note that the same reference numerals as in  FIG. 3  denote the same parts, and a repetitive explanation will be omitted. 
     The second embodiment is directed to a method by which a template  10  for use in SFIL is manufactured, and a mark  19  that makes the template  10  identifiable is formed by using paint on the lower surface side when viewed from the pattern formation side of the template  10 . Note that the existing technique is used as a method of manufacturing the pattern formation template  10 , and a detailed description of the method will be omitted in this embodiment. 
     First, the pattern formation template  10  on which a desired pattern is formed is prepared. Then, the template  10  is held on a processing stage  20  as shown in  FIG. 4  with the pattern formation surface facing up. The structure of the processing stage  20  and the method of placing the template  10  on the processing stage  20  are the same as in the first embodiment, and a repetitive explanation will be omitted. The mark  19  that makes the template  10  identifiable is formed by using paint on the lower surface of the template  10  placed on the processing stage  20 . As the method of forming the mark  19  by paint, it is possible to use, e.g., a pattern formation method performed by inkjet paint coating extensively used in printing methods. 
     The paint to be used is desirably paint that generally transmits the wavelength of light emitted to cure the photocurable resin when performing pattern transfer by SFIL. 
     When using the paint having the feature as described above, the existence of the mark  19  dose not obstruct the curing of the photocurable resin when performing pattern transfer by SFIL. Therefore, the position of the mark  19  may interfere with a region where a pattern to be transferred exists. Accordingly, the mark  19  can be formed by additional processing in a region where a part of or the whole mark  19  is included in a region where a pattern to be transferred is formed on the template surface. It is also possible to select a position where no region to be transferred is formed on the template surface, and form the mark  19  by additional processing. 
     In this embodiment as described above, when forming a pattern on a substrate by SFIL by using the template  10  on which the mark  19  capable of identification is formed, the pattern on the template  10  can be formed on a desired substrate without any influence of the mark  19  formed by additional processing. Therefore, the same effects as those of the first embodiment described previously can be obtained. 
     (Modifications) 
     Note that the present invention is not limited to each embodiment described above. Although quartz is used as the template substrate in each embodiment, the template substrate is not necessarily limited to quartz, and it is possible to use any material having a sufficient transmittance to the wavelength of light to be used in SFIL. 
     The identification mark is not limited to an arbitrary character string. The identification mark may be a one-dimensional barcode mark or two-dimensional barcode mark, and can also be formed by combining them. Also, the depth of grooves formed as the identification mark by engraving a substrate may appropriately be determined in accordance with the specifications. Furthermore, the paint to be used as the identification mark need only be paint that has a sufficient transmittance to the wavelength of light to be used in SFIL, and one that does not obstruct the curing of the photocurable resin. 
     While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.