JP4078683B2 - Projection exposure apparatus, projection exposure method, and scanning exposure method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a projection exposure apparatus, a projection exposure method, and a scanning exposure method, and more particularly, a projection exposure apparatus and a projection exposure method for projecting and exposing a pattern image formed on a mask onto a sensitive substrate via a projection optical system. In addition, the present invention relates to a scanning exposure method, and is particularly characterized by methods for focus control and leveling control.
[0002]
[Prior art]
Conventionally, various exposure apparatuses have been used for manufacturing a semiconductor element or a liquid crystal display element in a photolithography process. Currently, a pattern of a photomask or a reticle (hereinafter, collectively referred to as “reticle”) is used. In general, a projection exposure apparatus that transfers an image onto a substrate such as a wafer or a glass plate (hereinafter, referred to as a “sensitive substrate” as appropriate) having a photosensitive material such as a photoresist coated on the surface via a projection optical system. in use. In recent years, as this projection exposure apparatus, a sensitive substrate is placed on a two-dimensionally movable substrate stage, and the sensitive substrate is stepped (stepped) by this substrate stage, so that the pattern image of the reticle is placed on the sensitive substrate. The so-called step-and-repeat type reduction projection exposure apparatus (so-called stepper), which repeats the operation of sequentially exposing each shot area, is the mainstream.
[0003]
Recently, a step-and-scan type projection exposure apparatus (for example, a scanning exposure apparatus as described in Japanese Patent Application Laid-Open No. 7-176468), which is an improvement on a static exposure apparatus such as a stepper, has also been developed. It has come to be used relatively frequently. This step-and-scan type projection exposure apparatus can expose a large field with a smaller optical system as compared with (1) a stepper. Therefore, the projection optical system can be easily manufactured and the number of shots by large field exposure can be reduced. High throughput can be expected due to the decrease, and (2) there are advantages such as an effect of averaging by relatively scanning the reticle and wafer with respect to the projection optical system, and an improvement in distortion and depth of focus. Furthermore, as the integration density of semiconductor devices increases from 16M (mega) to 64M DRAM, and in the future to 256M, 1G (giga), and so on, the large field becomes essential, so it replaces the stepper. Therefore, it is said that scanning projection exposure apparatuses will become mainstream.
[0004]
Therefore, when the sensitive substrate is exposed using this scanning projection exposure apparatus, it is provided on the near side in the scanning direction with respect to the exposure field, as described in, for example, JP-A-6-283403. All the detection points in one row are used as sample points, and all the focus position values at the sample points are measured in advance before exposure, and averaging processing and filtering processing are performed. Controls the focus and auto leveling mechanism. In parallel with this, so-called complete look-ahead control in which the inclination in the non-scanning direction is obtained by the least square approximation method from the focus position measurement values at each sample point in the above-mentioned row, and the leveling control in the non-scanning direction is performed by open control. The law was being implemented.
[0005]
[Problems to be solved by the invention]
Since this type of projection exposure apparatus is mainly used as a mass-production machine for semiconductor elements and the like, it is possible to improve the throughput, that is, the throughput of how many wafers can be exposed within a certain period of time. Is inevitably required.
[0006]
In this regard, in the case of the above-described step-and-scan projection exposure apparatus, when exposing a large field, as described above, the number of shots exposed in the wafer is reduced, so that an improvement in throughput is expected. However, since exposure is performed during constant-velocity movement by synchronous scanning of the reticle and wafer, an acceleration / deceleration area is required before and after the constant-velocity movement area, and a shot equivalent to the shot size of the stepper is assumed. In the case of exposure, the throughput may be lower than that of the stepper.
[0007]
The flow of processing in this type of projection exposure apparatus is roughly as follows.
[0008]
(1) First, a wafer loading process is performed in which a wafer is loaded onto a wafer table using a wafer loader.
[0009]
(2) Next, a search alignment process is performed in which a rough position detection of the wafer is performed by the search alignment mechanism. Specifically, this search alignment process is performed, for example, based on the outer shape of the wafer or by detecting a search alignment mark on the wafer.
[0010]
{Circle around (3)} Next, a fine alignment step for accurately obtaining the position of each shot area on the wafer is performed. In this fine alignment process, an EGA (Enhanced Global Alignment) method is generally used. In this method, a plurality of sample shots in a wafer are selected, and an alignment mark (wafer mark) attached to the sample shot is selected. Are sequentially measured, and based on this measurement result and the design value of the shot arrangement, a statistical calculation is performed by a so-called least square method or the like to obtain all shot arrangement data on the wafer (Japanese Patent Laid-Open No. 61). -44429, etc.), the coordinate position of each shot area can be obtained with relatively high accuracy with high throughput.
[0011]
(4) Next, based on the coordinate position of each shot area obtained by the above-mentioned EGA method or the like and the baseline amount measured in advance, each shot area on the wafer is sequentially positioned at the exposure position, and the projection optical system is An exposure process for transferring the pattern image of the reticle onto the wafer is performed.
[0012]
(5) Next, a wafer unload process is performed in which the wafer on the wafer table subjected to the exposure process is unloaded using a wafer unloader. This wafer unloading step is performed simultaneously with the wafer loading step (1) for the wafer to be exposed. That is, (1) and (5) constitute a wafer exchange process.
[0013]
Thus, in the conventional projection exposure apparatus, four operations are repeatedly performed using one wafer stage, such as wafer exchange → search alignment → fine alignment → exposure → wafer exchange.
[0014]
Further, the throughput THOR [sheets / hour] of this type of projection exposure apparatus is given by the following equation when the wafer exchange time is T1, the search alignment time is T2, the fine alignment time is T3, and the exposure time is T4: It can be expressed as 1).
[0015]
THOR = 3600 / (T1 + T2 + T3 + T4) (1)
The operations from T1 to T4 are repeatedly executed sequentially (sequentially) in the order of T1, T2, T3, T4, T1, and so on. For this reason, if each element from T1 to T4 is speeded up, the denominator becomes smaller and the throughput THOR can be improved. However, the above-described T1 (wafer exchange time) and T2 (search alignment time) are relatively small since only one operation is performed on one wafer. In the case of T3 (fine alignment time), the throughput can be improved by reducing the number of shots when using the EGA method described above or by reducing the measurement time of a single shot. Since accuracy is degraded, T3 cannot be easily shortened.
[0016]
T4 (exposure time) includes a wafer exposure time and a stepping time between shots. For example, in the case of a scanning projection exposure apparatus such as the step-and-scan method, it is necessary to increase the relative scanning speed of the reticle and wafer by the amount that shortens the wafer exposure time, but the synchronization accuracy deteriorates. The scanning speed cannot be increased easily.
[0017]
In addition to the above throughput in this type of projection exposure apparatus, important conditions include (1) resolution, (2) depth of focus (DOF), and (3) line width control accuracy. . The resolution R is such that the exposure wavelength is λ and the numerical aperture of the projection lens is N.P. A. (Numerical Aperture), λ / N. A. And the depth of focus DOF is λ / (NA) ² Is proportional to
[0018]
Therefore, in order to improve the resolution R (reduce the value of R), the exposure wavelength λ is reduced or the numerical aperture N.P. A. Need to be larger. In particular, the density of semiconductor elements has been increasing recently, and the device rule has become 0.2 μmL / S (line and space) or less, so illumination is necessary to expose these patterns. A KrF excimer laser is used as the light source. However, as described above, the degree of integration of semiconductor elements will inevitably increase in the future, and development of a device having a light source having a wavelength shorter than KrF is desired. As a candidate for a next-generation apparatus equipped with such a light source having a shorter wavelength, an apparatus using an ArF excimer laser as a light source, an electron beam exposure apparatus, and the like are representatively mentioned. In the case of an ArF excimer laser, oxygen In some places, light is hardly transmitted, high output is difficult to be output, laser life is short, and equipment costs are high, and in the case of electron beam exposure equipment, light exposure equipment In reality, it is difficult to develop next-generation machines with the main viewpoint of shortening the wavelength because of the disadvantage that the throughput is significantly lower than.
[0019]
As another method for increasing the resolution R, the numerical aperture N.I. A. Can be increased, but N.I. A. If is increased, there is a demerit that the DOF of the projection optical system is reduced. This DOF can be roughly divided into UDOF (User Depth of Forcus: part used on the user side: pattern step, resist thickness, etc.) and the total focal difference of the apparatus itself. Up to now, since the ratio of UDOF has been large, the direction in which the DOF is increased is the main axis of development of the exposure apparatus. For example, modified illumination has been put to practical use as a technique for increasing the DOF.
[0020]
By the way, in order to manufacture a device, a pattern in which L / S (line and space), isolated L (line), isolated S (space), CH (contact hole), etc. are combined is formed on the wafer. However, the exposure parameters for performing optimum exposure differ for each pattern shape such as L / S and isolated line. For this reason, conventionally, using a method called ED-TREE (excluding CHs with different reticles), the common is that the resolution line width is within a predetermined allowable error with respect to the target value and a predetermined DOF is obtained. Exposure parameters (coherence factor σ, NA, exposure control accuracy, reticle drawing accuracy, etc.) are determined and used as the specifications of the exposure apparatus. However, it is thought that there will be the following technical flow in the future.
[0021]
(1) Improvement in process technology (planarization on the wafer) will lead to a decrease in pattern step and a decrease in resist thickness, and UDOF may be in the range of 1 μm to 0.4 μm or less.
[0022]
(2) The exposure wavelength is shortened from g-line (436 nm) → i-line (365 nm) → KrF (248 nm). However, only light sources up to ArF (193) have been studied in the future, and the technical hurdles are high. Thereafter, the process shifts to EB exposure.
[0023]
(3) It is expected that scanning exposure such as step-and-scan will become the mainstream of steppers instead of static exposure such as step-and-repeat. This technique enables large field exposure with a projection optical system having a small diameter (especially in the scanning direction), and accordingly, a high N.D. A. It is easy to realize.
[0024]
Against the background of the technical trend as described above, the double exposure method has been reviewed as a method for improving the limit resolution, and this double exposure method is used in KrF and future ArF exposure apparatuses, and 0.1 μmL / S. Attempts have been made to expose to the maximum. In general, the double exposure method is roughly divided into the following three methods.
[0025]
(1) L / S and isolated lines with different exposure parameters are formed on separate reticles, and each layer is subjected to double exposure under optimum exposure conditions.
[0026]
(2) When the phase shift method or the like is introduced, the limit resolution is higher in the L / S with the same DOF than the isolated line. By utilizing this, all the patterns are formed with L / S by the first reticle, and an isolated line is formed by thinning out L / S with the second reticle.
[0027]
(3) Generally, the isolated line is smaller than the L / S. A. Can obtain a high resolution (however, the DOF becomes small). Therefore, all patterns are formed by isolated lines, and L / S is formed by a combination of isolated lines respectively formed by the first and second reticles.
[0028]
The above double exposure method has two effects of improving resolution and improving DOF.
[0029]
However, in the double exposure method, since it is necessary to perform the exposure process a plurality of times using a plurality of reticles, the exposure time (T4) is more than doubled as compared with the conventional apparatus, and the throughput is greatly deteriorated. In reality, the double exposure method has not been studied very seriously, and the resolution and depth of focus (DOF) can be improved by using ultraviolet exposure wavelength, modified illumination, phase shift reticle, etc. Has been done.
[0030]
However, when the double exposure method described above is used in KrF and ArF exposure apparatuses, exposure up to 0.1 μmL / S is realized, thereby developing next-generation machines aimed at mass production of 256M and 1G DRAMs. There is no doubt that it is a promising option, and the development of a new technology has been awaited for improving the throughput, which is a problem of the double exposure method that becomes a bottleneck for this.
[0031]
In this regard, if the above-described four operations, ie, wafer exchange, search alignment, fine alignment, and exposure operations, can be processed partially or simultaneously in parallel, these four operations are compared with the case of performing them sequentially. Thus, it is considered that the throughput can be improved. For this purpose, it is premised that a plurality of substrate stages are provided. Providing a plurality of substrate stages is known and seems to be simple in theory, but there are many problems that must be solved in order to achieve a sufficient effect. For example, if two substrate stages having the same size as the current situation are simply arranged side by side, the installation area (so-called footprint) of the apparatus increases remarkably, leading to an increase in the cost of a clean room in which the exposure apparatus is placed. is there. In order to achieve high-precision overlay, alignment is performed on the sensitive substrate on the same substrate stage, and then the alignment of the mask pattern image and the sensitive substrate is performed using the alignment result. Since it is necessary to perform exposure, it is impossible to simply set one of the two substrate stages exclusively for exposure and the other for alignment, for example, as a realistic solution.
[0032]
Further, in the scanning type projection exposure apparatus, the exposure order for each shot area on the wafer W is as follows: (1) scanning acceleration / deceleration time, (2) settling time, (3) exposure time, and (4) adjacent shots. Although it is determined by the parameters (1) to (4) such as the stepping time, since the acceleration / deceleration of the reticle stage is generally the rate-limiting condition, the reticle stage is moved from one side to the other side in the scanning direction and from the other side to the one side. It is most efficient to scan the wafer alternately in the direction opposite to the reticle stage (for this purpose, the wafer is stepped by one shot in the non-scanning direction after one shot exposure). Is.
[0033]
However, when performing the above-described conventional complete read-ahead control (JP-A-6-283403, etc.), it is difficult to perform exposure in the above-described most efficient exposure order. That is, when exposing a shot area near the center of the wafer, the above complete look-ahead control can be performed without any problem. However, depending on the scanning direction of a shot area existing near the wafer outer periphery or a missing shot on the outer periphery. This is because complete prefetch control may be difficult, and in order to perform full prefetch, the scanning direction must be changed from the inside to the outside of the wafer. For this reason, the throughput is reduced.
[0034]
The present invention has been made under such circumstances, First An object of the present invention is to provide a projection exposure apparatus that can perform high-precision focus and leveling control while further improving the throughput.
[0035]
Also, Second object of the present invention Can perform high-precision focus and leveling control while further improving throughput scanning It is to provide an exposure method.
[0039]
[Means for Solving the Problems]
According to the first aspect of the present invention, a pattern image is projected onto an exposure area via a projection optical system (PL), and the sensitive substrates (W1, W2) are moved in the scanning direction with respect to the exposure area. By the above Sensitive substrate Each of the multiple shot areas above A first substrate stage (WS1) capable of holding a sensitive substrate (W1) and moving in a two-dimensional plane; and holding the sensitive substrate (W2) and the first substrate stage A second substrate stage (WS2) capable of moving independently of the first substrate stage (WS1) in the same plane as (WS1); provided separately from the projection optical system (PL), and the substrate stage (WS1) Or at least one alignment system (for example, 24a) that measures a mark on the sensitive substrate (W1 or W2) held by WS2); and a sensitive substrate during mark measurement using the alignment system (24a) (for example, W1) a first detection system (for example, 130) for detecting a relative position of the surface with respect to a predetermined reference surface; and a sensitive substrate (for example, W2) surface during exposure using the projection optical system (PL). A second detection system (132) for detecting a relative position with respect to a reference plane; and provided on each of the first substrate stage (WS1) and the second substrate stage (WS2) and held on the stage (WS1 or WS2) A substrate drive system (LS) for adjusting the surface position of the sensitive substrate (W1 or W2); one of the first substrate stage (WS1) and the second substrate stage (WS2) (for example, While the mark measurement operation using the alignment system (24a) is performed while performing detection by the first detection system (130) in WS1), the projection optical system (PL) in the other stage (for example, WS2). After controlling the two stages (WS1, WS2) so that an exposure operation using the projection optical system is performed, the exposure using the projection optical system (PL) is performed on the one stage (WS1). The controls the one stage (WS1) so that the operation is carried out, When exposing a shot area in the vicinity of the outer periphery set to be scanned from the outside to the inside of the sensitive substrate, Detection result of the first detection system (130) obtained during the mark measurement operation of the one stage (WS1) In And a control means (90) for controlling the substrate driving system (LS1) of the one stage (WS1) based on the control means (90). Projection exposure apparatus .
[0040]
According to this, while the mark measurement operation using the alignment system is performed while the detection by the first detection system is performed on one of the first substrate stage and the second substrate stage by the control means, the other stage is performed. Since the two stages are controlled so that the exposure operation using the projection optical system is performed in step 1, the mark measurement operation on one stage side and the exposure operation on the other stage side are processed in parallel. It is possible to improve the throughput as compared with the conventional technique in which operations are performed sequentially.
[0041]
Further, in the control means, after the parallel processing of the mark measurement operation on the one stage side and the exposure operation on the other stage side is completed, the exposure operation using the projection optical system is performed on one stage. While controlling one stage, When exposing a shot area in the vicinity of the outer periphery set to be scanned from the outside to the inside of the sensitive substrate, The substrate drive system of one stage is controlled based on the detection result of the first detection system obtained during the mark measurement operation of one stage and the detection result of the second detection system obtained during the exposure operation of one stage. To do. For this reason, during the exposure operation of this one stage, When exposing a shot area near the outer periphery set to be scanned from the outside to the inside of the sensitive substrate, Based on the detection result of the first detection system obtained during the previous mark measurement operation, the substrate driving system of the one stage is controlled to quickly drive the surface position of the sensitive substrate to near the imaging surface of the projection optical system. be able to . As a result, it is possible to expose each shot area in an efficient exposure sequence without adopting the inner scan for the shot area in the vicinity of the outer periphery set to be scanned from the outside to the inside of the sensitive substrate as described above. Can improve throughput, and Rapid and highly accurate focus and leveling control is possible.
[0042]
From a second viewpoint, the present invention provides: In synchronization with the movement of the mask (R) in the scanning direction with respect to the illumination area (IA) illuminated with the illumination light, the sensitive substrate (W1) with respect to the exposure area (IF) conjugate to the illumination area (IA). Alternatively, the pattern image of the mask (R) can be obtained by moving W2) in the scanning direction. Via projection optics (PL) A scanning projection exposure apparatus for exposing on the sensitive substrate (W1 or W2), the first substrate stage (WS1) capable of holding the sensitive substrate (W1) and moving in a two-dimensional plane; A second substrate stage (WS2) that holds (W2) and can move independently of the first substrate stage (WS1) in the same plane as the first substrate stage (WS1); and the projection optical system (PL ) And at least one alignment system (for example, 24a) for measuring a mark on the sensitive substrate (W1 or W2) held on the substrate stage (WS1 or WS2); and the alignment system (24a) A first detection system (for example, 130) for detecting the relative position of the sensitive substrate (W1 or W2) surface during mark measurement with a predetermined reference plane; and the projection optical system (PL) A second detection system (132) for detecting a relative position of the sensitive substrate (W2 or W1) surface in the light with respect to a predetermined reference plane; and each of the first substrate stage (WS1) and the second substrate stage (WS2) A substrate driving system (LS) for adjusting the surface position of the sensitive substrate held on the stage; one of the first substrate stage (WS1) and the second substrate stage (WS2) While the mark measurement operation using the alignment system (24a) is performed while performing detection by the first detection system (130) in (for example, WS1), the projection optical system is used in the other stage (for example, WS2). After controlling the two stages (WS1, WS2) so that the exposure operation using (PL) is performed, the projection optical system (PL) is used in the one stage (WS1). When controlling the one stage (WS1) so that the optical operation is performed, the exposure area (IF) of the plurality of shot areas on the sensitive substrate (W1) held by the one stage (WS1). When exposing a shot area in the vicinity of the outer periphery set so as to be scanned from the outside to the inside of the sensitive substrate (W1), the first stage (WS1) obtained during the mark measurement operation is obtained. The stage substrate drive system (LS) is controlled based on the detection result of the first detection system (130) and the detection result of the second detection system (132) obtained during the exposure operation of the one stage (WS1). And a control means (90) for controlling the substrate driving system (LS) of the one stage (WS1) using only the detection result of the second detection system (132) when exposing other shot areas. Have Projection exposure apparatus .
[0043]
According to this, while the mark measurement operation using the alignment system is performed while the detection by the first detection system is performed on one of the first substrate stage and the second substrate stage by the control means, the other stage is performed. Since the two stages are controlled so that the exposure operation using the projection optical system is performed in the above, these operations are performed by parallel processing of the mark measurement operation on one stage side and the exposure operation on the other stage side. It is possible to improve the throughput as compared with the conventional technique that has been performed sequentially.
[0044]
Further, in the control means, after the parallel processing of the mark measurement operation on the one stage side and the exposure operation on the other stage side is completed, the exposure operation using the projection optical system is performed on one stage. When controlling a stage, shots in the vicinity of the outer periphery set so as to be scanned from the outside to the inside of the sensitive substrate with respect to the exposure region of a plurality of shot regions on the sensitive substrate held on one stage When exposing an area, based on the detection result of the first detection system obtained during the mark measurement operation of the one stage and the detection result of the second detection system obtained during the exposure operation of the one stage. The stage substrate drive system is controlled, and when the other shot areas are exposed, only the detection result of the second detection system is used to control the substrate drive system of the one stage. For this reason, during the exposure operation of this one stage, it is set so that the exposure area where the information of the surface position of the sensitive substrate at the time of exposure of the previous shot cannot be obtained is scanned from the outside to the inside of the sensitive substrate. When exposing the shot area near the outer periphery, the surface position of the sensitive substrate is controlled by controlling the substrate drive system of the one stage based on the detection result of the first detection system obtained during the mark measuring operation of one stage. Can be quickly driven close to the imaging surface of the projection optical system, and the substrate driving system can be further finely adjusted based on the detection result of the second detection system to match the sensitive substrate surface with the imaging surface. I can do it. On the other hand, when exposing a shot area that can obtain information on the surface position of the sensitive substrate at the time of exposure of the previous shot other than the above, prior to starting exposure of the shot area to be exposed, during exposure of the previous shot Based on the information on the surface position of the sensitive substrate, the substrate drive system of one stage is controlled to quickly follow the surface position of the sensitive substrate to the vicinity of the imaging surface of the projection optical system, and then obtained during exposure. The surface position adjustment (“focus / leveling” adjustment) of the sensitive substrate is performed using only the detection result of the second detection system.
[0045]
Accordingly, quick and highly accurate focus and leveling control can be performed during exposure of any shot area.
[0046]
From a third viewpoint, the present invention provides: By projecting an image of the pattern onto the exposure area via the projection optical system (PL), and moving the sensitive substrate (W1 or W2) in the scanning direction with respect to the exposure area, On sensitive substrate Each of multiple shot areas To expose scanning An exposure method, comprising two substrate stages (WS1, WS2) each holding an sensitive substrate (W1 or W2) and independently movable in the same two-dimensional plane; said two stages (WS1, The mark on the sensitive substrate (for example, W1) held on one stage (for example, WS1) of WS2) is measured; while the mark measurement operation is being performed on the one stage (WS1), The relative position of the sensitive substrate (W1) held on one stage (WS1) with respect to a predetermined reference surface is detected; while the mark measurement operation is being performed on the one stage (WS1), the two stages The sensitive substrate (W2) held on the other stage (WS2) of (WS1, WS2) ) Exposure; after completion of the exposure operation of the other stage (WS2), Set to scan from the outside to the inside of the sensitive substrate, Exposure of the sensitive substrate (W1) held on the one stage (WS1) When to The surface position of the sensitive substrate (W1) held on the one stage (WS1) is adjusted based on the detected relative position. Scanning exposure method .
[0047]
According to this, the mark on the sensitive substrate held on one of the two stages is measured and held on one stage while the mark measurement operation is being performed on the one stage. A relative position of the sensitive substrate with respect to the predetermined reference surface is detected. While the mark measurement operation is being performed in one stage in this way, the sensitive substrate held in the other of the two stages in parallel with this is performed. Board Exposed. For this reason, it is possible to improve the throughput as compared with the conventional technique in which these operations are performed sequentially by parallel processing of the mark measurement operation on one stage side and the exposure operation on the other stage side.
[0048]
Then, after the exposure operation of the other stage is finished, that is, after the parallel operation on the two stages is finished, the sensitive substrate held on one stage is exposed. Is set to be scanned from the outside to the inside of the sensitive substrate. Sensitive substrate held on one stage When exposing the shot area near the upper periphery, The surface position of the sensitive substrate held on the one stage is adjusted based on the relative position (information on the surface position) of the sensitive substrate held on the one stage previously detected with respect to the predetermined reference plane. , It is possible to quickly drive the surface position of the sensitive substrate to near the imaging plane of the projection optical system. As a result, it is possible to expose each shot area in an efficient exposure sequence without adopting the inner scan even for the shot area near the outer periphery of the sensitive substrate set to be scanned from the outside to the inside of the sensitive substrate. Can improve throughput, and Rapid and highly accurate focus and leveling control is possible.
[0069]
Ma The From a fourth viewpoint, the present invention provides: Projection exposure in which an image of a pattern is projected onto an exposure region (IF) via a projection optical system (PL), and the sensitive substrate is moved in the scanning direction with respect to the exposure region (IF), thereby exposing the sensitive substrate. In this method, a sensitive substrate (W1) is held on a first substrate stage (WS1) movable in a two-dimensional direction (X-axis direction, Y-axis direction) and independent of the first substrate stage (WS1). A sensitive substrate (W2) is held on a second substrate stage (WS2) movable in a two-dimensional direction (X-axis direction, Y-axis direction), and one of the first and second substrate stages ( For example, a measurement sequence for detecting alignment marks on the sensitive substrate (W1) held on WS1) is executed in parallel with an exposure sequence for exposing the sensitive substrate (W2) on the other substrate stage (WS2). The measurement sequence During this period, surface position information in the vicinity of the outer periphery of the sensitive substrate (W1) on one substrate stage (WS1) is detected, and a measurement sequence using one substrate stage (WS1) and the other substrate stage (WS2) are detected. After the exposure sequence using is completed, the other substrate stage (WS2) is moved to the exchange position of the sensitive substrate, and one substrate stage (WS1) is moved to the image plane side of the projection optical system (PL). A shot region (210) near the outer periphery of the sensitive substrate held on the substrate stage (WS1) is exposed so that the exposure region (IF) scans from the outside to the inside of the sensitive substrate, and a measurement sequence is being performed during the exposure. Projection exposure method for adjusting the surface position of the sensitive substrate (W1) held on one substrate stage (WS1) based on the surface position information detected in step Is .
According to this, it is possible to perform highly accurate focus and leveling control while improving the throughput.
Also, From the fifth viewpoint, the present invention A projection exposure apparatus that exposes an image of a pattern formed on a mask (R) onto a sensitive substrate (W) via a projection optical system (PL), having a reflective surface for an interferometer, and the sensitive substrate A first substrate stage (WS1) that can move in a two-dimensional direction (X-axis direction, Y-axis direction); and a first substrate stage that has a reflective surface for an interferometer and holds a sensitive substrate ( A second substrate stage (WS2) capable of moving in a two-dimensional direction (X-axis direction, Y-axis direction) independently of WS1); provided separately from the projection optical system (PL), and an alignment mark on the sensitive substrate At least one first alignment system (24a) to be detected; second to measure the relative positional relationship between the reference (FM1) provided on the substrate stage and the mark on the mask (R) via the projection optical system (PL). An alignment system (142); The surface position detection system (130) for detecting surface position information with respect to the fixed reference surface; and the first alignment system (24a) can be used to measure the position of the substrate stage in the measurement sequence for detecting the alignment mark on the sensitive substrate. Of the substrate stage in the exposure sequence that exposes the sensitive substrate using the projection optical system (PL) and the first interference measurement long axis (BI4Y) that deviates from the reflecting surface of the substrate stage after the measurement sequence ends. An interferometer system having a second interferometric measurement long axis (BI3Y) that is disposed so as to be capable of measuring a position and deviates from the reflecting surface of the substrate stage after the exposure sequence ends. The measurement sequence on one substrate stage (for example WS1) is executed in parallel with the exposure sequence on the other substrate stage (WS2), The first positional relationship between the shot area on the sensitive substrate (W1) held on the other substrate stage (WS1) and the reference (FM1) provided on one substrate stage (WS1) is obtained, and its measurement sequence During execution, the surface position information of the surface of the sensitive substrate (W1) on one substrate stage (WS1) is detected using the surface position detection system (130), and the measurement sequence using one substrate stage (WS1) is detected. After the exposure sequence using the other substrate stage (WS2) is completed, the other substrate stage (WS2) is moved to the exchange position of the sensitive substrate, and one substrate stage (WS1) is moved to the projection optical system (PL). Between the reference (FM1) provided on one substrate stage (WS1) and the mark on the mask using the second alignment system (142). The second positional relationship is measured, and shot areas on the sensitive substrate (W1) held on one substrate stage (WS1) are sequentially exposed, and at the time of the exposure, the first and second positional relationships and the aforementioned Based on the position of one substrate stage (WS1) measured using the second interference measurement major axis, the position of one substrate stage (WS1) in the two-dimensional direction (X-axis direction, Y-axis direction) is controlled. And a projection exposure apparatus that adjusts the surface position of the sensitive substrate (W1) held on one substrate stage (WS1) based on the surface position information detected during the measurement sequence. Is .
According to this, it is possible to perform highly accurate focus and leveling control while improving the throughput.
[0070]
DETAILED DESCRIPTION OF THE INVENTION
<< First Embodiment >>
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.
[0071]
FIG. 1 shows a schematic configuration of a projection exposure apparatus 10 according to the first embodiment. The projection exposure apparatus 10 is a so-called step-and-scan type scanning exposure type projection exposure apparatus.
[0072]
The projection exposure apparatus 10 holds wafers WS1 and WS2 as first and second substrate stages that independently move in a two-dimensional direction while holding wafers W1 and W2 as sensitive substrates on a base board 12, respectively. The stage device provided, the projection optical system PL disposed above the stage device, and the reticle R as a mask above the projection optical system PL mainly in a predetermined scanning direction, here the Y-axis direction (the direction perpendicular to the plane of FIG. 1) ), A lighting system for illuminating the reticle R from above, a control system for controlling these parts, and the like.
[0073]
The stage device is levitated and supported on the base board 12 via an air bearing (not shown), and is independently 2 in the X-axis direction (the left-right direction on the paper surface in FIG. 1) and the Y-axis direction (the orthogonal direction on the paper surface in FIG. 1). Two wafer stages WS1 and WS2 capable of dimension movement, a stage drive system for driving these wafer stages WS1 and WS2, and an interferometer system for measuring the positions of the wafer stages WS1 and WS2 are provided.
[0074]
More specifically, air pads (for example, vacuum preload type air bearings) (not shown) are provided at a plurality of locations on the bottom surfaces of the wafer stages WS1 and WS2, and the air ejection force of the air pads and the vacuum preload are reduced. For example, it is levitated and supported on the base board 12 with an interval of several microns maintained by balance.
[0075]
On the base board 12, as shown in the plan view of FIG. 3, two X-axis linear guides extending in the X-axis direction (for example, a fixed side magnet of a so-called moving coil type linear motor) 122 , 124 are provided in parallel, and two X-axis linear guides 122, 124 are respectively attached with two moving members 114, 118 and 116, 120 that are movable along the X-axis linear guides. ing. Drive coils (not shown) are attached to the bottom portions of these four moving members 114, 118, 116, and 120 so as to surround the X-axis linear guide 122 or 124 from above and from the sides, respectively. And the X-axis linear guide 122 or 124 constitute moving coil type linear motors for driving the moving members 114, 116, 118, and 120 in the X-axis direction, respectively. However, in the following description, for the sake of convenience, the moving members 114, 116, 118, and 120 are referred to as X-axis linear motors.
[0076]
Two of these X-axis linear motors 114 and 116 are respectively provided at both ends of a Y-axis linear guide 110 (such as a fixed coil of a moving magnet type linear motor) 110 extending in the Y-axis direction. The remaining two X-axis linear motors 118 and 120 are fixed to both ends of a similar Y-axis linear guide 112 extending in the Y-axis direction. Therefore, the Y-axis linear guide 110 is driven along the X-axis linear guides 122 and 124 by the X-axis linear motors 114 and 116, and the Y-axis linear guide 112 is driven by the X-axis linear motors 118 and 120. 122 and 124 are driven.
[0077]
On the other hand, a magnet (not shown) surrounding one Y-axis linear guide 110 from above and from the side is provided at the bottom of wafer stage WS1, and wafer stage WS1 is moved to Y-axis by this magnet and Y-axis linear guide 110. A moving magnet type linear motor driven in the direction is configured. Further, a magnet (not shown) surrounding the other Y-axis linear guide 112 from above and from the side is provided at the bottom of the wafer stage WS2, and the wafer stage WS2 is moved to the Y-axis by this magnet and the Y-axis linear guide 112. A moving magnet type linear motor driven in the direction is configured.
[0078]
That is, in the first embodiment, the X-axis linear guides 122 and 124, the X-axis linear motors 114, 116, 118, and 120, the Y-axis linear guides 110 and 112, and the bottom portions of the wafer stages WS1 and WS2 are not illustrated. A stage driving system for driving the wafer stages WS1 and WS2 independently in an XY two-dimensional manner is configured by a magnet or the like. This stage drive system is controlled by the stage controller 38 in FIG.
[0079]
Note that by slightly varying the torque of the pair of X-axis linear motors 114 and 116 provided at both ends of the Y-axis linear guide 110, it is possible to generate or remove slight yawing in the wafer stage WS1. Similarly, by slightly varying the torque of the pair of X-axis linear motors 118 and 120 provided at both ends of the Y-axis linear guide 112, it is possible to generate or remove minute yawing in the wafer stage WS2. .
[0080]
On the wafer stages WS1 and WS2, the wafers W1 and W2 are fixed by vacuum suction or the like via a wafer holder (not shown). The wafer holder is finely driven in a Z-axis direction and a θ-direction (rotation direction about the Z-axis) orthogonal to the XY plane by a Z / θ drive mechanism (not shown). Further, on the upper surfaces of the wafer stages WS1 and WS2, fiducial mark plates FM1 and FM2 on which various fiducial marks are formed are installed so as to have almost the same height as the wafers W1 and W2, respectively. These reference mark plates FM1 and FM2 are used, for example, when detecting the reference position of each wafer stage.
[0081]
Further, a surface 20 on one side in the X-axis direction (left side surface in FIG. 1) and a surface 21 on one side in the Y-axis direction (surface on the back side in FIG. 1) 21 of the wafer stage WS1 are mirror-finished reflecting surfaces. Similarly, a surface 22 on the other side in the X-axis direction (the right side surface in FIG. 1) 22 and a surface 23 on the one side in the Y-axis direction of the wafer stage WS2 are mirror-finished reflecting surfaces. Yes. Interferometer beams of each length measuring axis (BI1X, BI2X, etc.) constituting an interferometer system, which will be described later, are projected onto these reflecting surfaces, and the reflected light is received by each interferometer, whereby a reference for each reflecting surface is obtained. Displacement from the position (generally, a fixed mirror is placed on the side of the projection optical system and the side of the alignment optical system, which is used as a reference plane), and thereby the two-dimensional positions of the wafer stages WS1 and WS2 are measured. It has come to be. The configuration of the measurement axis of the interferometer system will be described in detail later.
[0082]
Here, as the projection optical system PL, there is used a refractive optical system composed of a plurality of lens elements having a common optical axis in the Z-axis direction and having a predetermined reduction magnification, for example, 1/5, on both sides telecentric. Yes. For this reason, the moving speed of the wafer stage in the scanning direction at the time of step-and-scan scanning exposure is 1/5 of the moving speed of the reticle stage.
[0083]
On both sides in the X-axis direction of the projection optical system PL, as shown in FIG. 1, off-axis type alignment systems 24a and 24b having the same function are provided. They are located at the same distance from the center (coincided with the projection center of the reticle pattern image). These alignment systems 24a and 24b have three types of alignment sensors, an LSA (Laser Step Alignment) system, an FIA (Filed Image Alignment) system, and an LIA (Laser Interferometric Alignment) system. It is possible to measure the position of the mark and the alignment mark on the wafer in the X and Y two-dimensional directions.
[0084]
Here, the LSA system is the most versatile sensor that irradiates a mark with a laser beam and measures the mark position using diffracted / scattered light, and has been conventionally used for a wide variety of process wafers. The FIA system is a sensor that measures the mark position by illuminating the mark with broadband light such as a halogen lamp and processing the image of the mark, and is effectively used for asymmetric marks on the aluminum layer and wafer surface. The In addition, the LIA system is a sensor that irradiates a diffraction grating mark with laser light having a slightly different frequency from two directions, causes the generated two diffracted lights to interfere, and detects the position information of the mark from the phase. Yes, it can be used effectively for low step and rough wafers.
[0085]
In the first embodiment, these three types of alignment sensors are properly used according to the purpose, so-called search alignment for measuring the position of the three-dimensional mark on the wafer and measuring the approximate position of the wafer, Fine alignment or the like for performing accurate position measurement of each shot area on the wafer is performed.
[0086]
In this case, the alignment system 24a is used for position measurement of the alignment mark on the wafer W1 held on the wafer stage WS1 and the reference mark formed on the reference mark plate FM1. The alignment system 24b is used for measuring the position of the alignment mark on the wafer W2 held on the wafer stage WS2 and the reference mark formed on the reference mark plate FM2.
[0087]
Information from each alignment sensor constituting the alignment systems 24a and 24b is A / D converted by the alignment control device 80, and a digitized waveform signal is arithmetically processed to detect a mark position. This result is sent to the main control device 90 as a control means, and the main control device 90 instructs the stage control device to correct the synchronization position during exposure according to the result.
[0088]
Further, in the exposure apparatus 10 of the first embodiment, although not shown in FIG. 1, a reticle mark on the reticle R is provided above the reticle R via the projection optical system PL as shown in FIG. There are provided a pair of reticle alignment microscopes 142 and 144 composed of a TTR (Through The Reticle) alignment optical system using an exposure wavelength for simultaneously observing (not shown) and the marks on the reference mark plates FM1 and FM2. . Detection signals from these reticle alignment microscopes 142 and 144 are supplied to the main controller 90. In this case, the deflection mirrors 146 and 148 for guiding the detection light from the reticle R to the reticle alignment microscopes 142 and 144 are movably arranged, and when an exposure sequence is started, a command from the main controller 90 is also given. Thus, the deflecting mirrors 146 and 148 are retracted by the mirror driving device (not shown). Note that a configuration equivalent to the reticle alignment microscope 142, 144 is disclosed in, for example, Japanese Patent Laid-Open No. 7-176468, and therefore detailed description thereof is omitted here.
[0089]
Although not shown in FIG. 1, each of the projection optical system PL and the alignment systems 24a and 24b includes an autofocus / autoleveling measurement mechanism (hereinafter referred to as an in-focus position measuring mechanism) for checking the in-focus position as shown in FIG. , "AF / AL system") 130, 132, 134. Of these, the AF / AL system 132 as the second detection system accurately transfers the pattern on the reticle R onto the wafer (W1 or W2) by scanning exposure, and the pattern forming surface on the reticle R and the wafer. Since the exposure surface of W needs to be conjugate with respect to the projection optical system PL, whether or not the exposure surface of the wafer W matches the image plane of the projection optical system PL within the range of the focal depth (in-focus) In order to detect whether or not In the first embodiment, a so-called multipoint AF system is used as the AF / AL system 132.
[0090]
Here, the detailed configuration of the multipoint AF system constituting the AF / AL system 132 will be described with reference to FIGS.
[0091]
As shown in FIG. 5, the AF / AL system (multi-point AF system) 132 includes an optical fiber bundle 150, a condenser lens 152, a pattern forming plate 154, a lens 156, a mirror 158, and an irradiation objective lens 160. The optical system 151 includes a condensing objective lens 162, a rotational vibration plate 164, an imaging lens 166, and a condensing optical system 161 including a light receiver 168.
[0092]
Here, each part of the configuration of the AF / AL system (multi-point AF system) 132 will be described together with its operation.
[0093]
Illumination light having a wavelength that does not sensitize the photoresist on the wafer W1 (or W2) different from the exposure light EL is guided from an illumination light source (not shown) through the optical fiber bundle 150 and emitted from the optical fiber bundle 150. The light illuminates the pattern forming plate 154 through the condenser lens 152. The illumination light transmitted through the pattern forming plate 154 passes through the lens 156, the mirror 158, and the irradiation objective lens 160, and is projected onto the exposure surface of the wafer W. On the pattern forming plate 154 with respect to the exposure surface of the wafer W1 (or W2). The pattern image is projected and formed obliquely with respect to the optical axis AX. The illumination light reflected by the wafer W 1 is projected onto the light receiving surface of the light receiver 168 via the condenser objective lens 162, the rotation direction vibration plate 164 and the imaging lens 166, and on the light receiving surface of the light receiver 168 on the pattern forming plate 154. The pattern image is re-imaged. Here, the main controller 90 applies predetermined vibrations to the rotational direction vibration plate 164 via the vibration device 172, and a large number of light receivers 168 (specifically, the same number as the slit patterns of the pattern forming plate 154). Detection signals from the light receiving elements are supplied to the signal processing device 170. Further, the signal processing device 170 supplies a large number of focus signals obtained by synchronously detecting each detection signal with the drive signal of the vibration exciting device 172 to the main control device 90 via the stage control device 38.
[0094]
In this case, as shown in FIG. 6, for example, 5 × 9 = 45 vertical slit-like opening patterns 93-11 to 93-59 are formed on the pattern forming plate 154. The image of the aperture pattern is projected obliquely (45 °) with respect to the X axis and the Y axis on the exposure surface of the wafer W. As a result, a slit image having a matrix arrangement inclined at 45 ° with respect to the X axis and the Y axis as shown in FIG. 4 is formed. 4 indicates an illumination field on the wafer conjugate with an illumination area on the reticle illuminated by the illumination system. As is apparent from FIG. 4, the detection beam is irradiated onto an area that is two-dimensionally sufficiently larger than the illumination field IF under the projection optical system PL.
[0095]
The other AF / AL systems 130 and 134 as the first detection system are configured in the same manner as the AF / AL system 132. In other words, in the first embodiment, the detection beam can be irradiated also by the AF / AL mechanisms 130 and 134 used for measuring the alignment mark in substantially the same area as the AF / AL system 132 used for focus detection during exposure. It has become a structure. For this reason, when the alignment sensor 24a and 24b measures the alignment mark, the position of the alignment mark is measured while performing AF / AL measurement similar to that during exposure and autofocus / auto-leveling by control. Alignment measurement becomes possible. In other words, an offset (error) due to the posture of the stage does not occur between exposure and alignment.
[0096]
Next, the reticle driving mechanism will be described with reference to FIGS.
[0097]
The reticle driving mechanism includes a reticle stage RST that can move in a two-dimensional direction of XY while holding the reticle R on the reticle base board 32, a linear motor (not shown) that drives the reticle stage RST, and the reticle stage RST. And a reticle interferometer system for managing the position of the projector.
[0098]
More specifically, in the reticle stage RST, as shown in FIG. 2, two reticles R1 and R2 can be placed in series in the scanning direction (Y-axis direction). The RST is levitated and supported on the reticle base board 32 via an air bearing (not shown), and is driven minutely in the X-axis direction and minute in the θ direction by a drive mechanism 30 (see FIG. 1) including a linear motor (not shown). Rotation and scanning driving in the Y-axis direction are performed. The drive mechanism 30 is a mechanism that uses a linear motor similar to that of the stage device described above as a drive source, but is shown as a simple block in FIG. 1 for convenience of illustration and explanation. For this reason, the reticles R1 and R2 on the reticle stage RST are selectively used, for example, in double exposure, and any reticle can be scanned synchronously with the wafer side.
[0099]
On this reticle stage RST, a parallel plate moving mirror 34 made of the same material as the reticle stage RST (for example, ceramic) is extended in the Y-axis direction at one end of the X-axis direction. A reflective surface is formed on one surface of the mirror 34 in the X-axis direction by mirror finishing. An interferometer beam from an interferometer indicated by a measurement axis BI6X constituting the interferometer system 36 of FIG. 1 is irradiated toward the reflecting surface of the movable mirror 34, and the interferometer receives the reflected light and receives the wafer stage. The position of reticle stage RST is measured by measuring the relative displacement with respect to the reference surface in the same manner as on the side. Here, the interferometer having the measurement axis BI6X actually has two interferometer optical axes that can be measured independently, and measures the position of the reticle stage in the X-axis direction and measures the amount of yawing. Is possible. The interferometer having the measurement axis BI6X is based on the reticle and wafer based on yawing information and X position information of the wafer stages WS1 and WS2 from the interferometers 16 and 18 having measurement axes BI1X and BI2X on the wafer stage described later. This is used to control the rotation of reticle stage RST in the direction to cancel the relative rotation (rotation error) of the lens and to perform X-direction synchronization control.
[0100]
On the other hand, a pair of corner cube mirrors 35 and 37 are installed on the other side in the Y-axis direction (the front side in FIG. 1), which is the scanning direction (scanning direction) of reticle stage RST. A pair of double-pass interferometers (not shown) irradiate the corner cube mirrors 35 and 37 with interferometer beams indicated by measurement axes BI7Y and BI8Y in FIG. Are returned from the corner cube mirrors 35 and 37, and the reflected lights reflected there return on the same optical path and are received by the respective double-pass interferometers. The reference positions of the respective corner cube mirrors 35 and 37 (the reticle at the reference position). The relative displacement from the reflection surface on the base board 32 is measured. Then, the measurement values of these double pass interferometers are supplied to the stage control device 38 of FIG. 1, and the position of the reticle stage RST in the Y-axis direction is measured based on the average value. Information on the position in the Y-axis direction is obtained by calculating the relative position between the reticle stage RST and the wafer stage WS1 or WS2 based on the measurement value of the interferometer having the measurement axis BI3Y on the wafer side, and scanning during scanning exposure based on this. This is used for synchronous control of the reticle in the direction (Y-axis direction) and the wafer.
[0101]
That is, in the first embodiment, the reticle interferometer system is configured by the interferometer 36 and a pair of double-path interferometers indicated by the measurement axes BI7Y and BI8Y.
[0102]
Next, an interferometer system for managing the positions of wafer stages WST1 and WST2 will be described with reference to FIGS.
[0103]
As shown in these figures, the X axis direction one side of the wafer stage WS1 is along a first axis (X axis) passing through the projection center of the projection optical system PL and the detection centers of the alignment systems 24a and 24b. The surface is irradiated with an interferometer beam indicated by a first measurement axis BI1X from the interferometer 16 of FIG. 1, and similarly, on the other surface in the X-axis direction of the wafer stage WS2 along the first axis. Is irradiated with an interferometer beam indicated by a second measuring axis BI2X from the interferometer 18 of FIG. The interferometers 16 and 18 receive these reflected lights, thereby measuring the relative displacement of each reflecting surface from the reference position and measuring the positions of the wafer stages WS1 and WS2 in the X-axis direction. . Here, as shown in FIG. 2, the interferometers 16 and 18 are three-axis interferometers each having three optical axes. In addition to the measurement in the X-axis direction of the wafer stages WS1 and WS2, tilt measurement and θ measurement is possible. The output value of each optical axis can be measured independently. Here, the θ stage (not shown) that rotates the θ of the wafer stages WS1 and WS2 and the Z leveling stages RS1 and RS2 as a substrate driving system that performs minute driving and tilt driving in the Z-axis direction are actually reflecting surfaces. Therefore, all of the driving amount at the time of tilt control of the wafer stage can be monitored by these interferometers 16 and 18 (substrate driving system).
[0104]
The interferometer beams of the first measurement axis BI1X and the second measurement axis BI2X always come into contact with the wafer stages WS1 and WS2 over the entire range of movement of the wafer stages WS1 and WS2, and accordingly, the X axis Regarding the direction, the position of the wafer stages WS1 and WS2 is the first length measurement axis BI1X and the second length measurement axis BI2X during exposure using the projection optical system PL and when the alignment systems 24a and 24b are used. It is managed based on the measured value.
[0105]
As shown in FIGS. 2 and 3, an interferometer having a third measurement axis BI3Y perpendicularly intersecting the first axis (X axis) at the projection center of the projection optical system PL, and alignment systems 24a and 24b. Interferometers each having measurement axes BI4Y and BI5Y as fourth measurement axes perpendicularly intersecting with the first axis (X axis) at the respective detection centers are provided. Only the long axis is shown).
[0106]
In the case of the first embodiment, the Y-direction position measurement of the wafer stages WS1 and WS2 at the time of exposure using the projection optical system PL is used to measure the projection axis of the projection optical system, that is, the length measuring axis BI3Y passing through the optical axis AX. The measurement value of the interferometer is used, and the measurement value of the measurement axis BI4Y passing through the detection center of the alignment system 24a, that is, the optical axis SX, is used to measure the position of the wafer stage WS1 in the Y direction when the alignment system 24a is used. The measurement value of the measurement axis BI5Y passing through the detection center of the alignment system 24b, that is, the optical axis SX, is used for measuring the position in the Y direction of the wafer stage WS2 when the alignment system 24b is used.
[0107]
Accordingly, although the interference measurement major axis in the Y-axis direction deviates from the reflection surface of the wafer stages WS1 and WS2 depending on each use condition, at least one measurement axis, that is, the measurement axes BI1X and BI2X are the respective wafer stages. Since it does not deviate from the reflection surfaces of WS1 and WS2, the Y-side interferometer can be reset at an appropriate position where the interferometer optical axis to be used enters the reflection surface. A method for resetting the interferometer will be described in detail later.
[0108]
The Y measuring length measuring axes BI3Y, BI4Y, and BI5Y are two-axis interferometers each having two optical axes. In addition to the measurement in the Y-axis direction of the wafer stages WS1 and WS2, Tilt measurement is possible. The output value of each optical axis can be measured independently.
In the first embodiment, interferometers that manage the two-dimensional coordinate positions of wafer stages WS1 and WS2 by a total of five interferometers including three interferometers having interferometers 16 and 18 and measurement axes BI3Y, BI4Y, and BI5Y. A metering system is configured.
[0109]
In the first embodiment, as will be described later, while one of the wafer stages WS1 and WS2 executes the exposure sequence, the other executes the wafer exchange and wafer alignment sequence. The movement of the wafer stages WS1 and WS2 is managed by the stage controller 38 in accordance with a command from the main controller 90 based on the output value of each interferometer so that there is no interference between both stages.
[0110]
Next, the illumination system will be described with reference to FIG. As shown in FIG. 1, the illumination system includes an exposure light source 40, a shutter 42, a mirror 44, beam expanders 46 and 48, a first fly-eye lens 50, a lens 52, a vibrating mirror 54, a lens 56, and a second fly. The lens includes an eye lens 58, a lens 60, a fixed blind 62, a movable blind 64, relay lenses 66 and 68, and the like.
[0111]
Here, each part of the illumination system will be described together with its operation.
[0112]
Laser light emitted from a light source unit 40 including a KrF excimer laser that is a light source and a dimming system (a dimming plate, an aperture stop, etc.) is transmitted through a shutter 42 and then deflected by a mirror 44 to be a beam expander 46, The beam is shaped into an appropriate beam diameter by 48 and is incident on the first fly-eye lens 50. The light beam incident on the first fly-eye lens 50 is divided into a plurality of light beams by two-dimensionally arranged fly-eye lens elements, and each light beam is again different by the lens 52, the vibrating mirror 54, and the lens 56. The light enters the second fly-eye lens 58 from an angle. The light beam emitted from the second fly-eye lens 58 reaches the fixed blind 62 installed at a position conjugate with the reticle R by the lens 60. After the cross-sectional shape is defined in a predetermined shape, the reticle R A predetermined shape defined by the fixed blind 62 on the reticle R as uniform illumination light that passes through the movable blind 64 disposed at a position slightly defocused from the conjugate plane of Here, the illumination area IA having a rectangular slit shape (see FIG. 2) is illuminated.
[0113]
Next, the control system will be described with reference to FIG. This control system is composed of an exposure amount control device 70, a stage control device 38, and the like, which are subordinate to the main control device 90, with a main control device 90 that controls the entire apparatus as a whole.
[0114]
Here, the operation at the time of exposure of the projection exposure apparatus 10 according to the first embodiment will be described focusing on the operation of each component of the control system.
[0115]
The exposure amount controller 70 instructs the shutter driver 72 to drive the shutter driver 74 to open the shutter 42 before the synchronous scanning of the reticle R and the wafer (W1 or W2) is started. .
[0116]
Thereafter, the stage controller 38 starts synchronous scanning (scan control) of the reticle R and the wafer (W1 or W2), that is, the reticle stage RST and the wafer stage (WS1 or WS2) in accordance with an instruction from the main controller 90. The This synchronous scanning is performed by monitoring the measurement values of the measurement axis BI3Y and the measurement axis BI1X or BI2X of the interferometer system and the measurement axes BI7Y, BI8Y and the measurement axis BI6X of the reticle interferometer system, while controlling the stage control device. This is performed by controlling each of the linear motors constituting the driving system of the reticle driving unit 30 and the wafer stage by 38.
[0117]
When both stages are controlled at a constant speed within a predetermined tolerance, the exposure control device 70 instructs the laser control device 76 to start pulse emission. As a result, the rectangular illumination area IA of the reticle R whose pattern is chromium-deposited on the lower surface thereof is illuminated by illumination light from the illumination system, and an image of the pattern in the illumination area is 1/5 by the projection optical system PL. Projection exposure is performed on a wafer (W1 or W2) whose surface is reduced in size and coated with a photoresist on its surface. As is clear from FIG. 2, the slit width in the scanning direction of the illumination area IA is narrower than the pattern area on the reticle, and the reticle R and the wafer (W1 or W2) are synchronously scanned as described above. Thus, an image of the entire surface of the pattern is sequentially formed on the shot area on the wafer.
[0118]
Here, simultaneously with the start of the pulse emission described above, the exposure amount control device 70 instructs the mirror drive device 78 to drive the vibrating mirror 54 so that the pattern region on the reticle R is completely the illumination region IA (see FIG. 2). ), That is, until the image of the entire surface of the pattern is formed on the shot area on the wafer, this control is continuously performed to reduce the unevenness of interference fringes generated by the two fly-eye lenses 50 and 58. Do.
[0119]
Further, in order to prevent illumination light from leaking outside the light-shielding area on the reticle at the shot edge portion during the scanning exposure described above, the movable blind 64 is moved by the blind controller 39 in synchronization with the scanning of the reticle R and the wafer W. The drive control is performed, and a series of these synchronous operations are managed by the stage controller 38.
[0120]
By the way, the pulse light emission by the laser control device 76 described above needs to emit light n times (n is a positive integer) while an arbitrary point on the wafers W1 and W2 passes through the illumination field width (w). When the oscillation frequency is f and the wafer scan speed is V, the following equation (1) needs to be satisfied.
[0121]
f / n = V / w (1)
Further, when the irradiation energy of one pulse irradiated on the wafer is P and the resist sensitivity is E, the following equation (2) needs to be satisfied.
[0122]
nP = E (2)
In this way, the exposure amount control device 70 calculates all the variable amounts of the irradiation energy P and the oscillation frequency f, issues a command to the laser control device 76, and sets the dimming system provided in the exposure light source 40. By controlling the irradiation energy P and the oscillation frequency f, the shutter driving device 72 and the mirror driving device 78 are controlled.
[0123]
Further, in the main controller 90, for example, when correcting the movement start position (synchronous position) of the reticle stage and the wafer stage that perform synchronous scanning during scan exposure, the correction amount with respect to the stage controller 38 that controls the movement of each stage. Instructs the correction of the stage position according to.
[0124]
Furthermore, in the projection exposure apparatus of the first embodiment, a first transfer system that exchanges wafers with the wafer stage WS1, and a second transfer system that exchanges wafers with the wafer stage WS2; Is provided.
[0125]
As shown in FIG. 7, the first transfer system performs wafer exchange with the wafer stage WS1 at the left wafer loading position as will be described later. The first transport system is attached to a first loading guide 182 extending in the Y-axis direction, a first slider 186 and a second slider 190 moving along the loading guide 182, and the first slider 186. A first wafer loader including a first unload arm 184, a first load arm 188 attached to a second slider 190, and the like, and three vertical moving members provided on the wafer stage WS1 And a first center-up 180 composed of
[0126]
Here, the wafer exchange operation by the first transfer system will be briefly described.
[0127]
Here, as shown in FIG. 7, a case will be described in which the wafer W1 ′ on the wafer stage WS1 at the left wafer loading position and the wafer W1 transferred by the first wafer loader are exchanged.
[0128]
First, in main controller 90, the vacuum of a wafer holder (not shown) on wafer stage WS1 is turned off via a switch (not shown) to release the adsorption of wafer W1 ′.
[0129]
Next, main controller 90 drives center-up 180 upward by a predetermined amount via a center-up drive system (not shown). Thereby, the wafer W1 ′ is lifted to a predetermined position. In this state, main controller 90 supports the movement of first unload arm 184 by a wafer loader controller (not shown). Thereby, the first slider 186 is driven and controlled by the wafer loader control device, and the first unload arm 184 moves along the loading guide 182 over the wafer stage WS1 and is positioned directly below the wafer W1 ′.
[0130]
In this state, main controller 90 drives center up 180 downward to a predetermined position. During the downward movement of the center up 180, the wafer W1 ′ is transferred to the first unload arm 184, so the main controller 90 instructs the wafer loader controller to start vacuuming the first unload arm 184. As a result, the wafer W1 ′ is sucked and held by the first unload arm 184.
[0131]
Next, main controller 90 instructs the wafer loader controller to retract the first unload arm 184 and start moving the first load arm 188. As a result, the first unload arm 184 starts to move in the −Y direction in FIG. 7 integrally with the first slider 186, and at the same time, the second slider 190 and the first load arm 188 holding the wafer W1. The movement starts in the + Y direction integrally. When the first load arm 188 comes above the wafer stage WS1, the wafer loader control device stops the second slider 190 and releases the vacuum of the first load arm 188.
[0132]
In this state, the main controller 90 drives the center-up 180 upward, and the center-up 180 lifts the wafer W1 from below. Next, main controller 90 instructs wafer loader controller to retract the load arm. Thus, the second slider 190 starts moving in the −Y direction integrally with the first load arm 188, and the first load arm 188 is retracted. Simultaneously with the start of retraction of the first load arm 188, the main controller 90 starts to drive the center up 180 downward to place the wafer W1 on a wafer holder (not shown) on the wafer stage WS1, and vacuum the wafer holder. turn on. This completes a series of wafer exchange sequences.
[0133]
Similarly, as shown in FIG. 8, the second transfer system performs wafer exchange with the wafer stage WS2 at the right wafer loading position in the same manner as described above. The second transport system includes a second loading guide 192 extending in the Y-axis direction, a third slider 196 moving along the second loading guide 192, a fourth slider 200, and a third slider 196. A second wafer loader configured to include a second unload arm 194 attached, a second load arm 198 attached to the fourth slider 200, and the like, and a not-shown unit provided on the wafer stage WS2 It consists of the second center up.
[0134]
Next, parallel processing by two wafer stages, which is a feature of the first embodiment, will be described with reference to FIGS.
[0135]
In FIG. 7, while the wafer W2 on the wafer stage WS2 is being exposed through the projection optical system PL, the wafer stage WS1 and the first transfer system are in the left loading position as described above. A plan view showing a state in which the wafers are exchanged between them is shown. In this case, an alignment operation is performed on the wafer stage WS1 as described later following the wafer exchange. In FIG. 7, the position control of the wafer stage WS2 during the exposure operation is performed based on the measured values of the measurement axes BI2X and BI3Y of the interferometer system, and the position of the wafer stage WS1 where the wafer replacement and alignment operations are performed. The control is performed based on the measurement values of the measurement axes BI1X and BI4Y of the interferometer system.
[0136]
At the left loading position shown in FIG. 7, the arrangement is such that the reference mark on the reference mark plate FM1 of the wafer stage WS1 comes directly under the alignment system 24a. For this reason, the main controller 90 resets the interferometer of the measurement axis BI4Y of the interferometer system before measuring the reference mark on the reference mark plate FM1 by the alignment system 24a.
[0137]
Subsequent to the wafer exchange and the interferometer reset described above, search alignment is performed. The search alignment performed after the wafer exchange is a pre-alignment performed again on the wafer stage WS1 because the position error is large only by the pre-alignment performed during the transfer of the wafer W1. Specifically, the positions of three search alignment marks (not shown) formed on the wafer W1 placed on the stage WS1 are measured using an LSA sensor or the like of the alignment system 24a, and the measurement is performed. Based on the result, the wafer W1 is aligned in the X, Y, and θ directions. The operation of each part during this search alignment is controlled by main controller 90.
[0138]
After this search alignment is completed, fine alignment is performed in which the arrangement of each shot area on the wafer W1 is obtained here using EGA. Specifically, the wafer stage WS1 is sequentially controlled based on design shot arrangement data (alignment mark position data) while managing the position of the wafer stage WS1 by the interferometer system (measurement axes BI1X, BI4Y). While moving, the alignment mark position of a predetermined sample shot on the wafer W1 is measured by an FIA sensor or the like of the alignment system 24a, and based on this measurement result and the design coordinate data of the shot arrangement, statistical calculation by the least square method is performed. , All shot array data are calculated. The operation of each part in the EGA is controlled by the main controller 90, and the above calculation is performed by the main controller 90. This calculation result is preferably converted into a coordinate system based on the reference mark position of the reference mark plate FM1.
[0139]
In the case of the first embodiment, as described above, during the measurement by the alignment system 24a, the same AF / AL system 132 (see FIG. 4) as that at the time of exposure is used while performing the autofocus / auto leveling by the control and the alignment. The mark position is measured, and an offset (error) due to the posture of the stage can be prevented from occurring between alignment and exposure.
[0140]
While the wafer exchange and alignment operations are being performed on the wafer stage WS1 side, the wafer stage WS2 side continuously uses the two reticles R1 and R2 as shown in FIG. 9 while changing the exposure conditions. Then, double exposure is performed by the step-and-scan method.
[0141]
Specifically, fine alignment by EGA is performed in advance in the same manner as on the wafer W1 side described above, and the shot arrangement data on the wafer W2 obtained as a result (the reference mark on the reference mark plate FM2 is used as a reference). ), The shot area on the wafer W2 is sequentially moved below the optical axis of the projection optical system PL, and then the reticle stage RST and the wafer stage WS2 are synchronized in the scanning direction each time each shot area is exposed. Scan exposure is performed by scanning. Such exposure for all the shot areas on the wafer W2 is continuously performed even after reticle replacement. As a specific exposure sequence of double exposure, as shown in FIG. 10A, each shot area of the wafer W1 is sequentially scanned and exposed from A1 to A12 using a reticle R2 (A pattern). The reticle stage RST is moved by a predetermined amount in the scanning direction using the drive system 30 to set the reticle R1 (B pattern) to the exposure position, and then scan exposure is performed in the order of BI1X to BI1X2 shown in FIG. Do. At this time, since the exposure conditions (AF / AL, exposure amount) and transmittance are different between the reticle R2 and the reticle R1, it is necessary to measure the respective conditions during reticle alignment and change the conditions according to the results.
[0142]
The operation of each part during double exposure of the wafer W2 is also controlled by the main controller 90.
[0143]
In the exposure sequence and wafer exchange / alignment sequence that are performed in parallel on the two wafer stages WS1 and WS2 shown in FIG. 7 described above, the wafer stage that has been completed first enters a waiting state, and both operations are completed. At the time, the wafer stages WS1 and WS2 are controlled to move to the positions shown in FIG. The wafer W2 on the wafer stage WS2 for which the exposure sequence has been completed is replaced at the right loading position, and the wafer W1 on the wafer stage WS1 for which the alignment sequence has been completed is subjected to the exposure sequence under the projection optical system PL. Is called.
[0144]
In the right loading position shown in FIG. 8, the reference mark on the reference mark plate FM2 is arranged below the alignment system 24b as in the left loading position, and the wafer exchange operation and the alignment sequence described above are executed. Will be done. Of course, the reset operation of the interferometer of the measuring axis BI5Y of the interferometer system is executed prior to the mark detection on the reference mark plate FM2 by the alignment system 24b.
[0145]
Next, the reset operation of the interferometer by the main controller 90 when shifting from the state of FIG. 7 to the state of FIG. 8 will be described.
[0146]
After alignment at the left loading position, wafer stage WS1 is moved to a position where the reference mark on reference plate FM1 comes directly under the optical axis AX center (projection center) of projection optical system PL shown in FIG. However, since the interferometer beam of the measuring axis BI4Y is not incident on the reflecting surface 21 of the wafer stage WS1 during this movement, it is difficult to move the wafer stage to the position shown in FIG. 8 immediately after the alignment is completed. For this reason, in the first embodiment, the following measures are taken.
[0147]
That is, as described above, in the first embodiment, when the wafer stage WS1 is in the left loading position, the reference mark plate FM1 is set to be directly below the alignment system 24a. Since the interferometer of the measuring axis BI4Y is reset, the wafer stage WS1 is temporarily returned to this position, and the detection center of the alignment system 24a and the optical axis center (projection center) of the projection optical system PL, which are known in advance from that position. ) To the right in the X-axis direction by the distance BL while monitoring the measurement value of the interferometer 16 of the length measuring axis BI1X where the interferometer beam does not break. Move. As a result, wafer stage WS1 is moved to the position shown in FIG. Then, main controller 90 uses at least one of reticle alignment microscopes 142 and 144 to measure the relative positional relationship between the mark on reference mark plate FM1 and the reticle mark, and then an interferometer for measuring axis BI3Y. To reset. The reset operation can be executed when the next measurement axis to be used can irradiate the side surface of the wafer stage.
[0148]
As described above, the reason why high-precision alignment is possible even if the reset operation of the interferometer is performed is that the alignment mark on the reference mark plate FM1 is measured by the alignment system 24a, and then the alignment mark of each shot area on the wafer W1 is set. This is because the distance between the reference mark and the virtual position calculated by measuring the wafer mark is calculated by the same sensor. Since the relative distance between the reference mark and the position to be exposed is obtained at this point, if the correspondence between the exposure position and the reference mark position is obtained by the reticle alignment microscope 142 or 144 before the exposure, the value is added to the value. By adding the relative distance, even if the interferometer beam of the interferometer in the Y-axis direction is cut during the movement of the wafer stage and reset again, a highly accurate exposure operation can be performed.
[0149]
If the length measurement axis BI4Y cannot be cut while the wafer stage WS1 is moved from the alignment end position to the position shown in FIG. 8, the measurement values of the length measurement axes BI1X and BI4Y are monitored and after the alignment is completed. Of course, the wafer stage may be moved linearly to the position shown in FIG. In this case, the reset operation of the interferometer may be performed when the length measuring axis BI3Y passing through the optical axis AX of the projection optical system PL is applied to the reflecting surface 21 orthogonal to the Y axis of the wafer stage WS1.
[0150]
In the same manner as described above, the wafer stage WS2 may be moved from the exposure end position to the right loading position shown in FIG. 8 to perform the reset operation of the interferometer of the measurement axis BI5Y.
[0151]
FIG. 11 shows an example of the timing of an exposure sequence for sequentially exposing each shot area on the wafer W1 held on the wafer stage WS1, and FIG. 12 is performed in parallel with this. The timing of the alignment sequence on the wafer W2 held on the wafer stage WS2 is shown. In the first embodiment, while the two wafer stages WS1 and WS2 are independently moved in a two-dimensional direction, an exposure sequence and a wafer exchange / alignment sequence are performed in parallel for the wafers W1 and W2 on each wafer stage. By doing so, throughput is improved.
[0152]
However, when two operations are simultaneously performed using two wafer stages, the operation performed on one wafer stage may affect the operation performed on the other wafer stage as a disturbance factor. Conversely, there is an operation in which an operation performed on one wafer stage does not affect an operation performed on the other wafer stage. Therefore, in the first embodiment, among the operations that are processed in parallel, the operations that become disturbance factors are divided into the operations that do not become disturbance factors, or the operations that do not cause disturbance factors are performed simultaneously. The timing of each operation is adjusted.
[0153]
For example, during the scanning exposure, the wafer W1 and the reticle R are synchronously scanned at a constant speed, so that it does not become a disturbance factor, and it is necessary to eliminate other disturbance factors as much as possible. For this reason, during the scan exposure on one wafer stage WS1, the timing is adjusted so as to be stationary in the alignment sequence performed on the wafer W2 on the other wafer stage WS2. That is, the mark measurement in the alignment sequence is performed in a state where the wafer stage WS2 is stationary at the mark position, so that it is not a disturbance factor for the scan exposure, and the mark measurement can be performed in parallel during the scan exposure. 11 and 12, the scan exposure indicated by the operation numbers “1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23” with respect to the wafer W1 in FIG. 12, the mark measurement operations at the respective alignment mark positions indicated by the operation numbers “1, 3, 5, 7, 9, 11, 13, 15, 17, 19, 21, 23” in FIG. You can see that it is done synchronously. On the other hand, even in the alignment sequence, during scanning exposure, since the motion is constant, it is possible to perform high-precision measurement without causing disturbance.
[0154]
The same thing can be considered at the time of wafer exchange. In particular, vibration generated when the wafer is transferred from the load arm to the center up can be a cause of disturbance. Therefore, acceleration / deceleration before scan exposure or before and after synchronous scanning is performed at a constant speed (disturbance factor) The wafer may be delivered according to the above.
[0155]
The timing adjustment described above is performed by the main controller 90.
[0156]
Next, in the projection exposure apparatus 10 of the first embodiment, AF measurement of the wafer is performed during alignment using the AF / AL system 130 provided in the alignment system 24a or the AF / AL system 134 provided in the alignment system 24b. A method of performing focus / leveling control during exposure based on the measurement result and the AF measurement result of the wafer by the AF / AL system 132 provided in the projection optical system PL will be described.
[0157]
As described above, the exposure order for each shot area on the wafer W is as follows: (1) Acceleration / deceleration time during scanning, (2) Settling time, (3) Exposure time, (4) Stepping time for adjacent shots, etc. Although it is determined by the parameters 1 ▼ to 4), in general, since acceleration / deceleration of the reticle stage is a rate-determining condition, when 2-shot stepping is not performed by vertical stepping (stepping in the Y direction in FIG. 13) It is most efficient to scan the wafer alternately in the ± Y directions (sequential scanning exposure is performed for shots adjacent in the X direction in FIG. 13).
[0158]
FIG. 13 shows the exposure order of the shot area 210 on the wafer W1 determined in this way. FIG. 13 shows an example in which all shot arrangements are contained in the wafer W1.
[0159]
Also in the present embodiment, complete read-ahead control as described in Japanese Patent Laid-Open No. Hei 6-283403 is performed prior to exposure of each shot area, but the most efficient as shown in FIG. If exposure is to be performed in the exposure order, the pre-reading AF detection point is placed on the outer periphery of the wafer W1 at each position indicated by symbols A, B, and C in FIG. AF detection points that cannot be measured (detected) are generated. In such a case, the above complete look-ahead control cannot be performed.
[0160]
This will be described in further detail. FIGS. 14A, 14B, and 14C are enlarged plan views in the case of performing pre-reading AF measurement at each position indicated by A, B, and C in FIG. Actually, the exposure area IF conjugate to the illumination area IA on the reticle, the AF detection points AF1 to AF5, and the like are fixed, and the wafer W1 is scanned with respect to them. For convenience, FIG. , (B) and (C), the exposure area IF and the AF detection point are shown to be scanned with respect to the wafer surface. Therefore, in the following description, the direction opposite to the actual scanning direction of the wafer W1 will be described as the scanning direction.
[0161]
In this case, AF detection points AF1 to AF5 as the second detection system are arranged in the non-scanning direction (left and right direction of the paper surface) on one side of the exposure area IF in the scanning direction (up and down direction of the paper surface) (FIG. 14 ( In addition, AF detection points AB1 to AB5 as the second detection system are arranged in the non-scanning direction on the other side in the scanning direction of the exposure area IF (see FIG. 14B). ).
[0162]
When AF measurement is performed while scanning in the + Y direction in FIG. 14A, the detection points AF1 and AF2 are off the wafer W1 surface, and also in the cases of FIGS. 14B and 14C, the wafer W1 surface. Since the detection points (AB1 to AB5, AF4 and AF5) are off, the above-described prefetch control cannot be performed.
[0163]
In such a case, conventionally, in order to prevent the detection points from deviating from the surface of the wafer W1 at the positions A, B, and C, scanning is performed from the inside to the outside of the wafer W1 (referred to as inner scanning). The scanning direction is reversed as described above. However, if the scanning direction is reversed, the exposure order determined as described above is changed, resulting in a decrease in throughput.
[0164]
In order to prevent such a decrease in throughput, as shown in FIG. 15 (comparative example), when the AF detection points for prefetching (for example, AF1 to AF5) exist on all wafer surfaces and measurement is possible. When the AF measurement is started at D and auto focus and auto leveling control (hereinafter referred to as AF / AL control) is adopted, an error due to AF / AL tracking phase delay is between the tracking end points E to F. Occurs. Note that the point E in FIG. 15 indicates the follow-up completion position when normal look-ahead control is performed. As is clear from this, the AF / AL control accuracy deteriorates in such AF measurement. I understand.
[0165]
Therefore, in the first embodiment, prior to the pre-reading control at the time of wafer exposure, the alignment is performed using the AF / AL system 130 provided in the alignment system 24a or the AF / AL system 134 provided in the alignment system 24b. Sometimes, the AF measurement of the wafer W1 is performed under the same conditions as in the exposure, thereby preventing the deterioration of the AF / AL control accuracy, which is an error due to the phase delay of the AF / AL tracking. The AF / AL system 130 or the AF / AL system 134 is a first detection system capable of performing AF / AL measurement on the surface of the wafer W1 under the same conditions as those provided in the projection optical system PL described above. AF detection points (corresponding to AF1 to AF5: see FIG. 14A) and AF detection points (corresponding to AB1 to AB5: see FIG. 14B).
[0166]
That is, as shown in FIG. 16, on the wafer W1 to be aligned, the number of EGA measurement points is AL1 to AL6 (6 points), during which AF measurement is performed at the measurement points C and A in the same direction as the exposure sequence. , B. Also in this case, in order to prevent the operations of the two substrate stages from affecting each other, the stepping operations (disturbance factor operations) or the exposure operation and the alignment operation (non-disturbance factor operations) are synchronized with each other. The stages are moved in an order that does not interfere with each other. In this case, it is assumed that exposure time> alignment time + prefetch measurement time.
[0167]
FIG. 17 shows measurement results from detection points AF1 to AF5 by AF measurement at the time of alignment, which is a feature of the present invention at point A in FIG. In FIG. 17, in order to simplify the drawing, the level of the wafer surface is shown as 0. Usually, however, the results of AF1 to AF5 generally vary.
[0168]
In this case, as shown in FIG. 14A, since the AF measurement can be normally performed at the detection points AF4 and AF5, the AF measurement value also indicates the wafer surface position in FIG. On the other hand, the detection points AF3, AF2 and AF1 sequentially indicate the wafer surface position as they move in the scanning direction. In this way, if focus measurement of the shot area near the wafer outer periphery is performed in advance, in the next exposure sequence, for example, what measurement values are shown at positions A, B, and C in FIG. As can be seen, during pre-reading control during actual exposure, as shown in FIG. 18, compared to the case of FIG. 15, the wafer position is set to the target position (0 within the range of measurement reproducibility error of the wafer surface position). ). That is, the focus can be quickly driven.
[0169]
Originally, the tracking control response of autofocus is a condition that can follow 30% of the absolute error as a primary response, as shown in Japanese Patent Laid-Open No. 6-283403, and by reducing the initial absolute value error, The follow-up end point F becomes faster (because the allowable values are the same), and the follow-up can be finished even before the follow-up completion point E when the normal look-ahead control is performed.
[0170]
As described above, according to the projection exposure apparatus 10 of the first embodiment, the two wafer stages holding the wafer are moved independently, the wafer exchange and alignment operations are performed on one stage, and the other is performed. The exposure operation is performed in parallel on the stage, and at the time of the above alignment, the AF measurement of the wafer surface is performed using the AF / AL system of the alignment system. Since the focus measurement is performed in advance on the wafer periphery and the result is used, scanning from the outside to the inside of the wafer is performed in the vicinity of the wafer periphery where there is no wafer surface at the read-ahead position during exposure. Even in the shot area to be exposed, it is possible to quickly pursue the focus, and to prevent a delay in the follow-up of the prefetch control. Therefore, it is possible to control focus and leveling with high accuracy, and even when scanning exposure is performed from the outside to the inside of the wafer in the vicinity of the outer periphery of the wafer, it is not necessary to adopt the inner scan, and the most efficient. Since each shot area can be exposed in a good exposure order, throughput can be improved.
[0171]
Further, since the AF measurement at the time of alignment is performed while scanning from the same direction as the scanning exposure of the outer peripheral shot, it is possible to perform focus control that removes an offset or the like depending on the running direction of the stage.
[0172]
In addition, according to the projection exposure apparatus 10 of the first embodiment, two wafer stages for holding two wafers independently are provided, and these two wafer stages are moved independently in the XYZ directions, While performing wafer exchange and alignment operations on one wafer stage, the exposure operation is performed on the other wafer stage, and when both operations are completed, each other's operations are switched, greatly increasing throughput. It becomes possible to improve.
[0173]
In addition, according to the first embodiment, since at least two alignment systems that perform mark detection with the projection optical system PL interposed therebetween are provided, the alignment systems are alternately arranged by shifting the two wafer stages alternately. Thus, it is possible to perform the alignment operation and the exposure operation performed in parallel in parallel processing.
[0174]
In addition, according to the first embodiment, since the wafer loader for exchanging the wafer is arranged in the vicinity of the alignment system, particularly at each alignment position, the transition from the wafer exchange to the alignment sequence can be performed smoothly. Higher throughput can be obtained.
[0175]
Further, according to the first embodiment, since the high throughput as described above can be obtained, even if the off-axis alignment system is installed far away from the projection optical system PL, the influence of the degradation of the throughput is almost eliminated. For this reason, high N.I. A. It is possible to design and install a straight cylinder type optical system having a numerical aperture and a small aberration.
[0176]
In addition, according to the first embodiment, each optical system has an interferometer beam from an interferometer that measures approximately the center of each optical axis of the two alignment systems and the projection optical system PL. In both cases of alignment and pattern exposure via the projection optical system, the two wafer stage positions can be accurately measured without Abbe error, and the two wafer stages can be moved independently. It becomes possible to make it.
[0177]
Furthermore, the measurement axes BI1X and BI2X provided from both sides along the direction in which the two wafer stages WS1 and WS2 are arranged (here, the X-axis direction) toward the projection center of the projection optical system PL are always the wafer stages WS1 and WS1. Since irradiation is performed on WS2 and the position of each wafer stage in the X-axis direction is measured, movement control can be performed so that the two wafer stages do not interfere with each other.
[0178]
In addition, the length measurement axes BI3Y, BI4Y, and the length measurement axes BI3Y, BI4Y in the direction perpendicular to the detection center of the alignment system and the projection center position of the projection optical system PL (here, the Y axis direction) with respect to the length measurement axes BI1X, BI2X, Even if the interferometer is arranged so as to irradiate BI5Y and the wafer stage is moved and the measurement axis deviates from the reflecting surface, the position of the wafer stage can be accurately controlled by resetting the interferometer. Become.
[0179]
Reference mark plates FM1 and FM2 are provided on the two wafer stages WS1 and WS2, respectively. The mark position on the reference mark plate and the mark position on the wafer are obtained by measuring in advance with an alignment system. By adding the distance from the correction coordinate system to the reference plate measurement position before exposure, the wafer position can be measured without performing baseline measurement to measure the distance between the projection optical system and the alignment system. As a result, the mounting of a large reference mark plate as described in JP-A-7-176468 becomes unnecessary.
[0180]
Further, according to the first embodiment, since double exposure is performed using a plurality of reticles R, an effect of improving high resolution and DOF (depth of focus) can be obtained. However, in this double exposure method, since the exposure process must be repeated at least twice, the exposure time becomes long and the throughput is greatly reduced. By using the projection exposure apparatus of the first embodiment, Since the throughput can be significantly improved, high resolution and an improvement effect of DOF can be obtained without reducing the throughput. For example, in T1 (wafer exchange time), T2 (search alignment time), T3 (fine alignment time), and T4 (one exposure time), each processing time for an 8-inch wafer is T1: 9 seconds, T2: 9 seconds , T3: 12 seconds, T4: 28 seconds, throughput is THOR = 3600 / (T1 + T2 + T3 + T4 * 2) when double exposure is performed by a conventional technique in which a series of exposure processes are performed using one wafer stage. = 3600 / (30 + 28 * 2) = 41 [sheets / hour] The throughput of a conventional apparatus that performs a single exposure method using one wafer stage (THOR = 3600 / (T1 + T2 + T3 + T4) = 3600/58 = 62 [sheets] / Hour]), the throughput is reduced to 66%. However, when performing double exposure using the projection exposure apparatus of the first embodiment while T1, T2, T3, and T4 are processed in parallel, the exposure time is longer, so that the throughput THOR = 3600 / ( Since 28 + 28) = 64 [sheets / hour], it is possible to improve the throughput while maintaining the effect of improving the high resolution and the DOF. Further, since the exposure time is long, the number of EGA points can be increased, and the alignment accuracy is improved.
[0181]
In the first embodiment, the case where the present invention is applied to an apparatus that exposes a wafer using the double exposure method has been described. However, as described above, this is achieved by the apparatus of the present invention. When performing wafer exchange and wafer alignment in parallel on the other wafer stage side that can be moved independently while performing double exposure with two reticles on the wafer stage side of the conventional wafer stage, This is because there is a particularly great effect that a throughput higher than that of single exposure can be obtained and the resolving power can be greatly improved. However, the scope of application of the present invention is not limited to this, and the present invention can also be suitably applied when exposure is performed by a single exposure method. For example, assuming that the processing times (T1 to T4) of an 8-inch wafer are the same as described above, when performing exposure processing by a single exposure method using two wafer stages as in the present invention, T1, T2, and T3 are set as follows. When one group (30 seconds in total) and parallel processing with T4 (28 seconds) are performed, the throughput becomes THOR = 3600/30 = 120 [sheets / hour], and the single exposure method is performed using one wafer stage. Compared to the conventional throughput (THOR = 62 [sheets / hour], it is possible to obtain a throughput that is almost twice as high.
[0182]
In the above embodiment, the case where the scanning exposure is performed by the step-and-scan method has been described. However, the present invention is not limited to this, and the case where the stationary exposure is performed by the step-and-repeat method and the EB Of course, the present invention can also be applied to exposure apparatuses, X-ray exposure apparatuses, and stitching exposure in which chips are combined.
[0183]
<< Second Embodiment >>
Next, a second embodiment of the present invention will be described with reference to FIGS.
[0184]
In the second embodiment, pre-reading AF / AL measurement is performed using one wafer stage WS, and exposure is performed by performing focus / leveling control based on the measurement result.
[0185]
FIG. 19 shows a schematic configuration of a projection exposure apparatus 214 according to the second embodiment. This projection exposure apparatus 214 is a step-and-scan type scanning exposure type as in the first embodiment. The projection exposure apparatus is the same as the projection exposure apparatus 10 of the first embodiment shown in FIG. 1 in the basic components, and the same components are denoted by the same reference numerals and the description thereof is omitted. The difference from the projection exposure apparatus 10 of the first embodiment is that one wafer stage WS is configured, and the AF / AL system for measuring the surface position on the wafer W for pre-reading control is used for the exposure area IF. A grazing incidence irradiation optical system 151 provided on one side and the other side in the scanning direction and configured such that a plurality of detection points are arranged in a range wider than the width of the exposure region IF in the non-scanning direction The optical system 161 is a point. Further, the wafer stage WS of the second embodiment is provided with a Z leveling stage LS as a substrate driving system for holding the wafer W and performing minute driving and tilt driving in the Z-axis direction.
[0186]
When the arrangement of AF detection points for prefetch control with respect to the exposure area IF is seen in a perspective view in FIG. 20, it is detected in the non-scanning direction (± X direction) in the scanning direction (+ Y direction) of the exposure area IF. A detection area AFE (see FIG. 25) composed of points AF1 to AF9 is provided and arranged in a range larger than the width of the exposure area IF in the non-scanning direction. Further, in the scanning direction (−Y direction) of the exposure area IF, a detection area ABE (see FIG. 25) constituted by detection points AB1 to AB9 is provided in the non-scanning direction (± X direction). They are arranged in a range larger than the width in the non-scanning direction. These detection points AF1 to AF9 and detection points AB1 to AB9 are arranged on the front side in the scanning direction (+ Y direction and −Y direction) for scanning the exposure area IF, respectively, and the wafer W surface at each detection point is a predetermined one. The relative position of how much is deviated from the reference plane is detected prior to exposure of the shot area.
[0187]
21 is a side view of FIG. 20 viewed from the scanning direction, FIG. 22 is a plan view of FIG. 21, and FIG. 23 is a side view of FIG. 22 viewed from the non-scanning direction.
[0188]
As shown in FIGS. 22 and 23, the light beams emitted from the oblique incidence AF / AL irradiation optical systems 151a and 151b are detected points AB1 to AB9 extending in the non-scanning direction on the wafer W surface. Detection points AF1 to AF9 are formed, and the light beam reflected by the wafer W surface is received by the oblique incidence AF / AL focusing optical systems 161a and 161b. This is the N.I. of the projection lens of the projection optical system PL. A. Since the working distance between the lower surface of the projection lens and the wafer W becomes narrower as the numerical aperture increases, the exposure area IF cannot be measured by the oblique incidence AF system. Even in such a case, complete pre-reading measurement is executed. This is what we did.
[0189]
As shown in FIGS. 21 and 23, the shape near the lower end of the projection optical system PL of the second embodiment is an inverted truncated cone, and a plurality of irradiations from the irradiation optical systems 151a and 151b. Light is irradiated to each detection point position of the wafer W, and reflected light from the surface of the wafer W passes through both sides of the projection optical system PL and is received by the condensing optical systems 161a and 161b. Yes. This is to prevent the AF light flux from being scattered near the lower end of the projection optical system PL. A. The parallel plate 216 is rectangular on the lowermost surface of the projection optical system PL in accordance with the scanning direction in order to adjust it to the 45 ° direction of the projection optical system PL and to correct the aberration of the projection lens constituting the projection optical system PL. Is arranged. Then, before and after the parallel plate 216 in the scanning direction, AF detection points extending in a one-dimensional non-scanning direction are arranged at two locations for + Y scanning and −Y scanning. Compared with the two-dimensional detection type AF mechanism described in, for example, JP-A-6-283403, the AF measurement at the exposure position cannot be performed, but a spot group is formed long in the non-scanning direction. In addition, since the detection points are arranged one-dimensionally, there is an advantage that an offset error due to in-plane curvature of each AF spot can be easily corrected. Further, when adopting a method of forming interference fringes in the non-scanning direction by two-way incidence, etc., one-dimensional processing for detecting the AF / AL position by one-dimensional image processing from the spacing error and position variation of the interference fringes. Since it is a prefetch control method, there exists an advantage which becomes easy to apply this invention. In addition, since the light flux is divided into two areas of the detection areas AFE and ABE, a cover that does not block each light flux is installed, and a temperature-adjusted gas is allowed to flow through the cover so that the AF / If the AL accuracy is improved, the detection error can be further reduced.
[0190]
Next, prefetch control when the shot arrangement is larger than the outer periphery of the wafer W by the projection exposure apparatus 214 of the second embodiment will be described. For example, FIG. 32 is a diagram showing a comparative example related to the prefetch control when the shot arrangement is larger than the outer periphery of the wafer W. In FIG. 32, the exposure area IF to be scanned and exposed is scanned in the scanning direction (in the direction of the arrow above the paper surface: the exposure area IF and AF detection points AF1 to AF5 are actually fixed, and the wafer W is scanned with respect to these. For convenience, the AF detection points AF1 to AF5 arranged in the non-scanning direction are arranged in front of the exposure area IF and the AF detection point shown in the drawing so as to be scanned with respect to the wafer surface. The detection area AFB composed of the AF detection points AF1 to AF5 performs AF measurement in order to perform complete prefetch control, and the width of the detection area AFB is substantially the same as the width of the exposure area IF in the non-scanning direction. It consists of When prefetch control is performed using a projection exposure apparatus configured as shown in FIG. 32 (comparative example), AF output values from AF1 to AF5 are obtained as the stage moves, as shown in FIG. It is done. The horizontal axis of FIG. 33 indicates the stage movement time [t], and the vertical axis indicates the relative position [μm] in the Z direction with respect to the wafer surface position. As shown in the diagram of FIG. 33, the detection points AF5 to AF3 on the wafer W surface sequentially indicate the wafer surface positions as the detection points move in the scanning direction. Since AF1 does not pass through the wafer surface to the end, a normal output value cannot be obtained. As described above, if it is attempted to perform the pre-reading control of the entire shot area by the five-point measurement according to the comparative example of FIGS. 32 and 33, an error occurs in the shot area near the outer periphery of the wafer, and AF / AL control can be performed. Sometimes it disappeared. In order to avoid this, pre-reading control is performed while scanning from the inside to the outside of the wafer W, or the AF in the missing shot area is performed using the measurement data of the wafer surface position of the adjacent shot. It was necessary to change to the / AL control sequence.
[0191]
On the other hand, in the second embodiment, as shown in FIG. 20, the wafer surface position of the adjacent shot area is measured by increasing the width of the AF detection point in the non-scanning direction with respect to the exposure area IF. This makes it possible to perform pre-reading control that makes it difficult for errors to occur by using the measurement result.
[0192]
FIG. 24 is a plan view of the wafer W for explaining the prefetch control method using the AF / AL system according to the second embodiment. FIG. 24 shows the grouping of the shot areas when the pre-read control is performed in the order in which the wafer W can be exposed at the highest speed. FIG. 25 shows the positional relationship between the exposure area IF and the AF detection point during focus measurement. Here, which AF detection point (AF1 to AF9, AB1 to AB9) is used for each shot area to perform AF measurement is like “A, B, C, D, E, F, AF, AB”. Grouping is performed, and detection point positions to be used for each of these groups are determined in advance as shown in the table of FIG. In the horizontal direction of the table shown in FIG. 26, the positions of AF detection points (AF1 to AF9, AB1 to AB9) to be used are shown, and in the vertical direction, group names obtained by grouping shot areas are shown. Control is performed by the main controller 90 so that pre-reading control is performed using AF detection points (sensors) marked with ○ at those cross positions.
[0193]
For example, FIG. 27 shows the positional relationship between the AF detection point used when exposing the shot area 212 of the A group (for example, when the upper left shot area in FIG. 24 is exposed) and the wafer surface read-ahead control start. Is shown. In this case, control is performed by main controller 90 so that AF detection points AF7, AF8, AF9 existing at a position separated from exposure area IF by a distance L in the scanning direction are used. Here, at the start of the prefetch control shown in FIG. 27, since the three AF detection points (AF7, AF8, AF9) designated by the main controller 90 are all located on the wafer surface, the shot indicated by the broken line The pre-reading control is performed based on the measurement values measured at the three AF detection points AF7, AF8, and AF9 until the exposure of the area 212 is completed.
[0194]
26 and 27 is an “AF detection point fixing method” in which AF detection points used in accordance with shot areas are fixed in advance. The actual measurement in the shot area 212 in the example of FIG. 27 is only the detection point AF7, and the AF / AL control by prefetching is performed by using the measurement values of the detection points AF8 and AF9 on the adjacent shot areas. Can do.
[0195]
Further, when there is no AF detection point that is missing during the pre-reading control in the shot area, that is, in the case of the group AF or group AB shown in FIG. 24, the detection located within the shot area specified in the table of FIG. Measurement is performed using only the points AF3 to AF7 and AB3 to AB7, and the detection points AF1, AF2, AF8 and AF9 outside the shot area are not used.
[0196]
In the case of group E shown in FIG. 24, measurement is performed using detection points AF1 to AF5 as specified in the table of FIG. In this group E, as shown in FIG. 24, the detection points AF6 and AF7 can be measured during the pre-reading control. Therefore, the accuracy is higher when the measurement values of the detection points AF6 and AF7 are used. There is an advantage that the control processing of the main controller 90 can be simplified because it is not necessary to change the AF detection point used in one exposure operation when setting the shot arrangement. Therefore, when there is a margin in the control process, the measurement values of the detection points AF6 and AF7 may be used to perform more accurate focus and leveling control.
[0197]
Next, a prefetch control method other than the above will be described.
[0198]
In FIG. 28, a sensor capable of AF measurement on the wafer W surface without changing the number of AF detection points to be used is sequentially moved in the scanning direction, and the AF detection points are moved to a predetermined shot area. This is an “AF detection point moving type” that performs focus measurement of the wafer surface. As an AF measurement method for pre-reading control, in principle, it is the measurement method with the highest accuracy. In carrying out this “AF detection point movement type”, the main controller 90 detects any AF within the effective area inside the forbidden band defined at the peripheral edge of the wafer W while moving the wafer W in the scanning direction. In order to ascertain whether or not a dot has been applied, control is performed so that the AF detection point is switched based on the peripheral position information of the wafer, the position information of the AF detection point, and the position information of the shot area to be exposed. For example, in the case of FIG. 28, measurement is first performed using three detection points AF7, AF8, and AF9, then detection points AF6, AF7, and AF8, and then detection points AF5, AF6, and AF7. Finally, as in detection points AF4, AF5, and AF6, the sensors are switched so that three detection points in the effective area on the wafer surface and in the shot area 212 are selected as much as possible. Thus, even when the exposure area IF scans and exposes the outer periphery of the wafer W provided with the shot area from the outside to the inside (in fact, the wafer W side moves relative to the exposure area IF that does not move). Relative scanning is performed), and pre-reading control makes it possible to quickly drive the wafer surface position onto the imaging surface of the projection optical system PL, thereby enabling quick and highly accurate focus and leveling control. As described above, grouping may be performed as described above, or the outputs of all sensors may be monitored at all times, and detection points that are within an allowable value may be used.
[0199]
In addition, in FIG. 29, regardless of the number of AF detection points to be used, all the detection points that can be measured are “AF sensor number, position variable type”. In this case, the use of a plurality of AF detection points increases the averaging effect and makes it difficult to be affected by warpage of the outer peripheral portion of the wafer. In addition, this effect is further enhanced when the reproducibility is poor in AF measurement. In the case of FIG. 29 as well, as in FIG. 28, the main controller 90 moves any of the AF detection points within the effective area inside the forbidden band defined at the peripheral edge of the wafer W while moving the wafer W in the scanning direction. In order to ascertain whether or not the exposure has occurred, control is performed so that the AF detection point is switched based on the wafer outer periphery position information, the position information of the AF detection point, and the position information of the shot area to be exposed. Here, since the number of AF detection points is not limited, AF / AL measurement is performed using all the detection points included in the effective region among the detection points AF1 to AF9. As a result, even when a shot area near the outer periphery of the wafer W is scanned and exposed from the outside to the inside, it is possible to quickly drive the wafer surface position onto the imaging surface of the projection optical system PL by performing the pre-reading control. Thus, quick and highly accurate focus and leveling control can be performed.
[0200]
By using the look-ahead control method as described above, for example, by adding to the technique described in Japanese Patent Laid-Open No. Hei 6-283403, the quickest is possible regardless of the vicinity of the wafer outer periphery or the shot area in the wafer. It is possible to perform high-speed and high-accuracy scanning exposure on each shot area on the wafer surface in accordance with the exposure sequence that can be performed at the same time.
[0201]
Next, a description will be given of which data is adopted as the prefetch measurement data when performing the prefetch control described above. For example, if the width of the exposure area IF in the scanning direction is set to 6 to 8 mm and the scanning speed of the wafer during exposure is set to 80 to 90 mm / sec, the pre-reading AF detection point is determined depending on the waviness frequency of the wafer surface. It is desirable that acceleration + settling distance (L = 8 to 10 mm) until reaching the wafer scanning speed at the time of exposure because there is no unnecessary run-up in terms of throughput. This is because the pre-reading position is calculated based on the information on the wafer outer periphery position, the shot area coordinate position, the distance L from the exposure area IF to the AF detection point in the data file, and the pattern prohibition band (usually about 3 mm: The sensor is used when the pre-reading start position is on the inner side of FIG. 30). However, the outer periphery of the wafer is easily affected by warpage and dust, and is the pre-reading start position set in the data file. However, the position of the wafer surface may not be accurately represented.
[0202]
Here, with reference to FIG. 30 and FIG. 31, a description will be given of how to minimize the control error in the above case. In FIG. 30, in the above-described “AF detection point fixing method”, when AF detection points AF6 to AF9 are used as in group C, for example, according to the calculation on the data file, the prefetch control start coordinates are indicated by ▲ in FIG. 1), but it is assumed that (1) is considerably defocused due to the influence of the pattern forbidden band. As shown in FIG. 31, when the prefetch control is started at the position {circle around (1)}, each sensor output value in this case has a considerable error with respect to the target due to the influence of the detection point AF6. Since the sensor is located at the rightmost end of the AF detection point, it has a significant influence on the leveling control.
[0203]
If the pre-read detection point is designed to move at 80 mm / sec and 70% control is possible during scanning, the detection point AF 6 provided at the right end has an error of several μm or less in the Z-axis direction. If there is, a smaller error is required for the averaging effect during the pre-reading control. However, when there is an error of several tens of μm in the Z-axis direction, if leveling control is performed with the result of taking that value into account as a target value, an unacceptable error occurs. For this reason, the prefetch measurement is started when the result of monitoring the data at the time of starting the measurement of the prefetch detection point is within the allowable range, and when the result exceeds the allowable range, the point within the allowable range (2) It is desirable not to use the measurement result of the prefetch control until.
[0204]
In the “AF sensor position moving type” and “AF sensor number and position variable type” described above, only the AF detection points that are within the allowable range can be used.
[0205]
Furthermore, if an allowable range is set for the measurement error between the detection points, and AF detection points other than the AF detection points that cause the allowable range to be exceeded are used, for example, dust provided on the back side of the wafer It is possible to reduce the frequency at which an AF error occurs due to the influence of the above. However, since these methods require the wafer surface to be within the allowable range from the target AF driving position in advance, global AF or global AF / AL is executed based on the focus measurement result during wafer alignment. It is necessary to keep it.
[0206]
As described above, according to the projection exposure apparatus 214 according to the second embodiment, the exposure on the wafer W is performed when the pattern on the reticle R is scanned and exposed on the wafer W via the projection optical system PL. A plurality of AF detection points are arranged in a region wider than the region IF in the non-scanning direction. Prior to exposure of the shot area 212 near the outer periphery of the wafer W, focus pre-reading measurement is started when a part of the plurality of AF detection points is applied on the wafer W surface, and based on the measurement result. Since the focus control is started, it is possible to use the inner focus information that cannot be measured by the prefetch control of the conventional scanning projection exposure apparatus as the prefetch data for focus control. Therefore, highly accurate focus control can be performed without degrading the throughput.
[0207]
Further, when the number of AF detection points on the wafer W surface at the plurality of AF detection points is one, the leveling control at the time of exposure uses leveling information of adjacent shots or uses a fixed value (for example, an inclination amount in the X direction, Since both the tilt amounts in the Y direction are “0”), the pre-read control can be started even in the missing shot region near the outer periphery of the wafer.
[0208]
Furthermore, when pre-reading control is executed at one AF detection point on the wafer W surface, if a different AF detection point is placed on the wafer W surface, pre-reading measurement is started at that position, and both by the start of exposure. When the leveling control using the pre-reading measurement result becomes possible, the leveling control by the pre-reading measurement in the shot is switched from the leveling correction of the adjacent shot described above or the leveling correction by the fixed value. By doing so, it is possible to perform focus and leveling control with high accuracy even in the case of pre-reading control with respect to a missing shot on the outer peripheral portion.
[0209]
The AF detection points used when performing the pre-reading measurement are the outer peripheral position information of the wafer W, the position information of a plurality of AF detection points, and the shot areas on the wafer W when the shot arrangement on the wafer W is determined. The detection based on the AF detection point used for the pre-reading control is always executed at the time of wafer scanning, and the pre-reading control is performed when the detection result at any of the detection points falls within the allowable value. Since it is started, when the influence of the outer peripheral edge of the wafer is more than expected from the design coordinates, the focus control is not started at that point, and the occurrence of a large focus and leveling error can be prevented. .
[0210]
In the second embodiment, the case where one wafer stage is used has been described. However, even when two wafer stages as described in the first embodiment are used, it is needless to say that the second embodiment is carried out. Is possible. In this case, it is not always necessary to perform focus measurement in advance using the alignment system, but focus measurement may be performed using the alignment system for the purpose of higher accuracy. Further, when focus measurement by the alignment system is not performed, there is an advantage that the operation time can be used as another operation time.
[0211]
【The invention's effect】
As explained above, The present invention According to the above, the focus and leveling control can be performed with high accuracy while further improving the throughput. But it can.
[Brief description of the drawings]
FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to a first embodiment.
FIG. 2 is a perspective view showing a positional relationship among two wafer stages, a reticle stage, a projection optical system, and an alignment system.
FIG. 3 is a plan view showing a configuration of a drive mechanism of the wafer stage.
FIG. 4 is a diagram showing AF / AL systems provided in the projection optical system and the alignment system, respectively.
FIG. 5 is a diagram showing a schematic configuration of a projection exposure apparatus showing a configuration of an AF / AL system and a TTR alignment system.
6 is a diagram showing the shape of the pattern forming plate of FIG. 5. FIG.
FIG. 7 is a plan view showing a state in which a wafer exchange / alignment sequence and an exposure sequence are performed using two wafer stages.
8 is a view showing a state where the wafer exchange / alignment sequence and the exposure sequence in FIG. 7 are switched. FIG.
FIG. 9 is a diagram showing a reticle stage for double exposure that holds two reticles.
10A is a view showing a state in which the wafer is exposed using the pattern A reticle of FIG. 9, and FIG. 10B is a view of performing the wafer exposure using the pattern B reticle in FIG. 9; FIG.
FIG. 11 is a diagram showing an exposure order for each shot area on a wafer held on one of two wafer stages.
FIG. 12 is a diagram showing a mark detection order for each shot area on a wafer held on the other of two wafer stages.
FIG. 13 is a plan view of a wafer showing an exposure order of a scanning projection exposure apparatus when all shot arrangements are contained in the wafer.
14A is an enlarged plan view for performing pre-reading AF measurement at the position A in FIG. 13, and FIG. 14B is an enlarged plan view for performing pre-reading AF measurement at the position B in FIG. 13; FIG. 14C is an enlarged plan view for performing pre-reading AF measurement at the position C in FIG. 13.
FIG. 15 is a diagram showing a look-ahead control result of a comparative example in a shot area near the wafer outer periphery.
FIG. 16 is a plan view of a wafer showing an alignment sequence of a scanning projection exposure apparatus when all shot arrangements are contained in the wafer.
FIG. 17 is a diagram showing a prefetch control result in the first embodiment.
FIG. 18 is a diagram showing a look-ahead control result when there is an error in measurement reproducibility in the first embodiment.
FIG. 19 is a view showing a schematic configuration of a projection exposure apparatus according to a second embodiment.
FIG. 20 is a perspective view showing the arrangement of AF detection points for prefetch control with respect to an exposure area.
FIG. 21 is a side view of FIG. 20 viewed from the scanning direction.
22 is a plan view of FIG. 21. FIG.
FIG. 23 is a side view of FIG. 22 viewed from the non-scanning direction.
FIG. 24 is a plan view of a wafer W for explaining a prefetch control method using an AF / AL system according to the second embodiment.
FIG. 25 shows the positional relationship between the exposure area IF and the AF detection point at the time of focus measurement.
FIG. 26 is a selection diagram for designating an AF detection point position used for AF measurement for each shot area;
FIG. 27 is a diagram showing an AF detection point used when exposing a shot area belonging to an A group and a position at the start of prefetch control on the wafer surface;
FIG. 28 is a diagram showing AF detection points when performing focus measurement on a wafer surface by moving the AF detection points without changing the number of AF detection points to be used.
FIG. 29 is a diagram showing AF detection points when focus measurement of a wafer surface is performed using all measurable AF detection points.
FIG. 30 is a diagram illustrating an AF detection point used when exposing a shot area belonging to a group C and a position at the start of prefetch control on the wafer surface;
31 is a diagram showing a prefetch control result in FIG. 30. FIG.
32 is a diagram showing a comparative example regarding prefetch control when the shot arrangement is larger than the outer periphery of the wafer W. FIG.
FIG. 33 is a diagram showing a comparative example regarding prefetch control when the shot arrangement is larger than the outer periphery of the wafer W;
[Explanation of symbols]
10 Projection exposure equipment
24a, 24b alignment system
38 Stage control means
90 Main controller
130, 132, 134 AF / AL system
151 Irradiation optical system
161 Condensing optical system
210, 212 Shot area
214 Projection exposure apparatus
W, W1, W2 Wafer (Sensitive substrate)
WS, WS1, WS2 Wafer stage
PL projection optical system
R reticle
IF exposure area
IA lighting area
AF1 to AF9, AB1 to AB9 AF detection points
LS, LS1, LS2 Z leveling stage (substrate drive system)

Claims (8)

A projection exposure apparatus that exposes each of a plurality of shot areas on the sensitive substrate by projecting a pattern image onto the exposure area via the projection optical system and moving the sensitive substrate in the scanning direction relative to the exposure area. Because
A first substrate stage capable of holding a sensitive substrate and moving in a two-dimensional plane;
A second substrate stage that holds a sensitive substrate and is movable independently of the first substrate stage in the same plane as the first substrate stage;
At least one alignment system that is provided separately from the projection optical system and that measures a mark on the sensitive substrate held on the substrate stage;
A first detection system for detecting a relative position of a sensitive substrate surface with respect to a predetermined reference surface during mark measurement using the alignment system;
A second detection system for detecting a relative position of a sensitive substrate surface during exposure using the projection optical system with respect to a predetermined reference surface;
A substrate driving system provided on each of the first substrate stage and the second substrate stage for adjusting the surface position of the sensitive substrate held on the stage;
While the mark measurement operation using the alignment system is performed while performing detection by the first detection system in one of the first substrate stage and the second substrate stage, the projection optical system is used in the other stage. After controlling the two stages so that an exposure operation using the projection optical system is performed, the one stage is controlled so that an exposure operation using the projection optical system is performed on the one stage, and the sensitive substrate When exposing a shot region in the vicinity of the outer periphery set so as to be scanned from the outside to the inside, the one of the stages is based on the detection result of the first detection system obtained during the mark measurement operation of the one stage. A control means for controlling a substrate driving system of the stage.   When the control means exposes a shot area in the vicinity of the outer periphery set to be scanned from the outside to the inside of the sensitive substrate, the mark measuring operation of the one stage is performed without detecting the surface of the shot area. 2. The projection exposure apparatus according to claim 1, wherein a substrate driving system of the one stage is controlled based on a detection result of the first detection system obtained inside. The pattern image of the mask is moved by moving the sensitive substrate in the scanning direction with respect to the exposure region conjugate with the illumination region in synchronization with the movement of the mask in the scanning direction with respect to the illumination region illuminated with the illumination light. A scanning type projection exposure apparatus that exposes the sensitive substrate via a projection optical system,
A first substrate stage capable of holding a sensitive substrate and moving in a two-dimensional plane;
A second substrate stage that holds a sensitive substrate and is movable independently of the first substrate stage in the same plane as the first substrate stage;
At least one alignment system that is provided separately from the projection optical system and that measures a mark on the sensitive substrate held on the substrate stage;
A first detection system for detecting a relative position of a sensitive substrate surface with respect to a predetermined reference surface during mark measurement using the alignment system;
A second detection system for detecting a relative position of a sensitive substrate surface during exposure using the projection optical system with respect to a predetermined reference surface;
A substrate driving system provided on each of the first substrate stage and the second substrate stage for adjusting the surface position of the sensitive substrate held on the stage;
While the mark measurement operation using the alignment system is performed while performing detection by the first detection system in one of the first substrate stage and the second substrate stage, the projection optical system is used in the other stage. When the one stage is controlled such that the exposure operation using the projection optical system is performed on the one stage after the two stages are controlled so that the exposure operation using the projection is performed. When exposing a shot region in the vicinity of the outer periphery set to be scanned from the outside to the inside of the sensitive substrate with respect to the exposure region of the plurality of shot regions on the sensitive substrate held on the stage, the one The detection result of the first detection system obtained during the mark measurement operation of the stage and the detection result of the second detection system obtained during the exposure operation of the one stage And a control means for controlling the substrate drive system of the one stage using only the detection result of the second detection system when controlling the substrate drive system of the stage based on this and exposing other shot areas. . A scanning exposure method for exposing each of a plurality of shot regions on a sensitive substrate by projecting an image of a pattern onto the exposure region via a projection optical system and moving the sensitive substrate in the scanning direction with respect to the exposed region Because
Two substrate stages are prepared, each holding a sensitive substrate and independently movable within the same two-dimensional plane;
Measuring a mark on the sensitive substrate held on one of the two stages;
Detecting a relative position of a sensitive substrate held on the one stage with respect to a predetermined reference plane while a mark measuring operation is being performed on the one stage;
Exposing a sensitive substrate held on the other of the two stages while a mark measurement operation is being performed on the one of the stages;
When exposing a shot area in the vicinity of the outer periphery on the sensitive substrate held by the one stage, which is set to be scanned from the outside to the inside of the sensitive substrate after the exposure operation of the other stage is completed, A scanning exposure method comprising adjusting a surface position of a sensitive substrate held on the one stage based on a detected relative position.   When exposing a shot area in the vicinity of the outer periphery on the sensitive substrate that is set to be scanned from the outside to the inside of the sensitive substrate, without detecting the surface of the shot area, The scanning exposure method according to claim 4, wherein the surface position of the sensitive substrate held on the one stage is adjusted based on the detected relative position. A projection exposure method for exposing a sensitive substrate by projecting an image of a pattern onto an exposure region via a projection optical system and moving the sensitive substrate in a scanning direction with respect to the exposure region,
Holding a sensitive substrate on a first substrate stage movable in a two-dimensional direction;
Independent of the first substrate stage, holding a sensitive substrate on a second substrate stage movable in a two-dimensional direction;
The measurement sequence for detecting the alignment mark on the sensitive substrate held on one of the first and second substrate stages is parallel to the exposure sequence for exposing the sensitive substrate on the other substrate stage. And run;
Detecting surface position information in the vicinity of the outer periphery of the sensitive substrate on the one substrate stage during the measurement sequence;
After the measurement sequence using the one substrate stage and the exposure sequence using the other substrate stage are completed, the other substrate stage is moved to the exchange position of the sensitive substrate, and the one substrate stage is moved to the projection optics. Move to the image side of the system;
The shot area in the vicinity of the outer periphery of the sensitive substrate held on the one substrate stage is exposed so that the exposure area scans from the outside to the inside of the sensitive substrate, and the surface detected during the measurement sequence at the time of exposure A projection exposure method for performing surface position adjustment of a sensitive substrate held on the one substrate stage based on position information.   When exposing the shot area near the outer periphery of the sensitive substrate so that the exposure area scans from the outside to the inside of the sensitive substrate, the surface of the shot area to be exposed is not detected and the measurement sequence is performed. The projection exposure method according to claim 6, wherein the surface position adjustment of the sensitive substrate held on the one substrate stage is executed based on the detected surface position information.   The projection exposure method according to claim 6, wherein an alignment mark in the vicinity of the outer periphery of the sensitive substrate held on the one substrate stage is detected during the measurement sequence.

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