JP2005353869A - Light intensity distribution evaluation method, adjustment method, illumination optical apparatus, exposure apparatus, and exposure method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate the distribution of the intensity of light formed on the illumination pupil surface of an illumination optical device, for example, as effectively equivalent and uniform light intensity distribution while considering not only its outer form but also non-uniform distribution. <P>SOLUTION: A method of evaluating the light intensity distribution approximately formed in the shape of an annular as uniform light intensity distribution using the shape of an annular effectively equivalent therewith includes a step of determining a primary moment value for the light intensity distribution approximately formed in the shape of the annular (S2); determining a secondary moment value for the light intensity distribution approximately formed in the shape of the annular (S3); determining an intermediate diameter corresponding to an average value of an annular outer diameter and an inner diameter of the uniform light intensity distribution based on the primary moment value (S4); and determining a width corresponding to a difference of the annular outer diameter and the inner diameter of the uniform light intensity distribution based on the secondary moment value (S5). <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. It relates to the evaluation of the 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, the light intensity distribution of the secondary light source (substantially surface light source) formed on the rear focal plane of the fly-eye lens, that is, the illumination pupil plane is substantially uniform (the light intensity is substantially constant over the entire secondary light source). If so, it is easy to grasp the relationship between the shape and size of the secondary light source and the imaging characteristics, that is, to evaluate the imaging characteristics based on the shape and size of the secondary light source. However, the secondary light source actually obtained in the exposure apparatus has a light intensity distribution that is not uniform and has a relatively large change.

  In the prior art, the shape and size of the secondary light source are evaluated by ignoring the non-uniform distribution and considering only the outer shape. As a result, the imaging characteristics cannot be correctly evaluated on the basis of the shape and size of the secondary light source evaluated only considering the outer shape, and as a result, the resolution line width varies between two different exposure apparatuses. There was an inconvenience that this was likely to occur.

  The present invention has been made in view of the above-described problems. For example, the light intensity distribution formed on the illumination pupil plane of the illumination optical apparatus is effectively equivalent considering not only the outer shape but also the non-uniform distribution. An object of the present invention is to provide an evaluation method that can be evaluated as a uniform light intensity distribution.

  Further, the present invention increases the light intensity distribution on the illumination pupil plane by using an evaluation method that evaluates, for example, the light intensity distribution formed on the illumination pupil plane of the illumination optical apparatus as an effective equivalent uniform light intensity distribution. An object of the present invention is to provide an adjustment method capable of adjusting the accuracy.

  Another object of the present invention is to provide an exposure apparatus and an exposure method capable of faithfully projecting and exposing a fine pattern using, for example, an illumination optical apparatus in which the light intensity distribution on the illumination pupil plane is adjusted with high accuracy. And

In order to solve the above-described problem, in the first embodiment of the present invention, the light intensity distribution having a substantially circular shape formed on the predetermined surface is uniform in a circular shape that is effectively equivalent to the light intensity distribution having the substantially circular shape. A method for evaluating the light intensity distribution,
Integrating a product of the light intensity at each point in the region of the light intensity distribution having a substantially circular shape and a distance between the predetermined center point and each point over the entire region to obtain a first moment value; ,
And a step of obtaining an outer diameter of the uniform light intensity distribution with the circular shape centered on the predetermined center point based on the first moment value.

In the second embodiment of the present invention, the substantially annular light intensity distribution formed on the predetermined surface is evaluated as a uniform light intensity distribution with an annular shape that is effectively equivalent to the substantially annular light intensity distribution. A way to
Integrating the product of the light intensity at each point in the region of the substantially annular light intensity distribution and the distance between the predetermined center point and each point over the entire region to obtain the first moment value When,
A second moment is obtained by integrating the product of the light intensity at each point in the substantially annular light intensity distribution area and the square of the distance between the predetermined center point and each point over the entire area. A process for determining a value;
Obtaining an intermediate diameter corresponding to an average value of an outer diameter and an inner diameter of a uniform light intensity distribution in the annular shape centered on the predetermined center point based on the first moment value;
Obtaining a width corresponding to a difference between an outer diameter and an inner diameter of the uniform light intensity distribution in the annular shape centered on the predetermined center point based on the second moment value. Provide an evaluation method.

In a third aspect of the present invention, a method for evaluating a predetermined light intensity distribution formed on a predetermined surface as a uniform light intensity distribution that is effectively equivalent to the predetermined light intensity distribution,
Integrating the product of the light intensity at each point in the region of the predetermined light intensity distribution and the distance between the predetermined center point and each point over the entire region to obtain a first moment value;
And determining the outer diameter of the uniform light intensity distribution centered on the predetermined center point based on the first moment value.

In the fourth embodiment of the present invention, a method of evaluating a multipolar light intensity distribution formed on a predetermined surface as a multipolar and uniform light intensity distribution that is effectively equivalent to the multipolar light intensity distribution. Because
Integrating a light intensity at each point in the region of the multipolar light intensity distribution in a circumferential direction with respect to a predetermined center point to obtain an annular light intensity distribution centered on the predetermined center point;
Integrating a product of light intensity at each point in the zone-shaped light intensity distribution region and the distance between the predetermined center point and each point over the entire region to obtain a first moment value; When,
A second moment value is obtained by integrating the product of the light intensity at each point in the region of the annular light intensity distribution and the square of the distance between the predetermined center point and each point over the entire region. The process of seeking
Obtaining an intermediate diameter corresponding to an average value of an outer diameter and an inner diameter of the multipolar and uniform light intensity distribution around the predetermined center point based on the first moment value;
Obtaining a width corresponding to a difference between an outer diameter and an inner diameter of the multipolar and uniform light intensity distribution centered on the predetermined center point based on the second moment value. Provide an evaluation method.

In the fifth embodiment of the present invention, a measurement step of 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 the first to fourth embodiments;
And an adjustment step of adjusting the light intensity distribution based on an evaluation result of the evaluation step.

In the sixth 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 according to the first to fourth embodiments;
And an adjustment step of adjusting the light intensity distribution based on an evaluation result of the evaluation step.

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

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

  According to a ninth 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 seventh aspect.

  In the present invention, for example, the light intensity, the optical axis (predetermined center point), and the distance between each point in the region of the light intensity distribution having a substantially annular shape formed on the illumination pupil plane of the illumination optical device. The product is integrated over the whole area to obtain the first moment value. Further, the product of the light intensity at each point in the region of the light intensity distribution having a substantially annular shape and the square of the distance between the optical axis and each point is integrated over the entire region to obtain the second moment value. Then, based on the primary moment value and the secondary moment value, the outer diameter, the inner diameter, the annular ratio, etc. of the uniform light intensity distribution are obtained with an annular shape that is effectively equivalent to the light intensity distribution of the annular shape. .

  In this way, in the present invention, for example, the light intensity distribution (secondary light source) formed on the illumination pupil plane of the illumination optical device is effectively equivalent and uniform light intensity considering not only the outer shape but also the non-uniform distribution. It can be evaluated as a distribution, and the light intensity distribution on the illumination pupil plane can be adjusted with high accuracy. Therefore, in the exposure apparatus and the exposure method of the present invention, it is possible to faithfully project and expose a fine pattern using an illumination optical apparatus in which the light intensity distribution on the illumination pupil plane is adjusted with high accuracy. 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 and enters the incident surface of the micro fly's eye lens 5 as a wavefront division 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 is subjected to the condensing action of the condenser optical system 6 and then the mask M (and thus the wafer W). ) And the mask blind 7 disposed on a surface optically conjugate with the mask blind. Thus, 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 7. The light beam that has passed through the rectangular opening (light transmitting portion) of the mask blind 7 receives the light condensing action of the imaging optical system 8 and then illuminates the mask M on which a predetermined pattern is formed in a superimposed manner.

  Thus, the imaging optical system 8 forms an image of the rectangular opening of the mask blind 7 on the mask M supported by the mask stage MS. In other words, the mask blind 7 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. Therefore, an image of the secondary light source on the illumination pupil plane of the illumination optical system (2 to 8) 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.

  Further, by setting another diffractive optical element for multipole illumination in the illumination optical path instead of the diffractive optical element 3, various multipole illumination (bipolar illumination, octupole illumination, etc.) can be performed. . Similarly, various forms of modified illumination can be performed by setting a diffractive optical element having appropriate characteristics in the illumination optical path instead of the diffractive optical element 3.

  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 (2-8) 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 having a substantially annular shape measured by using the measuring apparatus according to the present embodiment. Referring to FIG. 3, in the adjustment method of the present embodiment, for example, using the measurement apparatus 10, optically conjugate with the illumination pupil plane of the illumination optical system (2 to 8) 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, evaluation and adjustment of the light intensity distribution in a substantially annular shape measured corresponding to the annular secondary light source formed on the illumination pupil plane of the illumination optical system (2 to 8) during annular illumination. The present invention is exemplarily applied to the above.

  Next, in the adjustment method of the present embodiment, the product of the light intensity at each point in the region of the light intensity distribution having a substantially annular shape measured in the measurement step S1 and the distance between the predetermined center point and each point is a region. To obtain a first moment value (S2). Specifically, as shown in FIG. 4, polar coordinates (r, θ) centered on the optical axis AX as a predetermined center point with respect to the light intensity distribution 40 having a substantially annular shape measured in the measurement step S <b> 1. Set. Here, r is a half coordinate of polar coordinates, and θ is a radial angle of polar coordinates.

  In this case, the light intensity I (r, θ) is not uniform (constant) over the entire region S in the substantially annular light intensity distribution 40, and for example, a comparison of changes as shown in FIG. Distribution close to a large Gaussian shape. In step S2, the light intensity I (r, θ) at each point in the region S of the substantially annular light intensity distribution 40 and the distance r between the optical axis AX and each point are calculated by the following equation (1). The product r × I (r, θ) is integrated over the entire region S (r = r1 to r2, θ = 0 to 2π) to obtain the first moment value PM.

Next, in the adjustment method of the present embodiment, the light intensity I (r, θ), the optical axis AX, and each point at each point in the region S of the light intensity distribution 40 having a substantially annular shape measured in the measurement step S1. Is obtained by integrating the product r ² × I (r, θ) of the distance r squared r ^{2 over} the entire region S (r = r1 to r2, θ = 0 to 2π). (S3). That is, in step S3, the second moment value SM is obtained by the following equation (2).

  Furthermore, in the adjustment method of the present embodiment, the uniform annular zone shape that is effectively equivalent to the substantially annular zone light intensity distribution 40 measured in the measurement step S1 based on the primary moment value PM obtained in the step S2. Light intensity distribution, that is, an outer diameter (radius) Ro and an inner diameter (radius) of a uniform (top-hat type) light intensity distribution 41 with an annular shape centering on the optical axis AX as shown in FIG. An intermediate diameter (radius) Rm corresponding to the average value with Ri is obtained (S4). Next, based on the second moment value SM obtained in step S3, it corresponds to the difference (Ro-Ri) between the outer diameter Ro and the inner diameter Ri of the uniform light intensity distribution 41 in the annular shape centered on the optical axis AX. A width B to be obtained is obtained (S5).

  In other words, in steps S4 and S5, the substantially annular light intensity distribution measured in the measurement step S1 based on the primary moment value PM obtained in step S2 and the secondary moment value SM obtained in step S3. Main parameters of a uniform light intensity distribution 41 having an annular shape that is effectively equivalent to 40, that is, an outer diameter Ro, an inner diameter Ri, an annular ratio (Ri / Ro), and the like can be obtained. Incidentally, the primary moment value PM corresponds to the dispersion of the light intensity distribution 40 having a substantially annular shape, and the secondary moment value SM corresponds to the average distance from the optical axis AX of the light intensity distribution 40 having a substantially annular shape. ing.

  Finally, in the adjustment method of the present embodiment, the light intensity distribution on the illumination pupil plane of the illumination optical system (2 to 8) is adjusted based on the evaluation result of the evaluation step (S2 to S5) (S6). Specifically, in the adjustment step S6, the illumination optical system (2) is effectively equivalent to the substantially annular light intensity distribution 40 on a surface optically conjugate with the illumination pupil plane of the illumination optical system (2 to 8) (in other words, the illumination optical system ( 2-8) The main parameters (outer diameter, inner diameter, and annular zone) of the uniform annular light intensity distribution 41 that is effectively equivalent to the substantially annular annular light intensity distribution (secondary light source) on the illumination pupil plane of 2-8) Ratio, etc.) and an optical system equivalent to a uniform light intensity distribution with an effective equivalent annular zone shape having a desired parameter in response to an input set value to the exposure apparatus as a secondary light source (2 to 8) The optical adjustment is performed so that the illumination pupil plane is formed.

  As described above, in the present embodiment, the light intensity distribution (secondary light source) formed on the illumination pupil plane of the illumination optical device (1-8) is effective in consideration of not only the outer shape but also the non-uniform distribution. Therefore, the light intensity distribution can be evaluated as an equivalent and uniform light intensity distribution, and as a result, the light intensity distribution on the illumination pupil plane can be adjusted with high accuracy. Therefore, in the exposure apparatus of the present embodiment, it is possible to faithfully project and expose a fine pattern using the illumination optical apparatus (1 to 9) in which the light intensity distribution on the illumination pupil plane is adjusted with high accuracy.

  In other words, in the present embodiment, unlike the conventional technique that considers only the outer shape of the light intensity distribution (secondary light source) formed on the illumination pupil plane, it is effectively equivalent considering the non-uniform distribution in addition to the outer shape. The imaging characteristics are correctly evaluated based on the shape and size of the secondary light source evaluated as a uniform light intensity distribution (external diameter, internal diameter, annular ratio, etc. in the case of an annular secondary light source) Therefore, it is possible to satisfactorily suppress the variation in the resolution line width between the two different exposure apparatuses, and to achieve good matching between the units.

  In addition, in order to accurately project and expose a fine pattern while suppressing variation in resolution line width satisfactorily, in the adjustment step S6, each point on the image plane of the projection optical system PL has an effectively equivalent annular zone shape. It is preferable to adjust the light intensity distribution formed on the illumination pupil plane so that the variation in the outer diameter Ro of the uniform light intensity distribution 41 is within ± 1.5%. Similarly, in the adjustment step S6, the variation in the inner diameter Ri of the uniform light intensity distribution 41 with an effectively equivalent annular zone shape at each point on the image plane of the projection optical system PL is within ± 1.5%. It is preferable to adjust the light intensity distribution formed on the illumination pupil plane.

  In the above-described embodiment, the present invention is applied to the evaluation and adjustment of the light intensity distribution having a substantially annular shape. However, the present invention is not limited to this, and the present invention can be applied to evaluation and adjustment of, for example, a substantially circular light intensity distribution or a multipolar light intensity distribution. In particular, the evaluation and adjustment of the light intensity distribution of the circular shape is similar to the evaluation and adjustment of the light intensity distribution of the annular shape, and is simpler than the case of the light intensity distribution of the annular shape.

  That is, the evaluation of the substantially circular light intensity distribution measured by the measuring device 10 corresponding to the circular secondary light source formed on the illumination pupil plane of the illumination optical system (2 to 8) during normal circular illumination and In the case of adjustment, the product r × I (r, θ) of the light intensity I (r, θ) at each point in the region S of the light intensity distribution having a substantially circular shape and the distance r between the optical axis AX and each point is obtained. The first moment value PM is obtained by integrating over the entire region S. Then, based on the first moment value PM, the outer diameter of the uniform light intensity distribution is obtained in a circular shape that is effectively equivalent to the measured light intensity distribution having a substantially circular shape.

  In addition, an effective equivalent circular shape having a desired outer diameter in response to an input set value to the exposure apparatus and a uniform light intensity distribution as a secondary light source on the illumination pupil plane of the illumination optical system (2-8) Optical adjustments are made to form. In this case, a uniform light intensity distribution with an effective equivalent circular shape for each point on the image plane of the projection optical system PL in order to accurately project and expose a fine pattern while suppressing variations in resolution line width. It is preferable to adjust the light intensity distribution formed on the illumination pupil plane so that the variation in the outer diameter of the illumination pupil is within ± 1.5%.

  Next, as an example of evaluation and adjustment of a multipolar light intensity distribution, measurement is performed corresponding to a secondary secondary light source formed on the illumination pupil plane of the illumination optical system (2 to 8) at the time of bipolar illumination. Evaluation and adjustment of the bipolar light intensity distribution measured by the apparatus 10 will be described. In this case, as shown in the flowchart of FIG. 6, for example, using the measuring device 10, a surface optically conjugate with the illumination pupil plane of the illumination optical system (2 to 8) based on the light that has passed through the projection optical system PL. The dipole light intensity distribution at is measured (S11).

  Subsequently, the light intensity at each point in the region of the dipolar light intensity distribution measured in the measurement step S11 is integrated in the circumferential direction with respect to the predetermined center point, and light in an annular shape centered on the predetermined center point. An intensity distribution is obtained (S12). Specifically, as shown in FIG. 7A, with respect to the dipolar light intensity distribution 70 measured in the measuring step S11, polar coordinates (r, centered on the optical axis AX as a predetermined center point). θ) is set. Here, r is a half coordinate of polar coordinates, and θ is a radial angle of polar coordinates.

  In this case, in the pair of substantially circular light intensity distributions 70a and 70b constituting the bipolar light intensity distribution 70, the light intensity I (r, θ) is not uniform (constant) over the entire region. For example, it has a distribution close to a Gaussian shape having a relatively large change. In step S12, the light intensity I (r, θ) at each point in the region of the dipolar light intensity distribution 70 is changed in the circumferential direction (θ = 0 to 2π) with respect to the optical axis AX by the following equation (3). Integration is performed to obtain an annular light intensity distribution 71 (see FIG. 7B) centered on the optical axis AX.

The annular light intensity distribution 71 obtained by the circumferential integration of Expression (3) has a distribution I _A (r) that changes only in the radial direction without changing in the circumferential direction around the optical axis AX. This is a light intensity distribution in a ring-shaped shape that is rotationally symmetric with respect to the optical axis AX. Thus, by applying the evaluation steps S2 to S5 described above to the annular light intensity distribution 71 obtained by the circumferential integration, it is effectively equivalent to the measured dipolar light intensity distribution 70. The outer diameter Ro, the inner diameter Ri, and the like of the dipolar and uniform light intensity distribution 72 (see FIG. 7C) can be obtained.

  Here, the outer diameter Ro and the inner diameter Ri of the effectively equivalent bipolar and uniform light intensity distribution 72 are inscribed and inscribed in a circle circumscribing the bipolar light intensity distribution 72 with the optical axis AX as the center. Each corresponds to the radius of the circle. Specifically, a primary moment value PM is obtained for the annular light intensity distribution 71 obtained in step S12 (S13), and a secondary moment value SM is obtained for the annular light intensity distribution 71 obtained in step S12. (S14), and based on the first moment value PM, an intermediate diameter Rm corresponding to the average value of the outer diameter Ro and the inner diameter Ri of the effectively equivalent bipolar and uniform light intensity distribution 72 is obtained (S15). Based on the second moment value SM, a width B corresponding to the difference between the outer diameter Ro and the inner diameter Ri of the effectively equivalent bipolar and uniform light intensity distribution 72 is obtained (S16).

Next, the light intensity at each point in the region of the light intensity distribution of each pole constituting the bipolar light intensity distribution measured in the measurement step S11 is integrated in the radial direction with respect to the optical axis AX that is a predetermined center point. Then, the light intensity angle distribution is obtained (S17). Specifically, in step S17, the light intensity I (r at each point in the region of the light intensity distribution (70a, 70b) of each pole constituting the bipolar light intensity distribution 70 is expressed by the following equation (4). , Θ) are integrated in the radial direction (r = 0 to r3) with respect to the optical axis AX to obtain the light intensity angle distribution I _B (θ) (see FIG. 8).

Next, based on the light intensity angle distribution obtained in step 17, the angle at which the light intensity distribution of each pole of the effectively equivalent bipolar and uniform light intensity distribution is estimated from the optical axis AX as a predetermined center point Is obtained (S18). Specifically, in step S18, the angle φ at which the light intensity distribution (72a, 72b) of each pole constituting the effectively equivalent bipolar and uniform light intensity distribution 72 is viewed from the optical axis AX is set to, for example, the light intensity. Each is obtained based on the half-value width Wh of the angle distribution I _B (θ). Finally, based on the evaluation results of the evaluation steps (S13 to S18), the light intensity distribution on the illumination pupil plane of the illumination optical system (2 to 8) is adjusted (S19).

  Specifically, in the adjustment step S19, the illumination optical system (2) is effectively equivalent to the dipole light intensity distribution 70 on a plane optically conjugate with the illumination pupil plane of the illumination optical system (2 to 8). Major parameters of the dipolar and uniform light intensity distribution 72 that is effectively equivalent to the dipolar light intensity distribution (secondary light source) on the illumination pupil plane of (8) to 8) (outer diameter, inner diameter, angle of view, etc.) Referring to FIG. 4, the illumination pupil of the illumination optical system (2 to 8) has an effective equivalent bipolar and uniform light intensity distribution having a desired parameter in response to an input set value to the exposure apparatus as a secondary light source. Optical adjustment is performed so that the surface is formed.

  In the above description, the present invention is applied to the evaluation and adjustment of the light intensity distribution having a substantially annular shape, the light intensity distribution having a substantially circular shape, and the light intensity distribution having a bipolar shape. However, the present invention is not limited to this, and the present invention can be similarly applied to, for example, evaluation and adjustment of other multipolar light intensity distributions. For example, as shown in FIG. 9, in the case of a quadrupolar light intensity distribution composed of four light intensity distributions 92 to 95 centered on the optical axis AX, a method for a dipolar light intensity distribution is applied. And apply.

  Further, for example, a quadrupolar light intensity distribution composed of four light intensity distributions 92 to 95 centered on the optical axis AX and a quadrupolar light intensity distribution composed of four light intensity distributions 96 to 99 centered on the optical axis AX. In the case of an octupole-shaped light intensity distribution constituted by the light intensity distribution, the inner four-pole light intensity distribution (92 to 95) and the outer four-pole light intensity distribution (96 to 99) The methods for the polar light intensity distribution may be applied and applied.

  Further, for example, a pentapolar light intensity distribution constituted by a light intensity distribution 91 on the optical axis AX and a quadrupolar light intensity distribution composed of four light intensity distributions 92 to 95 centered on the optical axis AX. In this case, the light intensity distribution 91 on the optical axis AX is applied with a technique for a light intensity distribution having a substantially circular shape, and the light intensity distribution with a quadrupolar shape (92 to 95) is applied with a technique for a light intensity distribution with a bipolar shape. Apply and apply.

  Further, for example, a light intensity distribution 91 on the optical axis AX, a quadrupolar light intensity distribution composed of four light intensity distributions 92 to 95 centered on the optical axis AX, and four lights centered on the optical axis AX. In the case of a nine-pole light intensity distribution constituted by a quadrupole light intensity distribution consisting of intensity distributions 96 to 99, the light intensity distribution 91 on the optical axis AX has a method for a light intensity distribution having a substantially circular shape. Applied to the inner quadrupole light intensity distribution (92 to 95) and the outer quadrupole light intensity distribution (96 to 99) by applying the method for the dipolar light intensity distribution, respectively. do it.

  Furthermore, the light intensity having various forms can be obtained by appropriately combining the technique for the light intensity distribution having a substantially annular shape, the technique for the light intensity distribution having a substantially circular shape, and the technique for the light intensity distribution having a bipolar shape. The present invention can be applied to distribution evaluation and adjustment.

  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 to 8) 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 8) 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 (1-8), and illumination optics. The light intensity distribution can be evaluated in the same manner for only the devices (1 to 8). 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. 10 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. 10, 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. 11, in a pattern forming process 401, a so-called photolithography process is performed in which a mask pattern is transferred and exposed to a photosensitive substrate (such as a glass substrate coated with a resist) using the exposure apparatus of the above-described embodiment. . 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 the 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 of the substantially ring-shaped shape measured using the measuring apparatus of this embodiment. It is a figure which shows a mode that the polar coordinate (r, (theta)) centering on an optical axis was set with respect to the substantially ring-shaped light intensity distribution measured using the measuring apparatus of this embodiment. FIG. 5 is a diagram illustrating a procedure for evaluating the substantially annular light intensity distribution shown in FIG. 4 as a uniform light intensity distribution with an effectively equivalent annular shape. It is a flowchart which shows schematically the process of the adjustment method containing the evaluation method of the dipolar light intensity distribution measured using the measuring apparatus of this embodiment. It is a figure explaining the evaluation method of bipolar light intensity distribution measured using the measuring device of this embodiment. It is a figure which shows roughly the light intensity angle distribution obtained by carrying out radial direction integration of the light intensity distribution of each pole which comprises bipolar light intensity distribution. It is a figure explaining application of this invention with respect to evaluation and adjustment of light intensity distributions other than two poles other than multiple poles. 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 Condenser optical system 7 Mask blind 8 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 (18)

A method of evaluating a substantially circular light intensity distribution formed on a predetermined surface as a uniform light intensity distribution with a circular shape that is effectively equivalent to the substantially circular light intensity distribution,
Integrating a product of the light intensity at each point in the region of the light intensity distribution having a substantially circular shape and a distance between the predetermined center point and each point over the entire region to obtain a first moment value; ,
And a step of obtaining an outer diameter of the uniform light intensity distribution with the circular shape centered on the predetermined center point based on the first moment value. A method of evaluating a substantially annular light intensity distribution formed on a predetermined surface as a uniform light intensity distribution with an annular shape that is effectively equivalent to the substantially annular light intensity distribution,
Integrating a product of the light intensity at each point in the region of the substantially annular light intensity distribution and the distance between the predetermined center point and each point over the entire region to obtain a first moment value; When,
A second moment is obtained by integrating the product of the light intensity at each point in the region of the light intensity distribution having the substantially annular shape and the square of the distance between the predetermined center point and each point over the entire region. A process for determining a value;
Obtaining an intermediate diameter corresponding to an average value of an outer diameter and an inner diameter of a uniform light intensity distribution in the annular shape centered on the predetermined center point based on the first moment value;
Obtaining a width corresponding to a difference between an outer diameter and an inner diameter of a uniform light intensity distribution in the annular shape centered on the predetermined center point based on the second moment value. Evaluation method to do. A method for evaluating a predetermined light intensity distribution formed on a predetermined surface as a uniform light intensity distribution that is effectively equivalent to the predetermined light intensity distribution,
Integrating the product of the light intensity at each point in the region of the predetermined light intensity distribution and the distance between the predetermined center point and each point over the entire region to obtain a first moment value;
Obtaining an outer diameter of the uniform light intensity distribution centered on the predetermined center point based on the first moment value. The product of the light intensity at each point in the region of the predetermined light intensity distribution and the square of the distance between the predetermined center point and each point is integrated over the entire region to obtain a second moment value. Process,
4. A step of obtaining a width corresponding to a difference between an outer diameter and an inner diameter of the uniform light intensity distribution centered on the predetermined center point based on the second moment value. Evaluation method described in 1. A method of evaluating a multipolar light intensity distribution formed on a predetermined surface as a multipolar and uniform light intensity distribution that is effectively equivalent to the multipolar light intensity distribution,
Integrating a light intensity at each point in the region of the multipolar light intensity distribution in a circumferential direction with respect to a predetermined center point to obtain an annular light intensity distribution centered on the predetermined center point;
Integrating a product of light intensity at each point in the zone-shaped light intensity distribution region and the distance between the predetermined center point and each point over the entire region to obtain a first moment value; When,
A second moment value is obtained by integrating the product of the light intensity at each point in the region of the annular light intensity distribution and the square of the distance between the predetermined center point and each point over the entire region. The process of seeking
Obtaining an intermediate diameter corresponding to an average value of an outer diameter and an inner diameter of the multipolar and uniform light intensity distribution around the predetermined center point based on the first moment value;
Obtaining a width corresponding to a difference between an outer diameter and an inner diameter of the multipolar and uniform light intensity distribution centered on the predetermined center point based on the second moment value. Evaluation method to do. Integrating a light intensity at each point in an area of an arbitrary unipolar light intensity distribution constituting the multipolar light intensity distribution in a radial direction with respect to the predetermined center point to obtain a light intensity angle distribution;
Obtaining an angle at which a monopolar light intensity distribution corresponding to the arbitrary single pole of the plurality of uniform light intensity distributions from the predetermined center point is obtained based on the light intensity angle distribution. The evaluation method according to claim 5, wherein: The evaluation method according to claim 6, wherein the estimated angle is obtained based on a half-value width of the light intensity angle distribution. 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. 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 adjusting step, the light intensity distribution is adjusted so that a variation in outer diameter of the uniform light intensity distribution in the annular shape is within ± 1.5% for each point on the irradiated surface. The adjustment method according to claim 9. In the adjusting step, the light intensity distribution is adjusted so that a variation in inner diameter of the uniform light intensity distribution in the annular shape is within ± 1.5% for each point on the irradiated surface. The adjustment method according to claim 9 or 10. In the adjusting step, the light intensity distribution is adjusted so that a variation in outer diameter of the uniform light intensity distribution in the circular shape is within ± 1.5% for each point on the irradiated surface. The adjustment method according to claim 9. The light intensity distribution in a surface optically conjugate with the illumination pupil plane is measured based on the light that has passed through the irradiated surface in the measurement step. The adjustment method described. An illumination optical apparatus adjusted by the adjustment method according to claim 7. An exposure apparatus comprising the illumination optical apparatus according to claim 14, 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;
16. The exposure apparatus according to claim 15, wherein, in the measuring 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. An exposure method, comprising: exposing a mask pattern onto a photosensitive substrate using the illumination optical apparatus according to claim 14. A projection step of forming an image of the pattern of the mask on the photosensitive substrate using a projection optical system;
18. The exposure method according to claim 17, wherein, in the measuring 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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