JP2005322855A - Evaluation method and adjusting method of light intensity distribution, lighting optical device, exposure device and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an evaluation method for quantitatively and high precision evaluating the symmetry uniformity of light intensity distribution formed on a lighting pupil face of a lighting optical device, for example. <P>SOLUTION: The method includes a setting process (S2) for setting a first division region and a second division region, which are almost symmetrical on a division line, passing a center point of light intensity distribution in the region of light intensity distribution; a calculating process (S3) for calculating a first light intensity calculation value, obtained by integrating light intensity distribution in the first division region for the first division region; and a second light intensity calculation value obtained by integrating light intensity distribution in the second division region for the second division region; and a deciding process (S4) judging symmetrical uniformity on the division line of light intensity distribution, based on the first light intensity calculated value and the second light intensity calculation value. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a light intensity distribution evaluation method, adjustment method, illumination optical apparatus, exposure apparatus, and exposure method. More specifically, the present invention is formed on an illumination pupil plane of an illumination optical apparatus mounted on an exposure apparatus for manufacturing a microdevice such as a semiconductor element, an image sensor, a liquid crystal display element, and a thin film magnetic head in a lithography process. The present invention relates to evaluation and adjustment of light intensity distribution.

  In a typical exposure apparatus of this type, a light beam emitted from a light source passes through a fly-eye lens (or microlens array) as an optical integrator, and a secondary light source as a substantial surface light source composed of a number of light sources. A light source (generally a predetermined light intensity distribution on the illumination pupil plane) is formed. The light beam from the secondary light source is limited through an aperture stop disposed in the vicinity of the rear focal plane of the fly-eye lens, and then enters the condenser lens.

  The light beam condensed by the condenser lens illuminates the mask on which a predetermined pattern is formed in a superimposed manner. The light transmitted through the mask pattern forms an image on the wafer via the projection optical system. Thus, the mask pattern is projected and exposed (transferred) onto the wafer. The pattern formed on the mask is highly integrated, and it is essential to obtain a uniform illuminance distribution on the wafer in order to accurately transfer this fine pattern onto the wafer.

  Therefore, a circular secondary light source is formed on the rear focal plane of the fly-eye lens, and the size thereof is changed to change the illumination coherency σ (σ value = aperture aperture diameter / projection optical system pupil diameter, or σ Attention has been focused on a technique of changing the value = the exit numerical aperture of the illumination optical system / the incident numerical aperture of the projection optical system. Further, attention has been focused on a technique for forming a ring-shaped or quadrupolar secondary light source on the rear focal plane of the fly-eye lens to improve the depth of focus and resolution of the projection optical system.

  In general, in order to accurately transfer a fine pattern onto a wafer, the light intensity distribution of a secondary light source (substantial surface light source) formed on the rear focal plane of the fly-eye lens, that is, the illumination pupil plane, has uniformity. This is very important. Specifically, when the light intensity distribution formed on the illumination pupil plane is substantially non-uniform, a line width difference (line width asymmetry) of the pattern may occur between the vertical direction and the horizontal direction. is there.

Therefore, a technique is known in which a correction filter is provided on the illumination pupil plane of the illumination optical system or its conjugate position to adjust the light intensity distribution formed on the illumination pupil plane substantially uniformly (see, for example, Patent Document 1). ).
JP 2001-259133 A

  However, the conventional technique has not proposed a method for quantitatively evaluating the symmetry uniformity of the light intensity distributions of various shapes formed on the illumination pupil plane. For example, the correction filter can be optimally designed quantitatively, The relationship between the non-uniformity of the light intensity distribution on the illumination pupil plane and the line width asymmetry could not be grasped quantitatively.

  The present invention has been made in view of the above-described problems, and for example, an evaluation method capable of quantitatively and accurately evaluating the symmetry uniformity of the light intensity distribution formed on the illumination pupil plane of the illumination optical device. The purpose is to provide.

  Further, the present invention provides a uniform light intensity distribution on the illumination pupil plane by using an evaluation method that quantitatively and highly accurately evaluates the symmetry uniformity of the light intensity distribution formed on the illumination pupil plane of the illumination optical device, for example. It is an object of the present invention to provide an adjustment method that can be adjusted with high accuracy so that

  The present invention also provides an exposure apparatus and an exposure method capable of faithfully projecting and exposing a fine pattern using, for example, an illumination optical apparatus adjusted with high accuracy so that the light intensity distribution on the illumination pupil plane is uniform. The purpose is to provide.

In order to solve the above problems, in the first embodiment of the present invention, there is provided a method for evaluating a light intensity distribution formed on a predetermined surface,
A setting step of setting a first divided region and a second divided region that are substantially symmetrical with respect to a dividing line passing through a center point of the light intensity distribution in the region of the light intensity distribution;
The first light intensity integrated value obtained by integrating the light intensity distribution in the first divided area over the first divided area, and the light intensity distribution in the second divided area integrated over the second divided area. Calculating step of calculating the second integrated light intensity obtained respectively,
And a determination step of determining symmetry uniformity of the light intensity distribution with respect to the dividing line based on the first light intensity integrated value and the second light intensity integrated value.

In the second embodiment of the present invention, a measuring step for measuring the light intensity distribution formed on the predetermined surface;
An evaluation step for evaluating the light intensity distribution measured in the measurement step using the evaluation method of the first embodiment;
And an adjustment step of adjusting the light intensity distribution based on an evaluation result of the evaluation step.

In the third aspect of the present invention, in the adjustment method of the illumination optical device that illuminates the irradiated surface based on the light flux from the light source,
A measurement step of measuring a light intensity distribution of a substantial surface light source formed on the illumination pupil plane of the illumination optical device;
An evaluation step for evaluating the light intensity distribution measured in the measurement step using the evaluation method of the first embodiment;
And an adjustment step of adjusting the light intensity distribution based on an evaluation result of the evaluation step.

  According to a fourth aspect of the present invention, there is provided an illumination optical apparatus that is adjusted by the adjustment method according to the second or third aspect.

  According to a fifth aspect of the present invention, there is provided an exposure apparatus comprising the illumination optical apparatus according to the fourth aspect and exposing a mask pattern onto a photosensitive substrate.

  According to a sixth aspect of the present invention, there is provided an exposure method characterized by exposing a mask pattern onto a photosensitive substrate using the illumination optical apparatus according to the fourth aspect.

  In the present invention, a first divided region and a second divided region that are substantially symmetrical with respect to a dividing line passing through the center point in the region of the light intensity distribution are set, and the light intensity distribution in the first divided region is spread over the first divided region. The first light intensity integrated value obtained by integrating the light intensity distribution and the second light intensity integrated value obtained by integrating the light intensity distribution in the second divided area over the second divided area are calculated. Then, based on the calculated first light intensity integrated value and the second light intensity integrated value, symmetry uniformity regarding the dividing line of the light intensity distribution is determined.

  Therefore, in the present invention, for example, the symmetry uniformity of the light intensity distribution formed on the illumination pupil plane of the illumination optical apparatus can be evaluated quantitatively and with high accuracy, and the light intensity distribution on the illumination pupil plane can be made uniform. Thus, it can be adjusted with high accuracy. In the exposure apparatus and exposure method of the present invention, a fine pattern can be faithfully projected and exposed using an illumination optical device adjusted with high accuracy so that the light intensity distribution on the illumination pupil plane is uniform. As a result, a favorable device can be manufactured.

Embodiments of the present invention will be described with reference to the accompanying drawings.
FIG. 1 is a drawing schematically showing a configuration of an exposure apparatus according to an embodiment of the present invention. FIG. 2 is a diagram schematically showing an internal configuration of a measurement apparatus mounted on the exposure apparatus of FIG. In FIG. 1, the Y axis is set along the normal direction of the wafer W, which is a photosensitive substrate, and the X axis and the Z axis are set along two directions orthogonal to each other in a plane parallel to the wafer W. . In FIG. 1, the illumination optical device is set to perform annular illumination.

  The exposure apparatus of the present embodiment includes a laser light source 1 for supplying exposure light (illumination light). As the laser light source 1, for example, a KrF excimer laser light source that supplies light with a wavelength of 248 nm, an ArF excimer laser light source that supplies light with a wavelength of 193 nm, or the like can be used. A substantially parallel light beam emitted from the laser light source 1 has a rectangular cross section extending in the X direction, and is incident on a beam expander 2 including a pair of lenses 2a and 2b. Each lens 2a and 2b has a negative refracting power and a positive refracting power in the plane of FIG. 1 (in the YZ plane), respectively. Therefore, the light beam incident on the beam expander 2 is enlarged in the paper surface of FIG. 1 and shaped into a light beam having a predetermined rectangular cross section.

  A substantially parallel light beam via a beam expander 2 as a shaping optical system enters a zoom lens 4 via a diffractive optical element 3 for annular illumination. In the vicinity of the rear focal plane of the zoom lens 4, the incident surface of the micro fly's eye lens 5 is positioned. In general, a diffractive optical element is formed by forming a step having a pitch of the wavelength of exposure light (illumination light) on a substrate, and has a function of diffracting an incident beam to a desired angle. Specifically, the diffractive optical element 3 converts a rectangular parallel light beam incident along the optical axis AX into a divergent light beam having a ring-shaped cross section.

  The diffractive optical element 3 is configured to be detachable with respect to the illumination optical path, and is configured to be switchable between a diffractive optical element for circular illumination and a diffractive optical element for quadrupole illumination. The micro fly's eye lens 5 is an optical member composed of a large number of microlenses (optical elements) arranged vertically and horizontally and densely. In general, a micro fly's eye lens is configured by simultaneously forming a large number of micro optical surfaces on a parallel flat glass plate by applying MEMS technology (lithography + etching or the like). In this way, the light beam that has passed through the diffractive optical element 3 passes through the zoom lens 4 to the incident surface of the micro fly's eye lens 5 as a wavefront splitting type optical integrator, for example, an annular illumination field centered on the optical axis AX. Form.

  Here, the size of the annular illumination field formed (that is, the outer diameter) changes depending on the focal length of the zoom lens 4. The light beam incident on the micro fly's eye lens 5 is two-dimensionally divided by a large number of minute lenses, and a light source is formed on the rear focal plane of each minute lens on which the light beam is incident. In this way, on the rear focal plane of the micro fly's eye lens 5, a ring-shaped substantial surface light source having substantially the same light intensity distribution as the ring-shaped illumination field formed by the light flux incident on the micro fly's eye lens 5 ( (Hereinafter referred to as “secondary light source”).

  The luminous flux from the annular secondary light source formed on the rear focal plane (that is, the illumination pupil plane) of the micro fly's eye lens 5 passes through the correction filter 6 disposed in the vicinity thereof, and is collected by the condenser optical system 7. After receiving the light action, the mask blind 8 disposed on a surface optically conjugate with the mask M (and thus the wafer W) is illuminated in a superimposed manner. The configuration and operation of the correction filter 6 will be described later. In this way, a rectangular illumination field similar to the shape of each microlens constituting the micro fly's eye lens 5 is formed on the mask blind 8. The light beam that has passed through the rectangular opening (light transmitting portion) of the mask blind 8 receives the light condensing action of the imaging optical system 9 and then illuminates the mask M on which a predetermined pattern is formed in a superimposed manner.

  Thus, the imaging optical system 9 forms an image of the rectangular opening of the mask blind 8 on the mask M supported by the mask stage MS. That is, the mask blind 8 constitutes a field stop for defining an illumination area formed on the mask M (and thus the wafer W). A pattern to be transferred is formed on the mask M. For example, a rectangular pattern region having a long side along the X direction and a short side along the Z direction in the entire pattern region is illuminated.

  The light beam that has passed through the pattern of the mask M forms an image of the mask pattern on the wafer W, which is a photosensitive substrate, via the projection optical system PL. The projection optical system PL has an aperture stop AS that is arranged at the pupil position and has a variable aperture, and is substantially telecentric on both the mask M side and the wafer W side. Accordingly, an image of the secondary light source on the illumination pupil plane of the illumination optical system (2-9) is formed at the pupil position of the projection optical system PL, and the wafer W is Koehler illuminated by the light via the projection optical system PL. That is, the wafer W supported by the wafer stage WS has, for example, a long side along the X direction and along the Z direction so as to optically correspond to the rectangular illumination area on the mask M. Then, a pattern image is formed in a rectangular effective exposure area (that is, a static exposure area) having a short side.

  As described above, the illumination area on the mask M and the effective exposure area on the wafer W have a rectangular shape with short sides along the Z direction. Accordingly, by moving (scanning) the mask stage MS and the wafer stage WS synchronously along the short side direction of the rectangular effective exposure area and the illumination area, that is, the Z direction, and consequently the mask M and the wafer W, On the wafer W, a mask pattern is scanned and exposed on a shot area having a width equal to the long side of the effective exposure area and a length corresponding to the scanning amount (movement amount) of the wafer W.

  In addition, instead of the diffractive optical element 3, normal circular illumination can be performed by setting a diffractive optical element for circular illumination in the illumination optical path. The diffractive optical element for circular illumination converts a rectangular parallel light beam incident along the optical axis AX into a divergent light beam having a circular cross section. Therefore, the light beam that has passed through the diffractive optical element for circular illumination forms, for example, a circular illumination field around the optical axis AX on the incident surface of the micro fly's eye lens 5. As a result, a circular secondary light source having substantially the same light intensity distribution as the circular illumination field formed on the incident surface is also formed on the rear focal plane of the micro fly's eye lens 5.

  Further, quadrupole illumination can be performed by setting a diffractive optical element for quadrupole illumination in the illumination optical path instead of the diffractive optical element 3. The diffractive optical element for quadrupole illumination converts a rectangular parallel light beam incident along the optical axis AX into a divergent light beam having a quadrupole cross section. Therefore, the light beam that has passed through the diffractive optical element for quadrupole illumination forms a quadrupole illumination field on the incident surface of the micro fly's eye lens 5, for example, with the optical axis AX as the center. As a result, a quadrupole secondary light source having substantially the same light intensity distribution as the quadrupole illumination field formed on the incident surface is also formed on the rear focal plane of the micro fly's eye lens 5.

  The exposure apparatus of the present embodiment includes a measuring device 10 for measuring a light intensity distribution corresponding to the light intensity distribution at the position of the aperture stop AS in the projection optical system PL. Referring to FIG. 2, the measuring device 10 includes a pinhole member 10a, a condenser lens 10b, and a photodetector 10c such as a two-dimensional CCD. Here, the pinhole member 10a is disposed at the image plane position of the projection optical system PL (that is, the height position at which the exposed surface of the wafer W should be positioned during exposure). The pinhole member 10a is disposed at the front focal position of the condenser lens 10b, and the photodetector 10c is disposed at the rear focal position of the condenser lens 10b.

  Accordingly, the detection surface of the photodetector 10c is disposed at a position optically conjugate with the position of the aperture stop AS of the projection optical system PL. In the measuring apparatus 10, the light that has passed through the projection optical system PL passes through the pinhole of the pinhole member 10a, and after receiving the light collecting action of the condenser lens 10b, reaches the detection surface of the photodetector 10c. Thus, a light intensity distribution corresponding to the light intensity distribution at the position of the aperture stop AS is formed on the detection surface of the photodetector 10c. As a result, the measurement apparatus 10 is optically conjugate with the illumination pupil plane (the rear focal plane of the micro fly's eye lens 5) of the illumination optical system (2-9) based on the light that has passed through the projection optical system PL. The light intensity distribution on the surface is measured.

  FIG. 3 is a flowchart schematically showing the steps of the adjustment method including the evaluation method of the light intensity distribution measured using the measurement apparatus of the present embodiment. Referring to FIG. 3, in the adjustment method of the present embodiment, for example, using the measurement apparatus 10, the optically conjugate with the illumination pupil plane of the illumination optical system (2-9) based on the light that has passed through the projection optical system PL. The light intensity distribution on a smooth surface is measured (S1). In the present embodiment, for the evaluation and adjustment of the annular light intensity distribution measured corresponding to the annular secondary light source formed on the illumination pupil plane of the illumination optical system (2-9) during annular illumination. The present invention is applied by way of example.

  Next, in the adjustment method of the present embodiment, the first divided region and the second divided region that are substantially symmetric with respect to the dividing line passing through the center point of the light intensity distribution in the annular region of the light intensity distribution measured in the measuring step S1. Are set (S2). Specifically, in the setting step S2, as shown in FIG. 4A, a center point 42 is defined from a circular outer shape (outer contour) 41 of the annular light intensity distribution 40 (S21). Then, as shown in FIG. 4B, four dividing lines 43 to 46 passing through the center point 42 defined in the defining step S21 are assumed (S22).

  In the assumed step S22, four dividing lines 43 to 46 are assumed so that a circle centered on the center point 42 is equally divided into four in the circumferential direction. Further, as shown in FIGS. 5 (a) and 5 (b) and FIGS. 6 (a) and 6 (b), with respect to each of the dividing lines 43 to 46 assumed in the assumed step S22, the first divided area A1 having a semi-annular shape. -A4 and half-ring-shaped second divided regions B1-B4 are respectively defined (S23). 1st division area A1-A4 prescribed | regulated by prescription | regulation process S23 is a half ring-shaped area | region located in one side of each division line 43-46, and 2nd division area B1-B4 is each division line 43-46. This is a half-banded region located on the other side.

Next, in the adjustment method of this embodiment, the light intensity distributions I _A1 (x, y) to I _A4 (x, y) in the first divided areas A1 to A4 are integrated over the first divided areas A1 to A4, respectively. The first integrated light intensity values P _{A1 to} P _A4 and the light intensity distributions I _B1 (x, y) to I _B4 (x, y) in the second divided areas _{B1 to} B4 are obtained as the second divided areas B1 to B1. Second light intensity integrated values P _{B1 to} P _B4 obtained by integrating over _B4 are calculated (S3).

Specifically, focusing on the first dividing line 43 that passes through the center point 42 and extends horizontally in the drawing in FIG. 5A, the first dividing region A1 and the half annular zone that are symmetric with respect to the first dividing line 43. Second divided region B1 is defined, and the first light intensity integrated value P _A1 obtained by integrating the light intensity distribution I _A1 (x, y) of the first divided region A1 and the light intensity distribution of the second divided region B1 The second light intensity integrated value P _B1 obtained by integrating with respect to I _B1 (x, y) is expressed by the following equations (1) and (2), respectively.

Similarly, when attention is paid to the second dividing line 44 that passes through the center point 42 and extends from the lower left to the upper right in the drawing at an angle of 45 degrees in FIG. 5B, a first half-ring-shaped first dividing that is symmetrical with respect to the second dividing line 44. A region A2 and a second annular region B2 having a semi-annular zone are defined, and a first light intensity integrated value P _A2 and a second division obtained by integrating the light intensity distribution I _A2 (x, y) of the first divided region A2. Second light intensity integrated values P _B2 obtained by integrating the light intensity distribution I _B2 (x, y) in the region B2 are expressed by the following equations (3) and (4), respectively.

Similarly, in FIG. 6A, focusing on the third dividing line 45 that passes through the center point 42 and extends in the vertical direction in the drawing, the first divided region A3 and the half annular zone that are symmetrical with respect to the third dividing line 45 are formed. Second divided area B3 is defined, and the first light intensity integrated value P _A3 obtained by integrating the light intensity distribution I _A3 (x, y) of the first divided area A3 and the light intensity distribution of the second divided area B3 Second light intensity integrated values P _B3 obtained by integrating with respect to I _B3 (x, y) are expressed by the following equations (5) and (6), respectively.

Further, when attention is paid to the fourth dividing line 46 that passes through the center point 42 and extends at an angle of 45 degrees from the upper left to the lower right in the drawing in FIG. A region A4 and a second annular region B4 having a semi-annular zone are defined, and a first light intensity integrated value P _A4 and a second division obtained by integrating the light intensity distribution I _A4 (x, y) of the first divided region A4. Second light intensity integrated values P _B4 obtained by integrating the light intensity distribution I _B4 (x, y) in the region B4 are expressed by the following equations (7) and (8), respectively.

Further, in the calculation step S3, the total light obtained by integrating the entire annular light intensity distribution I _ALL (x, y) over the region ALL (corresponding to the annular region 40 in FIG. 4A). The intensity integrated value P _{ALL is} also calculated. The total light intensity integrated value P _ALL is expressed by the following equation (9).

Next, in the adjustment method of the present embodiment, the first light intensity integrated values P _{A1 to} P _A4 and the second light intensity integrated values P _{B1 to} P _B4 respectively obtained for the dividing lines 43 to 46 through the calculation step S3 are obtained. Based on this, the symmetry uniformity with respect to each of the dividing lines 43 to 46 of the annular light intensity distribution 40 is determined (S4). Specifically, in the determination step S4, for the first dividing line 43, the first divided area A1 and the second divided area are based on the difference between the first light intensity integrated value P _A1 and the second light intensity integrated value P _B1. The error E ₁ of the symmetry uniformity of the light intensity distribution with respect to B1 is evaluated.

An error E ₁ of symmetry uniformity of the light intensity distribution between the first divided area A1 and the second divided area B1 defined by the first dividing line 43 is expressed by the following equation (10). Similarly, the error E ₂ of the symmetry uniformity of the light intensity distribution between the first divided area A 2 and the second divided area B 2 defined by the second dividing line 44, and the first defined by the third dividing line 45. Error E ₃ of the symmetry uniformity of the light intensity distribution between the divided area A3 and the second divided area B3, the light between the first divided area A4 and the second divided area B4 defined by the fourth dividing line 46 The error E ₄ of the symmetry uniformity of the intensity distribution is expressed by the following equations (11) to (13).

E ₁ = (| P _A1 −P _B1 |) / (P _A1 + P _B1 ) (10)
E ₂ = (| P _A2 −P _B2 |) / (P _A2 + P _B2 ) (11)
E ₃ = (| P _A3 −P _B3 |) / (P _A3 + P _B3 ) (12)
E ₄ = (| P _A4 −P _B4 |) / (P _A4 + P _B4 ) (13)

As described above, the error E ₁ is the symmetry uniformity error related to the first dividing line 43 of the annular light intensity distribution 40, and the error E ₂ is the symmetry uniformity related to the second dividing line 44 of the annular light intensity distribution 40. The error E ₃ is an error of symmetry uniformity with respect to the third dividing line 45 of the annular light intensity distribution 40, and the error E ₄ is symmetry uniformity of the annular light intensity distribution 40 with respect to the fourth dividing line 46. Represents the error.

FIG. 7 is a bar graph showing symmetric uniformity errors E _{1 to} E ₄ of the annular light intensity distribution 40 with respect to the first dividing line 43, the second dividing line 44, the third dividing line 45, and the fourth dividing line 46. It is a figure shown with a form. Referring to FIG. 7, the symmetry uniformity error E ₁ related to the first dividing line 43 of the annular light intensity distribution 40 and the symmetry uniformity error E ₄ related to the fourth dividing line 46 are about 3.2 to about 3. 4 (strictly, 3.36)%, which is relatively large, and the symmetry uniformity error E ₂ with respect to the second dividing line 44 and the symmetry uniformity error E ₃ with respect to the third dividing line 45 of the annular light intensity distribution 40. Is relatively small, about 1.75 to about 1.0%.

Alternatively, in the determination step S4, for each of the dividing lines 43 to 46, the first divided area A1 based on the first index corresponding to the ratio of the first light intensity integrated values P _{A1 to} P _{A4 to} the total light intensity integrated value P _ALL . The error of symmetry uniformity of the light intensity distribution in .about.A4 is evaluated, and the second divided region is based on the second index corresponding to the ratio of the second light intensity integrated values P _{B1 to} P _B4 to the total light intensity integrated value P _ALL . It is also possible to evaluate an error in symmetry uniformity of the light intensity distribution in B1 to B4.

Specifically, with respect to the first dividing line 43, the light intensity distribution in the first divided area A1 is based on the first index corresponding to the ratio of the first light intensity integrated value P _{A1 to} the total light intensity integrated value P _ALL . The symmetry uniformity error _ECU is expressed by the following equation (14). Further, with respect to the first dividing line 43, the symmetrical uniformity of the light intensity distribution in the second divided region B1 based on the second index corresponding to the ratio of the second light intensity integrated value P _B1 to the total light intensity integrated value P _ALL . The error E _CB is expressed by the following equation (15).
E _CU = 2 × P _A1 / P _ALL −1 (14)
E _CB = 2 × P _B1 / P _ALL −1 (15)

Similarly, the error E _LU of the symmetric uniformity of the light intensity distribution of the first divided region A2 and the error E _RB of the symmetric uniformity of the light intensity distribution of the second divided region B2 with respect to the second divided line 44, the third divided line 45. The error E _LC of the symmetry uniformity of the light intensity distribution of the first divided area A3 and the error E _RC of the symmetry uniformity of the light intensity distribution of the second divided area B3, and the light of the first divided area A4 related to the fourth dividing line 46 The error E _LB of symmetry of intensity distribution and the error E _RU of symmetry uniformity of the light intensity distribution of the second divided region B4 are respectively expressed by the following equations (16) to (21).

E _LU = 2 × P _A2 / P _ALL −1 (16)
E _RB = 2 × P _B2 / P _ALL −1 (17)
E _LC = 2 × P _A3 / P _ALL −1 (18)
E _RC = 2 × P _B3 / P _ALL −1 (19)
E _LB = 2 × P _A4 / P _ALL −1 (20)
E _RU = 2 × P _B4 / P _ALL −1 (21)

  FIG. 8 is a diagram showing errors in the symmetry uniformity of the light intensity distribution in each of the divided areas A1 to A4 and B1 to B4. In FIG. 8, a circle 80 drawn with a bold line corresponds to an error of 0, a circle 81 outside the circle 80 corresponds to an error of a predetermined positive value, and a circle 82 inside the circle 80 is a circle 81. It corresponds to an error of negative values having the same absolute value but different signs. Therefore, if the center of the black diamond in the figure representing the error E is on the line of the circle 80, the value of the error E is 0, and if the center of the black diamond is outside the circle 80, the value of the error E is shown. Is a positive value, and if the center of the black diamond is inside the circle 80, the value of the error E is a negative value.

  In FIG. 8, the orientation of the center position of each ring-shaped divided region (A1 to A4, B1 to B4) with respect to the center point 42 is the plot position of the black diamond representing the symmetry uniformity error of the light intensity distribution of each divided region. It corresponds to each direction. Further, as described above, the center circle 80 on the line corresponds to error 0, the movement of the circle 80 from the line radially outward corresponds to a positive error, and the circle 80 moves on the line radially inward from the line. Corresponds to a negative error. Therefore, referring to FIG. 8, the magnitude and direction of the symmetrical uniformity error of the light intensity distribution in each divided region can be grasped instantaneously and accurately.

  Finally, in the adjustment method of the present embodiment, the light intensity distribution is adjusted based on the evaluation result of the determination step S4 (that is, the evaluation result of the evaluation steps S2 to S4) (S5). Specifically, in the adjustment step S5, the correction filter 6 having a predetermined transmittance distribution is arranged on the rear focal plane of the micro fly's eye lens 5, that is, the illumination pupil plane or in the vicinity thereof, thereby forming the illumination pupil plane. Adjustment is made so that the error of the symmetry uniformity of the light intensity distribution becomes small.

  In this embodiment, as an example, a correction filter 6 having a transmittance distribution as shown in FIG. 9B is used, and a light intensity distribution having a symmetry uniformity error as shown in FIG. 9A (FIG. 8). Is adjusted to a light intensity distribution with a relatively small symmetry uniformity error, as shown in FIG. Here, the upper half region 6a of the correction filter 6 in the figure has a transmittance of 100%, and the lower half region 6b in the figure has a transmittance of 96%. A boundary line 6c between the region 6a and the region 6b corresponds to the first dividing line 43 of the annular light intensity distribution. As a result, the light intensity distribution shown in FIG. 9A having a symmetric uniformity error of ± 3.36% at the maximum is shown in FIG. 9C having a symmetric uniformity error of ± 2.34% at the maximum. The light intensity distribution can be adjusted.

As described above, in the present embodiment, the first divided areas (A1 to A4) and the second divided areas (B1 to B4) that are substantially symmetrical with respect to the dividing line passing through the center point in the area of the light intensity distribution are set. The first light intensity integrated value (P _{A1 to} P _A4 ) obtained by integrating the light intensity distribution in the first divided area over the first divided area, and the light intensity distribution in the second divided area as the second divided area The second integrated light intensity values (P _{B1 to} P _B4 ) obtained by integration over a range are calculated. Then, based on the calculated first light intensity integrated value (P _{A1 to} P _A4 ) and the second light intensity integrated value (P _{B1 to} P _B4 ), the symmetry uniformity regarding the dividing line of the light intensity distribution is determined. .

  Therefore, in this embodiment, the symmetry uniformity of the light intensity distribution formed on the illumination pupil plane of the illumination optical device (1-9) can be evaluated quantitatively and with high accuracy. It can be adjusted with high accuracy so that the intensity distribution is uniform. In the exposure apparatus of the present embodiment, a fine pattern is faithfully projected and exposed using the illumination optical apparatus (1 to 9) adjusted with high accuracy so that the light intensity distribution on the illumination pupil plane is uniform. Can do. In particular, by quantitatively evaluating the symmetry uniformity of the light intensity distribution, the correction filter 6 can be optimally designed quantitatively, and the relationship between the nonuniformity of the light intensity distribution on the illumination pupil plane and the line width asymmetry can be seen. It can be grasped quantitatively. For example, in an exposure apparatus, it is preferable to suppress the error of symmetry uniformity of the light intensity distribution formed on the illumination pupil plane of the illumination optical apparatus to within ± 5%, and to suppress the error of symmetry uniformity to within ± 3%. More preferably.

  In the above-described embodiment, four dividing lines 43 to 46 that divide a circle centered on the center point 42 into four equal parts in the circumferential direction are assumed. In other words, the symmetry uniformity of the light intensity distribution is analyzed in increments of 45 degrees with the center point 42 as the center. However, the present invention is not limited to this, and various modifications can be made for the step angle of analysis. In general, the smaller the step angle of analysis, the more accurate and detailed analysis becomes possible. In FIG. 10, the result (a) obtained based on the method of FIG. 8 when the analysis step angle is 45 degrees, and the result obtained based on the method of FIG. 8 when the analysis step angle is 1 degree ( b) is shown in contrast. In FIG. 10B, a line 84 corresponds to a set of center points of each black diamond when a large number of black diamonds representing errors are plotted.

  In the above-described embodiment, the first divided region is assumed on one side of the dividing line, and the second divided region is assumed on the other side. However, the present invention is not limited to this, and the first divided region and the second divided region that are substantially symmetric with respect to the dividing line can be defined by two straight lines that intersect at a predetermined angle at the center point. In FIG. 11, as an example, a first divided region 62 and a second divided region 63 that are substantially symmetric with respect to a dividing line 61 passing through the center point 60 are two straight lines 64 that intersect at an angle of 90 degrees at the center point 60 and A state defined by 65 is shown. The crossing angle between the two straight lines 64 and 65 can be appropriately changed between 0 degrees and 180 degrees. If the intersection angle between the two straight lines 64 and 65 is set to 180 degrees, the divided regions 62 and 63 are both in a half-ring shape as in the present embodiment.

  In the above-described embodiment, the light intensity distribution is adjusted using the correction filter 6 disposed on the rear focal plane of the micro fly's eye lens 5 or in the vicinity thereof. However, the present invention is not limited to this, and various modifications can be made to the arrangement and adjustment means of the correction filter 6. For example, the correction filter 6 can be disposed on the pupil plane of the imaging optical system 9 or in the vicinity thereof. For example, as disclosed in Japanese Patent Laid-Open No. 10-319321, a correction filter for adjusting the light intensity distribution on the illumination pupil plane may be arranged on the incident surface side of the fly-eye lens as an optical integrator. . Further, the light intensity distribution can be adjusted by using a suitable means other than the correction filter, for example, a deformable aperture stop as disclosed in JP-A-2002-75843. Further, in the above-described embodiment, the present invention is applied to the evaluation and adjustment of the symmetric uniformity of the annular light intensity distribution. However, the present invention is not limited to this, and various shapes such as a circular shape and a quadrupole shape are available. The present invention can be similarly applied to the evaluation and adjustment of the symmetrical uniformity of the light intensity distribution of various shapes.

 Further, in the above-described embodiment, the pinhole member 10a of the measuring device 10 is arranged at the image plane position of the projection optical system PL, and illumination of the illumination optical system (2-9) based on the light that has passed through the projection optical system PL. The light intensity distribution on a plane optically conjugate with the pupil plane is measured. Based on the measurement result, the light intensity distribution is evaluated for the exposure apparatus on which the illumination optical devices (1 to 9) are mounted. However, the present invention is not limited to this, and the pinhole member 10a of the measuring device 10 is arranged at the irradiated surface position (corresponding to the object plane position of the projection optical system PL) of the illumination optical device (1-9), and illumination optics The light intensity distribution can be evaluated in the same manner for only the devices (1 to 9). For a more detailed configuration and operation of the measuring device 10, reference can be made to, for example, Japanese Patent Laid-Open No. 2000-19012.

  In the exposure apparatus according to the above-described embodiment, the illumination optical device illuminates the mask (reticle) (illumination process), and the projection optical system is used to expose the transfer pattern formed on the mask onto the photosensitive substrate (exposure). Step), a micro device (semiconductor element, imaging element, liquid crystal display element, thin film magnetic head, etc.) can be manufactured. Refer to the flowchart of FIG. 12 for an example of a method for obtaining a semiconductor device as a micro device by forming a predetermined circuit pattern on a wafer or the like as a photosensitive substrate using the exposure apparatus of the above-described embodiment. To explain.

  First, in step 301 of FIG. 12, a metal film is deposited on one lot of wafers. In the next step 302, a photoresist is applied on the metal film on the one lot of wafers. Thereafter, in step 303, the image of the pattern on the mask is sequentially exposed and transferred to each shot area on the wafer of one lot through the projection optical system using the exposure apparatus of the above-described embodiment. Thereafter, in step 304, the photoresist on the one lot of wafers is developed, and in step 305, the resist pattern is etched on the one lot of wafers to form a pattern on the mask. Corresponding circuit patterns are formed in each shot area on each wafer. Thereafter, a device pattern such as a semiconductor element is manufactured by forming a circuit pattern of an upper layer. According to the semiconductor device manufacturing method described above, a semiconductor device having an extremely fine circuit pattern can be obtained with high throughput.

  In the exposure apparatus of the above-described embodiment, a liquid crystal display element as a micro device can be obtained by forming a predetermined pattern (circuit pattern, electrode pattern, etc.) on a plate (glass substrate). Hereinafter, an example of the technique at this time will be described with reference to the flowchart of FIG. In FIG. 13, in the pattern formation process 401, a so-called photolithography process is performed in which the exposure pattern of the above-described embodiment is used to transfer and expose a mask pattern onto a photosensitive substrate (such as a glass substrate coated with a resist). . By this photolithography process, a predetermined pattern including a large number of electrodes and the like is formed on the photosensitive substrate. Thereafter, the exposed substrate undergoes steps such as a developing step, an etching step, and a resist stripping step, whereby a predetermined pattern is formed on the substrate, and the process proceeds to the next color filter forming step 402.

  Next, in the color filter forming step 402, a large number of sets of three dots corresponding to R (Red), G (Green), and B (Blue) are arranged in a matrix or three of R, G, and B A color filter is formed by arranging a plurality of stripe filter sets in the horizontal scanning line direction. Then, after the color filter forming step 402, a cell assembly step 403 is executed. In the cell assembly step 403, a liquid crystal panel (liquid crystal cell) is assembled using the substrate having the predetermined pattern obtained in the pattern formation step 401, the color filter obtained in the color filter formation step 402, and the like.

  In the cell assembly step 403, for example, liquid crystal is injected between the substrate having the predetermined pattern obtained in the pattern formation step 401 and the color filter obtained in the color filter formation step 402, and a liquid crystal panel (liquid crystal cell) is obtained. ). Thereafter, in a module assembling step 404, components such as an electric circuit and a backlight for performing a display operation of the assembled liquid crystal panel (liquid crystal cell) are attached to complete a liquid crystal display element. According to the above-described method for manufacturing a liquid crystal display element, a liquid crystal display element having an extremely fine circuit pattern can be obtained with high throughput.

  In the above-described embodiment, the present invention is applied to an illumination optical apparatus having a specific configuration as shown in FIG. 1, but various modifications can be made to the specific configuration of the illumination optical apparatus. It is. In the above-described embodiment, KrF excimer laser light (wavelength: 248 nm) or ArF excimer laser light (wavelength: 193 nm) is used as exposure light. However, the present invention is not limited to this, and other appropriate laser light sources are used. The present invention can also be applied to.

It is a figure which shows schematically the structure of the exposure apparatus concerning embodiment of this invention. It is a figure which shows schematically the internal structure of the measuring device mounted in the exposure apparatus of FIG. It is a flowchart which shows roughly the process of the adjustment method containing the evaluation method of the light intensity distribution measured using the measuring device of this embodiment. (A) is a figure which shows a mode that a center point is defined from the circular-shaped external shape of an annular | circular shaped light intensity distribution, and (b) is a figure which shows a mode that four dividing lines which pass through the defined center point are assumed. (A) shows the first divided area A1 and the second divided area B1 defined for the first dividing line, and (b) shows the first divided area A2 and the second divided area B2 defined for the second dividing line, respectively. FIG. (A) shows the first and second divided areas A3 and B3 defined for the third dividing line, and (b) shows the first and second divided areas A4 and B4 defined for the fourth dividing line, respectively. FIG. It is a diagram illustrating a first dividing line to fourth dividing line zonal error E ₁ to E ₄ of symmetry uniformity of the light intensity distribution for a bar graph form. It is a figure which shows the difference | error of the symmetrical uniformity of the light intensity distribution of each division area A1-A4, B1-B4, respectively. It is a figure which shows a mode that the light intensity distribution formed in an illumination pupil plane is adjusted using a correction filter. A result (a) obtained based on the method of FIG. 8 when the analysis step angle is 45 degrees and a result (b) obtained based on the method of FIG. 8 when the analysis step angle is 1 degree. It is a figure shown by contrast. It is a figure which shows the modification which prescribes | regulates the 1st division area and 2nd division area which are respectively substantially symmetrical with respect to a division line by two straight lines which cross | intersect at a predetermined angle in a center point. It is a flowchart of the method at the time of obtaining the semiconductor device as a microdevice. It is a flowchart of the method at the time of obtaining the liquid crystal display element as a microdevice.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Laser light source 3 Diffractive optical element 4 Zoom lens 5 Micro fly eye lens 6 Correction filter 7 Condenser optical system 8 Mask blind 9 Imaging optical system 10 Measuring apparatus 10a Pinhole member 10b Condensing lens 10c Photodetector (two-dimensional CCD)
M Mask MS Mask stage PL Projection optical system AS Aperture stop W Wafer WS Wafer stage

Claims (17)

A method for evaluating a light intensity distribution formed on a predetermined surface,
A setting step of setting a first divided region and a second divided region that are substantially symmetrical with respect to a dividing line passing through a center point of the light intensity distribution in the region of the light intensity distribution;
The first light intensity integrated value obtained by integrating the light intensity distribution in the first divided area over the first divided area, and the light intensity distribution in the second divided area integrated over the second divided area. Calculating step of calculating the second integrated light intensity obtained respectively,
And a determining step of determining symmetry uniformity of the light intensity distribution with respect to the dividing line based on the first light intensity integrated value and the second light intensity integrated value. The setting step defines the first divided region and the second divided region by a defining step of defining the center point from the outer shape of the light intensity distribution, and two straight lines that intersect at a predetermined angle at the center point. The evaluation method according to claim 1, further comprising a defining step that defines each. The evaluation method according to claim 1, wherein the calculating step includes a step of calculating a total light intensity integrated value obtained by integrating the entire light intensity distribution over the region. In the determining step, an error in symmetry uniformity of the light intensity distribution between the first divided region and the second divided region based on a difference between the first light intensity integrated value and the second light intensity integrated value. The evaluation method according to claim 1, wherein the evaluation method is evaluated. In the determining step, an error in symmetry uniformity of the light intensity distribution in the first divided region is evaluated based on a first index corresponding to a ratio of the first light intensity integrated value to the total light intensity integrated value, 4. The error of symmetry uniformity of the light intensity distribution in the second divided region is evaluated based on a second index corresponding to the ratio of the second light intensity integrated value to the total light intensity integrated value. Evaluation method described in 1. 6. The setting step according to claim 1, wherein a plurality of dividing lines passing through the center point are assumed, and the first divided area and the second divided area are respectively set for each dividing line. 2. The evaluation method according to item 1. The evaluation method according to claim 6, wherein in the setting step, the plurality of dividing lines are assumed so that a circle centered on the center point is substantially equally divided in a circumferential direction. A measurement process for measuring the light intensity distribution formed on the predetermined surface;
An evaluation step for evaluating the light intensity distribution measured in the measurement step using the evaluation method according to any one of claims 1 to 7,
And an adjustment step of adjusting the light intensity distribution based on an evaluation result of the evaluation step. 9. The adjustment method according to claim 8, wherein in the adjustment step, adjustment is performed so that an error in symmetry uniformity of the light intensity distribution is suppressed to within ± 5%. In the adjustment method of the illumination optical device that illuminates the illuminated surface based on the light flux from the light source,
A measurement step of measuring a light intensity distribution of a substantial surface light source formed on the illumination pupil plane of the illumination optical device;
An evaluation step for evaluating the light intensity distribution measured in the measurement step using the evaluation method according to any one of claims 1 to 7,
And an adjustment step of adjusting the light intensity distribution based on an evaluation result of the evaluation step. In the adjustment step, a correction filter having a required transmittance distribution for suppressing an error in symmetry uniformity of the light intensity distribution within ± 5% is installed on or near the illumination pupil plane. Item 11. The adjustment method according to Item 10. The adjustment method according to claim 10 or 11, wherein, in the measurement step, a light intensity distribution on a surface optically conjugate with the illumination pupil plane is measured based on light passing through the irradiated surface. An illumination optical apparatus adjusted by the adjustment method according to claim 10. An exposure apparatus comprising the illumination optical apparatus according to claim 13, wherein a mask pattern is exposed onto a photosensitive substrate. A projection optical system for forming an image of the pattern of the mask on the photosensitive substrate;
15. The exposure apparatus according to claim 14, wherein in the measurement step, a light intensity distribution on a surface optically conjugate with the illumination pupil plane is measured based on the light that has passed through the projection optical system. An exposure method comprising: exposing a pattern of a mask onto a photosensitive substrate using the illumination optical device according to claim 13. A projection step of forming an image of the pattern of the mask on the photosensitive substrate using a projection optical system;
17. The exposure method according to claim 16, wherein in the measurement step, a light intensity distribution on a surface optically conjugate with the illumination pupil plane is measured based on light that has passed through the projection optical system.

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