Abstract:
A processing apparatus for transferring a relief pattern on a mold to a resist on a substrate through a compression of the mold against the resist, includes a supplier for supplying the resist between the substrate and the mold, and a recovery unit for recovering the resist.

Description:
[0001]    This application is a continuation of prior application Ser. No. 11/092,228, filed Mar. 28, 2005, to which priority under 35 U.S.C. §120 is claimed. This application claims a benefit of priority based on Japanese Patent Application No. 2004-096991, filed on Mar. 29, 2004, which is hereby incorporated by reference herein in its entirety as if fully set forth herein. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    The present invention relates generally to processing apparatuses, and more particularly to a processing apparatus that transfers a pattern on a mold as an original onto a substrate such as a wafer. The present invention is particularly suitable for a processing apparatus that uses the nanoimprint technology. 
         [0003]    The nanoimprint technology is one alternative to the photolithography that uses the ultraviolet (“UV”) light, X-rays and electron beams to form fine patterns for semiconductor devices. The nanoimprint presses (or stamps) a model (or a mold), on which a fine pattern has been formed by the electron-beam exposure etc., against a substrate such as a wafer to which a resinous material (resist) is applied, thereby transferring the pattern onto the resist. See, for example, S. Y. Chou, et al., Science, Vol. 272 pp. 85-87, 5 Apr. 1996. It is already demonstrated that the nanoimprint can transfer a fine shape of about 10 nm, and attracts attention especially as a fine periodic pattern forming means for magnetic recording media. Active researches and developments are globally under way. 
         [0004]    The nanoimprint sometimes uses the vacuum environment to prevent intrusions of air bubbles between a mold and a substrate. Methods that facilitate the resist flow at the press time include a (heat cycle) method of heating polymer as the resist more above the glass transition temperature for transfer, and a (photo-curing) method of exposing and curing the UV curable resin as the resist while pressing it with a transparent mold, and of releasing the mold. 
         [0005]    A manufacture of semiconductor integrated circuits (“ICs”) requires an overlay that transfers the next pattern with a precise alignment with a circuit pattern already formed on a substrate. The heat cycle method heats the resist, causes the substrate and mold to thermally expand with a temperature rise, and has difficulties in maintaining the overlay accuracy. Accordingly, the photo-curing method, in which temperature control is relatively easy, is more suitable in applying the nanoimprint to the manufacture of the semiconductor ICs. 
         [0006]    For the minimum critical dimension (“CD”) of a semiconductor IC pattern of 100 nm or less, the resist requires a low-viscosity material to fully fill in the mold&#39;s fine structure. A nanoimprint apparatus typically successively transfers a pattern onto a wafer surface in a step-and-repeat manner. Here, the “step-and-repeat manner” is one mode of exposure method that moves a wafer stepwise to an exposure area for the next shot every shot of cell projection onto the wafer. However, due to the low viscosity of the resist, it is difficult to previously apply resist to a substrate, transport and mount the substrate as in an exposure apparatus. One proposed method drops a proper quantity every time the mold is pressed in transferring each shot. See, for example, M. Colburn, S. Johnson, M. Stewart, S. Damle, T. Bailey, B. Choi, M. Wedlake, T. Michaelson, S. V. Sreenivasan, J. G. Ekerdt and C. G. Willson. “Step and Flash Imprint Lithography: A new approach to high resolution patterning.” Proc. SPIE 3676 (I): 379 (1999). 
         [0007]    The mold includes plural patterns for plural chips, and generally has a rectangular shape, whereas a wafer has a circular shape. Therefore, in transferring a mold pattern matrix-wise onto a wafer, the mold outstretches the wafer&#39;s peripheral shot (referred to as a “peripheral shot” hereinafter) that is smaller than the mold size, thus resulting in a partial transfer of the mold pattern. The partial transfer of the mold pattern to the peripheral area is economical and beneficial because some of the plural chip patterns in the mold are transferred. 
         [0008]    However, the low-viscosity resist flows out from the peripheral shot, and contaminates the processing apparatus and the wafer chuck for fixing the wafer. Thus, uneconomically, the prior art cannot transfer the mold pattern to the peripheral shot. 
       BRIEF SUMMARY OF THE INVENTION 
       [0009]    The present invention is directed to a processing apparatus that has good overlay accuracy, fine processing and economical efficiency, and can prevent resist&#39;s contaminations. 
         [0010]    A processing apparatus according to one aspect of the present invention for transferring a relief pattern on a mold to a resist on a substrate through a compression of the mold against the resist, includes a supplier for supplying the resist between the substrate and the mold, and a recovery unit for recovering the resist. 
         [0011]    A processing apparatus according to another aspect of the present invention for transferring a relief pattern on a mold to a resist on a substrate through a compression of the mold against the resist, includes a support for supporting the substrate arranged on a more upstream side than the mold in terms of a gravitational direction. 
         [0012]    A device manufacturing method according to still another aspect of this invention including the steps of transferring a pattern onto resist on a substrate using the above processing apparatus, and etching the substrate. Claims for the device manufacturing method that exhibits operations similar to those of the above processing apparatus cover devices as their intermediate products and finished products. Such products include semiconductor chips, CCDs, LCDs, magnetic sensors, thin-film magnetic heads, etc. 
         [0013]    Other objects and further features of the present invention will become readily apparent from the following description of the embodiments with reference to accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0014]      FIG. 1  is a schematic sectional view of a processing apparatus according to a first embodiment of this invention. 
           [0015]      FIG. 2  is an enlarged sectional view of a resist recovery means for the processing apparatus shown in  FIG. 1 . 
           [0016]      FIGS. 3A and 3B  are schematic plan views showing a shot layout of a wafer. 
           [0017]      FIG. 4  is a schematic sectional view showing a resist recovery means applicable to a processing apparatus as a second embodiment of this invention. 
           [0018]      FIG. 5  is a schematic sectional view showing a resist recovery means applicable to a processing apparatus as a third embodiment of this invention. 
           [0019]      FIG. 6  is a schematic sectional view of a processing apparatus as a fourth embodiment of this invention. 
           [0020]      FIG. 7  is an enlarged sectional view of a resist recovery means for the processing apparatus shown in  FIG. 6 . 
           [0021]      FIG. 8  is a flowchart for explaining a method for manufacturing a device (semiconductor chips such as ICs, LSIs, and the like, LCDs, CCDs, etc.) using the above processing apparatus. 
           [0022]      FIG. 9  is a detailed flowchart for Step  4  shown in  FIG. 8 . 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0023]    Referring now to the accompanying drawings, a description will be given of a photo-curing nanoimprint apparatus  10  according to a first embodiment of this invention. In each figure, the same reference numeral denotes the same element, and a duplicate description thereof will be omitted. Here,  FIG. 1  is a schematic sectional view of the nanoimprint apparatus  10 . 
         [0024]    The nanoimprint apparatus  10  has a photo-curing means, a mold  11 , a mold driver, a wafer  21 , a wafer driver, a resist supply means, a resist recovery means, and other mechanisms. 
         [0025]    The photo-curing means is a means that irradiates the UV light to a resist  42  via the mold  11 , having a light source  15  and an illumination optical system  14 . The light source  15  includes a mercury lamp (not shown), and the like that generate the UV light. The illumination optical system  14  includes lenses and apertures that shape the illumination light for exposing and hardening the resist and irradiating a resist surface, a shutter that switches between a light irradiation state and a light shielding state. 
         [0026]    The mold  11  has a fine structure to be transferred, and is made of a transparent material such that it transmits the exposure light for hardening resist. 
         [0027]    The mold driver includes a mold chuck  12  for holding the mold  11  on the apparatus  10 , and an imprint mechanism  13  as a driver that presses the mold  11  downward. The imprint mechanism  13  moves the mold  11  longitudinally, and controls an orientation of the mold  11  and an alignment between the mold  11  and the wafer  21  for close contact between the mold transfer surface and the wafer  21 . 
         [0028]    The wafer  21  is an object onto which a pattern on the mold  11  is transferred, and which is made into a semiconductor IC through the subsequent steps. 
         [0029]    The wafer driver includes a wafer chuck  22  that holds the wafer  21 , and a wafer stage  23  for adjusting the position and orientation of the wafer chuck  22 . The wafer stage  23  moves in XY plane directions, and enables the whole area of the wafer to be transferred. The wafer stage  23  provides a precise alignment, and overlay of a fine pattern. The wafer stage  23  serves to position the wafer  21 , and adjust the orientation of the wafer  21 &#39;s surface. 
         [0030]    The resist supply means includes a tank  31  that stores resists  41 ,  42  that have not yet received the UV light or have not yet been cured, a nozzle  32  for dropping the resist on the wafer surface, and a valve (not shown) that drops or stops dropping the resist  42  from the nozzle  32 . 
         [0031]    The resist recovery means includes a recovery port  33  and a recovery unit  34 . The recovery port  33  is provided in the surface of the wafer chuck  22  to attract and recover the resist  42  spilt from the wafer surface. The recovery unit  34  includes a vacuum pump, a filter, etc. (any of them not shown), and recovers the resist by setting the downstream of the recovery port to the negative pressure. 
         [0032]    Other mechanisms include a stool  24 , a damper  25 , a frame  26 , an alignment scope  27 , and a reference mark table  28 . The stool  24  supports the whole apparatus  10  as well as forming a reference plane for the wafer stage  23  to move along. The damper  25  serves to eliminate vibrations from the floor, supporting the stool  24 . The frame  26  supports components from the light source  15  to the mold  11  above the wafer  21 . The alignment scope  27  measures a position of an alignment mark on the wafer  21 , and positions the wafer stage  23  based on the result. The reference mark table  28  has a reference mark used for an alignment between the coordinate of the alignment scope  27  and the coordinate of the wafer stage  23 . 
         [0033]    In operation, the wafer  21  to be transferred is mounted on the wafer chuck  22  by a wafer feed system (not shown). The wafer chuck  22  holds the wafer  21  through the vacuum attraction means. The alignment scope  27  sequentially measures alignment marks on the wafer surface supported by the wafer stage, measuring the position of the wafer  21  with high precision. Each transfer coordinate is computed based on the measured results. Based on the results, a transfer is sequentially provided in a step-and-repeat manner. After all the transfers are completed, the wafer  21  is fed out and the next wafer  21  is fed in. 
         [0034]    In transfer, before the wafer is moved to the transfer position, the nozzle  32  drops an adequate amount of resist to the transfer position. The wafer stage  23  then moves and positions the wafer  21  to the transfer position. Upon completion of the positioning, the imprint mechanism  13  descends the mold  11 , and presses it against the wafer  21 . A load sensor in the imprint mechanism  13  determines a completion of the pressing. After the mold is pressed, the illumination light is irradiated and cures the resist  42 . After the resist is cured, the mold  11  is pulled up and moved to the next transfer position (or shot). 
         [0035]    A detailed description will now be given of a transfer to a peripheral shot.  FIG. 3A  shows a shot layout of the wafer  21 .  51  denotes areas patterned by the mold  11 , i.e., an area (shot) that is formed by a one mold pressing and exposure light irradiation. Each shot has four similar patterns  52 , and each pattern  52  corresponds to one semiconductor chip. For convenience of explanation,  52  is referred to as a chip. In other words, a four device patterns (chips  52 ) are transferred per shot. The layout in  FIG. 3A  is an example of 21 shots. The shot layout of  FIG. 3A  includes peripheral shots at the wafer&#39;s periphery to which a complete pattern cannot be transferred. However, it is understood that two chips out of four in the peripheral shot are not defective and thus can be effectively used. 
         [0036]    Referring now to  FIG. 2 , a further detailed description will be given of the peripheral shot. Here,  FIG. 2  is a sectional view of the wafer chuck  22 . The mold  11  is ready to be pressed after aligned. The surface of the wafer chuck  22  is provided with openings that attract the wafer  21 , and are connected to a vacuum pumping system (not shown) through a vacuum attracting pipe  29  in the wafer chuck  22 . A valve (not shown) in the pipe opens and closes so as to fix and release the wafer. 
         [0037]    The recovery port  33  as a groove in the surface of the wafer chuck  22  extends along the wafer&#39;s circumference, and is connected to a recovery pipe  35 . The recovery unit  34  attracts the applied resist  41  that is spilt from the wafer  21  through the recovery port  33  and the recovery pipe  35  for recovery. As a result, the recovery port  33  recovers the resist  41  that flows out of the wafer  21  in transferring to a peripheral shot, and protects the inside of the apparatus from contaminations by the resist  41 . This configuration achieves a transfer of a pattern to a peripheral shot, maximizing the wafer, and provides more valid semiconductor chips by 16 per wafer than the layout shown in  FIG. 3  in which no peripheral shots are transferred so as to prevent the resist from flowing out of the wafer. Here, the layout of  FIG. 3B  is a conventional example of 13 shots, which has no peripheral shots. 
         [0038]      FIG. 4  shows a sectional view of a resist recovery means (a wafer chuck  22 A) according to a second embodiment applicable to the nanoimprint apparatus similar to the first embodiment, and illustrates only the wafer chuck  22 A&#39;s structure. Components in  FIG. 4  other than the recovery port  33 A are similar to those in the first embodiment in  FIG. 2 , and thus a duplicate description thereof will be omitted. The recovery port  33 A is formed on the wafer chuck  22 A. An annular groove as the recovery port  33 A extends along the wafer  21 &#39;s outer circumference on its attracting surface. The groove&#39;s outer circumference is larger than the wafer&#39;s, and the groove&#39;s inner circumference is smaller than the wafer  21 &#39;s contour. As shown in  FIG. 4 , when the wafer chuck  22 A holds the wafer  22 , the recovery port  33 A abuts the back surface of the wafer  21 &#39;s outer circumference (wafer attracted surface). The recovery port  33 A enables the recovery port  33 A to directly and securely recover the resist  41  that flows down when the peripheral shot is transferred. The wafer chuck  22 A has a reduced supporting area for the wafer&#39;s backside, but can securely recover the resist  41 . 
         [0039]      FIG. 5  shows a sectional view of a resist recovery means (wafer chuck  22 B) according to a third embodiment. Similar to the first and second embodiments, it is applied to the nanoimprint apparatus, and  FIG. 5  shows only the structure of the wafer chuck  22 B. Elements in  FIG. 5  other than the recovery port  33 B are similar to those in the first embodiment in  FIG. 2 , and thus a duplicate description thereof will be omitted. 
         [0040]    The wafer chuck  22 B has a concave shape with a center dent, and the dent is the surface of the wafer chuck. The size of difference in level is so set that when the wafer  21  is held, the surface of the wafer and the height of the wafer chuck&#39;s periphery are about the same level of surface. This configuration equally presses the entire pattern surface of the mold that transfers the pattern to the peripheral shot and realizes a highly accurate transfer. As shown in  FIG. 5 , the recovery port  33 B surrounds the circumference of the wafer  21  and extends to the rise higher than the wafer  21 . When viewed from the top, the surface of the wafer chuck  22 B forms double rings. The inner recovery port recovers the resist that flows outside the wafer, and the outer recovery port recovers the resist that the inner recovery port could not recover. This configuration also recovers resist  41  that drops outside the wafer. The double recovery ports on and outside the wafer can securely recover the splitting resist. 
         [0041]      FIG. 6  shows a schematic sectional view of a photo-curing nanoimprint apparatus  10 C as an example of processing apparatus of a fourth embodiment, and  FIG. 7  is an enlarged sectional view near the mold  11 C. The apparatus  10 C mainly includes elements supported by a mainframe  51 C and a stage support frame  52 C. While the above embodiments locates the wafer stage  23  movable on an XY plane below the mold  11  and presses the mold  11  against the wafer while facing its pattern surface down during the transfer, the apparatus  10 C locates the wafer stage  23 C above the mold  11 C and holds the mold  11 C with its pattern surface facing up. In transfer, the mold  11 C is elevated from the bottom to the wafer  21 C that faces down, and pressed against the wafer  21 C. 
         [0042]    A light source  15 C, an illumination optical system  14 C, an imprint mechanism  13 , and a mold chuck  12 C are held in the mainframe  51 C. The stage support frame  52 C is connected to the mainframe  51 C. The stage support frame  52 C supports and hangs the wafer stage  23 C. Except for the reverse positional relationship between the mold  11 C and the wafer  21 C, the fundamental roles of each element are the same as those in the foregoing embodiments. The apparatus  10 C is different from the apparatus  10  and others in that the apparatus  10 C includes a nozzle driver  36 C. While the above embodiments moves the wafer stage  23  moves to the fixed nozzle position and drops the resist on a predetermined shot position, this embodiment always drops the resist  42  on the mold  11 C. 
         [0043]    A pattern transfer to the wafer  21 C utilizes the step-and-repeat manner as in the foregoing embodiment. A description will now be given of an operation to each shot. Since the resist  42  is dropped on the mold  11 C rather than the wafer  21 C, some operations are different from those in the prior art. In dropping the resist, the nozzle  32 C is moved above the mold. After a transfer to the previous shot is finished and the mold  11 C moves down, the nozzle driver  36 C moves the nozzle  32 C above the mold. Then, the nozzle  32 C drops the resist  42 . The nozzle may move and drop the resist for uniform dropping of the resist on the pattern surface of the mold  11 C. Upon completion of dropping the resist  42 , the nozzle driver  36 C retreats the nozzle  32 C and prevents the interference between the nozzle  32 C and the mold  11 C when the mold  11 C is being elevated and pressed against the wafer  21 C. The imprint mechanism  13 C has a z stroke enough to introduce the nozzle  32 C between the wafer  21 C and the mold  11 C. 
         [0044]    In operation, after the mold  11 C moves down, the nozzle  32 C moves above the mold  11 C, and drops an adequate amount of resist  42 . The nozzle  32 C retreats after dropping the resist. The mold  11 C is moved up and pressed against the wafer  21 C. During pressing, the illumination light is irradiated via the light source  15 C and the illumination optical system  14 C, and cures the resist  42 . Then, the mold  11 C moves down. The resist  42  that forms a pattern remains on the wafer surface. The wafer stage  23 C is moved to the next shot position. 
         [0045]    With reference to  FIG. 7 , the nozzle  32 C moves above the mold  11 C and drops the resist  42 . The mold chuck  12 C holds the mold  11 C through vacuum attractions. A vacuum attraction pipe  29  is installed in the mold  11 C, and connected to a vacuum pumping system (not shown). A recovery port  33 C having the same size and shape as those of the mold is provided around the circumference of the mold  11 C. The groove is cut along the circumference of the mold  11 C, and connected to the recovery unit  34 , which can recover the resist that flows out of the mold  11 C and into the recovery port  33 C. The central part of the mold chuck  12 C has an opening for the illumination light for curing the resist to pass through. The resist  41  from the nozzle  32 C when spilling from the mold  11 C is a contamination source in the apparatus  10 C, and thus recovered from the recovery port  33 C. The recovery port extends along the circumference of the mold  11 C, and recovers the resist  41  without fail. 
         [0046]    Thus, a pattern transfer with the mold pattern surface facing upward and a recovery of the resist through the mold chuck protect the wafer  21  from contaminations by the resist. While this embodiment provides the mold chuck  12 C with the opening, the present invention is not limited to this embodiment and may use a different recovery means such as a pail structure around the circumference of the mold chuck  12 C. 
         [0047]    Referring now to  FIGS. 8 and 9 , a description will be given of an embodiment of a device manufacturing method using the above nanoimprint apparatus  10 .  FIG. 8  is a flowchart for explaining how to fabricate devices (i.e., semiconductor chips such as IC and LSI, LCDs, CCDs, etc.). Here, a description will be given of the fabrication of a semiconductor chip as an example. Step  1  (circuit design) designs a semiconductor device circuit. Step  2  (mold fabrication) forms a mold that forms a pattern corresponding to a designed circuit pattern. Step  3  (wafer preparation) manufactures a wafer using materials such as silicon. Step  4  (wafer process), which is also referred to as a pretreatment, forms actual circuitry on the wafer through the nanoimprint technique using the mold and wafer. Step  5  (assembly), which is also referred to as a post-treatment, forms into a semiconductor chip the wafer formed in Step  4  and includes an assembly step (dicing and bonding), a packaging step (chip sealing), and the like. Step  6  (inspection) performs various tests for the semiconductor device made in Step  5 , such as a validity test and a durability test. Through these steps, a semiconductor device is finished and shipped (Step  7 ). 
         [0048]      FIG. 9  is a detailed flowchart of the wafer process in Step  4 . Step  11  (oxidation) oxidizes the wafer&#39;s surface. Step  12  (CVD) forms an insulating film on the wafer&#39;s surface. Step  13  (electrode formation) forms electrodes on the wafer by vapor disposition and the like. Step  14  (ion implantation) implants ions into the wafer. Step  15  (transfer) presses the mold against the wafer while applying a photosensitive material to the wafer, and irradiates the UV light to transfer the circuit pattern onto the wafer. Step  16  (etching) uses reactive ion etching (RIE) to complete the patterning operation. Step  17  (resist stripping) removes disused resist after etching. Thus, devices (i.e., semiconductor chips, LCD devices, photographing devices (such as CCDs, etc.), thin-film magnetic heads, and the like) are fabricated. These steps are repeated, and multi-layer circuit patterns are formed on the wafer. The device manufacturing method of this embodiment uses the photo-curing method and maintains the high overlay accuracy. In addition, the use of the low-viscosity resist easily covers a fine mold pattern realizing the fine processing, and a transfer of the mold pattern to the peripheral shot improves the economical efficiency. Moreover, a recovery of the resist can prevent the contamination of the apparatus and wafer, providing high-quality devices. Thus, the device manufacturing method using the nanoimprint technology of this embodiment, and devices as a resultant product constitute one aspect of this invention. The present invention intends to cover devices as intermediate and final products of this device manufacturing method. Such devices include semiconductor chips such as LSI, VLSI and the like, CCDs, LCDs, magnetic sensors, thin film magnetic heads, and the like. 
         [0049]    Thus, these embodiments can provide a processing apparatus that has good overlay accuracy, fine processing and economical efficiency, and can prevent resist&#39;s contaminations. 
         [0050]    Further, the present invention is not limited to these preferred embodiments, and various variations and modifications may be made without departing from the scope of the present invention.