JP2006135015A - Exposure device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve the problem that a base line fluctuates and overlay precision is deteriorated while a wafer one lot (about 25 sheets) is exposed, and that throughput is deteriorated when the base line is frequently measured for preventing deterioration of overlay precision. <P>SOLUTION: A mark arranged in an UL mirror cylinder is observed in a reticle microscope and an off-axis microscope. Relative dislocation of a meter system and a projection optical system is always measured and corrected. Thus, deterioration of overlay precision between base line measurement intervals is set to be a minimum. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to an exposure apparatus including an off-axis original plate and a substrate position measurement system. The present invention is particularly suitably applied to a scanning projection exposure apparatus that sequentially exposes a pattern on an original onto a photosensitive substrate by scanning the original and the photosensitive substrate in respective predetermined directions in synchronization. The

  Conventionally, in a manufacturing process of a semiconductor element formed from an extremely fine pattern such as LSI or VLSI, a reduced projection exposure in which a circuit pattern drawn on a mask is reduced and projected onto a substrate coated with a photosensitive agent. The device is in use. As the mounting density of semiconductor elements has increased, further refinement of the pattern line width has been demanded, and the resolution has been improved in response to the development of the resist process and the miniaturization of the exposure apparatus.

  As the degree of integration of these semiconductor elements is increased at the same time as the resolution is improved, the allowable range of the alignment state between the mask pattern and the photosensitive substrate pattern is becoming stricter year by year. Conventionally, the following three methods are used as the observation method of the alignment mark on the wafer surface for obtaining the position information of the photosensitive substrate, so-called wafer.

1. TTL method for measuring the position of the alignment mark on the wafer via the projection optical system. 2. An off-axis system that directly measures the position of an alignment mark on a wafer without using a projection optical system. There is a TTR system that simultaneously observes a wafer and a reticle via a projection optical system and detects the relative positional relationship between them.

  As an example of the above TTL method, there is a method of detecting alignment marks on a wafer using light having an alignment wavelength of non-exposure light via a projection optical system called TTL-AA (Through the Lens Auto Alignment). The following points are mentioned as the merits of this TTL-AA. Since the distance between the optical axis of the projection optical system and the optical axis of TTL-AA (so-called base line) can be arranged very short, the amount of wafer stage drive during alignment measurement and exposure is small. Therefore, a measurement error caused by a change in the distance between the optical axis of the projection optical system and the optical axis of TTL-AA due to an environmental change around the wafer stage can be suppressed. In other words, there is an advantage that the fluctuation of the baseline is small.

  However, when exposure light shifts to short wavelength light using an ArF laser or F2 laser as a light source, the glass material used is limited, so that it becomes difficult to correct chromatic aberration with respect to the alignment wavelength of the projection optical system. Therefore, an off-axis wafer observation microscope (hereinafter referred to as an off-axis microscope) that is not affected by the chromatic aberration of the projection optical system is effective.

  Further, in the case of an off-axis microscope, since there is no projection optical system, any wavelength can be used, and in addition, there is an advantage that a light source in a wide wavelength range can be used. As an advantage of using broadband wavelength light, it is possible to remove the influence of thin film interference on the photosensitive material (resist) coated on the wafer. Therefore, an off-axis microscope capable of correcting aberrations with respect to broadband wavelength light is an important alignment detection system.

  When aligning a reticle and wafer using an off-axis microscope that cannot directly measure the relationship between the observation position and the exposure position, the measurement center of the off-axis microscope and the projection image center of the pattern on the reticle (exposure center) are preliminarily measured. It is necessary to obtain a so-called baseline amount that is an interval between Then, the amount of deviation of the alignment mark in the shot on the wafer from the measurement center is detected by the off-axis microscope measurement, and the wafer is moved from the off-axis microscope observation position by a distance including the amount of deviation and the baseline amount. The center of the shot area is accurately aligned with the exposure center.

  However, in the process of using the exposure apparatus, the baseline amount may gradually vary due to changes over time. When such a baseline variation occurs, the alignment accuracy (superimposition accuracy) decreases because the shot center on the wafer cannot be sent to the center of the projection image of the pattern on the reticle. Therefore, it is necessary to periodically perform baseline measurement for accurately measuring the distance between the measurement center of the off-axis microscope and the projection image center of the pattern on the reticle.

  FIG. 1 is a diagram schematically showing the principle of baseline measurement of a projection exposure apparatus. The pseudo reticle R2 is provided with a mark M1 in the projection optical system exposure area. As shown in FIG. 1, the pseudo reticle R2 is held on the reticle drive stage 1, and the reticle drive stage 1 is moved so that the center of the pseudo reticle R2 is aligned with the optical axis AX of the projection optical system 2. On the wafer drive stage 3, a pseudo wafer W2 having a mark M2 equivalent to the alignment mark formed on the surface of the wafer W1 is provided at a position where it does not interfere with the wafer W1, and this mark M2 is the projection area of the projection optical system 2. When the wafer drive stage 3 is positioned by a laser interferometer (not shown) so as to be at a predetermined position, a TTR (Through the Reticle) type observation microscope 4 (hereinafter referred to as a TTR microscope) provided above the pseudo reticle R2. Thus, the mark M1 on the pseudo reticle R2 and the mark M2 on the pseudo wafer are simultaneously detected and the relative position is measured.

  An off-axis microscope 5 is disposed outside the projection optical system 2 (outside the exposure area). The optical axis of the off-axis microscope 5 is parallel to the optical axis AX of the projection optical system 2 on the side of the projection image. Inside the off-axis microscope 5, an index mark M3 serving as a reference for measuring the position of the mark on the wafer W1 or the pseudo-on-wafer mark M2 is provided on the glass plate, and a projection image plane (the surface of the wafer W1 or It is arranged almost conjugate with the surface of the pseudo wafer W2.

  As shown in FIG. 1, the position of the wafer drive stage 3 when the mark M1 on the pseudo reticle R2 and the mark M2 on the pseudo wafer W2 are aligned using a TTR microscope 4 is measured by a laser interferometer (not shown). To do. This value is X1. The position of the wafer stage 3 when the index mark M3 and the mark M2 of the off-axis microscope 5 are aligned is measured with a laser interferometer. If the value at this time is X2, the baseline amount BL can be obtained by calculating the difference (X1−X2). This baseline amount BL becomes a reference amount when the alignment mark on the wafer W1 is later measured by the off-axis microscope 5 and sent directly under the projection optical system 2.

  That is, the distance between the center of one shot (exposed area) on the wafer W1 and the alignment mark is XP, and the position of the wafer drive stage 3 when the alignment mark on the wafer W1 matches the index mark M3 of the off-axis microscope. Assuming X3, in order to match the shot center and the reticle center C, the wafer drive stage 3 may be moved to the position of the following equation (X3-BL-XP).

  As described above, after the alignment mark position on the wafer W1 is measured using the off-axis microscope, the wafer drive stage 3 is fed by a fixed amount related to the baseline amount BL, and the pattern of the reticle R1 is immediately transferred onto the wafer W1. Thus, exposure can be performed with accurate overlay on the shot area. However, it is necessary to measure the dimension between the reticle set mark M4 and the mark M1 on the pseudo reticle R2 by another means, and align the reticle R1 with the reticle set mark M4. Although only one-dimensional direction is considered here, it is actually necessary to consider it in two dimensions. Further, for simplicity, the baseline measurement is performed with one mark, but actually, the measurement is performed at a plurality of points in the exposure area and the angular deviation between the reticle and the wafer is corrected.

As described above, when the off-axis microscope is used, the reticle and wafer can be accurately aligned by always accurately measuring the baseline amount and reflecting the value (see, for example, Patent Document 1). ).
JP 2002-170754 A

  The base line varies depending on the position of the entire mark position measuring device with respect to the center of the projected image or the driving accuracy of the wafer stage. Assuming that the distance BL from the center of the projected image to the measurement center of the mark position measuring device is a temperature change, only (thermal expansion coefficient) × BL of the structure supporting the projection optical system and the mark position measuring device. Thermal deformation occurs. Further, when the driving accuracy of the wafer stage, for example, a yawing component is generated by θ, a measurement error is generated by θ × BL. These are alignment errors between the reticle and the wafer.

  In order to detect and correct these deviations, it is necessary to perform the baseline measurement described above. However, in order to perform baseline measurement, measurement using a TTR microscope that simultaneously observes a pseudo reticle and a mark on the pseudo wafer is included. In order to prevent the objective lens from blocking the exposure light, the TTR microscope is usually measured by moving to the exposure light passing region only at the time of measurement while escaping to the retracted position.

  Therefore, it takes time to drive the objective lens in order to perform measurement with the TTR microscope. In addition, a stage drive time for moving the pseudo-reticle and the mark on the pseudo-wafer to the measurement point and the time for measurement itself are required. These baseline measurement times degrade productivity. Since the exposure apparatus is required to be highly accurate and highly productive, it is not permitted to frequently perform the above-described baseline measurement using a TTR measuring instrument that deteriorates productivity. For this reason, the current exposure apparatus has a problem of how to correct the baseline deviation amount without reducing the throughput once the above-described baseline measurement is performed.

  In view of such points, the present invention provides an exposure apparatus that can reduce the influence of alignment errors caused by baseline fluctuations between baseline measurements and perform high-precision alignment of reticles and wafers without degrading throughput. The purpose is to provide.

  In order to achieve the above object, in the present invention, a mark is placed on the projection optical system barrel or optical component, the mark is observed with an off-axis microscope, and an index mark serving as a measurement standard possessed by the off-axis microscope itself, Compare. The relative positional fluctuation amount of both is recognized and corrected as a positional shift between the measurement center of the off-axis microscope and the projection optical system. This makes it possible to correct a relative positional shift caused by thermal deformation of the projection optical system and the off-axis microscope, which is an element of baseline fluctuation. Thereby, the wafer can always be sent to the correct position under the projection optical system.

  Similarly, on the reticle side, a mark is placed on the projection optical system barrel or optical component, and the mark is observed with an off-axis reticle observation microscope (hereinafter referred to as a reticle microscope), which becomes a measurement standard possessed by the reticle microscope itself. Compared with the index mark, the relative positional fluctuation amount of both is recognized and corrected as a relative positional deviation between the reticle microscope and the projection optical system. As a result, as in the wafer side, it is possible to correct a shift in the positional relationship between the measuring instrument system and the projection optical system, which is a factor of fluctuation. The above-mentioned baseline measurement is performed with a reticle and wafer exposure light TTR microscope that allows simultaneous observation of wafers for every fixed number of wafers processed, and the misalignment between the measurement system and the projection optical system is corrected between the measurements. By doing so, the positional deviation of the reticle and wafer can be minimized, and the alignment can be performed with high accuracy.

  That is, the technical contents of the present invention can solve the above-described problems by including the following configuration.

  (1) From an illumination optical system for irradiating an original with illumination light from an exposure light source, a projection optical system for projecting a pattern formed on the original onto a photosensitive substrate, and an optical axis of the projection optical system In an exposure apparatus having a detection area at a distant position and having an on-substrate mark position measuring device for measuring the position of an alignment mark on the photosensitive substrate, the mark provided on the projection optical system is the mark on the substrate. An exposure apparatus characterized by observing with a position measuring apparatus.

  According to the present invention, it is possible to detect and correct the amount of deviation of the original plate and the substrate position measurement system relative to the projection optical system among the baseline fluctuation factors between the baseline measurement and the next baseline measurement. This can reduce the deviation between the baseline measurement and the next baseline measurement. Therefore, it is possible to maintain highly accurate alignment performance without reducing the throughput, and a fine circuit pattern can be exposed efficiently and stably.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings.

  Embodiments of the present invention will be described with reference to the drawings. FIG. 2 is a schematic view of an exposure apparatus for carrying out the present invention. Of the names and functions of the respective parts, the same parts as those in FIG.

  The exposure apparatus of the present embodiment generally includes a light source 6 made of an excimer laser, a light source lens system 7 that is an optical system for shaping laser light L1 that is illumination light emitted from the light source 6 into a light beam having a predetermined shape, It comprises a projection optical system 2 that forms an image of a laser beam L1 formed in a predetermined shape by a light source lens system 7 on a wafer W1, which is a substrate, through a reticle R1.

  Reticle R1 and wafer W1 are mounted on reticle drive stage 1 and wafer drive stage 3, respectively, and scanning exposure is possible by driving the two stages in synchronization by changing the drive amount ratio corresponding to the magnification of projection optical system 2. It is said. The positions of the two stages can be measured by a laser interferometer (not shown). On each of the two stages, a mark M1 is provided on the pseudo reticle R2 and a mark M2 is provided on the pseudo wafer W2 for use in baseline measurement.

  Further, a TTR microscope 4 using exposure light is provided as a function of observing the marks M1 and M2 simultaneously and measuring the positional relationship. The light source of the TTR microscope 4 is provided with an optical path switching mirror mechanism 8 in the light source lens system 7. When the TTR microscope 4 is used, the mirror is placed in the optical path of the laser light L1 and the laser light L2 for the TTR microscope 4 light source is taken out. The laser beam L2 is incident on the TTR microscope 4 through the laser introducing optical system 9. The TTR microscope 4 is provided with a movable objective lens 10 so as not to block exposure light during exposure.

  A reticle microscope 11 for measuring the reticle mark position is installed on the reticle side. An index mark M5 serving as a measurement reference is built in the reticle microscope 11, the mark position on the reticle is measured based on this mark, and the amount of deviation is driven by the reticle alignment mechanism 12, whereby the reticle drive stage 1 is moved. It has a function of aligning the reticle R1 to a desired position. An off-axis microscope 13 for measuring the mark position on the wafer is provided on the wafer side. The off-axis microscope 13 has a built-in index mark M3 as a measurement reference, and the mark position on the wafer can be measured based on this mark. Projection optical system reference marks M6 and M7 are provided above and below the projection optical system 2, respectively, so that these marks can be observed with the reticle microscope 11 and the off-axis microscope 13. The function will be described below based on the schematic configuration diagram described above.

  When scanning exposure is performed with the reticle R1 pattern held on the reticle drive stage 1 superimposed on the wafer, both stages need to be driven in precise synchronization, and the absolute position of the reticle R1 and the wafer W1. Need to match. Therefore, baseline measurement is performed using the TTR microscope 4 as described in the prior art. The pseudo reticle R2 is sent into the projection optical system 2 exposure range by the reticle driving stage 1. In the pseudo reticle R2, the baseline measurement mark M1 is disposed within the exposure range of the projection optical system, and the alignment mark is disposed outside the exposure range as in the reticle R1.

  Next, the wafer drive stage 3 is moved so that the pseudo wafer W2 comes under the projection optical system 2. Similarly to the pseudo reticle R2, a baseline measurement mark M2 is also arranged on the pseudo wafer W2. The reticle drive stage 1 and wafer drive stage 3 are driven while measuring the position with an interferometer (not shown) so that the reticle and wafer baseline measurement marks are arranged at the center of the projection optical system. After driving, the marks M1 and M2 are overlapped and observed with the TTR microscope 4. The TTR microscope 4 introduces laser light L2 as illumination light, captures the mark on the wafer and the reticle as an image with a CCD camera, and the positional relationship between the two marks. Has a function to measure. During normal exposure, the objective lens 10 in the TTR microscope 4 is retracted from the exposure light passage area so as not to block the exposure light. At the time of TTR microscope measurement, the objective lens 10 is driven to the measurement image height. The TTR microscope 4 drives the wafer drive stage 3 and measures the alignment residual amount so that the deviation amount between both the reticle and the wafer mark is minimized. The positions of the reticle driving stage 1 and the wafer driving stage 3 at this time are measured with a laser interferometer, respectively.

  Next, the mark M1 on the pseudo reticle R2 and the mark M2 on the pseudo wafer W2 are moved to the measurement center of the reticle microscope 11 and the off-axis microscope 13. The position of the mark M1 on the pseudo reticle R2 is measured by the reticle microscope 11 with reference to the index mark M5, and the position of the reticle driving stage 1 at this time is measured by a laser interferometer.

  The positional relationship between the center of the projection optical system 2 and the center of measurement of the reticle microscope 11 based on the measured values of the TTR microscope 4, the reticle microscope 11, and the laser interferometer based on the same principle as described above for the wafer side in the conventional example. That is, the reticle side base line RBL can be measured. Similarly, on the wafer side, the position of the mark M2 on the pseudo wafer W2 is measured by the off-axis microscope 13 with reference to the built-in index mark M3. Based on the measured values of the wafer stage interferometer, the measurement center of the projection optical system 2 and the off-axis microscope 13, that is, the wafer-side baseline WBL can be measured. Since both the reticle and wafer side baselines are obtained, the reticle R1 and the off-axis microscope 13 are aligned at the measurement center of the reticle R1 and the mark on the wafer W1, and the reticle R1 and wafer are driven by driving both stages for the baseline. The relative position of W1 can be adjusted.

  During exposure operation after measuring the baselines on both the reticle side and the wafer side, the position of the mark on the reticle R1 and the mark on the wafer W1 are measured by the reticle microscope 11 and the off-axis microscope 13, and the stage is moved by the baseline to scan exposure. However, the baseline changes when the positional relationship between the projection optical system 2, the reticle microscope 11, and the off-axis microscope 13 changes due to thermal deformation or the like. Although the baseline measurement using the TTR microscope 4 described above is frequently performed, the baseline fluctuation due to various factors can be canceled. However, since the objective lens 10 driving and the measurement time of the TTR microscope 4 are extra, throughput is required. Will worsen. Therefore, in this embodiment, the reference marks M6 and M7 provided on the projection optical system 2 are observed with the reticle microscope 11 and the off-axis microscope 13 in order to reduce the alignment error after the baseline measurement, and the relative positions with respect to the index marks M5 and M3. The relative positional deviation between the projection optical system 2 and the measurement systems 11 and 13 is measured by measuring the change amount.

  FIG. 3A is an enlarged view of the lower part of the off-axis microscope 13 and the projection optical system 2. The off-axis microscope 13 measures the mark position on the wafer with reference to the index mark M3 as its reference, and moves the wafer drive stage 3 by taking the measured value and the previously measured baseline into consideration, thereby projecting. The shot center of the wafer can be aligned with the reticle image center of the optical system 2.

  Here, the projection optical system 2 is provided with a projection optical system reference mark M7 on a surface conjugate with the wafer as viewed from the off-axis microscope 13 and can be observed by the off-axis microscope 13. As described above, the projection optical system reference mark observation optical system 14 such as a half mirror is disposed in the off-axis microscope 13.

  As long as the projection optical system reference mark M7 is a component constituting the projection optical system 2, it may be installed in either a structure or an optical component. Further, if it is in the vicinity of the projection optical system, it may be attached to a component other than the components constituting the projection optical system. Since the off-axis microscope 13 can measure the position of the projection optical system reference mark M7 based on its own index mark M3, the distance between the off-axis microscope 13 and the projection optical system 2 changes due to thermal deformation or the like, and the baseline fluctuates by ΔWBL. In this case, the off-axis microscope can measure it as the projection optical system reference mark deviation ΔWBL. The distance between the off-axis microscope 13 and the projection optical system 2 is measured by measuring the wafer mark with the off-axis microscope on the basis of the index mark M3 and then moving the wafer on the basis of the interferometer with the measured value and the baseline WBL and ΔWBL. Regardless of the fluctuation, it is possible to send the shot center on the wafer to a fixed position of the projection optical system 2.

  In FIG. 3 (a), the projection optical system reference mark M7 is optically observed at all times. However, if necessary for the arrangement of the mark, a movable mechanism is provided in the middle of the projection optical system reference mark observation optical system 14. It is also possible to provide a light-shielding plate or absorption plate with which the projection optical system reference mark M7 can be observed only when necessary. By doing so, the projection optical system reference mark M7 can be made the same as the on-wafer mark, and the image processing function can be shared. Similar to the wafer side, the reticle side also corrects the relative displacement between the reticle microscope and the projection optical system.

  FIG. 3B shows an enlarged view of the upper part of the reticle microscope and the projection optical system. The reticle microscope 11 measures the relative position of the mark on the reticle R1 with respect to the index mark M5 serving as its reference, and drives the reticle alignment mechanism 12 so that the positions of the marks match each other. The alignment error is measured with a reticle microscope, and the reticle R1 is fed onto the projection optical system 2 by the reticle stage by an amount that takes into account this measured value and the baseline RBL previously measured, thereby allowing the reticle image through the projection optical system to pass through. The relative position between the center and the shot center on the wafer can be matched.

  Here, a projection optical system reference mark M6 is provided above the projection optical system. This mark may be attached to any component as long as it is a component constituting the projection optical system 2 as in the wafer side.

  Further, as long as it is in the vicinity of the projection optical system 2, it may be attached to a component other than the components constituting the projection optical system 2. The projection optical system reference mark observation optical system 15 is arranged so that the projection optical system reference mark M6 is conjugated with the on-reticle mark surface when viewed from the reticle microscope 11. The reticle microscope 11 measures the position of the projection optical system reference mark M6 with reference to its own index mark M5 in the same way as the mark on the reticle R1.

  When the distance between the reticle microscope 11 and the projection optical system 2 changes due to thermal deformation and the baseline changes by ΔRBL, the reticle microscope 11 can measure it as a deviation ΔRBL of the projection optical system reference mark M6.

  After measuring the mark on the reticle R1 with the reticle microscope 11 on the basis of the index mark M5, the reticle driving stage 1 is moved on the basis of the interferometer by an amount including the measured value, the baselines RBL and ΔRBL. 11. Projection optical system 2 Since reticle R1 can be sent to a fixed position of the projection optical system without being affected by relative position fluctuations, the shot center on the wafer can be aligned with the center of the projection optical system 2 reticle image. However, the cause of the baseline fluctuation may be other than the physical distance fluctuation between the measurement system and the projection optical system. For example, when the optical component inside the projection system is thermally deformed, only the optical axis may be changed with respect to the component outside the projection system.

  Baseline fluctuations due to such factors cannot be corrected by simply observing the projection optical system reference mark as in the present embodiment, so it is necessary to perform baseline measurement using the above-described TTR microscope every time a certain period of time elapses. is there.

  The present embodiment is effective as a function for minimizing the positional deviation from the execution of the baseline measurement to the execution of the next baseline measurement.

  FIG. 4 is a schematic view of the apparatus of the second embodiment. FIG. 4 shows another embodiment of the reticle / wafer measurement system having the same function in the same exposure apparatus as in FIG. 2 of the first embodiment. Of the names and functions of the respective parts, the same parts as those in FIG. In this embodiment, there is no reference mark inside the reticle microscope or off-axis microscope, and both the reticle microscope and off-axis microscope use the projection optical system reference mark installed in the projection optical system as a measurement standard. Different from 1.

  Details of the second embodiment will be described with reference to FIG. In the second embodiment, the baseline measurement is performed before the exposure operation as in the first embodiment. Since the description of the baseline measurement method is the same as that of the first embodiment, it is omitted. In the present embodiment, the projection microscope reference marks M6 and M7 are used as the measurement reference without the reference mark inside the reticle microscope 16 and the off-axis microscope 17 as a reference.

  FIG. 5A shows an enlarged view of the lower part of the off-axis microscope 17 and the projection optical system of the second embodiment. Of the names and functions of the respective parts, the same parts as those in FIG. The off-axis microscope measures the position of the mark on the wafer W1 by measuring the relative position with the projection optical system reference mark 7 serving as its own measurement reference, and takes into account the measured value and the baseline WBL previously measured. By moving the wafer, the shot center of the wafer can be adjusted to a fixed position of the projection optical system.

  When the distance between the off-axis microscope 17 and the projection optical system 2 fluctuates by ΔWBL due to thermal deformation, the projection optical system reference mark M7 as the measurement reference of the off-axis microscope 17 also fluctuates in the same manner. By measuring the mark on the wafer W1 with reference to M7 and moving the wafer drive stage 3 by the interferometer reference by an amount in which the base line WBL is added to the measured value, the off-axis microscope 17 and the projection optical system 2 regardless of relative position fluctuations. The shot center on the wafer W1 can be aligned with a certain position of the projection optical system 2. Similarly, the relative displacement between the reticle microscope and the projection optical system can be canceled on the reticle side.

  FIG. 5B shows an enlarged view of the upper part of the reticle microscope and the projection optical system. Of the names and functions of the respective parts, the same parts as those in FIG. The reticle microscope 16 measures the relative position of the mark on the reticle X with respect to the projection optical system reference mark M6 serving as its own measurement reference, and drives the reticle alignment mechanism 12 so that the positions of the marks match. By measuring the alignment error and moving the reticle driving stage 1 on the basis of the interferometer by an amount that includes the measured value and the baseline RBL previously measured, the reticle can be sent to a fixed position on the projection optical system. it can.

  When the distance between the reticle microscope 16 and the projection optical system 2 changes by ΔRBL due to thermal deformation, the position of the projection optical system reference mark M6 that becomes the measurement reference of the reticle microscope 16 also changes in the same manner. Therefore, the projection optical system reference mark M6 By measuring the mark on the reticle R1 using the reference and moving the reticle driving stage 1 based on the stage interferometer by an amount that includes the baseline RBL in the measurement value, the influence of the reticle microscope 16 and the projection optical system 2 relative position fluctuations is affected. Since the reticle R1 can always be sent to the same position with respect to the projection optical system without being received, exposure can be performed in a state where the reticle image center of the projection optical system 2 and the shot center on the wafer are aligned.

  However, as with the first embodiment, the baseline fluctuation may be caused by a physical distance between the measurement system and the projection optical system, as well as the physical distance. It is necessary to perform baseline measurement using the aforementioned TTR microscope every time. This embodiment is also effective as a means for minimizing the reticle and wafer alignment errors from the baseline measurement to the next baseline measurement, as in the first embodiment.

  In this embodiment, spectroscopic parts in which marks used as measurement standards are deleted from the reticle microscope and the off-axis microscope can be reduced. Therefore, the reticle and wafer are more advantageous than the first embodiment in terms of cost and size. Baseline fluctuations due to measurement system and projection system misalignment can be canceled only after measurement with an off-axis microscope, so it is not possible to cancel the deviation amount in real time for each shot while processing one wafer, for example. This is a disadvantage to Example 1.

  FIGS. 6A and 6B are enlarged views of the reticle microscope and off-axis microscope unit of the third embodiment. Since other configurations and functions are the same as those of the second embodiment, description thereof is omitted. In this embodiment, the projection optical system reference marks M6 and M7 are not directly attached to the parts constituting the projection optical system, but are attached to the projection optical system via the holding parts 18 and 19. Different from 2.

  Example 3 will be described with reference to the drawings. In the third embodiment, since the projection optical system reference mark is not directly attached to the components of the projection optical system, there is a degree of freedom in the arrangement of the mark positions. Therefore, as shown in FIGS. 6A and 6B, the projection optical system reference marks M6 and M7 can be attached in the same direction as the wafer W1 and the reticle R1 when viewed from the reticle microscope 16 and the off-axis microscope 17. In this case, in addition to the change in the relative distance between the projection optical system 2 and the measurement system, it is possible to cancel the variation in the measurement value that occurs when the vicinity of the objective lens of the measurement system is tilted.

  6A and 6B, when the mirrors of both the reticle microscope 16 and the off-axis microscope 17 are tilted by θ due to thermal deformation or the like, assuming that the span from the mirror to the measurement surface is L, the reticle R1 and the wafer The measurement values of the reticle microscope 16 and the off-axis microscope 17 change so that W1 approaches the projection optical system 2 by L × tan θ. If the base line RBL, the WBL reticle R1, and the wafer W1 are fed as they are, a feed shortage deviation occurs by L × tan θ.

  However, in this embodiment, the projection optical system reference marks M6 and M7, which are measurement references, are also measured with a deviation of L × tan θ. Since the deviation direction is the same as that of the wafer and the reticle, the deviation of L × tan θ is canceled with reference to the projection optical system marks M6 and M7.

  As described above, the third embodiment is superior to the first and second embodiments in that it can cancel the alignment variation due to the inclination in the vicinity of the measurement system objective lens. On the other hand, it can be said that it is a disadvantage that the thermal deformation of the parts 18 and 19 holding the projection optical system reference mark increases as a variable factor compared to the first and second embodiments. Further, as a mark arrangement, an arrangement as shown in FIG. 7 can be performed.

  FIG. 7 is a partially enlarged view of the off-axis microscope. Of the names and functions of the respective parts, the same parts as those in FIG. 6A differs from FIG. 6A in that the support component 20 is attached to the projection optical system 2 and the projection optical system reference mark M7 is arranged on the lower surface of the glass part 21 on the wafer mark. This mark arrangement reduces the number of optical components for measuring the projection optical system reference mark in the off-axis microscope, and the optical path is separated because the mark on the wafer and the reference mark are imaged on the CCD through the same optical system. Compared to the case of the measurement, it is possible to eliminate the measurement error factor due to the difference in the optical system. Such an arrangement is also possible on the reticle side. Similar to the wafer side, the same effect as that on the wafer side can be obtained by arranging a glass component supported by the projection optical system under the reticle mark and providing a projection optical system reference mark on the upper surface thereof.

It is the schematic which shows the baseline measuring method of a prior art. It is the schematic showing the 1st Example of this invention. (A) is a schematic diagram of the off-axis microscope part of the first embodiment of the present invention. (B) is a schematic diagram of a reticle microscope section of the first embodiment of the present invention. It is the schematic showing the 2nd Example of this invention. (A) is a schematic diagram of the off-axis microscope section of the second embodiment of the present invention. (B) is a schematic diagram of the reticle microscope section of the second embodiment of the present invention. (A) is a schematic diagram of the off-axis microscope section of the third embodiment of the present invention. (B) is a schematic diagram of a reticle microscope section of a third embodiment of the present invention. It is a schematic diagram of a projection optical system reference mark position change type off-axis microscope unit of the third embodiment of the present invention.

Explanation of symbols

AX Projection optical system optical axis BL Base line L1 Exposure light source laser light L2 Measurement light source laser light R1 Reticle R2 Pseudo reticle W1 Wafer W2 Pseudo wafer M1 Pseudo reticle alignment mark M2 Pseudo wafer alignment mark M3 Off-axis microscope index mark M4 reticle set mark M5 reticle microscope index mark M6 projection optical system reference mark M7 projection optical system reference mark RBL reticle side base line WBL wafer side base line 1 reticle driving stage 2 projection optical system 3 wafer driving stage 4 TTR microscope 5 off-axis microscope 6 Light source laser 7 Light source lens system 8 Optical path switching mirror mechanism 9 TTR microscope laser introduction optical system 10 Movable objective lens 11 Reticle microscope 12 Reticle alignment mechanism 13 Off-axis microscope 14 Projection optics System reference mark observation optical system 15 Projection optical system reference mark observation optical system 16 Reticle microscope 17 Off-axis microscope 18 Reticle side projection optical system reference mark holding part 19 Wafer side projection optical system reference mark holding part 20 Wafer side projection optical system Reference mark holding component 21 Wafer side projection optical system reference mark holding glass component

Claims (6)

  An illumination optical system for irradiating an original with illumination light from an exposure light source, a projection optical system for projecting a pattern formed on the original onto a photosensitive substrate, and a position away from the optical axis of the projection optical system An exposure apparatus having an on-substrate mark position measuring device for measuring a position of an alignment mark on the photosensitive substrate, wherein a mark provided in a projection optical system is used as the on-substrate mark position measuring device. An exposure apparatus characterized by observing with.   An illumination optical system for irradiating an original with illumination light from an exposure light source, a projection optical system for projecting a pattern formed on the original onto a photosensitive substrate, and a position away from the optical axis of the projection optical system In the exposure apparatus having an original position measuring device for measuring the position of the positioning mark on the original plate, the mark provided on the projection optical system is observed by the original mark position measuring device. An exposure apparatus.   An illumination optical system for irradiating an original with illumination light from an exposure light source, a projection optical system for projecting a pattern formed on the original onto a photosensitive substrate, and a position away from the optical axis of the projection optical system An exposure apparatus having an on-substrate mark position measuring device for measuring a position of an alignment mark on the photosensitive substrate, wherein a mark provided in a projection optical system is used as the on-substrate mark position measuring device. By monitoring the amount of relative position deviation from the index mark provided inside the on-board mark position measurement device, the substrate side baseline fluctuation due to the relative displacement between the projection optical system and the on-board mark position measurement device is recognized. An exposure apparatus characterized in that correction is performed.   An illumination optical system for irradiating an original with illumination light from an exposure light source, a projection optical system for projecting a pattern formed on the original onto a photosensitive substrate, and a position away from the optical axis of the projection optical system In the exposure apparatus having the original position measuring device for measuring the position of the positioning mark on the original plate, the mark provided on the projection optical system is observed with the on-original mark position measuring device, By monitoring the amount of relative positional deviation from the index mark provided inside the mark position measuring device, it is possible to recognize and correct variations in the original side baseline due to relative positional deviation between the projection optical system and the original mark position measuring device. A featured exposure apparatus.   2. The exposure apparatus according to claim 1, wherein the substrate position measuring apparatus uses a mark itself provided on the projection optical system as an index mark when measuring the substrate position.   3. The exposure apparatus according to claim 2, wherein the original position measuring device uses a mark itself provided in the projection optical system as an index mark when measuring the original position.

Images