DE69604524T2 - Scanning exposure apparatus and exposure method using the same - Google Patents

Description

This invention relates to a scanning exposure apparatus and an exposure method using the same, wherein a pattern of a reticle is transferred to a wafer while the reticle and the wafer are scanned in a time relationship and with respect to a projection optical system.

Fig. 12 shows an example of a relative positional relationship between a wafer and a reticle in a step-and-repeat exposure apparatus as well as the manner of detecting an image plane of an associated projection optical system.

In Fig. 12, reference numeral 200 denotes a Hg lamp, which is a light source of an illumination system. 210 denotes an elliptical mirror for collecting the light from the Hg lamp 200, and 202 denotes a condenser lens for collecting the light from the elliptical mirror 210 on a reticle 6. The reticle 6 is formed with a transmission mark for the alignment operation.

Reference numeral 13 denotes a projection optical system, and 14 denotes a wafer. 15 denotes a wafer receiving device, and 203 denotes a transmission mark of the wafer which corresponds to the transmission mark of the reticle 6. 204 denotes a light quantity sensor for detecting the amount of light passing through the transmission mark 203 of the wafer. The light quantity sensor 204 is formed integrally with the transmission mark 203 of the wafer. 205 denotes an XYZ table for moving the wafer in the X, Y and Z directions, and 206 denotes a position detection system for Detecting the position of the XYZ table 205. Denoted by 207 is a light quantity measuring system for the light quantity sensor, and 208 is a control system.

In this type of exposure apparatus, the transmission mark 203 and the light quantity sensor 204 arranged on the X-Y-Z table 205 are formed integrally with each other, and by detecting the position of the largest light quantity while moving it in the X, Y and Z directions, the position of a projected image of the reticle as well as the position of its image plane are determined (Japanese Patent Publication No. 58766/1990).

The above-mentioned method in the step-and-repeat exposure apparatus is effective in a case where the reticle is kept stationary with respect to the projection optical system.

However, in the scanning exposure devices, which have received much attention recently, the following problems occur.

(1) Spottiness:

In the scanning exposure apparatus, in many cases, a deep ultraviolet laser device (e.g. KrF excimer laser device or ArF excimer laser device) is used as a high energy and short wavelength light source to increase the resolution and productivity.

Such a deep ultraviolet laser device generally has high coherence, and an interference pattern (spot pattern) appears on the surface of a wafer.

In the scanning exposure apparatus, a reticle and a wafer are moved in a scanning manner relative to an illumination light (or to the projection system) during the ongoing exposure process. This creates the effect of such a speckle pattern is substantially reduced. When the method or structure for detecting the position of a projected image of the reticle or the position of the image plane while holding the reticle stationary is applied to such a scanning exposure apparatus, the detection is substantially influenced by the speckle pattern because the detection is to be carried out in a substantially stationary state (ie, without utilizing the advantageous features of the scanning exposure apparatus). Consequently, the accurate light quantity measurement is not achievable.

(2) Effective light source difference:

In the scanning exposure apparatus, compared with the step-and-repeat exposure apparatus, the light energy density in the exposure light irradiation area should be set higher in order to maintain the throughput. Finally, special attention should be paid to the design in terms of durability of the optical components. As a measure for this, it may be advantageous to provide an effective light source during the scanning movement with respect to the scanning direction (the shape of the effective light source is different in the exposure area in the scanning direction of the projection optical system). This enables the separation within the projection optical system of the light energy collection position between the scanning direction and a direction perpendicular to the scanning direction, and prevents the concentration of the light energy on an element or elements constituting the projection optical system.

However, when the above-mentioned measure is applied, the effective light source is different between the scanning state and the stationary state.

In other words, in the method or structure for detecting the position of the projected image of the reticle or for detecting the image plane in a substantially stationary state, it is necessary to detect the position of the projected image of the reticle or the image plane in a substantially stationary state due to the difference in the effective Light source in the exposure area, it is difficult to accurately detect the position of the projected image of the reticle or the image plane as in the scanning state.

(3) Position of the scanning table:

In scanning exposure apparatuses, the position of the reticle stage for scanning a reticle and the position of the scanning stage for scanning a wafer are controlled to maintain an ideal position during the scanning movement. However, no special means is provided for detecting the change in position between the scanning state and the stationary state. In the method which carries out the measurement in a substantially stationary state, the effect of the position of the scanning stage is not taken into account, and therefore it is difficult to accurately detect the position of the projected image of the reticle and the image plane in the scanning state.

It is an object of an aspect of the present invention to provide a method and/or an apparatus for a scanning exposure apparatus whereby the position of a projected image of the reticle, the image plane position and/or a magnification error in the scanning state can be accurately measured.

According to one aspect of the present invention, there is provided a scanning exposure apparatus comprising: a first movable table for supporting a first object which is movable in a predetermined one-dimensional direction, a second movable table for supporting a second object which is movable in a predetermined one-dimensional direction, a projection system for projecting a pattern of the first object onto the second object through a projection optical system while scanningly moving the first and second movable tables in a time relationship with respect to the projection optical system, a first mark formed on the first object and including a plurality of marks which regularly arranged along a scanning direction, a reference plate fixedly arranged on the second movable table and having a second mark including a plurality of marks regularly arranged along the scanning direction, a third movable table for supporting the second movable table which is movable in a direction different from the moving direction of the second table, photodetecting means fixedly arranged on the third movable table, and control means having a first function of moving the second and third movable tables in a manner to arrange the reference plate and the photodetecting means at a position of an image of the first mark as projected by the projection optical system, and having a second function of detecting the image of the first mark by the second mark using the photodetecting means during movement of the first and second movable tables in a time relationship with respect to the projection optical system.

In a preferred embodiment according to this aspect of the present invention, the second movable table comprises a displaceable device which can be displaced in a direction of the optical axis of the projection optical system to change the position of the reference plate with respect to the direction of the optical axis so that the photodetecting device detects the image of the first mark through the second mark.

In another preferred embodiment of this aspect of the present invention, each of the first and second marks comprises a mark having a plurality of marks arranged periodically in a regular manner.

In a further preferred embodiment of this aspect of the present invention, each of the first and second marks comprises a mark having a plurality of Markings that have different inclinations.

In a still further preferred embodiment of this aspect of the present invention, the control means determines the position at which the first mark is projected onto the second mark by the projection optical system, based on a signal in response to the detection of the image of the first mark through the second mark by the photodetecting means and based on the positions of the first and second movable tables at the time the signal is detected.

In a still further preferred embodiment of this aspect of the present invention, the control means determines the position in the optical axis direction of the projection optical system when the first mark is imaged by the projection optical system, based on a signal in response to the detection by the photodetecting means of the image of the first mark by the second mark and based on the position of the second movable table when the signal is detected.

According to another aspect of the present invention, there is provided an exposure method usable with a scanning exposure apparatus for projecting a pattern of a first object through a projection optical system onto a second object during scanning movement of the first and second objects in a time relationship with respect to the projection optical system, the method comprising the steps of: providing a first mark having a plurality of markings regularly arranged along a scanning direction, providing a reference plate fixedly mounted on a movable table for supporting the second object and having a second mark having a plurality of markings regularly arranged along the scanning direction, arranging a photodetector in a position in which an image of the first mark is or is to be projected by the projection optical system, and capturing the image of the first mark by the second mark using the photodetecting means during the scanning movement of the first object and the reference plate in a time relationship with respect to the projection optical system.

In a preferred embodiment according to this aspect of the present invention, in the detecting step, the image of the first mark is detected by the second mark using the photodetecting means while changing the position of the reference plate with respect to the direction of the optical axis of the projection optical system.

In another preferred embodiment of this aspect of the present invention, the method further comprises determining the position into which the first mark is or is to be projected onto the second mark by the projection optical system based on the positions of the first and second marks at a time when the image of the first mark is captured by the second mark using the photodetecting device.

In a further preferred embodiment of this aspect of the present invention, the method further comprises: determining the position with respect to the optical axis direction in which the first mark is imaged by the projection optical system based on a signal in response to the detection of the image of the first mark by the second mark using the photodetecting means and based on the position of the reference plate with respect to the optical axis direction at a time of detecting the signal.

According to a further aspect of the present invention, a method for producing a device which is usable with a scanning exposure apparatus for projecting a pattern of a reticle through a projection optical system onto a wafer while scanning the reticle and the wafer in a time relationship with respect to the projection optical system, the method comprising the steps of: providing a reticle mark having a plurality of marks regularly arranged along a scanning direction on the reticle, providing a reference plate fixedly arranged on a movable table for supporting the wafer and having a wafer mark having a plurality of marks regularly arranged along the scanning direction, arranging a photodetector at a position into which an image of the reticle mark is or is to be projected by the projection optical system, and capturing the image of the reticle mark through the wafer mark using the photodetector during the scanning movement of the reticle and the reference plate in a time relationship with respect to the projection optical system.

The embodiments of the present invention will be described below with reference to the accompanying drawings.

Fig. 1 is a schematic and diagrammatic view of the general structure of a scanning exposure apparatus according to an embodiment of the present invention,

Fig. 2 is a schematic and perspective view of a main portion of a scanning exposure apparatus according to an embodiment of the present invention,

Fig. 3 shows an enlarged view of a transmission mark of a reticle,

Fig. 4 shows an enlarged view of a pass mark of a wafer,

Fig. 5 shows an enlarged view of a light quantity sensor,

Fig. 6 is a schematic view for explaining the manner of detecting the position of a reticle,

Fig. 7 shows a schematic view, similar to Fig. 6, for explaining the manner of detecting the position of a reticle,

Fig. 8 is a schematic view for explaining the detection process, wherein part 8-1 of Fig. 8 schematically shows the relative positional relationship between a transmission mark of a reticle and a transmission mark of a wafer, wherein part 8-2 of Fig. 8 schematically shows output signals of the light quantity sensor during reticle position measurement, wherein part 8-3 of Fig. 8 schematically shows output signals of the light quantity sensor during reticle image plane measurement, and wherein part 8-4 of Fig. 8 schematically shows output signals of the light quantity sensor during reticle magnification error measurement,

Fig. 9 is a plan view of a scanning exposure apparatus according to an embodiment of the present invention for explaining the positional relationship,

Fig. 10 shows a schematic view of an alignment microscope,

Fig. 11 shows a schematic view of a reference structure within the alignment microscope,

Fig. 12 is a schematic view of a scanning exposure apparatus according to an embodiment of the present invention for explaining the positional relationship,

Fig. 13 shows a flow chart of the manufacturing processes of the device, and

Fig. 14 shows a flow chart of a wafer process.

Fig. 1 shows a scanning exposure apparatus according to an embodiment of the present invention. Numeral 1 denotes an excimer laser device for generating pulsed light, and 2 denotes a light beam shaping device for shaping the light from the excimer laser device into a desired size. Numeral 3 denotes a mirror, and 4 denotes a photosensor for detecting the illuminance on the surface of a reticle. Numeral 5 denotes a condenser lens, and 6 denotes a reticle. Numeral 7 denotes a reticle table for holding the reticle 6 and for performing the scanning movement during the exposure process. Numeral 8 denotes a linear motor for scanning the reticle table 7 in a direction shown, and 9 denotes a grating mirror fixed to the reticle table 7. Denoted at 10 is a laser interferometer for detecting the speed or position of the reticle stage 7, and at 11 is a magnification adjustment mechanism for very slightly changing the magnification of a projection system. Denoted at 12 is a motor for operating the magnification adjustment mechanism 11, and at 13 is an optical projection system for projecting a pattern of the reticle onto a wafer 14.

15 denotes a wafer support device for holding a wafer 14, and 16 denotes an 8Z tilting table for rotating, vertically and tiltingly moving the wafer support device 15. 17 denotes a scanning table for holding the θZ table 16 and for carrying out the scanning movement during the exposure operation. 18 denotes a Y table for moving the scanning table 17 in a direction perpendicular to the scanning direction, and 19 denotes a table base on which the Y table 18 is arranged. 20 denotes an L-shaped grating mirror which is fixedly arranged on the wafer support device 15, and 21 denotes a laser inter ferometer for detecting the speed or position of the wafer holder 15 in the scanning direction. 22 denotes a laser interferometer for detecting the speed or position of the wafer holder 15 in a direction perpendicular to the scanning direction. 23 denotes a linear motor for driving the scanning table 17 in the scanning direction, and 24 denotes a linear motor for driving the Y-table 18 in a direction perpendicular to the scanning direction.

Denoted at 25 is a light emitting section of a tilt and focus detecting system for projecting a light beam onto the surface of the wafer. Denoted at 26 is a light receiving section of the tilt and focus detecting system for measuring the position of the light from the light emitting section 25 reflected by the surface of the wafer 14 to thereby measure the inclination and position of the wafer surface. The components designated at 25 and 26 cooperate to form the tilt and focus detecting system.

30 denotes an alignment microscope for measuring the position of an alignment mark on the wafer 14, and 31 denotes a TV camera arranged on the alignment microscope 30. 32 denotes a scanning table-side transmission mark plate which is fixedly arranged on the wafer holder 15, on which a reticle-side transmission mark is to be imaged. 33 denotes an imaging lens for projecting light from an image of the reticle-side transmission mark onto a light quantity sensor 34. 34 denotes the light quantity sensor which has four light detection sections. 35 denotes a light quantity sensor unit which is fixedly arranged on the Y-table and which has the imaging lens 33 and the light quantity sensor 34 formed as a unit.

Denoted at 40 is a light emission control means operable in response to an input of position data of the scanning table 17 to generate and apply a light emission command signal to the excimer laser device 1 when the scanning table 17 is displaced in a predetermined positional relationship. Denoted at 41 is a current/voltage converting means for converting a photoelectric current signal from the photosensor 4 which detects the illuminance on the reticle surface into a voltage signal. Denoted at 42 is an integrating means for integrating the voltage output signals of the current/voltage converting means 41, and denoted at 43 is an analog/digital (A/D) converting means for converting analog data of the integrating means 42 into digital data. Denoted at 44 is a memory for setting the position of a relay lens in response to a central processing unit (CPU) 70. Denoted at 45 is a digital-to-analog (D/A) converter for converting digital data from the memory 44 into analog data. Denoted at 46 is a driver for operating a relay lens drive motor 12 according to the position data from the D/A converter 45.

Denoted at 50, 53 and 56 are memories for storing scanning speed command signals for the reticle stage 7, the scanning stage 17 and the Y stage 18, respectively. Denoted at 51, 54 and 57 are A/D conversion means for converting digital data from the memories 50, 53 and 56 into analog data, and 52, 55 and 58 are drive means for amplifying analog signals from the A/D conversion means 51, 54 and 57 to drive the linear motors 8, 23 and 24. Denoted at 60, 61 and 62 are position counting means for the reticle stage 7, the scanning stage 17 and the Y stage 18, respectively. 63, 64, 65 and 66 denote A/D conversion devices for converting analog signals applied thereto from the light quantity sensor, which has four light detection sections, into digital data. 70 denotes the central 71 denotes a read-only memory (ROM) which stores various programs and control data for the CPU 70. 72 denotes a random access memory (RAM) which is used by the CPU for temporary storage.

The operation of this embodiment is explained below with reference to the items listed below:

(1) Arrangement of the reticle

(2) Detection of the reticle position

(3) Detection of the image plane of the reticle

(4) Detection of the total reticle surface magnification error

(5) Adjustment of the coarse focus of the alignment microscope

(6) Adjustment of the microscope reference structure position detection

(7) Loading the wafer

(8) Detection of wafer position

(9) Scanning exposure

(10) Unloading the wafer

(1) Arrangement of the reticle:

After the reticle 6 is loaded onto the reticle stage 7, a microscope (not shown) for the reticle and a reticle driving mechanism (not shown) are used to place the reticle 6 in a predetermined position on the reticle stage 7.

(2) Detecting the reticle position:

After the positioning of the reticle 6 is completed, the light quantity sensor unit 35 arranged on the Y-table 18 is moved into the exposure area of the projection optical system 13 with the movement of the Y-table 18.

With the movement of the scanning table 17, the scanning table-side transmission mark plate 32 is also moved into the exposure area. With this movement of the scanning table 17, the scanning table-side transmission mark plate 32 moves to a position above the light quantity sensor unit 35. This is shown in Fig. 2. In Fig. 2, reference numeral 100 shows the zone of the reticle that is to be subjected to the exposure process. 101 designates an illumination area defined by the illumination system. 102 designates reticle-side transmission marks that are produced on the reticle 6, and 103 designates transmission marks that are produced on the scanning table-side transmission mark plate. 111-114 designate four light quantity detection sections of the light quantity sensor 34.

After the above-described operation, the reticle stage 7 and the scanning stage 17 are positioned to ensure that an image of a particular mark in a central portion in the scanning direction of the reticle-side transmission marks 121-124 (Fig. 3) as formed by the projection optical system 13 is registered with a particular mark in a central portion in the scanning direction of the scanning stage-side transmission marks 125-128 (Fig. 4). Then, the scanning motion is initiated at a scanning speed similar to that during the wafer exposure process.

It should be noted here that in the case where the reticle stage 7 and the scanning stage 17 are driven so that their relative positions are completely aligned with each other, no relative position deviation occurs between the reticle-side transmission mark 102 and the scanning stage-side transmission mark 103 during the scanning movement, so that the amount of light entering the light amount detecting sections 111-114 (Fig. 5) does not change. In view of this, in this embodiment, except for the special marks in the middle sections, the relative position of the reticle-side transmission mark 102 and the scanning stage-side transmission mark 103 is marks 102 and the scanning table-side transmission marks 103 are specially adjusted so that they deviate from the ideal relative position. This is shown in part 8-1 of Fig. 8.

In part 8-1 of Fig. 8, the solid line indicates the ideal relative position, and the dashed line indicates the actual relative position during measurement.

In part 8-1 of Fig. 8, the origin point O is the position of the reticle stage 7 and the scanning stage 17 at which the special marks in the middle portions of the reticle-side transmission marks 102 and the scanning stage-side transmission marks must overlap each other. Special points A and B are those positions at which the periodicity of the reticle-side transmission marks 102 and that of the scanning stage-side transmission marks 103 are shifted by just one period (Lp).

Therefore, when, in the origin point 0, the particular marks in the central portions of the reticle-side transmission marks 102 and the scanning table-side transmission marks 103 completely overlap each other, and when, in the particular points A and B, the periodicity of the reticle-side transmission marks 102 and that of the scanning table-side transmission marks 103 are completely shifted by one period (Lp), then, as shown by a solid line in part 8-2 of Fig. 8, the outputs of the light quantity detecting sections 111-114 in the origin point 0 and in the particular points A and B all become maximum.

Here, in the origin point O, if the special marks in the middle portions of the reticle-side transmission marks 102 and the scanning table-side transmission marks 103 do not completely overlap each other, the vertex of one of the outputs of the light quantity detecting sections 111-114 or the vertices of all of the outputs thereof deviate from the origin point O, as shown by a dashed line in part 8-2 of Fig. 8.

In Fig. 6, dashed lines correspond to the center lines of the reticle-side transmission marks 121 and 122, and solid lines correspond to the center lines of the scanning stage-side transmission marks 125 and 126.

Fig. 7 is an enlarged view of a portion of Fig. 6, and shows a case where the reticle-side transmission mark deviates from the ideal relative position to the scanning table-side transmission mark by an amount "Xeou, Yeou". In this case, the relative position at which the outputs of the upper light quantity sensors 111 and 112 become largest deviates from the ideal relative position by L₁ and L₂, respectively.

In this embodiment, each pass mark has an inclination of 45 degrees with respect to the scanning direction. This results in:

Xeou + Yeou = L1... (1)

Xeou - Yeou = L2... (2)

It follows:

Xeou = 1/2 * (L 1 + L 2 )... (3)

Yeou = 1/2 · (L1 - L2 )... (4)

Simultaneously with the above, the measurement is carried out with respect to another pair of reticle-side transmission marks 123 and 124 and another pair of scanning-stage-side transmission marks 127 and 128. When the reticle-side transmission marks deviate from the ideal relative position to the scanning-stage-side transmission marks by L₃ and L₄, respectively, the following relationships exist:

Xeou = 1/2 (L3 + L4)... (5)

Yeou = 1/2 · (L3 - L4 )... (6)

Here, if the distance in the Y direction between the upper transmission mark 125 (126) and the lower transmission mark 127 (128) is denoted by D, the deviation from the ideal position of the reticle image is denoted by (Xeo, Yeo), the angular deviation is denoted by θeo and the center displacement magnification error is denoted by Meo, then the equations of Xeou', Yeou, Xeod and Yeod result in

Xeo = 1 /2 (Xeou + Xeod)... (7)

Yeo = 1/2 · (Yeou + Yeod)... (8)

θeo = arctan{(Xeou - Xeod)/D}... (9)

Meo = (Yeou - Yeod)/D... (10)

The measurements and calculations described above specify the deviation (Xeo, Yeo) from the ideal position of the reticle image as well as the angular deviation θeo and the center magnification error Meo.

It should be noted that L₁-L₄ is easily determined from the relative position with which the light quantity detecting sections 111-114 give maximum levels.

The manner of determining L₁ will be explained below with reference to part 8-1 and part 8-2 of Fig. 8.

In part 8-2 of Fig. 8, L�0 shows the distance to the point at which the light quantity detecting section 111 has a maximum. If the distance on the reticle side by which the one period of the structure is shifted is denoted by La and the distance of the one period of the structure is denoted by Lp, then:

L&sub1; = Lp · (Loo'/La)... (11)

In a similar manner to that described above, L₂ - L₄ can be easily determined by measurements and calculations.

In this embodiment, except for the special marks in the central portions, the relative position of the reticle-side transmission marks 102 and the scanning table-side transmission marks 103 is specifically set to deviate from the ideal relative position as described above. Here, the distances from the origin point O to the special points A and B are La and Lb, respectively, each on the order of 10 mm. In comparison, a Pe interval of the scanning stage-side transmission mark is on the order of a few micrometers. Therefore, between the reticle position detecting operation and the ongoing exposure operation, the spotting, the effective light source and the posture can all be considered to be substantially unchanged.

(3) Detection of the image plane of the reticle:

After measuring the deviations Xeo, Yeo from the ideal position of the reticle image as well as the angular deviation θeo and the magnification error Meo as described above, corrections are made. With respect to the deviation Xeo, Yeo from the ideal relative position, their correction is made by changing the relative position on the scanning stage 17 side. The angular deviation θeo is made by performing θ rotation of the reticle on the reticle stage 7 side. The center magnification error Meo is corrected using the magnification adjustment mechanism 11.

Thereafter, the scanning movement is repeatedly carried out while detecting the correspondence between the reticle-side transmission marks 102 and the scanning table-side transmission marks 103 and the outputs of the light quantity detecting sections 111-114. Here, for each scanning movement, the position of the scanning table-side transmission marks 103 is changed by means of the θZ table 16 in the focus direction of the projection optical system 13.

Since the position of the scanning table side transmission marks 103 changes in the focus direction of the projection system 13, the outputs of the light quantity detecting sections 111-114 change as shown in part 8-3 of Fig. 8.

Here, the position of the scanning table-side transmission mark in the Z direction, in which the outputs of the light quantity detecting sections 111-114 become maximum, corresponds to the image plane position of the reticle.

From the position in the Z direction at which the outputs of the light quantity detecting sections 111 and 112 become maximum and from the position in the Z direction at which the outputs of the light detecting sections 113 and 114 become maximum, the position and inclination of the image plane of the reticle 6 with respect to the scanning position, in particular, the ideal image plane can be determined.

This ideal image plane is to be reproduced during the subsequent wafer exposure process in a time relationship with the scanning motion and relative to the wafer surface. Finally, after the measurements, the scanning table side transmission mark plate 32 is moved under the projection system 13 and in a time relationship with the scanning motion, the ideal image plane is reproduced using the scanning table side transmission mark plate 32. The ideal image plane position as determined in this operation based on the tilt and focus detection system 25 is stored in a memory.

(4) Detection of the total reticle surface magnification error:

After measuring and correcting the deviations Xeo, Yeo from the ideal position of the reticle 6 as well as the angular deviation θeo and the magnification error Meo and after measuring the ideal image plane of the reticle with respect to the scanning position, the scanning movement is carried out while again making the correspondence between the reticle stage side transmission marks 102 and the scanning stage side transmission marks 103 to correct all the errors, and the outputs of the light quantity detecting sections 111-114 are measured.

At this point, it is checked whether the correction of the position of the special mark in the middle section of the pass marks is completed. At the same time, it is checked whether the output at the special points A and B The light quantity detection sections 111-114 are maximized.

With respect to the particular points A and B, when one of the outputs of the light quantity detecting sections 111-114 becomes maximum at a point other than the particular points A and B, the following process is carried out in a similar manner to the case of detecting the reticle position (point (2)): That is, the deviation (Xea, Yea) from the ideal position of the reticle image at the position A as well as the angular deviation θea and the magnification error Mea and also the deviation (Xeb, Yeb) from the ideal position of the reticle at the position B as well as the angular deviation θeb and the magnification error are detected. From the results and based on Xeo, Yeo and Meo at the origin point 0, while using the positional deviations, the angular deviations and the magnification errors in the distance from the origin point 0 to the position A and in the distance from the origin point O to the position B as an approximate function of the position "r" of the reticle-side transmission marks in the scanning direction, the values Xe(r), Ye(r), θe(r) and Me(r) are determined. Regarding 4(r), the correction is made by changing the relative position of the transmission marks in a time relationship with the scanning movement. Regarding Ye(r), the correction is made by changing the position of the Y table in a time relationship with the scanning movement. Regarding θe(r), the correction is made by performing the rotation on the wafer side in a time relationship with the scanning movement. Regarding Me(r), the correction is made using the magnification adjustment mechanism 11 in a time relationship with the scanning movement. All deviations are correctable in this way.

Based on the correction values Xe(r), Ye(r), θe(r) and Me(r), it is determined how to correct or operate the relative position of the scanning stage, the position of the Y stage, the rotation on the wafer side, the magnification adjustment mechanism and the image plane position, respectively.

The data to be used in such correction and operation is correction data for the reticle as viewed from the scanning stage side pass marks. Hereinafter, it is also referred to as "correction data for the reticle". Of course, this correction data of the reticle is the function of the scanning direction position of the reticle.

(5) Adjustment of the coarse focus of the alignment microscope:

While the scanning stage-side transmission mark 103 is used as the original focus position determined as described above, its arrangement is carried out under the alignment microscope.

Here, an objective lens of the alignment microscope is moved along the optical axis direction so that the transmission mark is imaged in the TV camera 31. This is to reduce as much as possible the movement in the focus direction after the wafer that has been aligned is moved and placed under the projection optical system.

(6) Adjustment of the microscope reference structure position detection:

In the exposure apparatus of this embodiment, the projection system 13, the alignment microscope 30 and the light quantity sensor unit 35 are arranged along the same Y axis, as shown in Fig. 9. Thereby, with the movement of the Y table 18, the light quantity sensor unit 35 can be positioned under the alignment microscope 30, and with the movement of the scanning table 17, the scanning table side transmission mark plate 32 can be positioned above the light quantity sensor unit 35.

The alignment microscope 30 has a structure as shown in Fig. 10, wherein the reference numeral 150 designates a reference structure delimited within the alignment microscope 30. ture. 151 denotes an objective lens, and 152-155 denote optical lenses. 156 and 157 denote half mirrors, and 158 and 159 denote optical fibers for guiding the illumination light from a light source (not shown). As shown in Fig. 11, reticle-associated markings 161 and 162 are also arranged within the reference mark 150, which provide a positional reference of the alignment microscope.

The positioning of the scanning table side transmission mark plate 32 in the scanning direction is carried out so as to ensure that the projected images of the reticle-associated marks 161 and 162 overlap with the particular marks of the transmission marks 125 and 126 on the scanning table side transmission mark plate 32. Then, during the minute change of the position in the scanning direction over the thus determined position and also during the change of the position in the focus direction, the outputs of the light quantity detecting sections 111 and 112 are detected.

With this operation, the position of the projected image of the reticle-associated marks 161 and 162 and the image plane are detected in a similar manner to the case of detecting the position of the projected image of the reticle-side transmission marks 102 and detecting the image plane. It differs from the case of detecting the position of the projected image of the reticle-side transmission marks 102 and detecting the image plane in the following two points:

(i) The measurement is carried out in the steady state, and

(ii) Only two light quantity detection sections are used.

With the operations described above, the position of the projected image of the reticle-side transmission marks, the position of the projected image of the reticle-side ordered marks 161 and 162 with respect to the image plane and the relative position of the image plane.

This relative position is referred to as the "base line" between the optical projection system 13 and the alignment microscope 30 .

The process described in points (1)-(6) can be executed automatically in response to an operator entering a system calibration command before starting or during the wafer process.

(7) Loading the wafer:

Referring to Fig. 1, the exposure apparatus of this embodiment carries out wafer loading as follows. In response to the input of a wafer process start command, a wafer is automatically taken out from a wafer carrier within a wafer transport system (not shown). In a mechanical pre-adjustment section within the wafer transport system, the wafer is placed on an X-Y table. Using the wafer edge detection function, the outer edge shape of the wafer as well as its orientation plane are detected. Then, using an X-Y table, the orientation plane of the wafer is adjusted in a predetermined direction and the center position of the wafer is determined. Thereafter, using a focus detection function, the level (height) of the surface of the wafer is detected.

Thereafter, a pre-alignment mark of the wafer is placed under a microscope arranged on the top of the pre-alignment system so that the position of the pre-alignment mark is measured. Then, the X-Y-6 table is driven so that the position of the pattern of the wafer is placed in a predetermined positional relationship with a particular reference position of the transport system.

Finally, the wafer thickness data generated based on the wafer level detection is supplied to the central processing unit (CPU) 70 of the exposure apparatus.

In response to the receipt of this data, the CPU 70 of the exposure apparatus activates the Z drive mechanism of the θZ tilting table to change the level (height) of the wafer support so that when the wafer is placed thereon, the wafer surface is positioned substantially at the focus position of the projection system and the alignment microscope.

After the above-described operation, the transport system moves the wafer from the X-Y θ table of the transport system to the wafer holder of the exposure apparatus using a loading hand.

(8) Detection of wafer position:

When the wafer 14 is loaded on the wafer support device 15, the Y-table 18 and the scanning table 17 are operated to move the wafer 14 under the projection system 13 when the level measurement of the entire wafer surface is carried out using the focus detection system 25 and 26.

Then, the predetermined chip regions of the wafer are moved one after another under the alignment microscope, and the position measurement is carried out on alignment marks formed in each chip region.

The position measurements on the alignment marks are carried out by projecting the transmission mark portion 160 and the reticle-associated marks 161 and 162 of the reference mark 150 within the alignment microscope 30. Here, the light passing through the transmission mark portion 160 is used to illuminate the alignment marks of the wafer 14. Thus, the reticle-associated Marks 161 and 162 and the alignment marks of the wafer 14 are projected to the CCD camera 31.

This measurement determines the relative position of each chip of the wafer with respect to the reticle-associated markings 161 and 162 within the alignment microscope as well as the magnification in the scanning direction of each chip and in the direction perpendicular to the scanning direction.

In the above-described operation, it is determined how to correct and operate the relative position of the scanning table, the Y-table position, and the magnification adjustment mechanism in a timing relationship with the scanning movement during the exposure process of each chip of the wafer.

The data to be used in such correction and operation is correction data for the wafer as viewed from the reticle-associated marks 161 and 162 in the alignment microscope 30. These are also referred to hereinafter as "correction data for the wafer".

(9) Scanning exposure:

Based on the correction data for the reticle, the baseline and the correction data for the wafer as described above, the reticle and the entire surface of each chip of the wafer can be precisely aligned in registration and focus during the scanning exposure process.

After completion of the measurement of the correction data for the wafer, a first chip of the wafer 14 is moved under the projection system 13 based on the correction data for the reticle, the base line and the correction data for the wafer. While obtaining the ideal relative position of the particular chip to the reticle and obtaining the ideal image plane position using the correction data for the reticle and the correction data for the wafer and additionally while performing the mutual magnification correction, the reticle table 7 and the scanning table 17 initiate the actual scanning exposure operation.

In the exposure apparatus of this embodiment, the exposure amount of the wafer 14 is preset. In order to realize this exposure amount, it is necessary to detect the light energy by a pulse of the excimer laser device 1, which is the light source.

In this embodiment, before the start of the wafer process, the excimer laser device is excited, and the illuminance on the reticle surface, which corresponds to the illuminance on the wafer surface, is measured using the photosensor 4. Based on the measurement, the number of necessary exposure light pulses required for the entire area on the wafer is calculated.

From the necessary number of exposure light pulses calculated in this way, the CPU 70 sets the excitation controller 40 to the scanning table positions at which the excimer laser device is to be excited before starting the scanning exposure. During the scanning exposure operation, the exposure controller 40 constantly monitors the position of the scanning table 17, and each time the scanning table 17 reaches a preset scanning table position at which the laser device is to be excited, it applies an excitation command signal to the excimer laser device 1, thereby exciting the excimer laser device to generate pulse light.

The above operation completes the exposure of one chip. Similar operations are performed for all remaining chips on the same wafer.

(10) Unloading the wafer:

After the exposure operations of all chips are completed, the wafer 14 is removed by means of the Y-table 18 and the touch table 17 into the wafer unloading position. Then, the wafer 14 is unloaded from the wafer receiving device 15 using an unloading hand (not shown) of the transport system.

[Variations]

The embodiment of the present invention described above can be modified as follows.

(1) A variety of wafer-side transmission marks and light quantity sensors:

A plurality of wafer-side transmission marks and a plurality of light quantity sensors can be arranged around the wafer holding device. This enables the precise correction of a positional difference.

(2) Test reticles:

There are cases where it is practically impossible to form a number of reticle-side transmission marks on an actual reticle used for manufacturing the actual semiconductor devices, and this may be attributed to the relationship with alignment structures or other structures. To cope with this, a trial reticle may be produced in which a number of reticle-side transmission marks are present in order to periodically carry out the precise correction. An actual reticle can be formed with a small number of reticle-side transmission marks in this way.

(3) One-piece construction of transmission mark and light quantity sensor:

A large number of tilting transmission marks may be arranged on the reticle and the scanning table as in the previous embodiment, and a light quantity sensor may be fixedly arranged under the scanning table side transmission marks This enables the scanning table side transmission marks to be uniformly imaged on the light receiving surface of the light quantity sensor in the same focus state. It also allows the reticle image plane position to be detected with high accuracy. In this method, however, it is necessary to arrange a long light quantity sensor having uniform detection sensitivity under the scanning table side transmission marks. Thus, when a high frequency pulse light source such as an excimer laser device is used as a light source, it is generally difficult to satisfy the requirement of uniformity of sensitivity by the sensor alone. As a practical example of this, the amount of light entering the scanning table side transmission marks is made uniform while the reticle is kept in a stationary state in the exposure apparatus. While this state is maintained, a detection unit having an integral structure of the scanning table side transmission marks and the light quantity sensor is moved. Changes in the output of the light quantity sensor during this movement are stored as calibration data, which can be used for calibrating the output data of the light quantity sensor during detection of the position of an actual reticle or detection of the image plane. However, when the light energy from the light source does not have high stability, it is necessary to measure the light energy of the light source using a reticle surface illumination detection system as described with reference to the previous embodiment, thereby correcting the calibration data.

Next, an embodiment of the method for manufacturing a device using an exposure apparatus described above will be explained.

Fig. 13 shows a flow chart of the sequence of manufacturing a micro device such as a semiconductor chip (e.g. LSI-IC), a liquid crystal panel, a CCD, a thin layer magnetic head or a micromachine. Step 1 is a design process for designing the circuit of a semiconductor device. Step 2 is a process for making a mask based on the circuit pattern design. Step 3 is a process for making a wafer using a material such as silicon.

Step 4 is a wafer process, which is called a pre-process, using the mask and wafer thus produced, and the circuits are practically produced on the wafer by a lithographic process. The step S following this is an assembly step, which is called a post-process, in which the wafer produced in step 4 is formed into semiconductor chips. This step includes assembly (singling and bonding) and encapsulation (chip sealing). Step 6 is a test step in which the functional test, durability test, etc. of the semiconductor devices produced in step S are carried out. With these processes, the semiconductor devices are completed and they are sent for shipment (step 7).

Fig. 14 is a flow chart showing the details of the wafer process. Step 11 is an oxidation process for oxidizing the surface of a wafer. Step 12 is a CVD process for forming an insulating film on the wafer surface. Step 13 is an electrode forming process for forming electrodes on the wafer by vapor deposition. Step 14 is an ion implantation process for implanting ions into the wafer. Step 15 is a resist process for applying a resist (photosensitive material) to the wafer. Step 16 is an exposure process for copying by exposing the circuit pattern of the mask to the wafer by the above-described exposure apparatus. Step 17 is a development process for developing the exposed wafer. Step 18 is an etching process for removing the portions other than the developed resist image. Step 19 is a resist separation process for separating the resist material remaining on the wafer after which has been subjected to the etching process. By repeating these processes, overlapping circuit structures are created on the wafer.

Although the invention has been described with reference to the embodiments, it is not limited to the details set out, but modifications or variations are possible which are to be considered as falling within the scope of the invention, which is defined in the following claims.

Claims (14)

1. A scanning exposure apparatus comprising: - a first movable table (7) for supporting a first object (6) which is movable in a predetermined one-dimensional direction, - a second movable table (17) for supporting a second object (14) which is movable in a predetermined one-dimensional direction, - a projection system (13) for projecting a structure of the first object through an optical projection system onto the second object during the scanning movement of the first and second movable tables in a time relationship with respect to the optical projection system, - a first mark (102) formed on the first object and having a plurality of markings regularly arranged along a scanning direction, - a reference plate (32) fixedly arranged on the second movable table and having a second mark (103) with a plurality of markings regularly arranged along the scanning direction, - a third movable table (18) for supporting the second movable table, which is movable in a direction (Y) different from the direction of movement (X) of the second table, - a photodetecting device (34) fixedly arranged on the third movable table, and - a control device having a first function for moving the second and third movable tables in a manner to arrange the reference plate and the photodetecting device at a position of an image of the first mark projected by the projection optical system, and having a second function for detecting the image of the first mark by the second mark using the photodetecting device while the first and the second movable table can be moved in a time relationship with respect to the optical projection system. 2. An apparatus according to claim 1, wherein the second movable table has a sliding device which is sliding in a direction of an optical axis of the projection optical system, and wherein the control means is operable to operate the sliding device to change the position of the reference plate with respect to the direction of the optical axis so that the photodetecting means detects the image of the first mark through the second mark. 3. Apparatus according to claim 1, wherein each of the first and second marks comprises a marking having a plurality of periodically regularly arranged markings. 4. The apparatus of claim 1, wherein each of the first and second marks comprises a mark having a plurality of marks having different inclinations. 5. An apparatus according to claim 1, wherein said control means determines the position at which said first mark is to be projected onto said second mark by said projection optical system, based on a signal in response to detection by said photodetecting means of the image of said first mark by said second mark and based on the positions of said first and second movable tables at the time of detection of said signal. 6. An apparatus according to claim 2, wherein said control means determines the position in the optical axis direction of said projection optical system at which said first mark is to be imaged by said projection optical system based on a signal in response to detection of the image of said first mark through said second mark by said photodetecting means and based on the position of said second movable table upon detection of said signal. 7. An exposure method usable with a scanning exposure apparatus for projecting a structure of a first object through an optical projection system onto a second object during scanning movement of the first and second objects in a time relationship with respect to the optical projection system, the method comprising the steps of: - providing a first mark with a plurality of marks on the first object, which are regularly arranged along a scanning direction, - providing a reference plate fixedly mounted on a movable table for supporting the second object and having a second mark with a plurality of markings regularly arranged along the scanning direction, - arranging a photodetecting device in a position into which an image of the first mark is or is to be projected by the optical projection system, and - capturing the image of the first mark through the second mark using the photodetecting device during the scanning movement of the first object and the reference plate in a time relationship with respect to the optical projection system. 8. A method according to claim 7, wherein in the detecting step, the image of the first mark is detected by the second mark using the photodetecting means while changing the position of the reference plate with respect to the direction of the optical axis of the projection optical system. 9. The method according to claim 8, further comprising determining the position into which the first mark is or is to be projected onto the second mark by the projection optical system based on the positions of the first and second marks at the time when the image of the first mark is captured by the second mark using the photo-capturing device. 10. The method according to claim 8, further comprising determining the position with respect to the optical axis direction in which the first mark is imaged by the optical projection system based on a signal in response to the detection of the image of the first mark by the second mark using the photodetecting means and based on the position of the reference plate with respect to the optical axis direction at a time of detection of the signal. 11. A method of manufacturing a device usable with a scanning exposure apparatus for projecting a pattern of a reticle through an optical projection system onto a wafer while scanning the reticle and the wafer in a time relationship with respect to the optical projection system, the method comprising the steps of: - providing a reticle mark with a plurality of markings arranged regularly along a scanning direction on the reticle, - providing a reference plate which is fixedly arranged on a movable table for supporting the wafer and has a wafer mark with a plurality of markings regularly arranged along the scanning direction, - arranging a photodetecting device in a position into which an image of the reticle mark is or is to be projected by the optical projection system, and - capturing the image of the reticle mark through the wafer mark using the photodetecting device during the scanning movement of the reticle and the reference plate in a time relationship with respect to the optical projection system. 12. A method for manufacturing a semiconductor device, which comprises the steps according to any one of claims 7 to 10 and the step of projecting the structure through the first object with a mask onto a second object with a semiconductor wafer. 13. The method of claim 12, wherein the mask and the wafer are relatively moved in a scanning manner during projection of the structure. 14. A method according to claim 12 or claim 13, comprising the steps of developing the wafer after exposing it to the projected pattern and etching the wafer to remove the portions other than the developed areas.