JP2010114168A - Method and device for evaluating projected image, method and device for exposure, and method for managing the device for exposure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To efficiently evaluate the state of cross-sectional shape, etc., in an image which is to be formed in the photosensitive layer of a substrate, without having actually to expose the substrate. <P>SOLUTION: A device for exposure having a projected image evaluating device for evaluating the cross-sectional shape of the image to be formed in the photosensitive layer on a wafer W after development includes: a first operation part 22a for obtaining the contrast information of an intensity distribution of illumination light, in a direction along the front surface of the photosensitive layer; a second operation part 22b for obtaining standing wave information in the photosensitive layer, based on the reflectance of the front end in the photosensitive layer on the wafer W; and a third operation part 22c for obtaining the linewidth information of the image to be formed in the photosensitive layer after development, through the use of the contrast information to be obtained by the first operation part 22a and the standing wave information which is to be obtained by the second operation part 22b. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a projection image evaluation technique for evaluating the state of an image formed on a photosensitive layer on a substrate by exposure and development, as well as an exposure technique using this projection image evaluation technique and an exposure apparatus management technique. Furthermore, the present invention relates to a device manufacturing technique using the projection image evaluation technique.

  A wafer (or glass plate) coated with a resist as a substrate to be exposed in a reticle (or photomask) pattern in a lithography process for manufacturing a device such as a semiconductor element or a liquid crystal display element (electronic device or microdevice) For example, an exposure apparatus such as a batch exposure type projection exposure apparatus such as a stepper or a scanning exposure type projection exposure apparatus such as a scanning stepper is used. In this type of exposure apparatus, in order to transfer various patterns onto a wafer with high resolution while ensuring a sufficient depth of focus, exposure conditions such as illumination conditions are set according to the pattern to be transferred. .

After exposure is performed under the exposure conditions set in this way, a resist pattern is formed on the resist layer of the wafer by developing the wafer, and pattern formation processing such as etching is performed using this resist pattern. Applied. Therefore, in order to evaluate whether or not the formed resist pattern has a target shape, conventionally, for example, the line width when the resist pattern is viewed from the upper surface is measured by, for example, a scanning electron microscope (SEM). (For example, refer to Patent Document 1).
JP 2006-126532 A

In the conventional evaluation method in which the line width of a resist pattern is actually measured by a scanning electron microscope as in the past, if the resist pattern has a defect or the like, the exposure condition is set using another unexposed wafer. It is necessary to change and repeat exposure and development. Therefore, for example, there is a problem that it takes a long time to determine the optimum exposure conditions.
Furthermore, since the lower ground of the resist layer of the wafer reflects the illumination light for exposure with a reflectance of, for example, several percent, a standing wave formed by the illumination light incident on the resist layer and the reflected light from the base surface Thus, the light intensity distribution in the resist layer also has periodic fluctuations in the thickness direction. As a result, since the resist pattern after development includes a thick part and a thin part in the thickness direction, even if the line width of the thick part exceeds the allowable range, a post process is performed in the thin part. There is a possibility that the resist pattern collapses or the like (for example, a drying step during the development step).

In addition, in order to measure the change in the line width in the thickness direction of the resist pattern or the cross-sectional shape with a scanning electron microscope, it is necessary to perform a destructive inspection of the wafer, and a longer time is required for evaluation. In addition, there is a problem that the wafer after inspection cannot be reused.
In view of the above, the present invention provides a projection image evaluation technique capable of efficiently evaluating the state of a cross-sectional shape and the like of an image formed on a photosensitive layer of a substrate such as a resist pattern, and an exposure technique using this projection image evaluation technique. And an exposure apparatus management technique.

  It is another object of the present invention to provide a device manufacturing technique that can efficiently manufacture a device using the exposure technique.

  The projection image evaluation method according to the present invention is a projection image evaluation method for evaluating the cross-sectional shape of an image formed on a photosensitive layer on a substrate after development, and the exposure light of the exposure layer when exposing the photosensitive layer Determine the contrast information of the intensity distribution in the direction along the surface, determine the standing wave information in the photosensitive layer from the reflectance of the substrate, and develop the photosensitive layer based on the contrast information and the standing wave information The line width information of an image to be formed later is obtained.

  An exposure method according to the present invention is set using an exposure method for exposing a photosensitive layer on a substrate with exposure light, the step of setting exposure conditions for the photosensitive layer, and the projected image evaluation method of the present invention. A step of obtaining line width information of an image formed after development on the photosensitive layer under the exposure conditions, and a step of changing the set exposure conditions based on the obtained line width information. .

  An exposure apparatus management method according to the present invention is an exposure apparatus management method for exposing a photosensitive layer on a substrate with exposure light, wherein exposure conditions for the photosensitive layer are set in the exposure apparatus, and the projection according to the present invention is performed. Using the image evaluation method, the line width information of the image formed on the photosensitive layer after development is obtained under the set exposure conditions, and the exposure result by the exposure apparatus based on the obtained line width information Is to evaluate.

  A projection image evaluation apparatus according to the present invention is a projection image evaluation apparatus that evaluates a cross-sectional shape of an image formed on a photosensitive layer on a substrate after development, and that exposure light when exposing the photosensitive layer is sensitive to the projection image evaluation apparatus. A first calculation unit that obtains contrast information of intensity distribution in the direction along the surface of the layer, a second calculation unit that obtains standing wave information in the photosensitive layer from the reflectance of the substrate, and a first calculation unit. And a third calculation unit for obtaining line width information of an image formed on the photosensitive layer after development using the contrast information obtained and the standing wave information obtained by the second calculation unit. .

An exposure apparatus according to the present invention is an exposure apparatus that exposes a photosensitive layer on a substrate with exposure light, the projection image evaluation apparatus of the present invention, a setting unit that sets exposure conditions for the photosensitive layer, and the setting thereof And a controller that changes the set exposure condition based on the line width information of the image formed on the photosensitive layer after development, which is obtained by the projection image evaluation apparatus under the exposure condition. .
The device manufacturing method according to the present invention includes exposing the photosensitive layer on the substrate using the exposure method or exposure apparatus of the present invention and developing the exposed photosensitive layer.

  According to the present invention, for example, the intensity distribution (contrast information) of exposure light in the direction along the surface of the photosensitive layer on the substrate is used to determine the intensity distribution of the standing wave in the photosensitive layer obtained from the reflectance of the substrate ( By adding the standing wave information), a two-dimensional light intensity distribution in the photosensitive layer is obtained. Then, line width information of an image formed on the photosensitive layer after development can be obtained from the light intensity distribution and sensitivity information of the photosensitive layer. Therefore, it is possible to efficiently evaluate the state such as the cross-sectional shape of an image (for example, a resist pattern) formed on the photosensitive layer of the substrate without actually exposing the substrate.

Hereinafter, an example of a preferred embodiment of the present invention will be described with reference to FIGS.
FIG. 1 shows the configuration of a scanning exposure type exposure apparatus (projection exposure apparatus) 100 comprising a scanning stepper according to this embodiment. In FIG. 1, an exposure apparatus 100 includes an exposure light source 1, an illumination optical system ILS that illuminates a reticle R (mask) on which a transfer pattern is formed with illumination light IL (exposure light) from the light source 1, and Reticle stage RST that controls the position and speed of reticle R, projection optical system PL that projects an image of the pattern of reticle R onto wafer W (substrate) coated with a resist (photosensitive material), the position of wafer W, and It includes a wafer stage WST that controls the speed and a main control system 20 that includes a computer that controls the overall operation of the apparatus. 1, the Z axis is taken in parallel to the optical axis AX of the projection optical system PL, the X axis is parallel to the paper surface of FIG. 1 in the plane perpendicular to the Z axis, and the Y axis is perpendicular to the paper surface of FIG. Take and explain. The scanning direction of reticle R and wafer W during exposure is a direction parallel to the Y axis (Y direction).

As the light source 1, an ArF excimer laser light source (wavelength 193 nm) is used. As the light source 1, other laser light sources such as a KrF excimer laser light source (wavelength 248 nm), a mercury lamp, a harmonic generation light source such as a YAG laser, or a harmonic generation device such as a solid-state laser (for example, a semiconductor laser) may be used. Can be used.
The linearly polarized illumination light IL made up of ultraviolet pulsed light emitted from the light source 1 is converted into a desired shape by the beam expander 2, and then the illumination optics through the optical path bending mirror 3. The light enters the polarizing optical system 6 including the rotatable half-wave plate 4 and the quarter-wave plate 5 along the optical axis AXI of the system ILS. The main control system 20 controls the rotation angle of the half-wave plate 4 via a rotation drive unit (not shown), so that either of the two directions orthogonal to the polarization direction of the illumination light IL emitted from the polarization optical system 6 can be obtained. Or circularly polarized light. Further, by inserting a wedge-shaped birefringent prism (depolarizer) (not shown) into the optical path of the illumination light IL, the polarization state of the illumination light IL can be changed to random polarization (non-polarization). The detailed configuration of such a polarizing optical system 6 is disclosed in, for example, International Publication No. 2004/051717 pamphlet.

  The illumination light IL emitted from the polarization optical system 6 enters one of diffractive optical elements 7A, 7B, 7C, and the like. The diffractive optical element 7A diffracts the incident rectangular parallel light beam to form a circular illumination region in the far field. Furthermore, the incident illumination light IL is diffracted to form two illumination areas decentered in the X direction almost symmetrically with respect to the optical axis AXI in the far field. A diffractive optical element 7C for quadrupole illumination that forms four illumination regions that are decentered in the X direction and Z direction (corresponding to the Y direction on the pattern surface of the reticle R) substantially symmetrically with respect to the optical axis AXI, etc. And a diffractive optical element (not shown) for forming a two-pole and four-pole illumination area, a diffractive optical element (not shown) for forming an annular illumination area, and the like. These diffractive optical elements 7A to 7C and the like are held around the disk 8 as an example. In response to a command for setting an illumination condition from the main control system 20, the illumination control system 21 rotates the disk 8 by the drive unit 23, so that the diffractive optical element corresponding to the illumination condition is on the optical path of the illumination light IL. Placed in. In FIG. 1, a diffractive optical element 7A for normal illumination is set on the optical path of the illumination light IL.

  In FIG. 1, a light beam diffracted through the diffractive optical element 7A (or 7B, 7C, etc.) is a front group lens system 9a, a first prism 10a having a concave conical surface, and a second prism having a convex conical surface. The microlens array 11 as an optical integrator is illuminated through the axicon system 10 and the rear group lens system 9b. The front lens group 9a and the rear lens system 9b constitute a zoom lens (variable magnification optical system) 9 that can continuously change the focal length within a predetermined range. The zoom lens 9 optically couples the exit surface of the diffractive optical element 7A and the rear focal plane of the microlens array 11 optically in a conjugate manner.

  The illumination light IL emitted from the diffractive optical elements 7A to 7C and the like is collected in an illumination area having a predetermined shape such as a circular shape or a dipole shape on the rear focal plane of the zoom lens 9 (and hence the incident surface of the microlens array 11). To be lighted. As described above, the diffractive optical apparatus 7A and the like and the zoom lens 9 constitute an illumination area forming unit. The overall size of the illumination area changes depending on the focal length of the zoom lens 9. The focal length of the zoom lens 9 is controlled to a desired value by driving the lens system 9a of the zoom lens 9 along the optical axis AXI by a drive unit 24 including a slide mechanism, for example, based on a command from the illumination control system 21. The

  In the axicon system 10, the conical surfaces of the first prism 10 a and the second prism 10 b are arranged to face each other, and the second prism 10 b is based on a command from the illumination control system 21 and includes, for example, a drive unit 25 including a slide mechanism. Is driven along the optical axis AXI. Thus, by controlling the distance along the optical axis AXI of the prisms 10a and 10b, the position of the light beam emitted from the diffractive optical element 7A and the like in the radial direction with respect to the optical axis AXI on the incident surface of the microlens array 11 Can be controlled. Therefore, for example, when using the two-pole secondary light sources 42A and 42B shown in FIG. 2C described later, the secondary light sources 42A and 42B are controlled by controlling the distance between the prisms 10a and 10b of the axicon system 10 shown in FIG. The distance from the center optical axis AXI can be controlled. On the other hand, by controlling the focal length of the zoom lens 9, the individual sizes of the secondary light sources 42A and 42B can be controlled.

  The microlens array 11 is an optical element composed of a large number of microlenses having positive refractive power arranged densely in the vertical and horizontal directions. Each microlens constituting the microlens array 11 has a rectangular cross section similar to the shape of the illumination region to be formed on the reticle R (and thus the shape of the exposure region to be formed on the wafer W). The pupil plane (illumination pupil plane 12) of the illumination optical system ILS, which is the rear focal plane of the microlens array 11, has a light intensity distribution that is substantially the same as the illumination area formed by the incident light flux on the microlens array 11. A secondary light source composed of a secondary light source, that is, a substantial surface light source centered on the optical axis AXI is formed.

  In FIG. 1, illumination light IL from the secondary light source formed on the rear focal plane (illumination pupil plane 12) of the microlens array 11 defines the contour of the light intensity distribution of the secondary light source as necessary. After being limited via an aperture stop (not shown), via a first relay lens 13, a reticle blind 14 (field stop), a second relay lens 15, an optical path bending mirror 16, and a condenser optical system 17, The pattern surface (reticle surface) of the reticle R is illuminated in a superimposed manner. The illumination optical system ILS includes the optical members from the beam expander 2 to the condenser optical system 17. In this case, the arrangement plane of the reticle blind 14 is a conjugate plane of the reticle plane.

In the illumination optical system ILS, a photoelectric sensor (integrator sensor) (not shown) for monitoring the amount of illumination light IL being exposed is installed. With this photoelectric sensor, the main control system 20 can monitor the exposure amount (integrated exposure amount) for the wafer W.
In addition, instead of the prisms 10a and 10b, a prism in which a cone portion is a pyramid (or a pyramid shape), a prism having a hollow near the optical axis, or a plurality of portions processed separately and fixed integrally. Etc. may be used. Further, this position may be made variable along the optical axis AXI by using only the first prism 10a without using the two prisms 10a and 10b. Further, as the movable prism, a pair of V-shaped interval variable prisms (not shown) having a refractive power in one direction and no refractive power in a direction orthogonal thereto may be used. However, in FIG. 1, the axicon system 10 can be omitted when it is not necessary to change the position of the secondary light source on the illumination pupil plane 12 in the radial direction. Further, a fly-eye lens or the like may be used instead of the microlens array 11.

  Under the illumination light IL, an image of a predetermined circuit pattern in the illumination area of the reticle R is projected at a projection magnification β (β is, for example, 1/4, 1/5, etc.) via the bilateral telecentric projection optical system PL. Then, the image is transferred to the resist layer of one shot area among the plurality of shot areas on the wafer W arranged on the image plane of the projection optical system PL. The wafer W is a disk-shaped substrate having a diameter of 200 mm or 300 mm, such as a semiconductor (silicon or the like) or SOI (silicon on insulator).

  As the projection optical system PL of the present embodiment, a catadioptric projection optical system having a plurality of optical systems having optical axes intersecting each other as disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-47114, in addition to a refractive system. An optical system having an optical axis from the reticle to the wafer, and a catadioptric system having an optical axis substantially perpendicular to the optical axis, as disclosed in, for example, WO 01/065296 And a catadioptric projection optical system or the like that forms an intermediate image twice inside.

  The exposure apparatus 100 is an immersion exposure apparatus that performs exposure by an immersion method. In FIG. 1, the exposure apparatus 100 surrounds the distal end portion of the lens L1 on the most image plane side (wafer W side) constituting the projection optical system PL. In addition, a substantially ring-shaped nozzle unit 30 having an opening (not shown) through which the illumination light IL passes is held by a frame (not shown). The liquid supply path in the nozzle unit 30 is connected to the liquid supply apparatus 33 via the supply pipe 35A, and the liquid recovery path in the nozzle unit 30 is connected to the liquid recovery apparatus 34 via the recovery pipe 35B.

  The operations of the liquid supply device 33 and the liquid recovery device 34 are controlled by the main controller 20. Including a liquid supply device 33, a liquid recovery device 34, a supply pipe 35A, a recovery pipe 35B, and a nozzle unit 30, a local liquid immersion region 36 between the lens L1 at the tip of the projection optical system PL and the wafer W is provided. A local liquid immersion type liquid supply / recovery system that supplies and recovers the liquid Lq is configured. As the liquid Lq, for example, ultrapure water (hereinafter simply referred to as water) through which illumination light IL (here, ArF excimer laser light) passes is used. The refractive index n of the water illumination light IL is approximately 1.44. Therefore, the wavelength of the illumination light IL for exposing the wafer W is shortened to about 134 nm (= 193 nm × 1 / n), and the resolution and the depth of focus are improved.

The liquid supply / recovery system of the present example includes the ring-shaped nozzle unit 30. However, the present invention is not limited thereto. For example, as disclosed in International Publication No. 99/49504, a plurality of liquid supply systems are provided. It is also possible to configure a liquid supply and recovery system including a nozzle member and a plurality of nozzle members that recover the liquid.
In FIG. 1, the reticle R is sucked and held on the reticle stage RST so that the reticle surface is arranged on the object plane of the projection optical system PL parallel to the XY plane. The reticle stage RST is a reticle base (not shown). It is mounted so as to be movable at a constant speed in the Y direction and finely movable in at least the X direction, the Y direction, and the rotation direction around the Z axis. The position (including rotation) of reticle stage RST is measured by a laser interferometer in reticle stage drive system 31. Reticle stage drive system 31 controls the position and speed of reticle stage RST via a drive mechanism (not shown) based on the measurement information and control information from main control system 20.

  On the other hand, wafer W is sucked and held on wafer stage WST via a wafer holder (not shown), and wafer stage WST is placed on a wafer base (not shown) so as to be movable in the X and Y directions. The position (including rotation) of wafer stage WST is measured by a laser interferometer in wafer stage drive system 32. Wafer stage drive system 32 controls the position and speed of wafer stage WST via a drive mechanism (not shown) based on the measurement information and control information from main control system 20. In addition, wafer stage WST has wafer W W within exposure area (irradiation area of illumination light IL conjugate with illumination area with respect to projection optical system PL) during scanning exposure based on measurement information of an autofocus sensor (not shown). A focusing mechanism for aligning the surface with the imaging plane of the projection optical system PL is incorporated.

  The main control system 20 is connected to a simulator 22 (arithmetic unit) composed of a computer for evaluating (predicting) the cross-sectional shape of the resist pattern formed on the resist layer after the development of the wafer W. The simulator 22 executes a program for evaluating the cross-sectional shape of the resist pattern. The simulator 22 includes a first calculation unit 22a, a second calculation unit 22b, and a third calculation unit 22c, which will be described later, which are functions (software functions) executed by the program. In addition, it is also possible to implement | achieve these calculating parts 22a-22c separately with a hardware. Further, an input / output unit 19 for inputting / outputting various commands and various information to / from the operator is connected to the main control system 20.

Hereinafter, an example of an exposure operation including an operation for preliminarily evaluating the cross-sectional shape of the resist pattern in the exposure apparatus 100 will be described with reference to the flowchart of FIG.
First, in step 101 of FIG. 8, the reticle R to be exposed is loaded on the reticle stage RST of FIG. In the next step 102, the main control system 20 reads information on the finest pattern on the reticle R (hereinafter simply referred to as the pattern of the reticle R) from the exposure data file of the reticle R stored in the internal storage device, the reticle. Information such as illumination conditions for R, magnification and numerical aperture of projection optical system PL (set by an aperture stop (not shown)), sensitivity of a known resist on the wafer (appropriate exposure), and the like are read. Then, the main control system 20 sets the shape of the secondary light source on the illumination pupil plane 12 according to the read illumination condition, sets the polarization illumination in the polarization optical system 6 and projects via the illumination control system 21. The numerical aperture of the optical system PL is set. When the number of exposure pulses of the illumination light IL for each point on the wafer W during scanning exposure is N and the pulse energy of the illumination light IL on the wafer W is EPU, the exposure amount (integrated exposure amount) for the wafer W is N × EPU. Therefore, the exposure amount can be controlled by controlling the number of exposure pulses N and / or the pulse energy EPU.

Information on the pattern of the reticle R, its illumination conditions (the wavelength of the illumination light IL, the wavelength width, the shape of the secondary light source, the polarization illumination), the resist sensitivity, the numerical aperture of the projection optical system PL, etc. are stored in the storage unit of the simulator 22 Is also stored.
In the next step 103, the main control system 20 performs information such as the resist thickness (set value) h, transmittance Th, and refractive index on the wafer, and the reflectance of the resist on the wafer (substrate reflectance). Information on WR (for example, about 0 to several percent) is input from the exposure data file, and the input information is stored in the storage unit of the simulator 22. When the first layer on the wafer is exposed, the substrate reflectivity WR is equal to the reflectivity of the surface of the wafer before resist application. Further, when an antireflection film is formed on the surface of the wafer, the substrate reflectance WR is small. If a high-performance antireflection film is formed, the substrate reflectivity WR decreases, but the number of device manufacturing steps increases and the manufacturing cost increases. Therefore, it is preferable to adjust the exposure conditions including the illumination conditions so that the device can be manufactured with a high throughput even if there is a certain substrate reflectivity WR.

  Further, the main control system 20 determines, from the exposure data file related to the exposure apparatus 100, the aberration of the projection optical system PL, the refractive index of the liquid Lq during immersion exposure, and the average focus fluctuation (defocus) with respect to the projection optical system PL. Imaging error (for example, line width error), imaging error due to image vibration MSD which is the vibration of reticle stage RST and wafer stage WST, imaging error due to the degree of polarization of illumination light IL, and illumination optical system ILS and projection optical system PL The information on the image formation error due to the flare is read, and the information affecting the state of the image of the reticle pattern is stored in the storage unit of the simulator 22.

  Here, as an example, it is assumed that the pattern of the reticle R is a line and space pattern (hereinafter referred to as an L & S pattern) 41X formed in the X direction in FIG. . In addition, the illumination conditions at this time are two-pole illumination in the X direction using secondary light sources 42E and 42F elongated in the Z direction shown in FIG. 2E, and the polarization state of the illumination light IL on the reticle surface is changed in the Y direction. Let it be linearly polarized light (V polarized light). In FIG. 2E, a circumference 42G defines a coherence factor (σ value) in the illumination pupil plane 12, and the outer edge portions of the secondary light sources 42E and 42F are inscribed in the circumference 42G.

  Further, as an example, it is assumed that the line width at the stage of the projected image of the L & S pattern 41X is 37.5 nm, the period (pitch) is 75 nm, and the L & S pattern 41X is a halftone with a light transmittance of 6%. . Accordingly, the numerical aperture NA of the projection optical system PL is set to 1.35 (when using the liquid immersion method), and the σ value (σout) outside the secondary light sources 42E and 42F in FIG. The inner σ value (σin) is 0.843 (σin / σout = 0.86). Further, the degree of polarization of the illumination light IL is defined by the following DSP or RSP. In the following expression, Ix is the intensity of the target polarization component (here, V-polarized light), and Iy is the intensity of a polarization component different from the target polarization component (here, H-polarized light orthogonal to V-polarization).

DSP = | Ix−Iy | / (Ix + Iy) (1A)
RSP = Ix / (Ix + Iy) (1B)
In this case, as an example, the polarization degree DSP of the illumination light IL is set to 0.85 (the polarization degree RSP is 0.925).
As illumination conditions, it is also possible to use bipolar illumination in the X direction using circular secondary light sources 42A and 42B shown in FIG.

  3A and 3C are enlarged views showing a part of the exposure surface of the wafer W in FIG. 3A and 3C, a resist PR having a thickness h is applied on the wafer W. The 0th-order light emitted from one secondary light source 42A in FIG. 2C and passing through the L & S pattern 41X and the projection optical system PL in FIG. 2A is incident on the incident angles in FIGS. 3A and 3C. The first-order diffracted light emitted from the secondary light source 42A, diffracted by the L & S pattern 41X, and passed through the projection optical system PL as the light beam IL1 of θ (rad) is defined as the light beam IL2 of incident angle θ in FIG. . At this time, due to the interference of the light beams IL1 and IL2, the intensity distribution corresponding to the image 43X (see FIG. 3B) of the L & S pattern 41X by the projection optical system PL in the resist PR, that is, the X direction along the surface of the resist PR. A sinusoidal intensity distribution SX indicated by a solid line 44A in FIG. In FIG. 3B and later-described FIG. 3D, the portion with higher light intensity is shown in white.

  Information affecting the reticle pattern, illumination conditions (wavelength of illumination light IL, shape of secondary light source, etc.), magnification and numerical aperture of projection optical system PL, refractive index of liquid Lq, projection image (projection above) By using information such as aberration of the optical system PL, error due to focus fluctuation, error due to stage vibration (image vibration), resist thickness h, resist refractive index, resist transmittance Th, and the like, FIG. The first calculator 22a of the simulator 22 can calculate the intensity distribution SX. At this time, the intensity of the light beam IL1 may be set to a predetermined reference intensity, for example. Approximately, the intensity distribution SX can be calculated by representing the light beams IL1 and IL2 by plane waves whose phases partially change according to the aberration, and obtaining the absolute value of the sum thereof. The intensity distribution SX can be approximately expressed as follows using AX1 and average value AX2 which are ½ of the amplitude, and the contrast CSX is as follows.

SX = AX1 · sin (2π · X / PX) + AX2 (2A)
CSX = (AX1 / AX2) × 100 (%) (2B)
Actually, the intensity distribution SX is similar to that caused by interference of the 0th-order light emitted from the other secondary light source 42B of FIG. 2C and transmitted through the L & S pattern 41X and the primary light diffracted by the L & S pattern 41X. The intensity distribution is also superimposed. The intensity distribution SY of the image of the L & S pattern in the Y direction can be similarly calculated.

  Instead of directly calculating the intensity distribution SX, as shown in FIGS. 9A to 9D, the sensitivity for each error factor that lowers the contrast CSX of the intensity distribution of the projected image in advance (decrease in contrast) (Amount / variation amount of each factor) may be obtained and stored. 9 (A), 9 (B), 9 (C), and 9 (D) show focus variation (nm), image vibration MSD (nm) due to stage vibration, and polarization degree RSP of illumination light, respectively. Also, the contrast reduction amount ΔC caused by effective flare (%) is shown. The effective flare (Fef) is a sum of 0.5 times the flare (lens flare) FPL of the projection optical system PL and 0.25 times the flare (illumination flare) FILS of the illumination optical system ILS as follows. Defined.

Fef = FPL × 0.5 + FILS × 0.25 (3)
The influence of the lens flare FPL is proportional to the aperture ratio of the reticle R pattern, and the aperture ratio when the L & S pattern is formed on the entire surface of the reticle R is 0.5. Further, the influence of the illumination flare FILS is calculated by approximating the illumination light from a direction that does not contribute to image formation (only the 0th-order light passes).

From FIGS. 9A to 9D, when the focus variation is Fz (nm), the image vibration MSD is V (nm), the polarization degree RSP is P, and the effective flare is Fef, the value is obtained in advance by actual measurement or calculation. Using the stored sensitivity (coefficients) kz, kv, kp, kf, the contrast reduction amount ΔC can be expressed as follows.
ΔC = −kz · Fz ² , ΔC = −kv · V ² , ΔC = −kp (1-P),
ΔC = −kf · Fef (4)
As described above, with respect to the focus fluctuation Fz and the image vibration V, the contrast reduction amount is a quadratic function of Fz and V, and the contrast reduction due to other error factors is a linear function. Further, when the contrast of the intensity distribution SX calculated when the focus fluctuation Fz, the image vibration V, the polarization degree error (1-P), and the effective flare Fef are 0 (ideal state) is C ₀ , Using 4), the contrast CSX when there is the above error factor can be calculated as follows.

^{_{CSX = C 0 -kz · Fz 2}} -kv · V 2 -kp (1-P) -kf · Fef ... (5)
Here, since the pattern to be transferred is the L & S pattern 41X in the X direction, only the image vibration (X-MSD) in the X direction has to be considered as the image vibration V.
Specifically, FIG. 10 shows that when the illumination flare FILS is 2.0% (Fef = 0.5%) and the polarization degree P (RSP) is 0.925, the image vibration V and the focus fluctuation Fz are gradually changed. However, contrast CSX calculated using equation (5) is shown. In FIG. 10, the horizontal axis represents the image vibration (X-MSD) (nm) in the X direction, the vertical axis represents the focus fluctuation Fz (nm), and the regions CF1, CF2, CF3, CF4, CF5 separated by the solid curve. , CF6, CF7, CF8, CF9, CF10, and CF11, the calculated contrast CSX is 0.5-0.52, 0.48-0.5, 0.46-0.48, 0.44-0, respectively. .46, 0.42-0.44, 0.4-0.42, 0.38-0.4, 0.36-0.38, 0.34-0.36, 0.32-0.34 , 0.3-0.32.

If the required contrast CSX is 0.42, it can be seen from FIG. 10 that the allowable value of image vibration (X-MSD) when the focus variation is 35 nm is approximately 7 nm.
In this calculation example, the influence of wavefront aberration is small because the illumination aperture (secondary light source) is small. However, when the illumination aperture is large, the influence of wavefront aberration is also considered.

  Further, as shown in FIG. 2B, when the pattern of the reticle R includes the L & S pattern 41X in the X direction and the L & S pattern 41Y in the Y direction as shown in FIG. In addition, quadrupole illumination using cross-shaped quadrupole secondary light sources 42A, 42B, 42C, and 42D is obtained. In this case, regarding the image formation of the L & S pattern 41X in the X direction, the illumination light from the two secondary light sources 42C and 42D arranged in parallel to the Z axis becomes an offset component. Accordingly, the contrast of the intensity distribution SX in the X direction of the image decreases as shown by the dotted curve 44B in FIG. 3B (level adjustment is performed so that the average values match).

  Next, in FIG. 3C, the light beam IL1 passes through the resist PR having the transmittance Th and is reflected by the ground having the reflectance WR, whereby reflected light IL1R is generated from the ground (the surface of the wafer W). Then, due to the interference between the light beam IL1 and the reflected light IL1R, a standing wave 43Z having an intensity distribution SZ is formed in the resist PR with a period PZ in the Z direction indicated by a solid line 45A in FIG. In FIG. 3C, the angle φ (rad) formed by the light beam IL1 and the reflected light IL1R with respect to the plane parallel to the lower ground of the wafer W is as follows using the angle θ of FIG. .

φ = π / 2−θ (6)
Accordingly, the second calculation unit 22b of the simulator 22 in FIG. 1 performs the reticle R pattern, its illumination conditions (the wavelength of the illumination light IL, the shape of the secondary light source, etc.), the magnification and numerical aperture of the projection optical system PL, and the liquid Lq. Of the standing wave 43Z formed in the resist PR on the wafer W using information such as the refractive index of the resist, the refractive index of the resist, the resist thickness h, the resist transmittance Th, and the substrate reflectance WR. The direction intensity distribution SZ is calculated. For example, the intensity distribution SZ may be calculated by approximating the light beam IL1 and the reflected light IL1R with a plane wave using the angle φ and obtaining the absolute value of the sum thereof.

The intensity distribution SZ in the Z direction of the standing wave 43Z can be approximately expressed as follows using BX1 and average value BX2 which are ½ of the amplitude, and the contrast CSZ is as follows. At this time, the phase of the reflected light IL1R changes by π at the time of reflection.
SZ = BX1 · sin (2π · Z / PZ + π) + BX2 (0 ≦ Z ≦ h) (7A)
CSZ = (BX1 / BX2) × 100 (%) (7B)
Actually, the intensity distribution SZ is emitted from the standing light wave IL2 shown in FIG. 3A and the reflected light IL2R shown in FIG. 4B, and the other secondary light source 42B shown in FIG. 2C. The intensity distribution of the standing wave based on the 0th order light and the 1st order light passing through the L & S pattern 41X is also superimposed. Further, when the substrate reflectance WR of the wafer W is reduced, the standing wave intensity distribution SZ is reduced as a whole, as indicated by a dotted curve 45B in FIG.

  Therefore, in step 104 of FIG. 8, the first calculation unit 22a of the simulator 22 of FIG. 1 uses the exposure conditions including the pattern of the reticle R and the illumination conditions as described above on the surface of the resist PR on the wafer W. An intensity distribution SX that can be approximated by, for example, Expression (2A) of the pattern image of the reticle R in the direction along the X direction (here, the X direction) is calculated. Further, the first calculation unit 22a calculates the contrast CSX represented by the expression (2B) or the expression (5) of the intensity distribution SX, and stores these calculation results in the storage unit. The intensity of the illumination light IL at this time is a predetermined reference intensity.

In the next step 105, the second calculation unit 22b of the simulator 22 of FIG. 1 uses the exposure condition including the pattern of the reticle R, the illumination condition, and the substrate reflectivity WR as described above to apply the resist PR on the wafer W. An intensity distribution SZ in the Z direction that can be approximated by, for example, Expression (7A) of the standing wave formed inside is calculated, and the calculation result is stored in the storage unit.
In the next step 106, as an example, the third calculation unit 22c of the simulator 22 in FIG. 1 adds the intensity distribution SX calculated in step 104 and the intensity distribution SZ calculated in step 105 as follows. Then, the intensity distribution S (X, Z) of the illumination light in the X direction and the Z direction in the resist PR layer on the wafer W is obtained. At this time, the smaller the contrast CSX of the original image intensity distribution SX, the greater the influence of the standing wave intensity distribution SZ.

S (X, Z) = SX + SZ (8)
FIG. 4A shows an example of the intensity distribution S (X, Z) in the resist PR on the wafer W by contour lines 46, 46A to 46D. Further, since the exposure amount (integrated exposure amount) for the resist PR is obtained by multiplying the intensity of the illumination light IL by the exposure time, by multiplying the exposure time assumed for the intensity distribution S (X, Z), The exposure amount distribution in the resist PR can be obtained. In other words, the contour lines 46 and 46A to 46D in FIG. 4A can be regarded as the contour lines of the exposure amount. The contour lines of the exposure amount in FIG. 4A are obtained a plurality of times by changing the exposure time (integrated exposure amount) to a plurality.

  In the next step 107, the third calculation unit 22c is formed after developing the resist PR of the wafer W using the intensity distribution S (X, Z) approximated by the equation (8). The minimum line width dmin of the resist pattern 47 is predicted (obtained). For example, when the exposure amount by the illumination light IL is matched with the resist sensitivity (appropriate exposure amount), it is assumed that the contour line 46 in FIG. 4A is the appropriate exposure amount. At this time, the contour line 46A represents an exposure amount smaller than the appropriate exposure amount, and the contour lines 46C and 46D represent exposure amounts larger than the appropriate exposure amount. Note that many contour lines 46, 46A to 46D are actually drawn at finer intervals on the image data, for example.

Therefore, when the illumination light IL is irradiated with an appropriate exposure amount, the contour line 46 becomes the cross-sectional shape of the resist pattern 47 shown in FIG. 4C as it is after the development of the resist PR shown in FIG. The line width of the resist pattern 47 also periodically changes in the Z direction due to the intensity distribution of the L & S pattern image in the X direction and the intensity distribution of the standing wave.
Note that the shape of the resist pattern 47 after development is affected to some extent by PEB (post-exposure bake) performed after exposure of the resist PR and before development. Therefore, the influence of PEB (resist diffusion effect) may be obtained in advance by test printing or the like, and the resist pattern may be corrected in consideration of the influence of PEB when obtaining the shape of the resist pattern in step 107.

  Further, when obtaining the minimum line width dmin of the resist pattern 47 in FIG. 4C, the maximum line width dmax is also obtained. In this case, the resist pattern 47 has the minimum line width dmin in the bright part where the intensity of the standing wave 43Z (see FIG. 3D) is the largest, and the maximum line width dmax in the dark part where the intensity of the standing wave 43Z is the smallest. Become. Then, while increasing or decreasing the exposure amount of the illumination light IL by a predetermined amount ΔE with respect to the appropriate exposure amount, the resist pattern obtained from the intensity distribution S (X, Z) of FIG. The minimum line width dmin and the maximum line width dmax of the cross-sectional shape are obtained. For example, when the exposure amount of the illumination light IL is increased more than the appropriate exposure amount, a contour line (not shown) shifted to the contour line 46A side with respect to the contour line 46 in FIG. 4A represents a new cross-sectional shape.

  In the present embodiment, as an example, the exposure amount when the maximum line width dmax is 1/2 of the period PX of the resist pattern 47 (design target value) is the exposure amount when the wafer is actually exposed. . Then, the minimum line width dmin when the maximum line width dmax of the resist pattern 47 reaches the target value (= PX / 2) is set as the finally predicted minimum line width, and the maximum line width dmax at that time and The minimum line width dmin is output to the main control system 20 in FIG.

  FIGS. 5A, 5B, and 5C are images of an L & S pattern in the X direction with a period of 75 nm (line width of 37.5 nm) at the projection image stage, and the substrate reflectance WR is 0%, The resist patterns 47A, 47B, and 47C predicted to be formed after calculation are projected onto a 1% and 2% wafer resist under the condition that the maximum line width is 37.5 nm. Also, the dotted resist pattern 47D in FIG. 5C is a pattern predicted when the substrate reflectance is further 3%. 5A to 5C, it can be seen that the minimum line width dmin of the resist patterns 47A to 47D becomes smaller and more easily falls as the substrate reflectance WR becomes larger.

  FIG. 6A shows the substrate reflectance WR (%) and the minimum line width dmin (nm) of the resist pattern when the contrast of the projected images of the L & S pattern having a period of 75 nm (line width is 37.5 nm) is different. ) Shows an example of a predicted relationship. In FIG. 6A, a curve 51A is obtained when the contrast of the projection image is high using the dipole illumination of FIG. 2C, and a curve 51B is obtained by using the quadrupole illumination of FIG. When the contrast is low, the curve 51C is the minimum line width dmin of the resist pattern that is predicted when the contrast of the projected image is further lowered by 5% using the quadrupole illumination.

  FIG. 6B shows the maximum line of the resist pattern after development when the contrast of the projected image is decreased by 5% from 100% to 55% under the same conditions as in FIG. 6A. The minimum line width dmin when the width dmax is ½ of the period is obtained by simulation. From FIG. 6B, the higher the substrate reflectance, the larger the standing wave effect and the smaller the minimum line width dmin. However, when the contrast of the projected image is high, the minimum even if the substrate reflectance increases. It can be seen that the line width dmin does not become too small.

  Accordingly, the characteristics of FIG. 6B are stored in advance for a plurality of periods, and in the step corresponding to step 104 of FIG. 8, the contrast of the expression (2B) or expression (5) of the projection image of the reticle pattern is set. In the process corresponding to steps 105 to 107, the minimum line width dmin of the resist pattern after development is predicted by applying the substrate reflectivity and its contrast to the characteristics of FIG. 6B corresponding to the period of the pattern. May be. In this case, once the characteristics shown in FIG. 6B are calculated, the minimum line width dmin of the resist pattern after development can be easily obtained.

  FIG. 7 shows the case of the curve 51B of FIG. 6A (4-pole illumination) when the exposure amount is reduced by 4% with respect to the appropriate exposure amount (curve 52A), and the case of the appropriate exposure amount (curve). 52B) and an example of a predicted relationship between the substrate reflectivity and the minimum line width dmin of the resist pattern when the amount of exposure is increased by 4% (curve 52C). From FIG. 7, it can be seen that when the exposure amount is increased, the minimum line width dmin is further reduced, and the resist pattern is easily tilted. It can be seen that the influence of the exposure dose has little dependence on the substrate reflectivity.

  Next, at step 108 in FIG. 8, the main control system 20 determines whether or not the minimum line width dmin is greater than or equal to a predetermined allowable value determined in advance according to the maximum line width dmax (or period PX). To do. When the minimum line width dmin is smaller than the permissible value, the resist pattern 47 may fall during, for example, a drying process during the development process. Therefore, when the minimum line width dmin is smaller than the allowable value, the routine proceeds to step 109 where an operator call is performed as an example. Then, for example, when the operator has instructed the main control system 20 to change at least one of the illumination conditions, the numerical aperture of the projection optical system PL, the substrate reflectance, etc., the process proceeds to step 110. Then, the main control system 20 stores data such as the changed illumination conditions in the storage unit of the simulator 22. Thereafter, returning to step 104, the simulator 22 executes steps 104 to 107 to calculate the light intensity distribution in the resist PR of the wafer W, and the maximum line width dmax and the minimum line of the resist pattern 47 after development. Predict the width dmin.

Instead of making an operator call as in step 109, the process may directly move from step 108 to step 110 to change the illumination conditions in a predetermined order.
In step 108, if the minimum line width dmin is equal to or larger than the allowable value, the process proceeds to step 111, and the pattern of the reticle R is actually exposed on the wafer W coated with the resist in step 121.

  That is, in the exposure apparatus 100 shown in FIG. 1, the main control system 20 determines the illumination conditions of the illumination optical system ILS and the projection optical system PL used in the calculation when the minimum line width dmin becomes equal to or larger than the allowable value in step. The exposure conditions such as the numerical aperture and the exposure amount are set. Thereafter, under the control of main control system 20, reticle stage drive system 31, and wafer stage drive system 32, wafer stage WST is driven in the X and Y directions, and wafer W is stepped to the scan start position. The Subsequently, supply of the liquid Lq to the liquid immersion area 36 is started, irradiation of the illumination light IL is started, and the reticle R is scanned at a speed VR in the Y direction with respect to the illumination area via the reticle stage RST. In synchronism with this, scanning exposure is performed by scanning one shot area on the wafer W in the direction corresponding to the exposure area at a speed β · VR (β is the projection magnification) via the wafer stage WST. The pattern image of the reticle R is transferred to all shot areas on the wafer W by a step-and-scan operation that repeats the step movement and the scanning exposure.

  Thereafter, in step 112, wafer W on wafer stage WST in FIG. 1 is replaced with the next unexposed wafer, and in step 111, the wafer is exposed. On the other hand, the wafer that has been exposed in step 111 is transported from the exposure apparatus 100 to a coater / developer (not shown). After PEB (baking before development) is performed in step 122, the resist on the wafer is developed in step 123. And drying. In the next step 124, substrate processing including heating (curing) of the developed wafer and etching process is performed. Then, in the next step 125, after repeating the lithography process and the substrate processing process as necessary, the semiconductor is subjected to a device assembly step (including processing processes such as a dicing process, a bonding process, and a packaging process), an inspection step, and the like. Devices such as devices are manufactured.

At this time, in this embodiment, the illumination conditions and the like are set in advance so that the minimum line width dmin of the resist pattern is equal to or larger than the allowable value in Step 108. Therefore, the line width of the resist pattern is equal to or greater than the allowable value, and the resist pattern does not fall during the wafer development process in step 123, and the device can be manufactured with high throughput and high accuracy.
The effect of this embodiment is as follows.

  (1) The simulator 22 (projection image evaluation apparatus) that is provided in the exposure apparatus 100 of FIG. 1 of the present embodiment and evaluates the cross-sectional shape of the resist pattern formed after development on the resist PR on the wafer W is step 104. In contrast, the contrast information of the intensity distribution in the direction (X direction) along the surface of the resist PR of the illumination light IL when the resist PR is exposed (the intensity distribution SX and / or the expression (2B) in the expression (2A) (or the expression) (5)) has a first calculation unit 22a for obtaining the contrast CSX). Further, in Step 105, the simulator 22 obtains information on the standing wave 43Z in the resist PR from the substrate reflectance WR of the wafer W (intensity distribution SZ in Expression (7A), contrast CSZ in Expression (7B), and substrate reflectance WR. Of the resist pattern (image) formed after development on the resist PR based on the contrast information and the standing wave information in steps 106 and 107. And a third arithmetic unit 22c for obtaining a maximum line width dmax and a minimum line width dmin (line width information).

  According to the present embodiment, for example, by adding the intensity distribution SZ of the standing wave as the standing wave information to the intensity distribution SX of the image of the reticle pattern as the contrast information, A two-dimensional light intensity distribution is required. From the light intensity distribution and the sensitivity of the resist PR, the cross-sectional shape of the resist pattern formed on the resist PR after development, and thus the line width information can be obtained. Therefore, the cross-sectional shape of the resist pattern formed on the resist of the wafer W after development can be efficiently evaluated without actually exposing the wafer W.

  (2) In addition, when the third arithmetic unit 22c obtains (predicts) the maximum line width dmax and the minimum line width dmin (line width information) of the resist pattern, the exposure amount of the illumination light IL is changed to the sensitivity of the resist PR. A plurality of exposure amounts including (appropriate exposure amount) are set (step 107). Therefore, the actual appropriate exposure amount when the optimum line width can be finally obtained with the resist pattern can be obtained.

  (3) In this embodiment, the resist PR on the wafer W is exposed with illumination light IL from the illumination optical system ILS (illumination system) via the pattern of the reticle R and the projection optical system PL (projection system). . Then, when obtaining the contrast information when the resist PR is exposed in step 104, the first arithmetic unit 22a calculates the intensity distribution of the illumination light IL on the pupil plane of the illumination optical system ILS, the aberration of the projection optical system PL, and the resist. Defocus information (predicted defocus amount or focus variation) from the image plane of the projection optical system PL of PR (wafer W) is used. Therefore, the contrast information can be obtained with high accuracy. For example, when the cross-sectional shape of the resist pattern is roughly evaluated, the contrast information may be obtained using at least one piece of information.

  (4) In Steps 106 and 107, when the pattern formed on the resist PR of the wafer W is an image of the L & S pattern 41X in FIG. C) When obtaining the line width information of the resist pattern 47, the line width (maximum line width dmax) of the line portion of the resist pattern 47 in the dark portion (the portion with the smallest intensity) of the standing wave is a predetermined line width ( Here, the line width (minimum line width dmin) of the line part in the bright part of the standing wave when the period is ½ of the period PX is obtained. Therefore, the maximum line width and the minimum line width of the cross section of the resist pattern can be obtained, and the cross section can be accurately evaluated.

  (5) In the exposure method of FIG. 8 of the above embodiment, in the exposure method of exposing the resist on the wafer with the illumination light IL, step 102 for setting the exposure conditions (illumination conditions, exposure amount, etc.) for the wafer; Steps 104 to 107 for obtaining line width information of a resist pattern formed after development on the resist under the set exposure conditions using the resist pattern cross-sectional evaluation method (projected image evaluation method), And a step 110 of changing the set exposure condition based on the obtained line width information. Therefore, exposure conditions can be set so that a desired cross-sectional shape of a resist pattern can be obtained efficiently without actually performing exposure.

(6) Further, in the exposure method, the minimum line width dmin of the resist pattern is obtained in step 107 for obtaining the line width information, and the exposure condition is set so that the obtained minimum line width is not less than a predetermined allowable range. Has changed. Therefore, for example, it is possible to reliably prevent the resist pattern from collapsing in the developing process after the wafer is actually exposed.
(7) The exposure method of FIG. 8 can also be regarded as a management method of the exposure apparatus 100 of FIG. This management method is a management method of the exposure apparatus 100 that exposes the resist on the wafer W with the illumination light IL. The exposure apparatus 100 sets exposure conditions for the resist (wafer W) (steps 102 and 103). Using the projected image evaluation method, line width information of a resist pattern (image) formed on the resist after development under the set exposure conditions is obtained (steps 104 to 107), and the obtained line is obtained. The exposure result by the exposure apparatus 100 is evaluated based on the width information (step 108).

According to this management method, since the state of the cross section of the resist pattern formed on the wafer W after development can be predicted efficiently without actually performing exposure with the exposure apparatus, the load on the exposure apparatus can be reduced.
(8) In this management method, it is preferable to change the set exposure condition based on the evaluation of the exposure result (steps 108 and 110). Thus, the exposure conditions can be optimized in order to obtain a resist pattern having a desired cross-sectional shape after development without actually performing exposure.

  (9) The exposure apparatus 100 in FIG. 1 is an exposure apparatus that exposes the resist (photosensitive layer) of the wafer W with the illumination light IL, and the simulator 22 (projected image evaluation apparatus) of the above embodiment and the wafer W ( A resist pattern (image) formed after development on the resist obtained by the simulator 22 under the set exposure conditions and the illumination control system 21 etc. (setting unit) for setting the exposure conditions (illumination conditions etc.) for the resist) ), And a main control system 20 (control unit) for changing the set exposure condition. Therefore, the exposure conditions can be optimized so that a resist pattern having a desired cross section can be obtained without actually performing exposure.

(10) In this case, the simulator 22 determines the minimum line width of the resist pattern (step 107), and the main control system 20 determines that the determined minimum line width is within a predetermined allowable range (for example, the resist pattern is It is preferable to change the exposure conditions so as to be equal to or greater than the line width that does not fall down (step 110).
(11) In the device manufacturing method of the above embodiment, the resist on the wafer W is exposed using the exposure apparatus 100 of the above embodiment (step 111), and the exposed resist (wafer W). (Step 123). In this case, since the exposure conditions can be optimized in advance so that the developed resist pattern has a desired cross-sectional shape before exposure, devices can be manufactured with high throughput and high yield.

In the above embodiment, the following changes are possible.
First, in the above embodiment, the minimum line width dmin of the resist pattern is compared with an allowable value. However, for example, the average value of the line width of the cross section of the resist pattern can be compared with an allowable value. Further, the standard deviation (variation) of the line width of the cross section of the resist pattern may be compared with an allowable value.

In the above embodiment, the pattern to be transferred is the L & S pattern 41X in the X direction. However, the pattern to be transferred (reticle pattern) may be the L & S pattern 41Y in the Y direction in FIG. In this case, for example, bipolar illumination using a secondary light source obtained by rotating the secondary light source of FIG. 2C by 90 ° may be used as the illumination condition.
The pattern to be transferred may be a pattern including L & S patterns having various periods (line widths) in the X direction and / or the Y direction. In this case, for example, the illumination conditions may be adjusted so that the minimum line width of the resist pattern obtained from the image of the L & S pattern having the smallest period (line width) is equal to or greater than the allowable value.

  Further, for example, as shown in FIG. 11A, the pattern to be transferred includes L & S patterns 63A and 63B in which a plurality of line portions 62 elongated in the Y direction are arranged in a predetermined cycle in the X direction, and line portions that are long in the Y direction. The line pattern 61 having a line width wider than 62 may include a pattern formed close to the X direction. Images of the line portion 62 and the patterns 63A, 63B, and 61 in FIG. 11A by the projection optical system PL are referred to as an image 62P and images 63AP, 63BP, and 61P in FIG. In this case, for example, in order to evaluate the ease of collapse of the resist pattern obtained by developing the image 63P of the L & S pattern, the contrast C (62P) of the image 62P of the line portion closest to the line pattern image 61P in the image 63P. Is defined as follows.

  In this case, CL is the intensity at the center point 64L of the space portion between the images 62P and 61P, and CR is the center point 64R of the space portion between the image 62P and the image of the line portion adjacent thereto. The intensity at CC, CC, is the intensity at the center point 64C of the image 62P. Intensities CL, CR, and CC are obtained by calculation, for example. And the average intensity | strength Cav of the points 64L and 64R is calculated | required as follows.

Cav = (CL + CR) / 2 (9)
As an example, the contrast C (62P) of the image 62P in the line portion is defined by the following equation using the average intensity Cav and the intensity CC.
C (62P) = | Cav−CC | / (Cav + CC) (10)
Then, the minimum line width of the resist pattern corresponding to the image 62P when the contrast C (62P) and the substrate reflectance are changed is obtained in advance, and the illumination conditions and the like are set so that the minimum line width is equal to or greater than the allowable value. May be adjusted.

  Furthermore, when evaluating the cross-sectional shape of the resist pattern, the contrast ratio between the intensity distribution SZ of the standing wave 43Z in FIG. 3D and the intensity distribution SX of the reticle pattern image 43X in FIG. RSI) may be determined. Using AX1 that is ½ of the amplitude of the intensity distribution SX in Expression (2A) and BX1 that is ½ of the amplitude of the intensity distribution SZ in Expression (7A), the contrast ratio is approximated as an example. (RSI) can be expressed as:

RSI = BX1 / AX1 (11A)
Note that the contrast ratio (RSI) can be calculated directly from the following equation using the contrast CSZ of the standing wave 43Z of equation (7B) and the contrast CSX of the intensity distribution of the reticle pattern image of equation (5). Good.
RSI = CSZ / CSX2 (11B)
FIG. 12 shows the contrast ratio (RSI) between the standing wave and the image with respect to the substrate reflectance WR in the case of FIG. 6A, and the curves 53A, 53B, and 53C in FIG. The calculation results when the contrast of the image is reduced by 5% by dipole illumination, quadrupole illumination, and quadrupole illumination are shown. In this case, the lower the contrast of the image, the higher the contrast ratio (RSI), and the resist pattern after development is more likely to fall. Therefore, for example, the value of the contrast ratio (RSI) when the minimum line width of the resist pattern becomes the above allowable value is obtained in advance as the allowable value RSIth, and exposure is performed so that the contrast ratio (RSI) is equal to or less than the allowable value RSIth. By setting the conditions, a resist pattern having a desired cross-sectional shape can be obtained after development.

The present invention can be applied not only to a scanning exposure type projection exposure apparatus but also to exposure using a batch exposure type (stepper type) projection exposure apparatus. The present invention can also be applied to the case where exposure is performed with a dry exposure type exposure apparatus.
Further, as disclosed in, for example, Japanese translations of PCT publication No. 2004-51850 (and corresponding US Pat. No. 6,611,316), two reticle patterns are synthesized on a substrate via a projection optical system. The present invention can also be applied to an exposure apparatus that performs double exposure of one shot area on a substrate almost simultaneously by one scanning exposure. Furthermore, the present invention can also be applied to the case where exposure is performed with a projection exposure apparatus that uses extreme ultraviolet light (EUV light) having a wavelength of about several nm to 100 nm as exposure light. When EUV light is used, the mask is a reflection type, and an illumination system composed of a reflective optical member is used for illuminating the mask pattern, and a projection system composed of a reflective optical member is used to project the pattern. .

  In the above-described embodiment, a mask (reticle) on which a transfer pattern is formed is used. Instead of this mask, for example, as disclosed in US Pat. No. 6,778,257. An electronic mask that forms a transmission pattern or a reflection pattern based on electronic data of a pattern to be exposed may be used. This electronic mask is also called a variable shaping mask, and includes, for example, a DMD (Digital Micro-mirror Device) which is a kind of non-light emitting image display element (spatial light modulator).

  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, and various devices such as DNA chips can be widely applied. Furthermore, the present invention can also be applied to a manufacturing process when manufacturing a mask (photomask, reticle, etc.) on which mask patterns of various devices are formed using a photolithography process.

  In addition, the illumination optical system and projection optical system composed of a plurality of lenses are incorporated into the exposure apparatus main body for optical adjustment, and a reticle stage and wafer stage consisting of a large number of mechanical parts are attached to the exposure apparatus main body for wiring and piping. The exposure apparatus of the above-described embodiment can be manufactured by connecting and further performing general adjustment (electric adjustment, operation check, etc.). The exposure apparatus is preferably manufactured in a clean room where the temperature, cleanliness, etc. are controlled.

  In addition, this invention is not limited to the above-mentioned embodiment, Of course, a various structure can be taken in the range which does not deviate from the summary of this invention.

It is a figure which shows the structure of the exposure apparatus of an example of embodiment of this invention. (A) is an enlarged view showing an example of a reticle pattern, (B) is an enlarged view showing another example of a reticle pattern, (C) is a view showing a secondary light source during dipole illumination, and (D) is FIG. The figure which shows the secondary light source at the time of 4 pole illumination, (E) is a figure which shows another secondary light source at the time of 2 pole illumination. 2A is an enlarged view showing a part of a light beam generated from the pattern of FIG. 2A and incident on the wafer W, FIG. 3B is a diagram showing an intensity distribution SX by the light beam of FIG. ) Is a diagram showing a light beam incident on the wafer W and reflected light from the wafer W, and (D) is a diagram showing an intensity distribution SZ of a standing wave formed by the light beam of FIG. (A) is a figure which shows the intensity distribution in the resist layer of the wafer W by a contour line, (B) is a figure which shows a part of light beam in the resist layer of the wafer W, (C) is a resist pattern formed after development. It is an enlarged view which shows an example of a cross-sectional shape. (A), (B), and (C) are enlarged views showing an example of changes in the cross-sectional shape of the resist pattern when the substrate reflectance is gradually increased. (A) is a figure which shows an example of the result of having calculated the minimum line width of the resist pattern after image development with respect to the substrate reflectance under a plurality of illumination conditions, and (B) is the contrast of the projected image. It is a figure which shows an example of the result of having calculated the minimum line | wire width of the resist pattern after image development with respect to the substrate reflectivity by making small gradually. It is a figure which shows an example of the result of having calculated the minimum line | wire width of the resist pattern after image development with respect to a substrate reflectance by changing the exposure amount with respect to a wafer. It is a flowchart which shows an example of the exposure operation | movement in embodiment. (A), (B), (C), and (D) are diagrams showing examples of changes in contrast of a projected image due to focus fluctuation, image vibration, polarization degree, and effective flare, respectively. It is a figure which shows an example of the change of the contrast of a projection image at the time of changing image vibration (X-MSD) and a focus fluctuation | variation. (A) is a figure which shows an example of the pattern in which an L & S pattern and a line pattern are mixed, (B) is a figure which shows the image of the pattern of FIG. 11 (A). It is a figure which shows an example of the result of having calculated the contrast ratio of a standing wave and the image of a reticle pattern with respect to a board | substrate reflectance on several illumination conditions.

Explanation of symbols

  R ... reticle, PL ... projection optical system, W ... wafer, PR ... resist, ILS ... illumination optical system, 6 ... polarization optical system, 7A-7C ... diffractive optical element, 20 ... main control system, 21 ... illumination control system, 22 ... Simulator, 22a, 22b, 22c ... Calculation unit, 30 ... Nozzle unit, 41X, 41Y ... Line and space pattern (L & S pattern), 42A, 42B, 42E, 42F ... Secondary light source, 47, 47A-47C ... Resist pattern, 100 ... Exposure device

Claims (19)

A projection image evaluation method for evaluating a cross-sectional shape of an image formed on a photosensitive layer on a substrate after development,
Obtaining contrast information of intensity distribution in the direction along the surface of the photosensitive layer of exposure light when exposing the photosensitive layer;
Finding standing wave information in the photosensitive layer from the reflectance of the substrate,
A projection image evaluation method, comprising: obtaining line width information of an image formed on the photosensitive layer after development based on the contrast information and the standing wave information.   The projection image evaluation method according to claim 1, wherein when obtaining the line width information, a plurality of exposure amounts for the photosensitive layer are set. The photosensitive layer of the substrate is exposed with the exposure light from an illumination system through a predetermined pattern and a projection system,
When obtaining the contrast information when exposing the photosensitive layer, the intensity distribution of the exposure light on the pupil plane of the illumination system, the aberration of the projection system, and the defocus of the photosensitive layer from the image plane of the projection system The projection image evaluation method according to claim 1, wherein at least one piece of information is used. The pattern formed on the photosensitive layer includes a line and space pattern,
When obtaining the line width information of an image formed after development on the photosensitive layer, the line width of the line portion of the line and space pattern in the dark portion of the standing wave is a predetermined line width, The projection image evaluation method according to claim 1, wherein a line width of the line part in a bright part of a standing wave is obtained. The line and space pattern is arranged close to a line pattern having a line width wider than the line part,
The contrast information of the image of the line-and-space pattern is obtained using an average value of the light amount of the space part at both ends of the line part closest to the line pattern and the light quantity of the line part. Item 5. The projected image evaluation method according to Item 4.   6. The projection image evaluation method according to claim 1, wherein when exposing the photosensitive layer, a liquid that transmits the exposure light is supplied onto the photosensitive layer. 7. In the exposure method of exposing the photosensitive layer on the substrate with exposure light,
Setting exposure conditions for the photosensitive layer;
Using the projection image evaluation method according to any one of claims 1 to 6, obtaining line width information of an image formed on the photosensitive layer after development under the set exposure conditions;
A step of changing the set exposure condition based on the obtained line width information. Obtaining a minimum line width of the image in the step of obtaining the line width information;
8. The exposure method according to claim 7, wherein the exposure condition is changed so that the determined minimum line width is equal to or greater than a predetermined allowable range. An exposure apparatus management method for exposing a photosensitive layer on a substrate with exposure light,
Setting exposure conditions for the photosensitive layer in the exposure apparatus;
Using the projected image evaluation method according to any one of claims 1 to 6, obtain line width information of an image formed on the photosensitive layer after development under the set exposure conditions,
An exposure apparatus management method, comprising: evaluating an exposure result by the exposure apparatus based on the obtained line width information.   10. The exposure apparatus management method according to claim 9, wherein the set exposure condition is changed based on the evaluation of the exposure result. A projection image evaluation apparatus for evaluating a cross-sectional shape of an image formed after development on a photosensitive layer on a substrate,
A first calculation unit for obtaining contrast information of intensity distribution in a direction along the surface of the photosensitive layer of exposure light when exposing the photosensitive layer;
A second calculation unit for obtaining standing wave information in the photosensitive layer from the reflectance of the substrate;
A third arithmetic unit that obtains line width information of an image formed on the photosensitive layer after development using the contrast information obtained by the first arithmetic unit and the standing wave information obtained by the second arithmetic unit. When,
A projection image evaluation apparatus comprising:   The projection image evaluation apparatus according to claim 11, wherein the third calculation unit sets a plurality of exposure amounts for the photosensitive layer when obtaining the line width information. The photosensitive layer of the substrate is exposed with the exposure light from an illumination system through a predetermined pattern and a projection system,
The first calculation unit includes:
When obtaining the contrast information when exposing the photosensitive layer, the intensity distribution of the exposure light on the pupil plane of the illumination system, the aberration of the projection system, and the defocus of the photosensitive layer from the image plane of the projection system The projection image evaluation apparatus according to claim 11, wherein at least one piece of information is used. The pattern formed on the photosensitive layer includes a line and space pattern,
The third calculation unit includes:
When obtaining the line width information of an image formed after development on the photosensitive layer, the line width of the line portion of the line and space pattern in the dark portion of the standing wave is a predetermined line width, The projection image evaluation apparatus according to claim 11, wherein a line width of the line portion in a bright portion of a standing wave is obtained. The line and space pattern is arranged close to a line pattern having a line width wider than the line part,
The first calculation unit uses the average value of the light amount of the space part at both ends of the line part closest to the line pattern, and the light quantity of the line part, as contrast information of the image of the line and space pattern. The projection image evaluation apparatus according to claim 14, wherein the projection image evaluation apparatus is obtained.   16. The projection image evaluation apparatus according to claim 11, wherein when exposing the photosensitive layer, a liquid that transmits the exposure light is supplied onto the photosensitive layer. In an exposure apparatus that exposes a photosensitive layer on a substrate with exposure light,
A projection image evaluation apparatus according to any one of claims 11 to 16,
A setting unit for setting exposure conditions for the photosensitive layer;
A control unit for changing the set exposure condition based on line width information of an image formed on the photosensitive layer after development obtained by the projection image evaluation apparatus under the set exposure condition;
An exposure apparatus comprising: The projection image evaluation apparatus obtains a minimum line width of the image;
The exposure apparatus according to claim 17, wherein the control unit changes the exposure condition so that the determined minimum line width is equal to or greater than a predetermined allowable range. Exposing the photosensitive layer on the substrate using the exposure apparatus according to claim 17 or 18,
Developing the exposed photosensitive layer.

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