JP2007178538A - Photomask, method for measuring shot overlay accuracy, and method for manufacturing semiconductor device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photomask and a method for measuring shot overlay accuracy by which the overlay accuracy among shots belonging in different mask layers can be rapidly measured and shot overlay with high accuracy can be achieved, and to provide a method for manufacturing a semiconductor device. <P>SOLUTION: Four corners of a rectangular shot 1 are provided with measurement mark regions 13, 14, 15, 16 each having a line pattern extending parallel to the directions of two adjacent sides constituting the shot. Another shot having measurement mark regions in the same positions as in the shot 1, each mark region having a line pattern extending parallel to the directions of two adjacent sides constituting the shot is transferred onto an upper layer on the undercoat layer where the shot 1 is transferred. The line pattern of each measurement mark region is disposed in such a manner that each line pattern does not overlap other patterns when the shots are transferred onto the substrate with each mark region completely overlaps others. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a photomask having a mark for measuring overlay accuracy, a method for measuring shot overlay accuracy, and a method for manufacturing a semiconductor device.

  In a lithography process of a semiconductor device manufacturing process, a step-and-repeat type exposure apparatus is used when a fine pattern is transferred onto a wafer. In this type of exposure apparatus, a photomask (hereinafter referred to as a reticle) having a pattern several times larger than the pattern formed on the wafer is used. The pattern on the reticle is reduced and projected onto the wafer via an optical lens, and transferred repeatedly while changing the position on the wafer for each shot. At this time, each shot (exposure unit) on the substrate is transferred so as to overlap a part of the immediately preceding shot.

  In recent lithography techniques, it is necessary to perform pattern transfer on a layer formed continuously on an underlayer on which a fine pattern is formed. For this reason, it is important that the pattern of the upper layer (exposure shot) and the pattern of the base layer are accurately superimposed at the time of exposure. In order to perform superposition with high accuracy, alignment measurement is performed to obtain positional information of the shot of the underlayer before exposure. After aligning the exposure shot based on the position information, the upper layer pattern is transferred.

  However, in the step-and-repeat reduction projection exposure, as is well known, it is well known that arrangement errors such as a projection magnification error and a rotation error occur during exposure. Here, the projection magnification error is a deviation between the projection magnification of the transfer pattern and the desired projection magnification. The rotation error is a deviation between the direction of the transfer pattern and a desired direction. Due to the arrangement error, even if the alignment is performed with high accuracy, an error occurs in the overlay between the pattern of the base layer and the upper layer pattern.

  In order to reduce such an arrangement error, a pattern for measuring overlay accuracy such as a box-in-box pattern is arranged on the reticle in a region where shots overlap on the substrate. The measurement pattern is configured such that a complete pattern is formed when the shots overlap. Therefore, the arrangement error can be calculated by measuring the shape of the measurement pattern after development. The calculated arrangement error is fed back to the exposure apparatus, and the optical system of the exposure apparatus is adjusted so as to eliminate the arrangement error. Then, by performing the exposure of the next wafer in the state where the adjustment is performed, the placement error is reduced.

  The measurement of the arrangement error is performed on several measurement patterns provided in one shot in order to calculate the projection magnification error and the rotation error. In this case, even when global alignment is performed to estimate the placement error of the entire wafer based on the measurement results for several shots on the wafer and adjust the optical system, several tens of wafers are required. It is necessary to measure the measurement pattern at the location. For this reason, a great deal of time is required for overlay accuracy measurement.

  For example, Patent Document 1 described later discloses a technique for performing overlay accuracy measurement in a short time. In this technique, a reticle includes a chip pattern region in which an integrated circuit pattern to be a product is formed, and a scribe pattern region formed so as to surround the chip pattern region. At the four corners of the scribe pattern area, an outer X portion, an outer Y portion, an inner X portion, and an inner Y portion constituting the box-in-box pattern are respectively arranged. The outer X portion is composed of two vertical sides of the outer box mark (square shape), and the outer Y portion is composed of two lateral sides of the outer box mark. The inner X portion consists of two sides in the vertical direction of the inner box mark, and the inner Y portion consists of two sides in the horizontal direction of the inner box mark.

Steps and repeats are performed in rows and columns using the reticle to transfer the shot onto the wafer, so that the patterns arranged at the four corners on the reticle are superimposed on the wafer. Thereby, a box-in-box pattern for overlay accuracy measurement is formed on the substrate. According to this configuration, the presence or absence of a projection magnification error and a rotation error is determined by measuring the relative positions of the outer X portion, the outer Y portion, the inner X portion, and the inner Y portion with respect to one box-in-box pattern. be able to.
JP 2002-62635 A

  Thus, with the technique disclosed in Patent Document 1, it is possible to measure the overlay accuracy of shots belonging to the same layer with a relatively small number of measurements. However, it is not possible to directly measure the overlay accuracy between shots belonging to different layers, such as upper layer shots and underlayer shots.

  For example, if the projection magnification error and rotation error of the underlayer shot are larger than those of the upper layer shot, or the sign of the projection magnification component or rotation component is inverted between the upper layer shot and the underlayer shot. If so, a large misalignment occurs between the two layers. In the conventional technique described above, in order to measure the overlay accuracy between the upper layer shot and the underlying layer shot, it is necessary to separately perform measurement by providing another overlay accuracy measurement pattern.

  On the other hand, by increasing the number of measurement points of the overlay accuracy measurement pattern, it is possible to perform overlay with higher accuracy, but the measurement time significantly increases as the number of measurement points increases. For this reason, there is a need for a technique capable of performing highly accurate overlay in a shorter time.

  The present invention has been made in view of the above-described conventional problems, and is capable of measuring the overlay accuracy between shots belonging to different mask layers at a high speed, and realizing a highly accurate shot overlay, It is an object of the present invention to provide an alignment accuracy measuring method and a semiconductor device manufacturing method.

  In order to solve the above problems, the present invention employs the following means. That is, the photomask according to the present invention includes at least one measurement mark area provided at each of the four corners of a rectangular shot. In each measurement mark region, a measurement pattern including a line pattern extending in the first direction and a line pattern extending in a second direction different from the first direction is formed. Each line pattern is arranged in a state where the line patterns belonging to each measurement mark region do not overlap each other when all the measurement mark regions located at different corners overlap each other.

  Here, the four corners refer to regions where four different shots adjacent to each other overlap when a rectangular shot is transferred onto the substrate by a step-and-repeat exposure apparatus.

  In addition, the present invention can provide a pair of photomasks including a lower-layer photomask and an upper-layer photomask made of the photomask having the above-described configuration. In this case, each line pattern of the present photomask is obtained when the measurement mark regions located at different corners on the lower layer photomask and the measurement mark regions located at different corners on the upper layer photomask overlap each other. The line patterns belonging to the measurement mark area are arranged so as not to overlap each other.

  On the other hand, in another aspect, the present invention can provide a shot overlay accuracy measuring method for measuring shot overlay accuracy of a lower layer pattern and an upper layer pattern transferred onto a substrate by a step-and-repeat type exposure apparatus. . That is, in the shot overlay accuracy measuring method according to the present invention, first, measurement is performed in which line patterns extending in the first direction and line patterns extending in the second direction different from the first direction are formed at the four corners of the rectangular shot. A lower layer pattern is formed in a state where the measurement mark regions at the four corners overlap using a lower layer photomask having a mark region. Next, an upper layer film is formed on the lower layer pattern.

  Subsequently, the measurement mark regions at the four corners and the above using the photomask for the upper layer provided with the measurement mark regions in which the line pattern extending in the first direction and the line pattern extending in the second direction are formed at the four corners of the shot. The upper layer pattern is transferred in a state where the lower layer measurement mark region overlapped with the lower layer overlaps.

  Then, the relative distance between the lower line pattern extending in the first direction and the upper line pattern extending in the first direction formed by the above steps, and the second direction formed by the above steps. The relative distance between the lower line pattern extending in the second direction and the upper line pattern extending in the second direction is measured.

  Here, the relative interval is preferably the relative interval between the line patterns belonging to the measurement mark region located at the same corner in the lower layer photomask and the upper layer photomask.

  In still another aspect, the present invention can provide a semiconductor device manufacturing method in which a lower layer pattern and an upper layer pattern are transferred onto a substrate by a step-and-repeat type exposure apparatus. That is, in the method for manufacturing a semiconductor device according to the present invention, the measurement mark regions in which the line pattern extending in the first direction and the line pattern extending in the second direction different from the first direction are formed at the four corners of the rectangular shot. A lower layer pattern is formed in a state where the measurement mark regions at the four corners overlap with each other using a lower layer photomask. Next, an upper layer film is formed on the lower layer pattern.

  Subsequently, the measurement mark regions at the four corners and the above using the photomask for the upper layer provided with the measurement mark regions in which the line pattern extending in the first direction and the line pattern extending in the second direction are formed at the four corners of the shot. The upper layer pattern is transferred in a state where the lower layer measurement mark region overlapped with the lower layer overlaps.

  The relative distance between the lower line pattern extending in the first direction and the upper line pattern extending in the first direction formed by the above steps, and the second direction formed by the above steps. The relative distance between the lower line pattern and the upper line pattern extending in the second direction is measured.

  Then, the subsequent upper layer pattern is transferred in a state where the difference between the measured relative interval and the design value of the relative interval is reduced.

  In addition, the present invention can provide a method for manufacturing another semiconductor device using the above-described photomask. That is, in the method for manufacturing a semiconductor device according to the present invention, the measurement mark regions in which the line pattern extending in the first direction and the line pattern extending in the second direction different from the first direction are formed at the four corners of the rectangular shot. A lower layer pattern is formed in a state where the measurement mark regions at the four corners overlap with each other using a lower layer photomask. Next, an upper layer film is formed on the lower layer pattern.

  Subsequently, in a state where the substrate is arranged at a position where the upper layer pattern is exposed, the position of each lower layer pattern is measured, and the position where each lower layer pattern should be formed in design in the arrangement state of the substrate; The difference from the measured position of each lower layer pattern is calculated. Then, the upper layer pattern is exposed while the difference is reduced.

  Note that the first direction and the second direction are, for example, directions parallel to the sides constituting the shot.

  According to the present invention, it is possible to measure the overlay accuracy of an exposure shot with respect to a lower layer shot only by measuring one shot overlay measurement pattern. The arrangement error calculated based on the measurement result is obtained directly from the error for the lower layer shot. Therefore, highly accurate shot superposition can be performed by feeding back the arrangement error to the exposure apparatus and adjusting the optical system of the exposure apparatus so that the arrangement error is reduced. Therefore, it is possible to realize shot overlay with higher accuracy than in the prior art without increasing the number of measurement points.

  In addition, since the overlay accuracy of the exposure shot with respect to the lower layer shot can be obtained by measuring one measurement pattern, an arrangement error for the lower layer shot can be obtained in a very short time.

  Hereinafter, an embodiment according to the present invention will be described in detail with reference to the drawings based on an example in which the present invention is applied to a photomask (reticle) used for reduced projection exposure.

  FIG. 1 is a plan view showing the reticle of this embodiment. The reticle of this embodiment can be configured by arranging a pattern formed of a light shielding material such as chrome on one surface of a transparent substrate such as quartz, as in the known reticle.

  As shown in FIG. 1, the reticle of this embodiment includes a rectangular shot 1 (exposure unit) composed of a circuit pattern region 11 and a light shielding region 12. The light shielding region 12 is configured by arranging a light shielding film in an L shape over a predetermined width from two adjacent sides (the left side and the lower side in FIG. 1) of the four sides constituting the shot 1. Further, an area other than the light shielding area 12 in the shot 1 is a circuit pattern area 11, and a circuit pattern or the like to be transferred is arranged.

  Now, at the four corners of the reticle 1 of this embodiment, there are provided measurement mark regions 13, 14, 15, 16 in which patterns for measuring shot overlay accuracy are arranged. In this embodiment, the area sizes of the measurement mark areas 13 to 16 are all the same, and different measurement patterns are formed in the measurement mark areas 13 to 16, respectively. In the following description, the measurement mark areas 13 to 16 are appropriately referred to as an upper right mark area 13, an upper left mark area 14, a lower left mark area 15, and a lower right mark area 16 according to the arrangement positions in FIG.

  Distance from upper end of shot 1 to upper end of upper right mark area 13, distance from upper end of shot 1 to upper end of upper left mark area 14, distance from lower end of circuit pattern area 11 to upper end of lower left mark area 15, and circuit pattern The distances from the lower end of the region 11 to the upper end of the lower right mark region 16 are all the same (distance dy). Further, the distance from the right end of shot 1 to the right end of upper right mark area 13, the distance from the right end of shot 1 to the right end of lower right mark area 16, the distance from the left end of circuit pattern area 11 to the right end of upper left mark area 14, The distances from the left end of the circuit pattern area 11 to the right end of the lower left mark area 16 are all the same (distance dx).

  The measurement patterns formed in each of the measurement mark regions 13 to 16 include a first line pattern along one side constituting the rectangular shot 1 and a second line along a direction perpendicular to the first line pattern. And a line pattern. Here, each line pattern is formed on the reticle as a white pattern (an opening pattern formed in the light shielding film). Therefore, areas other than the line pattern of each measurement mark area are covered with the light shielding film. In this case, the measurement mark regions 14 to 16 formed in the light shielding region 12 are preferably formed with a white pattern so that the outer periphery of each measurement mark region is also transferred onto the substrate. Similarly, when the base of the circuit pattern region 11 is a light-shielding film (white pattern reticle), it is preferable that the frame line of the measurement mark region 13 is formed in a white pattern.

  2 to 5 are enlarged plan views showing the measurement mark regions 13 to 16 on the reticle. Hereinafter, in the drawings, the left-right direction is referred to as the X direction and the up-down direction is referred to as the Y direction. In each figure, the white pattern area, which is a line pattern, is indicated by diagonal lines, and the outer periphery of the mark area is indicated by a solid line.

  As shown in FIG. 2, in the upper right mark region 13, a line pattern 131 extending in the Y direction (hereinafter referred to as Y direction pattern 131) and a line pattern 132 extending in the X direction (hereinafter referred to as X direction pattern 132). Is provided. The Y direction pattern 131 is formed at a distance X1 from the left end of the upper right mark region 13. Further, the X direction pattern 132 is formed at a distance Y1 from the lower end of the upper right mark region 13. In the present embodiment, the distance refers to the distance between the center lines.

  In addition, as shown in FIG. 3, the Y direction pattern 141 is formed in the upper left mark area 14 at a distance X2 (X2> X1) from the left end of the upper left mark area 14, and the X direction pattern 142 is the upper left mark. It is formed at a distance Y2 (Y2> Y1) from the lower end of the region 14. Further, in the lower left mark area 15, as shown in FIG. 4, a Y direction pattern 151 is formed at a distance X3 (X3> X2) from the left end of the upper left mark area 15, and the X direction pattern 152 is an upper left mark. It is formed at a position of a distance Y3 (Y3> Y2) from the lower end of the region 15. Similarly, the lower right mark region 16 includes a Y-direction pattern 161 formed at a distance X4 (X4> X3) from the left end of the lower right mark region 16, and a distance Y4 (Y4 from the lower end of the lower right mark region 16). > Y3) An X-direction pattern 162 formed at a position is provided (FIG. 5).

  The lengths in the Y direction of the Y direction patterns 131, 141, 151, 161 and the lengths in the X direction of the X direction patterns 132, 142, 152, 162 are the same for the respective measurement mark regions 13-16. It is preferable that the length is within the region and does not overlap each other. Further, the relationship among the distances X1, X2, X3, X4, Y1, Y2, Y3, and Y4 is not particularly limited, but in this embodiment, X2−X1 = X4−X3, and Y4 -Y3 = Y3-Y2 = Y2-Y1. X3-X2 is larger than the length in the X direction of the X direction pattern. The size of each of the mark regions 13 to 16 is a rectangle of about 80 μm × 150 μm.

  FIG. 6 is a schematic cross-sectional view of the substrate onto which the shot 1 of the reticle is transferred. As shown in FIG. 6, the substrate 10 has a base layer 6 made of a conductor film, an insulating film or the like formed on a semiconductor substrate 5 such as a silicon wafer, and a resist film 7 formed on the base layer 6. Yes. In the present embodiment, a negative type photoresist is used as the resist film 7, but a positive type photoresist can also be used. The semiconductor substrate 5 may be a product wafer on which semiconductor elements such as transistors and diodes are formed, or may be a dummy wafer or a monitor wafer for the purpose of measuring only overlay accuracy.

  The substrate 10 shown in FIG. 6 is exposed through the reticle using a step-and-repeat projection exposure apparatus, and the shot 1 is transferred to the resist film 7. In the following, the case where the reduction ratio of the projection exposure apparatus is 1/5 will be described, but any reduction ratio can be adopted.

  FIG. 7 is a plan view showing a shot layout on the substrate 10. In FIG. 7, only four shots 31 to 34 on the substrate 10 are shown for explanation, and the circuit pattern area and the outer shape of the light-shielding area and the measurement mark area of each shot are shown.

  In the shot layout shown in FIG. 7, for example, exposure is performed in the order of shot 31, shot 32, shot 33, and shot 34. That is, when the exposure of the shot 31 is completed, the exposure apparatus moves the substrate 10 in the −X direction (left direction) by the width of the circuit pattern region 11 in the X direction for the exposure of the shot 32. When the exposure of the shot 32 is completed, the exposure apparatus moves the substrate 10 in the −Y direction (downward) by the width of the circuit pattern region 11 in the Y direction for the exposure of the shot 33, and at the same time the X direction of the circuit pattern region 11 Moves in the X direction (right direction) by the width of. When the exposure of the shot 33 is completed, the exposure apparatus moves the substrate 10 in the −X direction by the width of the circuit pattern region 11 in the X direction for the exposure of the shot 34.

  Here, when the width in the X direction of the circuit pattern region 11 on the reticle is x μm, the stepping amount in the X direction of the exposure apparatus is x / 5 μm. When the width of the circuit pattern region 11 on the reticle in the Y direction is y μm, the stepping amount in the Y direction of the exposure apparatus is y / 5 μm.

  When four different shots adjacent to each other are transferred onto the substrate 10 as described above, as shown in FIG. 7, a region 41 in which the corners of the shots 31 to 34 overlap (hereinafter referred to as a four-shot overlapping region 41). Is formed). At this time, the upper right mark area 13 of the shot 31, the upper left mark area 14 of the shot 32, the lower right mark area 16 of the shot 33, and the lower left mark area 15 of the shot 34 are overlapped and exposed in the 4-shot overlapping area 41. ing. Therefore, when the resist film 7 is developed after the exposure is completed, a resist pattern in which the mark regions 13 to 16 on the reticle overlap is formed.

  FIG. 8 is a plan view of a resist pattern formed in a region 42 (hereinafter referred to as an overlap measurement mark region 42) in which the measurement mark regions 13 to 16 are overlapped with the 4-shot overlap region 41. As shown in FIG. 8, on the substrate 10, resist patterns 133, 143, 153, and 163 corresponding to the Y-direction patterns 131, 141, 151, and 161 in the mark areas 13 to 16, and the mark areas 13 to Resist patterns 134, 144, 154, 164 corresponding to the X direction patterns 132, 142, 152, 162 in 16 are formed.

  As described above, in the exposure by the exposure apparatus, the pattern on the reticle is transferred at 1/5 times. Therefore, when the mark regions 13 to 16 are transferred without causing overlay deviation, the distances from the left end of the overlap measurement mark region 42 to the Y-direction resist patterns 133, 143, 153, and 163 are RX1, RX2, Assuming RX3 and RX4, RX1 = X1 / 5, RX2 = X2 / 5, RX3 = X3 / 5, and RX4 = X4 / 5. Similarly, when the mark areas 13 to 16 are transferred without causing overlay displacement, the distances from the lower end of the overlap measurement mark area 42 to the X-direction resist patterns 134, 144, 154, and 164 are set to RY1 and RY2, respectively. , RY3, RY4, RY1 = Y1 / 5, RY2 = Y2 / 5, RY3 = Y3 / 5, and RY4 = Y4 / 5. As described above, in the present embodiment, since the resist film 7 is a negative photoresist, a pattern made of the resist film 7 is formed in the hatched region in FIG.

  Subsequently, the base layer 6 is etched using the resist pattern formed on the substrate 10 as described above as a mask, and each resist pattern is transferred to the base layer 6. Thereafter, the resist pattern is removed, and a material film such as a conductor film or an insulating film is formed on the underlying layer 6 to which the pattern has been transferred. In the next step, a pattern is transferred to the formed material film.

  FIG. 9 is a plan view showing a shot 2 on a reticle used in the next process. The shot 2 may be formed on a transparent substrate different from the shot 1 or may be formed at a different position on the same transparent substrate.

  As shown in FIG. 9, the reticle shot 2 has a circuit pattern region 21 and a light-shielding film arranged in an L shape over a predetermined width from the left and lower sides of the shot 2 in the same manner as the shot 1 described above. A light shielding region 22 is provided.

  Measurement mark regions 23, 24, 25, and 26 in which patterns for overlay accuracy measurement are arranged are also provided at the four corners of shot 2, as in shot 1. The area sizes of the measurement mark areas 23 to 26 are all the same as the measurement mark areas 13 to 16 of the shot 1.

  9, the distance from the upper end of shot 2 to the upper end of upper right mark area 23, the distance from the upper end of shot 2 to the upper end of upper left mark area 24, and the lower end of circuit pattern area 21 to lower left mark area 25 And the distance from the lower end of the circuit pattern area 21 to the upper end of the lower right mark area 26 are all the same (distance dy). Further, the distance from the right end of shot 2 to the right end of upper right mark area 23, the distance from the right end of shot 2 to the right end of lower right mark area 26, the distance from the left end of circuit pattern area 21 to the right end of upper left mark area 24, The distance from the left end of the circuit pattern area 21 to the right end of the lower left mark area 26 is also the same (distance dx).

  The measurement patterns formed in the measurement mark regions 23 to 26 include a first line pattern along one side constituting the rectangular shot 2 and a second line along a direction perpendicular to the first line pattern. Pattern. Similar to shot 1, each line pattern is formed on the reticle as a white pattern.

  10 to 13 are enlarged plan views showing the measurement mark regions 23 to 26 on the reticle. In each figure, the white pattern area, which is a line pattern, is indicated by diagonal lines, and the outer periphery of the measurement mark area is indicated by a solid line.

  As shown in FIG. 10, the upper right mark area 23 of the shot 2 includes a Y direction pattern 231 and an X direction pattern 232. The Y direction pattern 231 is formed at a distance X5 from the left end of the upper right mark area 23, and the X direction pattern 232 is formed at a distance Y5 from the lower end of the upper right mark area 23. In the present embodiment, the Y-direction pattern 231 is shifted from the Y-direction pattern 131 of the upper right mark area 13 of the shot 1 by the distance A in the right direction in the drawing (X5 = X1 + A). Further, the X direction pattern 232 is shifted from the X direction pattern 132 of the upper right mark area 13 of the shot 1 by a distance B in the upward direction in the figure (Y5 = Y1 + B). Similarly, a Y-direction pattern 241 is formed in the upper left mark area 24 at a distance X6 (X6 = X2 + A) from the left end of the upper left mark area 24 as shown in FIG. An X-direction pattern 252 is formed at a position at a distance Y6 (Y6 = Y2 + B) from the distance.

  The lower left mark area 25 includes a Y-direction pattern 251 formed at a distance X7 (X7 = X3 + A) from the left end of the lower left mark area 26 and a position Y7 (Y7 = Y3 + B) from the lower end of the lower left mark area 25. And an X-direction pattern 252 formed in (FIG. 12). Similarly, the lower right mark area 26 includes a Y direction pattern 261 formed at a distance X8 (X8 = X4 + A) from the left end of the lower right mark area 26, and a distance Y8 (Y8 = Y8 from the lower end of the lower right mark area 26). Y direction pattern 262 formed at the position of Y4 + B) (FIG. 13).

  The lengths in the Y direction of the Y direction patterns 231, 241, 251, and 261, and the lengths in the X direction of the X direction patterns 232, 242, 252, and 262 are within the measurement mark regions 23 to 26. It is preferable that the lengths do not overlap each other. The distance A is arbitrary as long as the Y direction patterns 231, 241, 251, and 261 do not overlap the Y direction patterns 131, 141, 151, and 161 of the shot 1. Similarly, the distance B may be a distance that does not allow the X-direction patterns 232, 242, 252, and 262 to overlap the Y-direction patterns 132, 142, 152, and 162 of the shot 1. In this embodiment, A = (X2-X1) / 2 and B = (Y2-Y1) / 2.

  FIG. 14 is a schematic cross-sectional view of the substrate onto which the shot 2 is transferred. As shown in FIG. 14, a new material film 8 is formed on the base layer 6 to which the pattern has been transferred as described above, and a resist film 17 is formed on the material film 8. ing. In this embodiment, a negative type photoresist is used as the resist film 17, but a positive type photoresist can also be used.

  The substrate 10 shown in FIG. 14 is exposed through the shot 2 using the projection exposure apparatus, and the pattern on the reticle is transferred to the resist film 17. The shot layout on the substrate 10 is the same as in FIG.

  Therefore, a 4-shot overlapping region 41 of shot 2 is formed on the substrate 10 (see FIG. 7). At this time, the upper right mark area 23 of the shot 31, the upper left mark area 24 of the shot 32, the lower right mark area 26 of the shot 33, and the lower left mark area 25 of the shot 34 are overlapped and exposed in the 4-shot overlapping area 41. The Therefore, when the resist film 17 is developed after the exposure is completed, a resist pattern in which the mark areas 23 to 26 of the shot 2 are overlapped is formed.

  FIG. 15 is a plan view of a resist pattern formed in the overlap measurement mark region 42 of the 4-shot overlap region 41. FIG. As shown in FIG. 15, on the substrate 10, resist patterns 233, 243, 253, 263 corresponding to the Y-direction patterns 231, 241, 251, and 261 in the mark regions 23 to 26, and the mark regions 23 to 26, respectively. 26, resist patterns 234, 244, 254, and 264 corresponding to the X-direction patterns 232, 242, 252, and 262 are formed.

  As described above, in the exposure by the exposure apparatus, the pattern on the reticle is transferred at 1/5 times. Therefore, when the mark areas 23 to 26 are transferred without causing overlay displacement, the distances from the left end of the overlap measurement mark area 42 to the Y-direction resist patterns 233, 243, 253, 263 are RX5, RX6, Assuming RX7 and RX8, RX5 = X5 / 5, RX6 = X6 / 5, RX7 = X7 / 5, and RX8 = X8 / 5. Similarly, when each of the mark areas 23 to 26 is transferred without causing an overlay error, the distance from the lower end of the overlap measurement mark area 42 to each X-direction resist pattern is set to RY5, RY6, RY7, Assuming RY8, RY5 = Y5 / 5, RY6 = Y6 / 5, RY7 = Y7 / 5, and RY8 = Y8 / 5. As described above, in the present embodiment, since the resist film 17 is a negative photoresist, a pattern made of the resist film 17 is formed in the region indicated by the oblique lines in FIG.

  In the present embodiment, the resist pattern shown in FIG. 8 is transferred to the base layer 6 in the overlap measurement mark region 42. Therefore, when the actual substrate 10 is observed from above, the pattern of the underlayer 6 can be confirmed in addition to the resist pattern shown in FIG. FIG. 16 is a plan view showing such a pattern of the underlayer 6 and the resist pattern of FIG. In FIG. 15, the patterns of the underlayers corresponding to the resist patterns 133, 143, 153, 163, 134, 144, 154, and 164 shown in FIG. 8 are respectively the underlayer patterns 135, 145, 155, 165, 136, 146, 156, 166.

  As described above, each line pattern of shot 2 is arranged so as not to overlap with each line pattern of shot 1. For this reason, when the exposure via the shot 1 and the exposure via the shot 2 are normally superimposed, the underlying layer pattern is located between the resist patterns formed by the shot 2. The distance between the Y-direction patterns (for example, between the underlayer pattern 145 and the resist pattern 243) corresponding to the measurement mark region at the same position in the shot 1 and the shot 2 is A / 5 in design. It becomes. In addition, the distance between the X direction patterns (for example, between the underlayer pattern 146 and the resist pattern 244) corresponding to the measurement mark region at the same position in the shot 1 and the shot 2 is B / 5 in design. It becomes.

  Therefore, for example, by using a pattern measuring machine of an optical image processing method, the distance between these actually formed patterns is measured and compared with the design value (A / 5 or B / 5). Superposition accuracy can be obtained.

  For example, when the distance RX5-RX1 between the base layer pattern 135 corresponding to the Y direction pattern in the upper right mark region and the resist pattern 233 is A / 5 + α1, the overlay deviation amount of the shots in the X direction is α1. Further, when the distance RY5-RY1 between the base layer pattern 136 corresponding to the X direction pattern in the upper right mark region and the resist pattern 234 is B / 5 + β1, the shot overlay deviation amount in the Y direction is β1. That is, the overlay deviation amount at the upper right of the shot is measured as (X, Y) = (α1, β1).

  When the distance between the base layer pattern 145 and the resist pattern 243 is RX6-RX2 = A / 5 + α2, and the distance between the base layer pattern 146 and the resist pattern 244 is RY6-RY2 = B / 5 + β2, The overlay displacement amount is measured as (X, Y) = (α2, β2).

  Further, when the distance between the underlayer pattern 155 and the resist pattern 253 is RX7−RX3 = A / 5 + α3 and the distance between the underlayer pattern 156 and the resist pattern 254 is RY7−RY3 = B / 5 + β3, The overlay deviation amount is measured as (X, Y) = (α3, β3).

  Similarly, when the distance between the underlayer pattern 165 and the resist pattern 263 is RX8−RX4 = A / 5 + α4 and the distance between the underlayer pattern 166 and the resist pattern 264 is RY8−RY4 = B / 5 + β4, the shot right The amount of overlay displacement below is measured as (X, Y) = (α4, β4).

  As described above, according to the present embodiment, by measuring the overlay accuracy measurement pattern at one place, the overlay accuracy measurement pattern at the four corners of the shot formed in the previous process and the shot formed in the upper layer The overlay deviation amount of the overlay accuracy measurement pattern at the four corners can be measured. That is, by measuring the superposition accuracy measurement pattern at one place, it is possible to measure the overlay deviation between the shot of the base layer and the shot of the upper layer (exposure shot) at the four corners of the shot. Therefore, by calculating the placement error such as the projection magnification error and the rotation error at the time of exposure based on the measurement result, it is not the placement error only in the same layer as in the past, but the placement with respect to the pattern formed in the lower layer The error can be determined directly.

  The overlay deviation amount obtained as described above is stored in the exposure apparatus together with the coordinates on the substrate for each reticle, for example. Then, according to the reticle to be used, the exposure apparatus reads the overlay deviation amount, and performs exposure by adjusting the shot positioning mechanism and the optical system so that the overlay deviation amount is reduced. For example, when there are five measurement points of the overlapping measurement mark region 42 on the substrate 10, the arithmetic unit provided in the exposure apparatus calculates an average value for each directional component at each position (such as a grazing amount in the upper right X direction). Then, exposure is performed on all shots in a state where the average deviation amount is adjusted to be reduced. Thereby, stable exposure with small projection magnification error and rotation error during exposure can be realized in the production of semiconductor devices.

  In the above description, the case of exposing the upper layer 8 formed immediately above the underlayer 6 has been described. However, as shown in FIG. 17, the upper layer 8 formed by sandwiching another layer 9 on the underlayer 6. As a matter of course, it is possible to acquire an arrangement error with respect to the underlayer 6.

  Further, from the viewpoint of efficiently performing the measurement, it is preferable that the arrangement error with respect to the lower layer is acquired only for several shots on the substrate 10 as described above, and the exposure apparatus performs global alignment. However, it goes without saying that the present invention can also be applied to die-by-die alignment in which an arrangement error with respect to the lower layer is measured for all shots and an optical system or the like is adjusted for each shot.

  Further, in the above description, in shot 1 and shot 2, the distance between the Y-direction patterns of the measurement mark regions arranged at the same position on the reticle is set as the distance A. However, the line patterns may be arranged so that they do not overlap when all the measurement mark areas overlap. That is, the interval between the Y-direction line patterns may be different for each measurement mark region arranged at the same position on the reticle. Similarly, the interval between the X-direction line patterns may be different for each measurement mark region arranged at the same position on the reticle.

  In the above description, a case has been described in which line patterns extending in two directions parallel to the sides constituting a rectangular shot are arranged in each measurement mark region in order to directly measure the overlay error of shots. However, if the overlay deviation in two different directions can be acquired in the same plane, the overlay deviation in the X direction and the Y direction can be obtained by calculation (coordinate system conversion). That is, the same effect can be obtained if the line patterns arranged in each measurement mark region are arranged in two different directions.

  Furthermore, in the above description, as a particularly preferable mode, the measurement pattern of each measurement mark region is constituted by a line pattern. However, the shape of the measurement pattern may be a shape having a line portion capable of measuring the relative distance between the measurement patterns, and is not necessarily a line pattern having the same width.

  By the way, in the above, the overlay deviation between the base layer pattern transferred to the base layer 6 on the substrate 10 and the resist pattern transferred to the resist film 17 formed on the base layer 6 through the material film 8 is caused. The example of measuring and feeding back to the projection exposure apparatus was explained. In this case, the measured overlay error is reflected in the subsequent exposure in the projection exposure apparatus. However, if a configuration in which the projection exposure apparatus stores in advance the coordinates (hereinafter referred to as design coordinates) when all the measurement mark areas are transferred without causing an overlay error, the pattern of the upper layer is exposed. In addition, it is possible to reduce misalignment.

  As shown in FIG. 8, when the mark areas 13 to 16 are transferred without causing overlay displacement, the distance from the left end of the overlap measurement mark area 42 of each Y direction pattern 133, 143, 153, 163 is By design, RX1 = X1 / 5, RX2 = X2 / 5, RX3 = X3 / 5, and RX4 = X4 / 5. Further, the distance from the lower end of the overlap measurement mark area 42 of each X direction pattern 134, 144, 154, 164 is RY1 = Y1 / 5, RY2 = Y2 / 5, RY3 = Y3 / 5, RY4 = Y4 by design. / 5. Then, these resist patterns are transferred to the base layer 6 to form base layer patterns 135, 145, 155, 165 in the Y direction and base layer patterns 136, 146, 156, 166 in the X direction. On the underlayer pattern, as described above, the material film 8 and the resist film 17 are sequentially formed.

  Here, the design coordinates of the Y-direction underlayer patterns 135, 145, 155, and 165 when the projection exposure apparatus aligns the substrate 10 to the exposure position by a known alignment method are EX1, EX2, respectively. , EX3 and EX4. Note that EX1, EX2, EX3, and EX4 are X coordinates in a coordinate system (hereinafter referred to as an exposure coordinate system) used by the projection exposure apparatus for exposure position alignment. In addition, it is assumed that the design coordinates of the X-direction underlayer patterns 136, 146, 156, and 166 in this state are EY1, EY2, EY3, and EY4, respectively. EY1, EY2, EY3, and EY4 are Y coordinates in the exposure coordinate system.

  If there is an overlay error during the formation of the underlayer pattern, the Y-direction underlayer patterns 135, 145, 155, 165 and the X-direction underlayer patterns 136, 146, 156, 166 are located at positions different from the design coordinates. It is formed. Therefore, when the projection exposure apparatus performs exposure of the upper layer pattern, for example, the Y-direction underlayer patterns 135, 145, 155, 165, and X are used by using an optical image processing type pattern measuring machine provided in the projection exposure apparatus. By measuring the coordinates of the direction base layer patterns 136, 146, 156, and 166 in the exposure coordinate system, the overlay accuracy can be obtained.

  FIG. 18 is a diagram showing a base layer pattern formed in the overlapping mark region 42 of the substrate 10. In FIG. 18, the design coordinates of each underlying layer pattern are indicated by broken lines.

  As shown in FIG. 18, it is assumed that the X coordinate in the exposure coordinate system of the Y-direction underlayer pattern 135 is PX1, and PX1 = EX1 + γ1. At this time, assume that the Y coordinate in the exposure coordinate system of the X-direction underlayer pattern 136 is PY1, and PY1 = EY1 + δ1. At this time, the overlay deviation amount at the upper right of the shot is measured as (X, Y) = (γ1, δ1).

  Further, when the X coordinate PX2 in the exposure coordinate system of the Y-direction underlayer pattern 145 is PX2 = EX2 + γ2, and the Y coordinate PY2 in the exposure coordinate system of the X-direction underlayer pattern 146 is PY2 = EY2 + δ2, the superposition on the upper left of the shot is performed. The misalignment amount is measured as (X, Y) = (γ2, δ2).

  Further, when the X coordinate PX3 in the exposure coordinate system of the Y-direction underlayer pattern 155 is PX3 = EX3 + γ3, and the Y coordinate PY3 in the exposure coordinate system of the X-direction underlayer pattern 156 is PY3 = EY3 + δ3, the overlap in the lower left of the shot is performed. The misalignment amount is measured as (X, Y) = (γ3, δ3).

  Similarly, when the Y coordinate PX4 in the exposure coordinate system of the Y direction ground layer pattern 165 is PX4 = EX4 + γ4, and the Y coordinate PY4 in the exposure coordinate system of the X direction ground layer pattern 166 is PY4 = EY4 + δ4, The overlay deviation amount is measured as (X, Y) = (γ4, δ4).

  The overlay displacement amount obtained as described above is measured, for example, for 5 shots on the substrate 10, for example, and the overlay displacement amount at each position (upper right, upper left, lower left, lower right) of the projection exposure apparatus. The average value of is calculated. Then, when the upper layer pattern is exposed while being superimposed on the lower layer pattern on the substrate 10, the projection exposure apparatus performs shot positioning so that the overlay deviation amount decreases based on the calculated average value of the overlay deviation amount. Exposure is performed by adjusting the mechanism and optical system. Thereby, stable exposure with small projection magnification error and rotation error during exposure can be realized in the production of semiconductor devices.

  Therefore, according to the present method, as in the above-described method, it is possible to measure the overlay deviation of the shots of the underlayer at the four corners of the shot by measuring one overlay accuracy measurement pattern. Then, by correcting the position of the exposure shot for forming the upper layer pattern based on the measurement result, the correction of the pattern formed in the lower layer is not performed based on the arrangement error only in the same layer as in the prior art. Correction based on the placement error can be performed.

  Of course, this method can also be applied to a case where a pattern is transferred to an upper layer 8 formed by sandwiching another layer 9 on the base layer 6 as shown in FIG. Further, exposure shot position correction for forming an upper layer pattern may be performed for each shot.

  As described above, according to the present invention, since the placement error for the lower layer shot can be directly obtained, the placement error is fed back to the exposure apparatus, and the exposure apparatus is adjusted so that the placement error is reduced. High precision shot superposition can be performed. Further, since the arrangement error can be obtained by measurement at one place, the arrangement error for the lower layer shot can be obtained in a very short time without increasing the number of measurement points.

  In addition, this invention is not limited to embodiment mentioned above, A various deformation | transformation and application are possible in the range with the effect of this invention. For example, in the above description, an example in which only measurement mark regions for obtaining shot overlay accuracy between a pair of reticles are formed at the four corners of a shot. However, in general, many reticles are required to manufacture a semiconductor integrated circuit. For this reason, not only between a pair of reticles but also a larger number of shot overlay measurement marks between reticles are required. In this case, these overlay accuracy measurement patterns may be arranged at the four corners of the shot without overlapping each other.

  INDUSTRIAL APPLICABILITY The present invention has an effect that the upper and lower layer shot overlay deviation can be measured with high accuracy and at high speed, and is useful as a technique for measuring shot overlay accuracy in a lithography process.

1 is a schematic plan view showing a reticle according to an embodiment of the present invention. The top view which shows the upper right mark area | region of the reticle of one Embodiment of this invention The top view which shows the upper left mark area | region of the reticle of one Embodiment of this invention The top view which shows the lower left mark area | region of the reticle of one Embodiment of this invention The top view which shows the lower right mark area | region of the reticle of one Embodiment of this invention Sectional drawing which shows the board | substrate with which the pattern of the reticle of one Embodiment of this invention is transcribe | transferred Plan view showing an example of shot layout The top view which shows the pattern formed with the reticle of one Embodiment of this invention The top view which shows an example of the reticle of one Embodiment of this invention The top view which shows the upper right mark area | region of the reticle of one Embodiment of this invention The top view which shows the upper left mark area | region of the reticle of one Embodiment of this invention The top view which shows the lower left mark area | region of the reticle of one Embodiment of this invention The top view which shows the lower right mark area | region of the reticle of one Embodiment of this invention Sectional drawing which shows the board | substrate with which the pattern of the reticle of one Embodiment of this invention is transcribe | transferred The top view which shows the pattern formed with the reticle of one Embodiment of this invention The top view which shows the resist pattern and lower layer pattern which were formed with the reticle of one Embodiment of this invention Sectional drawing which shows the board | substrate with which the pattern of the reticle of one Embodiment of this invention is transcribe | transferred The top view which shows the pattern formed with the reticle of other embodiment of this invention

Explanation of symbols

1, 2 Shot on reticle 5 Semiconductor substrate 6 Underlayer 7, 17 Resist film 8 Upper layer 10 Substrate 11, 21 Circuit pattern region 12, 22 Light-shielding region 13, 23 Upper right measurement mark region 14, 24 Upper left measurement mark region 15, 25 Lower left measurement mark area 16, 26 Lower right measurement mark area 31, 32, 33, 34 Shot 41 on substrate 4-shot overlap area 131, 141, 151, 161 Y direction pattern (white pattern)
132, 142, 152, 162 X direction pattern (white pattern)
231, 241, 251, 261 Y direction pattern (white pattern)
232, 242, 252, 262 X direction pattern (white pattern)

Claims (10)

A photomask provided with a pattern for measuring shot overlay accuracy of a lower layer pattern and an upper layer pattern transferred onto a substrate by a step-and-repeat exposure apparatus,
A rectangular shot,
Measurement mark areas provided at least one at each of the four corners of the shot;
The measurement pattern including a line pattern extending in a first direction and a line pattern extending in a second direction different from the first direction, formed in each measurement mark region;
With
A photomask, wherein the line patterns belonging to each measurement mark region are arranged so as not to overlap each other when all the measurement mark regions located at different corners overlap each other.   The photomask according to claim 1, wherein the first direction and the second direction are parallel to sides forming the shot. A pair of photomasks comprising a lower layer photomask and an upper layer photomask comprising the photomask of claim 1,
When the measurement mark regions located at different corners on the lower photomask and the measurement mark regions located at different corners on the upper photomask all overlap, the line patterns belonging to the measurement mark regions are Photomasks arranged so that they do not overlap each other. A shot overlay accuracy measurement method for measuring shot overlay accuracy of a lower layer pattern and an upper layer pattern transferred onto a substrate by a step-and-repeat exposure apparatus,
The measurement of the four corners is performed using a lower layer photomask having measurement mark regions in which a line pattern extending in a first direction and a line pattern extending in a second direction different from the first direction are formed at the four corners of the rectangular shot. Forming a lower layer pattern with the mark areas overlapping;
Forming an upper layer film on the lower layer pattern;
The measurement mark regions at the four corners and the lower layer using a photomask for upper layers provided with measurement mark regions in which line patterns extending in the first direction and line patterns extending in the second direction are formed at the four corners of the rectangular shot A step of transferring the upper layer pattern in a state where the lower layer measurement mark region overlapped with is overlapped,
The relative distance between the lower line pattern extending in the first direction and the upper line pattern extending in the first direction formed by the above steps, and the second direction formed by the above steps. Measuring a relative distance between an extended lower line pattern and an upper line pattern extending in the second direction;
A method for measuring the accuracy of shot superposition.   5. The shot overlay accuracy measuring method according to claim 4, wherein the relative interval is a relative interval between line patterns belonging to a measurement mark region located at the same corner in the lower layer photomask and the upper layer photomask.   The shot overlay accuracy measuring method according to claim 4, wherein the first direction and the second direction are parallel to sides forming the shot. A method of manufacturing a semiconductor device that transfers a lower layer pattern and an upper layer pattern onto a substrate by a step-and-repeat exposure apparatus,
The measurement of the four corners is performed using a lower layer photomask having measurement mark regions in which a line pattern extending in a first direction and a line pattern extending in a second direction different from the first direction are formed at the four corners of the rectangular shot. Forming a lower layer pattern with the mark areas overlapping;
Forming an upper layer film on the lower layer pattern;
The measurement mark regions at the four corners and the lower layer using a photomask for an upper layer provided with measurement mark regions having line patterns extending in the first direction and line patterns extending in the second direction at the four corners of the rectangular shot A step of transferring the upper layer pattern in a state where the lower layer measurement mark region overlapped with is overlapped,
The relative distance between the lower line pattern extending in the first direction and the upper line pattern extending in the first direction formed by the above steps, and the second direction formed by the above steps. Measuring a relative distance between an extended lower line pattern and an upper line pattern extending in the second direction;
Transferring the subsequent upper layer pattern in a state where the difference between the measured relative interval and the design value of the relative interval is reduced;
A method for manufacturing a semiconductor device, comprising:   8. The method of manufacturing a semiconductor device according to claim 7, wherein the relative interval is a relative interval between line patterns belonging to a measurement mark region located at the same corner in the lower layer photomask and the upper layer photomask.   The method for manufacturing a semiconductor device according to claim 7, wherein the first direction and the second direction are parallel to a side constituting the shot. A method of manufacturing a semiconductor device that transfers a lower layer pattern and an upper layer pattern onto a substrate by a step-and-repeat exposure apparatus,
The measurement at the four corners is performed using a lower layer photomask having measurement mark regions in which a line pattern extending in a first direction and a line pattern extending in a second direction different from the first direction are formed at the four corners of the rectangular shot. Forming a lower layer pattern with the mark areas overlapping;
Forming an upper layer film on the lower layer pattern;
Measuring the position of each lower layer pattern in a state where the substrate is disposed at a position where the upper layer pattern is exposed;
Calculating the difference between the position where each lower layer pattern should be designed in the arrangement state of the substrate and the position of each measured lower layer pattern;
Exposing the upper layer pattern with the difference decreasing; and
A method for manufacturing a semiconductor device, comprising:

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