JP2000133563A - Exposure method and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form highly accurate and fine device patterns. SOLUTION: At forming of device patterns 41b which extend to a first direction on a wafer by multiply exposing a wafer with illuminating lights, first scanning exposure is operated by moving the wafer to a second direction, orthogonally crossing the first direction synchronously with the relative movement of a mask to the illuminating lights, and then a second scanning exposure is operating by synchronously moving the mask and the wafer to a direction opposite to that at the first scanning exposure. At the first scanning exposure and second scanning exposure, the transferring positions of the patterns are shifted to the second direction so that one part of the projected images of patterns 41a of the mask overlaps on the wafer. The exposure amount at the time of the first scanning exposure and second scanning exposure is set so as to be half the proper exposure amount corresponding to the sensitivity characteristics of a photoresist applied to the wafer. In this case, the superimposed parts of the projected images can have the proper exposure, and the parts can be obtained as the device patterns 41b.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method used for manufacturing a micro device such as a semiconductor device or a liquid crystal display device, and more particularly, to a projection optical system for projecting an image of a pattern formed on a mask. And an exposure method for sequentially projecting and transferring a photosensitive substrate onto a photosensitive substrate by a scanning method.

[0002]

2. Description of the Related Art Conventionally, various exposure apparatuses have been used for manufacturing a semiconductor element or a liquid crystal display element by a photolithography process. At present, an image of a pattern of a photomask (including a reticle) has been used. A projection exposure apparatus is generally used, which transfers an image onto a substrate (hereinafter, referred to as a photosensitive substrate) such as a wafer or a glass plate having a surface coated with a photosensitive material such as a photoresist via a projection optical system. . In recent years, as this projection exposure apparatus, two photosensitive substrates have been used.
It is mounted on a substrate stage that is movable in a three-dimensional manner, and the photosensitive substrate is stepped by this substrate stage, and the operation of sequentially exposing and transferring the reticle pattern image to each shot area on the photosensitive substrate is repeated. A so-called step-and-repeat type reduction projection exposure apparatus (so-called stepper) has become mainstream.

[0003] Recently, a step-and-scan type projection exposure apparatus (for example, a scanning exposure apparatus as disclosed in Japanese Patent Application Laid-Open No. 7-176468) has been improved by improving a static exposure apparatus such as a stepper. Devices) have also become relatively popular. This step and
The scanning type projection exposure apparatus can expose a large field with a smaller optical system as compared with a stepper, so that the projection optical system can be manufactured easily and high throughput can be expected due to the reduction in the number of shots due to the large field exposure. The relative scanning of the reticle and the wafer with respect to the projection optical system has an averaging effect, and has advantages such as a reduction in distortion and an increase in the depth of focus. Further, the integration degree of the semiconductor element is 16M (mega).
To 64M DRAM, 256M and 1G in the future
It is said that a scanning projection exposure apparatus will become the mainstream in place of a stepper because a large field becomes indispensable as the height increases with the times such as (giga).

Further, when exposing a photosensitive substrate using these projection exposure apparatuses, for example, Japanese Patent Application Laid-Open No. 4-273245.
As described in Japanese Unexamined Patent Publication (Kokai) No. H10-209, a so-called modified illumination method (SHRINC: Super High Resolution by IllumiNat
The resolution and depth of focus of a pattern to be formed have been improved by using ion control.

[0005]

Since this type of projection exposure apparatus is mainly used as a mass production machine for semiconductor devices and the like, it is necessary to determine how many wafers can be subjected to exposure processing within a certain period of time. It is inevitably required to improve the processing capacity, that is, the throughput.

In this regard, in the case of a step-and-scan projection exposure apparatus, when a large field is exposed, as described above, the number of shots to be exposed in a wafer is reduced, so that an improvement in throughput is expected. However, since exposure is performed during constant-speed movement by synchronous scanning between the reticle and the wafer, acceleration / deceleration areas are required before and after the constant-speed movement area. In the case of exposing, there is a possibility that the throughput may be reduced rather than the stepper.

[0007] The flow of processing in this type of projection exposure apparatus is roughly as follows.

First, a wafer loading step of loading a wafer on a wafer table using a wafer loader is performed.

Next, a search alignment step is performed in which a rough alignment of the wafer is detected by a search alignment mechanism. This search alignment step is, for example, based on the outer shape of the wafer, or
This is performed by detecting a search alignment mark on the wafer.

Next, a fine alignment step for accurately determining the position of each shot area on the wafer is performed.
In this fine alignment step, an EGA (Enhanced Global Alignment) method is generally used. In this method, a plurality of sample shots in a wafer are selected, and an alignment mark (wafer mark) attached to the sample shot is selected. Measure the position of
On the basis of the measurement result and the design value of the shot array, a statistical operation is performed by a so-called least square method or the like to obtain all shot array data on the wafer (see Japanese Patent Application Laid-Open No. SHO 6-69).
The coordinate position of each shot area can be obtained with relatively high accuracy with high throughput.

Next, while sequentially positioning each shot area on the wafer at the exposure position based on the coordinate position of each shot area obtained by the above-described EGA method or the like and a pre-measured baseline amount, the projection optical system is controlled. An exposure step of transferring a reticle pattern image onto a wafer via the reticle is performed.

Next, a wafer unloading step of unloading the exposed wafer on the wafer table using a wafer unloader is performed. This wafer unloading step is performed simultaneously with the above-described wafer loading step of the wafer to be subjected to the exposure processing. That is, a wafer exchange step is constituted by the above and.

As described above, in the conventional projection exposure apparatus, four operations such as wafer exchange → search alignment → fine alignment → exposure → wafer exchange are repeatedly performed using one wafer stage. .

The throughput THOR [sheets / time] of this type of projection exposure apparatus is as follows: T1 is the wafer exchange time, T2 is the search alignment time, T3 is the fine alignment time, and T4 is the exposure time. It can be expressed as the following equation (1).

THOR = 3600 / (T1 + T2 + T3 + T4) (1) The operations of T1 to T4 are performed in the order of T1 → T2 → T3 → T4 → T
.. Are sequentially (sequentially) repeatedly executed. Therefore, if the speed of each element from T1 to T4 is increased, the denominator becomes smaller, and the throughput THOR can be improved. However, the above-described T1 (wafer replacement time) and T2 (search alignment time) are relatively small in improvement because only one operation is performed for one wafer. In the case of T3 (fine alignment time), the throughput can be improved by reducing the number of shot samples or reducing the measurement time of a single shot when using the above-described EGA method. Since the accuracy is degraded, T3 cannot be easily reduced.

T4 (exposure time) includes a wafer exposure time and a stepping time between shots. For example, in the case of a scanning projection exposure apparatus such as a step-and-scan method, it is necessary to increase the relative scanning speed between the reticle and the wafer by the amount of shortening the wafer exposure time. The scanning speed cannot be easily increased.

In this type of projection exposure apparatus, in addition to the above throughput, important conditions include resolution, depth of focus (DOF), and line width control accuracy. The resolution R is defined as follows: the exposure wavelength is λ, and the numerical aperture of the projection lens is N.D. A. (Numerical Aperture), λ / N. A. And the depth of focus DOF is λ /
(NA) is proportional to ² .

Therefore, in order to improve the resolution R (decrease the value of R), the exposure wavelength λ must be reduced or the numerical aperture N.P. A. Need to be larger. In particular, recently, the density of semiconductor elements and the like has been increasing, and the device rule has become 0.2 μmL / S (line and space) or less. A KrF excimer laser is used as an illumination light source. However, as described above, it is inevitable that the degree of integration of semiconductor elements will further increase in the future, and it is desired to develop a device having a light source having a shorter wavelength than KrF. Representative examples of a next-generation apparatus having such a shorter wavelength light source include an apparatus using an ArF excimer laser as a light source, an electron beam exposure apparatus, and the like.
In the case of excimer lasers, high output is difficult to produce, the laser life is short, and the technical costs are high, and the technical costs are high.In addition, the throughput of electron beam lithography systems is higher than that of optical lithography systems. However, the reality is that the development of the next-generation machine with the main viewpoint of shortening the wavelength will not be as expected.

Another technique for increasing the resolution R is to use a numerical aperture N.P. A. May be increased, but N.I. A.
Has a demerit that the DOF of the projection optical system is reduced. This DOF is UDOF (Usable
Depth of Forcus: The part used on the user side: pattern step, resist thickness, etc., and the total focal difference (TF
D). Until now, UDOF
Therefore, the direction in which the DOF is increased is the main axis of development of the exposure apparatus, and as a technique for increasing the DOF, for example, deformed illumination or the like has been put to practical use.

By the way, in order to manufacture a device,
It is necessary to form a pattern combining L / S (line and space), isolated L (line), isolated S (space), and CH (contact hole) on the wafer. Exposure parameters for performing optimal exposure differ for each pattern shape such as S and isolated lines. For this reason, conventionally, using a method called ED-TREE (excluding CHs with different reticles), the resolution line width is within a predetermined tolerance with respect to a target value, and a predetermined D
A common exposure parameter (a coherence factor σ, NA, exposure control accuracy, reticle drawing accuracy, and the like) for obtaining an OF is obtained, and is used as a specification of an exposure apparatus. However, it is thought that there will be the following technical flows in the future.

The exposure wavelength is shortened from g-line (436 nm) to i-line (365 nm) to KrF (248 nm). From now on, ArF (193 nm) → F ₂ (157n
m), but the technical hurdle is high.
There is also a possibility of shifting to EB exposure.

It is expected that scanning exposure such as step-and-scan will become the mainstream of steppers instead of static exposure such as step-and-repeat.
This technique enables a large field exposure with a projection optical system having a small diameter (especially in the scanning direction), and a higher N.D. A.
Is easy to realize.

Against the background of the technical trends described above, a double exposure method has been reviewed as a method of improving the limit resolution. This double exposure method is used in KrF and ArF exposure apparatuses, and is up to 0.1 μmL / S. Attempts to expose are being considered. Generally, the double exposure method is roughly classified into the following three methods.

(1) L / S and isolated lines having different exposure parameters are formed on different reticles, and double exposure is performed on the same wafer under optimum exposure conditions.

(2) When the phase shift method or the like is introduced, the limit resolution of the L / S is higher than that of the isolated line in the same DOF.
By utilizing this, all patterns are formed with L / S on the first reticle, and L / S is formed on the second reticle.
An isolated line is formed by thinning S.

(3) In general, an isolated line is smaller than N / S A. But high resolution can be obtained. Therefore, all the patterns are formed by isolated lines, and the L / S is formed by combining the isolated lines formed by the first and second reticles, respectively.

The above double exposure method has two effects, that is, an improvement in resolution and an improvement in DOF.

However, in the double exposure method, since the exposure processing needs to be performed a plurality of times using a plurality of reticles, the exposure time (T4) becomes twice or more as compared with the conventional apparatus, and the throughput is largely deteriorated. Because of the inconvenience of doing
In reality, the double exposure method is not considered seriously,
Conventionally, resolution and depth of focus (DOF) have been improved by ultraviolet exposure wavelength, modified illumination, phase shift reticle, and the like.

However, it is difficult to realize the target resolution line width of 0.1 μm of the next-generation device by devising the above-mentioned ultraviolet exposure wavelength, modified illumination, and phase shift reticle. Therefore, the above-described double exposure method is applied to KrF, Ar
There is no doubt that realizing exposure up to 0.1 μmL / S by using the F exposure apparatus is a powerful option for the development of next-generation machines for mass production of 256M and 1G DRAMs.

As means for further improving the resolving power by the double exposure method, double exposure using the above-mentioned modified illumination is considered. In the conventional modified illumination method, L / S and L / S in a predetermined direction are considered. The resolution and the depth of focus (DOF) can be improved for the isolated L, but there is a disadvantage that the resolution and the depth of focus of the pattern in the direction orthogonal to the predetermined direction are significantly reduced. This can be mostly solved by simultaneously performing deformed illumination from two orthogonal axis directions. However, when looking at each L pattern, the image is significantly deteriorated at both end portions (portions where two-dimensional edges exist) of the pattern (for example, when the edge portion is Therefore, there is a disadvantage that the accuracy cannot be expected to be improved more than when the exposure is performed using the annular illumination method.

As another problem peculiar to the double exposure method, there is an inconvenience that the throughput is necessarily reduced due to the necessity of performing the exposure processing a plurality of times using a plurality of reticles as described above. In this case, not only is the actual exposure time increased, but also the reticle conventionally mounted on the reticle stage requires one reticle.
When performing the double exposure method, the reticle stored in the reticle library is taken out one by one using a reticle loader or the like, and the reticle is exchanged with the reticle stage to align the reticle. After the alignment, the exposure process is performed through the reticle, and a series of sequences of returning to the reticle and performing reticle exchange must be sequentially repeated. Therefore, there is a disadvantage that the throughput is reduced accordingly. Therefore, when a plurality of reticles are exchanged and used, it is required to shorten the reticle exchange time and improve the throughput to some extent.

As a method of shortening the reticle exchange time, it is conceivable to mount a plurality of reticles on a reticle stage. However, in such a case, the stage becomes large, and particularly in the case of a scanning type exposure apparatus. There is also a disadvantage that the position controllability is deteriorated.

Further, when a plurality of reticles are used as a set as in the above-described double exposure, a special device is required for managing the plurality of reticles. When a fine pattern is formed by exposure, the line width of the pattern changes due to various errors due to a change in focus, a change in exposure amount, a change in synchronization accuracy of the stage, and the like. These errors can be roughly classified into a fixed error having a characteristic of reproducing with a certain tendency and an indefinite error (random error) which occurs stochastically without a certain tendency, and these errors are removed by some method. If it can be performed, it is advantageous in improving the accuracy and miniaturization of the device pattern to be formed.

However, as described above, the exposure method in which the dense pattern (L / S) is entirely exposed at the first time and the isolated line is formed at the second time is based on the photosensitive characteristic of the photoresist for each device pattern to be formed. In this case, two exposures are performed with an appropriate exposure amount according to the above. However, both the dense pattern and the isolated pattern are substantially formed by one exposure. For this reason, from the viewpoint of reducing random errors, there is no difference from the normal exposure method of forming a device pattern by one-time exposure, and there is a problem that deterioration of the pattern shape due to random errors cannot be prevented. Also, in a scanning type exposure apparatus, a stage feed error or the like may vary depending on a scanning direction, and a pattern shape or the like may vary between device patterns.

Further, since the exposure is performed twice with an appropriate exposure amount according to the photosensitive characteristics of the photoresist,
As compared with the case where a device pattern is formed by one-time exposure, the exposure amount is required twice, which requires a long time for processing, and the cost of a light source such as a laser cannot be reduced.

In addition, although the line width of the device pattern generally depends on the line width of the reticle pattern, the line width of the device pattern can be freely adjusted using a single reticle without changing the line width of the reticle pattern. If it can be changed and adjusted, it is convenient because it can flexibly respond to various requests in forming a device pattern.

The present invention has been made in view of such problems of the prior art, and has as its object to form a fine pattern with high accuracy in a scanning type exposure apparatus. Another object is to improve the processing speed of exposure and reduce costs. Another object of the present invention is to provide a technique for changing and adjusting the line width of a device pattern using a single mask.

[0038]

Means for Solving the Problems In the following description, in order to facilitate understanding, each constituent element of the present invention will be described with reference numerals shown in the drawings of the embodiments. The constituent elements of the invention are not limited by these reference numerals.

1. An exposure method according to the present invention for achieving the above object is an exposure method of sequentially projecting and transferring a pattern image formed on a mask onto a photosensitive substrate (W) via a projection optical system (PL) by a scanning method. Wherein the image of the pattern (41a, 51a) of the same mask (R) is superposed and transferred a plurality of times with an exposure amount smaller than an appropriate exposure amount according to the sensitivity characteristics of the photosensitive substrate. In this case, it is desirable to transfer the image of the same mask pattern a plurality of times with the exposure amount smaller than the appropriate exposure amount according to the sensitivity characteristic of the photosensitive substrate by reversing the scanning direction.

In order to achieve the above object, the exposure apparatus of the present invention provides a pattern (41) formed on a mask (R).
a, 51a) through a projection optical system to form a photosensitive substrate (W)
An exposure apparatus for sequentially projecting and transferring an image by a scanning method on a mask stage (17) for holding the mask;
A substrate stage (22) for holding the photosensitive substrate, an illumination optical system (2, 14) for illuminating the mask, and a projection optical system (PL) for projecting an image of the pattern of the mask onto the photosensitive substrate. A driving device (13) for driving the mask stage and the substrate stage so as to move the mask and the photosensitive substrate synchronously with respect to the projection optical system;
A control device (7) for controlling the image of the pattern of the mask to be projected and transferred by superposing a plurality of times by reversing the scanning direction with an exposure amount smaller than an appropriate exposure amount according to the sensitivity characteristic of the photosensitive substrate. It is characterized by having.

According to the exposure method and the exposure apparatus of the present invention, the same mask pattern is transferred by overlapping a plurality of times with an exposure amount smaller than an appropriate exposure amount according to the sensitivity characteristics of the photosensitive substrate. Random errors that occur stochastically without having a certain tendency are reduced by the averaging effect, so that exposure accuracy is improved and a fine pattern can be formed with high accuracy. In addition, by performing the scanning exposure a plurality of times by reversing the scanning direction, the time required for the processing can be reduced as compared with the case where the scanning exposure is performed a plurality of times in the same direction. For example, a constant error based on, for example, the stage feed accuracy can be averaged, and a highly accurate pattern with little variation between device patterns can be formed.

Further, since the image of the pattern of the same mask is superimposed and transferred a plurality of times, compared with the prior art in which exposure processing is performed a plurality of times using a plurality of masks,
The mask replacement operation is not required, and the throughput can be improved. In addition, it is not necessary to place a plurality of masks on the mask stage in consideration of the reduction of the mask replacement time, and there is no inconvenience such as an increase in the size of the stage. In addition, it is advantageous in mask management.

In addition, since one exposure of the plurality of exposures is performed with an exposure amount smaller than an appropriate exposure amount according to the sensitivity characteristics of the photosensitive substrate, a device pattern to be formed on the photosensitive substrate is changed. Compared to the prior art in which the pattern is divided so as not to overlap with each other and each of the divided patterns is exposed with an appropriate exposure amount, the scanning speed can be increased, and the processing can be accelerated. In addition, a light source having a relatively low output can be adopted as the light source, and the cost of the apparatus can be reduced.

In the above arrangement, the image position of the pattern of the mask on the photosensitive substrate may be shifted (shifted) between successive ones of the plurality of transfers. By shifting the image position on the photosensitive substrate between successive ones of the multiple transfers in this way, the line width of the device pattern formed on the photosensitive substrate can be shifted by the shift amount (shift) of the image position. ) Can be freely adjusted according to the amount of the mask pattern, and a device pattern having a line width smaller than the line width of the projected image of the mask pattern on the photosensitive substrate can be formed.

The shift of the image position on the photosensitive substrate between successive ones of the plural times of transfer is not particularly limited. For example, the shift of the scanning start position of at least one of the mask and the photosensitive substrate is shifted. The image position can be shifted in the scanning direction by making the difference between the successive transfer. However, the image position may be shifted by shifting the relative positional relationship between the mask and the photosensitive substrate in the non-scanning direction (the direction orthogonal to the scanning direction) between the successive transfers. The projection position of the image by the projection system on the photosensitive substrate may be shifted without changing the relative positional relationship between the mask and the photosensitive substrate.

The exposure conditions including the respective illumination conditions and the like in the plurality of exposures are not particularly limited, and may be the same or different. Can be set to be an appropriate exposure amount according to the sensitivity characteristics of the photosensitive substrate, in this case, the exposure amount given to the photosensitive substrate by each of the plurality of transfer Can be set approximately equal to each other.

2. According to the exposure method of the present invention for achieving the above object, the photosensitive substrate (W) is subjected to multiple exposure with illumination light to form device patterns (41b, 51b) extending along the first direction on the photosensitive substrate. In the exposure method, a first scanning exposure for moving the photosensitive substrate in a second direction orthogonal to the first direction in synchronization with a relative movement of the mask (R) with respect to the illumination light; A second synchronously moving the mask and the photosensitive substrate in a direction opposite to that of the scanning exposure;
In the scanning exposure, the transfer position of the image of the pattern is shifted in the second direction (scanning direction) such that a part of the image of the pattern of the mask (41a, 51a) overlaps on the photosensitive substrate. And In this case, the same pattern on the mask is used in the first and second scanning exposures, and the device pattern is formed in a portion where the image of the same pattern overlaps on the photosensitive substrate. it can.

An exposure apparatus according to the present invention for achieving the above object includes an illumination system (2, 14) for irradiating a mask (R) with illumination light, and the photosensitive substrate is irradiated with the illumination light via the mask. (W) is subjected to multiple exposure, and a first
Device patterns (41b, 51b)
In the exposure apparatus for forming b), in order to scan and expose the photosensitive substrate with the illumination light, the photosensitive substrate is moved in the first direction in synchronization with the relative movement of the mask with respect to the illumination light. A stage system (17, 22) moving in a second direction orthogonal to the first scanning exposure,
At the time of scanning exposure, the mask and the photosensitive substrate are moved in opposite directions, and the transfer position of the image of the pattern (41a, 51a) of the mask on the photosensitive substrate is shifted in the second direction. A control device (7, 13) for controlling the driving of the stage system so as to overlap a part of the image
And characterized in that:

According to the exposure method and the exposure apparatus of the present invention, the image of the pattern of the mask is superposed and transferred by at least two times of the first and second scanning exposures. The random error that occurs stochastically without any occurrence is reduced by the averaging effect, the exposure accuracy is improved, and a fine pattern can be formed with high accuracy. Further, since the scanning direction is reversed between the first scanning exposure and the second scanning exposure, the time required for processing can be reduced as compared with the case where scanning exposure is performed in the same direction, and the difference in the scanning direction can be reduced. For example, a constant error based on the stage feed accuracy and the like is averaged, and a highly accurate pattern with little variation between device patterns can be formed.

Further, the transfer position of the pattern image is shifted in the scanning direction (second direction) so that a part of the image of the pattern of the mask overlaps between the first scanning exposure and the second scanning exposure. Therefore, it is possible to freely adjust the line width of the device pattern according to the deviation amount, and it is possible to form a device pattern having a line width smaller than the line width of the projected image of the mask pattern on the photosensitive substrate. It becomes possible.

In the above arrangement, the exposure amounts given to the photosensitive substrate in the first and second scanning exposures are respectively:
It can be smaller than an appropriate value according to the sensitivity characteristics of the photosensitive substrate. In this way, the device pattern to be formed on the photosensitive substrate is divided so as not to overlap with each other, and each of the divided patterns is exposed at an appropriate exposure amount. Since the speed can be increased, the processing can be accelerated, and a light source having a relatively low output can be adopted, and the cost of the apparatus can be reduced.

The exposure conditions including the respective illumination conditions and the like in the first and second scanning exposures are not particularly limited, and may be the same or different.
The sum of the exposure amounts given to the photosensitive substrate by the first and second scanning exposures can be set so as to be an appropriate value according to the sensitivity characteristics of the photosensitive substrate. In this case, the first and second scanning exposures can be performed. The exposure amount given to the photosensitive substrate by each of the two scanning exposures can be set substantially equal to each other.

[0053]

Embodiments of the present invention will be described below with reference to the drawings.

First, a projection exposure apparatus according to an embodiment of the present invention will be described with reference to FIG. FIG. 1 shows a schematic configuration of a step-and-scan type projection exposure apparatus using a catadioptric system as a projection optical system.

In FIG. 1, an illumination light IL composed of a pulse laser beam emitted from an excimer laser light source 2 whose light emission state is controlled by an exposure control device 1 is deflected by a deflecting mirror 3 to a first illumination system 4. Reach. In this example, a KrF excimer laser (wavelength 2
48 nm) laser light source is used. However, as an exposure light source, an ArF excimer laser (wavelength 193n) was used.
m), or F ₂ laser (may use a laser light source of wavelength 157 nm), a metal vapor laser light source, a harmonic generator of YAG laser, or may be used bright line lamp such as a mercury lamp.

The projection optical system PL according to the present embodiment is a catadioptric system in which a plurality of reflective optical elements including a concave mirror having a reflective surface processed with an aspheric surface and a mirror and a refractive optical element such as a lens are used. Although it is an optical system (catadioptric system), a projection optical system including only a plurality of refractive optical elements may be used.

The first illumination system 4 includes a beam expander,
It includes a light amount variable mechanism, an illumination switching mechanism for switching the amount of illumination light when the coherence factor (so-called σ value) of the illumination optical system is changed, a fly-eye lens, and the like. Then, the illumination light IL is applied to the exit surface of the first illumination system 4.
A secondary light source distributed in a plane is formed, and a switching revolver 5 for an illumination system aperture stop for variously switching illumination conditions is disposed on a surface on which the secondary light source is formed. On the side surface of the switching revolver 5, a normal circular aperture stop, a so-called deformed illumination aperture stop having a plurality of apertures eccentric from the optical axis, a ring-shaped aperture stop, and a small σ value having a small circular aperture are provided. An aperture stop or the like is formed, and the switching device 6
By rotating the switching revolver 5 through the illuminator, a desired illumination system aperture stop can be arranged on the exit surface of the first illumination system 4. Further, when the illumination system aperture stop is switched in such a manner, the illumination switching mechanism in the first illumination system 4 is switched by the switching device 6 so that the light amount becomes largest.

The operation of the switching device 6 is similar to that of the exposure control device 1.
The operation of the exposure control apparatus 1 is controlled by a main controller 7 that controls the overall operation of the apparatus.

The illumination light IL transmitted through the illumination system aperture stop set by the switching revolver 5 is incident on a beam splitter 8 having a large transmittance and a small reflectance, and the illumination light reflected by the beam splitter 8 is converted into a photo. The light is received by an integrator sensor 9 including a photoelectric detector such as a diode. A detection signal obtained by photoelectrically converting the illumination light by the integrator sensor 9 is supplied to the exposure control device 1. The relationship between the detection signal and the exposure amount on the wafer is measured and stored in advance, and the exposure control device 1 monitors the integrated exposure amount on the wafer from the detection signal. The detection signal is also used to normalize output signals of various sensor systems using the illumination light IL for exposure.

The illumination light IL transmitted through the beam splitter 8
Illuminates an illumination field stop system (reticle blind system) 11 via a second illumination system 10. This illumination field stop system 1
The arrangement surface 1 is conjugate with the entrance surface of the fly-eye lens in the first illumination system 4, and the illumination field stop system 11 is illuminated in an illumination area substantially similar to the cross-sectional shape of each lens element of the fly-eye lens. You. The illumination field stop system 11 is divided into a movable blind and a fixed blind, and the fixed blind is a field stop having a fixed rectangular opening. Are two pairs of movable blades. The fixed blind determines the shape and size (width) of the illumination area on the reticle, and the movable blind gradually opens and closes the covering of the fixed blind at the start and end of scanning exposure. Is performed. As a result, it is possible to prevent the area other than the original shot area on the wafer from being irradiated with the illumination light.

The operation of the movable blind in the illumination field stop system 11 is controlled by a drive unit 12. When the stage control unit 13 performs synchronous scanning of a reticle and a wafer as described later, the stage control unit 13
Drives the movable blind in the scanning direction in synchronization with the driving device 12. The illumination light IL that has passed through the illumination field stop system 11 illuminates a rectangular illumination area 15 on the pattern surface (lower surface) of the reticle R with a uniform illumination distribution via a third illumination system 14. The arrangement surface of the movable blind of the illumination field stop system 11 is conjugate with the pattern surface of the reticle R, and the fixed blind is arranged away from the conjugate surface in the direction of the optical axis (defocused). The shape of 15 is defined by the opening of its fixed blind.

In the following, the X axis is taken perpendicular to the plane of FIG. 1 in the plane parallel to the pattern plane of the reticle R, the Y axis is taken parallel to the plane of FIG. 1, and the Z axis is taken perpendicular to the pattern plane of the reticle R. Take and explain. At this time, the illumination area 1 on the reticle R
5 is a rectangular area long in the X direction.
Reticle R is in the + Y direction or -Y with respect to illumination area 15
Scan in the direction. That is, the scanning direction is set in the Y direction.

The pattern in the illumination area 15 on the reticle R is projected through a telecentric projection optical system PL on both sides (or one side on the wafer side) to a projection magnification β (β is, for example, 1/4,
(1/5, etc.), and image-formed and projected on an exposure area 16 on the surface of the wafer W coated with the photoresist. In addition,
The specific configuration of the projection optical system PL in FIG. 1 is disclosed in, for example, Japanese Patent Application Laid-Open No. 9-246140.

Reticle R is held on reticle stage 17, and reticle stage 17 is mounted on reticle support 18.
It is mounted on an upper guide extending in the Y direction via an air bearing. The reticle stage 17 can scan the reticle support base 18 in the Y direction at a constant speed by a linear motor, and has an adjustment mechanism that can adjust the position of the reticle R in the X direction, the Y direction, and the rotation direction (θ direction). . A moving mirror 19m fixed to the end of the reticle stage 17 and a laser interferometer (not shown except for the Y axis) 19 fixed to a column (not shown) use the moving mirror 19m and the X direction of the reticle stage 17 (reticle R). The position in the direction is always measured with a resolution of about 0.001 μm, the rotation angle of the reticle stage 17 is also measured, and the measured value is supplied to the stage control device 13. The stage control device 13 responds to the supplied measured value. Thus, the operation of a linear motor or the like on the reticle support 18 is controlled.

On the other hand, the wafer W is held on a sample table 21 via a wafer holder 20, the sample table 21 is mounted on a wafer stage 22, and the wafer stage 22 is
It is mounted on the upper guide via an air bearing. The wafer stage 22 is configured to perform scanning and stepping movement at a constant speed in the Y direction on the surface plate 23 by a linear motor, and to perform stepping movement in the X direction. Further, a Z stage mechanism for moving the sample table 21 in a predetermined range in the Z direction and a tilt mechanism (leveling mechanism) for adjusting the tilt angle of the sample table 21 are incorporated in the wafer stage 22.

Moving mirror 2 fixed to the side of sample stage 21
The position of the sample table 21 (wafer W) in the X and Y directions is always 0.001 μm by a laser interferometer (not shown except for the Y axis) 24 fixed to a column (not shown) and 4 m.
At the same time, the rotation angle of the sample table 21 is measured. The measured value is supplied to the stage control device 13, and the stage control device 13 controls the operation of the linear motor for driving the wafer stage 22 and the like according to the supplied measured value.

At the time of scanning exposure, an exposure start command is sent from the main controller 7 to the stage controller 13. In response to this, the stage controller 13 moves the reticle R via the reticle stage 17 in the Y direction at a speed V 2. In synchronization with the scanning, the wafer W is scanned through the wafer stage 22 in the Y direction at a speed Vw. Reticle R to wafer W
The scanning speed Vw of the wafer W is β
-Set to V2.

The projection optical system PL is held in an upper plate of a U-shaped column 25 planted on the surface plate 23. Then, a slit image or the like is projected obliquely to a plurality of measurement points on the surface of the wafer W on the side surface of the projection optical system PL in the X direction, and the positions (focus positions) in the Z direction at the plurality of measurement points are set. Output a plurality of corresponding focus signals,
Oblique incidence multi-point auto focus sensor (hereinafter, referred to as
An “AF sensor” 26 is disposed. A plurality of focus signals from the multi-point AF sensor 26 are supplied to a focus / tilt control device 27, and the focus / tilt control device 27 obtains a focus position and a tilt angle of the surface of the wafer W from the plurality of focus signals. ,
The obtained result is supplied to the stage control device 13.

The stage controller 13 adjusts the focus position and the tilt angle of the wafer stage 22 so that the supplied focus position and the tilt angle match the focus position and the tilt angle of the imaging plane of the projection optical system PL, which are obtained in advance. The Z stage mechanism and the tilt mechanism are driven by a servo system. Thereby, even during the scanning exposure, the exposure region 1 of the wafer W is
The surface in 6 is controlled by the autofocus method and the autoleveling method so as to match the image forming plane of the projection optical system PL.

Further, an off-axis type alignment sensor 28 is fixed to a side surface of the projection optical system PL in the + Y direction.
The position detection of the alignment wafer mark attached to each shot area of the wafer W is performed by 8, and a detection signal is supplied to the alignment signal processing device 29.
The measured value of the laser interferometer 24 is also supplied to the alignment signal processor 29, and the alignment signal processor 29 calculates the stage coordinate system (X, Y) of the wafer mark to be detected from the detection signal and the measured value of the laser interferometer 24. ) Is calculated and supplied to the main controller 7. The stage coordinate system (X, Y) refers to a coordinate system determined based on the X and Y coordinates of the sample table 21 measured by the laser interferometer 24. The main controller 7 obtains array coordinates in the stage coordinate system (X, Y) of each shot area on the wafer W from the coordinates of the supplied wafer mark, and supplies the coordinates to the stage controller 13. Controls the position of the wafer stage 22 when scanning exposure of each shot area is performed based on the supplied array coordinates.

The reference mark member F is placed on the sample table 21.
M is fixed, and on the surface of the reference mark member FM, various reference marks serving as a position reference of the alignment sensor, a reference reflection surface serving as a reference of the reflectance of the wafer W, and the like are formed. At the upper end of the projection optical system PL, a reflected light detection system 30 for detecting a light beam or the like reflected from the wafer W via the projection optical system PL is attached.
Is supplied to the self-measuring device 31. Under the control of the main controller 7, the self-measuring device 31 monitors the amount of reflection (reflectance) of the wafer W, measures illuminance unevenness, measures an aerial image, and the like.

Under the control of the stage controller 13, the reticle R is positioned at a predetermined illumination position (initial scanning position). In this state, the excimer laser light source 2 controls the excimer laser light source 2 under the control of the exposure control device 1 in relation to the field of view of the illumination field stop system 11 so that the substantial exposure amount on the wafer W becomes an appropriate exposure amount. Scanning exposure is performed by irradiating pulse laser light at the oscillation frequency and moving the wafer W and the reticle R relative to each other at an appropriate speed under the control of the stage controller 13.

FIGS. 2A and 2B and FIGS. 3A and 3B show a case where a dense pattern (L / S) and an isolated pattern having a periodicity are formed as device patterns.
Description will be made with reference to (A) and (B). Note that FIG.
3A and 3A show a reticle pattern formed on a reticle, in which a colored portion is a light-shielding portion and an uncolored portion is a light-transmitting portion. FIGS. 2B and 3B show device patterns to be formed or formed on the wafer W. The colored portions are lines (convex portions), and the uncolored portions are spaces ( Recess).

The dense pattern 41b as shown in FIG. 2B and the isolated pattern 5 as shown in FIG.
It is assumed that a device pattern including 1b as a component is formed on a wafer W coated with a photoresist (positive resist) having predetermined sensitivity characteristics.

In this case, first, FIG. 2A or FIG.
The reticle R on which the reticle pattern is formed as shown in FIG. The attitude of the reticle R with respect to the reticle stage 17 is set such that the extending direction (X direction, first direction) of the patterns 41a, 51a is substantially orthogonal to the scanning direction (Y direction, second direction). Next, the stage controller 13
Controls the reticle position adjusting mechanism of the reticle stage 17 to set the first reticle R at a predetermined illumination position (scanning initial position), and substantially adjusts the position of the wafer W held on the wafer stage 22 by suction. Exposure amount is wafer W
In relation to the field of view (opening width) of the illumination field stop system 11, the intensity of the excimer laser (average value), etc., the exposure amount becomes １ ／ of the appropriate exposure amount according to the sensitivity characteristic of the photoresist applied to the photoresist. The first scanning exposure is performed by appropriately selecting and adjusting one or both of the oscillation frequency and the scanning speed of the laser light from the excimer laser light source 2.

Next, by reversing the moving directions of the reticle stage 17 and the wafer stage 22, the scanning direction is reversed from the first scanning exposure, and the substantial exposure on the wafer W is performed in the same manner as described above. The second scanning exposure is performed so that the amount becomes の of the appropriate exposure amount according to the sensitivity characteristics of the photoresist applied to the wafer W.

At this time, the scan start timing of the reticle stage 17 on the wafer stage 22 in the second scan exposure is delayed or advanced from the scan start timing of the reticle stage 17 on the wafer stage 22 in the first scan exposure. Accordingly, the relative positional relationship between the reticle R and the wafer W in the scanning direction in the second scanning exposure is shifted from the relative positional relationship between the reticle R and the wafer W in the scanning direction in the first scanning exposure. As a result, the position of the projection image formed by the first scanning exposure on the wafer W and the position of the projection image formed by the second scanning exposure in the scanning direction are shifted (shifted). Are exposed with an appropriate exposure amount, and the overlapping portion (overlapping portion) becomes a device pattern.

That is, as shown in FIG. 2 or FIG. 3, the line width of the reticle pattern 41a or 51a is set to LW.
R, the device pattern 41 to be formed on the wafer W
When the line widths of b and 51b are set to LWW, the position of the reticle R at the time of the second scanning exposure is shifted by (LWR-LWW) with respect to the time of the first scanning exposure, so that the position of the reticle R is changed according to the shift amount. Device patterns 41b and 51b having different line widths
Can be formed.

In the present embodiment, the relative positional relationship between the reticle R and the wafer W is shifted in the scanning direction between the first scanning exposure and the second scanning exposure, so that a fine pattern corresponding to the shift amount is obtained. Although a device pattern having a wide line width is formed, it is needless to say that the first scanning exposure and the second scanning exposure may be performed by matching the relative positional relationship without shifting. No. Although the device pattern thus formed is not shown, the reticle pattern formed on the reticle R (FIG.
The pattern has a line width substantially equal to the line width of the image projected on the wafer W by the projection optical system PL shown in FIG.

According to the present embodiment, the pattern image of the reticle R is superimposed and transferred by the two scanning exposures of the first and second scanning exposures, so that there is a certain tendency. However, random errors that occur stochastically are reduced by the averaging effect, and a fine pattern can be formed with high accuracy. In addition, in the first scanning exposure and the second scanning exposure, scanning is performed with the moving directions of the mask and the photosensitive substrate reversed.
The time required for processing can be reduced as compared with the case where the reticle R and the wafer W are moved so that the moving directions of the reticle R and the wafer W are the same in the second scanning exposure and the second scanning exposure. For example, since a constant error based on the stage feed accuracy and the like is also averaged, variations between device patterns are small, and a highly accurate pattern can be formed.

Furthermore, the transfer position of the pattern is shifted in the scanning direction so that a part of the image of the pattern of the reticle R is overlapped in the first scanning exposure and the second scanning exposure, so that the device pattern is exposed. Can be freely adjusted according to the deviation amount, and a device pattern having a line width smaller than the line width of the projected image of the pattern of the reticle R on the wafer W can be formed. . Therefore, by adjusting this shift amount, the same reticle R
Can be used to form device patterns with different line widths, and can flexibly respond to various requests for forming device patterns without changing the reticle R.

In the present embodiment, the first and second exposures of the two exposures are respectively set to の of the appropriate exposure, and from the viewpoint of reducing the random error, this is set. Although such a setting is effective, it is not always necessary that the first and second exposure doses match.
The second exposure may be greater than the second exposure, or the second exposure may be greater than the first exposure. In this case, the sum of the first and second exposures can be distributed so as to match the appropriate exposure.

In this embodiment, a single reticle R
Since the same pattern image is multiple-transferred onto the wafer W, the reticle exchange operation is not required as compared with the related art in which the exposure processing is performed a plurality of times using a plurality of reticles R, and the throughput is reduced. In addition to improving the reticle management time, there is no need to load multiple reticles on the reticle stage in consideration of shortening of the reticle exchange time, and it is possible to eliminate inconvenience such as enlargement of the stage. It is advantageous.

However, two or more types of patterns are formed on a single reticle R, and the reticle R is partially shielded from light by blinds or the like. By doing so, it is possible to improve the throughput, avoid an increase in the size of the stage, and facilitate reticle management. In this case, one pattern formed on the reticle R and another pattern can have different shapes including the line width.

In the above-described embodiment, the reticle R is arranged so that the direction in which the pattern of the reticle R extends is orthogonal to the scanning direction, and the first scanning exposure and the second scanning exposure are performed on the wafer W. Is shifted in the scanning direction by shifting the scanning start position of the reticle R, but may be shifted by shifting the scanning start position of the wafer W. Further, the image position on the wafer W may be shifted by shifting the scanning start positions of both the reticle R and the wafer W.

Further, the reticle R is arranged such that the direction in which the pattern of the reticle R extends extends along the scanning direction, and the relative positional relationship between the reticle R and the wafer W in the direction orthogonal to the scanning direction is determined by the reticle R and / or the wafer. The image position on the wafer W may be shifted in a direction orthogonal to the scanning direction by shifting the position by a position adjustment mechanism of W or the like. In addition, without changing the relative positional relationship between the reticle R and the wafer W, for example, a part of an optical element constituting the projection optical system can be moved, or an optical element for shifting the image position is inserted into the optical path. For example, the projection position of the image by the projection optical system on the surface of the wafer W may be directly shifted by, for example, configuring the projection optical system.

Further, the step-and-
In the case of a scan-type reduction projection exposure apparatus, two scanning exposures are continuously performed on one shot area on a wafer, and two scanning exposures are continuously performed while sequentially moving shots. Alternatively, the second scanning exposure may be sequentially performed after the first scanning exposure is sequentially performed on all or a part of the shot areas.

The embodiments described above are described for facilitating the understanding of the present invention, and are not described for limiting the present invention. Therefore, each element disclosed in the above embodiment is intended to include all design changes and equivalents belonging to the technical scope of the present invention.

For example, in each of the above embodiments, a desired device pattern is formed by the first and second scanning exposures. However, the present invention is not limited to this. Furthermore, a device pattern can also be formed by a plurality of (three or more) exposures. The size and shape of the pattern, the wavelength of the light source, the numerical aperture (NA) of the projection optical system, and the aperture (field stop) of the illumination optical system
The shape and the like are not limited to the above, and can be arbitrarily changed.

The conditions of the first scanning exposure and the second scanning exposure, for example, the intensity distribution of the exposure illumination light defined by the aperture stop of the revolver 5 (shape and size of the secondary light source) , A numerical aperture N.R. defined by a variable aperture stop arranged on a pupil plane of the projection optical system PL. A. , JP-A-4
-277612 and JP-A-6-314646, the presence or absence of a progressive focusing method for moving the image plane of the projection optical system PL and the wafer W in the direction along the optical axis during exposure, And an optical filter (so-called pupil filter) for changing a part of the optical characteristics (amplitude transmittance, phase, etc.) of the imaging light flux generated from the reticle pattern and distributed on the pupil plane (Fourier transform plane) of the projection optical system PL. The presence or absence may be different.

Further, the above is the projection exposure apparatus of the step-and-scan method, but the exposure apparatus to which the present invention is applied is not limited to the above-described exposure apparatus.
It can be applied to any other scanning type exposure apparatus.

[0092]

Since the present invention is configured as described above in detail, there is an effect that errors during exposure can be averaged to form a fine pattern with high accuracy. In addition, there is an effect that the processing speed of exposure can be improved and cost can be reduced. Further, there is an effect that device patterns having different line widths can be formed without replacing the mask.

[Brief description of the drawings]

FIG. 1 is a view showing an overall schematic configuration of an exposure apparatus according to an embodiment of the present invention.

FIGS. 2A and 2B are diagrams showing dense patterns according to the embodiment of the present invention, wherein FIG. 2A shows a reticle pattern and FIG. 2B shows a device pattern.

3A and 3B are diagrams showing an isolated pattern according to the embodiment of the present invention, wherein FIG. 3A shows a reticle pattern, and FIG. 3B shows a device pattern.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 exposure control device 2 excimer laser light source 11 illumination field stop system 13 stage control device 17 reticle stage 22 wafer stage R reticle W wafer IL illumination light PL projection optical system 41a, 51a reticle pattern 41b, 51b: Device pattern

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5F046 AA13 BA05 CA04 CA08 CB01 CB03 CB05 CB12 CB13 CB22 CB23 CB25 CC01 CC02 CC03 CC05 CC06 CC13 CC16 CC18 DA01 DA02 DA14 DB01 DB05 DC02 DC09 DC12 EA03 EA09 EA13 EB01 FC02 ED03

Claims (12)

[Claims] 1. An exposure method for sequentially projecting and transferring an image of a pattern formed on a mask onto a photosensitive substrate via a projection optical system by a scanning method, wherein an appropriate exposure amount according to sensitivity characteristics of the photosensitive substrate is obtained. An exposure method characterized in that an image of the same mask pattern is superimposed and transferred a plurality of times with a small amount of exposure. 2. An exposure method for sequentially projecting and transferring an image of a pattern formed on a mask onto a photosensitive substrate via a projection optical system by a scanning method, wherein an appropriate exposure amount according to the sensitivity characteristic of the photosensitive substrate is provided. An exposure method characterized in that an image of a pattern of the same mask is transferred by superposing a plurality of times by reversing the scanning direction with a small amount of exposure. 3. The exposure method according to claim 1, wherein an image position of the pattern of the mask on the photosensitive substrate is shifted between successive ones of the plurality of transfers. . 4. The exposure method according to claim 3, wherein the image position is shifted by making a scanning start position of at least one of the mask and the photosensitive substrate different between successive transfer operations. 5. The method according to claim 1, wherein a total of exposure amounts given to the photosensitive substrate by the plurality of transfer operations is an appropriate exposure amount according to sensitivity characteristics of the photosensitive substrate.
Exposure method according to 1. 6. The exposure method according to claim 5, wherein an exposure amount given to the photosensitive substrate by each of the plurality of transfers is substantially equal to each other. 7. An exposure apparatus for sequentially projecting and transferring an image of a pattern formed on a mask onto a photosensitive substrate via a projection optical system by a scanning method, comprising: a mask stage for holding the mask; A substrate stage for holding, an illumination optical system for illuminating the mask, a projection optical system for projecting an image of a pattern of the mask onto the photosensitive substrate, and synchronizing the mask and the photosensitive substrate with respect to the projection optical system A driving device for driving the mask stage and the substrate stage so as to move; and a plurality of images obtained by reversing a scanning direction of the image of the pattern of the mask with an exposure amount smaller than an appropriate exposure amount according to the sensitivity characteristic of the photosensitive substrate. An exposure device, comprising: a control device for performing control so as to perform projection transfer by overlapping. 8. An exposure method for forming a device pattern extending along a first direction on the photosensitive substrate by performing multiple exposure of the photosensitive substrate with illumination light, wherein the mask is moved relative to the illumination light. A first scanning exposure that synchronously moves the photosensitive substrate in a second direction orthogonal to the first direction; and a first scanning exposure that synchronously moves the mask and the photosensitive substrate in a direction opposite to that in the first scanning exposure. An exposure method, wherein a transfer position of an image of the pattern is shifted in the second direction so that a part of an image of the pattern of the mask overlaps on the photosensitive substrate in the two-scan exposure. 9. The method according to claim 8, wherein the exposure amount given to the photosensitive substrate in each of the first and second scanning exposures is smaller than an appropriate value according to a sensitivity characteristic of the photosensitive substrate. Exposure method. 10. The device according to claim 1, wherein the same pattern on the mask is used in the first and second scanning exposures, and the device pattern is formed on a portion of the photosensitive substrate where an image of the same pattern overlaps. The exposure method according to claim 8 or 9, wherein 11. An illumination system for irradiating a mask with illumination light, and a photosensitive substrate is subjected to multiple exposures with the illumination light through the mask to form a device pattern extending along a first direction on the photosensitive substrate. In order to scan and expose the photosensitive substrate with the illumination light, the exposure substrate performs a second movement perpendicular to the first direction in synchronization with the relative movement of the mask with respect to the illumination light. A stage system that moves in the direction, at the time of the first scanning exposure and at the time of the second scanning exposure, moves the mask and the photosensitive substrate in opposite directions, and forms an image of the pattern of the mask on the photosensitive substrate. An exposure apparatus, comprising: a control device that controls driving of the stage system so that a transfer position is shifted in the second direction so as to overlap a part of the image of the pattern. 12. The first and second masks so that a superimposed portion of an image of the pattern of the mask becomes the device pattern.
The exposure apparatus according to claim 11, further comprising an exposure amount control device configured to reduce an exposure amount given to the photosensitive substrate by scanning exposure to a value smaller than an appropriate value according to sensitivity characteristics of the photosensitive substrate. .