JP4726232B2 - Exposure method, exposure apparatus, and device manufacturing method - Google Patents

Description

  The present invention relates to an exposure method, an exposure apparatus, and a device manufacturing method for exposing a substrate with extreme ultraviolet light via a reflective reticle.

  Conventionally, reduction projection exposure using ultraviolet rays has been performed as a printing (lithography) method for manufacturing fine semiconductor elements such as semiconductor memories and logic circuits. The minimum dimension that can be transferred by reduction projection exposure is proportional to the wavelength of light used for transfer and inversely proportional to the numerical aperture of the projection optical system. For this reason, in order to transfer a fine circuit pattern, the wavelength of light used has been shortened, and used as a mercury lamp i-line (wavelength 365 nm), a KrF excimer laser (wavelength 248 nm), and an ArF excimer laser (wavelength 193 nm). The wavelength of ultraviolet light has become shorter.

  However, semiconductor elements are rapidly miniaturized, and there is a limit to reduction projection exposure in lithography using ultraviolet light. Therefore, a reduction projection exposure apparatus using extreme ultraviolet light (EUV light) having a wavelength of about 10 to 15 nm, which is shorter than ultraviolet light, has been developed in order to efficiently burn a very fine circuit pattern of less than 0.1 μm. Has been.

  In the EUV light region, the absorption of light by a substance becomes very large. Therefore, a lens optical system using light refraction as used in visible light and ultraviolet light is not practical, and is not reflected in an exposure apparatus using EUV light. An optical system is used. In this reflective optical system, a reflective reticle in which a pattern to be transferred by an absorber is formed on a mirror is also used.

  As a reflection type optical element that constitutes an exposure apparatus using EUV light, there are a multilayer mirror and a grazing incidence total reflection mirror. Since the real part of the refractive index is slightly smaller than 1 in the EUV region, total reflection occurs when used at an oblique incidence where EUV light is incident on the surface. Usually, a high reflectivity of several tens of percent or more can be obtained at an oblique incidence within several degrees as measured from the surface. However, the degree of freedom in optical design is small, and it is difficult to use a total reflection mirror for a projection optical system.

  As a mirror for EUV light used at an incident angle close to normal incidence, a multilayer mirror in which two kinds of substances having different optical constants are alternately stacked is used. For example, molybdenum and silicon are alternately laminated on the surface of a glass substrate polished to a precise surface shape. The thickness of the layer is, for example, about 0.2 nm for the molybdenum layer, about 0.5 nm for the silicon layer, and about 20 layers. The sum of the thicknesses of two kinds of substances is called a film cycle. In the above example, the film period is 0.2 nm + 0.5 nm = 0.7 nm by adding the thickness of each material layer.

When EUV light is incident on such a multilayer mirror, EUV light having a specific wavelength is reflected. When the incident angle is θ, the wavelength of the EUV light is λ, and the film period is d, approximately Bragg's equation (1),
2 × d × sin θ = λ (1)
Only EUV light with a narrow bandwidth centered on λ that satisfies the above relationship is efficiently reflected. The bandwidth at this time is about 0.6 to 1 nm.

  The reflectivity of the reflected EUV light is about 0.7 at the maximum, and the EUV light that is not reflected is absorbed in the multilayer film or the substrate, and most of the energy becomes heat. Multilayer mirrors have a greater light loss than visible light mirrors, so it is necessary to minimize the number of mirrors. At this time, in order to realize a wide exposure area with a small number of mirrors, the reticle and wafer are simultaneously scanned using only a thin arc-shaped area (ring field) separated from the optical axis by a wide area. Is transferred (scan exposure).

  FIG. 8 shows a schematic diagram of a reduction projection exposure apparatus using EUV light as a conventional example. The apparatus includes an EUV light source, an illumination optical system, a reflective reticle, a projection optical system, a reticle stage, a wafer stage, an alignment optical system, a vacuum system, and the like.

  For example, a laser plasma light source is used as the EUV light source. In this method, a target material placed in a vacuum vessel is irradiated with high-intensity pulsed laser light from a light source 801 to generate high-temperature plasma, and EUV light having a wavelength of, for example, about 13 nm is emitted from the target material. . As a target material supplied by the target supply device 802, a metal thin film, an inert gas, a droplet, or the like is used, and the target material is supplied into the vacuum vessel by means such as a gas jet. In order to increase the average intensity of the emitted EUV light, the pulse laser should have a high repetition frequency, and is usually operated at a repetition frequency of several kHz.

  The illumination optical system includes a plurality of multilayer films or oblique incidence mirrors (803, 804, 805), an optical integrator 806, and the like. The first stage condensing lens 807 serves to collect EUV light emitted from the laser plasma almost isotropically. The optical integrator 806 has a role of uniformly illuminating the mask with a predetermined numerical aperture. In addition, an aperture for limiting an area illuminated by the reticle surface to an arc shape is provided at a position conjugate with the reticle of the illumination optical system.

  The projection optical system uses a plurality of mirrors (808 to 811). When the number of mirrors is small, the use efficiency of EUV light is high, but aberration correction becomes difficult. The number of mirrors necessary for aberration correction is about 4 to 6. The shape of the reflecting surface of the mirror is a convex or concave spherical or aspherical surface. The numerical aperture NA is about 0.1 to 0.3. The mirror is made by grinding and polishing a substrate made of a material such as low expansion coefficient glass or silicon carbide, which has high rigidity and high hardness, and a low coefficient of thermal expansion. A multilayer film such as silicon is formed. When the incident angle is not constant depending on the location in the mirror plane, as is clear from the Bragg equation described above, the wavelength of EUV light whose reflectivity increases depending on the location in a multilayer film with a constant film period shifts. Therefore, it is necessary to provide a film period distribution so that EUV light having the same wavelength is efficiently reflected in the mirror plane.

  Reticle stage 812 and wafer stage 813 have a mechanism that scans synchronously at a speed ratio proportional to the reduction magnification. Here, a coordinate system is set in which the scanning direction is X in the reticle or wafer surface, Y is the direction perpendicular to the scanning direction, and Z is the direction perpendicular to the reticle or wafer surface.

  The reticle 814 is held by a reticle chuck 815 on the reticle stage 812. The reticle stage 812 has a mechanism that moves at high speed in the X direction, and has a fine movement mechanism that corrects the inclination of the angle in the X direction, the Y direction, the Z direction, and the rotation direction around each axis so that the reticle can be positioned. It has become. The position and orientation of the reticle stage are measured by a laser interferometer, and the position and orientation are controlled based on the result.

  Wafer 816 is held on wafer stage 813 by wafer chuck 817. The wafer stage 813 has a mechanism that moves at high speed in the X direction, like the reticle stage. Further, a fine movement mechanism is provided in the X direction, the Y direction, the Z direction, and the rotation direction around each axis so that the wafer can be positioned. The position and orientation of the wafer stage are measured by a laser interferometer, and the position and orientation are controlled based on the result.

  The alignment detection optical system (818, 819) is performed by, for example, an off-axis bright field illumination image processing detection system as in the ArF exposure apparatus, and performs wafer alignment while having a predetermined baseline amount. .

  In addition, the focus position in the Z direction is measured on the wafer surface by the focus position detection optical system 820, and the position and angle of the wafer stage are controlled so that the wafer surface is always kept at the image formation position by the projection optical system during exposure. Is possible.

  When one scan exposure is completed on the wafer, the wafer stage is stepped in the X and Y directions and moved to the next scan exposure start position, and the reticle stage and wafer stage are again proportional to the reduction magnification of the projection optical system. Synchronous scanning is performed in the X direction at a speed ratio. In this manner, the operation of synchronously scanning the reduced projection image of the reticle while it is formed on the wafer is repeated (step-and-scan). Thus, the reticle transfer pattern is transferred onto the entire wafer surface.

  FIG. 9 is a configuration diagram of conventional reticle alignment. In the present specification, hereinafter, the reticle, which is the original plate, and the mask are collectively referred to as “reticle”.

  Reticle alignment performs relative alignment between a “reticle reference mark” accurately positioned on the apparatus main body and a “reticle alignment mark” on the reticle. In FIG. 9, alignment light having a wavelength different from that of exposure light is reflected by the prism 80 toward the reticle 1 to illuminate the reticle reference mark 60 and the reticle alignment mark 4. The light from these marks is changed in the direction of the optical path by the bending mirror 70 and directed to the image pickup device 10 through the optical system 40, and both mark images of the reticle reference mark 60 and the reticle alignment mark 4 are formed on the image pickup device 10. Form an image. Then, the amount of positional deviation with respect to the main body of the reticle 1 is calculated from the positional relationship between the images of both marks. Based on the result, the reticle stage 812 is driven by a driving device (not shown) to align the reticle alignment mark 4 and the reticle reference mark 60. When this alignment is performed, the alignment between the reticle and the exposure apparatus main body ends.

For example, Patent Document 1 discloses a technique relating to a method for producing a reflective mask and an exposure apparatus using the reflective mask.
Japanese Patent Laid-Open No. 7-240363

  However, Patent Document 1 relates exclusively to a method for producing a reflective mask, and does not specifically teach a method or apparatus for accurately aligning a reflective mask and a wafer. Considering reticle alignment in X-ray reduction projection exposure equipment (EUVL), because the reticle used is a reflective reticle, both the “reticle reference mark” and “reticle alignment mark” mark images as in the conventional example are “ It is impossible to detect the image at the same time through the transmission.

  In addition, since the reflective reticle and the multilayer mirror are optimized to have high reflectivity with EUV light, there is a possibility that sufficient reflectivity cannot be obtained for alignment light that is non-exposure light. . In other words, when considering so-called “TTL (Through The Lens) alignment”, which is performed via a reflective reticle by non-exposure light and a multilayer mirror, the “reticle alignment mark” on the reflective reticle and the mark on the wafer side In the alignment, since the reflectance of the reticle alignment mark is low with respect to the alignment light, the image detection signal may be lowered.

  Here, in a normal projection exposure apparatus, a method of aligning a reticle and a wafer via a projection lens is called TTL alignment, but in an EUV exposure apparatus, the projection optical system is not a lens but a multilayer mirror optical system. Although it is generally difficult to say TTL because it is constituted by a system, in the present application, for ease of explanation, an alignment method using a multilayer mirror optical system is also defined as TTL alignment in a broad sense and used in the description. Shall.

  An object of the present invention is to enable accurate alignment of a reflective reticle.

An exposure method for exposing the substrate held on the substrate stage with extreme ultraviolet light via the reflective reticle held on the reticle stage and the projection optical system according to the present invention that achieves the above object,
Using the first detection system including the first imaging device, reflected light from the alignment mark provided on the reflective reticle held on the reticle stage at the first position is reflected on the first imaging device. Detecting a position of the alignment mark with respect to the first imaging device,
Using the first detection system, the first imaging device detects reflected light from a first reference mark provided on the reticle stage at a second position different from the first position. A second detection step of detecting a position of the first reference mark with respect to the first imaging device;
From the first reference mark provided on the reticle stage at a third position different from the first position and the second position, using a second detection system including a second imaging device. of the reflected light, the projection optical system, the second reference mark and the second reference mark provided on the substrate stage, such is in the position as to be positioned on the exposure axis, the second via A third detection step of detecting a position of the first reference mark with respect to the second imaging device by detecting with an imaging device;
The second position, the third position, the position of the first reference mark detected in the second detection step, and the position of the first reference mark detected in the third detection step A baseline step for determining a baseline as a distance between an optical axis of the first detection system and an exposure axis ,
Based on the first position, the position of the alignment mark detected in the first detection step, and the baseline obtained in the baseline step, the reflective reticle is positioned with respect to the exposure axis. A positioning step for positioning the reticle stage to match ,
And an exposure step of exposing the substrate with extreme ultraviolet light through the reflective reticle held on the reticle stage positioned in the positioning step.

Alternatively, according to the present invention for achieving the above object, an exposure apparatus for exposing a substrate with extreme ultraviolet light via a reflective reticle,
A reticle stage that holds and moves the reflective reticle;
A projection optical system for projecting a pattern provided on the reflective reticle held on the reticle stage onto the substrate;
A substrate stage for holding and moving the substrate;
A first detection system including a first imaging device;
A second detection system including a second imaging device,
By detecting the reflected light from the alignment mark provided on the reflective reticle held on the reticle stage at the first position using the first detection system, by the first imaging device, Detecting the position of the alignment mark relative to the first imaging device;
Using the first detection system, the first imaging device detects reflected light from a first reference mark provided on the reticle stage at a second position different from the first position. By detecting the position of the first reference mark with respect to the first imaging device,
Using the second detection system, the reflected light from the first reference mark provided on the reticle stage at a third position different from the first position and the second position, a projection optical system, since the second reference mark is detected through the reference mark and the second provided on said substrate stage is positioned so as to position on the exposure axis, the second imaging Detecting the position of the first fiducial mark relative to the device;
Based on the second position, the third position, the position of the first reference mark with respect to the first imaging device, and the position of the first reference mark with respect to the second imaging device. Obtain the baseline as the distance between the optical axis of the detection system 1 and the exposure axis ,
Based on the first position, the position of the alignment mark, and the baseline , the reticle stage is positioned so as to align the reflective reticle with respect to the exposure axis ,
The substrate is exposed to extreme ultraviolet light through the reflective reticle held on the positioned reticle stage and the projection optical system.

  According to the present invention, it is possible to accurately align a reflective reticle.

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

<First Embodiment>
FIG. 1 is a view for explaining a first embodiment of an alignment apparatus according to the present invention, and is a configuration diagram of reticle alignment in a reduced X-ray exposure apparatus (EUV). The reticle alignment is characterized in that an image is detected by scanning the reticle stage 6 for a positional shift between the reticle stage reference mark (2, 3) on the reticle stage 6 and the reticle alignment mark (4, 5) on the reticle 1. . FIG. 10 is a flowchart showing an outline of processing showing the procedure of the alignment method.

  The details of the processing will be specifically described below. The alignment light emitted from the illumination source 20 and having a wavelength different from that of the exposure light (step S1010) is changed in direction by the optical system 40 (step S1020) and guided to the bending mirror 50. The bending mirror 50 is disposed in a region where the exposure light is not shielded, and the position thereof is fixed or movable. The alignment light whose direction of the optical path has been changed by the bending mirror 50 has its principal ray incident perpendicularly to the reticle stage 6 and the reticle 1 (step S1030).

  The alignment light reflected by the reticle stage reference mark 2 on the reticle stage 6 is directed to the imaging device 10 via the bending mirror 50 and the optical system 40, and the reticle stage reference mark 2 forms an image on the imaging device 10.

  Subsequently, the reticle stage is sequentially scanned by a predetermined amount in a predetermined direction so that the reticle alignment marks 4 and 5 and the reticle stage reference mark 3 are imaged on the imaging apparatus 10 (step S1040), and the respective positional deviations are calculated (step S1040). S1050). Here, reticle stage reference marks 2 and 3 and reticle alignment marks 4 and 5 are arranged at the same height in the Z direction in advance for ease of construction. However, the defocus characteristic of each mark image may be detected to detect the height in the Z direction.

  Note that the reticle reference mark 60 is accurately positioned in the apparatus main body system, and the image of the reticle reference mark 60 is imaged on the imaging apparatus 10 by illumination light from another illumination source 30, thereby including the imaging apparatus 10. In addition, it is possible to periodically measure changes with time of the detection optical system.

  In addition, since reticle stage reference marks 2 and 3 are arranged on reticle stage 6, the reticle stage reference mark 2 and 3 are “reticle-less” (the reticle stage is not holding the reticle as the original stage) and the reticle stage scan error in the scan direction is timed. You can see changes. By capturing this change over time, the positioning of the stage can be calibrated.

  FIG. 2 is a plan view of reference mark arrangement from the Z direction in EUV mask alignment. First, it is assumed that two or more reticle stage reference marks are arranged on the reticle stage 6. Further, two or more reticle alignment marks on the reticle 1 are arranged in an area avoiding the exposure area. For example, reticle stage reference marks are MS1 to MS4, and reticle alignment marks are MA1 to MA4.

  Further, the imaging devices 200 and 201 in FIG. 2 are arranged at positions accurately positioned in the device main body system. While shifting the reticle stage in the negative direction of the X-axis, the displacement of the reticle alignment mark with respect to the reticle stage reference mark, that is, the displacement of the reticle is calculated from the positional displacement amount of each mark formed on the imaging devices 200 and 201. Can do. Specifically, first, the reticle stage 6 is scanned in the negative direction of the X axis, and the reticle stage reference marks MS1, MS2 on the reticle stage are detected using the imaging devices 200, 201. The detection method uses bright-field image processing and obtains the amount of deviation from the centers of the imaging devices 200 and 201 at this time.

  Next, if the reticle 1 is “installed on the reticle stage as designed”, the reticle stage is scanned in the negative direction of the X axis so that the reticle alignment marks MA1 to MA4 are located directly below the imaging devices 200 and 201. The positional deviation amounts (X1, Y1) to (X4, Y4) of the reticle alignment marks MA1 to MA4 imaged on the imaging devices 200 and 201 and the positional deviation amounts of the reticle stage reference marks MS3 and MS4 are determined in the bright field. Obtained using image processing. Finally, the displacement of the reticle alignment mark with respect to the reticle stage reference mark, that is, the amount of displacement of the reticle is calculated. For example, as will be described later, this misalignment occurs when the reticle and the wafer are aligned using the reticle stage reference mark and the wafer stage reference mark when the reticle is properly placed on the reticle stage. This is added to the alignment control amount as a deviation. By using this deviation, the reticle stage side is displaced so that the reticle is arranged at the design value position, or the reticle is placed on the reticle stage so as to be in a prescribed arrangement (using a reticle transport mechanism (not shown)). You may make it correct | amend by installing again.

  FIG. 3 is a diagram for explaining a specific operation of reticle alignment in the positioning apparatus according to the present invention. In order to execute alignment, two arbitrary reference marks are selected, and the geometric positional relationship between the reference marks and the imaging devices 200 and 201 is calculated. Here, assuming that the displacement amounts of the selected reticle alignment mark MA1 and reticle alignment mark MA2 are (X1, Y1) (X2, Y2), respectively, the displacement amounts of these reticle alignment marks MA1, MA2 are used. When the amount of reticle deviation (X, Y, θ) is calculated, it is as follows.

  In order to calculate the amount of reticle displacement (X, Y, θ), it is sufficient to calculate the amount of reticle displacement if there are two measurement points in the plane. For example, reticle alignment mark MA3, It is also possible to calculate the amount of reticle displacement (X, Y, θ) by imaging the amount of displacement of MA4 with an imaging device and calculating the amount of displacement (X3, Y3), (X4, Y4). . In addition, statistical processing can be performed by performing multipoint measurement as in this embodiment, and an advantageous effect can be expected, for example, an averaging effect can be expected.

<Second Embodiment>
FIG. 4 is a diagram for explaining a second embodiment of the alignment apparatus and method according to the present invention. 2 shows a configuration in which two imaging devices 200 and 201 are arranged in the negative direction of the X axis, but in the present embodiment, as shown in FIG. For example, the imaging devices 202 and 203 may be arranged in the positive direction of the X axis. At this time, when the reticle stage is scanned in the negative direction of the X axis, the imaging stage 200, 201 is used to detect the reticle stage reference marks MS1, MS2 and the reticle alignment marks MA1, MA2, and in the positive direction of the X axis. When scanning, the imaging devices 202 and 203 can be used to detect the reticle stage reference marks MS3 and MS4 and the reticle alignment marks MA3 and MA4. As a result, alignment detection can be performed only in the scan region necessary for the reticle stage to expose the EUV light, unnecessary scanning errors of the reticle stage can be reduced, and further improvement in accuracy can be expected.

  In the conventional reticle alignment, as shown in FIG. 9, it is not preferable to have a very wide gap between the reticle reference mark 60 and the reticle alignment mark 4 in terms of accuracy. However, the reticle in the first and second embodiments is not preferred. In the alignment, since the working distance between the bending mirror 50 and the reticle stage reference mark 2 can be taken freely, a degree of freedom can be given to the design of the pellicle on the reticle.

<Third Embodiment>
FIG. 5 is a view showing the arrangement of an exposure apparatus including an alignment apparatus for explaining the third embodiment. The imaging devices 10a and 10b, the illumination sources 20a and 20b, the illumination sources 30a and 30b, the optical systems 40a and 40b, the bending mirror 50a, and the reticle reference marks 60a and 60b are the imaging device 10, the illumination source 20, and the illumination source, respectively. 30, members corresponding to the optical meter 40, the bending mirror 50, and the reticle reference mark 60. Reference numeral 110 denotes a wafer chuck for holding the wafer 100, and 120 and 130 denote a θZ tilt stage and an XY stage, respectively. While irradiating EUV light, which is exposure light from the illumination system 80, onto the wafer 100 via the reticle 1 and the reflecting mirror optical system 90, the reticle stage 6 and the XY stage 130 (the θZ tilt stage 120 is also used). By scanning in synchronization, the pattern on the reticle 1 is scanned and projected on the wafer 100. The alignment light, which is non-exposure light, is irradiated from the illumination source 20b, and the non-exposure light is reflected by the half mirror 50b to illuminate the reticle stage reference mark 2. Further, the alignment light reflected by the reticle stage reference mark 2 passes through the reflection mirror optical system 90 and irradiates the stage reference mark 140 on the wafer stage.

The alignment light reflected by the stage reference mark 140 passes through the reflection mirror optical system 90 again, is reflected by the reticle stage reference mark 2, is reflected by the half mirror 50b, and is directed to the imaging device 10b. The alignment between the reticle and the wafer is executed from the relative positional relationship between the detected stage reference mark 140 and the reticle stage reference mark 2. (This is included here in the definition of on-axis TTL alignment.)
Here, the relative positional relationship between the reticle 1 and the reticle stage reference mark 2 is detected in advance by the method described in the first embodiment. It shall be.

  Subsequently, the relative positional relationship between the stage reference mark 140 and the wafer alignment mark (not shown) on the wafer 100 is also separately off-axis using an off-axis microscope that captures an image with the imaging device 150 via the optical system 160. It is detected by the method and is aligned or grasped.

  Next, the distance (baseline) between the exposure axis corresponding to ΔA in the figure and the off-axis detection system is obtained using a well-known baseline measurement method. Specifically, for example, the position of the stage reference mark 140 detected by the non-exposure light alignment light emitted from the illumination source 20b, the position of the stage reference mark 140 detected using an off-axis microscope, and the respective detection positions ΔA can be accurately obtained from the stage movement distance during placement.

  Further, in the present embodiment, since reticle alignment is also performed at a location deviating from the exposure axis, there is a distance between the exposure axis and the reticle alignment detection system corresponding to ΔB in the figure. This is defined as the baseline on the reticle side. The reticle-side base line ΔB is also normally detected by detecting the position of the reticle stage reference mark 2 by the non-exposure light alignment light emitted from the illumination source 20b and the detection system described in the first embodiment. Can be detected as accurately as baseline measurement.

  In the third embodiment, on-axis TTL alignment is performed and the reticle-side baseline and the wafer-side baseline are corrected, whereby the positional relationship between the exposure axis and the reticle-side and wafer-side off-axis detection systems can be found. Therefore, at the time of reticle replacement or periodically, the positional relationship between the reticle stage reference mark and the reticle alignment mark is detected by the method described in the first embodiment. On the other hand, each time the wafer is replaced, the stage reference mark is detected by the off-axis microscope. If the positional relationship between the wafer alignment marks is detected, all the mutual arrangement relationships are taken into account, and then the stage is set based on the positions of the reticle stage reference mark 2 and the stage reference mark 140 obtained by each off-axis system. The reticle 1 and the wafer 100 can be aligned by executing so-called off-axis global alignment in which relative alignment is performed based on the movement accuracy. In this case, on-axis TTL alignment need only be used to confirm each baseline.

  Apart from this method, in the present embodiment, the positional relationship between the reticle stage reference mark and the reticle alignment mark is detected by the method described in the first embodiment at the time of reticle replacement or periodically, while wafer replacement is performed. It is also possible to detect the positional relationship between the stage reference mark and the wafer alignment mark by the above-mentioned off-axis microscope every time and perform on-axis TTL alignment for each wafer exposure based on this data. In this case, relative alignment (global alignment) depending on the movement accuracy of the stage can be executed based on the position detection result in the on-axis TTL. In this case, it is not necessary to measure the baseline. The half mirror 50b includes a moving mechanism so as not to block EUV exposure light emitted from the illumination optical system 80. Further, it is more preferable that a plurality of wafer alignment marks and stage reference marks are provided in the same manner as the reticle side, and each of them is detected by a plurality of off-axis scopes.

  According to the present embodiment, as shown in FIG. 5, the reticle-side reference necessary for on-axis TTL alignment can be shifted from the reticle alignment mark where the reflectance, that is, the mark contrast is difficult to expect with non-exposure light, to the reticle stage reference mark. it can. As a result, on-axis TTL alignment can be performed with a reticle stage reference mark that is optimized in reflectance (mark contrast) with respect to alignment light, and alignment accuracy is improved. In particular, in this embodiment, a light source for detecting a reticle stage reference mark and a stage reference mark via a reflecting mirror optical system, a light source for detecting a reticle stage reference mark and a reticle alignment mark, a stage reference mark, Since the light source for detecting the wafer alignment mark is separated, the wavelength light suitable for on-axis TTL alignment and the wavelength light suitable for reticle mark detection and wafer mark detection Can be selected separately.

<Fourth Embodiment>
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described. FIG. 6 shows a manufacturing flow of microdevices (semiconductor chips such as IC and LSI, liquid crystal panels, CCDs, thin film magnetic heads, micromachines, etc.).

  In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask production), a mask on which the designed circuit pattern is formed is produced. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon. In step 4 (wafer process), called a pre-process, an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. Next, step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4, such as an assembly process (dicing, bonding), a packaging process (chip encapsulation), and the like. including. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, the semiconductor device is completed and shipped (step 7).

  FIG. 7 shows a detailed flow of the wafer process. In step 11 (oxidation), the wafer surface is oxidized. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed onto the wafer by exposure using the exposure apparatus described above. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.

  By using the manufacturing method of this embodiment, it is possible to manufacture a highly integrated semiconductor device that has been difficult to manufacture.

It is a schematic side view of the alignment apparatus which shows the structure of the reticle alignment concerning this invention. It is a figure explaining the process of reticle alignment concerning this invention. It is a figure explaining the process of reticle alignment in this invention. It is a figure explaining 2nd Embodiment concerning this invention. It is a figure which shows the structure at the time of applying an alignment apparatus to EUV exposure apparatus. It is a figure which shows the manufacture flow of a semiconductor device. It is a figure which shows the detailed flow of a wafer process. It is a figure which shows the structure of the conventional EUV exposure apparatus. It is a figure which shows the structure of the conventional reticle alignment. It is a flowchart which shows the outline of the process which shows the procedure of the alignment method.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Reflective type reticle 2, 3 Reticle stage reference mark 4, 5 Reticle alignment mark 6 Reticle stage 10 Imaging device 20 Illumination source 30 Illumination source 40 Optical system 50 Bending mirror 60 Reticle reference mark 90 Reduction projection optical system 100 Wafer 110 Wafer chuck 120 θ, Z, Tilt stage 130 X, Y stage 140 Stage reference mark 150 Off-axis scope 160 Objective lens

Claims (5)

An exposure method for exposing a substrate held on a substrate stage with extreme ultraviolet light via a reflective reticle held on a reticle stage and a projection optical system,
Using the first detection system including the first imaging device, reflected light from the alignment mark provided on the reflective reticle held on the reticle stage at the first position is reflected on the first imaging device. Detecting a position of the alignment mark with respect to the first imaging device,
Using the first detection system, the first imaging device detects reflected light from a first reference mark provided on the reticle stage at a second position different from the first position. A second detection step of detecting a position of the first reference mark with respect to the first imaging device;
From the first reference mark provided on the reticle stage at a third position different from the first position and the second position, using a second detection system including a second imaging device. of the reflected light, the projection optical system, the second reference mark and the second reference mark provided on the substrate stage, such is in the position as to be positioned on the exposure axis, the second via A third detection step of detecting a position of the first reference mark with respect to the second imaging device by detecting with an imaging device;
The second position, the third position, the position of the first reference mark detected in the second detection step, and the position of the first reference mark detected in the third detection step A baseline step for determining a baseline as a distance between an optical axis of the first detection system and an exposure axis ,
Based on the first position, the position of the alignment mark detected in the first detection step, and the baseline obtained in the baseline step, the reflective reticle is positioned with respect to the exposure axis. A positioning step for positioning the reticle stage to match ,
An exposure step of exposing the substrate with extreme ultraviolet light via the reflective reticle held on the reticle stage positioned in the positioning step;
An exposure method comprising:   In the third detection step, reflected light from the second reference mark is detected by the second imaging device via the projection optical system and the first reference mark, whereby the second detection mark is detected. The exposure method according to claim 1, wherein the position of the second reference mark with respect to the imaging device is detected. An exposure apparatus that exposes a substrate with extreme ultraviolet light via a reflective reticle,
A reticle stage that holds and moves the reflective reticle;
A projection optical system for projecting a pattern provided on the reflective reticle held on the reticle stage onto the substrate;
A substrate stage for holding and moving the substrate;
A first detection system including a first imaging device;
A second detection system including a second imaging device,
By detecting the reflected light from the alignment mark provided on the reflective reticle held on the reticle stage at the first position using the first detection system, by the first imaging device, Detecting the position of the alignment mark relative to the first imaging device;
Using the first detection system, the first imaging device detects reflected light from a first reference mark provided on the reticle stage at a second position different from the first position. By detecting the position of the first reference mark with respect to the first imaging device,
Using the second detection system, the reflected light from the first reference mark provided on the reticle stage at a third position different from the first position and the second position, a projection optical system, since the second reference mark is detected through the reference mark and the second provided on said substrate stage is positioned so as to position on the exposure axis, the second imaging Detecting the position of the first fiducial mark relative to the device;
Based on the second position, the third position, the position of the first reference mark with respect to the first imaging device, and the position of the first reference mark with respect to the second imaging device. Obtain the baseline as the distance between the optical axis of the detection system 1 and the exposure axis ,
Based on the first position, the position of the alignment mark, and the baseline , the reticle stage is positioned so as to align the reflective reticle with respect to the exposure axis ,
Exposing the substrate with extreme ultraviolet light via the reflective reticle held on the positioned reticle stage and the projection optical system;
An exposure apparatus characterized by that.   The reflected light from the second reference mark is detected by the second image pickup device via the projection optical system and the first reference mark, whereby the second image pickup device with respect to the second image pickup device is detected. 4. The exposure apparatus according to claim 3, wherein the position of the reference mark is detected. Exposing the substrate using the exposure apparatus according to claim 3;
Developing the substrate exposed in the process;
A device manufacturing method characterized by comprising:

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