JP2012142327A - Imprint apparatus, method, and template for imprint - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an imprint apparatus, a method, and a template for imprint, capable of solving a problem in which conventional alignment systems are not capable of performing a good alignment, because a resin for imprinting flows into recesses and projections of an alignment mark on a template side, preventing a signal of the mark from being detected.SOLUTION: At a position apart from a mesa part where an imprinting pattern is formed, a minute mesa, having the same height as an imprinting pattern part, is provided for forming an alignment mark on a template side. With the alignment mark, an alignment is performed by observing an alignment mark on the wafer side of a shot different from an imprinting shot.

Description

  The present invention relates to an imprint apparatus and method, and an imprint template.

  Imprint technology, particularly nanoimprint technology, is a technology that enables transfer of nanoscale fine patterns, and is being put into practical use as one of nanolithography technologies for mass production of magnetic storage media and semiconductor devices. In nanoimprinting, an apparatus such as an electron beam drawing apparatus is used to form a pattern of a shot to be transferred on a mesa of a template. A fine pattern is formed by imprinting and transferring a pattern on a substrate such as a silicon wafer or a glass plate to which the pattern is transferred, using a mold on which a fine pattern is formed using an apparatus such as an electron beam drawing apparatus as an original plate. This fine pattern is formed by applying a resin for nanoimprinting on a substrate and curing the resin in a state where a mold pattern is pressed against the substrate through the resin.

  The main nanoimprint technologies that are currently in practical use include the thermal cycling method and the photocuring method. In the thermal cycle method, a thermoplastic nanoimprint resin is heated to a temperature equal to or higher than the glass transition temperature, and the mold is pressed against the substrate through the resin in a state where the fluidity of the resin is enhanced. And after cooling, a pattern is formed by pulling the mold away from the resin. On the other hand, in the photocuring method, an ultraviolet curable nanoimprint resin is used. The resin is applied on the substrate, and a pattern made by separating the mold from the cured resin after the resin is cured by irradiating with UV light while pressing a mold made of a light-transmitting material such as quartz. Is done. The thermal cycle method is accompanied by an increase in transfer time due to temperature control and a decrease in dimensional accuracy or position accuracy due to temperature change. However, since the photocuring method does not have such a problem, the photocuring method is nanoscale. This is advantageous in mass production of semiconductor devices.

  Various nanoimprint apparatuses have been realized so far depending on the curing method and application of the resin. When an apparatus for mass production such as a semiconductor device is assumed, an apparatus to which jet and flash imprint lithography (hereinafter referred to as JFIL) is applied is effective. A nanoimprint apparatus suitable for JFIL is disclosed in Patent Document 1. Such a nanoimprint apparatus has a substrate stage, a nanoimprint resin application mechanism, an imprint head, a light irradiation system, and an alignment mark detection mechanism for positioning. The imprint operation is performed in a step-and-repeat manner like an optical exposure apparatus because the area of a shot to be stamped once is limited.

  First, nanoimprint semiconductor applications are considered to be applied to memory devices. For memory devices, cost reduction by mass production was the primary challenge, and the most effective cost reduction was miniaturization. As is well known, nanoimprint technology is excellent in microfabrication capability, and is most suitable for the requirements of memory devices.

  An alignment operation in a conventional nanoimprint (hereinafter simply referred to as imprint) apparatus is performed as follows. An alignment mark is previously formed on a template that is a wafer and a mold (hereinafter referred to as a template in the present invention) so as to be overlapped at the time of stamping. The alignment measurement in each shot of the wafer is performed in a state where the wafer alignment mark of the shot and the alignment mark on the template are overlapped. That is, a method of optically observing the alignment state, correcting and driving the shift amount, and then irradiating exposure light to cure the resin.

  The alignment marks formed in advance on the template and a predetermined portion of the wafer are required to be as small as possible in order to reduce the cost of manufacturing the semiconductor element chip. In conventional optical exposure machines, the scribe between the chip and the chip is required. It is stored in the line. In a semiconductor imprint apparatus, a method has been proposed in which a large alignment mark dedicated area called mote is prepared for each shot adjacent to a scribe. The reason is to avoid an index matching effect described later. If the imprint technology is still at the experimental level, it could be mote. However, if the imprint technique is to be used for actual mass production, providing a large dedicated area such as a mote for each shot has a problem of reducing the effective area on the wafer. Further, since the imprinting resin is not applied to the moat portion, there is a problem in the consistency with the etching process after imprinting.

  For the above reasons, it has become necessary to make the alignment mark as large as other TEG marks used in semiconductor manufacturing and store it in a scribe line.

Japanese Patent No. 4185941

  However, the following problems occur when an alignment mark is placed in the scribe line. The first problem is that it is difficult to detect a template signal due to index matching. Since the alignment mark on the template side is made by etching a template made of quartz or the like, it has a structure in which simple irregularities are formed on glass.

  When imprinting resin enters the alignment mark part of the concavo-convex structure at the time of stamping, the refractive index of both (quartz or the like and imprinting resin) is almost the same, so the alignment mark of the template becomes invisible. A phenomenon occurs. This is a phenomenon called index matching. For this reason, means has been proposed for attaching a thin film to the alignment mark on the template side so that the mark can be seen optically. For example, a metal thin film is selectively attached to one of the uneven portions of the alignment mark.

  However, in the case of imprinting, the template is soiled if the stamp is repeated many times, so that periodic cleaning is required. In general, a metal thin film has no durability in cleaning, and will be lost after cleaning several times, thus limiting the life of the template. Although index matching measures are indispensable, the first problem is that the template life is limited when the metal mark is attached to the alignment mark.

  The second problem is that each time the alignment mark is stamped, it is crushed, and a large number of marks are required. Since the conventional optical stepper has adopted the global alignment method, if the reticle portion corresponding to the alignment mark position on the wafer is made a light shielding portion, in the case of a positive resist, the resist remains on the mark, and the subsequent steps The mark could be protected in the process. In the case of a negative resist, the same effect can be obtained if the opening is reversed.

  However, in the conventional imprint, the mark on the template is overlaid on the wafer mark, and the amount of mutual displacement is checked, and then exposure is performed. This is because both the template and the wafer accompanying the stamping may physically move together, so the alignment state is directly checked before exposure. For this reason, the alignment mark of the template is imprinted on the alignment mark of the wafer during exposure.

  The alignment mark is disposable in each process, and the alignment mark used in the previous process cannot be used in the next process. That is, as many alignment marks as the number of steps to be used are required. As the number of imprint processes increases, the area occupied by the alignment mark increases, which is a great restriction on the design of the semiconductor element.

  The third problem is cost. In order to avoid index matching, applying a thin film such as a metal to the alignment mark on the template requires an extra step in the template creation process. In the case of imprinting, since the template has a life due to contact, the template price has a great influence on the running cost. That is, the application of the thin film is inconsistent with the requirement for cost reduction of the template particularly required for imprinting.

  Therefore, an object of the present invention is to provide an alignment method that can obtain an alignment mark signal on a template without requiring a thin film while maintaining high alignment accuracy, and can protect a mark on a wafer. To do.

  In order to achieve this object, the present invention is characterized in that an alignment mark for a template is arranged in a region outside a shot to be originally imprinted, and alignment is performed by observing the alignment mark and the alignment mark of a wafer. To do. In this specification, the entire region where the pattern is actually imprinted and transferred is referred to as a shot. A shot may contain a plurality of chips, and if it is large, it may contain only one chip. The IC is the IC itself that is finally separated.

  Because the alignment mark for the template is physically separated from the shot part that is actually imprinted, there is an unexposed fluid imprint resin between the template and the wafer alignment mark during alignment. do not do. Accordingly, the resin does not fill the unevenness of the alignment mark on the template side as in the prior art, and index matching problems do not occur, and high-precision alignment can be performed.

  The present invention is characterized by using a template that is selectively formed by separating an alignment mark for a template from a mesa portion on the same surface (the same height) as a portion called a mesa that is actually stamped to form a pattern. To do. By making the height of the mesa portion and the alignment mark for the template the same, simultaneous drawing can be performed when a pattern is formed by EB on the template, and high-precision alignment accuracy can be achieved.

  Although several embodiments of the present invention are conceivable, in one of the preferred embodiments, when the template is in a stamped state, the position of the alignment mark provided on the template is changed to a stamp formed in advance on the wafer. Correspond to the position of the alignment mark in the scribe line other than the shot. The scribe line may be a scribe line that exists on the outermost side of the shot, or may be a scribe line that separates chips when the shot to be exposed is composed of a plurality of chips.

  In this case, the alignment mark on the template and the alignment mark on the wafer can be observed simultaneously during the stamping operation. Since observation is possible even during the stamping operation, the alignment accuracy can be improved. Furthermore, it is possible to further increase the alignment accuracy by monitoring the alignment state at a plurality of positions sandwiching the stamp target shot and performing processing such as averaging.

  Another embodiment of the present invention is characterized in that a stamping operation is started after a predetermined amount of step is performed after the alignment mark on the template side and the alignment mark on the wafer side are measured in advance. In this case, the position of the alignment mark on the template does not necessarily coincide with the position of the scribe line of the wafer, and is preferably determined according to the feature of the element. Particularly in the case of the present invention, the alignment mark on the template side may come into contact with the wafer at the time of stamping. If the position of the alignment mark on the template side is selected in advance at a location where damage to the element is unlikely to occur even if contact is made, the risk of occurrence of damage due to contact can be minimized.

  In the present invention, the time when the alignment mark on the wafer is actually detected is different from the time when the alignment mark is stamped. Therefore, the present invention is characterized in that, at the time of stamping, the mark is not engraved on the template side portion corresponding to the wafer alignment mark. As a result, even after the stamping, only the resin having a flat surface is placed on the wafer alignment mark, so that the mark can be protected.

  In the present invention, when performing alignment measurement, an unexposed resin is not inserted between the alignment mark on the template and the alignment mark on the wafer side, but only an unexposed resin is inserted only in a so-called mesa portion to be stamped to form a pattern. It is out. For this reason, in the present invention, in the application of the resin, an unexposed resin is not applied to a portion corresponding to the alignment mark on the template side at the same height as the mesa portion, thereby avoiding the index matching problem.

  In the present invention, alignment that can protect the alignment mark can be performed by forming the mesa portion for alignment in a place away from the stamped mesa.

It is the figure which showed the individuality of the nanoimprint method of 1st Embodiment of this invention. FIG. 3 is a layout diagram of observation optical systems according to a first embodiment of the present invention and a conventional example. It is the figure which showed the nanoimprint method of another embodiment of 1st Embodiment of this invention. It is another arrangement drawing of the observation optical system of 1st Embodiment of this invention. It is the figure which showed the structure of the nanoimprint method of 2nd Embodiment of this invention. It is the figure which showed the procedure of the nanoimprint method of 1st Embodiment of this invention.

<< First Embodiment >>
Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. First, the imprint apparatus is a device for transferring a concavo-convex pattern formed on a template to an imprint resin disposed (applied) on a substrate such as a wafer or glass. More specifically, the imprint resin having a photo-curing function and the concavo-convex pattern is brought into contact, and the imprint resin is irradiated between the concavo-convex patterns by irradiating ultraviolet light. Harden. The transfer is completed by peeling off the template on which the concavo-convex pattern is formed from the resin for imprinting after curing.

  FIG. 1A is a diagram showing the positions of an imprint shot 1 and adjacent shots 1R, 1U, 1L, 1D and alignment marks when the present invention is applied. As described above, a shot is an area where a pattern is formed by imprinting at once. Further, it is defined as an area that is finally separated from the chip and becomes an IC. In general, an integer number of chips are arranged in a shot. In the case of FIG. 1A, one shot is composed of 6 chips of 2 × 3.

  A scribe line as a margin for finally separating the chips is formed between the chips in the shot. Further, the peripheral portion of the shot is adjacent to the chip in the shot imprinted next. Therefore, a scribe line is also formed in the shot periphery. In a memory device to which imprint is most easily applied, there are many cases where a plurality of chips exist in a shot. However, in logic, since the size of the device is large, only one chip may be inserted.

  In FIG. 1A, the shot shot is 1 and the right side of the shot adjacent to 1 is named 1R, the upper side is 1U, the left side is 1L, and the lower side is named 1D. The naming method is the same in the following drawings. Since the imprint apparatus performs pattern formation by step-and-repeat, the pattern formed in each shot is basically the same. In the case of this figure, a pattern is formed in advance on the wafer to be stamped in the previous step.

  As an exposure apparatus for forming a pattern in the previous process, an immersion scanner is assumed. In the case of this embodiment, the size of one shot is set to be the same as the area that the immersion scanner can expose in one shot, but the concept of the present invention can be applied to different sizes. is there.

  Since recent immersion scanners are considered to be applied to double patterning, the accuracy between shots has been formed with a value on the order of 1 nm to sub-nm. The present invention is characterized in that, when a certain shot is imprinted, the wafer alignment mark of the adjacent shot is used instead of the wafer alignment mark of the shot to be imprinted. Since the shots are different when the alignment marks of the adjacent shots are used, it seems that the alignment accuracy deteriorates due to the stage error on the patterning error of the template in the same shot.

  However, according to the analysis by the inventors, with the recent improvement of the stage accuracy of the immersion scanner, the deterioration of the alignment accuracy due to the stage can be ignored. In imprinting, since the pattern on the template to be imprinted is the same size, it is not possible to receive the benefit of reducing the drawing accuracy due to the magnification as in the case of the 4 × reticle in the scanner. Rather, the position error due to drawing between patterns inside the same-size pattern is larger than the stage error between shots.

  Therefore, according to the inventor's analysis, the total alignment accuracy has hardly changed even if the wafer alignment mark in the shot to be stamped is used or the wafer alignment mark in the adjacent shot is used. The present invention becomes possible only when such changes in the situation are taken into account.

  In FIG. 1, there are three marks that can measure XY at three locations in the scribe line of each shot. These three are made in the same way for adjacent shots. The present embodiment is characterized in that the wafer alignment marks of adjacent shots are in a positional relationship in which they can be observed in an overlapping manner with the alignment marks of the template in a state where the shots to be imprinted are imprinted.

  That is, observation is performed with the alignment marks on both the template and the substrate being overlapped at a position separated from the pattern on the template mesa. In alignment observation, two parameters are given to each alignment mark on the template side.

  Specifically, the mark 1Rxy is used for the right adjacent shot 1R, 1Uxy is used for the upper adjacent shot 1U, 1Lxy is used for the left adjacent shot 1L, and 1Dxy is used for the lower adjacent shot 1D. Here, the subscript xy means that measurement in both X and Y directions is possible with one mark.

  In the present invention, when the target shot 1 is in the stamp position, alignment marks on the template side are provided at positions corresponding to the above-described marks 1Rxy to 1Dxy in order to perform alignment measurement on adjacent shots. The alignment marks on the template side are provided at positions indicated by 1Rxyt, 1Uxyt, 1Lxyt, and 1Dxyt corresponding to 1Rxy to 1Dxy. The subscript t indicates a mark on the template side.

Therefore, when the template is viewed from the wafer side to be imprinted, FIG. 1B shows the portions 1 and 1Rxyt, 1Uxyt, 1Lxyt, and 1Dxyt surrounded by the squares protruding as mesas. It should be noted that since FIGS. 1A and 1B are different in the observation direction, the relationship is reversed like a mirror image due to the relationship of agitation.
It is a requirement at the time of mass production to put the wafer alignment mark in the scribe line.

  Therefore, the alignment mark on the template side in this embodiment is characterized by being arranged at a position on the scribe line in the adjacent shot. Being on the scribe line means that at least one coordinate of the alignment mark observation position on the template side is at a position separated from the shot peripheral portion by an integral multiple of the chip. The coordinates referred to here mean XY coordinates that can be set along the periphery of the mesa portion 1t. Needless to say, a pattern of the device to be transferred (uneven pattern) is formed on the mesa portion 1t of the template 25.

  As shown in FIG. 2A, the apparatus side is also characterized in that an observation system is arranged at a position for observing a mark at a position distant from the stamp shot portion, and alignment is performed based on the observation result. For this reason, at least one of the observation position coordinates of the observation system is characterized in that it is in a state of observing a coordinate position that is an integer multiple of the chip away from the shot periphery. The arrangement of the observation system is provided so as to sandwich the mesa portion 1t of the stamp shot. By sandwiching, it is possible to expect an improvement in alignment accuracy by averaging the stage accuracy building.

  In the figure, 20 is a template and 21 is a wafer. Since the positions of 1Rxyt and 1Lxyt on which the template-side alignment marks are written are separated from the mesa portion 1t on which the IC pattern is written, the exposure light beam 22 and the observation optical systems 23 and 24 can be easily separated. This is obvious when compared with the configuration of the conventional example of FIG. In FIG. 2B, since the observation position is set at the end of the mesa 1t of the template 25, the separation of the observation optical systems 26 and 27 and the exposure light beam 22 is very limited, and design restrictions on the observation optical system become severe.

  FIG. 1C shows a template structure in the A-A ′ cross section of FIG. As described above, the template has a mesa structure 1t in which the shot portion 1 to be imprinted is raised in a plateau shape. The lift amount is generally in the range of 10 to several tens of um. On the other hand, the alignment mark portions 1Rxyt, 1Uxyt, 1Lxyt, and 1Dxyt on the template side are also characterized by a mesa structure having the same height as the mesa portion 1t.

  Since FIG. 1C is an A-A ′ cross section, 1Rxyt and 1Lxyt have the same height as the mesa portion 1t. As a result of the same height, when creating a template, the mesa part 1t and the alignment mark parts 1Rxyt, 1Uxyt, 1Lxyt, 1Dxyt can be exposed with a single electron beam (EB) drawing, enabling high-precision pattern drawing. It became. If the height is not the same as the mesa portion, EB drawing is repeated a plurality of times, and it is difficult to obtain alignment accuracy between 1t on which the actual element of the template is drawn and the pattern in the alignment mark portion.

  There are two stages in template production. One is a process of creating a mother template as an original plate by EB drawing, and the other is a process of creating many child templates by a replica method imprinted on the mother template. The mother template may be used for actual wafer stamping, but since the EB drawing takes time and is expensive, a child template is usually used for wafer stamping. Also in the creation of the child template, it is desirable that the mesa portions 1t on which the IC pattern is formed and the mesa portions of the alignment mark portions 1Rxyt, 1Uxyt, 1Lxyt, and 1Dxyt are aligned as shown in FIG.

  The mesa portions 1Rxyt, 1Uxyt, 1Lxyt, and 1Dxyt separated for the template side alignment mark basically need only have an alignment mark portion. However, the size of the mesa area of the alignment mark portion may be larger than the area occupied by the alignment mark because of the child template formation process. For example, in order to carry out the etching in the depth direction of the alignment mark of the template formed on the mesa portions 1Rxyt, 1Uxyt, 1Lxyt, 1Dxyt in the same manner as the actual element portion, the resin on the actual element portion and the alignment mark portion is etched. The thickness must be the same.

  In order to make the thickness uniform, the mesa area of the alignment mark region on the template side is adjusted. In a coating method using droplets such as JFIL, the thickness of the resin is determined by the amount of droplets, the area of the mesa portion, and the ratio of the pattern, so the thickness is controlled by adjusting the mesa area of the alignment mark portion. There is a need.

  When increasing the area of the mesa portion of the alignment mark on the template side, it is preferable to increase the area along the scribe line. Increasing the size along the scribe line means that a geometrical relationship is established that the area occupied by the alignment mark portion on the template side fits in the scribe line on the wafer side. When the alignment mark on the template side is provided at a position that matches the wafer alignment mark of the adjacent shot, the alignment marks may come into contact with each other at the time of stamping. In order to avoid this, it is increased in the scribe line direction, but this case will be described later.

  On the other hand, the alignment mark on the wafer side is formed on the scribe line between the chips including the most peripheral portion of the shot, as has been described many times. In the case of the most extreme one-shot one-chip configuration, the alignment mark is arranged at the peripheral portion. In the example of FIG. 1, one shot has a 2 × 3 6-chip configuration, and the alignment marks for detecting the XY directions are both included in the width of the scribe line.

  If the alignment mark area is large and one direction cannot fit in the scribe line, as shown in FIG. 3, it is necessary to separately arrange the X direction detection mark and the Y direction detection mark. There is. FIG. 3 shows an example in which marks for X measurement are included in two places in the scribe line of each shot and marks for Y measurement are included in two places. A total of four alignment marks, two each, are formed in advance in the same manner on each shot on the wafer. The alignment of the stamp shot 3 is performed by observing the wafer alignment mark of the adjacent shot with the alignment mark of the template in the stamped state.

  More specifically, the right adjacent shot 3R uses 3Rx and 3Ry, the upper adjacent shot 3U uses 3Ux and 3Uy, the left adjacent shot 3L uses 3Lx and 3Ly, and the lower adjacent shot 3D uses 3Dx and 3Dy. Here, the subscripts x and y mean that the X and Y directions are used for measurement at the mark, respectively.

  In this embodiment, when the target shot 3 is at the stamp position, alignment measurement is performed on adjacent shots. Therefore, template-side alignment marks are provided at positions indicated by 3Rxt, 3Ryt, 3Uxt, 3Uyt, 3Lxt, 3Lyt, 3Dxt, and 3Dyt corresponding to the above-described marks 3Rx to 3Dy. The subscript t indicates a mark on the template side. Accordingly, FIG. 3B shows the template as viewed from the side of the wafer to be imprinted, and the real element portions 3t and 3Rxt to 3Dyt surrounded by the squares protrude as mesas.

  In FIGS. 3A and 3B, since the observation directions are different, the relationship is reversed like a mirror image due to the relationship of the solder. The wafer alignment mark is usually placed in a scribe line. Therefore, the alignment marks on the template side in this embodiment are arranged so as to fit in the scribe lines in the adjacent shots. Being on the scribe line means that at least one of the position coordinates of the alignment mark on the template side is at a position separated from the shot peripheral portion by an integral multiple of the chip.

  In the figure, Sx and Sy indicate the sizes of the chip in the X and Y directions, the mark for measuring the Y direction is an integral multiple of Sx, and the mark for measuring the X direction is the peripheral portion of the mesa 3t by an integral multiple of Sy. Away from. When the target shot is stamped, no imprinting resin droplet is applied on the adjacent shot. Therefore, since there is no unexposed resin between the wafer alignment mark of the adjacent shot and the alignment mark on the template, a stable alignment signal can be obtained.

  If there is an alignment mark on the template side in the shot 1t or 3t portion to be imprinted as in the prior art, the unexposed resin is sprayed in a droplet state between the mesa portion to be imprinted and the wafer and spread by the imprint. Resin in an unexposed state has fluidity, flows in by imprinting, enters the concavo-convex portion of the alignment mark on the template side, and fills the concavo-convex structure. Since quartz is usually used as the template material, the refractive index is about 1.5, while the refractive index of the resin is about 1.5.

When the unevenness of the alignment mark of the template is filled with unexposed resin, an optical index matching effect occurs. Since the unevenness on the template side has the same refractive index, it loses its refractive power and loses its original function as an alignment mark.
In the initial imprint apparatus, a special area called mote is created exclusively for alignment in the template and wafer alignment so that unexposed resin does not rotate around the mote portion.

  When observed at the moat portion, the unfilled resin does not enter the alignment mark portion of the template, so that the alignment signal can be detected. However, when manufacturing a product such as a memory device in which cost is important, an area not related to the element function such as mote becomes a dead space, and the effective area of the wafer is reduced. Therefore, as described in the embodiments so far, it has become necessary to store the alignment mark in the scribe line originally provided for separating the chip.

  Since the scribe line is adjacent to the actual element, unexposed resin flows in at the time of stamping and an index matching effect occurs. There has been a means of intentionally generating contrast by attaching an optical thin film to the alignment mark on the template side. However, such a thin film not only has a problem of cleaning durability, but also has an adverse effect of making an imprint template to be manufactured inexpensively because an extra process is required for manufacture.

  In the adjacent shot alignment according to the present embodiment, since there is no filling problem due to unexposed resin, the index matching phenomenon does not occur, and the unevenness of the alignment mark on the template side can play the original role. Therefore, an extra film forming process is unnecessary, and the cost increase of the template can be minimized.

  In the exposure apparatus of this embodiment, the wafer alignment mark in the stamp shot is not used for positioning when stamping the own shot, but is used for positioning when stamping the adjacent shot. Therefore, there are two states regarding the observation of the wafer alignment mark. One is a state observed in the state before the stamping, and the other is a state in which the resin after the exposure exists on the wafer alignment mark after the stamping. In the former case, there is no problem because the wafer alignment mark is observed as it is in the initial state, but in the latter case, there is a possibility of giving an erroneous signal if there is an extra pattern on the resin after exposure on the mark. .

  Therefore, the present invention is characterized in that, at the time of stamping, the pattern of the template portion at the position corresponding to the wafer alignment mark is a shape that does not give an extra signal, for example, a flat pattern. Since the resin itself is transparent to the observation light, if the surface shape is flat, the originally formed wafer alignment mark can be observed without distortion. However, from the viewpoint of optical signal detection, there is an output difference depending on the presence or absence of resin even if the wafer alignment mark is flat.

  Therefore, in the alignment observation, the apparatus side has two parameters for each alignment mark on the template side, and these two parameters correspond to the presence or absence of the imprinting resin on the alignment mark on the substrate side. And That is, on the apparatus side, it is necessary to enable separate offsets for the above two states or control of the state of the observation optical system, such as optimal wavelength selection.

  The fact that an extra signal component is not given to the wafer alignment mark at the time of stamping means that this mark can be used in subsequent processes. In the conventional method, after simultaneously observing the wafer alignment mark and the template alignment mark in the stamp shot, ultraviolet irradiation is performed with the marks aligned.

  Therefore, after the stamping, the concave / convex pattern of the template alignment mark is firmly imprinted on the resin on the wafer alignment mark and cannot be used in the subsequent process. This patent made it possible to protect wafer alignment marks and reduce the number of alignment marks.

  The alignment mark on the template side of the present invention is desirably arranged at a position symmetrical to the stamp shot. Although it is most preferable to arrange at a point-symmetrical position, line symmetry is also effective because there are restrictions on the arrangement of IC elements. By averaging the measurement results of the alignment detection positions that are symmetric with respect to the stamp shot, it is possible to average the step error when the wafer is created in the previous process described above, and to improve the alignment accuracy.

  Then, the asymmetry of the arrangement with respect to the mesa portion of the shot pattern to be transferred at a plurality of alignment mark observation positions is corrected and calculated, and the alignment operation is performed. That is, when it deviates from the symmetrical position, it is possible to deal with it by introducing an asymmetry process so that a weight is applied at the time of interpolation according to the geometric arrangement.

  The measurement by the symmetrical arrangement cannot be performed when the wafer comes to the edge portion of the wafer and only one of the wafer alignment marks exists. In that case, the deviation of the edge shot is inferred from the result of one shot. When analogizing the deviation of the edge shot from the adjacent shot, the following is preferable. That is, the first wafer of a lot starts with the imprinting of a shot with all adjacent shots, learns the correlation between the measured value of the alignment mark on each template side and the final correction value of each shot, and then takes the edge shot. It is preferable to go to the seal. If one or several such learnings are performed and the habit at the time of edge shot imprinting is stored as an offset value, the imprinting can be performed in the order of the earliest throughput thereafter.

  Another feature in the adjacent shot alignment is that the alignment can be speeded up. When using the alignment mark arranged in the conventional stamp shot, it was assumed that measurement was started after unexposed resin was filled between the wafer and the template. In the case of JFIL, resin droplets are placed on a wafer in advance and spread by a stamping operation to uniformly distribute the resin. In the process of extending, unexposed resin enters the structure of the wafer alignment mark and the template alignment mark. The process of the resin entering is the time when the wetted part gradually expands when the alignment mark part is observed, and the alignment signal is extremely unstable during that time.

  On the other hand, when the alignment signal is detected in the adjacent shot of the present embodiment, since a fluid unexposed resin does not exist between the wafer and the alignment mark on the template side, a stable signal can be acquired from the beginning. Therefore, in the present invention, the observation at a plurality of alignment positions is stepped to the next shot, and alignment is performed by taking an alignment signal from the point when the resin is still in the filling process at the stamping shot portion. Specifically, the observation at a plurality of alignment positions is performed from the time when the substrate moves stepwise relative to the mesa portion of the template until the stamping is completed. Filling can take several seconds.

  In addition, when there is an alignment mark in the conventional stamped portion, the mark is located at the outermost peripheral portion and filling is the last, so that there is a waiting time until filling is completed. In the present invention, since the alignment signal can be monitored from the filling period, the alignment time can be greatly shortened. Further, by continuing the measurement until the completion of the stamping, it is possible to cope with an unexpected situation that occurs at the time of contact between the template and the wafer at the time of stamping. For example, if the stamping operation is not successful with dust or the like sandwiched during stamping, an abnormal value is likely to appear in the alignment signal.

  When an abnormal value appears during alignment observation, a warning signal is output to the control unit of the apparatus main body, and a determination is made that the apparatus is stopped or the imprint operation is stopped depending on the state and the next shot is started. For detecting an abnormal value, a criterion such as detecting that a measured value of two alignment signals having a relationship between shots deviates from a value predicted to be obtained when stepping to the next shot is more than a certain threshold is applied. The

  In the present invention, as shown in FIG. 1C, the template side alignment mark and the mesa portion of the stamped portion are flush with each other, so that the wafer at the time of stamping and the template side alignment mark may come into contact with each other. Conventionally, there has been an idea that the height of the alignment mark on the adjacent shot side is slightly lower than the mesa pattern on the stamped portion in order to cope with the contact. However, as described above, since this method needs to perform EB drawing separately, it is impossible to maintain the positional relationship between the alignment mark part and the actual element mark part on the template side with high accuracy at the nm level.

  The present invention is characterized in that both are kept on the same surface and EB drawing is simultaneously performed to ensure positional accuracy and contact is allowed. If it is strong to destruction by contact, contact is considered acceptable. If they are in contact, it is desirable that the contact portion is not an actual element portion. This is the reason why the mesa portion area of the template side alignment mark described above is extended into the scribe line area. Since the imprint apparatus is also an exposure apparatus, it has a stage accuracy of at least about um.

  Therefore, the mesa side and wafer side patterns with which the mesa portions of the alignment marks on the template side come into contact can be designed in advance. Accordingly, it is possible to fit the alignment mark area on the template side into the corresponding scribe line of the wafer. In addition to this, the pressure applied upon contact can be calculated. If a pattern is designed in such a way that the template and the wafer come into contact with each other in the state of a line having a width of 1 μm or more when they come into contact with each other, as a result, the occurrence of failure during contact can be ignored. it can.

  Since the contact occurs due to the surface accuracy of the wafer or the template, it does not contact at a pinpoint but contacts as a region. Therefore, if the contact area of the pattern portion is large and the pattern is thick, the possibility of breakage is reduced. Further, since the template itself has an elastic force, the pressing force is not so strong.

  With the configuration of this embodiment, because of analogy from adjacent shots, it is impossible to correct non-linear distortion such as step direction between shots, chip rotation error, skew generated in the shot, and trapezoidal distortion. . However, these errors are errors in the exposure apparatus and process equipment up to the previous process for making a wafer. For example, the step direction and the chip rotation error are errors caused by the exposure apparatus before imprinting. These correction amounts can be corrected on the imprint apparatus side if they are previously input as global items offline.

  As described above, this embodiment can create new possibilities for adjacent shot alignment, which has been considered to be less accurate, by improving the overlay accuracy of recent optical exposure devices such as immersion. did it. In addition, by allowing the contact in adjacent shots and devising the mark so as not to hit the actual element, the occurrence of the problem pixel can be ignored.

  Further, since the alignment mark part is separated from the 1t or 3t mesa part, the degree of freedom is greatly increased so that the configuration of the observation optical system can be seen in the arrangement of 41 to 44 in FIG. It is possible to increase the NA of the observation optical system and to flexibly arrange the illumination system, which can contribute to higher alignment accuracy.

  In the present embodiment, an example of using shots in the upper, lower, left, and right directions as the positions of adjacent shots has been described, but it is also possible to use shots at diagonal positions as adjacent positions.

<< Second Embodiment >>
When one chip has one shot as in the case of logic, the position of the template side alignment mark is considerably far from the mesa of the stamped portion, although it is an adjacent chip. As an extreme example, when the entire shot size 26 × 33 mm ² of the scanner is set to one chip, one of the alignment marks on the template side is located 33 mm away. Of course, there are cases where this is acceptable depending on the accuracy, but the second embodiment is a method of monitoring alignment at a slightly closer position.

  FIG. 5A is a layout diagram of wafers. As shown in the figure, the arrangement is complete, and the 2 × 3 chip arrangement is one shot as in the previous examples. In this example, the alignment is performed using the alignment mark of the own shot, not the adjacent shot, and the alignment mark provided on the template. In this embodiment, the alignment mark on the template side can be set at an arbitrary position away from the stamp mesa 5t. Also in this embodiment, as shown in FIG. 1C of the first embodiment, the height of the mesa portion of the alignment mark is the same as the mesa 5t of the stamp portion.

  FIG. 5B is a layout in one shot on the wafer side, and FIG. 5C is a layout diagram on the template side. Here, alignment marks 5Rxy, 5Uxy, 5Lxy, and 5Dxy are formed on a scribe line around the wafer side. On the other hand, 5Rxyt, 5Uxyt, 5Lxyt, and 5Dxyt are formed on the template side together with the mesa portion 5t of the pattern.

  In the present embodiment, the positions of 5Rxyt, 5Uxyt, 5Lxyt, and 5Dxyt do not necessarily correspond to the scribe line shape. For this reason, the alignment sequence is shown in FIG. The order is arbitrary, but first, alignment measurement is performed by superimposing 5Rxy and 5Rxyt in FIG. Next, alignment measurement is performed in the order of 5Uxy, 5Uxyt, 5Lxy, 5Lxyt, 5Dxy, and 5Dxyt, and a sequence for determining 5t alignment using these measurement values.

  In this case, since the distance between 5t and each alignment mark on the template is known in advance as a design value, a measurement system such as an interferometer or an encoder is provided separately, while monitoring the value of the interferometer. Alignment measurement and alignment drive are performed. In this case, in order to monitor the displacement accompanying the contact between the template and the wafer, the measurement system is provided on both the wafer and the template.

  The present embodiment also has the same characteristics such as that the unfilled resin does not enter between the template and the wafer that the first embodiment has. However, since it cannot be monitored in real time at the time of stamping as in the first embodiment, the accuracy of the interferometer is trusted. In addition, since R → U → L → D must be measured four times, it takes time. Therefore, by accumulating learning, it is possible to speed up by omitting some measurements.

  This embodiment can also protect the alignment marks on the wafer. The pattern of the template corresponding to the wafer alignment mark at the time of stamping may be a shape that does not give an extra alignment signal after the stamping, for example, a flat pattern.

  Also in this embodiment, there is a possibility that the alignment mark on the template side contacts the wafer at the time of stamping. If the position of the alignment mark on the template side is selected in advance at a location where damage to the element is unlikely to occur even if contact is made, the risk of occurrence of damage due to contact can be minimized.

  In the embodiment described above, alignment that can protect the alignment mark with high accuracy can be performed by forming the mesa portion for alignment at the same height in a place away from the stamp mesa.

  Further, in the embodiment described above, it is possible to acquire a template-side alignment mark signal without attaching a special thin film to the template-side alignment mark. Since the wafer side alignment mark can be protected, the same alignment mark can be used a plurality of times, and the area occupied by the alignment mark can be reduced. Further, since a special thin film process is not required, it is possible to provide a low-cost template. In addition, since the alignment mark of the template and the pattern of the actual element portion to be actually imprinted can be drawn simultaneously with an electron beam, the relative position accuracy of the pattern in the template can be guaranteed.

  Therefore, the positional relationship between the patterns inside the template can be maintained with high accuracy, and high-precision alignment can be expected. If the positional relationship within the template cannot be maintained with high accuracy, offset processing may be performed. However, considering the problem of offset measurement accuracy and the need to frequently replace the template during imprinting, offset processing is possible. Is not practical.

  In one of the preferred embodiments, the stamping can be performed while monitoring the alignment state of the two at the time of stamping, leading to higher alignment accuracy. In the conventional JFIL system, unexposed resin is dispersed as droplets on the wafer and spread and connected at the time of stamping to apply the resin. For this reason, it is impossible to acquire an alignment signal until the resin applied as discrete droplets flows on the alignment marks on the wafer and covers the whole.

  In the present invention, since there is no unexposed and fluid resin between the template and the wafer alignment mark, measurement can be started without waiting for resin filling. For this reason, the throughput of the apparatus can be increased, and the effect of improving the processing capability is great.

1 ... Shot to be stamped, 1t ... Mesa on template corresponding to stamp shot, 1R, 1U, 1L, 1D ... Shot adjacent to stamp shot 1 1Rxy, 1Uxy, 1Lxy, 1Dxy ... Existing wafer alignment mark, 1Rxyt, 1Uxyt, 1Lxyt, 1Dxyt ... Template alignment mark on template, 3 .... Shot to be imprinted, 3t ... Mesa on template corresponding to imprint shot, 3R, 3U, 3L 3D ··· Shot adjacent to imprint shot 3 3Rx, 3Ry, 3Ux, 3Uy, 3Lx, 3Ly, 3Dx, 3Dy ··· Wafer alignment mark existing in shot adjacent to imprinted shot, 3Rxt, 3Ryt, 3Uxt, 3Uyt 3Lxt, 3Lyt, Dxt, 3Dyt, template alignment mark on template, 5. shot to be stamped, 5t, mesa on template corresponding to stamp shot, 5Rxy, 5Uxy, 5Lxy, 5Dxy, wafer alignment mark, 5Rxyt, 5Uxyt, 5Lxyt, 5Dxyt, template alignment mark on template, 20 ... template, 21 ... wafer, 22 ... exposure beam, 23, 24 ... alignment observation system, 25 ... template, 26, 27 ... .Alignment optical system, 41, 42, 43, 44..Alignment optical system

Claims (21)

  In an imprint apparatus for forming a pattern of a shot to be transferred on a template mesa and imprinting the pattern onto a substrate to be transferred, a plurality of positions separated from the pattern on the mesa of the template The imprint apparatus is characterized in that the alignment mark on both the template and the substrate is observed in an overlapping state, and the pattern on the mesa is imprinted on the substrate based on the observation result.   The coordinate of at least one of the plurality of alignment mark observation positions is set at a position that is an integer multiple of the size of the chip in the shot from the periphery of the mesa. Imprint device.   3. The imprint apparatus according to claim 2, wherein the observation at the plurality of alignment positions is performed from when the substrate is moved stepwise relative to the mesa of the template until the stamping is completed. .   The imprint apparatus according to claim 3, wherein a warning signal is output to a control unit of the apparatus main body when an abnormal value is obtained in the observation.   2. The imprint apparatus according to claim 1, wherein the observation has two parameters for each alignment mark on the template side.   6. The imprint apparatus according to claim 5, wherein the two parameters are parameters corresponding to the presence or absence of an imprinting resin on the alignment mark of the substrate.   The imprint apparatus according to claim 1, wherein the alignment operation is performed by correcting and calculating the asymmetry of the arrangement of the observation positions of the plurality of alignment marks with respect to the mesa portion of the shot pattern to be transferred.   In an imprint method in which a pattern of a shot to be transferred is formed on a mesa of a template and the pattern is imprinted on a substrate to be transferred, the imprint method is performed at a plurality of positions on the mesa separated from the pattern of the template An imprint method comprising: observing an alignment mark provided on the substrate through an alignment mark of the template provided, and imprinting a pattern on the mesa on the substrate based on an observation result.   9. The imprint method according to claim 8, wherein the alignment mark region of the template provided on the mesa is accommodated in a scribe line provided on the corresponding substrate.   The alignment mark provided on the substrate to be observed through the alignment marks of the template provided at the plurality of positions is an alignment mark of a shot different from the shot to be stamped. The imprint method according to 8 or 9.   The position of the alignment mark of the template provided in the plurality of positions matches the position of the alignment mark of a shot different from the stamp shot on the substrate in a stamped state. Imprint method.   The alignment operation is performed by setting at least one coordinate of the plurality of alignment mark observation positions to a position that is an integral multiple of the size of the chip in the shot from the periphery of the mesa. The imprint method according to 10.   13. The inspection according to claim 11 or 12, wherein the observation at the plurality of alignment positions is performed from the time when the substrate is moved stepwise relative to the mesa of the template until the stamp is completed. How to print.   9. The imprint method according to claim 8, wherein the alignment operation is performed by correcting and calculating the asymmetry of the arrangement of the plurality of alignment mark observation positions with respect to the mesa portion of the shot pattern to be transferred.   The first substrate of the lot is characterized by starting from the stamping of a shot of all adjacent shots and learning the correlation between the measured value of each alignment mark of the template and the final correction value of each stamped shot. The imprint method according to claim 8.   An imprint template, wherein a pattern of a shot to be transferred is formed on a mesa, and alignment marks are formed on the mesa at a plurality of positions separated from the pattern.   The imprint template according to claim 16, wherein the height of the mesa having the pattern of the shot to be transferred is equal to the height of the mesa of the alignment mark at the plurality of positions.   The coordinate of at least one of the alignment marks at the plurality of positions is set at a position that is an integer multiple of the size of the chip in the shot from the periphery of the mesa. Template for imprint.   19. The imprint template according to claim 18, wherein the mesa on which the alignment mark is formed is sized to fit in a scribe line of a corresponding substrate.   The mesa portion having a pattern of a shot to be transferred has a shape in which a pattern corresponding to a position to be an alignment mark on the substrate side at the time of imprinting has a shape that does not give an extra signal after imprinting. The imprint template according to 16. 21. The imprint template according to claim 20, wherein the shape that does not give the extra signal is a flat pattern.