JP2006078283A - Position measuring device, aligner provided with the position-measuring device and aligning method using the position-measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provided a position-measuring device etc., that is improved in the throughput of wafer alignment, while maintaining precision of measurement. <P>SOLUTION: The position measuring device comprises the search measurement system 23 provided with the CCD camera 21 and NA diaphragm 22 for search measurement for conducting rough measurements on the alignment mark AM on the wafer W; the fine measurement system 28 provided with the CCD camera 25 and 26 and the NA diaphragm 27 for fine measurement for precisely measuring the alignment mark AM; and the observation measuring system 31 provided with the CCD camera 30 for the observation for observing the surface of the wafer W, including the wafer mark AM. The diaphragms a and b of the NA diaphragm 22 and the diaphragm a and b of the NA diaphragm 27 are the same in shape but are different in the number of apertures. By changing the combinations of the diaphragms a and b of the NA diaphragm 22 and the aperture diaphragms A, B, C and D of the σ diaphragm 62, measurement conditions can be changed variously, thereby the search measurement error can be surely avoided. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a position measuring apparatus that improves the throughput while maintaining measurement accuracy when imaging a position measuring pattern and measuring the position of the position measuring pattern, and an exposure apparatus including the position measuring apparatus. The present invention relates to an exposure method using this position measuring apparatus.

  In general, in a lithography process for manufacturing a semiconductor, an exposure apparatus (stepper or scanner) is used, and various mask patterns (reticle patterns) are repeatedly exposed on a shot area of a wafer as an exposure substrate to develop, etch, A complex circuit is formed while performing chemical processing.

  2. Description of the Related Art Conventionally, an image processing type position measuring apparatus has been used in a stepper wafer alignment system. In such an apparatus, for example, an image of a position measurement pattern (alignment mark) formed on a wafer is picked up using a bright field microscope, and the obtained measurement signal is image-processed to obtain a position measurement pattern. Is detected (alignment measurement). For example, as a wafer alignment system for a stepper, an FIA (Field Image Alignment) sensor is used.

  In the above-described exposure process, the FIA sensor detects alignment marks formed in association with arbitrary shot areas on the resist-coated wafer, determines each position by image processing, and performs statistical processing on the wafer. The overall position and rotation amount are calculated. In response to the result, the stepper performs a stepping exposure operation while driving the wafer stage to accurately position the wafer (wafer alignment), and forms a reticle pattern on the position of each desired shot area on the wafer.

  In order to expose an exposure pattern having a very narrow line width, this superposition needs to be performed with an accuracy of several nanometers (nanometers). Therefore, further accuracy is required for positioning accuracy (alignment accuracy).

  In the stepper, in order to efficiently mass-produce semiconductors, the performance of how many wafers can be exposed per hour (throughput) is very important. Therefore, in addition to having high alignment accuracy, FIA is required to be able to perform alignment measurement at high speed.

  In the alignment measurement described above, first, search measurement is performed to measure the approximate position of the alignment mark on the wafer (relative positional relationship between the wafer and the measurement visual field of the alignment measurement system), and then based on the measurement result of the search measurement. Fine measurement to measure the alignment mark with high accuracy.

  Search measurement is important in that it provides correction position information for alignment marks for the next fine measurement. If this measurement is not performed smoothly, the next fine measurement may be affected. . For example, depending on the type of alignment mark as a measurement target and the illumination conditions for illuminating the alignment mark for measurement, it takes time to detect the alignment mark during search measurement, and the process proceeds to the next fine measurement. It may take a long time to complete, and in the worst case, the alignment mark cannot be detected, and the apparatus may stop during the measurement. This is a factor that reduces the throughput described above.

  The present invention has been made in view of such circumstances, and a position measurement apparatus that maintains the measurement accuracy and improves the throughput of the wafer alignment, an exposure apparatus including the position measurement apparatus, and the position measurement apparatus. An object is to provide an exposure method to be used.

  The position measuring apparatus according to claim 1 of the present invention that achieves the above object irradiates a position measuring pattern (alignment mark AM) formed on an object (wafer) with measurement illumination light, and performs the position measurement. A position measuring device (FIA sensor 20) for measuring the position of the object by receiving and measuring the reflected light reflected from the pattern for the object, and the reflected light reflected from the position measuring pattern is converted into the objective optical system. Light is received by the first light receiving element (search measurement CCD camera 21) via the first objective lenses 69 to 71, and the position measurement pattern is subjected to a first measurement magnification (around 20 times (for example, 19 times)). The first measurement system (search measurement system 23) that is measured in step (b) and the first light receiving element that reflects the reflected light reflected from the position measurement pattern via the objective optical system (first objective lenses 69 to 71). Different Light is received by a second light receiving element (fine measurement CCD cameras 25 and 26), and the position measurement pattern is subjected to a second measurement magnification (approximately 40 times (for example, 39 times)) higher than the first measurement magnification. A first measurement system (fine measurement system 28) for measuring the first measurement system disposed on an optical path that guides light reflected from the position measurement pattern to the first light receiving element. An imaging beam aperture stop (see FIG. 3B: NA stop 22: numerical aperture (NA) is, for example, a = 0.3, b = 0.24 to 0.3), and the second measurement system. Is a second imaging beam aperture stop (see FIG. 3B) arranged on the optical path that guides the light reflected from the position measurement pattern to the second light receiving element (see FIG. 3B: NA stop 27: numerical aperture is, for example, a = 0.5, b = 0.4 to 0.5), and the first and second imaging light beams are opened. Wherein the numerical aperture of the diaphragm are different.

  A plurality of restricting portions (σ aperture stop 62: FIG. 3) arranged on the illumination light path for guiding the measurement illumination light to the position measurement pattern and restricting the measurement illumination light to different numerical apertures or shapes. (A) Reference: illumination with numerical aperture (NA) or σ value of illumination, for example, A = 0.4, B = 0.12, C = 0.24, D = 0.3-0.4) A light beam aperture stop (σ stop) is further provided, and when performing the measurement by the first measurement system, any one of the plurality of restriction portions may be selectively arranged on the illumination optical path. Preferred (claim 2).

  The reflected light reflected from the position measurement pattern is received by a third light receiving element (observation CCD camera 30) independent of the first and second light receiving elements, and the position measuring pattern is received by the first light receiving element. A third measurement system (observation measurement system 31) that measures at a third measurement magnification (approximately 5 times (for example, 4.8 times)) lower than the measurement magnification of 1 can be further provided. .

  The exposure apparatus according to claim 4 of the present invention that achieves the above object illuminates a mask pattern (reticle pattern: alignment mark) and transfers an image of the mask pattern onto an exposure substrate (wafer). A position measurement device according to any one of claims 1 to 3, wherein the position measurement pattern formed on the substrate to be exposed is measured using the position measurement device. An image of the mask pattern is transferred onto the substrate to be exposed positioned based thereon.

  The exposure method according to claim 5 of the present invention, which achieves the above object, illuminates a mask pattern (reticle pattern: alignment mark) and transfers an image of the mask pattern onto an exposure substrate (wafer). It is a method, Comprising: The position measurement pattern formed on the said to-be-exposed board | substrate is measured using the position measuring apparatus as described in any one of Claim 1 thru | or 3, It measures using the said position measuring apparatus. The image of the mask pattern is transferred onto the substrate to be exposed positioned based on the result.

  According to the position measurement apparatus of the first aspect of the present invention, the first measurement system and the second measurement system having different measurement magnifications include the first light receiving element and the second light receiving element, respectively, and have different numerical apertures. The first imaging light beam aperture stop and the second imaging light beam aperture stop are provided, and the position measurement pattern can be smoothly measured under optimum measurement conditions.

  According to the position measuring device of claim 2, the illumination light beam aperture stop is further provided, and when performing measurement in the first measurement system, one of the plurality of restricting portions is selected on the illumination optical path. Because it is possible to measure after changing the illumination conditions according to the type of position measurement pattern and selecting the optimal illumination condition, depending on the type of position measurement pattern, the effective measurement result may be It is not possible to avoid such a situation that the apparatus stops in the worst case.

  According to the position measurement apparatus of claim 3, the light is received by the third light receiving element independent of the first and second light receiving elements, and the position is measured at the third measurement magnification lower than the first measurement magnification. Since it has further the 3rd measurement system which measures the pattern for measurement, it can measure with this 3rd measurement system first, can measure with the 1st measurement system based on this measurement result, and when measuring with the 1st measurement system The measurement range can be narrowed to some extent, and as a result, the measurement time of the position measurement pattern can be shortened.

  According to the exposure apparatus according to claim 4 or the exposure method according to claim 5, since the position measurement apparatus according to any one of claims 1 to 3 is used, mask pattern overlay accuracy is ensured. In addition, it is possible to avoid a situation where the position measurement pattern cannot be effectively measured and the apparatus stops, and it is possible to improve throughput.

  Embodiments of a position measuring apparatus, an exposure apparatus including the position measuring apparatus, and an exposure method using the position measuring apparatus according to the present invention will be described below with reference to FIGS.

  FIG. 1 is a general block diagram showing an embodiment of an exposure apparatus equipped with a position measuring device (FIA (Field Image Alignment) sensor of the present invention, and FIG. 2 is a block diagram showing a detailed embodiment of the position measuring device of FIG. 3A is an explanatory view of a σ stop as an illumination aperture stop equipped in the position measuring apparatus shown in FIG. 2, and FIG. 3B is an explanatory view of an NA stop as an imaging beam aperture stop. 4 is a configuration diagram showing a light source of illumination light for measurement equipped in the position measuring device shown in FIG. 2, FIG. 5 is an explanatory view for explaining the function of the indicator plate equipped in the position measuring device shown in FIG. 6A is an enlarged view showing the σ stop arranged in the autofocus system provided in the position measuring apparatus shown in FIG. 2, FIG. 6B is an enlarged view showing the aperture stop, and FIG. FIG. 7 is an enlarged view showing a slit. FIG. 7 shows an alignment formed on a wafer as a substrate to be exposed. It is a top view which shows an example of a mark.

  First, the overall configuration and operation of an exposure apparatus equipped with the position measurement apparatus of this embodiment will be described with reference to FIG.

  In the present embodiment, the exposure apparatus 10 applies a circuit pattern as a mask pattern formed on a reticle R as a mask as an object or a substrate to be exposed via the projection optical system PL by a step-and-repeat method. This is a reduction projection type exposure apparatus that sequentially exposes and transfers each shot area of the wafer W. In FIG. 1, the X axis and the Z axis are set in parallel with the paper surface, and the Y axis is set in a direction perpendicular to the paper surface.

  In FIG. 1, the exposure light emitted from the illumination optical system 11 illuminates a reticle R as a mask with a substantially uniform illuminance. The reticle R is held on a reticle stage RS, and the reticle stage RS is supported so as to be able to move and slightly rotate in a two-dimensional plane (XY plane) on a base (not shown). A main control system 12 that controls the operation of the entire apparatus controls the operation of the reticle stage RS via the drive device 13.

  The image of the circuit pattern formed on the reticle R is projected onto each shot area on the wafer W via the projection optical system PL. Although not shown, alignment marks (position measurement patterns) for position measurement in the X-axis direction and for position measurement in the Y-axis direction (for two-dimensional measurement) are formed on the wafer W at the periphery of each shot area. ing.

  Wafer W is placed on wafer stage WST via wafer holder 14. Wafer stage WST includes an XY stage 15 for two-dimensionally positioning wafer W in a plane perpendicular to the optical axis of projection optical system PL, and wafer W in a direction parallel to the optical axis of projection optical system PL (Z-axis direction). Are constituted by a Z stage 16 that positions the wafer and a stage (not shown) that rotates the wafer W slightly.

  A movable mirror 17 is fixed on wafer stage WST (XY stage 17), and a laser interferometer 18 is arranged so as to face this movable mirror 17. Although not shown in detail, the movable mirror 17 includes a plane mirror having a reflecting surface perpendicular to the X axis and a plane mirror having a reflecting surface perpendicular to the Y axis. The laser interferometer 18 also includes two X-axis laser interferometers that irradiate the moving mirror 17 along the X axis and two laser beams that irradiate the moving mirror 17 along the Y axis. It is composed of a Y-axis laser interferometer. The X coordinate and Y coordinate of wafer stage WST are measured by one laser interferometer for X axis and one laser interferometer for Y axis. Further, the rotation angle of wafer stage WST is measured by the difference between the measurement values of the two laser interferometers for the X axis.

  Information on the X coordinate, the Y coordinate, and the rotation angle measured by the laser interferometer 18 is sent to the main control system 12, and the main control system 12 monitors the sent coordinates and drives the wafer stage WST via the drive system 19. Control the positioning operation. Although not shown, an interferometer system similar to that on the wafer side is also provided on the reticle side.

  Next, features of the present invention will be described.

  An FIA sensor 20 is disposed on the side of the projection optical system PL. The FIA sensor 20 measures alignment marks AM (see FIG. 7) arranged for each shot area of the wafer W, sends the measurement results to the main control system 12, and performs arithmetic processing in the main control system 12. Then, the positioning operation of wafer stage WST is controlled via drive system 19 to perform positioning (alignment) of wafer W. After this positioning, an exposure process is performed in which the pattern of the reticle R is transferred to each shot area of the wafer W on the wafer stage WST via the projection optical system PL.

  As shown in FIG. 2, the FIA sensor 20 includes a search measurement CCD camera 21 as a first light receiving element, an NA aperture 22 as a first imaging light beam aperture stop, and the like, and a first measurement magnification (around 20 times). (For example, 19 times)), a search measurement system 23 as a first measurement system for measuring the approximate position of the alignment mark AM on the wafer W, a fine measurement CCD camera 25 as a second light receiving element, 26 and an NA stop 27 as a second imaging light beam aperture stop, and the like, which measures the alignment mark AM with high accuracy at a measurement magnification higher than the first measurement magnification (around 40 times (for example, 39 times)). A third measurement system 28 includes a fine measurement system 28 and an observation CCD camera 30 as a third light receiving element, and the like, and observes a wide range of the surface of the wafer W including the alignment mark AM. An observation measurement system 31 as a measurement system, and a measurement illumination optical system 33 that illuminates the alignment mark AM on the wafer W with broadband light for the search measurement system 23, the fine measurement system 28, and the observation measurement system 31 are provided. . Further, the FIA sensor 20 includes an autofocus system 35 for adjusting the imaging positions of the search measurement system 23, the fine measurement system 28, and the observation measurement system 31.

  First, the measurement illumination optical system 33 that illuminates the alignment mark AM with broadband light will be described.

  The measurement illumination optical system 33 includes a light source unit 36 shown in FIG. The light source unit 36 includes a halogen lamp 37 and takes illumination light (for example, broadband light of 530 nm to 800 nm) from the halogen lamp 37 from two directions (left and right directions in FIG. 4).

  Illumination light taken from one side (left direction in FIG. 4) is branched by the first branching section 38, and one of the illumination lights is further branched by the second branching section 39, and the light transmission system of the autofocus system 35 is split. Guided to light guides 56 and 57.

  The other illumination light is combined with the illumination light from the other of the halogen lamps 37 (right direction in FIG. 4) at the third branch portion 40 and guided to the light guide 41. The illumination light emitted from the end face of the light guide 41 passes through the relay lens 42, the wavelength selection filter 43, and the neutral density filter (ND filter) 44 for selecting the attenuation factor, and further passes through the dichroic mirror 45. In this dichroic mirror 45, infrared light (for example, 870 nm infrared light) emitted from the infrared LED 46 and passed through the collimating lens 47 is synthesized. The synthesized illumination light enters the light guide 50 or 51 via the relay lens 48. A switchable mirror 52 is disposed on the optical path immediately before (upstream side) the light guides 50 and 51. When the mirror 52 is retracted from the optical path and does not pass through the mirror 52, the light guide 50 starts. The light is guided to the light guide 53 for fine search system illumination. When the mirror 52 is advanced in the optical path and passes through the mirror 52, the light guide 51 enters the light guide 54 for low magnification observation illumination.

  The wavelength selection filter 43 can change the selected wavelength by moving in a direction orthogonal to the optical axis. For example, a filter unit that transmits light without selecting a wavelength, a filter unit that transmits light of 530 nm to 610 nm, a filter unit that transmits light of 600 nm to 710 nm, and a filter unit that transmits light of 700 nm to 800 nm are provided. The illumination wavelength can be selected by switching and arranging any one of these four filter units on the optical axis. Similarly, the neutral density filter 44 can move in a direction orthogonal to the optical axis to change the attenuation factor.

  The light source unit 36 is equipped with a halogen lamp 58 having the same configuration as the halogen lamp 37. This halogen lamp 58 is used in an autofocus mechanism (as detection light used in the focus detection unit) for detecting the focus state between the imaging surface of the projection optical system PL and the wafer surface. That is, as shown in FIG. 1, the illumination light is irradiated from the halogen lamp 58 onto the surface of the wafer W, the reflected light is received by the CCD camera 60 which is a light receiving element, and this is processed by the main control system 12, A control signal is sent to a drive system (not shown) of the projection optical system PL, and the lens in the projection optical system PL is moved on the optical axis by the drive system to adjust the imaging position.

  Illumination light guided to a light guide (optical fiber) 53 for fine search system illumination exits from the exit end of the light guide 53 and passes through a σ stop 62 as an illumination beam aperture stop, and passes through a condenser lens 63. The illumination field stop 64 is illuminated. The illumination light that has passed through the illumination field stop 64 is reflected by the half prism 65, then passes through the half prism 66 and the relay lens 67, is reflected by the half prism 68, and passes through the first objective lenses 69 to 71 and the index plate 72. The wafer W is illuminated.

  As shown in FIG. 3A, the σ stop 62 has an aperture stop A that has no stop and whose NA (numerical aperture) of illumination is regulated by the opening (for example, 0.4) of the exit end of the light guide 53. An aperture stop B whose illumination NA is smaller than the exit end opening of the light guide 53 (for example, 0.12), and an illumination NA larger than that of the aperture stop B and smaller than the exit end opening of the light guide 53 (For example, 0.24) An aperture stop C and an aperture stop D whose illumination NA is an annular stop (for example, an annular stop having an inner diameter of 0.3 and an outer diameter of 0.4) are orthogonal to the optical axis. It is possible to select the aperture stops A to D by moving in the moving direction, change the shape of the stop or the aperture size as appropriate, and change the illumination conditions.

  When search measurement is performed by the search measurement system 23, one of the aperture stops A to D is selected and the illumination condition is changed. The reason why the aperture stops A to D are selected in this way is to set a measurement condition for avoiding a search measurement error caused by a low image contrast when performing search measurement and obtaining an optimum measurement signal. . The aperture stops A to D are also selected depending on the level difference of the alignment mark AM.

  When fine measurement is performed by the fine measurement system 28, the aperture stop A in the σ stop 62 is basically selected, but the aperture stops B, C, and D may be selected. That is, large σ illumination with the aperture stop A selected is fundamental, and in some cases, small σ illumination with the aperture stop B selected, medium σ illumination with the aperture stop C selected, and annular illumination with the aperture stop D selected (dark field) The illumination of the alignment mark AM is performed by any one of (illumination).

  In the search measurement and fine measurement, the illumination light is guided to the alignment mark AM on the wafer W through the same optical path. In the search measurement and the fine measurement, the selection of the aperture stops A to D of the σ stop 62 may be the same.

  Next, the illumination light guided to the light guide 54 for observation illumination with low magnification will be described. The illumination light guided to the observation illumination light guide 54 is emitted from the exit end of the light guide 54 and then illuminates the illumination field stop 76 via the condenser lens 74 and the mirror 75. The illumination light having passed through the illumination field stop 76 passes through the half prism 65 and the relay lens 67 after passing through the half prism 65 in the same manner as the illumination light guided to the light guide 53 for fine search system illumination. The light is reflected by the prism 68 and passes through the first objective lenses 69 to 71 and the index plate 72 to illuminate the wafer W.

  Next, the search measurement system 23, the fine measurement system 28, and the observation measurement system 31 that measure the position of the image of the alignment mark AM from the reflected light reflected from the alignment mark AM will be described.

  First, the observation measurement system 31 for observing the surface of the wafer W including the alignment mark AM will be described. The light reflected by the wafer W follows the same path as the illumination light in the reverse direction, and the index plate 72 and the first objective lens 69. ˜71, half prism 68 and relay lens 67, reflected by half prism 66, and then reflected by half prism 77 to illuminate field stop 79. The light that has passed through the field stop 79 is reflected by the mirror 80, passes through the relay lens 81, the NA stop 82, the relay lens 83, and the infrared cut filter 84 and enters the observation CCD camera 30. The observation CCD camera 30 photoelectrically converts an image of reflected light from the surface of the wafer W and sends this signal to the main control system 12 for signal processing. Thereby, information in a wide range of the surface of the wafer W can be obtained.

  Next, the search measurement system 23 will be described. The light reflected by the wafer W follows the same path as the observation measurement system 31, is reflected by the half prism 66, and reaches the half prism 77, but is transmitted through the half prism 77. Then, the field stop 86 is illuminated. The light that has passed through the field stop 86 enters the search CCD camera 21 via the relay lens 87, the NA stop 22, the relay lens 88, and the infrared cut filter 89. The search CCD camera 21 photoelectrically converts the reflected light image of the alignment mark AM, sends this signal to the main control system 12, and performs signal processing in the main control system 12 to calculate the position of the alignment mark AM.

  Here, as shown in FIG. 3B, the NA stop 22 has, for example, a stop (normal opening stop) a having a numerical aperture (NA) of 0.3 and a stop b (ring) of 0.24 to 0.3. It is possible to change the illumination condition by changing the shape by moving in a direction orthogonal to the optical axis. The apertures a and b of the NA aperture 22 have the same shape as the apertures a (numerical aperture 0.5) and b (numerical aperture 0.4 to 0.5) of the NA aperture 27 provided in the fine measurement system. However, the numerical aperture is different.

  By changing the combination of the diaphragms a and b of the NA diaphragm 22 and the aperture diaphragms A, B, C and D of the σ diaphragm 62 described above, various measurement conditions can be changed. For example, large σ measurement in which A / a is selectively arranged, small σ measurement in which B / a is selectively arranged, medium σ measurement in which C / a is selectively arranged (these are bright field measurements), D / a Are dark field measurement in which C / b is selectively arranged, and annular dark field measurement in which C / b is selectively arranged.

  In the case of B / a, which is a small σ measurement, the contrast of the image can be increased and the edge of the measurement signal becomes sharp. However, if the image becomes too sharp, ringing occurs (the swell of the signal waveform is large), and it is difficult to determine which edge should be collected, and image signal processing becomes difficult. In such a case, C / a which is medium σ measurement is selected. As a result, the undulation of the signal waveform is suppressed, so that the image signal processing is facilitated.

  In the search measurement, A / a which is basically a large σ measurement is selected. This is because in the fine measurement performed after the search measurement (as described above, the aperture stop A is selected for the σ stop 62 in the fine measurement), the σ stop 62 does not need to be switched. The speed of AM measurement can be increased, and fine measurement can be performed without changing (moving) the σ diaphragm 62, so that there is an advantage that measurement accuracy is not adversely affected. It is.

  D / a, which is dark field measurement, has a large dark field effect and is effective when dark but has a low step pattern. However, when this is dark, a pattern may be seen when switching to C / b, which is annular dark field measurement.

  As described above, in the present embodiment, in the search measurement, the illumination condition and the measurement condition are changed by changing the combination of the aperture stops a and b of the NA stop 22 and the aperture stops A, B, C and D of the σ stop 62. By making various changes, search measurement errors are surely avoided, and any type of alignment mark AM (for example, the height of the step pattern) can be measured under optimal illumination conditions and measurement conditions. It is like that.

  Next, the fine measurement system 28 that measures the position of the alignment mark AM with high accuracy will be described. In the fine measurement, unlike the above-described observation measurement and search measurement, the index plate 72 is used. As shown in FIG. 5, the index plate 72 is an index pattern 72a in which dot patterns are two-dimensionally arranged on the upper surface (the surface away from the wafer W) as a reference for measuring the position of the image of the alignment mark AM. Is formed, and an infrared reflection film 72b that reflects only the infrared light and transmits the white illumination light of the halogen lamp 37 is formed on the lower surface (the surface close to the wafer W). In the indicator plate 72, after the infrared light is repeatedly reflected by the infrared reflecting film 72b, the indicator pattern 72a is illuminated with the infrared light. The infrared light reflected by the index pattern 72 a is emitted toward the first objective lenses 69 to 71 together with the white light reflected from the wafer W. As the index pattern 72a, a pattern formed with a chromium (Cr) film on a glass plate as in the conventional case may be used. However, in order to improve the signal contrast and to improve the measurement accuracy, the reflectivity is higher. It is preferable to form the index pattern 72a with a high material. Examples of such materials include platinum (Pt), aluminum (Al), gold (Au), copper (Cu), and silver (Ag).

  Since the infrared light and the white light are guided to the observation CCD camera 30 and the search measurement CCD camera 21, the infrared light portion is removed by the infrared cut filters 84 and 89 described above, and only the white light is obtained. Is incident.

  Infrared light and white light pass from the first objective lenses 69 to 71 through the half prism 68, are reflected by the mirror 90, and then pass through the second objective lens 91, the third objective lens 92, and the herbing 93, and the NA aperture 27 is illuminated. The infrared light and white light that have passed through the NA stop 27 are transmitted through the fourth objective lens 94, reflected by the mirror 95, and incident on the dichroic mirror 96. The dichroic mirror 96 is a wavelength selection mirror that transmits infrared light and reflects white light to separate infrared light and white light. The white light reflected from the dichroic mirror 96 is removed by the infrared cut filter 97, and the infrared light remaining without being separated is incident on the fine measurement CCD camera 25 and transmitted through the dichroic mirror 96. The white light remaining after being reflected by the mirror 98 is removed by the white cut filter 99 and is incident on the fine measurement CCD camera 26. The fine measurement CCD camera 25 photoelectrically converts the reflected light image of the alignment mark AM, and the fine measurement CCD camera 26 photoelectrically converts the reflected light image of the index pattern 72a and sends these signals to the main control system 12. The signal is processed by the main control system 12 to calculate the position of the alignment mark AM with reference to the index pattern 72a.

  As described above, the NA diaphragm 27 has the same shape as the NA diaphragm 22 of the search measurement system 23, but the numerical aperture of the diaphragm a is 0.5 and the numerical aperture of the diaphragm b is 0.4 to 0.5. (See FIG. 3B), the NA aperture 22 and the numerical aperture are different.

  The herbing 93 is a type capable of adjusting “vignetting” and is equipped with an electric drive mechanism. That is, the herbing 93 is a parallel flat plate that can be tilted with respect to the optical axis (rotatable about a rotation axis in a direction perpendicular to the optical axis) and is directed toward the NA aperture 27 (or from the NA aperture 27). A mechanism for moving the luminous flux in a direction perpendicular to the optical axis. This makes it possible to make adjustments to reduce the light beam vignetting (the imaging aperture stop being decentered with respect to the optical axis) (paragraph 0109 in JP-A-2002-213916, parallel to FIG. 16). Flat plate 113a).

  Next, an alignment autofocus system 35 for adjusting the imaging positions of the search measurement system 23, the fine measurement system 28, and the observation measurement system 31 will be described.

  First, the light transmission system will be described. Illumination lights emitted from the end faces of the light guides 56 and 57 are σ stops 100A and 100B (see FIG. 6A), condenser lenses 101A and 101B, and multi-slits 102A and 102B, respectively. (See FIG. 6C), after passing through the light transmitting lenses 103A and 103B, the light enters the half prism 105 through one slit of the aperture stops 104A and 104B (the slit on the right side of FIG. 6B). The light from the aperture stop 104A passes through the half prism 105, and the light from the aperture stop 104B is reflected by the half prism 105. These lights are combined in the pupil space at the aperture stop position, transmitted through the slit combining lens 107, and reflected by the field combining mirror 108 which is optically substantially conjugate with the wafer W. At the wafer conjugate position, the two multi-slit images are completely overlapped and projected onto the wafer W. At this time, as shown in the principle explanatory diagram of the alignment autofocus system 35 in FIG.

  Next, the light receiving system will be described. Of light projected onto the wafer W at a predetermined wafer projection tilt angle T, light incident from the right side in FIG. 8 is reflected from the left side, and light incident from the left side is reflected from the right side. Then, it returns to the field synthesis mirror 108 through the same optical path, and further passes through the other slit of the aperture stops 104A and 104B (the slit on the left side of FIG. 6B), and the cylindrical lens, the light receiving lenses 110A and 110B, the mirror A multi-slit image is formed on the line sensor 112 via the cylindrical lens 111 and the like. The multi-slit image that has passed through the aperture stop 104A and the multi-slit image that has passed through the aperture stop 104B are incident on the line sensor 112. Depending on the interval between the image forming positions on the line sensor 112 of these multi-slit images. The defocus amount (focus state) is measured. That is, the line sensor 112 photoelectrically converts each input image distribution and sends it to the main control system 12, and the main control system 12 calculates these image signals to obtain the interval between the image forming positions of the multi-slit images, The defocus amount is calculated from this interval. The main control system 12 drives the Z stage 16 to a position where the defocus amount becomes zero. Thereby, the above-described observation measurement, search measurement, and fine measurement are performed in a focused state.

In addition, in the case of using the multi slits 102A and 102B (see FIG. 6C) described above, the projected image of the slit is tilted unless the image plane tilt of the optical system is sufficiently good, and as a result, The interval value D0 between the left and right multi-slits 102A and 102B has a variation for each slit. Further, if there is wavefront aberration in the optical system, the left and right slit images are distorted to have different image intensity distributions (image asymmetry), or the linearity of the relationship between the focus Z and the slit image position shift amount is lost. For this reason, in this embodiment, PV (Peak
to Valley) value is within 0.5 μm, preferably within 0.1 μm on wafer W, and wavefront aberration is PV value of 0.2λ (λ = 633 nm) or less.

  The alignment autofocus system 35 performs various adjustments described below.

  FIG. 8 shows various adjustments in the alignment autofocus system 35. In the light transmission system shown on the left side of FIG. 8, the light guide is adjusted back and forth (or the condenser lens back and forth), the tilt adjustment of the position herbing (parallel plate), the light transmission focus adjustment of the light transmission lens, and the achromatic declination prism. Adjustments such as chromatic dispersion adjustment, tilt adjustment of telecentric herbing, and focus adjustment of the slit compound lens are performed. In the light receiving system shown on the right side of the figure, the received color dispersion adjustment of the achromatic deviation prism and the adjustment of sensor position herbing are performed. Etc. are adjusted.

  In the alignment autofocus system 35, telecentric adjustment (wafer projection angle T adjustment of left and right slits), slit positioning adjustment, in-plane telecentric adjustment (telecentration adjustment of each slit), and confocality (multi-slit image is conjugate with wafer surface). Various adjustments such as adjusting the slit rotation (each slit image is relatively rotated on the sensor), adjusting the sensor rotation, adjusting the slit image incident position (left and right slit image position). Is further implemented.

  A specific method for these adjustments will be described. The alignment autofocus measurement is performed using the interval D0 (pixel unit) on the line sensor at the best focus position of the slit images of the left and right multi-slits 102A and 102B and the rate R0 (focus movement amount per sensor pixel). If the current interval value is D, the current defocus amount DF is represented by DF = R0 × (D−D0). Therefore, the work is performed in a state where the interval D0 and the rate R0 are always matched by optical adjustment.

  In the best focus position setting, a reflection surface (non-pattern forming surface) having no FM (see FIG. 2) pattern is set at the best focus position of the FIA sensor 20, and the positions of the multi slits 102A and 102B are set to fine marks (FIG. 6). (C) Refer to five narrow slits located in the center: Obtained every time a large defocus occurs, and the rough image (two left and right positions in FIG. 6C) is obtained. See the wide slit: The shape of the projected image does not collapse much even if it is defocused greatly). Further, a slit interval D0 necessary for alignment autofocus measurement is obtained. At this time, if the position of the slit image on the line sensor 112 is deviated, adjustment is performed by sensor position herving (parallel plate) in the light receiving system.

  Further, the optical axis inclination is adjusted so that the rate (inclination per pixel) becomes a desired value. In this method, a non-pattern area is set at the best focus position of the FIA sensor 20, the slit Z interval is obtained by shaking the focus Z, and the rate (focus shift amount per sensor pixel) is measured and set. The fine slit rate, the rough slit rate, the rates of the fine slit portions in the multi-slits 102A and 102B, and the rates of the rough slit portions are displayed.

  If the left and right multi-slits 102A and 102B do not match the tilt amount, the shift amount of the slit image changes, so the rate value is adjusted to the correct value. For this purpose, the tilt amount T of the wafer projection optical axis of the multi-slit 102A that is the left multi-slit and the multi-slit 102B that is the right multi-slit may be adjusted. Specifically, it is adjusted by tilting a parallel plate (herving glass) for adjusting telecentric (inclination of the wafer projection optical axis) in each light transmission system of the multi slit 102A and the multi slit 102B. As a result, it is possible to accurately match the correct rate value.

  Further, focus adjustment of the left and right multi-slits 102A and 102B at the best focus position is performed. This adjusts the focus of the light transmitting lenses 103A and 103B and the slit combining lens 107. That is, as shown in the explanatory view of the focus and position adjustment method in FIG. 9A, adjustment is performed by superimposing the adjustment light / dark pattern, which is the intensity pattern of the alignment autofocus adjustment mark on the FM, on the light transmission slit. When the adjustment light / dark pattern on FM is superimposed on the light transmission slit, the signal waveform shown in FIG. FIG. 9B is an explanatory diagram for explaining a method for measuring the edge position and edge inclination of a signal, and is performed by measuring the edge position and inclination from the signal waveform. IEL and IER represent the positions of the left and right inner edges of the adjustment light / dark pattern, and OEL and OER represent the positions of the left and right outer edges of the light transmission slit. From these, the edge position of the light transmission slit and the adjustment light / dark pattern The edge position is determined. In addition, ΔIEL and ΔIER represent the inclination of the left and right inner edges of the adjustment light / dark pattern, and ΔOEL and ΔOER represent the inclination of the left and right outer edges of the light transmission slit, from which the inclination and adjustment of the edge of the light transmission slit are adjusted. The inclination of the edge of the bright and dark pattern is required.

  The image data obtained by swinging the defocus Z with a pitch based on the best focus position of the FIA sensor 20 is sequentially processed to obtain the maximum edge slope (angle) Z position of the light transmission slit and the maximum edge slope Z of the base pattern. The position is obtained (the focus position of the light transmission slit and the focus position of the light receiving system, respectively). In order to maintain the overlap between the base pattern and the light transmission slit, the base pattern is shaken with a measurement direction offset together with Z (about half the above-mentioned rate). The adjustment light / dark pattern is performed while overlapping the light transmission slit. Further, the focus adjustment is performed by adjusting the alignment auto-focus adjustment mark with the slit combining lens 107 or the light receiving lenses 110A and 110B of the respective light receiving systems. The focus adjustment of each multi-slit image is performed by the light transmission lenses 103A and 103B in each light transmission system.

  Further, the incident position of the multi-slit image on the wafer W is measured and adjusted so as to be accurately overlapped on the wafer W. This is performed by superimposing a light and dark pattern for adjustment, which is a base pattern, on the light transmission slit shown in FIG. 9, and measuring the positions of the multi slits A and B and the base pattern on the basis of a sensor by image processing. The incident positions of the multi slits A and B are adjusted so as to be the same at the best focus position of the FIA sensor 20 with respect to the background mark. As an adjusting means, it is performed by tilting a position herving which is a parallel plate of the light transmission system shown in FIG.

  Further, since color shift occurs depending on the wavelength band depending on the thickness of the photoresist applied on the wafer W, color shift adjustment is performed. Since the alignment autofocus system 35 uses light in a wide wavelength range (530 to 800 nm) as in the FIA sensor 20, although there is no color shift in the central wavelength range, color shift occurs in the long wave range and the short wave range, respectively. For this reason, a color filter that transmits only the long wave side and a color filter that transmits only the short wave side are inserted in the vicinity of the condenser lens of the illumination optical system, respectively, so that adjustment errors in the long wave and short wave are matched.

  The slit image incident position measurement on the wafer W is measured in the long wave region, and the slit image incident position relative relationship on the wafer W is measured in the short wave region, so that there is no color shift of the wafer projected image of each multi slit. Then, an achromatic declination prism (see FIG. 8) installed in each light transmission system is adjusted by rotating it around the optical axis. Achromatic declination prisms are made by joining two declination prisms made of glass material. The emission angle is almost zero at the center wavelength of the wavelength region, and for light in the long wave region and short wave region, It is an optical element that generates a deflection angle in the positive direction and the negative direction, respectively. By such adjustment, it is possible to eliminate the color shift of the projected slit image.

  Further, at the best focus position of the FIA sensor 20, the deviation due to the color of the reference slit interval D0 is measured in a state where the illumination light is in the long wave region and the short wave region. This deviation is made sufficiently small by rotating the achromatic declination prism (see FIG. 8) installed in the light receiving system about the optical axis.

  In the FIA sensor 20 described above, in order to measure alignment marks of various sizes, the transmitted wavefront aberration in the vicinity of the optical axis is good, and the transmitted wavefront aberration in the periphery is sufficiently good. This is especially true when coma is large. When the line width, reflectivity, pitch, level difference, etc. of the mark change, there is an effect that lateral deviation occurs in the measurement results. If it is not uniform, the horizontal shift phenomenon occurs when the mark size or pattern changes. For example, the wavefront aberrations of the objective lenses 69 to 71, 91, 92, and 94 on the optical path from the wafer W of the fine measurement system 28 to the CCD cameras 25 and 26 for fine measurement are reduced over the entire fine measurement region. Yes. Thereby, alignment accuracy can be improved.

  Next, related items of the FIA sensor 20 will be described. If distortion remains in the optical system of the FIA sensor 20, a lateral shift occurs in the measurement result when the measurement position of the alignment mark AM is shifted. For this reason, in the present embodiment, not only the distortion in the optical system but also the minute image distortion caused by the minute waviness of the polished surface is suppressed.

In this embodiment, the FIA sensor 20 has axial chromatic aberration and lateral chromatic aberration sufficiently small over the wide wavelength range of 530 to 800 nm, and other aberrations are also good. When the (deviation amount from the vertical axis of the optical axis) is large, when the wafer W is defocused, lateral deviation occurs in the measurement result, so that the telecentricity is good at all points including off-axis points in the measurement area. It is preferable to do.

  In the present embodiment, the camera rotation correction is performed in the CCD cameras 25 and 26 for fine measurement. For example, the wafer stage WST is set so that the alignment mark AM is placed in the upper half and the lower half of the measurement area, and the fine measurement CCD camera 25, based on the horizontal shift amount of the measurement result and the vertical shift amount of the alignment mark AM, 26 rotations are determined and corrected.

  Further, in this embodiment, as shown in FIG. 10, the entire optical path of the fine measurement system 28 is covered and sealed by the upper unit cover 120 and the lower unit cover 121, thereby suppressing the influence of air fluctuations in the optical system. Yes.

  The fine measurement CCD cameras 25 and 26 (including the infrared LED 46 (see FIG. 4), etc.) (including the infrared LED 46 (see FIG. 4)), which are heat sources, are disposed in the upper unit cover 120 and sealed. The heat generated from the wafer W is prevented from being transmitted to the periphery of the wafer W. Further, a heat sink pump 122 filled with a refrigerant is disposed in the upper unit cover 120 so that the temperature in the upper unit cover 120 does not rise due to heat generated from the CCD cameras 25 and 26 for fine measurement. Adjustments are being made. Although not shown, the fourth unit lens 94, mirror 95, fine measurement CCD cameras 25 and 26, etc. are integrated in the upper unit cover 120 to suppress measurement errors due to vibration. .

  Further, in this embodiment, as shown in FIG. 11, an inspection pattern 125 such as a step pattern is formed on the FM itself, and offset management with respect to the original wafer is performed.

  Conventionally, optical characteristics of a position detection device (FIA sensor) using an inspection wafer provided with a predetermined pattern such as a phase (step) pattern (typically, aberrations such as spherical aberration and coma aberration, luminous flux vignetting). (For example, the imaging aperture stop is decentered asymmetrically with respect to the optical axis to block the light beam)) (for example, JP-A-2002-213916). In this embodiment, as shown in FIG. In addition, an inspection pattern 125 having a phase (step) pattern for measuring optical characteristics of the FIA sensor 20 as a position detection device is provided on an FM (reference plate) provided on the wafer stage WST. This eliminates the need to place the inspection wafer on or off the wafer stage WST each time the characteristics of the optical system of the position detection device are measured. Here, using a specific inspection substrate as a reference inspection substrate, the measurement result of the optical system of the position detection device using the reference inspection substrate, and the inspection pattern on the FM (reference plate) on wafer stage WST It is preferable to obtain in advance the difference from the measurement result of the optical system of the position detection apparatus using (step difference pattern or the like) as an offset value. By correcting the measurement result of the optical system of the position detection apparatus using the inspection pattern on the FM (reference plate) on the wafer stage WST with the offset value, highly accurate measurement can be performed.

  In this embodiment, it is desirable to reduce the influence on the throughput as much as possible by shortening the switching time of the switching mechanisms such as the σ diaphragm 62 and the NA diaphragms 22 and 27 as much as possible.

  In the illumination optical system 33, the fiber end face of the light transmission system may be hexagonal in order to make the luminance distribution of the secondary light source uniform.

  The present invention is not limited to the one described in the above embodiment, and various modifications can be made within the scope of the present invention.

1 is an overall configuration diagram showing an embodiment of an exposure apparatus equipped with a position measurement apparatus (FIA (Field Image Alignment) sensor of the present invention. FIG. It is a block diagram which shows detailed embodiment of the position measuring apparatus of FIG. (A) is explanatory drawing of (sigma) stop as an illumination aperture stop with which the position measuring apparatus shown in FIG. 2 was equipped. FIG. 6B is an explanatory diagram of an NA stop as the imaging light beam aperture stop. It is a block diagram which shows the light source of the illumination light for measurement with which the position measuring apparatus shown in FIG. 2 was equipped. It is explanatory drawing explaining the function of the parameter | index plate with which the position measuring apparatus shown in FIG. 2 was equipped. (A) is an enlarged view showing a σ stop arranged in an autofocus system equipped in the position measuring apparatus shown in FIG. 2. (B) is an enlarged view showing the aperture stop. C) is an enlarged view showing the multi-slit. It is a top view which shows an example of the alignment mark formed on the wafer as a to-be-exposed board | substrate. It is explanatory drawing of the various adjustments in the alignment autofocus system. (A) is explanatory drawing of a focus and a position adjustment method. (B) is explanatory drawing explaining the method of measuring the edge position and edge inclination of a signal. 3 is a configuration diagram of an optical path portion of a fine measurement system 28. FIG. It is explanatory drawing of the embodiment which forms the test patterns 125, such as a level | step difference pattern, in FM itself.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Exposure apparatus 15 XY stage 16 Z stage 20 FIA sensor (position measuring device)
21 CCD camera for search measurement (first light receiving element)
22 NA stop (first imaging beam aperture stop)
23 Search measurement system (first measurement system)
25, 26 Fine measurement CCD camera (second light receiving element)
27 NA stop (second imaging beam aperture stop)
28 Fine measurement system (second measurement system)
30 CCD camera for observation 31 Observation measurement system (third measurement system)
35 Alignment autofocus system 62 σ stop (illumination beam aperture stop)
69-71 First objective lens R Reticle W Wafer

Claims (5)

A position measurement device that measures the position of an object by irradiating measurement illumination light formed on the object with measurement illumination light and receiving and measuring reflected light reflected from the position measurement pattern. And
A first measurement system that receives reflected light reflected from the position measurement pattern by a first light receiving element via an objective optical system, and measures the position measurement pattern at a first measurement magnification;
The reflected light reflected from the position measurement pattern is received by the second light receiving element different from the first light receiving element through the objective optical system, and the position measurement pattern is higher than the first measurement magnification. A second measurement system for measuring at a second measurement magnification of the magnification,
The first measurement system includes a first imaging light beam aperture stop disposed on an optical path that guides light reflected from the position measurement pattern to the first light receiving element;
The second measurement system includes a second imaging light beam aperture stop disposed on an optical path that guides light reflected from the position measurement pattern to the second light receiving element,
A position measuring apparatus, wherein the first and second imaging light beam aperture stops have different numerical apertures. The position measuring device according to claim 1,
An illumination beam aperture stop that is disposed on an illumination optical path that guides the measurement illumination light to the position measurement pattern and includes a plurality of restricting portions for restricting the measurement illumination light to different numerical apertures or shapes. In addition,
When performing the measurement by the first measurement system, any one of the plurality of restricting portions is selectively arranged on the illumination optical path. In the position measuring device according to claim 1 or 2,
The reflected light reflected from the position measurement pattern is received by a third light receiving element independent of the first and second light receiving elements, and the position measurement pattern is lower in magnification than the first measurement magnification. A position measurement device further comprising a third measurement system for measuring at a third measurement magnification. An exposure apparatus that illuminates a mask pattern and transfers an image of the mask pattern onto an exposed substrate,
It has the position measuring device according to any one of claims 1 to 3,
An image of the mask pattern is transferred onto the exposure substrate positioned based on a result of measuring a position measurement pattern formed on the exposure substrate using the position measurement device. Exposure device. An exposure method for illuminating a mask pattern and transferring an image of the mask pattern onto an exposure substrate mounted on a stage,
The position measurement pattern formed on the substrate to be exposed is measured using the position measurement device according to any one of claims 1 to 3,
An exposure method, comprising: transferring an image of the mask pattern onto the substrate to be exposed positioned based on a result measured using the position measuring device.

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