JP2000036451A - Exposure method and lithography system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable a superposition exposure process of high superposition accuracy to be carried out using projection exposure systems. SOLUTION: This exposure method is carried out in a manner in which a projection exposure system that is ensured of a high superposition accuracy is selected, knowing the deformation of the transferred images of layers and taking the deformation controlling capacities of projection exposure systems 1101 to 110N into consideration, on the basis of an exposure history which indicates that photoreceptive substrates which are to be subjected to superposition exposure and possessed of at least one or more exposed photoreceptive layers are exposed to light as projection images are deformed by the use of the projection exposure systems 1101 to 110N. The photoreceptive substrates are subjected to a superposition exposure process using the selected projection exposure system. Therefore, a superposition exposure process of high superposition accuracy can be carried out using the projection exposure systems 1101 to 110N.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure method and a lithography system, and more particularly, to a lithography system used in a lithography process when manufacturing a micro device such as a semiconductor device or a liquid crystal display device. And an exposure method.

[0002]

2. Description of the Related Art Conventionally, in a lithography process for manufacturing a semiconductor device, a liquid crystal display device, or the like, a pattern formed on a mask or a reticle (hereinafter, collectively referred to as a “reticle”) is resisted through a projection optical system. There is used a projection exposure apparatus that transfers a wafer onto a substrate such as a wafer or a glass plate (hereinafter, appropriately referred to as a “sensitive substrate or wafer”) coated with the like. In order to improve mass productivity, it is common practice to prepare a plurality of projection exposure apparatuses and construct a lithography system in which these projection exposure apparatuses are managed by a host computer.

Here, in manufacturing a semiconductor device or the like, different circuit patterns are formed by stacking on a sensitive substrate in a number of layers, but in order to enhance mass productivity, each circuit layer on one substrate (layer) is formed. It is necessary to transfer the circuit pattern using a different projection exposure apparatus. Therefore, it is necessary to match the distortion of the transferred image between the projection exposure apparatuses in order to secure the overlay accuracy.

In a conventional lithography system, in order to secure the overlay accuracy by reducing the machine difference of the transferred image, the distortion of the transferred image by each projection exposure apparatus is brought as close as possible to the ideal value when each projection exposure apparatus is carried in. The respective projection optical systems and the like are adjusted as described above, or one of the plurality of projection exposure apparatuses is defined as a reference unit, and the other projection exposure apparatuses are controlled so that the same distortion as the transfer image distortion in this reference unit occurs. The projection optical system was adjusted.

As a method of adjusting the distortion of the transferred image of the projection exposure apparatus, for example, in a collective exposure apparatus, a part of lens elements of a projection optical system is driven in an optical axis direction or a plane orthogonal to the optical axis. Japanese Patent Laid-Open No. 4-127 discloses a method and an apparatus for generating an image distortion by inclining the
No. 514, etc. Further, as an example in the scanning type exposure apparatus, the magnification of the projection optical system is continuously changed during the scanning exposure, the relative angle of the reticle and the substrate in the scanning direction is offset, or the relative angle is continuously changed. Japanese Patent Application Laid-Open No. 7-579 discloses a method and an apparatus for distorting an image formed after scanning by a changing method.
No. 91, for example.

[0006]

In the above-described conventional lithography system, the distortion of the transferred image by each projection exposure apparatus is smaller than the distortion of the reference transferred image, that is, the distortion of the ideal value or the distortion of the reference unit. Are small, but a difference of about the sum of the differences may exist between the projection exposure apparatuses. Further, the transfer characteristics of the projection exposure apparatus change with time, and the machine difference of the distortion of the transfer image between the projection exposure apparatuses may increase with time.

For this reason, in the transfer image matching using the adjustment value of the transfer image distortion at the time of introduction of each projection exposure apparatus, which has been performed in the conventional lithography system, the miniaturization of a circuit pattern, which has been increasing in recent years, has been increasing. It is becoming difficult to respond to a request for improvement in overlay accuracy accompanying this.

The present invention has been made under such circumstances, and an object of the present invention is to provide an exposure method and a lithography system capable of performing overlay exposure with high overlay accuracy while using a plurality of projection exposure apparatuses. To provide.

[0009]

According to an exposure method of the present invention, a plurality of projection exposure apparatuses (110 _{1 to} 110 _N ) each including at least one projection exposure apparatus capable of adjusting a distortion of a projected image are used for a sensitive substrate (W). In an exposure method for exposing the photosensitive substrate (W) in a multi-layer manner, the exposure history of the sensitive substrate (W) and the plurality of projection exposure devices (110 ₁ ) are superimposed upon exposure of the sensitive substrate (W) to which at least one layer has been exposed. １１０110 _N ) A projection exposure apparatus for superposing and exposing the sensitive substrate is selected from the plurality of projection exposure apparatuses based on the respective distortion adjustment capabilities.

According to this, when performing overlay exposure on a sensitive substrate on which at least one or more layers have been exposed, for example, a lot of sensitive substrates, the sensitive substrate to be subjected to overlay exposure is determined by what type of projection exposure has been performed. From the exposure history indicating the state of exposure by the device,
Know the distortion of the transferred image in each layer, and then select a projection exposure apparatus that can ensure the overlay accuracy with high accuracy in consideration of the distortion adjustment capability of each projection exposure apparatus. Then, the superposed exposure of the sensitive substrate is performed using the selected projection exposure apparatus. Therefore, overlay exposure can be performed with high overlay accuracy while using a plurality of projection exposure apparatuses.

Here, the distortion of the projected image at the time of exposure of the projection exposure apparatus that has exposed each layer greatly contributes to the distortion of the transferred image of each layer that has already been exposed. Therefore, it is desirable that the above-mentioned exposure history includes distortion information of a projected image at the time of exposure of each layer that has already been exposed.

When selecting a projection exposure apparatus for performing the overlay exposure, an error in the overlay of a projection image by the projection exposure apparatus that has exposed the sensitive substrate to be subjected to the overlay exposure for each of the projection exposure apparatuses. Find the residual error when performing distortion adjustment to minimize it,
By selecting a projection exposure apparatus that performs overlay exposure based on the value of each residual error, an appropriate projection exposure apparatus can be selected. In such a case, the distortion adjustment that causes the residual error of the selected projection exposure apparatus is performed, and the overlay exposure is performed.

In selecting a projection exposure apparatus,
Further considering the drawing error of the pattern formed on the mask,
By comprehensively calculating the error of the transferred image in the actual pattern transfer, a more appropriate projection exposure apparatus can be selected. Furthermore, a projection exposure apparatus that performs the overlay exposure by comprehensively judging the operating status of each projection exposure apparatus at the time of selection of the projection exposure apparatus and the matching accuracy with the error of the transferred image in the already performed exposure. By selecting, it is possible to improve mass productivity while securing high overlay accuracy.

A lithography system according to the present invention includes: a plurality of projection exposure apparatuses (110 _{1 to} 110 _N ) each including at least one projection exposure apparatus capable of adjusting a distortion of a projected image; In superposing exposure of the sensitive substrate (W), the sensitive substrate is superimposed based on the exposure history of the sensitive substrate (W) and the distortion adjustment capability of each of the plurality of projection exposure apparatuses (110 _{1 to} 110 _N ). A determination device (130, 140, 160) for selecting a projection exposure apparatus to be exposed from the plurality of projection exposure apparatuses.

According to this, upon superposition exposure,
The sensitive device to be subjected to the overlay exposure is
A projection exposure apparatus that can ensure high overlay accuracy based on an exposure history indicating what kind of state the projection exposure apparatus has been exposed to and the distortion adjustment capability of each projection exposure apparatus. Select That is, since the overlay exposure is performed on the sensitive substrate using the above-described exposure method of the present invention, the overlay exposure can be performed with high overlay accuracy while using a plurality of projection exposure apparatuses.

Here, the judging device includes a process management device for managing the operation status of the plurality of projection exposure devices; and a distortion management device for managing the operation history of the plurality of projection exposure devices and the distortion setting of the projected image. It is possible to configure.

In such a case, the distortion management apparatus calculates an optimum distortion set value for the exposure of the sensitive substrate for the projection exposure apparatus capable of adjusting the distortion of the projected image based on the exposure history of the sensitive substrate. It is appropriate for the system to share the processing and to contribute to the selection of the projection exposure apparatus that performs the overlay exposure, as the load sharing of the system. In this system configuration, for example, when exposing a sensitive substrate, for a sensitive substrate to be subjected to overlay exposure specified by a process management apparatus, distortion management is performed based on the exposure history and the distortion adjustment capability of each projection exposure apparatus. The apparatus determines at least one candidate for a projection exposure apparatus that performs overlay exposure from the viewpoint of overlay accuracy. Then, the process management apparatus can execute the exposure method of selecting one projection exposure apparatus from the determined projection exposure apparatuses based on the determined operation state of the projection exposure apparatus. According to this exposure method, it is possible to improve mass productivity while securing high overlay accuracy.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIG.
This will be described with reference to FIG.

FIG. 1 schematically shows the configuration of a lithography system 100 according to one embodiment. The lithography system 100 includes N projection exposure apparatuses 110 ₁
To 110 _N , machine controllers (MC) 120 _{1 to} 12 provided for each projection exposure apparatus 110 _i (i = 1 to N).
0 _N , image distortion calculation device 130, centralized information server 140,
It comprises a terminal server 150 and a host computer 160 as a process management device. Here, the projection exposure device 110 _i , the MC 120 _i , the image distortion calculation device 13
0, centralized information server 140, and terminal server 15
0 is connected to a local area network (LAN) 170, and the host computer 160 is connected to the LAN 170 via the terminal server 150. That is, in the hardware configuration, a communication path among the projection exposure apparatus 110 _i , the MC 120 _i , the image distortion calculation apparatus 130, the centralized information server 140, the terminal server 150, and the host computer 160 is secured. The actual communication between the components in the system will be described later.

Each of the projection exposure apparatuses 110 _{1 to} 110 _N may be a step-and-repeat type projection exposure apparatus (so-called “stepper”), or may be a step-and-scan type projection exposure apparatus. (Less than,
“Scanning exposure apparatus”). However, at least one of the projection exposure apparatuses 110 _{1 to} 110 _N needs to have a capability of adjusting the distortion of the projected image. In the following description, the projection exposure apparatuses 110 ₁ to 110 ₁
It is assumed that all of 10 _N are scanning exposure apparatuses having a capability of adjusting the distortion of a projected image.

FIG. 2 shows such a projection exposure apparatus 110.₁~
110_NOne of the projection exposure apparatuses 110₁Schematic structure of
The results are shown. Note that other projection exposure apparatuses 110_Two~
110 _NIs configured similarly to the projection exposure apparatus. Shown in FIG.
Exposure values 110₁Is a lighting IOP,
Reticle stage for holding reticle R as mask
RST, projection optical system PL, wafer W as a sensitive substrate
A wafer stage WST and the like to be mounted are provided.

The illumination system IOP includes an illuminance uniforming optical system including a light source, a fly-eye lens, a relay lens, a variable ND filter, a reticle blind, a dichroic mirror, and the like (all not shown). . The configuration of such an illumination system is described in, for example,
No. 12433.

In this illumination system IOP, a slit-shaped illumination area defined by a reticle blind on a reticle R on which a circuit pattern or the like is drawn is illuminated by illumination light IL with substantially uniform illuminance.

A reticle R is fixed on the reticle stage RST by, for example, vacuum suction. Here, reticle stage RST is driven by an optical axis of an illumination optical system (an optical axis of a projection optical system PL to be described later) for positioning of reticle R by a reticle stage driving unit (not shown) composed of a magnetic levitation type two-dimensional linear actuator. It can be driven minutely in an XY plane perpendicular to AX) and can be driven at a scanning speed designated in a predetermined scanning direction (here, Y direction). Further, in the present embodiment, the magnetic levitation type two-dimensional linear actuator includes a Z drive coil in addition to the X drive coil and the Y drive coil, and thus can be minutely driven in the Z direction.

The position of the reticle stage RST within the stage movement plane is constantly detected by a reticle laser interferometer (hereinafter referred to as a "reticle interferometer") 16 through a movable mirror 15 at a resolution of, for example, about 0.5 to 1 nm. Is done. Position information of reticle stage RST from reticle interferometer 16 is sent to stage control system 19, and
Reference numeral 9 drives the reticle stage RST via a reticle stage driving unit (not shown) based on the position information of the reticle stage RST.

The projection optical system PL is disposed below the reticle stage RST in FIG. 2, and the direction of the optical axis AX is the Z-axis direction. In this case, the optical axis AX is set so that the optical arrangement is telecentric on both sides. A plurality of lens elements 27, 29, 3 arranged at predetermined intervals along
, And these lens elements 27, 2
The lens barrel 32 includes 9, 30, 31,.... The projection optical system PL is a reduction optical system having a predetermined projection magnification, for example, 1/5 (or 1/4). For this reason, when the illumination area of the reticle R is illuminated by the illumination light IL from the illumination system IOP, the illumination light IL that has passed through the reticle R causes the circuit pattern of the reticle R in the illumination area to pass through the projection optical system PL. Is formed on a wafer W having a surface coated with a resist (photosensitive agent). This projection exposure apparatus 110
_{In FIG. 1} , an imaging characteristic correction device for correcting distortion (including magnification) of a projection image by the projection optical system PL is provided (this will be described in detail later).

The wafer stage WST is arranged below the projection optical system PL in FIG. 2, and a wafer holder 9 is held on the wafer stage WST. The wafer W is vacuum-sucked on the wafer holder 9. The wafer holder 9 can be tilted in any direction with respect to the best image forming plane of the projection optical system PL by a driving unit (not shown), and can be finely moved in the optical axis AX direction (Z direction) of the projection optical system PL. ing. Further, the wafer holder 9 can also rotate around the optical axis AX.

The wafer stage WST moves not only in the scanning direction (Y direction) but also in the scanning direction so that a plurality of shot areas on the wafer W can be positioned in the exposure area IA conjugate with the illumination area IAR. Steps for repeating the operation of scanning (scanning) exposing each shot area on the wafer W and the operation of moving to the exposure start position of the next shot, which are configured to be movable also in the vertical direction (X direction). Perform an AND scan operation. The wafer stage WST is driven in the XY two-dimensional directions by a wafer stage driving unit (not shown) such as a motor.

The position of wafer stage WST in the XY plane is constantly detected by wafer laser interferometer 18 via movable mirror 17 at a resolution of, for example, about 0.5 to 1 nm. The position information (or speed information) of wafer stage WST is sent to stage control system 19, and stage control system 19 controls wafer stage WST based on this position information (or speed information).

The projection exposure apparatus 11 configured as described above
At 0 ₁ , the wafer W and the reticle R are oppositely directed along the scanning direction (Y direction) in a state where the slit-shaped illumination area (center is substantially coincident with the optical axis AX) is illuminated by the illumination light IL. Then, they move synchronously at a speed ratio corresponding to the projection magnification. By this scanning exposure, the pattern of the pattern area of the reticle R is reduced and transferred onto the shot area on the wafer W.

On the side of the projection optical system PL, an off-axis type alignment microscope for detecting the position of an alignment mark (wafer mark) attached to each shot area on the wafer W, for example, an image processing type microscope. An image alignment sensor 8 is provided. Main controller 50
Prior to the above-described scanning exposure, the array coordinates of the shot area on the wafer W are calculated based on the measured position of the wafer mark by, for example, a statistical operation disclosed in Japanese Patent Application Laid-Open No. 61-44429.

Further, the projection exposure apparatus 110 ₁ and supplies from an oblique direction the imaging light beam for forming a plurality of slit images toward the best imaging plane of the projection optical system PL with respect to the optical axis AX direction Irradiation optical system 13 and wafer W of the image forming light beam
An oblique incidence type multi-point focal point position detection system comprising a light receiving optical system 14 for receiving each reflected light beam on the surface of the lens through a slit is fixed to a support (not shown) supporting the projection optical system PL. I have. This multipoint focal position detection system (1
As the components 3 and 14), for example, those having the same configuration as that disclosed in JP-A-5-190423 are used.
The stage control system 19 drives the wafer holder 9 in the Z direction and the tilt direction based on the wafer position information.

Next, an image forming characteristic correcting device for correcting the image forming characteristic of the projection system PL will be described. The imaging characteristic correction device, change the atmospheric pressure, as well as compensate for changes in the imaging characteristics of the projection optical system PL ₁ itself due to the illumination light absorption, etc., the distortion of the exposure shots before layer on the wafer W (shot area) In addition, it has a function of distorting the projected image of the pattern of the reticle R. The imaging characteristics of the projection optical system PL include a focal position, a curvature of field, distortion, astigmatism, and the like.
Although mechanisms for correcting these are conceivable, the following description assumes that the imaging characteristic correction device mainly corrects only the distortion (including the magnification) of the projected image.

In FIG. 2, the lens element 27 closest to the reticle R, which constitutes the projection optical system PL, is fixed to a support member 28, and the lens elements 29, 30, 31,. Is fixed to the lens barrel 32. The support member 28 is provided with projection optics via a plurality of (three in this case) telescopic drive elements, for example, piezo elements 11a, 11b, and 11c (the drive element 11c on the far side of the drawing is not shown in FIG. 2). System P
It is connected to the L lens barrel 32. Drive element 11
The drive voltages applied to a, 11b, and 11c are independently controlled by the imaging characteristic control unit 12, whereby the lens element 27 can be arbitrarily tilted with respect to the plane orthogonal to the optical axis AX and in the optical axis direction. It has a movable configuration.
The drive amount of the lens element 27 by each drive element is strictly measured by a position sensor (not shown), and the position is maintained at a target value by servo control.

The support member 28 of the lens element 27 in the projection exposure apparatus 110 _1, the drive element 11a, 11b,
An imaging characteristic correction device (also serving as a magnification adjusting means) is configured by the imaging characteristic control unit 12 that controls the driving voltage for the imaging characteristic 11c. Note that the optical axis AX of the projection optical system PL indicates a common optical axis of the lens elements 29 and below.

Next, in order to measure the distortion of the projected image, the aerial image measuring device 60 for photoelectrically detecting the projected image of the measurement mark (mark pattern) formed on the reticle R via the projection optical system PL is measured. This will be described with reference to FIG.

FIG. 3 is an enlarged view showing the vicinity of wafer stage WST of FIG. 2 including aerial image measuring device 60. In FIG. 3, a projecting portion having an open top is provided on the upper surface of one end of wafer stage WST, and light-receiving glass 62 is fitted in a state of closing the opening of the projecting portion. On the upper surface of the light-receiving glass 62, a light-shielding band 64a formed of a chromium layer is formed at a peripheral portion thereof, and a substantially square opening pattern 64 is formed at a central portion.

Inside the wafer stage 50 below the opening pattern 64, a relay optical system composed of lenses 66 and 68 and an illumination light beam (image light beam) relayed by a predetermined optical path length by the relay optical system (66, 68). 3) a light receiving optical system including a bending mirror 69 for bending the optical path and a photoelectric sensor 70 including a photoelectric conversion element such as a silicon photodiode or a photomultiplier.

In this embodiment, the wafer stage WS
The protruding portion on the upper surface of one end of the T, the light receiving glass 62, the opening pattern 64 formed by the light shielding band 64a on the light receiving glass 62, the relay optical system (66, 68), the folding mirror 6
The aerial image measuring device 60 is constituted by the photoelectric sensor 9 and the photoelectric sensor 70.

According to the aerial image measuring device 60, when detecting the projected image of the measurement pattern formed on the reticle R via the projection optical system PL, the illumination light IL transmitted through the projection optical system PL. Illuminates the light-receiving glass 62 and the light-receiving glass 6
Illumination light IL that has passed through the upper opening pattern 64 reaches the photoelectric sensor 70 through the light receiving optical system. The photoelectric sensor 70 performs photoelectric conversion and outputs a light amount signal P corresponding to the amount of received light to the main controller 50. I do.

Next, an example of a method of detecting a distortion of a projected image using the aerial image measuring device 60 will be described.

As a premise, here, FIG.
It is assumed that a measurement mark 90 is formed as a line and space (L / S) mark pattern including five bar marks as shown in FIG. In FIG. 4, the hatched portions (shaded portions) represent light-shielding bands.

This projection image is detected by moving the wafer stage WST such that the light-shielding portion 64a of the opening pattern 64 on the light receiving glass 62 on the wafer holder 9 side is located immediately below the optical axis AX of the projection optical system PL. Started with

At this start position, when the measurement mark 90 is illuminated by the illumination light IL from the illumination system IOP, the illumination light IL transmitted through the measurement mark 90 portion (five bar marks) causes the measurement mark 90 to be displayed on the wafer stage WST. Light receiving glass 6
A projection image 90 ′ of the measurement mark 90 is formed on the light-shielding portion 64 a of the opening pattern 64 on the wafer holder 52 side.
The state at this time is shown in FIG.

In response to an instruction from main controller 50, stage control system 19 moves wafer stage WST at a predetermined speed in the -X direction via a stage drive system. Thus, the measurement mark 90 gradually overlaps the opening pattern 64 from the right side of the projected image 90 ′. As the overlap between the projection image 90 'of the measurement mark 90 and the aperture pattern 64 increases, the amount of light incident on the photoelectric sensor 70 increases, and the time when the projection image 90' of the measurement mark 90 and the aperture pattern 64 just overlap is obtained. It becomes the maximum light quantity. Thereafter, when the wafer stage WST further moves in the −X direction, the amount of light incident on the photoelectric sensor 70 gradually decreases, and when the projection image 90 ′ of the measurement mark 90 and the opening pattern 64 no longer overlap, the photoelectric sensor The amount of light incident on 70 is zero.

FIG. 6A shows the change in the light amount at this time. The main controller 50 differentiates the waveform of the light amount signal P (actually, digital data captured at a predetermined sampling interval) as shown in FIG. A differential waveform as shown in FIG. 6B is calculated. As is clear from FIG. 6B, when the front edge of the opening pattern 64 in the scanning direction crosses the projected image 90 'of the measurement mark, the light amount gradually increases, that is, the differential waveform becomes positive. . Conversely, when the rear edge of the opening pattern 64 in the scanning direction crosses the projected image 90 'of the measurement mark 90, the light amount gradually decreases, that is, the differential waveform becomes negative.

The main controller 50 performs known signal processing such as Fourier transform based on the differential waveform as shown in FIG. 6B, and an optical image (aerial image) on which the measurement mark 90 is projected. Is detected.

By detecting the projection images (aerial images) of the plurality of measurement marks arranged on the reticle R using the detection method described above, the magnification of the projection optical system PL and the image formation such as distortion are detected. The distortion of the projected image including the characteristics is measured.

Returning to FIG. 2, main controller 50 is connected to LAN 17
0 is connected to and is connected to the MC 120 ₁ via the communication path 180 which is provided in a different path from the LAN 170. Then, main controller 50 via the communication path 180, and transmits and receives operating parameters from the MC 120 _1, the progress and results of the exposure operation in MC 120 _1. Further, main controller 50 transmits the measurement result of the distortion of the projected image to centralized information server 140 via LAN 170.

Returning to FIG. 1, each of the MCs 120 _{1 to} 120 _N is configured in the same manner as a normal personal computer. Each MC 120 _i communicates with a corresponding projection exposure apparatus 110 _i via a communication
Through the N170, performs communication with the image distortion calculation unit 130 makes an inquiry of the operating parameters of the corresponding projection exposure apparatus 110 _i, also, the operation of the projection exposure apparatus 110 _i corresponding the image distortion arithmetic unit 130 Receive parameters. Note that each MC 120 _i is
It has also manage coater / developer (not shown) installed at 0 _i paired.

The image distortion calculation device 130 is constituted by a medium-scale computer system (for example, a mini computer system or an engineering workstation system) having a high calculation capability. This image distortion calculation device 1
Reference numeral 30 denotes the MCs 120 ₁ to ₁ via the LAN 170.
Other communications with 20 _N, LAN 170 and through the terminal server 150 communicates with the host computer 160 receives the designation information of the exposure lot from the host computer 160, also specified exposure Lot A candidate for a projection exposure apparatus suitable for the exposure is determined, and the determination result is transmitted to the host computer 160. Further, the image distortion calculation device 130
Communicates with the centralized information server 140 via the LAN 170, and exchanges data described later.

The centralized information server 140 comprises a mass storage device and a LAN interface. The large-capacity storage device stores exposure history data relating to a lot of wafers W managed by the image distortion calculation device 130. The exposure history data includes distortion data of a projected image during exposure of each layer for each wafer lot. Further, the large-capacity storage device stores a drawing error of a reticle to be used.

In the present embodiment, the distortion data of the projected image at the time of exposure of each layer includes the distortion adjustment parameter of the projected image relating to the projection optical system PL of the projection exposure apparatus used in the exposure of each layer, and the reticle used. Drawing errors and the projection exposure apparatus using the aerial image measuring device 60 described above periodically (for example, once / day, once / week, once / month, etc.)
Is calculated by the image distortion calculator 130 based on the projection image distortion data measured under the predetermined exposure condition, and stored in the mass storage device of the centralized information server 140. Note that a distortion management device includes the image distortion calculation device 130 and the centralized information server 140.

The terminal server 150 is connected to the LAN 1
It is configured as a gateway processor for absorbing the difference between the communication protocol of 70 and the communication protocol of the host computer 160. This terminal server 15
0, the host computer 160 and the LAN 17
Communication with the MCs 120 _{1 to} 120 _N and the image distortion calculation device 130 connected to 0 is enabled.

The host computer 160 is composed of a large-sized computer, and performs overall control in the manufacture of semiconductor elements and the like in a factory, for example, including a lithography process. The determining device includes the image distortion calculating device 130, the centralized information server 140, and the host computer 160.

As the LAN 170, any of a bus type LAN and a ring type LAN can be adopted. In the present embodiment, a bus type LAN of a carrier sensitive medium access / contention detection (CSMA / CD) system of the IEEE802 standard is used.
You are using The communication path 180 may be a communication path of either a serial type or a parallel type. In this embodiment, a serial type communication path of the RS232C standard is used.

Next, an algorithm of the exposure processing of the wafer W by the lithography system 100 of the present embodiment configured as described above will be described with reference to FIG.

As a prerequisite for executing the exposure processing algorithm shown in FIG. 7, the wafer W to be exposed is
Exposure of one or more layers has already been performed. Exposure history data of the wafer W, each of the projection exposure apparatuses 110 ₁ to 110 ₁
It is assumed that the distortion data of the projected image regarding 0 _N and the drawing error of the pattern formed on the reticle R to be transferred are stored in the centralized information server 140.

First, in step 201 in FIG. 7, the host computer 160 should secure the overlay identifier (for example, lot number) of the wafer W to be subjected to the overlay exposure and the overlay accuracy in the overlay exposure. An exposure exposure layer suitable for performing exposure of the wafer W of the lot number by designating an exposed layer (hereinafter referred to as “reference layer”) or more and a reticle identifier (for example, a reticle number) to be used. The device is connected to the terminal server 150 and the LAN.
An inquiry is made to the image distortion calculation device 130 via 170.

Next, in step 203, the image distortion calculation device 130 performs exposure of each reference layer from the exposure history information of the lot of the wafer W from the centralized information server 140 in accordance with the received lot identifier and the reference layer. The distortion data of the projected image is read out via the LAN 170. Further, image distortion calculation device 130 reads out drawing error of reticle R used from centralized information server 140 via LAN 170 according to the received reticle identifier.

Subsequently, the image distortion calculation device 130 takes into account the drawing error of the readout reticle R, and the projection image distortion in each of the projection exposure devices 110 _i has occurred during the exposure of the reference layer. the distortion adjustment parameter values the difference between the distortion of the image is minimum is calculated for each projection exposure apparatus every 110 _i. Here, when there are a plurality of reference layers, the distortion of the projection image generated at the time of exposure of each reference layer is statistically processed (for example, average calculation) to obtain the distortion of the projection image serving as a reference for superposition. .

Then, each of the calculated projection exposure apparatuses 110
_{i, the} distortion adjustment parameter value for each projection exposure apparatus 1
10 _i determines whether or not the adjustment capability range, if it is determined affirmatively is generated at the time of exposure of the distortion and the reference layer of the projected image when applying the calculated distortion adjustment parameter values determining the difference between the distortion of which was projected image as a residual error of those of the projection exposure apparatus 110 _i. On the other hand, when a negative determination is made, the distortion of the projected image that minimizes the difference from the distortion of the projected image that occurred during the exposure of the reference layer within the range of the adjustment capability of those projection exposure apparatuses. Is calculated, and the difference between the distortion of the projected image when these distortion adjustment parameter values are applied and the distortion of the projected image generated during exposure of the reference layer is calculated by the projection exposure apparatus 110. _{Determined as} the residual error of _i . That is, for each of all of the projection exposure apparatus 110 _i, obtaining a residual between the best distortion adjustment parameter values in the range of distortion adjustment capability of the projected image errors.

Next, the image distortion calculator 130 compares each residual error with a predetermined allowable error, and determines a projection exposure apparatus having a residual error equal to or less than the allowable error as a candidate for a projection exposure apparatus that performs overlay exposure. I do.

Then, in step 205, the list of the determined projection exposure apparatuses is sent to the host computer 160 as a candidate list to the LAN 170 and the terminal server 150.
To send over.

Next, in step 207, the host computer 160 refers to the current operation status and future operation schedule of the projection exposure apparatuses listed in the received candidate list, and proceeds with the lithography process most efficiently as a lithography system. In view of this, a projection exposure apparatus that performs overlay exposure is selected. For example, the host computer 16
In the case of 0, if there is a projection exposure apparatus that is not currently in operation among the projection exposure apparatuses listed in the candidate list, the projection exposure apparatus is selected. When all of the projection exposure apparatuses listed in the candidate list are in operation, the host computer 160
Selects, for example, a projection exposure apparatus that is expected to complete the current exposure operation first.

In step 205 described above, the image distortion calculation device 130 calculates the residual error of each projection exposure apparatus listed in the candidate list in addition to the candidate list.
0 may be transmitted. In this case,
In step 207, the host computer can select a projection exposure apparatus that performs overlay exposure, taking into account the processing efficiency and exposure accuracy in the lithography system. For example, when a plurality of projection exposure apparatuses listed in the candidate list are not currently in operation, by selecting the one with the smallest residual error among them, it is possible to increase the exposure accuracy while ensuring processing efficiency.

[0067] In the following description the case where the projection exposure apparatus 110 ₁ is selected as an example.

[0068] Then, in step 209, the host computer 160 immediately if not running projection exposure apparatus 110 ₁ selected, were also selected projection exposure apparatus 11
0 ₁ is in operation, waits for the end of the exposure operation, and designates the identifier of the lot of the wafer W to be subjected to the overlay exposure and specifies the MC connected to the projection exposure apparatus 110 ₁ selected.
120 and instructs the exposure run through LAN170 to _1.

Next, in step 211, exposure execution
MC120 which received the instruction of₁Is the overlay exposure
Of the lot of the wafer W to be an elephant and the projection exposure apparatus 1
10 ₁Of the wafer W of the lot is designated.
The adjustment parameter value of the distortion of the projected image when illuminating
An inquiry is made to the image distortion calculation device 130. In addition, projection exposure
Device 110_iAnd MC120_iCorresponds to one-to-one,
MC120₁Is a projection exposure apparatus 110₁Instead of the identifier
And MC120₁It is also possible to specify the identifier of
You.

Next, in step 213, the image distortion calculation device 130 performs the processing in step 20 on the wafer W lot according to the received wafer W lot identifier.
Calculated in 3, the distortion adjustment parameters related to the projection exposure apparatus 110 ₁ selected to MC 120 ₁ LAN 170
To send over. Before or after this transmission, before the overlay exposure, the image distortion calculation device 130 specifies the distortion of the projection image of the lot in the overlay exposure, and transmits the distortion data of the projection image to the centralized information via the LAN 170. The information is stored in the server 140 and the exposure history information of the lot is temporarily updated. When after successful completion of the exposure from the MC 120 ₁ is notified, it changes the temporary updating of the exposure history information of the lot to this update.

Next, at step 215, MC12
0 ₁ transmits the received distortion adjustment parameter to the projection exposure apparatus 110 ₁ via the communication path 180 ₁ . The projection exposure apparatus 110 _1, based on the distortion adjustment parameters received, by controlling the imaging characteristic correction device itself, adjusting the distortion of the projected image. Thereafter, in step 217, by the projection exposure apparatus 110 ₁ strain is adjusted in the projected image, the pattern formed on reticle R, by overlay exposure is transferred to the wafer W.

As described above, in the lithography system 100 of the present embodiment, each time a lot of each wafer W is subjected to the overlay exposure, the residual error due to the distortion of the projected image generated in the exposure of the exposed reference layer is reduced. Can be kept within an allowable range, and an appropriate projection exposure apparatus can be selected from the viewpoint of improving the processing efficiency of the lithography system. Therefore, mass productivity can be improved while ensuring high overlay accuracy.

In the above embodiment, all of the plurality of projection exposure apparatuses are scanning exposure apparatuses. However, all projection exposure apparatuses may be step-and-repeat type steppers. The scanning exposure apparatus and the stepper may be mixed. However, when the scanning type exposure apparatus and the stepper are mixed, or when the field size is different even when all the exposure apparatuses are steppers, the measurement positions for measuring the distortion of the projection image are different. May not be directly comparable. In that case, the distortion of the projected image at a required position may be obtained from an appropriate model of the distortion of the projected image (for example, a cubic model) and compared.

Further, in the above embodiment, all of the plurality of projection exposure apparatuses have the ability to adjust the distortion of the projected image, but at least one projection exposure apparatus has the ability to adjust the distortion of the projected image. do it. In the case where projection exposure apparatuses that do not have the capability of adjusting the distortion of the projected image coexist, use the measured values of the distortion of the projected image instead of calculating the best value of the distortion adjustment parameter when creating the candidate list. Then, the residual error may be obtained.

In the above embodiment, when adjusting the distortion of the projected image, the imaging characteristics of the projection optical system are adjusted. However, by adjusting the synchronous movement state between the reticle and the wafer, the projected image is adjusted. May be adjusted. Further, the distortion of the projected image may be adjusted by adjusting both the imaging characteristics of the projection optical system and the synchronous movement state between the reticle and the wafer.

In the above embodiment, the lens element of the projection optical system is driven by adjusting the imaging characteristics of the projection optical system. However, the inside of a part of the closed chamber on the optical path of the exposure light in the projection optical system is controlled. The imaging characteristics of the projection optical system may be adjusted by controlling the gas pressure and adjusting the refraction at that portion.

In the above embodiment, the measurement of the distortion of the projected image of each projection exposure apparatus is performed periodically. However, the calculation of the distortion adjustment parameter is performed for each exposure of each layer of each wafer lot. It may be performed immediately before.

In the above embodiment, the distortion of the projected image of each projection exposure apparatus is measured by detecting the aerial image using the aerial image measuring device, but the measurement pattern formed on the reticle for measurement is measured. It is also possible to measure the distortion of the projected image by actually transferring the pattern onto the measurement wafer and measuring the pattern transferred onto the wafer.

Further, when the projection exposure apparatus has a function of detecting an aerial image by an aerial image measuring device, a position detection mark is also formed on a reticle for manufacturing a device, and the aerial image of the position detection mark is detected. Thus, each time the reticle is used in the projection exposure apparatus, distortion measurement of the projected image and alignment of the reticle can be accurately performed.

The exposure object of the projection exposure apparatus is not limited to a wafer for semiconductor manufacturing as in the above embodiment, but may be, for example, a square glass plate for exposing a liquid crystal display element pattern, a thin-film magnetic plate, or the like. It can be widely applied to substrates for manufacturing heads.

The illumination light IL in the projection exposure apparatus of the above embodiment includes g-line (436 nm), i-line (365 nm), KrF excimer laser light (248n).
m), ArF excimer laser light (193 nm), F ₂ laser light (157 nm), and charged particle beams such as X-rays and electron beams. For example, when an electron beam is used, a thermionic emission type lanthanum hexabolite (LaB ₆ ) or evening light (Ta) can be used as an electron gun.

The magnification of the projection optical system may be not only a reduction system but also an equal magnification or an enlargement system.

As the projection optical system, KrF, Ar
Glass material when using far ultraviolet rays such as F excimer laser light
Use materials that transmit deep ultraviolet rays such as quartz and fluorite
Yes, F _TwoWhen using laser light or X-rays, catadioptric systems or
Is a reflective optical system (the reticle is also of the reflective type)
Use an electron beam, and use an optical system when using an electron beam.
If an electron optical system consisting of an electron lens and a deflector is used,
Good. The optical path through which the electron beam passes must be in a vacuum state.
Needless to say.

When a linear motor (see US Pat. No. 5,623,853 or US Pat. No. 5,528,118) is used for a wafer stage or a reticle stage, air bearing is used. Either an air levitation type or a magnetic levitation type using Lorentz force or reactance force may be used. Further, the wafer stage or reticle stage may be a tie that moves along a guide, or may be a guideless type without a guide.

The reaction force generated by the movement of the wafer stage is mechanically applied to the floor (ground) using a frame member (as described in US Pat. No. 5,528,118). You can escape. The reaction force generated by the movement of the reticle stage is disclosed in
No. 75 (US Serial No. 08/41)
No. 6,558), a frame member may be used to mechanically escape to the floor (ground).

The illumination optical system and the projection optical system composed of a plurality of lenses are incorporated in the main body of the projection exposure apparatus for optical adjustment, and a reticle stage and a wafer stage composed of many mechanical parts are mounted on the main body of the projection exposure apparatus. By connecting wirings and pipes, and further performing overall adjustment (electrical adjustment, operation confirmation, etc.), the projection exposure apparatus of the present embodiment, and furthermore, the lithography system of the present embodiment can be manufactured. It is desirable that the projection exposure apparatus be manufactured in a clean room in which temperature, cleanliness, and the like are controlled.

In the semiconductor device, a step of designing the function and performance of the device, a step of manufacturing a reticle based on the design step, a step of manufacturing a wafer from a silicon material, and a step of manufacturing a reticle by the lithography system of the above-described embodiment. It is manufactured through a step of exposing a pattern to a wafer, a device assembling step (including a dicing step, a bonding step, and a package step), an inspection step, and the like.

[0088]

As described above in detail, according to the exposure method of the present invention, when performing the overlay exposure for the sensitive substrate on which at least one or more layers have been exposed, the sensitive substrate to be subjected to the overlay exposure is used. Based on the exposure history indicating what kind of projection exposure apparatus has been used so far and the distortion adjustment capability of each projection exposure apparatus, select a projection exposure apparatus that can ensure high overlay accuracy. . Therefore, overlay exposure can be performed with high overlay accuracy while using a plurality of projection exposure apparatuses.

Further, when selecting a projection exposure apparatus for performing the overlay exposure, by considering the operation status of each projection exposure apparatus, it is possible to improve the throughput of the exposure processing while ensuring high overlay accuracy.

Further, according to the lithography system of the present invention, at the time of superposition exposure, the judgment device is based on the exposure history of the sensitive substrate to be superposed and the distortion adjustment capability of each projection exposure device. Then, a projection exposure apparatus that can ensure the overlay accuracy with high accuracy is selected.
That is, since the overlay exposure of the sensitive substrate is performed using the exposure method of the present invention, the overlay exposure can be performed with high overlay accuracy while using a plurality of projection exposure apparatuses.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a schematic configuration of a lithography system according to an embodiment.

FIG. 2 is a diagram showing a schematic configuration of the projection exposure apparatus of FIG.

FIG. 3 is an enlarged view showing a portion near a wafer stage in FIG. 2;

FIG. 4 is a diagram illustrating an example of a measurement mark formed on a reticle.

FIG. 5 is a diagram for explaining a method of photoelectrically detecting a projected image of a measurement mark in FIG. 4;

6A is a diagram illustrating a waveform of a light amount signal obtained as a result of photoelectrically detecting the projected image of the measurement mark in FIG. 4, and FIG. 6B is a diagram illustrating a differential waveform of FIG.

FIG. 7 is a flowchart of an algorithm of an exposure process performed in the lithography system according to the embodiment;

[Explanation of symbols]

110: Projection exposure device, 130: Image distortion calculation device (part of distortion management device, part of determination device), 140: Centralized information server (part of distortion management device, part of determination device), 16
0: Host computer (part of process management device and judgment device)

 ──────────────────────────────────────────────────の Continuing on the front page (72) Inventor Yuki Ishii 3-2-3 Marunouchi, Chiyoda-ku, Tokyo F-term in Nikon Corporation (Reference) 5F046 BA04 BA05 CA03 CA04 CC01 CC02 CC03 CC10 CC13 CC16 CC18 DA01 DA13 DA27 DA30 DB01 DD06 EA03 EA04 EA09 EB03 EC05 ED03 FA17 FC06

Claims (10)

[Claims] 1. An exposure method for exposing a sensitive substrate in multiple layers with a plurality of projection exposure apparatuses including at least one projection exposure apparatus capable of adjusting a distortion of a projected image, wherein the at least one layer is exposed. In overlay exposure of the substrate, the projection exposure apparatus that overlays and exposes the sensitive substrate is based on the exposure history of the sensitive substrate and the distortion adjustment capability of each of the plurality of projection exposure apparatuses. An exposure method characterized by selecting from the following. 2. The apparatus according to claim 1, wherein the exposure history includes distortion information of a projected image at the time of exposure of a projection apparatus that has exposed the sensitive substrate among the plurality of projection exposure apparatuses.
Exposure method according to 1. 3. The method according to claim 1, wherein, when the selection is performed, distortion adjustment is performed for each of the plurality of projection exposure apparatuses so as to minimize an overlay error with a projection image by the projection exposure apparatus that has exposed the sensitive substrate. The exposure method according to claim 1, wherein an error is obtained. 4. The method according to claim 3, wherein when performing the overlay exposure by the selected projection exposure apparatus, information on distortion adjustment when the residual error is obtained is used.
Exposure method according to 1. 5. The exposure method according to claim 1, wherein, when selecting a projection exposure apparatus that performs the overlay exposure, a drawing error of a pattern formed on a mask is further considered. 6. The exposure apparatus according to claim 1, wherein, when selecting a projection exposure apparatus that performs the overlay exposure, an operation state of the plurality of exposure apparatuses at the time of the selection is further considered. Method. 7. A plurality of projection exposure apparatuses each including at least one projection exposure apparatus capable of adjusting a distortion of a projection image; and, when performing overlay exposure of the sensitive substrate having been exposed to at least one layer, the sensitive substrate is exposed. A lithography system comprising: a determination device that selects a projection exposure device that superimposes and exposes the sensitive substrate from the plurality of projection exposure devices based on an exposure history and a distortion adjustment capability of each of the plurality of projection exposure devices. 8. A process management device for managing an operation status of the plurality of projection exposure apparatuses; a distortion management for managing exposure history of the sensitive substrate and distortion setting of projection images of the plurality of projection exposure apparatuses. The lithographic system according to claim 7, comprising a management device. 9. The distortion management device calculates an optimal distortion set value when exposing the sensitive substrate, for a projection exposure device capable of adjusting the projection image, based on the exposure history of the sensitive substrate. The lithography system according to claim 8, wherein: 10. The exposure method used in the lithography system according to claim 9, wherein, when exposing a sensitive substrate, the process management device supplies an identifier of the sensitive substrate to the distortion management device. And the distortion management device, based on an exposure history of the sensitive substrate identified by the identifier of the sensitive substrate, and the distortion adjustment capability of each of the plurality of projection exposure devices,
A second step of determining one or more candidate projection exposure apparatuses to perform exposure from among the plurality of projection exposure apparatuses, and supplying information on the determined projection exposure apparatus to the process management apparatus; A third step in which the apparatus selects a projection exposure apparatus that exposes the sensitive substrate from the determined projection exposure apparatuses based on the determined operation state of the projection exposure apparatus; and the selected projection exposure. A fourth step in which the selected projection exposure apparatus queries the distortion management apparatus for a distortion setting parameter when exposing the sensitive substrate when the distortion of the projection image of the apparatus is adjustable; A step in which the projection exposure apparatus performs exposure while adjusting the distortion of the projected image based on the distortion setting parameter from the distortion management apparatus.