JP2010283305A - Exposure apparatus and method of manufacturing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exposure apparatus that exchanges multiple original plates to expose the patterns of the original plates on a substrate, improves the accuracy of alignment between the original plates and the substrate, and improves a throughput. <P>SOLUTION: The exposure apparatus for exposing the patterns of the original plates on the substrate by double patterning includes a stage that moves with the original plate placed thereon, a holding means for holding the original plate to be exposed following the original plate placed on the stage, a heating means for heating the original plate held by the holding means, and a control means for controlling the heating means. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an exposure apparatus that exposes a pattern of an original on a substrate.

Recently, the progress of semiconductor device manufacturing technology has been remarkable, and the progress of microfabrication technology has been remarkable. In particular, optical processing technology is mainly reduced projection exposure equipment with submicron resolution, commonly known as steppers, and it is necessary to increase the numerical aperture (NA) of the optical system and shorten the exposure wavelength to further improve the resolution. It is illustrated. As the exposure wavelength is shortened, the exposure light source is also changing from a g-line or i-line high-pressure mercury lamp to an KrF or ArF excimer laser.
Furthermore, in order to improve the resolution and secure the depth of focus during exposure, a projection exposure apparatus having a projection optical system that can expose the space between the wafer and the projection optical system in an immersion state has appeared.

  In addition, since there is a limit to shortening the wavelength and increasing the NA in the past, in one process of various processes for forming a semiconductor element, a plurality of masks (reticles) are exchanged and a mask pattern is formed on the wafer. A method has been proposed in which exposure is performed and miniaturization is performed by overlapping a plurality of exposures. These are referred to as a double exposure method (“Double Exposure method”) or a double patterning method.

  Further, as the resolution of the projection pattern is improved, higher accuracy is also required for the alignment for relatively aligning the wafer (substrate) and the mask (original plate) in the projection exposure apparatus. A projection exposure apparatus is not only a high-resolution exposure apparatus but also a function as a highly accurate position detection apparatus. As the miniaturization progresses, it is necessary to improve the alignment accuracy between the wafer and the mask.

  In particular, the above-described double exposure method proposed as a semiconductor miniaturization method is to apply a plurality of masks to a resist that has been applied once, to expose a mask pattern onto a wafer, and to overlap a plurality of exposures. In this method, a plurality of mask patterns are sequentially overlapped and exposed. This double exposure method does not include a conventional development process between exposures of a plurality of masks, and a plurality of masks are stored in advance in an exposure apparatus to develop a single wafer. The exposure is performed sequentially.

  On the other hand, the exposure apparatus is also required to improve throughput, which is the capability of wafer exposure processing. Recently, an exposure apparatus (hereinafter referred to as a “two-stage exposure apparatus”) having two wafer stages has been proposed in order to improve this throughput and to improve alignment and focus accuracy. This two-stage exposure apparatus has a measurement region (measurement stage) for measuring alignment, focus, and the like, and an exposure region (exposure stage) for performing exposure. In addition, there are a plurality of wafer stages that move back and forth between these two areas, and the wafer stage is alternately switched between the measurement area and the exposure area, and the wafer is exposed. For this reason, in the conventional example in which the measurement area and the exposure area are one area, the alignment and exposure are performed continuously. However, in the two-stage exposure apparatus, the alignment can be performed in parallel and the throughput is improved and the alignment is performed. Highly accurate measurement is performed by extending the measurement time.

  The reticle usually has a structure in which a pattern is formed of Cr on quartz, and the temperature rises due to the absorption of exposure light in the exposure operation, and expands. Since the reticle expands in this way, the pattern itself formed on the reticle also expands, causing an alignment error between the reticle and the wafer. Therefore, in Patent Document 1, in an exposure apparatus that exposes a plurality of wafers with a single reticle, exposure of the reticle is measured by measuring the expansion of the reticle during exposure and correcting the image formation state based on the measurement result. A device has been proposed.

Japanese Patent Laid-Open No. 4-192317

  In the exposure apparatus of the double exposure method, a plurality of reticles are alternately exposed on a single wafer. For example, when double exposure is performed using two reticles A and B, exposure is performed in the steps of alignment measurement, focus measurement, reticle A exposure, reticle replacement, reticle B exposure, and wafer recovery. On the other hand, the reticle usually has a structure in which a pattern is formed of Cr on quartz, and the temperature rises due to absorption of exposure light in the exposure operation, and expands. When the reticle expands, the pattern itself formed on the reticle also expands, which causes an alignment error between the reticle and the wafer.

  In the conventional exposure apparatus disclosed in Patent Document 1, in order to expose a plurality of wafers with a single reticle, the reticle expansion is measured, and exposure is performed with correction based on the measurement result of the reticle expansion. It was only. That is, it is sufficient to capture the expansion component during exposure. However, in the exposure apparatus of the double exposure method, since the reticle A is exchanged with another reticle B after the exposure operation and exposed, the reticle A is not exposed. In a state where no exposure is performed, the reticle A contracts because it is cooled. Therefore, when the reticle A is exposed again to another wafer next time, the reticle and wafer cannot be aligned with high accuracy unless the deformation component is managed. Similarly, since the reticle B is repeatedly heated by exposure and cooled by standby, exposure by high-precision alignment cannot be performed.

Although it is possible to measure the deformation component of the reticle every time the reticle is exchanged, the measurement time is required, so that the throughput is lowered. In the exposure apparatus of the double exposure method, since the time for exchanging the reticle occurs, the throughput further decreases.
SUMMARY OF THE INVENTION An object of the present invention is to provide an exposure apparatus that replaces a plurality of original plates and exposes a pattern of the original plate onto a substrate, improves alignment accuracy between the original plate and the substrate, and improves throughput.

An exposure apparatus of the present invention for solving the above-mentioned problems is an exposure apparatus that exposes a plurality of original plate patterns on a substrate by double patterning.
Holding means for holding an original to be exposed next to the original mounted on the stage, temperature adjusting means for adjusting the temperature of the original held by the holding means, and control means for controlling the temperature adjusting means; It is characterized by providing.

  According to the present invention, a plurality of original plates are exchanged to expose a pattern of the original plate on the substrate, the alignment accuracy between the original plate and the substrate is improved, and the throughput is improved.

It is a schematic block diagram of the exposure apparatus of Embodiment 1 of this invention. It is explanatory drawing of the baseline measurement in Embodiment 1 of this invention. It is a graph which shows the concept of the relationship between the expansion-contraction state of a reticle in 1st Embodiment of this invention, an exposure state, and a standby state. It is a schematic block diagram of the two-stage type exposure apparatus of the modification of Embodiment 1 of this invention. It is explanatory drawing of the sequence of the double exposure method in the two-stage type exposure apparatus of the modification of Embodiment 1 of this invention. It is explanatory drawing of the measurement result of the expansion-contraction state of the reticle at the time of standby in Embodiment 1 of this invention. It is explanatory drawing of the measurement result of the expansion-contraction state of the reticle at the time of another waiting in Embodiment 1 of this invention. It is explanatory drawing of the cooling means in Embodiment 1 of this invention. It is explanatory drawing of the measurement result of the calibration light quantity in Embodiment 1 of this invention. It is explanatory drawing of the cooling means in Embodiment 1 of this invention. It is explanatory drawing of the cooling means in Embodiment 2 of this invention. It is explanatory drawing of the cooling means in Embodiment 2 of this invention.

Embodiments of the present invention will be described below with reference to the accompanying drawings.
With reference to FIG. 1, the exposure apparatus of Embodiment 1 of this invention is demonstrated. The exposure apparatus according to the first embodiment of the present invention is an exposure apparatus of a double exposure method in which a plurality of reticles 2 and 2 ′ (original) are exchanged to expose a pattern of reticles 2 and 2 ′ onto a wafer 6 (substrate). In other words, the exposure apparatus exposes the wafer 6 with a pattern of a plurality of reticles 2, 2 ′ by double patterning.
In the exposure apparatus of the double exposure method, the first reticle 2 constituting the first pattern is exposed to one wafer 6. After that, the reticle is exchanged for the second reticle 2 ′ by the reticle transport system 21 shown in FIG. 4, and this single wafer 6 is exposed.
When there are three or more reticles 2, 2 ',..., This repeated exposure is performed. In other words, a plurality of reticles 2, 2 ′, etc. are sequentially exchanged for one wafer 6, exposure is performed, and when there are a plurality of wafers 6. On the other hand, the same operation is repeated.

In the exposure apparatus of the double exposure method of the first embodiment, the reason for performing the exposure in the above procedure is as follows. For example, when there are a plurality of wafers 6..., All the wafers 6... Are exposed using the first reticle 2, and after completion, all the wafers 6 are used using the second reticle 2 ′. A method of exposing... Is also conceivable.
In this method, since the number of times of exchanging the reticles 2 and 2 ′ is reduced, the time required for exchanging the reticles 2 and 2 ′ can be reduced, thereby improving the throughput. However, this method requires alignment measurement of the wafer 6... Every time for the second reticle 2 ′, so that the alignment accuracy deteriorates. For this reason, when the alignment measurement of one wafer 6 is completed, the plurality of reticles 2 and 2 ′ are exposed, and then the operation of shifting to the next wafer exposure operation does not cause a decrease in alignment accuracy.

The reticle stage 20 (stage) is means for mounting and moving the reticles 2 and 2 ′. The reticle transport system 21 (holding means) is means for holding a reticle 2 ′ to be exposed next to the reticle 2 mounted on the reticle stage 20.
The light IL having the optical axis AX emitted from the illumination optical system 1 that illuminates the exposure light illuminates the reticle 2 arranged on the basis of the reticle set marks 12 and 12 ′ formed on the reticle stage 20. The reticles 2 and 2 'are positioned by a reticle alignment scope 11 that can simultaneously observe the reticle set marks 12 and 12' and the reticle set marks 13 and 13 'formed on the reticles 2 and 2'.

  The reticle alignment scope 11 is configured to be movable above the reticle 2 using exposure light as a light source, and passes both the reticle 2 and the wafer 6 at a plurality of image heights of the projection optical system 3 through the reticle 2 and the projection optical system 3. Observable. That is, the positions of the reticle 2 and the wafer 6 can also be detected. Note that a scope that can be observed through the projection optical system 3 and a scope that can measure the reticle set alignment marks 12 and 12 ′ may be configured separately.

  The light IL transmitted through the pattern on the reticle 2 forms an image of the pattern on the reticle 2 on the wafer 6 via the projection optical system 3, and forms an exposure pattern on the wafer 6. At this time, an area where one exposure is performed is called a shot. The wafer 6 is controlled by a stage control system 10 and is held on a wafer stage 8 (substrate stage) that can be driven in XYZ and rotational directions. A reference mark 15 for baseline measurement, which will be described later, is formed on the wafer stage 8.

  On the other hand, an alignment mark (not shown) is formed on the wafer 6, and the position of the alignment mark is measured by the dedicated position detection device 4. The position of the wafer stage 8 is always measured by an interferometer 9 referring to the mirror 7 of the interferometer, and is formed on the wafer 6 from the measurement result of the interferometer 9 and the measurement result of the alignment mark by the position detection device 4. The arrangement information of the shots that have been taken is calculated.

  Further, when the wafer 6 is exposed, it is necessary to perform alignment with respect to the focus position of the image formed by the projection optical system 3, and the focus detection device 5 that detects the position of the wafer 6 in the focus direction is provided. . The focus detection device 5 includes a light source 501, an illumination lens 502, a slit pattern 503, an illumination lens 504, a mirror 505, a mirror 506, a detection lens 507, and a photoelectric conversion element 508. Light 501 a emitted from the light source 501 projects the slit pattern 503 from an oblique direction on the wafer 6 through the illumination lens 502, the slit pattern 503, the illumination lens 504, and the mirror 505. The slit pattern 503 projected on the wafer 6 is reflected by the surface of the wafer 6 and reaches the photoelectric conversion element 508 such as a CCD by the detection lens 507 configured on the opposite side via the mirror 506. The focus direction of the wafer 6 is measured from the position of the image of the slit pattern 503 obtained by the photoelectric conversion element 508.

As described above, the arrangement information of the shots formed on the wafer 6 is calculated from the measurement result of the alignment mark (not shown) on the wafer 6 by the position detection device 4. However, before calculating the shot arrangement information, it is necessary to obtain the baseline BL shown in FIG. 2 which is the relative positional relationship between the position detection device 4 and the reticle 2.
An outline of this baseline measurement method will be described with reference to FIG. The reticle 2 has a calibration mark 23 that is a position correction mark. When the calibration mark 23 is illuminated by the illumination optical system 1, the light IL that has passed through the transmission part of the calibration mark 23 is converted by the projection optical system 3 into an opening pattern image of the calibration mark 23 on the wafer 6 side. Form at the focus position.

  On the other hand, a reference mark 15 is formed on the wafer stage 8, and the reference mark 15 has a pattern having an opening having the same size as the projection image of the calibration mark 23 on the reticle 2. The light IL that has passed through the aperture pattern reaches a photoelectric conversion element (not shown) that is configured under the reference mark 15, and the intensity of the light IL that has passed through the aperture pattern is measured by the photoelectric conversion element (not shown). .

  Further, on the reference mark 15, a position measurement mark (not shown) that can be detected by the position detection device 4 is configured in addition to the opening pattern corresponding to the calibration mark 23 of the reticle 2. The position measurement mark (not shown) of the reference mark 15 is driven to the observation region of the position detection device 4 and detected by the position detection device 4 and the measurement result of the position of the wafer stage 8 by the interferometer 9 at that time. The position of the position measurement mark (not shown) of the reference mark 15 is obtained.

Next, with reference to FIG. 2, a method for obtaining the baseline BL, which is the relative position of the position detection device 4 with respect to the projection optical system 3, using the reference mark 15 will be described in more detail.
First, the calibration mark 23 formed on the reticle 2 is driven to a predetermined position through which the exposure light IL passes. The exposure light IL is illuminated by the illumination optical system 1 with respect to the calibration mark 23 driven to a predetermined position. The light IL that has passed through the transmission part of the calibration mark 23 is imaged as a pattern image of the calibration mark 23 at the imaging position on the wafer 6 by the projection optical system 3. The wafer stage 8 is driven to move the opening pattern on the reference mark 15 having the same shape to a position that matches the pattern image of the calibration mark 23. At this time, while the reference mark 15 is arranged on the image formation surface (predetermined focus surface) of the calibration mark 23, the photoelectric pattern under the reference mark 15 is driven while driving the opening pattern on the reference mark 15 in the X direction. An output value of a conversion element (not shown) is measured.

FIG. 9 shows a schematic graph when the position of the opening pattern on the reference mark 15 in the X direction and the output value of the photoelectric conversion element (not shown) under the reference mark 15 are plotted. In FIG. 9, the horizontal axis is the position of the opening pattern on the reference mark 15 in the X direction, and the vertical axis is the output value I of the photoelectric conversion element (not shown) below the reference mark 15. As shown in FIG. 9, when the relative position of the opening pattern on the calibration mark 23 and the reference mark 15 is changed, the output value also changes. Of the change curve 40, the light that has passed through the calibration mark 23 has the maximum intensity at the position (X0) where it coincides with the opening of the opening pattern on the reference mark 15. By obtaining the coincident position X0, the position of the image projected on the wafer 6 by the projection optical system 3 of the calibration mark 23 is obtained.
Note that the calibration mark 23 is configured at a plurality of locations on the reticle 2, and the position of the calibration mark 23 is measured by the reference mark 15, thereby measuring the shape (magnification, distortion state) of the reticle 2. It is also possible.

  The cooling fans 61 and 61 ′ (temperature adjusting means) shown in FIGS. 1 and 10 are means for adjusting the temperature of the reticle 2 ′ held by the reticle transport system 21 (holding means) and are in a standby state until exposure. Cool reticle 2 '. The upper surface of the reticle 2 ′ is sucked by the reticle transport system 21, and cooling fans 61 and 61 ′ are provided in the vicinity below the reticle 2 ′. Air or gas controlled to a predetermined temperature is blown from the cooling fans 61 and 61 '. The cooling fans 61 and 61 'are disposed only below, but the present invention is not limited to this, and the cooling fans 61 and 61' may be provided above the reticle 2 '.

  The cooling fans 61 and 61 'may be provided so as to be movable. That is, the exposure area to be exposed varies depending on the circumstances of the user, such as the specifications of the chip to be manufactured. Therefore, when the exposure area is different, the high temperature portion, which is the expansion portion of the reticle 2 ', is different, so that the cooling location is also changed, and cooling is performed locally and efficiently. The moving direction may be the in-plane direction of the reticle 2 'or a direction approaching the reticle. By cooling by the cooling fans 61 and 61 ′, the reticle 2 ′ in the standby state can be controlled to be in a predetermined expansion / contraction state that is a predetermined temperature state before the next exposure is started.

The control means 14 is a means for controlling the cooling fans 61 and 61 ′, and the cooling fans 61 and 61 ′ are cooled so that the temperature immediately before the exposure of the reticle 2 ′ in the standby state becomes a predetermined expansion / contraction state. Control.
The control unit 14 controls the cooling fans 61 and 61 ′ so as to predict and correct the expansion state of the reticle 2 ′ during exposure based on the predetermined expansion / contraction state.

The exposure apparatus of the first embodiment measures the expansion / contraction state of the reticle 2 ′ held by the reticle transport system 21 (holding means), and the position detection devices 32 and 32 ′ shown in FIG.
(Extension monitor) or an infrared scope 42 (extension monitor) shown in FIG.
The control unit 14 controls the cooling fans 61 and 61 ′ based on the measurement results of the position detection devices 32 and 32 ′ or the infrared scope 42. The position detection devices 32 and 32 ′ measure the position of the position detection mark formed on the reticle 2 ′. The infrared scope 42 is a thermography that measures the temperature of the reticle 2 ′.

  With reference to FIG. 6, a method for measuring the expansion / contraction state of reticle 2 'in the standby state will be described. FIG. 6A shows the exposure apparatus of Embodiment 1 from the side, and FIG. 6B is a plan view of FIG. 6A. Position detection devices 32 and 32 'for observing and measuring the alignment mark formed on the reticle 2' are configured at the standby position of the reticle 2 '. After the exposure of a certain reticle is completed, the expansion / contraction state of the reticle 2 'can be measured at the standby position. Alignment marks AM1, AM2, AM3, AM4 are formed on the lower surface of the reticle 2 '. A reference plate 31 serving as a reference is arranged in the vicinity of the Z direction. The reference plate 31 includes reference patterns FM1, FM2, FM3, FM4 for the alignment marks AM1, AM2, AM3, AM4 formed on the reticle 2 '.

  FIG. 6B shows the relationship between the reference patterns FM1, FM2, FM3, FM4 and the alignment marks AM1, AM2, AM3, AM4. The reference patterns FM1, FM2 are included in the alignment marks AM1, AM2, AM3, AM4. , FM3, FM4 are arranged. The position detection devices 32 and 32 'are configured at positions corresponding to the alignment marks AM1, AM2, AM3 and AM4, and the reference patterns FM1, FM2, FM3 and FM4. The position detection devices 32 and 32 'simultaneously observe the alignment marks AM1, AM2, AM3 and AM4 and the reference patterns FM1, FM2, FM3 and FM4. By detecting the positions of the alignment marks AM1, AM2, AM3, AM4 corresponding to the reference patterns FM1, FM2, FM3, FM4, the expansion / contraction state of the reticle 2 'is measured. In other words, by detecting the relative positions of the four alignment marks AM1, AM2, AM3, AM4 and the reference patterns FM1, FM2, FM3, FM4, it is possible to measure the expansion / contraction state of the reticle 2 ′ in the X and Y directions. It becomes. Here, the temperature of the reference plate 31 is controlled, and the reference plate 31 itself does not expand and contract. Or the temperature is measured and the expansion-contraction state is managed correctly.

  With reference to FIG. 7, another method for measuring the expansion / contraction state which is the temperature distribution of the reticle 2 'in the standby state will be described. In the first embodiment, an infrared scope 42 that measures the expansion / contraction state that is the temperature distribution of the reticle 2 ′ is configured. The infrared scope 42 is a thermography, which captures infrared rays generated from the entire surface of the reticle 2 'or a predetermined region, and measures the temperature distribution of the reticle 2' from the infrared rays. By controlling the temperature of the heat absorbing members 62a, 62b, 62c, and 62d in FIG. 11 based on the result of the infrared scope 42, the infrared scope 42 is always controlled to have a predetermined temperature and a predetermined temperature distribution. By always setting the temperature of the reticle 2 ′ in the standby state to a predetermined state, it is possible to predict and correct the expanded state in the next exposure state with high accuracy.

  As described above, while measuring the expansion / contraction state of the reticle 2 ′, cooling is performed by the cooling fans 61, 61 ′ to the expansion / contraction state that is a predetermined temperature state, and the next exposure is started. For this reason, the expansion state of the reticle 2 ′ generated by exposure can be predicted with high accuracy and can be corrected. In the prediction of the expansion state of the reticle 2 ′, the state (shape and generation amount) changes depending on parameters such as the exposure area, reticle transmittance, and illumination conditions. The expansion state is predicted depending on the parameter information and the exposure amount (or the elapsed time during exposure). Several methods have conventionally been proposed for predicting the amount of change with respect to the elapsed time. However, accurate correction cannot be made unless the state of prediction start is accurately grasped. Therefore, according to the first embodiment, correction with higher accuracy is possible.

  With reference to FIG. 11, another cooling means will be described. FIG. 11A is a view of the reticle 2 ′ seen from the side, and FIG. 11B is a view seen from the top. Reticle adsorbing portions 62a, 62b, 62c, and 62d that also serve as a heat absorbing member that absorbs the heat of the reticle 2 'are configured in the reticle transport system 21. The reticle attracting members 62a, 62b, 62c and 62d are composed of Peltier elements and can be heated and cooled. The heat absorbing members 62a, 62b, 62c, and 62d cool the peripheral portion of the reticle 2 '. The four heat absorbing members 62a, 62b, 62c, 62d can be independently controlled in temperature, and can be heated in some cases. That is, the in-plane temperature distribution of the reticle 2 'can be controlled so that the local temperature distribution of the reticle 2' can be predetermined. On the other hand, the temperature of the heat absorbing members 62a, 62b, 62c, and 62d is controlled so that the reticle 2 ′ is in a predetermined state while being monitored by the method shown in FIG. .

  With reference to FIG. 12, another cooling means for reticle 2 'will be described. FIG. 12 (a) shows the reticle 2 'from above, and FIG. 12 (b) is a side view. In FIG. 12A, the reticle transport system 21 includes a portion that adsorbs the periphery of the reticle 2 'and a non-contact heat absorber 63 at the center. The heat absorber 63 is composed of a Peltier element and cools the reticle 2 '. The heat absorber 64 is also configured below the reticle 2 '. Similarly to the heat absorber 63, the heat absorber 64 also absorbs the heat of the reticle 2 '. The expansion / contraction state of the reticle 2 'is measured by the method shown in FIGS.

  Further, another cooling means for controlling the temperature of the reticle 2 'will be described with reference to FIG. A pellicle frame 65 constituting a pellicle (not shown) is provided below the pattern surface of the reticle 2 '. The pellicle frame 65 is made of a metal member and has good heat conductivity. The temperature of the pellicle frame 65 is lowered with respect to the pellicle frame 65 by the above-described cooling fan, Peltier element, or the like. Since the pellicle frame 65 is made of a metal member, it absorbs the heat of the reticle 2 'itself. As described above, by lowering the temperature of the reticle 2 ′, it becomes possible to maintain a predetermined expansion / contraction state, which is a predetermined temperature state, and since exposure is started in this state, the thermal expansion of the reticle 2 ′ during exposure is performed. Can be predicted and corrected with high accuracy.

  According to the first embodiment, a standby reticle that is not exposed is set to a predetermined expansion / contraction state that is a predetermined temperature condition, and exposure is always started from the predetermined expansion / contraction state. Since it always starts from a predetermined stretched state at the start of exposure, the thermal expansion during the exposure is predicted with high accuracy. Exposure by high-precision alignment can be performed by correcting exposure based on the predicted expansion value. Further, it is not necessary to measure the expansion and contraction of the reticle at the time of exposure, thereby improving the throughput.

Next, with reference to FIG. 4, a two-stage exposure apparatus having a plurality of wafer stages according to a modification of the first embodiment of the present invention will be described.
Although Embodiment 1 of FIG. 1 is an exposure apparatus having one wafer stage 8, a modification of Embodiment 1 of FIG. 4 is a two-stage exposure apparatus having a plurality of wafer stages.
The two-stage exposure apparatus according to the modification of the first embodiment includes a plurality of wafer stages that move between a measurement region for measuring alignment and an exposure region for exposure, thereby further improving throughput. Regarding the reference numerals shown in FIG. 4, the same constituent elements in FIG.

Compared with the single-stage exposure apparatus of the first embodiment of FIG. 1, the two-stage exposure apparatus of the modification of the first embodiment of FIG. 4 differs from the measurement area for measuring alignment and the exposure area to be exposed. A plurality of wafer stages 8a and 8b (substrate stages).
A plurality of these two measurement areas and exposure areas are exposed, and a plurality of wafers are exposed while being switched so that two wafer stages 8a and 8b alternately perform measurement and exposure in the modification of the first embodiment.
As an advantage of having such a configuration, it is possible to perform measurements such as alignment in parallel during the exposure operation, and it is possible to lengthen the time spent for the measurement. Therefore, high-precision exposure is performed by performing multiple measurements, increasing the number of measurement shots, and performing various measurements. That is, since measurement can be performed simultaneously with exposure, throughput is improved.

  In the measurement region, alignment marks (not shown) formed on the wafers 6 a and 6 b are sequentially measured by the position detection device 4. By this measurement, a shot arrangement formed on the wafers 6a and 6b is calculated, and global alignment measurement is performed. Prior to this global alignment measurement, the reference marks 15a and 15b formed on the wafer stages 8a and 8b are measured, and the relative relationship between the reference marks 15a and 15b and the wafers 6a and 6b is measured.

  When the global alignment measurement is completed, information on the height (focus) direction of the wafers 6a and 6b is then measured by the focus detection devices 5 and 5 '. The focus detection devices 5 and 5 'are fixed with respect to the exposure device, and measure the height (Z direction) of the entire surfaces of the wafers 6a and 6b while the wafer stages 8a and 8b are driven in the XY directions. Regarding the focus direction, before measuring the heights of the wafers 6a and 6b, the reference marks 15a and 15b are measured by the focus detection devices 5, 5 ', and the relative relationship between the reference marks 15a and 15b and the wafers 6a and 6b is measured. Is detected.

  Basically, when the alignment mark measurement and focus measurement are completed, the wafer stage moves to the exposure region while holding the wafer. Here, it is important to drive without changing the relative relationship between the wafer and the reference mark. For the wafer stage moved to the exposure area, the relative position (XY direction and focus direction) between the reference mark 15 and a calibration mark (not shown) formed on the reticle 2 shown in FIG. 2 is detected by exposure light. The detection method is based on the method shown in FIG. Thereby, the relationship between the reticle 2 and the wafer stage 8a is obtained, and when the relationship between the reticle 2 and the wafer stage 8a is obtained, an exposure operation is performed based on the shot arrangement information and the focus information measured in the measurement region.

  In the above, the operation in the space of the wafer stage has been described, but the configuration of the space of the reticle will be described below. A reticle transport system 21 for mounting the reticles 2 and 2 'on the reticle stage 20 shown in FIG. The reticle transport system 21 constitutes two suction portions 30 and 30 ′ fixed to the rotating shaft 28. The suction units 30 and 30 ′ suck the reticles 2 and 2 ′ and attach and detach them on the reticle stage 20 by a rotating operation. For example, when the two reticles 2 and 2 ′ are exposed alternately, the reticle transport system 21 is rotated, and is alternately attached and detached for exposure.

With reference to FIG. 5, the two-stage exposure apparatus of the modification of Embodiment 1 by the double exposure method is demonstrated. Three types of methods will be described with respect to an exposure sequence when two types of reticles are double-exposed on a plurality of wafers 6a and 6b.
The “Metro” column indicates the wafer number processed in the measurement area, and the “Expo” column indicates the wafer number processed in the exposure area at that time. A shaded cell indicates the wafer stage 8a, and a white portion indicates one wafer stage 8b. “Reticle” indicates the type of the reticle 2, and two types of reticles “A” and “B” are alternately switched to perform exposure.

  In FIG. 5A, the first wafer (No. 1) performs alignment measurement (first row), and the reticle A is exposed. At the same time, no. Alignment measurement is performed on the second wafer (second row). Next, no. The second wafer is driven to the exposure region, and the reticle A is similarly exposed. At that time, no. The first wafer returns to the measurement area and waits for exposure of the next reticle B (third line). No. When the exposure of the wafer No. 2 is completed, the reticles A and B are exchanged, and at the same time, 2 and No. No. 1 wafer is replaced, and then the reticle B is No. 1. Exposure is performed on one wafer (fourth row). No. When the exposure of the wafer No. 1 is completed, 2 is replaced, and the pattern of the reticle B is exposed to this wafer. In parallel with this, No. for which exposure was completed is shown. 1 is carried out of the apparatus, and the next No. 1 is transferred. 3 wafers are carried in and alignment measurement is performed (line 5). Hereinafter, as shown in the drawing, the reticle B and the reticle A are alternately replaced, the wafer is also alternately replaced, and the exposure is repeated. This exposure sequence reduces the number of reticle exchanges, and improves the throughput when the time required for reticle exchange is long.

FIG. 5B differs from FIG. After the exposure of the reticle A to the second wafer, the wafer remains in the exposure region as it is, the reticle B is replaced, and the reticle B is exposed (line 4). Then, no. One wafer is transferred to the exposure region to expose the reticle B.
As described above, with respect to FIG. 5A, the frequency of exchanging the wafer can be reduced, and the throughput is improved when the exchange time of the wafer stage is long.

  In FIGS. 5A and 5B described above, the exposure order of reticles A and B is different for a plurality of wafers. Depending on the heat accompanying exposure, the wafer may expand. In such a case, if the order of the reticles A and B having different exposure amounts is switched, the expansion due to the exposure is different, so that the alignment accuracy may deteriorate. In this case, the reticle exposure order and the wafer exposure order are all performed in the same order and corrected with a certain offset, so that high accuracy can be achieved. FIG. 5C shows the exposure sequence in this way. In this sequence, the order of the reticle with respect to the wafer and the order of exposing the wafer can be adjusted for all the wafers. However, as described above, since reticle exchange and wafer exchange are frequent, the throughput may be reduced in consideration of the time required for them. As described above, throughput is improved by selecting a sequence according to required accuracy.

  In the above sequence, double exposure is performed using a plurality of reticles. What should be noted here is, for example, the behavior of the reticle B carried out with respect to the reticle A being exposed. Usually, the reticle is a quartz film having a pattern of a metal film such as Cr. When exposed, the reticle absorbs the exposure light and expands due to heat generation. While exposure is being performed, expansion proceeds to a saturation state where heat dissipation and absorption are balanced. Conversely, when exposure stops, cooling proceeds and shrinkage occurs. That is, the reticle repeatedly expands and contracts due to exposure and pause. Such reticle expansion and contraction generates a so-called alignment error. Therefore, it is necessary to perform exposure so as to suppress generation as much as possible or to correct the generation amount.

  In the double exposure method, the exposed reticle expands and the waiting reticle contracts. For example, while the reticle A is being exposed, the reticle A expands while the reticle B contracts. In the conventional example of exposing a wafer using a single reticle, the expansion state is monitored by calibration measurement, the optical performance such as magnification and distortion of the projection optical system is adjusted, and the drive operation of the reticle stage is controlled. However, it was possible to perform exposure while reducing alignment errors. However, in the double exposure method, since it is changed after the exposure, a cooling state is always generated. Therefore, if the contracted state is not managed, the alignment performance is deteriorated.

  FIG. 3 is a graph schematically showing changes in expansion / contraction (magnification error) caused by heating and cooling of the reticle 2 '. The horizontal axis indicates the elapsed time, and the vertical axis indicates the magnification error of the reticle 2 '. Since expansion occurs in the exposure state, the magnification component increases. On the other hand, when the reticle 2 ′ moves to the standby state, it is cooled (heat radiation) and contraction occurs. In this way, expansion and contraction occur repeatedly. In FIG. 3, although it is expressed as a magnification component, it may also occur as a higher-order error component such as distortion, but the concept is the same, and detailed description thereof is omitted.

When such expansion and contraction are repeated, the state of timing for starting control is important.
For example, in the previous expansion and cooling (standby state), the control accuracy differs when the timing at which the next exposure is started is point A and when it is point B. That is, when the next exposure is started at point A, the expanded state cannot be accurately predicted or corrected without accurately grasping the cooling state up to that point. Conversely, in a steady state such as point B, only the expansion component starting from that point can be predicted and corrected with high accuracy.

  In the double exposure method according to the first embodiment, the modified example of the first embodiment, and the second embodiment, the temperature of the reticle 2 in the standby state is set to a predetermined expansion / contraction state, and exposure is always started from the same predetermined expansion / contraction state at the start of exposure. Done. Therefore, exposure is performed while accurately predicting and correcting the expanded state of the reticle 2 during exposure. For this reason, the alignment error which generate | occur | produces in the exposure apparatus of a double exposure method is reduced.

[Embodiment of Device Manufacturing Method]
Next, a method for manufacturing a device (semiconductor device, liquid crystal display device, etc.) according to an embodiment of the present invention will be described. In this method, an exposure apparatus to which the present invention is applied can be used.
A semiconductor device is manufactured through a pre-process for producing an integrated circuit on a wafer (semiconductor substrate) and a post-process for completing an integrated circuit chip on the wafer produced in the pre-process as a product. The pre-process may include a step of exposing the wafer coated with the photosensitive agent using the above-described exposure apparatus, and a step of developing the wafer exposed in the step. The post-process can include an assembly process (dicing, bonding) and a packaging process (encapsulation). Moreover, a liquid crystal display device is manufactured by passing through the process of forming a transparent electrode. The step of forming the transparent electrode includes a step of applying a photosensitive agent to a glass substrate on which a transparent conductive film is deposited, a step of exposing the glass substrate on which the photosensitive agent is applied, using the above-described exposure apparatus, and the step And developing the glass substrate exposed in step (b).
The device manufacturing method of this embodiment is more advantageous than the conventional one in at least one of device productivity, quality and production cost, and safety.
As mentioned above, although preferable embodiment of this invention was described, this invention is not limited to these embodiment, A various deformation | transformation and change are possible within the range of the summary.

DESCRIPTION OF SYMBOLS 1 Illumination system, 2 Reticle, 3 Projection optical system, 4 Position detection apparatus, 5 Focus position detection apparatus, 6 Wafer, 7 Interferometer mirror, 8 Wafer stage, 9 Interferometer, 10 Stage control system, 11 Reticle alignment scope, 12 Reticle set mark, 14 control means, 15 reference mark, 20 reticle stage

Claims (7)

In an exposure apparatus that exposes a plurality of original plate patterns on a substrate by double patterning,
A stage that carries the original and moves,
Holding means for holding an original to be exposed next to the original mounted on the stage;
Temperature adjusting means for adjusting the temperature of the original plate held by the holding means;
An exposure apparatus comprising: control means for controlling the temperature adjusting means.   2. The exposure apparatus according to claim 1, further comprising a plurality of substrate stages that move between a measurement area for measuring alignment and an exposure area for exposure. An expansion / contraction monitor for measuring the expansion / contraction state of the original plate held by the holding means;
The exposure apparatus according to claim 1, wherein the control unit controls the temperature adjusting unit based on a measurement result of the extension monitor.   4. The exposure apparatus according to claim 3, wherein the expansion / contraction monitor measures a position of a position detection mark formed on the original.   5. The exposure apparatus according to claim 3, wherein the expansion / contraction monitor is a thermography for measuring a temperature of the original plate.   6. The exposure apparatus according to claim 1, wherein the cooling unit includes at least one of a pellicle frame, a cooling fan, and a Peltier element made of a metal member. A step of exposing the substrate using the exposure apparatus according to claim 1;
And a step of developing the substrate exposed in the step.

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