JPH11233434A - Exposure condition determining method, exposure method, aligner, and manufacture of device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable stably to obtain an optimum exposure condition with high precision, by changing the quantity of exposure energy in the row direction and the focusing position in the column direction, the row direction and the column direction being orthogonal to each other on a measuring induction substrate, and then finding the matching degree of each transfer pattern for each partitioned region. SOLUTION: A reticle R is irradiated with an exposure illuminating light IL of exposure energy I, and a wafer W is arranged at a position Z in the direction of optical axis AX of a projection optical system. A measuring pattern PR formed on the reticle R is transferred onto the wafer W by carrying out exposure under conditions having various combinations of the exposure energy I and the focusing position Z. Next, each pattern PW transferred on the wafer W under each exposure condition is measured and pattern matching a template pattern is carried out. A coefficient of correlation is found for each exposure condition and distribution of each coefficient of correlation thus found in the two-dimensional coordinate is found. On the basis of a pattern formed by a coordinate value in the two-dimensional coordinate to be a threshold value of a coefficient of correlation C, an optimum exposure condition is found.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure condition determining method, an exposure method, an exposure apparatus, and a device manufacturing method, and more particularly, to an exposure condition for transferring a pattern formed on a mask to a sensitive substrate. Condition determination method for determining the exposure, an exposure method for performing exposure under the exposure condition determined by the exposure condition determination method, an exposure apparatus to which the exposure method is applied, and a device such as a semiconductor element using the exposure method And a method for producing the same.

[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 (hereinafter, referred to as a “reticle pattern”) formed on a mask or a reticle (hereinafter, collectively referred to as a “reticle”). An exposure apparatus is used to transfer the wafer (hereinafter referred to as “sensitive substrate or wafer”) onto a substrate such as a wafer or a glass plate coated with a resist or the like via a projection optical system.
This type of apparatus includes a stepping operation in which a wafer stage on which a wafer as a sensitive substrate is mounted is moved in a two-dimensional direction by a predetermined amount and positioned at a predetermined exposure position, and a reticle pattern is projected in the positioning state by projection optics. A static exposure type (also called a step-and-repeat type) reduction projection type exposure apparatus (so-called “stepper”) that repeats an exposure operation for transferring to a shot area on a sensitive substrate via a system, While illuminating a predetermined slit-shaped area on the reticle with illumination light, the reticle and the wafer are synchronously moved in a predetermined scanning direction with respect to the projection optical system, and the reticle pattern is sequentially projected on the wafer via the projection optical system. 2. Description of the Related Art A step-and-scan scanning exposure apparatus for transferring images has been put to practical use.

In exposure by this type of exposure apparatus, the energy amount (exposure dose) of exposure light applied to a region to be exposed on a wafer, the image surface of a reticle pattern to be transferred at the time of exposure, and the surface of the wafer. Positional relationship with the area to be exposed,
That is, it is known that the shape of the pattern transferred to the wafer changes due to the focus error of the area to be exposed on the wafer. That is, if the exposure dose is small, the region on the wafer to be exposed is not sufficiently exposed, and if the exposure dose is large, the region on the wafer that is not to be exposed is exposed. Further, when the exposure area on the wafer does not coincide with the image plane of the reticle pattern (not within the depth of focus of the image plane of the reticle pattern related to the projection optical system), that is, when there is a focus error, The reticle pattern image formed in the exposed area is blurred, and a faithful reduced image of the reticle pattern cannot be transferred onto the wafer. Therefore, in transferring a faithful reduced image of the reticle pattern onto the wafer, it is necessary to perform exposure while optimizing the exposure dose and the focus control position (hereinafter, referred to as “focus position”) of the wafer.

Conventionally, such optimum exposure conditions are detected by using a predetermined reticle pattern (for example, a line and space pattern) as a test pattern, and using the test pattern with various exposure doses and various wafer focus positions. This is performed by performing test exposure on the test wafer and visually determining the state of the pattern transferred to the test wafer. That is, the exposure dose and the focus position of the wafer that were subjected to the test exposure visually determined to be the best transfer state were set as the best exposure conditions, or the presence or absence of a transfer pattern was visually determined, and the exposure determined to be the transfer pattern was determined. The middle point of the dose amount range and the middle point of the wafer focus position range are used as the exposure dose amount and the wafer focus position as the best exposure conditions.

[0005]

In the above-described conventional method for determining the exposure condition, the result of the test exposure is visually determined, and thus has the following inconvenience.

That is, in the method of determining the exposure condition for obtaining the best exposure condition from the test exposure visually determined to be the best transfer condition, when the test exposure condition is roughly set, the best transfer condition is determined from the test exposure. Is easy to find, but the obtained best exposure condition could not be accurately obtained. On the other hand, when the test exposure conditions are set finely, first, the time required for the test exposure becomes long, and the productivity is deteriorated. Furthermore, it is expected that there will be many candidates for the best exposure condition, and it has been difficult to determine the best exposure condition stably and accurately by visual judgment by a person.

In the method of determining the best exposure condition from the middle point of the exposure dose range where the transfer pattern is visually determined to be present and the middle point of the focus position range of the wafer, the test exposure condition is roughly set. In such a case, it is easy to determine the presence or absence of a transfer pattern from the test exposure, but since the true boundary of the presence or absence of the transfer pattern is not guaranteed to be the test exposure condition, the best exposure condition is accurately determined. I couldn't do that. On the other hand, when the test exposure conditions are set finely, first, the time required for the test exposure becomes long, and the productivity is deteriorated. Furthermore, it is difficult to determine the boundary of the presence or absence of a transfer pattern, and
In addition, it is difficult to accurately determine the best exposure condition.

The present invention has been made under such circumstances, and a first object of the present invention is to provide an exposure condition determining method capable of stably and accurately obtaining an optimum exposure condition. .

It is a second object of the present invention to provide an exposure method capable of reliably realizing high-precision exposure under the best exposure conditions.

A third object of the present invention is to provide an exposure apparatus capable of reliably realizing highly accurate exposure under the best exposure conditions.

A fourth object of the present invention is to provide a method for manufacturing a highly integrated device.

[0012]

According to a first aspect of the present invention, a mask (R) is irradiated with illumination light for exposure, and a pattern formed on the mask (R) is projected onto a projection optical system (PL).
And a method of determining exposure conditions for transferring to a sensitive substrate (W) through a matrix, comprising a matrix direction having a row direction and a column direction orthogonal to each other on a surface to be exposed of a sensitive substrate for measurement (W _T ). Regarding a virtual partitioned area, for the same row, the measurement sensitive substrate (W _T ) is connected to the projection optical system (PL).
At the same position in the direction of the optical axis, the exposure energy amount is monotonically changed in the row direction, the same exposure energy amount is set in the same column, and the measurement sensitive substrate (W _T ) is set in the column direction. A first step of monotonically changing the position in the optical axis direction and transferring a measurement pattern formed on a measurement mask to each of the divided areas; and a step of transferring the sensitive substrate (W) to which the pattern has been transferred in the first step. _T ), and developing a transfer pattern formed on the developed sensitive substrate (W _T ); and a transfer pattern of each of the divided areas detected in the second step. A third step of pattern matching with the template pattern obtained; and a fourth step of obtaining the best exposure condition based on the result of the pattern matching in the third step. No.

In the exposure condition determining method according to the first aspect, first,
In a two-dimensional coordinate system in which a row direction and a column direction orthogonal to each other on the measurement-sensitive substrate are axial directions, the amount of exposure energy is changed in the row direction, and the projection optical system of the measurement-sensitive substrate is changed in the column direction. The position in the optical axis direction, that is, the focus position of the measurement-sensitive substrate is monotonously changed, and the measurement pattern formed on the measurement mask is converted into a virtual partitioned area arranged in a matrix on the measurement-sensitive substrate. Transfer (first step). As a result, the change in the exposure energy amount as the exposure condition is reflected in the row direction,
In addition, test exposure under various test exposure conditions in which a change in the focus position of the measurement-sensitive substrate as an exposure condition is reflected in the column direction is performed for each partitioned area on one measurement-sensitive substrate.

Next, the test-exposed sensitive substrate for measurement is developed, and a pattern (transfer pattern) transferred to each of the divided areas on the sensitive substrate for measurement is detected (second step). A pattern matching is performed between each of the obtained transfer patterns and a template pattern prepared in advance, and a matching degree (correlation degree between two patterns) is obtained for each of the divided areas (third step). That is, the transfer state of each section area is obtained by an objective and quantitative method of pattern matching, not by a sensual method such as human visual observation. Then, the best exposure condition is obtained based on the result of the pattern matching obtained objectively and quantitatively for each of the divided areas (fourth step).

Therefore, according to the exposure condition determination method of the present invention, the best exposure condition can be obtained stably and accurately without making the test exposure condition unnecessarily fine.

According to a second aspect of the present invention, in the exposure condition determining method according to the first aspect, each of the divided areas has the same shape, and a difference between exposure energy amounts between the adjacent divided areas in the row direction is equal to or smaller than that. It is the same.

According to this, since a quantitative pattern matching result can be obtained with the exposure energy having the same interval width, the process for deriving the best exposure condition in the fourth step becomes easy.

According to a third aspect of the present invention, in the exposure condition determining method according to the first aspect, each of the divided areas has the same shape, and the position in the optical axis direction between the adjacent divided areas in the column direction. Are characterized by the same difference.

According to this, a quantitative pattern matching result can be obtained in which the focus positions of the measuring sensitive substrate are equally spaced in width, so that in deriving the best exposure condition in the fourth step, processing is facilitated. Become.

In the exposure condition determination method of the first aspect, various measurement patterns formed on the measurement mask can be considered. For example, as in the invention according to the fourth aspect, the measurement pattern is replaced with the measurement mask. 6. A periodic pattern formed over the entire irradiation area of the exposure illumination light of ( _RT ), or the measurement pattern may be replaced with the measurement mask as in the invention according to claim 5. (R _T ) may be a periodic pattern formed in a part of the irradiation area of the exposure illumination light. Here, the irradiation area of the illumination light for exposure of the measurement mask is an area to which the illumination light for exposure is simultaneously irradiated. That is, in the case of the step-and-repeat method, it is an area where the pattern transferred to the sensitive substrate can be formed on the mask, and in the case of the step-and-scan method, it is the same as the above-mentioned slit-like area. Become.

According to the exposure condition determining method of the present invention, pattern matching is performed over the entirety of the shot area of the sensitive substrate in accordance with the irradiation area of the exposure light of the measurement mask, so that each position in the shot area can be determined. Can be determined for the best exposure condition.

According to the exposure condition determining method of the present invention, since the amount of calculation for pattern matching can be reduced, a pattern matching result can be obtained at high speed, and the exposure condition can be determined at high speed.

In the exposure condition determining method according to the fifth aspect, as in the sixth aspect of the present invention, irradiation of the exposure illumination light on which the measurement pattern of the measurement mask ( _RT ) is formed. Part of the region can be two or more minute regions having different distances from the center point of the irradiation region. According to this, by performing pattern matching on two or more minute regions having different distances from the center point of the shot region, it is possible to obtain the best exposure condition at a position corresponding to these minute regions. Therefore, the image plane of the mask pattern is obtained for each micro area from the obtained best exposure condition, and the focus control position for the shot area can be determined from these.

In the exposure condition determination method of the first aspect, the configuration of the template pattern can be variously considered. For example, as in the invention of the seventh aspect, the template pattern is selected from one of the divided areas. Alternatively, the template pattern may be formed based on the measurement pattern and the projection magnification of the projection optical system (PL). The calculated pattern can also be used. Alternatively, as in the invention described in claim 9, the template pattern may be a pattern consisting of only one of maximum brightness and minimum brightness.

According to the exposure condition determining method of the present invention, since it is not necessary to prepare a template pattern by calculation or the like in advance, the state of the transfer pattern can be easily subjected to pattern matching. In selecting the template pattern, the transfer pattern of the section area in which the state of the transfer pattern is considered to be the best is to be visually checked by a human. After this template pattern is selected, a statistical operation called pattern matching is performed.
Since the exposure condition is determined based on the result, the subjective factor of the selector in selecting the template pattern is eliminated, and the best exposure condition can be obtained stably and accurately.

According to the exposure condition determination method of the present invention, since the template pattern is a pattern calculated based on the measurement pattern and the projection magnification of the projection optical system, any subjective element is eliminated. Since the exposure condition is determined by the above, the best exposure condition can be obtained stably and accurately.

According to the exposure condition determining method of the ninth aspect, the template pattern is a pattern consisting of only one of the maximum brightness and the minimum brightness.
As in the case of the exposure condition determination method described above, the exposure condition can be determined without any subjective elements, and no calculation is required for creating the template pattern. Furthermore, in the case of the exposure condition determination method according to the eighth aspect, it is possible to avoid a sudden change in the pattern matching result due to the exposure condition, so that the skill of the operator such as setting a threshold value when obtaining the best exposure condition is required. Can be reduced.

In the exposure condition determination method of the first aspect, there are various possible best exposure conditions to be determined, but as in the invention of the tenth aspect, the best exposure condition is determined by changing the best focus position in the optical axis direction. At least one of the condition regarding the best exposure energy amount.

According to an eleventh aspect of the present invention, a mask (R) is irradiated with illumination light for exposure, and a pattern formed on the mask (R) is exposed to a sensitive substrate (W) via a projection optical system (PL). 2. An exposure method for transferring to an image, the method comprising:
A step of setting the best exposure condition determined by the exposure condition determination method according to any one of (1) to (4); and projecting the pattern formed on the mask (R) under the set exposure condition using a projection optical system (PL). ) And transferring to a sensitive substrate (W).

According to this, the pattern formed on the mask is transferred to the sensitive substrate via the projection optical system according to the best exposure condition determined by the exposure condition determining method of the present invention. can do.

According to a twelfth aspect of the present invention, a mask (R) is irradiated with illumination light for exposure, and a pattern formed on the mask (R) is exposed via a projection optical system (PL) to a sensitive substrate (W). A driving mechanism (21) for driving the sensitive substrate (W) in the direction of the optical axis of the projection optical system (PL) and in a two-dimensional plane orthogonal thereto;
A detection system (40, 42) for detecting the position of the sensitive substrate in the optical axis direction, and monitoring the detection result of the detection system (40, 42) through the drive mechanism (21) while monitoring the detection result; A focus adjustment system (19, 40, 42) for adjusting the optical axis position of the substrate (W) to a predetermined target position; and a light intensity variable mechanism (1, 3) for changing the intensity density of the exposure illumination light. And a storage device (29) for storing the best exposure condition determined by the exposure condition determination method according to claim 1, which is performed using the drive mechanism (21) and the light intensity variable mechanism (1, 3). At least one of the target position of the focus adjustment system (19, 40, 42) and the light intensity variable mechanism (1, 3) so that the best exposure condition stored in the storage device (29) is obtained. And an adjusting device (20) for adjusting. .

In the exposure apparatus of the twelfth aspect, a driving mechanism,
Using a focus adjustment system, and a light intensity variable mechanism, regarding a matrix-like virtual partitioned region having a row direction and a column direction orthogonal to each other on the exposed surface of the measurement-sensitive substrate, for the same row, The sensitive substrate for measurement is located at the same position in the optical axis direction of the projection optical system, the exposure energy is monotonously changed in the row direction, the same exposure energy is used for the same column, and the same amount of exposure energy is used for the column direction. The measurement pattern formed on the measurement mask is transferred to each of the divided areas while the position in the optical axis direction is monotonously changed. Next, the best exposure condition obtained based on the transfer result for each of these partitioned areas and the pattern matching result between the template and the template pattern prepared in advance is stored in the storage device. And
The adjustment device adjusts at least one of the target position of the focus adjustment system and the light intensity variable mechanism so that the best exposure condition stored in the storage device is obtained, and exposes the sensitive substrate.

Therefore, according to the exposure apparatus of the twelfth aspect, the exposure condition determination method of the first aspect can be supported, and the exposure apparatus formed on the mask under the best exposure condition determined by the exposure condition determination method of the first aspect. Since the pattern is transferred to the sensitive substrate via the projection optical system, the sensitive substrate can be accurately exposed.

According to a thirteenth aspect of the present invention, there is provided a device manufacturing method including an exposure step using the exposure method according to the eleventh aspect.

According to this, since the exposure method of claim 11 is used, high-precision exposure is performed under the best exposure condition accurately obtained by the exposure condition determination method of any one of claims 1 to 10. Thus, a highly integrated device can be manufactured.

[0036]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of an exposure apparatus and an exposure method according to the present invention will be described below with reference to FIGS.

FIG. 1 shows an exposure apparatus 10 according to one embodiment.
0 is shown schematically. This exposure apparatus 100
Is a so-called step-and-scan exposure type projection exposure apparatus.

The exposure apparatus 100 holds an illumination system 10 for emitting illumination light for exposure, a reticle stage RST as a mask stage for holding a reticle R as a mask, a projection optical system PL, and a wafer W as a sensitive substrate. X
Substrate table 18 that moves in the XY two-dimensional direction in the Y plane
And an XY stage device 14 having the same, and their control systems. The control system includes a main control device 20 as an adjusting device and a storage device 29 for storing exposure conditions.

FIG. 2 is a diagram for explaining an example of a specific configuration of the illumination system 10. As shown in FIG. As shown in FIG.
The illumination system 10 includes an excimer laser light source 1, a beam shaping optical system 2, an energy rough adjuster 3, a fly-eye lens 4, an illumination system aperture stop plate 5, a beam splitter 6, a first relay lens 7A, and a second relay lens 7B. , Fixed reticle blind 8A, movable reticle blind 8B, and the like.

Here, the components of the illumination system 10 will be described. As the excimer laser light source 1, Kr
F excimer laser light source (oscillation wavelength 248 nm), ArF
Excimer laser light source (oscillation wavelength 193 nm) or F ₂
An excimer laser light source (oscillation wavelength: 157 nm) or the like is used. Instead of the excimer laser light source 1, a pulse light source such as a metal vapor laser light source or a harmonic generator of a YAG laser may be used as the exposure light source.

The beam shaping optical system 2 changes the cross-sectional shape of the laser beam LB pulsed from the excimer laser light source 1 so that the laser beam LB is efficiently incident on the fly-eye lens 4 provided behind the optical path of the laser beam LB. The shaping is performed by, for example, a cylinder lens and a beam expander (both not shown).

The energy rough adjuster 3 is arranged on the optical path of the laser beam LB behind the beam shaping optical system 2, and here, a plurality of light sources having different transmittances (= 1−dimming ratio) are provided around the rotating plate 31. (For example, only two ND filters 32A and 32D are shown in FIG. 1), and the rotating plate 31 is rotated by a drive motor 33 to make the light incident. The transmittance for the laser beam LB to be switched can be switched from 100% in a geometric progression in a plurality of steps. Drive motor 33
Is controlled by the main controller 20. In addition, a fine modulator of a double grating system or a fine energy modulator for adjusting the crossing angle of two optical filters can be arranged behind the rough energy adjuster 3.

The fly-eye lens 4 is arranged on the optical path of the laser beam LB behind the energy adjuster 3, and forms a number of secondary light sources for illuminating the reticle R with a uniform illuminance distribution. Hereinafter, the laser beam emitted from the secondary light source is referred to as “pulse illumination light IL”.

An illumination system aperture stop plate 5 made of a disc-shaped member is arranged near the exit surface of the fly-eye lens 4. This illumination system aperture stop plate 5 is equiangularly spaced,
For example, an aperture stop composed of a normal circular aperture, an aperture stop composed of small circular apertures for reducing the σ value that is a coherence factor, a ring-shaped aperture stop for annular illumination, and a plurality of apertures for a modified light source method. A modified aperture stop which is eccentrically arranged (only two types of aperture stops are shown in FIG. 1) and the like are arranged. The illumination system aperture stop plate 5 is configured to be rotated by a drive device 51 such as a motor controlled by a main controller 20 as an adjustment device, which will be described later. It is selectively set on the optical path of the IL.

Pulse illumination light I behind the illumination system aperture stop plate 5
A beam splitter 6 having a small reflectance and a large transmittance is disposed on the optical path L, and a fixed reticle blind 8A and a movable reticle blind 8 are further provided on the rear optical path.
A relay optical system including the first relay lens 7A and the second relay lens 7B is arranged with B interposed therebetween.

The fixed reticle blind 8A is disposed on a plane slightly defocused from a plane conjugate to the pattern plane of the reticle R, and has a rectangular opening defining an illumination area IAR (see FIG. 4) on the reticle R. . Also,
A movable reticle blind 8B having an opening whose position and width in the scanning direction are variable is arranged near the fixed reticle blind 8A, and at the start and end of scanning exposure, the illumination area IAR is further provided via the movable reticle blind 8B. The restriction prevents unnecessary portions from being exposed.

On the optical path of the pulse illumination light IL behind the second relay lens 7B constituting the relay optical system, there is provided a bending mirror M for reflecting the pulse illumination light IL passing through the second relay lens 7B toward the reticle R. Is arranged.

The operation of the illumination system 10 configured as described above will be briefly described. The laser beam LB pulsed from the excimer laser light source 1 is applied to the beam shaping optical system 2.
, Where the cross-sectional shape is shaped so as to efficiently enter the rear fly-eye lens 4, and then enter the energy rough adjuster 3. And this energy rough adjuster 3
Laser beam LB transmitted through any one of the ND filters
Enter the fly-eye lens 4. Thereby, a large number of secondary light sources are formed at the exit end of the fly-eye lens 4. The pulse illumination light I emitted from the many secondary light sources
After passing through one of the aperture stops on the illumination system aperture stop plate 5, L reaches a beam splitter 6 having a large transmittance and a small reflectance. The pulse illumination light IL as exposure light transmitted through the beam splitter 6 is supplied to the first relay lens 7A.
After passing through the rectangular opening of the fixed reticle blind 8A and the movable reticle blind 8B after passing through, the optical path is bent vertically downward by the mirror M through the second relay lens 7B, and then held on the reticle stage RST. A rectangular illumination area IAR on the reticle R is illuminated with a uniform illuminance distribution.

On the other hand, the pulsed illumination light IL reflected by the beam splitter 6 is received by an integrator sensor 53 composed of a photoelectric conversion element via a condenser lens 52, and the photoelectric conversion signal of the integrator sensor 53 has a peak (not shown). It is supplied to the main controller 20 as an output DS via a hold circuit and an A / D converter. As the integrator sensor 53, for example, a PIN photodiode having sensitivity in the deep ultraviolet region and having a high response frequency for detecting pulse emission of the excimer laser light source 16 can be used. The output DS of this integrator sensor 53
And the illuminance (exposure amount) of the pulse illumination light IL on the surface of the wafer W are obtained in advance, and the main controller 20
Are stored in the storage device 29 attached to the storage device.

FIG. 3 shows components related to the control of the exposure amount of the illumination system 10 shown in FIG. As shown in FIG. 3, inside the excimer laser light source 1, a laser resonator 1a, a beam splitter 1b, an energy monitor 1c, an energy controller 1d, a high-voltage power supply 1e, and the like are provided. The rough energy adjuster 3 and the excimer laser light source 1 constitute a light intensity variable mechanism.

In FIG. 3, a laser beam emitted in a pulse form from a laser resonator 1a is incident on a beam splitter 1b having a high transmittance and a small reflectance, and the laser beam LB transmitted through the beam splitter 1b is It is injected outside. The laser beam LB reflected by the beam splitter 1b enters an energy monitor 1c composed of a photoelectric conversion element, and a photoelectric conversion signal from the energy monitor 1c is output via a peak hold circuit (not shown) to an output E.
S is supplied to the energy controller 1d.
The unit of the energy control amount corresponding to the output ES of the energy monitor 1c is (mJ / pulse). During normal light emission, the energy controller 1d
The power supply voltage of the high-voltage power supply 1e is feedback-controlled so that the output ES of the high-voltage power supply 1e becomes a value corresponding to the target value of energy per pulse in the control information TS supplied from the main control device 20. Also, the energy controller 1d
Energy supplied to the laser resonator 1a is converted to a high voltage power supply 1e.
The oscillation frequency is also changed by controlling the oscillation frequency.
That is, the energy controller 1 d
In accordance with the control information TS from 0, the oscillation frequency of the excimer laser light source 1 is set to the frequency specified by the main controller 20, and the energy per pulse in the excimer laser light source 1 is specified by the main controller 20. The feedback control of the power supply voltage of the high-voltage power supply 1e is performed so as to obtain the adjusted value.

Further, a shutter 1f for shielding the laser beam LB in accordance with control information from the main controller 20 is provided outside the beam splitter 1b in the excimer laser light source 1.

Returning to FIG. 1, the reticle stage RST
On top, a reticle R is fixed, for example, by vacuum suction. The reticle stage RST is two-dimensionally (in the X-axis direction and in the X-axis direction) in a plane perpendicular to the optical axis IX of the illumination optical system (coincident with the optical axis AX of the projection optical system PL described later) for positioning the reticle R. It is configured to be capable of minute driving (in the Y-axis direction orthogonal to the XY plane and in the rotation direction about the Z axis orthogonal to the XY plane).

The reticle stage RST is designated in a predetermined scanning direction (here, the Y-axis direction) on a reticle base (not shown) by a reticle driving unit (not shown) composed of a linear motor or the like. It can be moved at different scanning speeds. This reticle stage RST is
The entire surface of the reticle R has a moving stroke that can at least cross the optical axis IX of the illumination optical system.

A movable mirror 15 for reflecting a laser beam from a reticle laser interferometer (hereinafter referred to as a “reticle interferometer”) 16 is fixed on the reticle stage RST. Is, for example, 0.5 to 1 nm by the reticle interferometer 16.
It is always detected with a resolution of the order. Here, in practice, a moving mirror having a reflecting surface orthogonal to the scanning direction (Y-axis direction) on the reticle stage RST and a non-scanning direction (X-axis direction)
And a reticle interferometer 16 is provided with one axis in the scanning direction and two axes in the non-scanning direction. In FIG.
5, shown as reticle interferometer 16.

The position information of the reticle stage RST from the reticle interferometer 16 is sent to the stage control system 19 and the main controller 20 via the stage control system 19, and the stage control system 19 sends the reticle stage RST in response to an instruction from the main controller 20. R
Reticle drive unit (not shown) based on ST position information
Drives the reticle stage RST via the.

The initial position of the reticle stage RST is determined so that the reticle R is accurately positioned at a predetermined reference position by a reticle alignment system (not shown). This means that the position of the reticle R has been measured with sufficiently high accuracy.

The projection optical system PL is disposed below the reticle stage RST in FIG. 1 and its optical axis AX
The direction (coincident with the optical axis IX of the illumination optical system) is the Z-axis direction. Here, a plurality of lens elements 60a arranged at predetermined intervals along the optical axis AX direction so as to have a telecentric optical arrangement on both sides. , 60b,... Are used. The projection optical system PL is a reduction optical system having a predetermined projection magnification, for example, 1/5 (or 1/4). Therefore, the illumination light I from the illumination optical system
When the illumination region IAR of the reticle R is illuminated by L, the illumination light IL passing through the reticle R causes the reticle R in the illumination region IAR to pass through the projection optical system PL.
A reduced image (partially inverted image) of the circuit pattern is formed on the wafer W having a surface coated with a photoresist.

Of the above lens elements, the uppermost lens element 60 closest to the reticle stage RST
a is held by a ring-shaped support member 62. The support member 62 has three points by extendable drive elements, for example, piezo elements 64a, 64b, and 64c (the drive element 64c on the back side of the drawing is not shown). Supported and lens barrel 6
6. The driving elements 64a, 64b,
By 64c, three points around the lens element 60a can be independently moved in the optical axis AX direction of the projection optical system PL. That is, the lens element 60a can be translated along the optical axis AX according to the displacement of the driving elements 64a, 64b, 64c, and can be arbitrarily inclined with respect to a plane perpendicular to the optical axis AX. . Then, these drive elements 64a,
The voltages supplied to the driving elements 64a, 64b, 64c are controlled by the imaging characteristic correction controller 68 based on the command from the main controller 20.
64c is controlled. In addition,
1, the optical axis AX of the projection optical system PL coincides with the optical axes of the lens element 60b fixed to the lens barrel 66 and other lens elements (not shown).

In the present embodiment, a sealing chamber 69 is formed between specific lens elements near the center of the projection optical system PL in the optical axis direction, and the sealing chamber 69 is formed.
Is adjusted by a pressure adjusting mechanism (not shown) (for example, a bellows pump or the like). This pressure adjusting mechanism is also controlled by the imaging characteristic correction controller 68 based on a command from the main controller 20, whereby the internal pressure of the sealed chamber 69 is adjusted.

Here, the optical axis A of the lens element 60a
The magnification of the projection optical system PL can be changed or the image plane of the projection optical system PL can be changed by moving or tilting in the X direction. Further, the magnification and the imaging plane of the projection optical system PL can be changed by changing the internal pressure of the sealed chamber 69 inside the projection optical system PL.

The XY stage device 14 includes a Y stage 16 which can reciprocate in a Y-axis direction (left-right direction in FIG. 1) as a scanning direction on a base (not shown), and a Y-axis direction on the Y stage 16. The X stage 12 includes an X stage 12 that can reciprocate in an orthogonal X axis direction (a direction orthogonal to the plane of FIG. 1) and a substrate table 18 provided on the X stage 12. Further, a wafer holder 25 is placed on the substrate table 18, and the wafer W as a sensitive substrate is held by the wafer holder 25 by vacuum suction.

The substrate table 18 is mounted on the X stage 12 in such a manner that it is positioned in the X and Y directions and is allowed to move and tilt in the Z axis direction. The substrate table 18 is supported by three shafts (not shown) at three different support points, and these three shafts are independently moved in the Z-axis direction by a wafer driving device 21 as a driving mechanism. The wafer W is driven, whereby the surface position (the Z-axis direction position and the inclination with respect to the XY plane) of the wafer W held on the substrate table 18 is set to a desired state.

A movable mirror 27 for reflecting a laser beam from a wafer laser interferometer (hereinafter, referred to as a “wafer interferometer”) 28 is fixed on the substrate table 18. The position of the X.18 in the XY plane is always detected with a resolution of, for example, about 0.5 to 1 nm.

Here, actually, a moving mirror having a reflecting surface orthogonal to the Y-axis direction which is the scanning direction and a moving mirror having a reflecting surface orthogonal to the X-axis direction which is the non-scanning direction are actually provided on the substrate table 18. The wafer interferometer 28 is provided with one axis in the scanning direction and two axes in the non-scanning direction. In FIG. 1, these are representatively shown as the moving mirror 27 and the wafer interferometer 28. . The position information (or speed information) of the substrate table 18 is sent to the stage control system 19 and the main controller 20 via the stage control system 19, and the stage control system 19 sends the position information (or speed information) in response to an instruction from the main controller 20. information)
Drive 21 based on the X stage 1
2, the Y stage 16 and the X stage 12 are controlled via the Y stage 16 drive system and the substrate table 18 drive system.

Further, on the substrate table 18, there are provided various reference marks for baseline measurement for measuring the distance from the detection center of the off-axis type alignment detection system (not shown) to the optical axis of the projection optical system PL. The formed reference mark plate FM is fixed.

Further, the apparatus shown in FIG. 1 includes an exposure area IA on the surface of the wafer W (a wafer W conjugate to the illumination area IAR described above).
Upper region: see FIG. 4) which is one of oblique incident light type focus detection systems (focus detection systems) for detecting the position in the Z direction (optical axis AX direction) of the inner portion and the region in the vicinity thereof. A multipoint focus position detection system is provided. As shown in FIG. 1, the multipoint focus position detection system includes an optical fiber bundle 80, a mirror 81, a condenser lens 82, a pattern forming plate 83, a lens 84, a mirror 85, and an irradiation objective lens 8.
And a light-receiving optical system 42 including a light-collecting objective lens 87, a rotational direction vibration plate 88, an imaging lens 89, a light-receiving slit plate 98, and a light-receiving device 90 having a large number of photosensors. Have been. The detailed configuration of the multi-point focus position detection system is disclosed in, for example, Japanese Patent Application Laid-Open No. Hei 6-283403.

Here, each component of the multi-point focus position detection system (40, 42) will be described together with its operation. Illumination light having a wavelength that does not expose the photoresist on the wafer W different from the exposure light is guided through an optical fiber bundle 80 from an illumination light source (not shown). The illumination light emitted from the optical fiber bundle 80 illuminates the pattern forming plate 83 via the mirror 81 and the condenser lens 82.

A plurality of slit-like opening patterns (not shown) are formed on the pattern forming plate 83 in a matrix arrangement. The illumination light (image light flux of the opening pattern) transmitted through each slit-shaped opening pattern of the pattern forming plate 83 is supplied to the lens 84, the mirror 85 and the irradiation objective lens 8.
6, the image is projected onto the exposure surface of the wafer W, and the image of the slit-shaped opening pattern on the pattern forming plate 83 is projected and formed on the exposure surface of the wafer W. Some of these opening patterns are imaged in the exposure area IA of the wafer W (see FIG. 4), and other parts of the opening pattern are imaged outside the exposure area IA of the wafer W.

Then, the light beam reflected from the surface to be exposed of the wafer W advances in a direction inclined by a predetermined angle symmetrically with respect to the optical axis AX with respect to the image light beam from the irradiation optical system 40, and the condensing objective lens 87 , Rotation direction diaphragm 88 and imaging lens 89
Is re-imaged on the light receiving slit plate 98 disposed on the front side of the light receiver 90. The re-formed image is detected by the light receiver 90, and is synchronously detected by the signal processing device 91 via the sensor selection circuit 93 with the signal of the rotational vibration frequency. A large number of focus signals obtained by synchronous detection by the signal processing device 91 are supplied to the main control device 20.

A large number of focus signals obtained by the synchronous detection are supplied to the main controller 20. Then, main controller 20 predicts the next focus state with respect to the focus signal relating to the opening pattern formed outside of exposure area IA of wafer W, that is, in which direction the surface of wafer W is in the + Z direction or the −Z direction. It is used for prediction about the change in level or leveling. The stage control system 19 and the wafer driving device 21 perform focusing and leveling adjustment of the exposure area IA of the wafer W based on the prediction made in this way and a focus signal relating to the opening pattern formed in the illumination area IA of the wafer W. Is performed. Note that a focus adjustment system is constituted by the multipoint focus position detection system (40, 42) and the stage control system 19.

In the apparatus shown in FIG. 1, an off-illustration (not shown) comprising an imaging alignment sensor arranged on the side of the projection optical system PL and observing a position detection mark (alignment mark) formed on the wafer W is provided. An alignment microscope of the Axis system, and an image processing apparatus (not shown) for inputting the observation result of the alignment microscope and the position information of the wafer W from the wafer interferometer 28 to obtain the position of the position detection mark on the wafer W. Have. The position of the position detection mark obtained by the image processing device is supplied to the main controller 20.

In the exposure apparatus 100 of the present embodiment,
As shown in FIG. 4, the reticle R is illuminated by a rectangular (slit-shaped) illumination area IAR having a longitudinal direction perpendicular to the scanning direction (Y-axis direction) of the reticle R,
The reticle R is scanned at a speed V _R in the -Y direction during exposure (scanning). The illumination area IAR (the center substantially coincides with the optical axis AX) is projected onto the wafer W via the projection optical system PL, and a slit-shaped projection area conjugate to the illumination area IAR, that is, an exposure area IA is formed. Since the wafer W is to the reticle R in inverted imaging relationship, the wafer W is the direction of the velocity V _R is scanned at a speed V _W in synchronization with the reticle R in the opposite direction (+ Y direction), the shot on the wafer W The entire surface of the area SA can be exposed. Scan speed ratio V _W / V _R
Accurately corresponds to the reduction magnification of the projection optical system PL, and the pattern of the pattern area PA of the reticle R is accurately reduced and transferred onto the shot area SA on the wafer W. The width of the illumination area IAR in the longitudinal direction is set to be wider than the pattern area PA on the reticle R and smaller than the maximum width of the light-shielding area ST, and the entire area of the pattern area PA is illuminated by scanning. It has become so.

In the scanning type exposure apparatus 100, at the time of the above scanning exposure, the main controller 20 controls the reticle via the stage control system 19 and the wafer driving device 21 based on the detection signal of the alignment detection system (not shown). R and wafer W
Is performed, and the pattern surface of the reticle R and the surface of the wafer W are conjugated with respect to the projection optical system PL based on the detection signals of the multipoint focus position detection system (40, 42). Main controller 20 so that the image plane of projection optical system PL coincides with the surface of wafer W (the wafer surface falls within the range of the depth of focus of the best image plane of projection optical system PL). Stage control system 1
The substrate table 18 is driven and controlled in the Z-axis direction and the tilt direction via the wafer 9 and the wafer driving device 21 to adjust the surface position (set the mating surface).

Next, a description will be given of a method of determining exposure conditions for the exposure apparatus 100 described above. Prior to the description of the exposure condition determination method, an outline of the principle of detecting the best exposure condition in the present embodiment will be described with reference to FIG. As shown in FIG. 5A, the reticle R is irradiated with exposure illumination light IL having an intensity (exposure energy) I, and the wafer W
Is the optical axis AX direction of the projection optical system PL (that is, the Z direction).
At the position Z. FIG. 5B shows a conceptual diagram of a pattern (line and space mark: hereinafter, referred to as “L / S mark”) PR formed on reticle R, and FIG. FIG. 3 shows a conceptual diagram of a pattern (L / S mark) PW transferred onto the wafer W. Here, as shown in FIG.
Is assumed to be an L / S mark having a line width LR and an arrangement period of 2LR, the pattern PW transferred to the wafer W is as shown in FIG.
An L / S mark having a line width LW and an arrangement period LWP is obtained.

In an ideal exposure, if the projection magnification of the projection optical system PL is β, LW = β · LR (1) LWP = 2β · LR (2) Position Z in Z direction
When the (focus position) changes, the relationship of Expression (2) is maintained, but the line width PW of the pattern PW changes, so that the relationship of Expression (1) is not always satisfied. That is,
The line width LW is a function LW (I, Z) of the exposure energy I and the focus position Z. Therefore, (1) fulfills the relation equation, a change in exposure energy I and the focus position Z, the best exposure condition defined by (1) the smallest degree of deviation from the relationship of Formula (I _B, In order to set Z _B ), it is necessary to adjust the exposure energy I and the focus position Z.

By the way, considering the difference value | ΔL | between the line width LW transferred to the wafer W and the ideal line width LT (= β · LR), the exposure condition (I, Z) is the best exposure condition. (I _B, Z _B) increases away from. That is,
Exposure conditions (I, Z) is the best exposure condition (I _B, Z _B) away from the actual transfer pattern is away from the ideal transfer pattern. For example, when an ideal transfer pattern is used as a template pattern and pattern matching between the template pattern and an actual transfer pattern is performed, the exposure conditions (I,
As Z) departs from the best exposure condition (I _B , Z _B ), the correlation coefficient decreases.

Therefore, for example, the best exposure condition can be determined by executing the following procedure.
In brief, the measurement pattern PR formed on the reticle R is exposed to light under exposure conditions of various combinations of exposure energy I and focus position Z, and is transferred onto the wafer W. Next, each pattern PW transferred to the wafer W under each exposure condition is measured to perform pattern matching with the template pattern, and for example, a correlation coefficient is determined for each exposure condition. Then, the two-dimensional coordinates (I,
After determining the distribution of Z), by setting the threshold value of the correlation coefficient C, 2-dimensional coordinate to the threshold (I, based on the figure coordinate value of Z) is formed, the best exposure condition (I _B, Z _B)
Ask for.

In this procedure, it is conceivable to use the above-mentioned value | ΔL | instead of the correlation coefficient. However, when using the value | ΔL | Very precise measurement is required to detect a subtle change for each line width, but in pattern matching with a template pattern, the pattern PW transferred to the wafer W is handled collectively, A change in the transferred pattern PW can be accurately detected.
That is, from the viewpoint of measurement accuracy, it is more advantageous to use the correlation coefficient than the value | ΔL |.

Hereinafter, the detection of the best exposure condition in this embodiment will be described in more detail with reference to FIGS. 6 and 7 show flowcharts for detecting the best exposure condition in the present embodiment.

First, in step 201 of FIG. 6, a reticle R _T for collecting reference information is loaded on the reticle stage RST by a reticle loader (not shown). FIG. 8 shows a pattern configuration formed on a reticle R _T for collecting reference information used in the present embodiment. The reticle R _T, as shown in FIG. 8 (A), a central portion and four corners total of five marks RM of the pattern area PA of the reticle R _T is formed. The pattern area PA other than the mark RM formation area is a light shielding pattern. Each mark RM is, as shown in FIG.
This is an L / S mark in which lines having a line width LR _X and a line length _RY are arranged in the line width direction at a period of 2LR _X.

[0082] Returning to FIG. 6, subsequently, in step 203, the wafer loader (not shown), measurement wafer W _T is loaded onto the substrate table 18.

Next, in step 205, the exposure energy is set to an initial value (= I ₁ ). In the present embodiment, in determining the exposure condition, the exposure energy is changed from I ₁ to I _N (N = 6, for example) in steps of ΔI. The setting of the exposure energy is performed by the exposure energy coarse adjuster 3 or the light source 1 shown in FIG. That is, the adjustment of the exposure energy by the coarse adjuster 3 is performed by changing the transmittance of the laser beam LB. On the other hand, the correlation between the output ES of the energy controller 1c in FIG. 3 and the output DS of the integrator sensor 53 is obtained in advance, and based on this correlation, the adjustment of the exposure energy by the light source 1 is performed for one pulse of the laser beam LB. This is done by changing the hit energy. The adjustment of the exposure energy by the light source 1 is performed by the shutter 1f.
Is performed in a state where the laser beam LB is cut off.

Next, in step 207, main controller 20 instructs stage control system 19 to set a target position (hereinafter, referred to as a "Z position" or "focus position") for positioning of wafer W _{T in} the Z direction in scanning exposure. ) Is the initial value (= Z ₁ ). In the present embodiment, in determining the exposure condition, the Z position is shifted from Z ₁ by Δ
It is changed in steps of Z to Z _M (M = for example, 6).

[0085] Subsequently, in step 209, divided areas DA _ij of the exposure surface of the wafer _{W T (i = 1~M, j} =
Substrate table 18 to the scanning start position in the divided area DA ₁₁ of the 1 to N) marks RM on reticle R is transferred is moved. This movement is performed by the main control device 20 via the stage control system 19 and the wafer driving device 21. 9 and 10 show the arrangement of the partition areas DA _ij on the wafer W. The surface of the wafer W is shown in FIG.
As shown in (A), the pattern area P of the reticle R
A is divided into a plurality of shot areas SA corresponding to A.
In this shot area, as shown in FIG. 9B, there are five areas DA corresponding to the five marks transferred in the subsequent measurement exposure. Each of these areas DA, are virtually divided into a matrix, these divided areas, one mark RM is a divided area DA _ij transcribed by the scanning exposure of one. Further, as shown in FIG. 10, the _divided area DA _ij is + X
Direction is the row direction (increasing direction of j), + Y direction are arranged on wafer W _T to a matrix which is a column direction (increasing direction of i).

Returning to FIG. 6, next, at step 211, the reticle R _T as described above with reference to FIG.
And the wafer W _T are moved synchronously to make the illumination area IAR
Conjugate area IA opens the shutter 1f just before start takes the shot area SA, performing scanning exposure of the shot area of the exposure surface of the wafer W _T. During this scanning exposure, the main controller 20 moves the substrate table 18 in the Z-axis direction through the stage control system 19 and the wafer drive 21 based on the detection signals of the multipoint focus position detection system (40, 42). with the target position is driven and controlled in the Z axis direction so that Z ₁ combined adjustment of the drive controlled by the surface located on the tilting direction (setting of the alignment surface). The conjugate area IA of the illumination area IAR closes the shutter 1f immediately after leaving the divided area DA _ij.

When step 211 is completed, step 2
In step 13, it is determined whether or not the transfer of the divided area corresponding to the predetermined Z position range is completed with the exposure energy kept constant. Because only mark RM only for divided areas DA ₁₁ is transferred in the above, the scanning exposure for a given Z position range is determined not to be made.
Then, in step 215, main controller 20
The stage control system 19 _transmits the Z of the wafer W _T in the scanning exposure.
Position indicates that it is Z _2. Subsequently, in step 209, as described above, the substrate table 1 to the scanning start position mark RM to divided area DA ₂₁ is transferred
8 is moved. At this time, reticle _RT is returned to the scanning start position. Then, in step 211, as in the case of divided area DA _11, the scanning exposure for the transfer mark RM in relation to the block region DA ₂₁ is performed.

Thereafter, in step 213, a predetermined Z
Until it is determined that scanning exposure has been performed on the position range, the mark RM on the partitioned area DA _i1 (i = 3 to M)
Are sequentially performed. Thus,
Exposure energy amount in the scanning exposure for the case where I _1, the pattern formed on reticle R _T to the surface to be exposed of the wafer W _T is transferred. If it is determined in step 213 that the scanning exposure has been performed for the predetermined Z position range, then, in step 217, it is determined whether or not the exposure for the defined area in the predetermined exposure energy range has been completed. In the above, the divided area DA _i1 (i = 1 to
Since only the mark RM has been transferred only to M), it is determined that the scanning exposure has not been performed in the predetermined exposure energy range.
Similarly to 5, the exposure energy is set to be I ₂ .

[0089] Then, the exposure energy as in the case of I _1, in step 207, the main controller 20,
The stage control system 19, after the Z position of the wafer W _T in the scanning exposure has indicated that it is Z _1, step 209
Step 215 is repeatedly executed, and the divided area DA
Scanning exposure for transferring the mark RM for _i2 is performed.

Thereafter, in step 217, until it is determined that the scanning exposure has been performed in the predetermined exposure energy range, the mark RM relating to the partitioned area DA _ij (i = 1 to M, j = 3 to N) is transferred. Are sequentially performed. Thus, the pattern formed on reticle R _T to the surface to be exposed of the wafer W _T is transferred for a predetermined exposure energy range. As a result, the marks MR are transferred to all of the partition areas DA _ij . If it is determined in step 217 that the scanning exposure has been performed within the predetermined exposure energy range, then, in subroutine 221, pattern matching between the pattern transferred to each partitioned area DA _ij and the template pattern is performed.

FIG. 7 shows a flowchart of the subroutine 221. As shown in FIG. 7, in the subroutine 221, first, in step 227, the wafer W _T is unloaded from the substrate table 18 (see FIG. 1), and subsequently, in step 229, the wafer W _T is developed. Next, in step 231, the transfer pattern formed in the partitioned regions DA _ij on the developed wafer W _T is imaged by CCD or the like through a microscope, the imaging result data is taken into the computer. For this data capture, an exposure apparatus equipped with a microscope and a CCD in addition to the exposure apparatus 100 of the present embodiment described above may be used.
Alternatively, it may be performed by another device including a microscope or the like and a computer.

Next, in step 233, a template pattern is set. Here, the template pattern, can either be an ideal transfer pattern calculated based on the pattern formed on reticle R _T and the projection magnification of the projection optical system PL, and also in the divided area DA _ij A pattern selected from the transferred patterns can also be used. In selecting this pattern, a pattern determined by a person to be close to the most ideal pattern among the patterns transferred to the partitioned area DA _ij can be used. A pattern transferred to a partitioned area exposed under the exposure condition closest to the energy and the best focus position can also be used. Subsequently, in step 235, pattern matching between the pattern transferred to each section area DA _ij and the template pattern is performed to obtain a correlation coefficient for each section area DA _ij . Then, in step 237,
The correlation coefficient C _{ij for} each partitioned area DA _ij thus obtained
And returns to the main routine.

Next, returning to FIG. 6, at step 223, the best exposure energy and the best focus position, which are the best exposure conditions, are obtained for each of the five areas DA in the shot area SA as follows. First, one area DA
, The distribution of the correlation coefficient is obtained by considering the two-dimensional coordinates (I, Z) of the exposure energy I and the focus position Z, and plotting the correlation coefficient C _ij at the coordinate values (I _j , Z _i ). In the above-described exposure of the measurement wafer W _T , the divided areas DA _ij have the same size, and the difference in exposure energy between the divided areas adjacent in the row direction is a constant value (= ΔI). Having a constant value the difference between the focus position adjacent in the column direction (= [Delta] Z), the wafer W _T on the divided area DA _ij sequences as two-dimensional coordinates of (I, Z) coordinate values in (I _j, Z _i ).

Next, the best exposure condition is determined based on the distribution of the correlation coefficient C _ij obtained in this manner, and several methods can be considered. For example, in the first method, a threshold value of the correlation coefficient is set, and it is determined that there is a transfer pattern in a section area having a correlation coefficient larger than the threshold value, whereas no transfer pattern exists in a section area having a correlation coefficient smaller than the threshold value. Is determined. FIG. 11 shows an example of this determination result. Note that, in FIG. 11, the divided areas determined to have no transfer pattern are shown as white areas, and the divided areas determined to have transfer patterns are shown as hatch areas.
Then, of the divided areas determined to have the transfer pattern,
A section area adjacent to the section area determined to have no transfer pattern is extracted, and the coordinate values of the extracted section areas are obtained. From the coordinate values thus obtained, an approximate curve in the two-dimensional coordinates (I, Z) is obtained by, for example, the least square method. Based on this approximation curve, the best exposure energy I
Determining _B and the best focus position Z _B. Here, the best exposure energy I _B, in the approximate curve regards exposure energy I as independent variables, when the value and the focus position Z and the difference δZ specific focus position is regarded as the dependent variable, the value of δZ up value (or the value of δZ minimum value) may be calculated values of exposure energy to be as the best energy I _B. Further, when the best focus position Z _B is regarded as an independent variable in the approximated curve, and the difference δI between a specific exposure energy value and the exposure energy I is regarded as a dependent variable, the value of δI becomes the maximum value. (or the value of δI minimum value) may be obtained values of the focus position to be the best focus position Z _B.

In the second method, a plurality of threshold values of the dependent variable are set in the approximate curve of the first method, and the midpoint of the value of the independent variable in which the dependent variable is the threshold value is obtained for each threshold value. . Then, the best value of the parameter of the exposure condition selected as the independent variable is obtained from the average value of these middle points. According to this, one value can be reliably determined as the best value. In addition, as a third method, two-dimensional coordinate values (I _j ,
An approximated surface (that is, C (I, Z)) is obtained from the correlation coefficient C _ij for Z _i ), and the value of the exposure energy and the value of the focus position at which the correlation coefficient becomes maximum in this approximated surface are determined as the best exposure energy. The best exposure condition may be determined as the best focus position.

Thereafter, in the same manner as above, the best exposure condition is obtained for each of the other areas DA. Thus, the best exposure condition for each position in the shot area SA of each area DA is obtained.

In step 225, the best exposure condition obtained in step 223 is
The information is stored in the storage device 29. In this way, subjective factors can be eliminated, and the best exposure conditions can be obtained stably and accurately.

Next, an exposure operation by the scanning exposure apparatus 100 of the present embodiment in the case of manufacturing a device will be described.

First, the reticle R on which the pattern to be transferred is formed is moved by the reticle loader to the reticle stage R.
Loaded to ST. Similarly, the wafer W to be exposed is loaded on the substrate table 18 by the wafer loader.

Next, the main controller 20 controls the reference mark plate F on the substrate table 18 by a reticle microscope (not shown).
M, reticle alignment, baseline measurement using an alignment detection system (not shown), and preparation work such as alignment measurement such as EGA (enhanced global alignment) using the alignment detection system are performed as required according to a predetermined procedure. Will be

In this exposure operation, first, the wafer W
The substrate table 18 is moved such that the XY position of the substrate table becomes the scanning start position for exposing the first shot area (first shot) on the wafer W. This move
The operation is performed by the main controller 20 via the stage control system 19 and the wafer driving device 21. At the same time, the reticle stage 18 is moved so that the XY position of the reticle R becomes the scanning start position. This movement is performed by the main controller 20 via the stage control system 19 and a reticle drive unit (not shown).

[0102] Thus, to move the wafer W and reticle R in each of the scanning start position, before moving synchronously, the main controller 20, the best exposure energy I _B and the best focus position is a best exposure condition from the storage device 29 It reads the Z _B. Then, the main controller 20, based on the read best exposure energy I _B, the energy of the exposure illumination light source 1 and the rough modulator 3 is controlled to thereby adjust the I _B,
As the target focus position of the best focus position Z _B are read out, and notifies the stage control system 19.

Then, the stage control system 19 controls the XY position information of the reticle R measured by the reticle interferometer 16 and the X-axis of the wafer W measured by the wafer interferometer 28.
On the basis of the Y position information and the first speed information, the reticle R
And the wafer W are relatively moved. Scanning exposure is performed along with the relative movement.

The stage control system 19 moves the substrate table 18 in the Z-axis direction and the tilt direction through the wafer driving device 21 based on the Z position information of the wafer detected by the multi-point focus position detection system (40, 42). Drive control is performed in the direction to adjust the surface position.

When the transfer of the reticle pattern to the first shot area is completed by the scanning exposure performed while being controlled as described above, the substrate table 18 is stepped by one shot area, and the scanning exposure is performed similarly to the previous shot area. Done. The shutter 1f
Is opened and closed at the same timing as described above.

Thereafter, the stepping and the scanning exposure are sequentially repeated as described above, and the required number of shot patterns are transferred onto the wafer W. Therefore, according to the present embodiment, scanning exposure can be performed under the best exposure condition obtained with high accuracy, and highly accurate exposure can be performed.

Next, an embodiment of a device manufacturing method using the above-described scanning exposure apparatus and method will be described.

FIG. 12 shows devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin film magnetic heads,
The flowchart of the example of manufacture of a micromachine etc. is shown. As shown in FIG. 12, first, in step 30
In 1 (design step), a function / performance design of a device (for example, a circuit design of a semiconductor device) is performed, and a pattern design for realizing the function is performed. Subsequently, in step 302 (mask manufacturing step)
A mask on which the designed circuit pattern is formed is manufactured. On the other hand, in step 303 (wafer manufacturing step)
A wafer is manufactured using a material such as silicon.

Next, in step 304 (wafer processing step), actual circuits and the like are formed on the wafer by lithography using the mask and the wafer prepared in steps 301 to 303, as described later. Next, step 305 (device assembly step)
In, device assembly is performed using the wafer processed in step 304. This step 305 includes processes such as a dicing process, a bonding process, and a packaging process (chip encapsulation) as necessary.

Finally, step 306 (inspection step)
In step 305, inspections such as an operation confirmation test and a durability test of the device manufactured in step 305 are performed. After these steps, the device is completed and shipped.

FIG. 13 shows a detailed flow example of step 304 in the case of a semiconductor device. In FIG. 13, step 311 (oxidation step)
In, the surface of the wafer is oxidized. Step 312
In the (CVD step), an insulating film is formed on the wafer surface. In step 313 (electrode forming step), electrodes are formed on the wafer by vapor deposition. Step 3
At 14 (ion implantation step), ions are implanted into the wafer. Steps 311 to 314 described above
Each of them constitutes a pre-processing step in each stage of wafer processing, and is selected and executed according to a necessary process in each stage.

At each stage of the wafer process, when the above-described pre-processing step is completed, the post-processing step is executed as follows. In this post-processing step, first, in step 3
In 15 (resist forming step), a photosensitive agent is applied to the wafer. Subsequently, in step 316 (exposure step), the circuit pattern of the mask is transferred onto the wafer by the above-described exposure apparatus and exposure method. next,
In step 317 (development step), the exposed wafer is developed, and in step 318 (etching step), the exposed members other than the portion where the resist remains are removed by etching. Then, in step 319 (resist removing step), unnecessary resist after etching is removed.

By repeating these pre-processing and post-processing steps, multiple circuit patterns are formed on the wafer.

By using the device manufacturing method of the present embodiment as described above, it is possible to manufacture a highly integrated device which was conventionally difficult to manufacture.

In this embodiment, the L / S pattern is used as the pattern formed on the reticle _RT for measurement. However, similar to the L / S pattern, the L / S pattern is close to the actual circuit pattern, and the periodic pattern is easy for image processing. A simple dot pattern can also be used. Whichever pattern is used, it is preferable that the pattern is a periodic pattern near the minimum line width or the minimum area that can be transferred by the target exposure apparatus.

Further, in the present embodiment, the pattern formed on the reticle _RT for measurement is composed of the marks MR formed at five places at the center and four corners, but the desired position for obtaining the best exposure condition is obtained. The mark MR can be formed on the measurement reticle _RT in accordance with the resolution.

Further, the L / S pattern in the same period direction was used as the pattern formed on the reticle _RT for measurement, but the vertical lines, horizontal lines,
A composite L / S pattern such as an oblique line may be used. In this case, it becomes possible to measure aberration such as astigmatism.

In the present embodiment, pattern matching for calculating a correlation coefficient is used as pattern matching with a template pattern. For example, pattern matching for calculating a difference between patterns may be used.
In this case, the pattern matching result is minimized under the best exposure condition, and the pattern matching result increases as the distance from the best exposure condition increases. However, considering this point, it is necessary to determine the best exposure condition in the same manner as in the present embodiment. Can be.

Further, the template pattern can be a pattern consisting of only one of the maximum brightness and the minimum brightness. Also in this case, the best exposure condition can be determined by examining the dependence of the pattern matching result on the exposure energy and the focus position. For example, the best focus position can be determined by directly using the first method for obtaining the best exposure condition in the present embodiment, and the pattern matching result becomes extremely small due to a change in the focus position at the same exposure energy. A focus position that is a value is obtained for each exposure energy, and an exposure energy value at which the type of the extreme value changes from a local maximum value to a local minimum value can be obtained as the best exposure energy.

In the present embodiment, the best focus position is obtained by exposing the wafer while changing the Z position of the wafer. However, the main controller 20 forms the image plane position of the projection optical system PL in FIG. The best imaging condition can be obtained by being changed via the image characteristic correction controller 68. In this case, in order to set the best exposure condition, main controller 20 adjusts the imaging characteristics of projection optical system PL via imaging characteristic correction controller 68.

In this embodiment, an excimer laser light source is used as a light source, but an ultraviolet bright line (g-line, i-line, etc.) from an ultra-high pressure mercury lamp may be used. In this case, the exposure energy may be adjusted by lamp output control, a dimming filter such as an ND filter, a light amount aperture, and the like.

The present invention also relates to a reduction projection exposure apparatus using ultraviolet light as a light source, a reduction projection exposure apparatus using soft X-rays having a wavelength of about 10 nm as a light source, an X-ray exposure apparatus using a light source having a wavelength of about 1 nm, and an EB (Electronics). Beam exposure apparatus, and any wafer exposure apparatus such as an exposure apparatus using an ion beam, and a liquid crystal exposure apparatus. Also, it does not matter whether the apparatus is a step-and-repeat machine, a step-and-scan machine, or a step-and-stitching machine.

[0123]

As described in detail above, claim 1 is as follows.
According to the exposure condition determination method according to any one of (1) to (10), the pattern formed on the mask is transferred to the sensitive substrate under the exposure conditions of various combinations of the exposure energy amount and the focus position. Then, pattern matching between the pattern transferred to the sensitive substrate and the template pattern prepared in advance is performed, and the best exposure condition is determined based on the result of the pattern matching. The best exposure condition can be determined accurately.

According to the exposure method of the eleventh aspect, the pattern formed on the mask is transferred to the sensitive substrate according to the best exposure condition determined by the exposure condition determining method of the first aspect. Therefore, accurate exposure can be performed.

According to the exposure apparatus of the twelfth aspect, the pattern formed on the mask is stored in the storage device based on the best exposure condition determined by the exposure condition determining method of the first aspect. Since the image is transferred to the sensitive substrate, accurate exposure can be performed.

According to the device manufacturing method of the thirteenth aspect, since the exposure method according to the eleventh aspect is used in the exposing step, it is possible to manufacture a highly integrated device which has conventionally been difficult to manufacture.

[Brief description of the drawings]

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

FIG. 2 is a diagram for explaining an example of a specific configuration of the illumination system 10 of FIG.

FIG. 3 is a diagram for explaining a portion related to exposure amount control of the illumination system 10 of FIG. 2;

FIG. 4 is a view for explaining the principle of scanning exposure of the apparatus of FIG. 1;

FIG. 5 is a diagram (part 1) for explaining the principle of exposure condition determination in one embodiment ((A) to (C)).

FIG. 6 is a flowchart for determining exposure conditions according to one embodiment.

FIG. 7 is a flowchart of a subroutine 221 in FIG. 6;

FIG. 8 is a diagram for explaining a pattern formed on a reticle _RT ((A), (B)).

9 is a diagram for explaining the arrangement of divided areas on wafer _{W T ((A), (} B)).

FIG. 10 is a diagram for explaining the arrangement of partitioned areas.

FIG. 11 is a diagram for explaining a state of a transfer pattern due to a change in exposure energy I and a focus position Z;

FIG. 12 is a flowchart illustrating an embodiment of a device manufacturing method according to the present invention.

FIG. 13 is a flowchart of a process in step 304 of FIG.

[Explanation of symbols]

Reference Signs List 1 light source (part of light intensity variable mechanism) 3 coarse adjuster (part of light intensity variable mechanism) 19 stage control system (part of focus adjustment system) 20 main control device (adjustment device) 21 wafer drive device (drive) Mechanism) 29 Storage device 40 Irradiation optical system (part of detection system, part of focus adjustment system) 42 Light receiving optical system (part of detection system, part of focus adjustment system) PL Projection optical system R Reticle (mask) R _T reticle (measurement mask) W wafer (photosensitive substrate) W _T wafer (measurement sensitive substrate)

Claims (13)

[Claims] An exposure condition determination method for irradiating a mask with exposure illumination light and transferring a pattern formed on the mask to a sensitive substrate via a projection optical system, the method comprising: On the exposure surface, regarding a virtual virtual partitioned area having a row direction and a column direction that are orthogonal to each other, for the same row, the measurement sensitive substrate is at the same position in the optical axis direction of the projection optical system, In the row direction, while changing the exposure energy amount monotonously,
The same exposure energy amount is used for the same row, and the position of the measurement sensitive substrate in the optical axis direction is monotonously changed in the column direction, so that the measurement pattern formed on the measurement mask is formed in each of the divided areas. A first step of transferring;
A second step of developing the sensitive substrate to which a pattern has been transferred in the first step, and detecting a transfer pattern formed on the developed sensitive substrate; and each of the divided areas detected in the second step A third step of pattern-matching the transfer pattern and a previously prepared template pattern; and a fourth step of obtaining the best exposure condition based on the result of the pattern matching in the third step. 2. The exposure condition determination method according to claim 1, wherein each of the divided areas has the same shape, and the difference in the amount of exposure energy between the adjacent divided areas in the row direction is the same. Method. 3. The apparatus according to claim 1, wherein each of the divided areas has the same shape, and a difference in position in the optical axis direction between the adjacent divided areas in the column direction is the same.
3. The exposure condition determination method described in 1. 4. The exposure condition determination according to claim 1, wherein the measurement pattern is a periodic pattern formed over the entire area of the measurement mask irradiated with the exposure illumination light. Method. 5. The exposure condition according to claim 1, wherein the measurement pattern is a periodic pattern formed in a part of the irradiation area of the exposure illumination light of the measurement mask. Decision method. 6. A part of an irradiation area of the exposure illumination light, on which the measurement pattern of the measurement mask is formed, is two or more minute areas having different distances from a center point of the irradiation area. The exposure condition determination method according to claim 5, wherein: 7. The exposure condition determination method according to claim 1, wherein the template pattern is a pattern transferred to one of the divided areas selected from the divided areas. 8. The method according to claim 1, wherein the template pattern is a pattern calculated based on the measurement pattern and a projection magnification of the projection optical system. 9. The exposure condition determining method according to claim 1, wherein the template pattern is a pattern consisting of only one of maximum brightness and minimum brightness. 10. The exposure condition determination method according to claim 1, wherein the best exposure condition is at least one of a condition related to a best focus position in the optical axis direction and a condition related to a best exposure energy amount. 11. A mask is irradiated with illumination light for exposure,
An exposure method for transferring a pattern formed on the mask to a sensitive substrate via a projection optical system, wherein the exposure method includes the steps of:
Setting a best exposure condition determined by the exposure condition determination method according to any one of claims 10 to 10; and a pattern formed on the mask under the set exposure condition via a projection optical system. And a step of transferring the image to a substrate. 12. A mask is irradiated by exposure illumination light,
An exposure apparatus for transferring a pattern formed on the mask to a sensitive substrate via a projection optical system, wherein the driving device drives the sensitive substrate in an optical axis direction of the projection optical system and in a two-dimensional plane orthogonal to the optical axis direction. And a detection system for detecting the position of the sensitive substrate in the optical axis direction, and monitoring the detection result of the detection system to determine the position of the sensitive substrate in the optical axis direction via the drive mechanism in a predetermined manner. 2. The exposure according to claim 1, wherein the focus adjustment system adjusts to a target position; a light intensity variable mechanism that changes an intensity density of the exposure illumination light; and the exposure is performed using the drive mechanism and the light intensity variable mechanism. A storage device for storing the best exposure condition determined by the condition determination method; at least the target position of the focus adjustment system and the light intensity variable mechanism so that the best exposure condition stored in the storage device is obtained. An exposure apparatus and an adjusting device for adjusting one. 13. A method for manufacturing a device, comprising an exposure step using the exposure method according to claim 11.