JP5397596B2 - Flare measurement method and exposure method - Google Patents

Description

  The present invention relates to a flare measurement method for measuring flare information of a projection optical system and an exposure method using the flare measurement method.

  In an exposure apparatus used in a photolithography process for manufacturing various devices (electronic devices) such as semiconductor devices, scattered light generated by the roughness of the surface of the optical member constituting the projection optical system is caused by the original light flux. If a flare as image blur is formed around the image to be imaged, the contrast of the image is lowered and the imaging characteristics are affected. Therefore, when evaluating the imaging characteristics of the projection optical system, it is necessary to measure the flare. Also, in an exposure apparatus (EUV exposure apparatus) that uses extreme ultraviolet light (Extreme Ultraviolet Light: hereinafter referred to as EUV light) as the exposure light, almost all optical members including the reticle are reflective members, and flare However, since the required resolution increases, flare needs to be measured with high accuracy.

  As a conventional flare measurement method, for example, an image of an evaluation pattern including an annular transmission part (or reflection part) is exposed through a projection optical system, and an exposure amount when the image of the transmission part is exposed, and There is known a Kirk method (Kirk method) for evaluating flare from a ratio to an exposure amount when the center of an image of a light shielding portion inside is exposed (for example, see Patent Document 1).

JP 2007-234716 A

  Flares include short-distance flare that spreads over a narrow area and long-distance flare that spreads outside the exposure area of the image plane of the projection optical system, and conventional flare measurement methods can easily measure short-distance flare. Long-distance flare is difficult to measure because the area of small light intensity extends far away. Long distance flare may also affect adjacent shot areas on the substrate being exposed. Therefore, in order to further increase the exposure accuracy in the future, it is necessary to accurately evaluate long-distance flare.

  In view of such circumstances, it is an object of the present invention to provide a flare measurement technique capable of accurately measuring flare information over a wide range such as a long-distance flare, and an exposure technique using the flare measurement technique.

A first flare measurement method according to the present invention is a method for measuring flare information of a projection optical system, wherein an image of a first pattern in which line portions and space portions are periodically formed via the projection optical system, or Exposing one of the images of the second pattern having a shape different from the first pattern onto the first photosensitive substrate and the image of the first pattern or the image of the second pattern via the projection optical system; And exposing the other one of the first pattern image and the second pattern image exposed on the first photosensitive substrate to one of the first pattern image and the first pattern of the first photosensitive substrate. Measuring the line width of the image of the line portion or the space portion at a plurality of positions of the pattern image, exposing the image of the first pattern on the second photosensitive substrate, and the second The first exposed to the photosensitive substrate A step of measuring the line width of the image of the line section or the space portion of the image of the pattern, the step of obtaining the flare information from the measurement result of the line width, only contains the image of the first pattern and the second The step of exposing on the photosensitive substrate is to expose the image of the first pattern at different positions on the second photosensitive substrate while changing the exposure amount, and to expose the line exposed on the second photosensitive substrate. The step of measuring the line width of the image of the portion or the space portion includes the step of obtaining the relationship between the line width and the exposure amount, and the step of obtaining the flare information was measured on the first photosensitive substrate. A line measured by the second photosensitive substrate, including a step of obtaining an exposure amount at the plurality of positions of the first photosensitive substrate based on a relationship between the line width and the line width and the exposure amount. Comparison of the width with the line width measured on the first photosensitive substrate More, and requests the flare information.
A second flare measurement method according to the present invention is a method of measuring flare information of a projection optical system, and is an image of a first pattern in which line portions and space portions are periodically formed via the projection optical system. Or exposing one of the images of the second pattern having a shape different from that of the first pattern onto the first photosensitive substrate, and the image of the first pattern or the second pattern via the projection optical system. Exposing the other of the first image to one of the first pattern image or the second pattern image exposed on the first photosensitive substrate and exposing the first photosensitive substrate on the first photosensitive substrate. A step of measuring the line width of the image of the line portion or the space portion at a plurality of positions of the image of the first pattern, and a step of obtaining the flare information from the measurement result of the line width. The first image of In the step of exposing the photosensitive substrate, the first pattern and the first photosensitive substrate are moved in the scanning direction with respect to the projection optical system, and an image of the first pattern is used as the first photosensitive property. The step of scanning exposure of the substrate and exposing the image of the second pattern onto the first photosensitive substrate includes the step of stopping the second pattern and the first photosensitive substrate, and then image of the second pattern. Then, the first photosensitive substrate is exposed.

  An exposure method according to the present invention is an exposure method in which a pattern is formed on an object via a projection optical system, and the flare information of the projection optical system is measured using the flare measurement method of the present invention. Processing according to the measurement result is performed.

  According to the flare measurement method of the present invention, for example, when an image of the first pattern is exposed and the image of the second pattern is exposed on a part of the image of the first pattern, the first image outside the image of the second pattern is exposed. The influence of flare appears in the image of one pattern, and the line width of the line portion or the space portion of the image of the first pattern changes. Therefore, flare can be evaluated from the change in line width.

It is sectional drawing which shows schematic structure of the exposure apparatus of an example of embodiment of this invention. (A) is a bottom view showing a pattern on the test reticle R1, (B) is an enlarged view showing a part of the L & S pattern in FIG. 2 (A), and (C) is a bottom view showing a pattern of the test reticle R2. is there. It is a flowchart which shows an example of the measurement operation | movement of the flare of a projection optical system. (A) is a plan view showing an image of a pattern of a test reticle R1 exposed on a plurality of shot areas on the wafer W1, and (B) is a plan view showing a resist pattern formed on the wafer W1 after development. (A) is a plan view showing a pattern image of the test reticle R1 exposed on the wafer W2, (B) is a plan view showing an image of the pattern of the test reticle R2 exposed on the wafer W2, and (C) is a plan view. It is a top view which shows the image formed by double exposure on the wafer W2. It is an enlarged plan view showing a resist pattern formed by development on wafer W2 after double exposure. It is a flowchart which shows an example of the manufacturing process of an electronic device.

An exemplary embodiment of the present invention will be described with reference to the drawings.
FIG. 1 is a cross-sectional view schematically showing the overall configuration of the exposure apparatus 100 of the present embodiment. The exposure apparatus 100 uses EUV light (Extreme Ultraviolet Light) such as 11 nm or 13 nm as the exposure light (exposure illumination light or exposure beam) EL within a wavelength range of about 100 nm or less and about 3 to 50 nm. Device. In FIG. 1, an exposure apparatus 100 includes a laser plasma light source 10 that generates a pulse of exposure light EL, and an illumination optical system ILS that illuminates a pattern surface (here, the lower surface) of a reticle R (mask) with an illumination region 27R. A reticle stage RST that moves the reticle R, and a projection optical system PO that projects an image of a pattern in the illumination area 27R of the reticle R onto a wafer W (photosensitive substrate) coated with a resist (photosensitive material). ing. Further, the exposure apparatus 100 includes a wafer stage WST that moves the wafer W, a main control system 31 that includes a computer that controls the overall operation of the apparatus, and the like.

In this embodiment, since EUV light is used as the exposure light EL, the illumination optical system ILS and the projection optical system PO are composed of reflective optical members such as a plurality of mirrors except for a specific filter or the like (not shown). The reticle R is also a reflection type. For example, the reflective optical member is obtained by processing a surface of a member made of quartz (or a metal having high heat resistance) into a predetermined curved surface or a plane with high accuracy, and then molybdenum (Mo) and silicon (Si) on the surface. A multilayer film (an EUV light reflecting film) is formed as a reflecting surface. The multilayer film may be another multilayer film in which a substance such as ruthenium (Ru) or rhodium (Rh) and a substance such as Si, beryllium (Be), or carbon tetraboride (B ₄ C) are combined. . The reticle R is formed, for example, by forming a multilayer film on the surface of a quartz substrate to form a reflective surface (reflective film), and on the reflective surface, tantalum (Ta), nickel (Ni), chromium (Cr), or the like. A transfer pattern is formed by an absorption layer made of a material that absorbs EUV light. A metal can also be used as the reticle R substrate.

Further, in order to prevent the EUV light from being absorbed by the gas, the exposure apparatus 100 is accommodated in the box-like vacuum chamber 1 as a whole, and the space in the vacuum chamber 1 is evacuated through the exhaust pipes 32Aa, 32Ba and the like. Large vacuum pumps 32A, 32B and the like are provided. Further, a plurality of sub-chambers (not shown) are provided in order to further increase the degree of vacuum on the optical path of the exposure light EL in the vacuum chamber 1. As an example, the pressure in the vacuum chamber 1 is about 10 ⁻⁵ Pa, and the pressure in the subchamber (not shown) that houses the projection optical system PO in the vacuum chamber 1 is about 10 ⁻⁵ to 10 ⁻⁶ Pa.

  Hereinafter, in FIG. 1, the Z axis is taken in the normal direction of the surface (bottom surface of the vacuum chamber 1) on which the wafer stage WST is placed, and a plane perpendicular to the Z axis (in this embodiment, a plane substantially parallel to the horizontal plane) In the following description, the X axis is perpendicular to the paper surface of FIG. 1 and the Y axis is parallel to the paper surface of FIG. In this embodiment, when the reticle R is irradiated with the exposure light EL, an illumination region 27R is formed on the reticle R. As shown in FIG. 2B, the illumination area 27R has an arc shape elongated in the X direction (non-scanning direction). During normal exposure, the reticle R and the wafer W are in the Y direction (with respect to the projection optical system PO). Scanning is performed in synchronization with the scanning direction.

  First, the laser plasma light source 10 includes a high-power laser light source (not shown), a condensing lens 12 that condenses laser light supplied from the laser light source through the window member 15 of the vacuum chamber 1, xenon, and the like. This is a gas jet cluster type light source including a nozzle 14 for ejecting a target gas and a condensing mirror 13 having a spheroidal reflection surface. For example, the exposure light EL pulse-emitted from the laser plasma light source 10 at a frequency of several kHz is condensed on the second focal point of the condenser mirror 13. The output of the laser plasma light source 10 (irradiation energy per unit time of the exposure light EL) is controlled by the exposure amount control system 33 under the control of the main control system 31.

  The exposure light EL condensed at the second focal point becomes a substantially parallel light beam via a concave mirror (collimator optical system) 21 and is incident on a first fly-eye optical system 22 composed of a plurality of mirrors. The exposure light EL reflected by the system 22 enters a second fly's eye optical system 23 composed of a plurality of mirrors. The pair of fly-eye optical systems 22 and 23 constitutes an optical integrator. The shape and arrangement of the mirror elements of the fly-eye optical systems 22 and 23 are disclosed in, for example, US Pat. No. 6,452,661.

  In FIG. 1, the reflecting surface of each mirror element of the first fly-eye optical system 22 is substantially conjugate with the pattern surface of the reticle R, and is in the vicinity of the reflecting surface of the second fly-eye optical system 23 (near the exit surface of the optical integrator). ), A substantial surface light source (a set of a large number of minute secondary light sources) having a predetermined shape is formed. That is, the surface on which the substantial surface light source is formed is the pupil plane of the illumination optical system ILS, and the illumination condition is set to normal illumination, annular illumination, dipole illumination, or An aperture stop 28 for switching to quadrupole illumination or the like is disposed.

  The exposure light EL that has passed through the aperture stop 28 enters the curved mirror 24, and the exposure light EL reflected by the curved mirror 24 is reflected by the concave mirror 25, and then is an arcuate illumination area on the pattern surface of the reticle R. 27R is illuminated in a superimposed manner with a uniform illuminance distribution obliquely from below. The curved mirror 24 and the concave mirror 25 constitute a condenser optical system. The illumination optical system ILS is configured including the concave mirror 21, the fly-eye optical systems 22 and 23, the aperture stop 28, the curved mirror 24, and the concave mirror 25. In this case, the exposure light EL from the laser plasma light source 10 Koehler illuminates the first fly's eye optical system 22 and thus the pattern surface of the reticle R. The illumination optical system ILS is not limited to the configuration shown in FIG. 1, and various other configurations are possible.

  Further, in order to define the arcuate illumination area 27R, the first Y-axis blind 26Y1 that shields the outside of the edge portion in the −Y direction of the exposure light EL, and the + Y of the exposure light EL reflected by the illumination area 27R A reticle blind including a second Y-axis blind 26Y2 that shields the outside of the direction edge portion, and first and second X-axis blinds (not shown) that define the position and width of the exposure light EL in the X direction. A variable field stop) is provided. The opening / closing operation of the reticle blind is controlled by a blind control system 34 under the control of the main control system 31.

  Next, the reticle R is attracted and held on the bottom surface of the reticle stage RST via the electrostatic chuck RH. The reticle stage RST is moved along a guide surface parallel to the XY plane of the outer surface of the vacuum chamber 1 by the stage control system 35 based on the measurement value of a laser interferometer (not shown) and the control information of the main control system 31. For example, it is driven with a predetermined stroke in the Y direction via a drive system (not shown) composed of a magnetically levitated two-dimensional linear actuator, and is also driven in a small amount in the X direction and the rotation direction around the Z axis (θz direction). The The reticle R is installed in a space surrounded by the vacuum chamber 1 through an opening on the upper surface of the vacuum chamber 1. A partition 8 is provided so as to cover the reticle stage RST on the vacuum chamber 1 side, and the inside of the partition 8 is maintained at an atmospheric pressure between the atmospheric pressure and the atmospheric pressure in the vacuum chamber 1 by a vacuum pump (not shown).

  The exposure light EL reflected by the illumination area 27R of the reticle R travels to the projection optical system PO that forms a reduced image of the pattern on the object plane (first surface) on the image plane (second surface). As an example, the projection optical system PO is configured by holding six mirrors M1 to M6 with a lens barrel (not shown), and is non-telecentric on the object plane (pattern surface of the reticle R) side and has an image plane (wafer W Is a telecentric reflecting optical system on the surface side, and the projection magnification is a reduction magnification such as 1/4. The exposure light EL reflected by the illumination area 27R of the reticle R is reduced to a part of the pattern of the reticle R on the exposure area 27W (area conjugate to the illumination area 27R) on the wafer W via the projection optical system PO. Form.

  In the projection optical system PO, the exposure light EL from the reticle R is reflected upward (+ Z direction) by the first mirror M1, subsequently reflected downward by the second mirror M2, and then the third mirror M3. And reflected downward by the fourth mirror M4. Next, the exposure light EL reflected upward by the fifth mirror M5 is reflected downward by the sixth mirror M6 to form a partial image of the pattern of the reticle R on the wafer W. As an example, the projection optical system PO is a coaxial optical system in which the optical axes of the mirrors M1 to M6 overlap the optical axis AX in common, and an aperture stop AS is disposed in the vicinity of the pupil surface near the reflection surface of the mirror M2 or in the vicinity thereof Has been. Further, between the mirror M6 and the wafer W, a pair of shielding plates 30Y1, 30Y2 in the Y direction and a pair of shielding plates in the X direction (not shown) for shielding flare generated by scattering in the projection optical system PO. ) Including a shielding mechanism. Note that the projection optical system PO does not have to be a coaxial optical system, and its configuration is arbitrary.

  Wafer W is attracted and held on wafer stage WST via electrostatic chuck WH. Wafer stage WST is arranged on a guide surface arranged along the XY plane. Wafer stage WST is driven by stage control system 35 via a drive system (not shown) composed of, for example, a magnetic levitation type two-dimensional linear actuator based on the measurement value of a laser interferometer (not shown) and control information of main control system 31. Then, it is driven with a predetermined stroke in the X direction and the Y direction, and is also driven in the θz direction or the like as necessary.

  In the vicinity of the wafer W on the wafer stage WST, an irradiation amount monitor 29 including a photoelectric sensor having sensitivity to EUV light such as a photodiode is installed, and a detection signal from the irradiation monitor 29 is supplied to the main control system 31. Has been. As an example, based on the measurement result of the irradiation monitor 29, the main control system 31 at the time of normal exposure causes the exposure amount control system so that the integrated exposure amount after scanning exposure falls within an allowable range at each point on the wafer W. The oscillation frequency and pulse energy of the laser plasma light source 10 are controlled via 33, and the scanning speed of the reticle stage RST (and wafer stage WST) is controlled via the stage control system 35. The main control system 31 is connected to a data processing system 36 for processing data relating to flare measurement.

At the time of exposure, the wafer W is arranged inside the partition 7 so that the gas generated from the resist on the wafer W does not adversely affect the mirrors M1 to M6 of the projection optical system PO. The partition 7 is formed with an opening through which the exposure light EL passes, and the space in the partition 7 is evacuated by a vacuum pump (not shown) under the control of the main control system 31.
At the time of exposure of the wafer W, the illumination optical system ILS illuminates the reticle R with an arcuate illumination area, and an image of the pattern in the illumination area 27R passes through the projection optical system PO into one shot area (die In the state exposed above, the reticle R and the wafer W move synchronously with respect to the projection optical system PO in the Y direction at a speed ratio according to the reduction magnification of the projection optical system PO. . In this way, the pattern image of the reticle R is exposed to the shot area on the wafer W. Thereafter, the wafer stage WST is driven to move the wafer W stepwise in the X and Y directions, and then the pattern image of the reticle R is scanned and exposed on the next shot area on the wafer W. In this way, a pattern image of the reticle R is sequentially exposed to a plurality of shot areas on the wafer W by the step-and-scan method.

  Next, the flare of the projection optical system PO of this embodiment will be described. Scattered light that is a factor of flare in the projection optical system PO is caused by the surface roughness of the mirrors M1 to M6. The flare is, for example, several in the exposure area 27W on the image plane of the projection optical system PO. There are short-distance flare that spreads in the range from about μm to about 1 mm, and long-distance flare that spreads over a distance of, for example, about 1 mm or more on the image plane. In the present embodiment, shielding plates 30Y1, 30Y2, etc. are installed between the projection optical system PO and the wafer W in FIG. Therefore, among the scattered light (flares) generated at the ends of the mirror M6 closest to the wafer W of the projection optical system PO in the + Y direction and the −Y direction, the scattered light contacting the edge portions of the shielding plates 30Y1 and 30Y2 in the Y direction. Only scattered light inside ELa and ELb reaches the wafer W. Similarly, of the scattered light (flare) generated at the ends in the ± X direction of the mirror M6, only the scattered light inside the scattered light contacting the edge portion of the shielding plate (not shown) in the X direction is on the wafer W. To reach. Therefore, when an image of an edge of the shielding plates 30Y1, 30Y2, etc. by the scattered light ELa, ELb in the Y direction and scattered light (not shown) in the X direction is an image 30P, the image 30P is an area surrounding the exposure area 27W. Long-distance flare generated in the projection optical system PO does not spread outside the image 30P of the edge portion of the shielding plate.

  Therefore, in this embodiment, a flare including a long-distance flare that spreads outside the exposure area 27W on the wafer W and inside the image 30P of the edge portion of the shielding plate is set as a measurement target. At the time of the flare measurement, the first test reticle R1 in FIG. 2A or the second test reticle R2 in FIG. 2C is loaded on the reticle stage RST in FIG. 1 instead of the reticle R. 2A and 2B is a coordinate system on the bottom surface of reticle stage RST in FIG.

  As shown in the bottom view of FIG. 2A, a line and space pattern (with a period Pr in the X direction) is formed on the entire pattern area of the test reticle R1 (area corresponding to one shot area on the wafer). Hereinafter, it is referred to as an L & S pattern.) 2 is formed. The L & S pattern 2 is surrounded by an absorption layer PAB (dark part) of exposure light. As shown in the enlarged view of FIG. 2B, the L & S pattern 2 has a line portion 2A made of a reflective film extending in the Y direction with an X direction width of Pr / 2, and an X direction width of Pr / 2. A space portion 2B made of an absorption layer extending in the Y direction is arranged with a period Pr in the X direction. As an example, the width Pr / 2 of the line portion 2A and the space portion 2B is about 50 to 60 nm at the stage of the image by the projection optical system PO. In FIG. 2A, FIG. 4A described later, and the like, the period of the L & S pattern 2 and its image is drawn considerably larger than the actual one for easy understanding.

  Further, as shown in the bottom view of FIG. 2C, a rectangular region elongated in the X direction, for example, surrounded by the absorption layer PAB at the center of the pattern region of the test reticle R2 is a reflective pattern 4 made of a reflective film. . The reflection pattern 4 is a region wider than the illumination region 27R by the exposure light EL in the X direction and the Y direction, and the reflection pattern 4 is set so as to cover the illumination region 27R during flare measurement. As an example, the width of the exposure region 27W on the wafer conjugate with the illumination region 27R in the Y direction (scanning direction) is about several mm, and the length in the X direction is about 20 to 30 mm. The shape of the reflection pattern 4 may be any shape as long as it is wider than the illumination region 27R. The entire pattern region of the test reticle R2 may be used as a reflection film, and the entire surface may be used as the reflection pattern 4. Good.

  Next, an example of an operation for evaluating the flare of the projection optical system PO of the exposure apparatus 100 using the test reticles R1 and R2 will be described with reference to the flowchart of FIG. The operation on the exposure apparatus 100 side at this time is controlled by the main control system 31. First, in step 101 of FIG. 3, the first test reticle R1 of FIG. 2A is loaded on the reticle stage RST of FIG. 1, and the alignment of the test reticle R1 is performed using the alignment mark (not shown) of the test reticle R1. Is done. In the next step 102, an unexposed wafer (referred to as W1) coated with a positive resist is loaded on wafer stage WST. In the next step 103, the main control system 31 sets the exposure amount for the wafer when an image having the same duty ratio (ratio between the width of the line portion and the width of the space portion) as the L & S pattern 2 of the test reticle R1 is exposed. The exposure amount (predetermined value) EP slightly lower than the exposure amount (resist sensitivity) is set to EP, and the value of the control parameter i is set to 1.

  In the next step 104, the exposure apparatus 100 applies an image 2P of the L & S pattern 2 of the test reticle R1 to the entire surface of the first shot area (reference shot) 38A on the wafer W1 in FIG. Then, exposure is performed with the set exposure amount EP. The image 2P is obtained by arranging the image 2AP of the line portion 2A (bright portion) and the image 2BP of the space portion 2B (dark portion) in the X direction with a period Pr · β (β is the projection magnification of the projection optical system PO). . However, for convenience of explanation, it is assumed that an erect image in the X and Y directions of the pattern of the test reticle R1 is formed on the wafer W1. 2A is a bottom view of the test reticle R1, and FIG. 4A is a plan view of the wafer W1, both of which are inverted in the X direction. The same applies to the test reticle R2.

  In the next step 105, it is determined whether or not the set exposure amount has reached a predetermined upper limit value (a value higher than the level obtained by adding the expected maximum exposure amount of the long distance flare to the exposure amount EP). At this stage, since the exposure amount has not reached the upper limit, the operation shifts to step 106, and the main control system 31 increases the exposure amount EPi of the wafer by a predetermined amount ΔEP based on the following equation. The predetermined amount ΔEP is set according to the flare measurement accuracy.

EPi = EP + i · ΔEP (1)
Thereafter, 1 is added to the value of the parameter i in step 107, and the process returns to step 104. The test reticle is set to the i-th (here, i = 2) shot region 38B on the wafer W with the set exposure amount EP1. The image 2P of the L & S pattern 2 of R1 is exposed. Information on the set exposure amount EPi on the wafer W and the order (position) of the corresponding shot areas is stored in the data processing system 36. Thereafter, until the set exposure amount EPi exceeds the upper limit value, the exposure amounts EP2 that gradually increase in the shot areas 38C and 38D and other shot areas (not shown) on the wafer W in FIG. , EP3,..., The image 2P of the L & S pattern 2 of the test reticle R1 is exposed. When the number of shot areas to be exposed is not enough for one wafer, the image of the L & S pattern 2 on the test reticle R1 is exposed to a large number of shot areas on a plurality of wafers with a gradually increasing exposure amount. May be.

  Thereafter, when the set exposure amount EPi exceeds the upper limit value, the operation proceeds from step 105 to step 108, and the wafer W1 is unloaded from the exposure apparatus 100 and transferred to a coater / developer (not shown). The coater / developer develops the resist on the wafer W1. In each of the shot areas 38A to 38D on the wafer W1 after development, a resist pattern 2R corresponding to the image 2P of the L & S pattern 2 is formed as shown in FIG. The resist pattern 2R corresponds to a plurality of line patterns 2AR composed of concave portions (dissolving portions) corresponding to the image 2A of the line portion and an image 2BP of the space portion as shown in the enlarged view of the B1 portion in FIG. And a plurality of space patterns 2BR made of convex portions (remaining portions).

  In the next step 109, the developed wafer W1 is set on a scanning electron microscope (SEM) (not shown), and the first shot area 38A (exposure is exposed and developed on the wafer W1 in FIG. 4B). A plurality of square measurement areas MTij (i) with a period SX and SY (= SY) in the X direction and Y direction, a width ΔX in the X direction and a width ΔY (= ΔX) in the Y direction = 1,..., I; j = 1,. As an example, the width ΔX (ΔY) of the measurement region MTij is about 5 μm, and the period SX (SY) of the arrangement of the measurement regions MTij is about 200 μm. In this case, the measurement region MTij in the shot region 38 in the X direction The number I is about 100 to 150, and the number J in the Y direction is about 150 to 200. Then, the line width dxij in the X direction of the line pattern 2AR in the resist pattern 2R is measured by SEM at a plurality of positions in each measurement area MTij of the shot area 38A, as shown by the enlarged B1 portion. An average value (also referred to as dxij) is obtained. Instead of measuring the line width of the line pattern 2AR, the line width of the space pattern 2BR may be measured as described later.

  Information on the average line width dxij of the line pattern 2AR in the multiple measurement areas MTij in the shot area 38A is supplied to the data processing system 36. In the data processing system 36, a reference CD (critical dimension) map is created, which is a table in which information of the average line width dxij of each measurement area MTij in the shot area 38A is associated with the exposure amount EP. The CD map is stored in the storage unit. Further, for the other shot regions 38B to 38D on the wafer W1 in FIG. 4B, the average line width dxij of the line pattern 2AR in each of the many measurement regions MTij inside is measured by the SEM, and the measurement result is It is supplied to the data processing system 36. In the data processing system 36, the difference Δdxij from the average line width dxij of the measurement area MTij in the corresponding shot area 38A of the average line width dxij of each measurement area MTij such as the shot areas 38B to 38D is obtained, and each measurement area MTij is obtained. A CD map in which the difference Δdxij and the exposure amount difference δEPi (= EPi−EP) are arranged in correspondence with each other is created, and this CD map is also stored in the storage unit.

  In this case, since the exposure amount EPi (difference in exposure amount) is larger in the shot area to be exposed later, the average line width dxij (difference Δdxij) gradually increases. For example, the average line width dxij in the measurement area MTij of the fourth shot area 38D is larger than the average line width dxij in the shot area 38A, as shown in the B2 portion of the enlarged view. Therefore, the difference in exposure amount corresponding to the difference Δdxij in the resist pattern average line width of each measurement region MTij in each shot region on the wafer W1, and thus the exposure amount EPi can be obtained.

The process including the measurement in the SEM in step 109 may be executed immediately before step 118, which is a process including the measurement in the SEM described later.
In the next step 111, the first test reticle R1 shown in FIG. 2A is loaded onto the reticle stage RST shown in FIG. Note that when the process proceeds to step 111 following step 108 (or step 109) as in the present embodiment, the test reticle R1 is already loaded on the reticle stage RST, and therefore step 111 can be omitted. . In the next step 112, an unexposed wafer (referred to as W2) coated with a positive resist is loaded on wafer stage WST. In the next step 113, the exposure apparatus 100 scans the entire surface of one shot area 38 on the wafer W1 in FIG. 5A by scanning exposure, and the image 2P of the L & S pattern 2 of the test reticle R1 is converted into a reference CD map. Exposure is performed with the exposure amount EP as created. The periphery of the shot area 38 is a non-exposed portion 40A that is not irradiated with exposure light.

  In the next step 114, the test reticle R1 is unloaded from the reticle stage RST, the second test reticle R2 in FIG. 2C is loaded onto the reticle stage RST, and an alignment mark (not shown) of the test reticle R2 is loaded. The alignment is performed using. In the next step 115, wafer stage WST is driven in the X direction (non-scanning direction), and as shown in FIG. 5B, shot area 38 on wafer W2 is shot with respect to position B3 so far. The region 38 moves in the + X direction by HX / 2 which is ½ of the width in the X direction. In the next step 116, the image of the reflection pattern 4 of the test reticle R2 (in this case, the image 27RP of the illumination area 27R itself) is superimposed on the area including the shot area 38 on the wafer W2 at a predetermined exposure amount in a stationary state. To expose. In this case, the image 27RP of the illumination area 27R is obtained by irradiating the entire exposure area 27W with the exposure light EL with a uniform light amount distribution, and the area other than the exposure area 27W is the non-exposed portion 40B. However, flare from the projection optical system PO is also irradiated to the non-exposure portion 40B.

As a result of this exposure, an image 2P of the L & S pattern 2 of the test reticle R1 and an image of the reflection pattern 4 of the test reticle R2 (in the illumination area 27R) are formed in the shot area 38 on the wafer W2, as shown in FIG. The image 27RP or the exposure region 27W) is laterally shifted in the X direction and double-exposed.
In the subsequent step 117, the wafer W2 is unloaded from the exposure apparatus 100 and transferred to a coater / developer (not shown), and the resist on the wafer W2 is developed by the coater / developer. In the shot area 38 on the wafer W2 after development, as shown in FIG. 6, a resist pattern 2R corresponding to the image 2P of the L & S pattern 2 and a resist pattern 27RR (or exposure area) corresponding to the image 27RP of the illumination area 27R And a resist pattern 27WR) corresponding to 27W. Further, since the long distance flare from the projection optical system PO is irradiated around the resist pattern 27RR and inside the edge image 30P such as the shielding plates 30Y1 and 30Y2 in FIG. 1, the resist pattern 27RR The line width of the line pattern 2AR is thicker as the position is closer to the resist pattern 27RR. From this difference in line width, a long-distance flare that is an increased amount of exposure can be obtained.

  Therefore, in the next step 118, the developed wafer W2 is set in a scanning electron microscope (SEM) (not shown), and in the shot region 38 of the wafer W2 in FIG. 6, the center 43 of the resist pattern 27RR is used as a reference. A number of evaluation points Fm (m = 1, 2, 3,...) Having a distance Xm in the X direction and a distance Ym in the ± Y direction are set, and the line width dxm of the line pattern 2AR is measured at these evaluation points Fm. In this case, the line width dxk of the line pattern 2AR is measured also at a plurality of evaluation points Fk outside the X direction with respect to the resist pattern 27RR and inside the image 30P. That is, a large number of measurement points Fm are set equally between the resist pattern 27RR and the image 30P in the X and Y directions with a predetermined period (for example, the same as the measurement period SX in FIG. 4B). Information on the position of each evaluation point Fm and the measurement result of the line width dxm is supplied to the data processing system 36.

  In the next step 119, the data processing system 36 measures the closest line width dxm of the line pattern 2AR measured at each evaluation point Fm in the shot area 38 of FIG. 6 in the reference CD map stored in step 109. A difference Δdxm with respect to the average line width dxij of the region MTij (or an interpolation value from a value in the vicinity thereof) is obtained. Thereafter, the difference Δdxm is compared with the CD map stored in step 109 to obtain an exposure amount difference δEPm corresponding to the difference Δdmx (difference from the exposure amount EP at the time of creating the reference CD map). This difference δEPm is the exposure amount of the flare at the evaluation point Fm, and the data processing system 36 uses the exposure amount δEPm and the exposure amount EPF when the image of the illumination area 27R in FIG. Thus, the flare at the evaluation point Fm is calculated.

Flare = (δEPm / EPF) × 100 (%) (2)
Further, by obtaining the flare of each evaluation point Fm, it is possible to obtain the distribution of flare (long distance flare) spreading outside the exposure region 27W. The measurement result of the flare distribution is supplied to the main control system 31. In the next step 120, the main control system 31 adjusts the positions of the shielding plates 30Y1, 30Y2, etc. according to the distribution of the long distance flare as an example. That is, if there are many long-distance flares, the adjacent shot area is slightly exposed during the scanning exposure of a shot area on the wafer W. Therefore, in order to reduce such unnecessary exposure, a shielding plate in the X direction (not shown) You may narrow the space | interval of illustration. Thereby, the measurement of the long distance flare of the projection optical system PO is completed.

In this way, by double-exposing the image of the L & S pattern 2 and the image of the reflection pattern 4 (illumination area 27R) on the wafer and measuring the line width of the resist pattern corresponding to the image of the L & S pattern 2, Long distance flare and the like of the projection optical system PO can be accurately measured.
Effects and the like of this embodiment are as follows.
(1) The flare measurement method of the projection optical system PO of the exposure apparatus 100 according to the present embodiment is such that the image 2P of the L & S pattern 2 of the test reticle R1 is exposed to the resist-coated wafer W2 via the projection optical system PO. Step 113 and the image of the reflection pattern 4 (illumination area 27R) of the test reticle R2 different from the L & S pattern 2 are exposed through the projection optical system PO while partially overlapping the image 2P on the wafer W2. Step 116, Step 118 for measuring the line width of the line pattern 2AR at the plurality of evaluation points Fm of the resist pattern 2R corresponding to the image 2P on the wafer W2, and the flare of the projection optical system PO from the measurement result of the line width. Determining step 119.

According to this flare measurement method, an image of the reflection pattern 4 (illumination area 27R) is exposed on a part of the image 2P of the L & S pattern 2 on the wafer W2, and a long-distance flare is present in the image 2P outside the image. Is irradiated, and the line width of the image of the line portion of the image 2P changes. Therefore, the long distance flare can be evaluated from the change in the line width.
In the image 2P of the L & S pattern 2, the sum of the line width of the image of the line portion 2A and the line width of the image of the space portion 2B is constant (the period of the image 2P). Instead of measuring the line width of the image (line pattern 2AR), the line width of the image of the space 2B may be measured, and the flare may be obtained from this measurement result.

  In the present embodiment, the image of the L & S pattern 2 of the test reticle R1 is first exposed on the wafer W2, and then the image of the reflection pattern 4 of the test reticle R2 is superimposed thereon and exposed. However, the image of the reflection pattern 4 (illumination region 27R) of the test reticle R2 is first exposed on the wafer W2, and then the L & S pattern 2 image of the test reticle R1 is overlaid and exposed so as to cover the image. May be. Even in this case, the flare of the projection optical system PO can be measured similarly.

The test reticles R1 and R2 are not necessarily separated from each other, and the reflection pattern 4 of the test reticle R2 may be formed in a part of the pattern area of the test reticle R1.
(2) In the present embodiment, the steps 102 to 107 for exposing the image 2P of the L & S pattern 2 of the test reticle R1 onto the wafer W1 coated with the resist, and the line portion of the image 2P exposed to the wafer W1. In step 110, the line width of the image of the line portion of the image 2P measured on the wafer W2 and the line portion of the image 2P measured on the wafer W1 are measured. Flare is calculated by comparison with the line width. Therefore, the flare can be obtained only from the measurement result of the line width.

When measuring the line width of the space portion of the image of the L & S pattern 2 in step 118, the line width of the image of the space portion of the image of the L & S pattern 2 may also be measured in step 109.
(3) In this case, in steps 104 to 107, the image 2P of the L & S pattern 2 is exposed to different shot areas 38A to 38D on the wafer W1 while changing the exposure amount. In step 109, the image of the L & S pattern 2 is measured. The reference CD map and the CD map are created by associating the line width and the exposure amount, and in step 119, the flare at the position where the line width is measured using the measured line width and those CD maps. The amount of exposure is obtained. Therefore, by creating the reference CD map and the CD map in advance, the flare of the projection optical system PO can be efficiently measured using the CD map thereafter.

Therefore, the operations from Step 101 to Step 109 in FIG. 3 do not need to be performed every time the flare measurement of the projection optical system PO is performed, for example, once after the start of the operation of the exposure apparatus or periodically. It may be only.
(4) Further, the reflection pattern 4 of the test reticle R2 is wider than the illumination area 27R. By using the reflection pattern 4, in step 116, exposure is performed on the entire surface of the exposure area 27W of the exposure light EL on the wafer W2. It has been broken. That is, by using the reflection pattern 4, the shape of the entire illumination region 27R or the shape of the entire exposure region 27W is defined as the irradiation region. Therefore, it is possible to measure the long distance flare that goes outside the exposure area 27W.

Note that the reflection pattern 4 of the test reticle R2 may be the same shape as the illumination region 27R or a smaller pattern. In this case, the flare that goes out of the rectangular pattern image can be measured by the double exposure.
Further, in the present embodiment, the shape of the illumination area 27R has been described by taking an arc shape as an example, but may be a rectangular shape.
(5) In this embodiment, the periodic direction of the L & S pattern 2 of the test reticle R1 is the X direction (non-scanning direction), but the periodic direction may be the Y direction (scanning direction). Furthermore, the duty ratio of the L & S pattern 2 (the ratio of the width between the line portion and the space portion) may not be 1: 1.

The test reticle R1 is formed with the L & S pattern 2 having a uniform period. For example, the test reticle R1 is formed with an L & S pattern having a gradually changing period or a large number of independent small L & S patterns. May be. Even in this case, flare can be measured by measuring the change in the line width of the image of the line portion or space portion after double exposure.
(6) In this embodiment, the wafer W2 is moved in the + X direction by a distance that is ½ of the width of the shot region 38 in Step 115 between Step 113 and Step 116. In Step 118, the illumination region 27R is moved. The line width of the line pattern 2AR is also measured at the evaluation point Fk on the X direction side with respect to the resist pattern 27RR corresponding to the image. Accordingly, it is possible to measure the range and amount of flare spreading in the non-scanning direction with respect to the exposure region 27W.

In step 115, the wafer W2 may be moved in the −X direction. Thereby, a flare spreading in the −X direction from the exposure region 27W can be measured. Further, the movement amount of the wafer W2 in the X direction may not be ½ of the width of the shot region 38 in the X direction.
Further, step 115 may be omitted, and the image of the illumination area 27R may be exposed at the center of the image of the L & S pattern 2. In this case, the flare spreading in the + Y direction and the −Y direction from the exposure region 27W can be measured.

(7) In this embodiment, the measurement of the line width of the image line portion of the image of the L & S pattern 2 on the wafers W1 and W2 is performed on the resist pattern formed after development of the resist on the wafers W1 and W2. Is going. The line width can be measured with high accuracy using a scanning electron microscope or the like.
Note that the measurement of the line width of the line portion (or space portion) of the image of the L & S pattern 2 on the wafers W1 and W2 may be performed at the stage of the latent image of the resist layer.

(8) In the above embodiment, since the EUV exposure apparatus is used, the test reticles R1 and R2 are of a reflective type, and the pattern is formed of a reflective film and an absorbing film for EUV light.
When the test reticles R1 and R2 are used as a transmissive reticle of an exposure apparatus that uses exposure light having a wavelength of 193 nm, for example, the test reticle includes, as an example, a substrate that transmits exposure light, and the surface of the substrate. The pattern corresponding to the L & S pattern 2 or the reflection pattern 4 is formed as a periodic transmission pattern or a transmission pattern having a predetermined shape from which a part of the light shielding film is removed.

  (9) Further, the exposure method of the present embodiment is an exposure method in which the pattern of the reticle R is illuminated with the exposure light EL, and the wafer W is exposed with the exposure light EL through the pattern and the projection optical system PO. Steps 101 to 119 of measuring the flare information of the projection optical system PO by the flare measurement method of the embodiment and a step 120 of adjusting the positions of the shielding plates 30Y1, 30Y2, etc. based on the measurement result of the flare information are included. . Therefore, even if the flare of the projection optical system PO exists, the target pattern can be formed on the wafer W while suppressing the influence.

Instead of adjusting the positions of the shielding plates 30Y1, 30Y2, etc., the size of the openings formed by the shielding plates 30Y1, 30Y2 may be changed.
Moreover, although the structure provided with the shielding mechanism containing the shielding plates 30Y1 and 30Y2 in the Y direction and the shielding plate in the X direction has been described, this shielding mechanism can be omitted.
By doing so, it becomes possible to measure a wide range of flares that are not blocked by the shielding plates 30Y1 and 30Y2 and the shielding plate in the X direction.
Further, instead of adjusting the positions of the shielding plates 30Y1, 30Y2, etc., or together therewith, a desired pattern is formed on the wafer W by reducing the influence of the flare according to the measurement result of the flare of the projection optical system PO. The shape such as the line width of the pattern formed on the reticle R may be corrected so as to be formed. That is, the reticle design may be changed in consideration of the optical proximity effect.

In the embodiment of FIG. 1, the case where the EUV light is used as the exposure beam and the all reflection projection optical system including only six mirrors is used is described as an example. For example, in addition to an exposure apparatus having a projection optical system composed of only four mirrors or the like, a VUV light source having a wavelength of 100 to 160 nm, for example, an Ar ₂ laser (wavelength 126 nm) is used as a light source, and four to eight mirrors or the like are used. The present invention can also be applied to an exposure apparatus equipped with a projection optical system.

Furthermore, the present invention can also be applied to a case where a projection optical system composed of a refractive system using ArF excimer laser light (wavelength 193 nm) or the like as exposure light is used.
When an electronic device (or microdevice) such as a semiconductor device is manufactured using the exposure method or exposure apparatus of the above embodiment, the electronic device has a function / performance design of the electronic device as shown in FIG. Step 221 to perform, Step 222 to manufacture a mask (reticle) based on this design step, Step 223 to manufacture a substrate (wafer) that is a base material of the device and apply a resist, Reticle by the exposure apparatus of the above-described embodiment A substrate processing step 224 including a step of exposing the pattern of the substrate (sensitive substrate), a step of developing the exposed substrate, a heating (curing) and etching step of the developed substrate, a device assembly step (dicing step, bonding step, 225) as well as inspection steps It is produced through the flop 226 and the like.
Therefore, in this device manufacturing method, a pattern of the photosensitive layer is formed on the substrate using the exposure method or exposure apparatus of the above embodiment, and the substrate on which the pattern is formed is processed (step 224). Is included. According to the exposure method or the exposure apparatus, since the influence of flare of the projection optical system can be reduced, an electronic device can be manufactured with high accuracy.

In addition, the present invention is not limited to application to a semiconductor device manufacturing process. For example, a manufacturing process of a display device such as a liquid crystal display element or a plasma display formed on a square glass plate, or an imaging element (CCD, etc.), micromachines, MEMS (Microelectromechanical Systems), thin film magnetic heads, various devices such as DNA chips, and masks themselves can be widely applied to the manufacturing process.
In addition, this invention is not limited to the above-mentioned embodiment, A various structure can be taken in the range which does not deviate from the summary of this invention.

  ILS ... illumination optical system, R ... reticle, R1, R2 ... test reticle, PO ... projection optical system, W ... wafer, M1-M6 ... mirror, 2 ... L & S pattern, 2P ... L & S pattern image, 2R ... resist pattern, 4 ... reflection pattern, 27R ... illumination area, 27W ... exposure area, 30Y1, 30Y2 ... shielding plate

Claims (8)

In a method for measuring flare information of a projection optical system,
One of the first pattern image in which the line portions and the space portions are periodically formed or the second pattern image having a shape different from the first pattern is transferred to the first photosensitive substrate via the projection optical system. Exposing to
The other of the image of the first pattern or the image of the second pattern is transferred to the image of the first pattern or the image of the second pattern exposed on the first photosensitive substrate via the projection optical system. A process of overlaying and exposing on one side;
Measuring a line width of the image of the line part or the space part at a plurality of positions of the image of the first pattern on the first photosensitive substrate;
Exposing an image of the first pattern onto a second photosensitive substrate;
Measuring the line width of the image of the line portion or the space portion of the image of the first pattern exposed on the second photosensitive substrate;
See containing and a step of obtaining the flare information from the measurement result of the line width,
The step of exposing the image of the first pattern on the second photosensitive substrate includes exposing the image of the first pattern to a different position on the second photosensitive substrate while changing an exposure amount,
The step of measuring the line width of the image of the line portion or the space portion exposed on the second photosensitive substrate includes a step of obtaining a relationship between the line width and an exposure amount,
The step of obtaining the flare information includes exposing the first photosensitive substrate at the plurality of positions based on the line width measured on the first photosensitive substrate and the relationship between the line width and the exposure amount. look including the step of determining the amount, by comparison with the second line width measured measured line width of a photosensitive substrate and in said first photosensitive substrate, and obtaining the flare information Flare measurement method. The second pattern has a shape that defines an irradiation area of illumination light irradiated on an object plane of the projection optical system or an image plane of the projection optical system,
The flare measurement method according to claim 1, wherein the step of obtaining the flare information obtains flare information outside the irradiation area. The step of exposing the image of the first pattern to the first photosensitive substrate moves the first pattern and the first photosensitive substrate in a scanning direction with respect to the projection optical system, and Scanning and exposing the first photosensitive substrate with an image of one pattern;
The step of exposing the image of the second pattern to the first photosensitive substrate includes stationary the second pattern and the first photosensitive substrate, and the first photosensitive substrate using the image of the second pattern. flare measuring method according to claim 1 or claim 2, wherein exposing the sexual substrate. In a method for measuring flare information of a projection optical system,
One of the first pattern image in which the line portions and the space portions are periodically formed or the second pattern image having a shape different from the first pattern is transferred to the first photosensitive substrate via the projection optical system. Exposing to
The other of the image of the first pattern or the image of the second pattern is transferred to the image of the first pattern or the image of the second pattern exposed on the first photosensitive substrate via the projection optical system. A process of overlaying and exposing on one side;
Measuring a line width of the image of the line part or the space part at a plurality of positions of the image of the first pattern on the first photosensitive substrate;
See containing and a step of obtaining the flare information from the measurement result of the line width,
The step of exposing the image of the first pattern to the first photosensitive substrate moves the first pattern and the first photosensitive substrate in a scanning direction with respect to the projection optical system, and Scanning and exposing the first photosensitive substrate with an image of one pattern;
The step of exposing the image of the second pattern to the first photosensitive substrate includes stationary the second pattern and the first photosensitive substrate, and the first photosensitive substrate using the image of the second pattern. A flare measurement method comprising exposing a conductive substrate. Between the step of exposing the image of the first pattern to the first photosensitive substrate and the step of exposing the image of the second pattern to the first photosensitive substrate, the first photosensitive substrate. Moving in a direction perpendicular to the scanning direction with respect to the projection optical system,
At least one of the plurality of positions at which the line width of the line portion or the space portion exposed on the first photosensitive substrate is measured is orthogonal to the scanning direction with respect to the image of the second pattern. The flare measurement method according to claim 3 or 4 , wherein the flare measurement method is located outside the direction in which the flare occurs. The step of measuring the line width of the image of the line portion or the space portion exposed on the first photosensitive substrate includes the step of developing the first photosensitive substrate, and the first photosensitive property after development. flare measuring method according to any one of claims 1 to 5, characterized in that it comprises a step of measuring the line width of the light-sensitive pattern formed on the substrate. The flare measurement method according to any one of claims 1 to 6 , wherein the projection optical system is a reflection system using EUV light as illumination light. In an exposure method for forming a pattern on an object via a projection optical system,
Measure flare information of the projection optical system using the flare measurement method according to any one of claims 1 to 7,
An exposure method that performs processing according to the measurement result of the flare information.

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