JP2001244182A - Method of measuring variations in image formation characteristics of projection optical system due to exposure heat and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To easily measure variations in the image formation characteristics, such as a projection magnifying power and position of the focal point of a reduction projection lens under lightning conditions and to optimize the correction coefficient of the image formation characteristics in a short time. SOLUTION: A first process is provided in which the amount of energy exposed that irradiates a projection optical system is controlled in time, and the amount of an image formation characteristics change in the projection optical system is measured with time, when a prescribed pattern formed on a reticle 109 as an original plate is transferred on a wafer 115 as a photosensitive substrate located at a conjugate point of the reticle 109 for exposure, through the intermediary of the reduction projection lens 110 and reduction projection lens aperture stop 111 of a projection optical system. A second process is also provided in which an irradiation variation in the image formation characteristics is turned quantitative.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a projection exposure apparatus for manufacturing semiconductor elements such as ICs and LSIs, liquid crystal substrates, thin-film magnetic heads, and the like, and measures and optimizes fluctuations in imaging characteristics of a projection optical system. It is about the method.

[0002]

2. Description of the Related Art Conventionally, in the process of manufacturing a semiconductor device formed from an extremely fine pattern such as an LSI or a super LSI, a circuit pattern drawn on a mask is reduced and exposed on a substrate coated with a photosensitive agent, and is formed by printing. A reduced projection exposure apparatus is used. As the packaging density of semiconductor devices has increased, further miniaturization of patterns has been demanded, and the development of resist processes and the coping with miniaturization of exposure apparatuses have been performed.

As a means for improving the resolving power of the exposure apparatus, there are a method of changing the exposure wavelength to a shorter wavelength and a method of increasing the numerical aperture (NA) of the reduction projection lens. When the resolution is improved in this manner, the depth of focus of the reduction projection lens becomes shallower. Therefore, improvement of focus accuracy for matching the wafer surface with the imaging plane (focal plane) of the reduction projection lens is an important theme.

[0004] One of the important optical characteristics of the projection exposure apparatus is alignment accuracy for accurately superimposing each pattern over a plurality of steps. An important factor affecting this alignment accuracy is a reduction projection lens. There is a magnification error. The size of patterns used in VLSIs is becoming increasingly finer year by year, and accordingly, there is a growing need for improved alignment accuracy. Therefore, the necessity of maintaining the magnification of the reduction projection lens at a predetermined value has become extremely high.

The reduction projection lens absorbs a part of the exposure energy, and the heat generated thereby causes a change in the temperature of the reduction projection lens, thereby changing the optical characteristics such as the refractive index of the reduction projection lens. It has been known. Therefore, if the exposure light is continuously irradiated on the reduction projection lens for a long time, the amount by which the projection magnification of the reduction projection lens changes with respect to a predetermined reduction magnification (for example, 1/5) or the image forming surface of the reduction projection lens The amount by which the position of the (focal plane) changes in the optical axis direction may change by an amount that cannot be ignored for the focus accuracy and the alignment accuracy described above. For this reason,
There has been proposed a method of correcting a temporal variation of an imaging characteristic due to an exposure energy irradiation state of a reduction projection lens. For example, as proposed by the present applicant in Japanese Patent Publication No. 63-16725, the amount of focus change due to the exposure energy state of the reduction projection lens is measured,
And a model expression using the non-exposure time and the like as variables, and corrects the focus position of the reduction projection lens based on the calculation result. The model formula has a focus change coefficient specific to the reduction projection lens. If this coefficient is measured by an experiment, it is possible to compensate for a difference in focus characteristics of the reduction projection lens.

Further, there has been proposed an exposure apparatus capable of obtaining a better resolution for projecting a specific pattern by changing the numerical aperture of an illumination system. In such an apparatus, generally, when the numerical aperture of the illumination system is changed, the illuminance on the wafer image plane changes accordingly, and at the same time, the distribution state of the light flux on the pupil plane of the reduction projection lens, that is, in the vicinity of the pupil plane. Energy density changes. Therefore,
If the distribution of the light source image generated on the pupil plane of the reduction projection lens changes due to the illumination light, the imaging characteristics due to the above-described exposure energy irradiation state also change, and the amount that cannot be ignored for the focus accuracy and the alignment accuracy may change. There is. For this reason, there has been proposed a method of satisfactorily adjusting the fluctuation of the imaging characteristic even when the energy distribution incident on the reduction projection lens changes. For example, as proposed in the specification of Japanese Patent No. 2828226, a correction coefficient of an imaging characteristic corresponding to a light source distribution state of illumination light is stored, and when the light source distribution state is changed, a corresponding correction coefficient is stored. There is a method of reading out correction information and performing correction based on the information.

[0007]

In order to accurately correct the variation of the imaging characteristics due to the exposure energy irradiation, an experimental exposure (hereinafter, referred to as an exposure) while changing the exposure condition in advance corresponding to the light source distribution state of the illumination light. It is necessary to optimize the irradiation variation amount of the imaging characteristics by “test exposure”.

However, with increasing lighting conditions,
It is very difficult for the operator to repeat the test exposure while changing the amount of exposure energy applied to the reduction projection lens over time, and to manually perform the process of optimizing the correction coefficient. There is a disadvantage that requires a long time. Further, with the improvement of the focus accuracy and the alignment accuracy, it is necessary to further improve the accuracy of the correction coefficient. Also in this case, the method in which the operator repeatedly performs the test exposure and optimizes the correction coefficient has a disadvantage that it takes a very long time.

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, it is an object of the present invention to easily measure the projection magnification of a reduction projection lens and the imaging characteristics of a focus position under a plurality of illumination conditions, and to correct the imaging characteristics. The purpose is to optimize the coefficients in a short time.

[0010]

According to the present invention, a predetermined pattern formed on an original is transferred onto a photosensitive substrate at a position conjugate with the original via a projection optical system. A method for measuring the variation of the imaging characteristic of the exposure apparatus, wherein a first step of controlling the amount of exposure energy applied to the projection optical system over time and measuring a variation of the imaging characteristic of the projection optical system over time; And quantifying the irradiation variation of the imaging characteristic by function approximation based on the measurement result of the imaging characteristic.

Further, the present invention provides an illumination system for illuminating an original with illumination light for exposure, a projection optical system for projecting the pattern of the original on a photosensitive substrate with a predetermined imaging characteristic, and An exposure apparatus comprising: a light source distribution changing unit configured to change a distribution of a light source image generated on a pupil plane of the projection optical system by illuminating light, wherein the distribution of the light source image is changed by the light source distribution changing unit. First means for controlling the amount of energy applied to the projection optical system over time for each distribution of the light, and measuring the amount of change over time in the imaging characteristics, and the light source based on the measurement result of the imaging characteristics. Second means for quantifying the irradiation variation of the imaging characteristics by function approximation for each image distribution,
It is characterized in that a measuring means including the first means and the second means for measuring the fluctuation of the imaging characteristic is provided.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiments of the present invention,
The amount of exposure energy applied to the reduction projection lens is controlled over time according to a plurality of illumination conditions, and the measurement pattern on the original (mask) is test-exposed on the substrate (wafer) while changing the imaging characteristics. Measuring the amount of variation based on the imaging information of the measurement pattern formed on the substrate (wafer),
A measurement method for calculating a correction coefficient by approximating a function of the imaging characteristic fluctuation from the measurement result is proposed, and the above object is achieved by automating the method.

Further, in the method or the exposure apparatus for measuring the variation of the imaging characteristic of the projection optical system according to the embodiment of the present invention, the variation of the imaging characteristic of the projection optical system may include a focus, a magnification,
And at least one of distortions.

[0014]

FIG. 1 shows a schematic configuration of an exposure apparatus according to an embodiment of the present invention. In the figure, 101 is, for example, KrF
A pulsed laser light source in which a gas such as that described above is sealed and emits laser light.

The light source 101 emits light having a wavelength in the far ultraviolet region of 248 nm. Further, the laser light source 101 includes a front mirror constituting a resonator, a diffraction grating for narrowing an exposure wavelength, a narrowing module including a prism, and a spectral device for monitoring wavelength stability and spectral width. A monitor module including a detector and a detector, a shutter, and the like are provided. Control of gas exchange operation of the laser light source 101, control for wavelength stabilization, control of discharge applied voltage, and the like are performed by the laser control device 102. In this embodiment, independent control by only the laser controller 102 is not performed, and control can be performed by a command from the main controller 103 of the entire exposure apparatus connected by an interface cable.

The beam emitted from the pulse laser light source 101 is applied to a beam shaping optical system (not shown) of the illumination optical system 104.
After the beam is shaped into a predetermined beam shape through a laser beam, the beam is incident on an optical integrator (not shown), and forms a number of secondary light sources to illuminate a mask 109 described later with a uniform illuminance distribution. The shape of the aperture of the aperture stop 105 of the illumination system 104 is substantially circular, and the illumination system controller 108 can set the diameter of the aperture and, consequently, the numerical aperture (NA) of the illumination optical system 104 to a desired value. Has become. In this case, the value of the ratio of the numerical aperture of the illumination optical system 104 to the numerical aperture of the reduction projection lens 110, which will be described later, is the coherence factor (σ value).
Reference numeral 8 indicates that the σ value can be set by controlling the aperture stop 105 of the illumination system. A half mirror 106 is arranged on the optical path of the illumination optical system 104, and a part of the exposure light for illuminating the reticle 109 is reflected by the half mirror 106 and taken out. A photo sensor 107 for ultraviolet light is disposed on the optical path of the reflected light from the half mirror 106, and generates an output corresponding to the intensity (exposure energy) of the exposure light. The output of the photo sensor 107 is the pulse laser light source 1
The energy is converted into an exposure energy per one pulse by an integration circuit (not shown) that performs integration every pulse emission of 01, and is input to a main controller 103 that controls the exposure apparatus main body via an illumination system controller 108.

Reference numeral 109 denotes a reticle (or mask) serving as an original, on which a circuit pattern of a semiconductor element to be printed is formed. The reduction projection lens 110 reduces the circuit pattern image of the reticle 109 at a reduction magnification β (β is, for example, １ ／),
Wafer 11 as photosensitive substrate coated with photoresist
5 so as to form an image on one shot area. An aperture stop 111 of the reduction projection lens 110 whose opening is substantially circular is arranged on a pupil plane (Fourier transform plane with respect to the reticle) of the reduction projection lens 110, and the diameter of the opening is controlled by driving means 112 such as a motor. By doing so, a desired value can be set. Reference numeral 113 denotes a field lens driving device, which is a reduction projection lens 110.
The field constituting a part of the middle lens system is moved on the optical axis of the reduction projection lens 110 by using air pressure, a piezoelectric element, or the like, thereby preventing various aberrations of the reduction projection lens 110 from deteriorating. While improving the projection magnification, the distortion error is reduced.

The wafer stage 116 can move in a three-dimensional direction, and can move in the optical axis direction (Z direction) of the reduction projection lens 110 and in a plane (XY plane) orthogonal to this direction. Then, by measuring the distance between the movable mirror 117 fixed to the wafer stage 116 by the laser interferometer 118, the XY plane position of the wafer stage 116 is detected. The stage controller 120 under the control of the main controller 103 of the exposure apparatus detects the position of the wafer stage 116 by the laser interferometer 118 and controls the driving means 119 such as a motor to move the wafer stage 116 to a predetermined position. Move to the XY plane position.

Reference numeral 121 denotes a light projecting optical system, and 122 denotes a detection optical system. These constitute a focus surface detecting means, and the light projecting optical system 121 is a non-exposure method that does not expose the photoresist on the wafer 115 to light. A plurality of light beams composed of light are projected, and the light beams are respectively condensed and reflected on the wafer 115. The light beam reflected by the wafer 115 is incident on the detection optical system 122.

Although not shown, a plurality of position detecting light receiving elements are arranged in the detecting optical system 122 in correspondence with each reflected light beam. The reflection point of each light beam is configured to be substantially conjugate by the imaging optical system. Reduction projection lens 1
The displacement of the surface of the wafer 115 in the optical axis direction of No. 10 is as follows.
It is measured as a position shift of the incident light beam on the position detecting light receiving element in the detection optical system 122.

Next, a description will be given of a model formula of irradiation variation of the image forming characteristic of the reduction projection lens 110 due to exposure energy irradiation according to the present embodiment, and a correction coefficient for quantifying the model formula. FIG. 2 shows an example of a change over time of a change in focus (or magnification) of the reduction projection lens due to exposure.

In FIG. 2, the horizontal axis is time t, and the vertical axis is the focus (or magnification) fluctuation amount F of the reduction projection lens 110.
Is shown. When the initial focus (or magnification) of the reduction projection lens 110 is set to F0 and the laser light source 101 starts exposing the reduction projection lens 110 from time t0, the focus (or magnification) changes with time and is constant at time t1. Focus (or magnification) F1
To be stable. After that, even if the exposure light is continuously applied to the reduction projection lens 110, the energy absorbed by the reduction projection lens 110 to become heat and the thermal energy emitted from the reduction projection lens 110 reach an equilibrium state, and the focus (or magnification) is reached. ) Does not change from F1. When the exposure is stopped at time t2, the focus (or magnification) returns to the original state with time, and at time t3, the focus (or magnification) becomes the initial focus (or magnification) F0. The variation ΔF from F0 to F1 is determined by the size of the exposure area of the pattern on the mask 109 (hereinafter referred to as “pattern size”), the ratio of the light transmitting portion to the pattern size (hereinafter referred to as “transmittance”), and the laser light source. It changes according to the pulse energy emitted from 101. That is, focus (or magnification)
The amount of change varies proportionally with the amount of exposure energy applied to the reduction projection lens 110. Reduction projection lens 11
Assuming that the exposure energy applied to 0 is Q, the variation ΔF
Is represented by equation (1).

ΔF = K × Q (1)

In equation (1), K is a focus change saturation value (or magnification change saturation value) per unit light amount (unit exposure energy), and the focus (or magnification) fluctuation curve shown in FIG. This value will converge later.

The time constant TS1 at the rise from time t0 to t1 and the time constant TS2 at the fall from time t2 to t3 are constant regardless of the amount of exposure energy applied to the reduction projection lens 110. is there. These time constants TS
1 and TS2 are equivalent to the time constant on the heat transfer characteristic of the reduction projection lens 110, and indicate values unique to the reduction projection lens 110. In other words, at the time of rising and falling, a fluctuation similar to the characteristic of the exponential function is exhibited. The characteristics at the time of rising are approximated by Expression (2) ΔF × (1−exp (−t / TS1)) (2), and the characteristics at the time of falling are expressed by Expression (3) ΔF × exp (−t / TS2) (3)

However, when the coherence factor (σ value), which is the ratio of the numerical aperture of the illumination optical system 104 to the numerical aperture of the reduction projection lens 110, is changed, the pupil plane of the reduction projection lens 110 is changed as described above. The generated energy density distribution changes, and not only the time constants TS1 and TS2 but also the focus (or magnification) change saturation value K changes. A curve showing the irradiation variation characteristic of the image forming characteristic of the reduction projection lens 110 shown in FIG. 2 is modeled by the functions of Expressions (1), (2), and (3), and the coefficients are used to quantify the amount of variation. The given time constants TS1 and TS2 and the focus change saturation value (or magnification change saturation value) K are converted into coherence factors (σ values).
By accurately obtaining the focus accuracy and the alignment accuracy, the focus accuracy and the alignment accuracy can be improved.

Next, an embodiment of a test exposure method for obtaining the correction coefficient, which is a feature of the present invention, will be described using the exposure apparatus shown in FIG. First, test exposure for obtaining a focus variation curve will be described. FIG. 3 shows a predicted curve 301 of focus fluctuation due to exposure energy irradiation.
FIG. In the figure, the horizontal axis represents time, and the vertical axis represents the focus fluctuation amount of the reduction projection lens 110. During the period from time t0 to time t10, the exposure light is continuously irradiated on the reduction projection lens 110, and the rising characteristic of the focus fluctuation is shown. From time t10 to t2
Until 0, the exposure light is not irradiated, and shows a falling characteristic. When measuring the rising characteristic, exposure light is continuously applied to the reduction projection lens 110, and the curve 3
Arbitrary timings h1 and h during the rising of 01
The amount of change in the focus position may be measured at 2,..., H10, and approximated by the model equation (1) representing the rising characteristic.
Similarly, in the case of measuring the falling characteristics, the arbitrary timings c11, c12,..., C during the falling of the curve 301 without irradiating the reduction projection lens 110 with the exposure light.
The fluctuation amount of the focus position may be measured at 20 and approximated by the model expression (3) representing the fall characteristic.

A method of controlling the amount of exposure energy applied to the reduction projection lens 110 with time in order to measure the rising and falling characteristics will be described with reference to FIGS. When measuring the rise characteristics, the number of measurement points (for example,
Between the measurement points (10 points shown in FIG. 3) (for example, h1 in FIG. 3)
The main controller 103 sets each exposure amount (the exposure amount per unit time and the irradiation time) for irradiation between
Set to. Reduction sensor 11 with photo sensor 107
The reduction projection lens 110 is heated by performing exposure while monitoring the exposure amount irradiated to zero.

In this case, it is desirable to irradiate at the position of the wafer stage 116 where there is almost no reflected light. After heating the projection lens 110 with the set exposure amount, the wafer 115 is subjected to exposure (hereinafter, referred to as “sample exposure”) for measuring a variation amount of a focus position described later. When measuring the falling characteristics, the number of measurement points (for example, 10 points shown in FIG. 3) and each cooling time between the measurement points (for example, between c11 and c12 in FIG. 3) are set in the main control device 103 and reduced. Projection lens 110
After the natural cooling for the set time, the sample exposure is performed in the same manner as when the rise characteristic is measured.

The above-described sample exposure will be described with reference to FIGS. 4, 5 and 6. FIG. FIG. 4 is an example of a shot layout on a wafer used for sample exposure. In the figure, S1 to S11 are shots when the mask on which the resolution chart for focus measurement shown in FIG. 5 is drawn is reduced and projected on the wafer, and is composed of a total of 11 shots. The resolution chart shown in FIG.
A line width that can be resolved by the reduction projection lens 110 when the reduction projection exposure is performed on the wafer 115 is represented by a dot size,
The numerical values indicate the values of the line width. After reducing and exposing the mask pattern of FIG. 5 onto the wafer 115, the resolution chart exposed on the wafer 115 is measured with an optical microscope, and the smallest measurable dot (minimum value) is the limit line width of the exposure. .

Referring back to FIG. 4, a shot S1 for sample exposure
The focus position (Z position of the wafer stage) when exposing S11 to S11 will be described. In the figure, a reference focus position that has been adjusted beforehand in a state where exposure energy is not irradiated to the reduction projection lens 110 is defined as a focus position of S6 which is an intermediate shot. The focus position of the other shots is S which is the focus reference position.
6, the optical axis direction of the reduction projection lens 110 (Z direction)
The Z position of the wafer stage 116 is determined so as to be displaced vertically. In FIG. 4, S6 is set as a reference focus position,
Wafer stage 11 at a pitch of -0.1 μm in the direction of S1
6, the Z position is lowered, and +0. This is an example in which exposure is performed by raising the Z position of the wafer stage 116 at a pitch of 1 μm. As the shots S1 to S11 are exposed, the Z position of the wafer stage 116 is driven upward at a pitch of +0.1 μm.

FIG. 6 shows an example of the result obtained by subjecting the resolution chart shown in FIG. 5 to reduced projection exposure on the wafer 115 while changing the focus position, and measuring the limit line width. In FIG.
The vertical axis represents the limit line width that can be resolved by the reduction projection lens 110, and the horizontal axis represents the relative position of the wafer stage 116 in the optical axis direction (Z direction) when the focus reference position (shot S6) is 0.0. P1 to P11 are points where the results of measuring the critical line widths of the sample exposures S1 to S11 are plotted, and 601 is a curve obtained by quadratic approximation of the measured values of P1 to P11. In this example, the minimum value of the curve 601 is +
This is an example in which a slice 602 is sliced at 20%, and a focus variation amount +0.1 μm is obtained with the midpoint Pc as a best focus position.

Returning to FIG. 3, by performing the test exposure in which the above-described sample exposure is repeated for each of the measurement points h1 to h10 and c11 to c20 while controlling the amount of exposure energy and time for irradiating the reduction projection lens 110. In addition, the focus fluctuation characteristics can be accurately measured.

Then, based on the exposure energy amount, the reduced projection lens heating time, the cooling time, and the measured focus fluctuation characteristic, which are irradiated according to the heating condition of the set parameter, which is the exposure condition, the equations (1) and (2) are obtained. , The focus change saturation value K, the time constant TS1,
By calculating each coefficient of TS2 by calculation, the amount of fluctuation can be accurately quantified.

Further, after changing the coherence factor (σ value), which is the ratio of the numerical aperture of the illumination optical system 104 to the numerical aperture of the reduction projection lens 110, the test exposure is repeatedly performed to obtain the coherence factor (σ).
Value), the focus change saturation value K, the time constant TS1,
Each coefficient of TS2 can be calculated.

FIG. 7 is a flowchart of a measurement program for automating test exposure in this embodiment. First,
In step S701, an illumination condition to be measured in advance, a heating condition and a cooling condition of the reduction projection lens for each illumination condition, and a shot position when the test exposure in FIG. 4 is exposed on a substrate (wafer) are set. In step S702, step S
In step 701, the coherence factor (σ value) set in the first illumination condition is read, and in step S703, the illumination optical system aperture stop 105 and the reduced projection lens aperture stop 111 are driven in accordance with the σ value. Next, the process proceeds to step S705, in which the reduction projection lens 11 is used to measure the rising fluctuation.
The process proceeds to step S706 for heating 0. Here, the exposure is performed according to the heating conditions of the parameters set in step S701. At this time, the wafer stage 116 is driven to a position where reflected light hardly enters the reduction projection lens 110.
Next, in step S708, the substrate (wafer) on the wafer stage 116 is driven to the sample exposure position in FIG.
In step S709, sample exposure is performed. Thereafter, step S70 is performed until the sample exposure of the measurement points under the heating conditions is completed.
Steps S709 to S709 are repeated. Next, the sample exposure under the cooling condition for measuring the falling fluctuation is different from that under the heating condition in that the reduction projection lens 110 is naturally cooled for the set time in step S707. As described above, test exposure can be automatically performed for each illumination condition while controlling the amount of energy applied to the projection lens over time.

In the above embodiment, for convenience of explanation,
Although the method for measuring the irradiation fluctuation characteristic of the focus characteristic of the reduction projection lens 110 and the method for obtaining the correction coefficient for quantifying the characteristic fluctuation curve have been exemplified, the present invention is not limited thereto, and the method of sample exposure and If the mask is appropriately selected, the irradiation variation of the magnification and the distortion of the reduction projection lens can of course be measured.

[0038]

[Embodiment of Device Production Method] Next, an embodiment of a device production method using the above-described exposure apparatus will be described. FIG. 8 shows a flow of manufacturing micro devices (semiconductor chips such as ICs and LSIs, liquid crystal panels, CCDs, thin-film magnetic heads, micro machines, etc.). In step 1 (circuit design), a device pattern is designed. Step 2
In (mask production), a mask on which a designed pattern is formed is produced. On the other hand, in step 3 (wafer manufacture), a wafer is manufactured using a material such as silicon or glass. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer by lithography using the prepared mask and wafer. The next step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer produced in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). including. Step 6
In (inspection), inspections such as an operation confirmation test and a durability test of the semiconductor device manufactured in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).

FIG. 9 shows a detailed flow of the wafer process. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. Step 15
In (resist processing), a photosensitive agent is applied to the wafer. In step 16 (exposure), the circuit pattern of the mask is printed and exposed on the wafer by the exposure apparatus having the measuring means for measuring the variation of the imaging characteristics described above. Step 17 (development) develops the exposed wafer. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), unnecessary resist after etching is removed. By repeating these steps, multiple circuit patterns are formed on the wafer.

In this embodiment, in each of the repetitive processes, as described above, by properly measuring the change in the imaging characteristic of the projection optical system due to the exposure heat, accurate alignment can be performed without being affected by the process. It is possible.

By using the production method of this embodiment, it is possible to produce a highly integrated device, which was conventionally difficult to produce, at low cost.

[0042]

As described above, according to the present invention,
It is possible to optimize the correction model formula for the fluctuation of the imaging characteristics of the reduction projection lens due to the exposure energy for each illumination condition in a short time.

[Brief description of the drawings]

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

FIG. 2 is a graph showing an irradiation variation characteristic of an imaging characteristic of the reduction projection lens according to one embodiment of the present invention.

FIG. 3 is a graph showing a variation characteristic of focus according to exposure energy of a reduction projection lens according to an embodiment of the present invention.

FIG. 4 is a diagram showing a wafer shot layout used for sample exposure according to one embodiment of the present invention.

FIG. 5 is a diagram showing a mask pattern for sample exposure according to one embodiment of the present invention.

FIG. 6 is a graph showing focus measurement results during sample exposure according to one embodiment of the present invention.

FIG. 7 is a flowchart showing an operation of test exposure according to one embodiment of the present invention.

FIG. 8 is a diagram showing a flow of manufacturing a micro device.

FIG. 9 is a diagram showing a detailed flow of a wafer process in FIG. 8;

[Explanation of symbols]

101: pulse laser light source, 102: laser control device,
103: main controller of the exposure apparatus, 104: illumination optical system,
105: illumination system aperture stop, 106: half mirror, 10
7: photo sensor, 108: illumination system controller, 109:
Reticle, 110: reduction projection lens, 111: reduction projection lens aperture stop, 112: reduction projection lens aperture stop driving means, 113: field lens driving means, 114: projection lens control device, 115: wafer, 116: wafer stage, 117 : Moving mirror, 118: Laser interferometer, 11
9: wafer stage control means, 120: stage control device, 121, 122: focus plane detection means, 301:
Focus fluctuation prediction curve due to exposure energy irradiation, h
1, h2, h10: measurement points for measuring rising characteristics of focus fluctuation, c11, c12, c20: measurement points for measuring falling characteristics of focus fluctuation, S1 to S11: shot layout of sample exposure for focus measurement,
S701 to S710: Step.

Claims (5)

[Claims] 1. A method according to claim 1, wherein a predetermined pattern formed on the original is transferred via a projection optical system onto a photosensitive substrate located at a position conjugate with the original. A first step of controlling the amount of exposure energy applied to the projection optical system over time and measuring the amount of change in the imaging characteristic of the projection optical system over time, and based on the measurement result of the imaging characteristic, A second step of quantifying the irradiation fluctuation of the projection optical system by function approximation. 2. The projection optical system according to claim 1, wherein the variation in the imaging characteristics of the projection optical system includes at least one of focus, magnification, and distortion. A method for measuring imaging characteristic fluctuation. 3. An illumination system for illuminating an original with illumination light for exposure, a projection optical system for projecting a pattern of the original on a photosensitive substrate with a predetermined image forming characteristic, and an illumination system for illuminating light. In an exposure apparatus including a light source distribution changing unit that changes a distribution of a light source image generated on a pupil plane of a projection optical system,
The light source distribution changing unit changes the distribution of the light source image, controls the amount of energy applied to the projection optical system with time for each light source image distribution, and measures the time-dependent change in the imaging characteristics. First means, based on the measurement result of the imaging characteristics,
Second means for quantifying the irradiation variation of the imaging characteristic by function approximation for each distribution of the light source image, and measuring means for measuring the imaging characteristic variation including the first means and the second means. An exposure apparatus, comprising: 4. The exposure apparatus according to claim 3, wherein the imaging characteristic variation of the projection optical system includes at least one of focus, magnification, and distortion. 5. A method according to claim 1 or 2, wherein a device is manufactured by using the exposure apparatus according to claim 3 or 4. Device manufacturing method.