JP2008124308A - Exposure method and exposure apparatus, and device manufacturing method using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure method and an exposure apparatus, by which the plurality of parameters are calculated with a simulation technology and a targeted pattern image is formed on a wafer front surface. <P>SOLUTION: The exposure method comprises the steps of: measuring a light amount distribution of a quadratic light source image; calculating a center position of the distribution and the light amount distribution in each region partitioned by lines passing through the center position; computing differences between the targeted pattern image and an image projected on a substrate at the time of carrying out an exposure with the light amount distribution of the quadratic light source image by using information of the center position and the light amount distribution; establishing a target position of the center position and a target value of the light amount distribution; and adjusting the center position and the light amount distribution based on the target position and the target value. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention generally relates to an exposure method, an exposure apparatus, and a device manufacturing method using the same.

  Until now, various techniques have been used to improve the resolution of a pattern formed on a wafer. One of them is a modified illumination technique. In the modified illumination technique, light is incident obliquely on a mask (reticle), and either the + 1st order diffracted light or the −1st order diffracted light of the mask pattern and the 0th order diffracted light are combined with the pupil plane of the projection optical system. This is a technique for forming an image with two light beams. Deformed illumination refers to a secondary light source other than a single circular shape by using a special optical element for a light beam from a light source, instead of a single circular secondary light source based on a light beam from a commonly used light source. Means lighting. Examples of modified illumination include annular illumination, dipole illumination, and quadrupole illumination. Here, the illuminance distribution of the secondary light source based on the light flux from the light source corresponds to the angular distribution of the light incident on the mask surface.

  When a so-called Koehler illumination optical system is assembled, the pupil plane of the projection optical system becomes an optically conjugate plane with the pupil plane of the illumination optical system, and a secondary light source image is formed on the pupil plane of the projection optical system.

  Note that various optical elements such as prisms are configured in the illumination optical system, and various types of modified illumination can be achieved by changing the types of these optical elements or changing the shape of the configured diaphragm. Is obtained. The size of the illuminance distribution of the secondary light source based on the light flux from the light source can be changed by adjusting the position of the optical element.

  When a mask pattern is formed on a substrate, an illuminance distribution of a secondary light source suitable for target imaging performance is required. Thus, for example, in the case of annular illumination, it is known to change the annular ratio or change the shape of the illuminance distribution of the secondary light source (see Patent Document 1). In the invention described in Patent Document 1, the light amount distribution of the secondary light source image is measured, and when the secondary light source obtained from the measurement is used, the line width variation of the image projected on the wafer and the exposure process margin Is calculated by simulation. Then, based on the calculation result, the optical element of the illumination optical system is selected or set, and the annular ratio and the shape of the secondary light source are adjusted.

  On the other hand, in a plurality of exposure apparatuses, there are machine differences due to processing errors, for example, decentration and performance of the antireflection film, in the optical elements constituting the illumination optical system. For this reason, in the illuminance distribution of the secondary light source, there may be a shift in position between the center position of the secondary light source and the optical axis of the projection optical system. This positional deviation is caused by the deviation between the position of the image formed on the wafer and the position of the target image when the wafer surface is defocused with respect to the image plane position of the projection optical system, and the target line width. Appears as a difference in line width. Therefore, attempts have been made to improve the positional deviation between the center position and the optical axis of the projection optical system (see Patent Document 2).

  In the invention described in Patent Document 2, in the exposure apparatus, a shift in the center position of the secondary light source shape, that is, a so-called eccentricity is detected by a detector. Then, based on the detection result, the optical element of the illumination optical system is driven two-dimensionally along the optical axis direction of the illumination optical system and a plane perpendicular to the optical axis to reduce the shift amount of the center position. Yes.

In addition, non-uniformity in the light amount distribution of the secondary light source in the exposure apparatus may occur. This non-uniformity appears as a difference in the imaging line width of the pattern at the time of defocusing as described above. For this reason, attempts have been made to improve the non-uniformity (see Patent Document 3). In the invention described in Patent Document 3, the amount of deviation (eccentricity) of the center position of the secondary light source shape is detected by a detector. Then, the secondary light source formation surface is divided into a plurality of lines along the line passing through the center position, and the light quantity integrated value is calculated by integrating the light quantity in each region. Based on the calculated value, the light amount distribution in each region is adjusted using a correction filter so that the integrated light amount value is uniform among the plurality of regions.
JP 2005-228846 A Japanese Patent Laid-Open No. 11-87232 JP 2005-322855 A

  As described above, the conventional technique discloses an image improvement method and a technique for setting an optical system to an ideal state.

  However, in order to actually form a desired pattern on the substrate surface, it becomes a problem how to combine the plurality of parameters such as the shape of the secondary light source and the light quantity distribution of the secondary light source to realize the exposure process.

  Accordingly, an object of the present invention is to provide an exposure method and an exposure apparatus for deriving the plurality of parameters by a simulation technique and forming a target pattern image on a substrate surface.

In order to solve the above-described problems, an exposure method according to one aspect of the present invention includes: forming a secondary light source with light from a light source; illuminating a mask with light from the secondary light source; In an exposure method for projecting an image of the mask pattern onto a substrate,
The measurement step of measuring the light amount distribution of the image of the secondary light source, and the light amount distribution of the secondary light source image measured in the measurement step, divided by the center position of the secondary light source image and a line passing through the center position A calculation step for calculating a light amount distribution in each region in the pupil plane of the projected optical system, and information on the center position calculated in the calculation step and the light amount distribution in each region, A calculation step for calculating a difference between the pattern image to be projected and an image projected on the substrate by the light amount distribution, and based on a calculation result in the calculation step, a target position of the center position and a light amount distribution in each region A setting step for setting a target value, and based on the target position and the target value set in the setting step, the center position and each area Kicking and an adjustment step of adjusting a light amount distribution, characterized by projecting the image of the pattern of the mask in the light amount distribution of the secondary light source image that has been adjusted in the adjusting step on the substrate.

  An exposure apparatus according to another aspect of the present invention includes an illumination optical system that illuminates a mask with light from a light source, a projection optical system that projects an image of the pattern of the mask onto a substrate, and a light source from the light source. A measuring device for measuring the light amount distribution of the secondary light source image based on the luminous flux, and dividing the light amount distribution of the secondary light source image measured by the measuring device by a line passing through the center position of the secondary light source image and the center position. And calculating the light amount distribution in each region, and using the calculated center position and information on the light amount distribution in each region, a target pattern image and an image projected on the substrate by the light amount distribution, Calculating means for calculating a difference between the target position of the center position and a target value of the light amount distribution in each region based on the calculation result, and the illumination optics based on the target position and the target value Optical elements And having an actuator for moving the.

  According to the present invention, a target pattern image can be projected onto a wafer with higher imaging performance.

  Preferred embodiments of the present invention will be described below with reference to the drawings.

  FIG. 1 shows an exposure apparatus to which the present invention can be applied. The exposure apparatus includes a light source 1, an illumination optical system 400, and a projection optical system 14. The light source 1 is an ultrahigh pressure mercury lamp or an excimer laser that oscillates light in the ultraviolet region or the far ultraviolet region. The light emitted from the light source 1 is converted into a desired light beam shape by the shaping optical system 2, and condensed by the condensing optical system 3 in the vicinity of the incident surface of the optical rod 4.

  The condensing zoom lens 5 images the illuminance distribution (light intensity distribution) in the vicinity of the exit surface 4 b of the optical rod 4 on the incident surface 6 a of the fly-eye lens 6 at a predetermined magnification. The exit surface 4b of the optical rod 4 and the entrance surface 6a of the fly-eye lens 6 are substantially conjugate to each other. Further, by using the condenser zoom lens 5 as a zoom lens having a variable magnification, it is possible to adjust a light flux region incident on the fly-eye lens 6 and to form various illuminance distributions.

  The fly-eye lens 6 has a configuration in which a plurality of minute lenses are two-dimensionally arranged, and the vicinity of the exit surface 6b corresponds to the pupil plane of the illumination optical system. Here, instead of the fly-eye lens 6, two sets of cylindrical lens arrays may be used.

  A diaphragm member 7 is disposed on the pupil plane of the illumination optical system in order to shield unnecessary light and achieve a desired illuminance distribution. The aperture member 7 has a variable aperture size and shape by an aperture drive mechanism (not shown).

  The irradiation lens 8 superimposes and illuminates the pupil surface illuminance distribution formed near the exit surface 6 b of the fly-eye lens 6 on the field stop 9. The field stop 9 is composed of a plurality of movable light shielding plates, and limits the exposure range on the mask (reticle) 13 surface and the wafer 15 surface, which are irradiated surfaces, so as to form an arbitrary opening shape. Reference numerals 10 and 11 denote imaging lenses, which form an image of the aperture shape of the field stop 9 on a mask 13 that is an irradiated surface. Reference numeral 12 denotes a deflection mirror.

  The mask 13 is held by a mask stage 17, and the mask stage 17 is driven and controlled by a mask stage driving device (not shown).

  The projection optical system 14 projects the circuit pattern of the mask illuminated with the illuminance distribution formed by the illumination optical system 400 onto the wafer 15 that is a substrate.

  The wafer 15 is held on the wafer stage 18, and the wafer stage 18 moves two-dimensionally along the optical axis direction of the projection optical system and a plane orthogonal to the optical axis. The wafer stage 18 is driven and controlled by a wafer stage driving device (not shown).

  The two-dimensional image sensor 16 that is a measuring instrument (measuring instrument) measures (measures) the amount of light incident on the wafer 15. For example, a CCD can be used as a two-dimensional image sensor. The two-dimensional image sensor 16 moves with the driving of the wafer stage 18 and receives illumination light in the irradiation region. Then, the two-dimensional image sensor 16 transmits a signal corresponding to the received light to the control device 21 described later.

  Reference numerals 19 and 20 denote illumination light generating means, which have optical elements for forming annular illumination or quadrupole illumination from the light flux from the optical rod 4.

  Here, the illumination optical system 400 is composed of an optical system subsequent to the shaping optical system 2 and extending from the imaging lens 11 to the preceding stage.

  Further, the condensing optical system 3 and the optical rod 4 are referred to as a first optical unit 100, the illumination light generation means 19 and 20 are referred to as a second optical unit 200, and the condensing zoom lens 5 is referred to as a third optical unit 300. The light quantity distribution (light intensity distribution) formed by the first optical unit 100 is the first light quantity distribution A, and the light quantity distribution (light intensity distribution) formed by the second optical unit 200 is the second light quantity distribution B. To do.

  The first to third optical units convert the light flux from the light source into a desired shape, and adjust the light intensity distribution of the light flux incident on the fly-eye lens 6 at the subsequent stage, whereby the light quantity distribution on the pupil plane of the illumination optical system The (pupil plane distribution C) can be adjusted. The light emitting surface on the pupil plane or the light itself is a secondary light source.

  Next, the second optical unit 200 will be described in detail. As shown in FIG. 2 (a), when forming an annular illumination that is well known in the art (annular illumination), the illumination light generating means 19 and 20 receive light as shown in FIG. 2 (b). A prism having a concave conical surface (or a flat surface) on the side and a convex conical surface on the light exit side may be used.

  Further, in order to form so-called quadrupole illumination as shown in FIG. 3A, the illumination light generating means 19 and 20 are provided with concave four on the light incident side as shown in FIG. A prism having a pyramid (or a plane) and a convex quadrangular pyramid on the light exit side may be used. At this time, the angle formed by the ridgeline of the quadrangular pyramid on the entrance surface and the exit surface and the optical axis of the illumination optical system may be equal, and in order to improve illumination efficiency, the angles on the entrance side and the exit side are made different. (A conical prism may be used as well).

  Furthermore, if the illumination light generating means 19 and 20 are constituted by a pair of prisms as shown in FIGS. 4A and 5A and they can be moved relative to each other in the optical axis direction, more redundant. It becomes possible to realize the light quantity distribution of the secondary light source. Here, the light quantity distribution of the secondary light source corresponds to the angular distribution of the exposure light incident on the mask 13 surface, and determines the light quantity distribution of the secondary light source image formed on the pupil plane 14a of the projection optical system. Here, the pupil plane 14a of the projection optical system is a plane optically conjugate with the pupil plane of the illumination optical system. That is, the light quantity distribution of the secondary light source is reflected in the secondary light source image on the pupil plane of the projection optical system.

  If the interval between the prisms is reduced as shown in FIG. 4A, the light quantity distribution of the annular secondary light source with a large width of the light emitting part as shown in FIG. 4B is realized. On the other hand, if the interval between the prisms is increased as shown in FIG. 5A, the light quantity distribution of the annular secondary light source having a small width of the light emitting portion as shown in FIG. 5B is realized.

  Thus, since the light quantity distribution of the secondary light source can be changed, an appropriate illuminance distribution may be formed according to the mask pattern.

  Further, when combined with the subsequent condenser zoom lens 5, the size (σ value) of the secondary light source shape can be adjusted while maintaining the annular ratio. Here, the σ value is a value obtained by dividing the exit-side numerical aperture of the illumination optical system by the incident-side numerical aperture of the projection optical system.

  When forming the illuminance distribution of the annular secondary light source as shown in FIG. 2A, the first optical unit 100 sets the first light amount distribution A to a circular shape, and the second optical unit 200 sets the second light amount distribution. Let B be an annular shape. Then, by driving the optical element in the optical unit 200, the ratio of the outer diameter and the inner diameter of the annular zone (ring zone ratio) is adjusted. Furthermore, when combined with the third optical unit 300, the size (σ value) of the secondary light source shape can be adjusted while maintaining the annular ratio of the second light quantity distribution.

  Next, the exposure method in the first embodiment of the present invention will be described with reference to FIGS. As shown in FIG. 6, first, in S1, the light quantity distribution of the secondary light source image formed on the pupil plane of the projection optical system is measured (measured). FIG. 7 shows a measuring apparatus that measures the in-plane light quantity of the secondary light source image formed on the pupil plane of the projection optical system. In FIG. 7, the deflecting mirror 12 is omitted in order to simplify the description.

  First, the field stop 9 is driven and set so that the minute aperture is positioned on the optical axis of the projection optical system 14. Then, the light emitted from the light source 1 is incident on the opening, and the light passing through the opening is transmitted through the imaging lenses 10 and 11. The mask 13 is moved so as not to block the light, and the light transmitted through the imaging lenses 10 and 11 enters the projection optical system 14 and is condensed on a reference plane (focal position) indicated by a dotted line. That is, only the light that has passed through the aperture of the field stop 9 once forms an image on the reference plane and enters the two-dimensional image sensor 16 while reflecting the incident angle. The light receiving surface of the two-dimensional image sensor 16 is disposed below the reference surface in the optical axis direction (Z direction in the drawing). By doing so, the light quantity of each pixel can be plotted two-dimensionally, and the light quantity distribution of the secondary light source image formed on the pupil plane of the projection optical system can be measured.

  The two-dimensional image sensor 16 is disposed on an XY stage 18 that holds the wafer 15. When it is desired to measure the amount of light in the secondary light source image at a point other than the optical axis of the projection optical system 14, a small aperture of the field stop 9 is set at the point to be measured and the position of the two-dimensional image sensor 16 is set. The XY stage 18 is moved in the horizontal direction so that the measurement position is reached. By doing so, it is possible to measure the light amount of the secondary light source image at a plurality of positions (each image height) at different distances from the optical axis of the projection optical system.

  A line sensor may be used instead of the two-dimensional image sensor 16. Further, a pinhole having a sufficiently small diameter with respect to the spread of the light beam is provided above the light receiving surface of the two-dimensional image sensor 16 without providing a small aperture in the field stop 9, and a pinhole is disposed at the focal position. Measurement may be performed.

  As another method for measuring the light amount distribution at each position (image height) of the secondary light source image, a minute aperture may be provided at a position conjugate with the field stop 9 as shown in FIG. Specifically, the field stop 9 is opened, and a mask 13 or a plate in which a minute opening is formed by a Cr pattern or the like is disposed.

  The light quantity distribution of the secondary light source image at a certain position is measured by the method as described above, and the other positions can be similarly measured by moving the XY stage 18 to the position to be measured. Therefore, by measuring at an arbitrary position of the mask 13 provided with a minute opening, it is possible to measure the light amount distribution of the secondary light source image at a position (image height) corresponding to the distance from the optical axis of the projection optical system 14. .

  Next, as shown in FIG. 6, in S2, a center position of the secondary light source image and a light amount distribution (light intensity distribution) to be described later are calculated from the measured light amount distribution of the secondary light source image. Here, the light amount distribution and the light intensity distribution are used to represent the same optical performance. The calculation method will be described with reference to FIG. In the case of dipole illumination, assuming that the shape is a part of a ring, an outer outline or an inner outline is specified, and the center point of the ring is set as the center position of the secondary light source image. Similarly, in the case of quadrupole illumination, assuming that the shape of the secondary light source image is a part of the ring, the outer contour or the inner contour is specified, and the center of the ring is set to the center position of the secondary light source image. And In the case of annular illumination, the center of the ring is set as the center position of the secondary light source image.

  After determining the center position of the secondary light source image, the light amount distribution in each region in the pupil plane of the projection optical system divided by the line passing through the center position is calculated. As shown in FIGS. 9A and 9A, 9B and 9B, in the case of quadrupole illumination, two lines that are orthogonal to each other through the center position obtained as described above. The measurement area is divided into four areas. The measurement area is represented by a rectangle in the outer frame of FIG. Then, the light amount distribution in each region is calculated. Then, the light quantity distribution is compared between the areas, and the uniformity of the light quantity distribution is determined. In the case of dipole illumination, as shown in FIGS. 9C and 9C and FIGS. 9D and 9D, two measurement areas are formed by a line passing through the center position of the secondary light source image. To determine the uniformity. In the case of annular illumination, four divided regions as shown in FIGS. 9 (e) and 9 (e '), FIG. 9 (a), or FIG. 9 (b) are used.

  The uniformity index will be described with reference to FIG. First, an integrated value S1 obtained by integrating the light amount in the region 1 over the region and an integrated value S2 obtained by integrating the light amount in the region 2 over the region are obtained. Then, the difference between S1 and S2 is divided by the sum of S1 and S2 to obtain a uniformity index. Based on this value, a simulation described later is performed. However, any index of uniformity may be used as long as it shows variation in the light amount distribution between the regions.

  Next, in S3 of FIG. 6, in the exposure apparatus of the present embodiment, the mask pattern is projected onto the wafer 15 when the mask pattern is projected onto the wafer 15 with the measured light amount distribution (light intensity distribution) of the secondary light source. Calculate the image to be performed (simulation). In S4, the difference between the image obtained by the simulation and the target pattern image is calculated by comparison with the target pattern image. Here, this difference appears as a positional deviation or a line width difference between the image formed on the wafer 15 and the target pattern image at the time of defocusing.

  The above-described positional shift and line width difference will be described with reference to FIG. First, an image (target pattern image) to be projected on the wafer 15 is determined. Here, it is assumed that the pattern 52 of three lines is a target pattern image. For the target pattern image, the mask pattern is a rectangular pattern such as pattern 51. When the pattern 51 is projected onto the wafer 15 in a state where there is no defocus, the corners are rounded and the target pattern image is 52. However, when the pattern 51 is actually exposed, an image like 53 is projected on the wafer 15 due to the influence of defocusing. Therefore, the deviation (arrow 56 in the figure) between the center line of the line 531 of the image 53 projected on the wafer 15 and the center line of the line 521 (line corresponding to the line 531) of the target pattern image 52 is described above. This is a misalignment. Further, the difference between the line width 55 of the line 532 of the image 53 projected on the wafer 15 and the line width 54 of the line 522 (line corresponding to the line 532) of the target pattern image 52 is the above-mentioned line width. Difference.

  Here, in the above simulation, the calculation may be performed in consideration of the characteristics of the resist applied on the wafer 15. That is, the resist is exposed to a pattern projected on the wafer 15 and developed to calculate a pattern to be formed, and the pattern is compared with the target pattern to obtain a positional shift and a line width difference. May be.

  Next, in response to the calculation result of S4, the target position is set for the center position of the light quantity distribution of the secondary light source in S5. In addition, a target value of the light quantity distribution in each region of the light quantity distribution of the secondary light source is set. In setting the target position and the target value of the light quantity distribution, the above-described positional deviation and line width difference are set to be minimum.

  In step S6, the center position of the light quantity distribution of the secondary light source and the light quantity distribution in each area are adjusted based on the target position regarding the center position of the light quantity distribution of the secondary light source and the target value of the light quantity distribution in each area. Finally, a mask pattern image is projected onto the wafer 15 using the light quantity distribution of the secondary light source adjusted in S6 (S7).

  In S1, when the light amount distribution of the secondary light source image is measured at a plurality of positions according to the distance from the optical axis of the projection optical system, the above-described positional deviation and line width difference at the plurality of positions are obtained. Then, the target position for the center position of the light quantity distribution of the secondary light source and the target value of the light quantity distribution in each area are summed up so that the positional deviation and line width difference at the plurality of positions are totaled and the value is minimized. Set and adjust.

  Next, the flow of data from measurement to adjustment of the light amount distribution of the secondary light source image will be described. A signal corresponding to the light amount distribution of the secondary light source image measured by the two-dimensional image sensor 16 is sent to the control device 21. Then, in the calculation unit which is a calculation means in the control device 21, the center position of the secondary light source and the light amount distribution in each region are calculated from the signal, and the mask pattern is changed to the wafer 15 using the light amount distribution of the secondary light source. The amount of positional deviation and the line width difference of the image projected on the screen are calculated. Further, the center position of the secondary light source to be targeted and the light quantity distribution in each of the above areas are obtained from the positional deviation amount and the line width of the image. Then, the control device 21 controls the positions of the actuators 22, 23, and 24 that drive the optical elements so that the light amount distribution of the secondary light source approaches the target value calculated by the calculation unit. The optical elements to be driven are illumination light generation means 19 and 20 such as an optical rod 4, a condensing zoom lens 5 and a prism, which are arranged so as to be driven in the direction of the optical axis and the direction perpendicular to the optical axis. Controlled to an appropriate position.

  Next, adjustment of the center position of the secondary light source shape and the light amount distribution in each region will be described with reference to FIGS. As shown in state X in FIG. 11, the optical prism 19 is decentered due to causes such as component tolerance, assembly tolerance, and drive tolerance. Therefore, as shown in the state X of FIG. 10, the center position of the secondary light source shape is shifted from the optical axis, and the light amount distribution in each region is not uniform. Therefore, when the optical rod 4 is moved in a direction perpendicular to the optical axis as in the state Y in FIG. 11, the uniformity of the light intensity distribution can be adjusted from the state X to the state Y in FIG. Further, when the condenser zoom lens 5 is moved in the direction perpendicular to the optical axis as in the state Z in FIG. 11, the center position of the secondary light source shape can be adjusted from the state Y to the state Z in FIG. it can.

  According to the exposure method of the present embodiment, the above-described positional deviation and line width difference are small for any mask pattern, and a target pattern image can be projected onto the wafer with higher accuracy. This is because the target pattern image and the image projected onto the wafer are compared, and the center position of the light amount distribution of the secondary light source and the light amount distribution in each region are adjusted independently.

  Next, an exposure method in the second embodiment of the present invention will be described with reference to FIG. Description of the same parts as those of the first embodiment is omitted. In the second embodiment, the difference from the first embodiment is that the position difference between the image projected on the wafer 15 and the target pattern image is measured before measuring the light quantity distribution of the secondary light source image. The difference between the line widths is to be calculated. Then, the calculated value is stored as data. Here, the image projected onto the wafer 15 is calculated by shifting the center position of the secondary light source image from the optical axis of the projection optical system. In addition, when the light intensity distribution in each region shown in FIG. 9 is not equal among a plurality of regions, the positional deviation and the line width difference between the image projected on the wafer 15 and the target pattern image are calculated. Calculate and store as data.

  In S21 in FIG. 12, the deviation between the center position of the secondary light source image and the optical axis of the projection optical system, and the variation (non-uniformity) in the light amount (light intensity) distribution in each region described in FIG. An image projected on the wafer 15 is calculated by simulation. In S22, the difference between the image calculated by the simulation and the target pattern image is calculated. Here, this difference appears as a positional deviation or a line width difference between the image formed on the wafer 15 and the target pattern image at the time of defocusing. Therefore, the image positional deviation and the line width difference when defocusing is 1 μm are calculated. Then, for the unit amount of deviation between the center position of the secondary light source image and the optical axis of the projection optical system, the image position deviation and the line width difference are obtained. The value obtained in this way is called sensitivity, and is referred to as first information here. In addition, as for the unit amount of variation in the light amount distribution in each region, an image position shift and a line width difference are obtained. The obtained value is set as the second information. Here, the first information is the sensitivity due to the shift of the center position, and the second information is the sensitivity due to the nonuniformity.

  This will be specifically described below. Here, in order to simplify the description, the positional deviation between the target pattern image and the image projected on the wafer 15 when exposed with the light amount distribution of the set secondary light source will be described. For example, as shown in FIG. 13A, when the center position of the distribution of the secondary light source image coincides with the optical axis of the projection optical system, and the light quantity distribution is uniform among the regions, the defocus amount of 1 μm. Let u be the image displacement. Then, as shown in FIG. 13B, when the center position of the distribution of the secondary light source image is shifted by 0.02σ from the optical axis of the projection optical system, the positional deviation of the image per 1 μm defocus is obtained. v. Here, 0.02σ indicates a value obtained by multiplying the above σ value by 0.02 (2% of the σ value).

  Finally, the value is calculated by dividing the obtained difference between u and v by 0.02σ. This value represents the positional deviation of the image per defocus of 1 μm when the central position of the distribution of the secondary light source image is shifted by the unit length σ from the optical axis of the projection optical system. This is called sensitivity due to the shift of the center position.

  Next, the sensitivity due to nonuniformity will be described. As shown in FIG. 14A, when the integrated value of the light amount in the region A1 is larger than the integrated value of the light amount in the region A2, the positional deviation of the pattern is set to v ′ with respect to the defocus amount of 1 μm. Then, the difference between v ′ and the previously obtained u is divided by the difference between the integrated value of the light amount in the region A1 and the integrated value of the light amount in the region A2, and the sensitivity due to the nonuniformity is determined. Here, the uniformity index described above may be used to calculate the sensitivity.

  In S23, the light quantity distribution of the secondary light source image is measured. In S24, the center position of the secondary light source image and the light quantity distribution in each region are obtained. These steps are the same as in the first embodiment.

  Next, using the sensitivity obtained in S22 and the center position and light amount distribution obtained in S24, the image positional deviation and the line width difference when defocused are calculated (S25). For example, in the case of the dipole illumination as shown in FIG. 14B, regarding the positional deviation of the pattern, the sensitivity due to the deviation of the center position is x, and the sensitivity due to the non-uniformity is y. The deviation between the center position of the secondary light source image and the optical axis of the projection optical system is X, and the difference between the integrated value of the light amount in the region A1 and the integrated value of the light amount in the region A2 is Y. In this case, the image positional deviation is a value obtained by adding a value obtained by multiplying x and X by a value obtained by multiplying y and Y.

  In S26, the target position with respect to the center position of the light quantity distribution of the secondary light source and the target value of the light quantity distribution in each region of the light quantity distribution of the secondary light source are set so that the image positional deviation is minimized. For example, it is assumed that a position shift of the image of 10 nm / μm / σ occurs due to a position shift with respect to the center position of the secondary light source image. At this time, if there is non-uniformity in the light amount distribution in each region of the light amount distribution of the secondary light source that causes a displacement of the image of 1 nm / μm, the center position of the secondary light source image is set to −0.1σ. If it is shifted from the optical axis of the projection optical system, the image is not displaced. Here, 1 nm / μm represents a 1 nm position shift caused by 1 μm defocus, and 1 nm / μm / σ represents a 1 nm position shift caused by 1 μm defocus per σ.

  Next, in S27, the light quantity distribution of the secondary light source is adjusted according to the calculated target value. Finally, in S28, a mask pattern image is projected onto the wafer 15 using the light quantity distribution of the secondary light source adjusted in S27.

  According to the present embodiment, since the sensitivity due to the deviation or non-uniformity of the center position is obtained in advance before measuring the light amount distribution of the secondary light source, the target value of the light amount distribution at the center position and each region is set for a short time. Can be calculated with Furthermore, from the measurement of the light amount distribution of the secondary light source image to the adjustment of the light amount distribution of the secondary light source can be performed in a shorter time.

  Hereinafter, an embodiment of a device manufacturing method using the above-described exposure method will be described with reference to FIGS. FIG. 15 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, the manufacture of a semiconductor chip will be described as an example. In S101 (circuit design), the device circuit is designed. In S102 (mask production), a mask on which the designed circuit pattern is formed is produced. In S103 (wafer manufacture), a wafer is manufactured using a material such as silicon. S104 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. S105 (assembly) is referred to as a post-process, and is a process of forming a semiconductor chip using the wafer created in S104, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). In S106 (inspection), inspections such as an operation confirmation test of the semiconductor chip created in S105 are performed. Through these steps, a semiconductor chip is completed and shipped (S107).

  FIG. 16 is a detailed flowchart of the wafer process in S104. In S201 (oxidation), the surface of the wafer is oxidized. In S202 (CVD), an insulating film is formed on the surface of the wafer. In S203 (electrode formation), an electrode is formed on the wafer by vapor deposition or the like. In S204 (ion implantation), ions are implanted into the wafer. In S205 (resist processing), a photosensitive agent is applied to the wafer. In S206 (exposure), using the exposure method described in Example 1 or 2, the circuit pattern of the mask is exposed to the photosensitive agent on the wafer. In S207 (development), the exposed photosensitive agent is developed to form a resist image. In S208 (etching), portions other than the developed resist image are removed. In S209 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.

  According to the device manufacturing method of the present embodiment, it is possible to manufacture a higher quality device than before.

1 is a schematic view of an exposure apparatus according to a first embodiment of the present invention. It is a figure showing the light intensity distribution of a ring-shaped secondary light source. It is a figure showing the light intensity distribution of the secondary light source of a quadrupole. It is a figure showing the means to form the light intensity distribution of the secondary light source with a large annular ratio. It is a figure showing the means to form the light intensity distribution of the secondary light source with a small ring zone ratio. It is a flowchart of the exposure method in 1st Example of this invention. It is a figure which shows the measuring method of the light quantity distribution of a secondary light source image. It is a figure which shows the method of calculating | requiring the center position of a secondary light source image. It is a figure which shows the measurement area | region for calculating | requiring the uniformity of the light intensity distribution of a secondary light source image. It is a figure showing the light intensity distribution of the secondary light source in an adjustment stage. It is a figure showing arrangement | positioning of each optical element in an adjustment stage. It is a flowchart of the exposure method in 2nd Example of this invention. It is a figure which shows the shift | offset | difference of the center position in a secondary light source image. It is a figure which shows the dispersion | variation in the light intensity in a secondary light source image. It is a flowchart which shows a device manufacturing method. It is a flowchart which shows a wafer process. It is a figure showing the difference of position shift and line | wire width.

Explanation of symbols

400 Illumination optical system 14 Projection optical system 16 Two-dimensional image sensor 21 Control device 22 Actuator 23 Actuator 24 Actuator

Claims (8)

In an exposure method of forming a secondary light source with light from a light source, illuminating a mask with a light beam from the secondary light source, and projecting an image of the pattern of the mask onto a substrate via a projection optical system,
A measuring step for measuring a light amount distribution of the image of the secondary light source;
The light amount distribution in each region in the pupil plane of the projection optical system divided from the light amount distribution of the secondary light source image measured in the measurement step by a center position of the secondary light source image and a line passing through the center position. A calculating step for calculating
A calculation step for calculating a difference between a target pattern image and an image projected on the substrate by the light amount distribution using information on the center position calculated in the calculation step and the light amount distribution in each region. When,
A setting step for setting a target position of the center position and a target value of a light amount distribution in each region based on the calculation result in the calculation step;
An adjustment step of adjusting a light amount distribution in the center position and each region based on the target position and the target value set in the setting step,
An exposure method, wherein an image of the mask pattern is projected onto a substrate with a light amount distribution of the secondary light source image adjusted in the adjustment step.   2. The exposure method according to claim 1, wherein in the adjustment step, a light amount distribution in the center position and each region is adjusted independently. Calculating first information for calculating a difference between an image projected on the substrate and a target pattern image when there is a deviation between the center position and the optical axis of the projection optical system;
Second information indicating a difference between an image projected on the substrate and a target pattern image when the light amount distribution is non-uniform among a plurality of regions divided by a line passing through the center position. A calculating step,
Based on the first information and the second information, the target pattern image and the light amount of the secondary light source image having the deviation and the light amount distribution being non-uniform among the plurality of regions The exposure method according to claim 1, wherein a difference from an image projected on the substrate is calculated by distribution. In the measurement step, the light amount distribution of the secondary light source image is measured at a plurality of positions at different distances from the optical axis of the projection optical system,
In the calculation step, a positional shift between a target pattern image at the plurality of positions and an image projected on the substrate by a light amount distribution of the secondary light source image measured in the measurement step is calculated.
2. The exposure method according to claim 1, wherein in the setting step, a target value of a light amount distribution in the target position and each of the regions is set based on a total of the positional deviations in the plurality of positions. In the measurement step, the light amount distribution of the secondary light source image is measured at a plurality of positions at different distances from the optical axis of the projection optical system,
In the calculation step, a difference in line width between a target pattern image at the plurality of positions and an image projected on the substrate by a light amount distribution of a secondary light source image measured in the measurement step is calculated.
2. The exposure method according to claim 1, wherein, in the setting step, a target value of a light amount distribution in the target position and each region is set based on a total of the line width differences at the plurality of positions. .   The exposure method according to claim 1, wherein the target position is deviated from the optical axis of the projection optical system, and a target value of a light amount distribution in each region is different among the plurality of regions.   A device manufacturing method comprising the steps of: exposing the substrate using the exposure method according to any one of claims 1 to 6; and developing the exposed substrate. An illumination optical system that illuminates the mask with light from a light source;
A projection optical system that projects an image of the mask pattern onto the substrate;
A measuring instrument for measuring a light amount distribution of a secondary light source image based on a light flux from the light source;
From the light amount distribution of the secondary light source image measured by the measuring device, the center position of the secondary light source image and the light amount distribution in each region divided by the line passing through the center position are calculated, and the calculated center The difference between the target pattern image and the image projected on the substrate by the light amount distribution is calculated using the position and the light amount distribution information in each region, and the center position is calculated based on the calculation result. A calculation means for calculating a target position and a target value of the light amount distribution in each of the areas;
An exposure apparatus comprising: an actuator that moves an optical element of the illumination optical system based on the target position and the target value.

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