JPH08288206A - Apparatus and method for exposure - Google Patents

Abstract

PURPOSE: To satisfactorily correct a change, in an optical characteristic, caused by the thermal deformation of a mask by using only a magnification correction means. CONSTITUTION: An irradiation region on a reticle R to be irradiated with exposure light is set by a main blind 52. On the basis of information on the set irradiation region and on the basis of distribution information on a pattern on the known reticle R, infrared rays are irradiated in a state that they have been adjusted by a subblind 60 by an infrared irradiation controller 66 in such a way that a physical quantity regarding the expansion and contraction of the reticle R becomes nearly uniform in the irradiation region when the exposure light is irradiated. In a state that the expansion and contraction of the reticle R has been adjusted in this manner, the magnification of the image of the pattern on the reticle R formed on the wafer is adjusted in a magnification adjusting mechanism on the basis of the physical quantity regarding the expansion and contraction of the reticle R.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure apparatus and an exposure method, and more particularly to an exposure apparatus and an exposure method for forming an image of a pattern formed on a mask on a photosensitive substrate.

[0002]

2. Description of the Related Art Conventionally, in a projection exposure apparatus used for manufacturing a semiconductor integrated circuit or a liquid crystal substrate, the image forming characteristics (for example, magnification and focal position) produced by absorption of exposure light by a projection optical system are In order to correct the change, for example, each lens element forming the projection optical system is moved in the optical axis direction, tilted with respect to a plane orthogonal to the optical axis, or the pressure in the airtight space between the lens elements is adjusted. For example, a means for correcting the image formation characteristic is provided. For example, it is possible to favorably maintain the image forming characteristics caused by the projection optical system absorbing the exposure light based on the changing characteristics of the image forming characteristics (see Japanese Patent Laid-Open No. 63-58349, etc.).

However, since the exposure light beam also passes through the mask, there is a problem that the mask is thermally deformed by the absorption of the exposure light, which causes a change in the image forming characteristic.
In order to improve such a problem, for example, Japanese Patent Laid-Open No. 4-192
In Japanese Patent No. 317, the amount of thermal deformation of the mask due to the absorption of illumination light (exposure light) is obtained, and the change in the image formation state is predicted based on this amount. There is disclosed a technique for minimizing the influence of fluctuations in the image formation state by using the technique.

[0004]

However, in the method of calculating the average amount of expansion and contraction of the mask and correcting the magnification by the magnification correction means, the exposure light irradiation area is set by using the blinds. It is difficult to correct the magnification when a part of the mask is irradiated with light, or when the exposure light absorption has a location dependency due to the nonuniformity of the mask pattern, that is, when the expansion and contraction amount of the mask becomes nonuniform. There was an inconvenience. Further, even if the mask pattern is uniform, there is a disadvantage that the temperature distribution occurs in a shape close to concentric circles from the center of the mask, and the expansion / contraction amount of the mask is not linear.

On the other hand, in the technique disclosed in Japanese Patent Laid-Open No. 4-192317, the amount of thermal deformation of the mask is obtained, and the image formation state is changed by formulating the amount of thermal deformation of the mask based on optical calculation or actual measurement. Since it is necessary to obtain (predict), it is necessary to perform a complicated calculation in order to obtain the change in the image formation state. Further, in the technique described in the above publication, not only the magnification but also the deformation (distortion, etc.) which is not symmetric with respect to the optical axis of the projection optical system can be corrected even if the change in the imaging state can be accurately obtained. There is also an inconvenience that it is not possible to perform sufficient correction for changes in optical characteristics due to thermal deformation of the mask unless a means for correcting the imaging characteristics having a possible complicated configuration is provided.

The present invention has been made in view of the inconveniences of the prior art, and an object thereof is to correct a magnification variation without performing a complicated calculation for obtaining a change in an image formation state. It is an object of the present invention to provide an exposure apparatus and an exposure method capable of excellently correcting a change in optical characteristics caused by thermal deformation of a mask.

[0007]

As in the prior art, when the change in the imaging characteristics due to the thermal deformation of the mask is not calculated accurately, but the amount of thermal deformation of the mask is made uniform, It is possible to satisfactorily correct the change in the optical characteristics due to the thermal deformation of the mask only by the magnification correction means. That is, the thermal deformation of the mask is not allowed to freely occur, but the thermal deformation of the mask is intentionally applied so as to easily correct the change in the imaging state of the mask pattern. Changes in state can be easily corrected. The present invention has the following configuration based on this solution principle.

According to a first aspect of the invention, the mask is irradiated with light having a first wavelength characteristic emitted from a light source for exposure,
An exposure apparatus for forming an image of a pattern on the mask on a substrate coated with a photosensitizer, and an irradiation area setting means for setting an irradiation area on the mask which is irradiated with light having the first wavelength characteristic. And a physical quantity related to expansion and contraction of the mask at the time of irradiation with light having the first wavelength characteristic based on the set irradiation area information and known pattern distribution information on the mask. An expansion / contraction adjusting unit that adjusts the expansion / contraction of the mask so as to be uniform; and a magnification adjustment system that adjusts the magnification of the image of the pattern of the mask based on a physical quantity related to the expansion / contraction of the mask.

In this case, the expansion / contraction adjusting means is
The light having the second wavelength characteristic based on the light source that emits the light having the second wavelength characteristic that is not exposed to the photosensitive agent, and the information about the set irradiation area and the known pattern distribution information on the mask. And a second irradiation area setting means for setting an irradiation area on the mask which is irradiated by.

Alternatively, the expansion / contraction adjusting means adjusts the temperature of the heater on the basis of a heater arranged in the peripheral portion of the mask, information on the set irradiation region and pattern distribution information on the mask. The temperature control system may be included.

The magnification adjusting system further comprises an input means for inputting the energy of light having the first wavelength characteristic, a magnification adjusting mechanism for changing the magnification of an image of the mask pattern, and the first input. The control system for controlling the magnification adjusting mechanism based on the energy of light having the wavelength characteristic and the physical quantity related to the expansion and contraction of the mask.

Further, the image of the pattern of the mask may be formed on the photosensitive substrate via a projection optical system, and in such a case, the magnification adjusting system changes according to energy absorption of the projection optical system. It is desirable that the means is a means for adjusting changes in the image forming characteristics of the projection optical system.

According to a sixth aspect of the present invention, there is provided an exposure apparatus which irradiates a mask having a mask protection member having a thin film and a frame member with exposure light to form an image of a pattern on the mask on a photosensitive substrate. And a temperature sensor that detects the temperature of the space formed by the mask protection member and the mask or the temperature of the mask protection member; and adjusts the temperature of the space or the mask protection member based on the output of the temperature sensor. And a temperature adjusting mechanism for controlling the temperature.

According to a seventh aspect of the present invention, in an exposure method of irradiating a mask with exposure light to form an image of a pattern on the mask on a photosensitive substrate, a physical quantity relating to expansion and contraction of the mask is at least the physical amount on the mask. The image of the pattern is formed on the photosensitive substrate in a state where the expansion and contraction of the mask is adjusted so as to be substantially uniform in the irradiation region of the exposure light.

[0015]

According to the first aspect of the invention, the irradiation area setting means sets the irradiation area on the mask which is irradiated with the light (exposure light) having the first wavelength characteristic. In the expansion / contraction adjusting means, a physical quantity related to expansion / contraction of the mask at the time of irradiation with light having the first wavelength characteristic (for example, temperature of the mask, expansion / contraction) based on the set irradiation area information and known pattern distribution information on the mask. The expansion or contraction of the mask is adjusted by making the amount, or the conversion value of the temperature into the expansion or contraction amount, etc., substantially uniform at least in the irradiation region on the mask. With the expansion and contraction of the mask adjusted in this way,
The magnification adjustment system adjusts the magnification of the image of the mask pattern based on the physical quantity related to the expansion and contraction of the mask.

In this state, when the mask is irradiated with the light having the first wavelength characteristic emitted from the light source for exposure, the magnification of the image of the pattern on the mask is adjusted and the substrate coated with the photosensitizer ( Hereinafter, it is formed on a "photosensitive substrate".

According to this, the magnification of the pattern image is adjusted by the magnification adjusting system at the stage when the expansion and contraction of the mask is adjusted (adjusted so as to have a uniform expansion and contraction amount). It is possible to satisfactorily correct the change in the image formation state of the mask pattern caused by the thermal deformation of the mask, without performing the complicated calculation for obtaining and only by correcting the magnification variation.

According to the sixth aspect of the invention, the temperature sensor detects the temperature of the space formed by the mask protection member and the mask or the mask protection member. The temperature adjustment mechanism adjusts the temperature of the space or the mask protection member based on the output of the temperature sensor.

Therefore, when the temperature of the space formed by the mask protection member and the mask or the mask protection member becomes higher than that of other portions of the mask due to the irradiation of the exposure light, the temperature of the space or the mask protection member. Is adjusted by the temperature adjusting mechanism so that the temperature is approximately equal to that of other portions.

According to the seventh aspect of the invention, the pattern image is exposed in a state where the expansion and contraction of the mask is adjusted so that the physical quantity related to the expansion and contraction of the mask becomes substantially uniform at least in the exposure light irradiation area on the mask. It is formed on a substrate. Therefore, only by correcting the magnification of the image of the pattern to be formed, it is possible to satisfactorily correct the change in the optical characteristics due to the thermal deformation of the mask, and the mask pattern can be accurately formed on the photosensitive substrate. Can be overlaid.

[0021]

【Example】

<< First Embodiment >> A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of a projection exposure apparatus 10 as an exposure apparatus according to the first embodiment.

In this projection exposure apparatus 10, a wafer stage 12 that moves two-dimensionally in a plane orthogonal to the paper surface (in the XY plane) in FIG. 1, and an optical axis AX are arranged orthogonal to the movement plane of the wafer stage 12. A projection lens PL as a projection optical system, a reticle R as a mask arranged above the projection lens PL, and a main light source 14 as a light source for exposure that emits light (exposure light) having a first wavelength characteristic. , A sub-light source 16 as a light source for emitting light having the second wavelength characteristic, an irradiation optical system for the exposure light IL, an irradiation optical system for the light having the second wavelength characteristic, a magnification adjusting mechanism 18, and control of these. It is equipped with a system.

The wafer stage 12 is provided with a stage drive unit 20 including a motor (not shown). The moving position of the wafer stage 12 is detected by a light wave interferometer (not shown), and the stage drive unit 20 is driven and controlled by the main control unit 22 based on the output of the light wave interferometer. Stage 12
Is configured to move two-dimensionally on the X and Y coordinate axes.
A wafer holder 24 is provided on the wafer stage 12, and a wafer W as a photosensitive substrate is held on the wafer holder 24 by vacuum suction.

A dose sensor 26 is installed on the wafer stage 12. The light receiving surface (measurement surface) of the irradiation amount sensor 26 and the surface of the wafer W have substantially the same height. The irradiation amount sensor 26 can measure the power (energy) of the exposure light IL applied to the wafer W via the projection lens PL.

As the projection lens PL, a bilateral telecentric projection lens is used in the present embodiment, and this projection lens PL is actually the optical axis AX direction (Z direction).
It is configured to include a plurality of lens elements (all of which are not shown) arranged along.

The reticle R is an optical axis AX of the projection lens PL.
It is held on a reticle stage 28 that makes fine movements in the X, Y, and θ directions in a plane orthogonal to. The pattern surface of the reticle R is conjugate with the surface of the wafer W with respect to the projection lens PL.

The main light source 14 includes, for example, an ultrahigh pressure mercury lamp, an excimer laser (KrF, ArF), a YAG laser, etc., and g-line, i-line, excimer light (wavelength 248 nm:
Light (exposure light) IL having a first wavelength characteristic that sensitizes a resist as a photosensitizer applied on the wafer W, such as KrF, 193 nm: ArF), a harmonic of a YAG laser (wavelength of 200 nm or less), is generated.

The irradiation optical system for irradiating the reticle R with the exposure light IL includes a mirror 30 that reflects the exposure light IL emitted from the main light source 14 and bends the exposure light IL horizontally, and the exposure light IL reflected by the mirror 30. A fly-eye optical system 32 including an optical integrator (fly-eye lens) and the like, a relay optical system 34, and a dichroic mirror 36 obliquely installed at an angle of about 45 degrees above the reticle R. A main condenser lens 38 arranged between the dichroic mirror 36 and the reticle R,
It is configured to include. A shutter 40 that opens and closes the optical path of the exposure light IL is provided between the main light source 14 and the mirror 30, and the shutter 40 is driven by a shutter control circuit 44 via a drive unit 42. There is. Also, at the exit of the fly-eye optical system 32,
An illumination system diaphragm 46 is arranged. Further, a half mirror (beam splitter) 48 is arranged between the illumination system diaphragm 46 and the relay optical system 34, and a part of the exposure light IL reflected by the half mirror 48 is P.
The power (energy) of the exposure light IL is monitored by being measured by an integrator sensor (power monitor) 50 such as an IN photodiode.

Further, in the relay optical system 34, there is provided a main blind 52 for setting the incident area of the exposure light IL on the reticle R, and the main blind 52 is conjugated with the pattern surface of the reticle R. It is located in. The main blind 52 is driven by the main blind drive unit 54. In the first embodiment, the main blind 52 and the main blind drive unit 54 constitute irradiation area setting means.

As the sub light source 16, a light source which emits light of the second wavelength characteristic which does not expose the resist, infrared rays IR in this embodiment, is used.

The irradiation optical system for irradiating the reticle R with this infrared IR is composed of an optical system 56, a relay optical system 58, and the above-mentioned main condenser lens 38. In the relay optical system 58, a sub blind 60 is provided at a position conjugate with the pattern surface of the reticle R. The sub blind 60 is composed of photoelectric elements (hereinafter referred to as “liquid crystal element”) 60A such as liquid crystal elements and photochromic elements arranged in a matrix of 16 rows and 16 columns as shown in FIG. Each liquid crystal element 60A is
It is adapted to be turned on / off independently (ON / OFF) by an electric signal from the sub blind driving unit 62. Therefore, the sub-blind driving unit 62 can transmit or block the infrared IR emitted from the sub-light source 16 at any position of the sub-blind 60.

The magnification adjusting mechanism 18 is for correcting variations in optical characteristics (magnification) due to incidence of exposure light (specifically, light transmitted through the reticle R) IL of the projection lens PL. As the magnification adjusting mechanism 18, a mechanism that increases or decreases the pressure in the airtight space between the specific lens elements forming the projection lens PL is used in this embodiment. In addition,
As this magnification adjusting mechanism, for example, one that drives, tilts, or rotates some lens elements constituting the projection lens PL in the optical axis AX direction by a driving element such as a piezoelectric element or a magnetostrictive element is used. Good.

The control system of the projection exposure apparatus 10 includes the shutter control circuit 44 and the magnification correction controller 6 described above.
4, an infrared irradiation controller 66, a main controller 22 for controlling the entire apparatus, and the like.

Of these, the infrared irradiation controller 66 is
It is composed of a microcomputer and the like. The infrared irradiation controller 66 includes a shutter opening / closing control signal from the shutter control circuit 44 and an integrator sensor 5.
The energy value detected at 0 and the main blind drive unit 54
The information of the irradiation area of the exposure light IL on the reticle R set by is input. Further, the distribution information of the pattern on the reticle R is stored in advance in the internal memory of the infrared irradiation controller 66.

As the distribution information of the pattern on the reticle R, for example, the irradiation amount sensor 26 is composed of a photodiode array or the like, and the pattern region of the reticle R is divided into a large number of blocks using the irradiation amount sensor 26. The reticle transmittance of the exposure light IL of the block is measured in advance by taking the ratio of the value of the dose sensor 26 with the reticle R to the value of the dose sensor 26 without the reticle R, and for each block. The existence rate of the pattern can be obtained and used as the distribution information of the pattern. Alternatively, the light receiving surface of the irradiation amount sensor 26 is set to an area corresponding to each divided block and the irradiation amount sensor 26 is set to the projection lens P.
Wafer stage 12 so as to be two-dimensionally scanned below L
May be controlled to obtain the ratio of the pattern for each block by taking the ratio of the value of the dose sensor 26 with the reticle R to the value of the dose sensor 26 without the reticle R. .

In the infrared irradiation controller 66, the exposure light I on the reticle R set by the main blind drive unit 54 is used.
Based on the information of the irradiation area of L and the pattern distribution information stored in the internal memory, the distribution of the expansion / contraction amount (thermal deformation amount) generated on the reticle R by the irradiation of the exposure light IL is predicted before exposure, and The sub-blind drive unit 62 is controlled as will be described later based on the predicted distribution of the expansion / contraction amount.

A shutter opening / closing control signal is input from the shutter control circuit 44 to the magnification correction controller 64. The specific control operation of the magnification controller 64 will be described later. Further, the main control unit 22 has a reticle R
The type of light-shielding member such as chrome that forms the pattern, heat absorption coefficient, thermal expansion coefficient, etc. are input in advance from a keyboard,
It is stored in that memory.

Next, the first book constructed as described above
The operation of the embodiment will be described.

In the step of transferring the pattern of the reticle R onto the wafer W, prior to the actual exposure of the exposure shot of the wafer W, the main blind drive unit 54 makes a predetermined opening based on an instruction from the main control unit 22. When the main blind 52 is driven to set the irradiation area of the exposure light IL, information on the set irradiation area (main blind 5
2 opening information) is sent to the infrared irradiation controller 66. Further, the output of the integrator sensor 50 is always input to the infrared irradiation controller 66. The output of the integrator sensor 50 is also output to the main controller 22. The main control unit 22 controls the exposure amount (blind open time) based on the output of the integrator sensor 50.

The infrared irradiation controller 66 calculates the distribution of the expansion / contraction amount (thermal deformation amount) generated in the reticle R due to the absorption of the exposure light IL based on the irradiation area information and the known pattern distribution information.

For example, when the pattern on the reticle R has a uniform distribution, the reticle R expands greatly in the area irradiated with the exposure light IL, and the reticle R expands much in the area not irradiated with the exposure light IL. Not expected to.
Therefore, the infrared irradiation controller 66 controls the sub blind drive unit 62 based on this prediction result to set the transmission portion of the sub blind 60 so as to be inverted from the opening of the main blind 52. For example, when the exposure light IL is applied to the central portion of the reticle R (area shown in black in FIG. 2) through the opening of the main blind 52, as shown in FIG. Area 60 shown in black in FIG. 2)
The transmissive part of the sub blind 60 is set so that B is opaque and the outer peripheral part (region shown by the matrix in FIG. 2) 60C is transmissive. As a result, at the time of actual exposure, infrared rays are emitted to the area where the exposure light IL is not emitted, and the expansion / contraction amount (expansion amount) of the reticle R becomes generally isotropic and nearly uniform.

Further, for example, the central portion of the reticle R (see FIG.
The area 60B ₁ shown in black and the area 60D ₁ shown in diagonal lines are irradiated with exposure light, and the pattern existence rate of the upper right portion 60D ₁ in the pattern area of the reticle R in FIG. 3 is small. In the case of the pattern distribution, since the expansion amount of the portion is also expected to be very small, the infrared irradiation controller 66 irradiates the portion 60D ₁ with the exposure light IL and the infrared IR, and the outer peripheral portion 60C described above. _The sub-blind driving unit 62 so that the infrared IR is radiated to ₁
Control. That is, the outer peripheral portion 60C ₁ and the upper right portion 60
The transparent portion of the sub blind 60 is set as shown in FIG. 3 so that D ₁ becomes transparent. Also in this case, when the reticle R is irradiated with the exposure light IL during the actual exposure, the expansion / contraction amount (expansion amount) of the reticle R is generally isotropic and nearly uniform. As described above, in the first embodiment, the sub blind 60, the sub blind driving unit 62, and the infrared irradiation controller 66 make the second blind
This irradiation area setting means is configured, and further, the second irradiation area setting means and the sub light source 16 configure expansion / contraction adjusting means.

By irradiating the reticle R with the infrared rays IR as described above, the expansion / contraction amount (or heat distribution) of the reticle R becomes substantially uniform over the entire reticle.

Since the expansion / contraction amount (or heat distribution) of the reticle R is substantially uniform over the entire reticle, the projected image of the reticle pattern due to the thermal expansion of the reticle changes its magnification approximately isotropically (with the center of the reticle as a reference). Change to be point symmetric). Therefore, after the expansion / contraction amount (or heat distribution) of the reticle R becomes substantially uniform over the entire reticle, only the change in magnification of the projected image of the reticle pattern need be corrected.

Since it can be considered that the reticle R expands and contracts substantially uniformly, the magnification correction controller 64 is operated by the main controller 2
The expansion / contraction amount of the reticle R at the time of exposure is calculated from the thermal expansion coefficient of the pattern of the reticle R and the energy of the exposure light stored in the second memory.

The relationship between the amount of expansion and contraction of the reticle R pattern at the time of exposure and the change in magnification of the projected image of the reticle pattern is previously determined by experiment or calculation, and then this reticle R
The change in magnification of the projected image of the reticle pattern is calculated based on the actual amount of expansion and contraction.

The relationship between the control amount of the magnification adjusting mechanism 18 and the change in the projected image of the reticle pattern is previously obtained by experiments or calculations, and the magnification correction controller 64 determines that the change in the projected image of the reticle pattern is substantially zero. The magnification adjusting mechanism 18 is controlled so that Specifically, the magnification adjusting mechanism 18 changes, for example, the refractive index of the gas between the lens elements in a specific portion of the projection optical system PL (changes the pressure of the gas), or causes the lens element to move to the light of the projection optical system PL. It moves and rotates along the axis or in a plane perpendicular to the optical axis.

The amount of expansion and contraction of the reticle R when the exposure light enters the reticle R is determined based on the irradiation area set by the frind 22, pattern distribution information, and the thermal expansion coefficient of the pattern. Find the amount of expansion and contraction,
Based on this actual expansion / contraction amount, the main control unit 22 controls both the expansion / contraction adjusting means and the magnification adjusting mechanism 18.

In the case of the first embodiment, since the output of the integrator sensor 50 is always input to the infrared irradiation controller 66, the intensity of the exposure light IL can be known. In the infrared irradiation controller 66 using the intensity of this exposure light, for example, by the method disclosed in Japanese Patent Laid-Open No. 4-192317, the type of the light shielding member such as chrome forming the pattern of the reticle R and the heat absorption rate. In consideration of the above, it is also possible to obtain the actual amount of expansion and contraction of the reticle R by numerically calculating the thermal deformation amounts at several representative points in the reticle R. In this case, since the infrared irradiation controller 66 can more accurately predict the distribution of the expansion / contraction amount of the reticle R, the sub-blind 60 is subdivided into 16 rows and 16 columns or more to obtain the expansion / contraction amount distribution. Accordingly, it is desirable that the on / off control of each liquid crystal element 60A forming the sub blind 60 is performed more precisely.

Before the exposure of the exposure shot of the wafer W is started,
After the main blind 52 and the sub blind 60 are set by the procedure described above, the main control unit 22 moves the wafer stage 12 via the stage drive unit 20 so that the irradiation amount sensor 26 is located below the projection lens PL. To drive. Then
When the main control unit 22 opens the shutter 40 via the shutter control circuit 44, the sub-light source 16 is turned on by the infrared irradiation controller 66 based on the opening / closing control signal of the shutter 40, and the infrared IR along with the exposure light IL reticle R. And the irradiation amount sensor 26 is irradiated via the projection lens PL. In the dose sensor 26, the reticle R and the projection lens P
The amount of light passing through L is measured. The output of the dose sensor 26 is input to the main controller 22. The main controller 22 stores the measured value of the irradiation amount sensor 26 in the memory, and the main controller 22 controls the infrared irradiation controller 66.
It will also be sent to. The main control unit 22 is always
Since the output of the integrator sensor 50 is monitored, the infrared irradiation controller 66 corrects the energy (light amount) of the infrared IR so that the ratio between the output value of the integrator sensor 50 and the output value of the irradiation amount sensor 26 becomes constant. To do. As a result, it is possible to cancel the temporal change of the image plane power due to deterioration of the main light source 14.

When the preparation is completed in this way, the main controller 22 positions the wafer stage 12 on the first shot on the wafer W within the projection field of the projection lens PL based on the shot arrangement coordinates of the wafer W. The reticle pattern is transferred (exposed) on the first shot by controlling the shutter control circuit 44. When the exposure in this transfer process starts, the infrared irradiation controller 66 also manages the turning on and off of the sub light source 16 so that the infrared reticle R is irradiated with the infrared light IR from the sub light source 16 in synchronization with the opening and closing of the shutter 40.

During the exposure, the exposure light IL emitted from the main light source 14 is
When the shutter 14 is in the open state, it is reflected by the mirror 30, passes through the fly-eye optical system 32 and the relay optical system 54, is reflected by the dichroic mirror 36, is condensed by the condenser lens 38, and enters the reticle R. At this time, if the irradiation region of the exposure light IL is set by the main blind 52 so as to be substantially coincident with the pattern region of the reticle R, the pattern formed on the reticle R is conjugated via the projection lens PL. Wafer W in position
Is transferred to Then, the pattern of the reticle is sequentially transferred onto the wafer W by repeating the movement of the wafer stage 12 and the exposure.

In this way, the pattern of the reticle R is transferred onto the wafer by the so-called step-and-repeat method by the main control section 22. During this exposure, the reticle R is controlled by the infrared irradiation controller as described above.
The amount of expansion and contraction is adjusted to be uniform. Along with this, a magnification controller 64 is used to perform a known method, for example, JP-A-60-78454 or JP-A-62-13682.
By the following method as disclosed in Japanese Patent Laid-Open No. 1 etc., the variation of the image forming characteristic due to the thermal deformation of the projection lens PL due to the absorption of the exposure light IL and the infrared ray IR, for example, the optical characteristic (magnification) of the projection lens is corrected. .

That is, in the internal memory of the magnification correction controller 64, the time constant (attenuation characteristic) on the magnification variation characteristic of the projection lens PL, and the entire exposure light IL mainly transmitted through the previously measured projection lens PL are measured. The amount of light (energy),
Data such as a change in magnification (coefficient) with respect to the pressure adjustment amount is stored in advance. That is, in this embodiment, the internal memory that stores the energy (value) of the exposure light in advance functions as the input unit. After the energy of the exposure light is measured in advance, a keyboard or the like may be provided as an input means to perform key input.

In the magnification correction controller 64, a signal representing the duty ratio within a unit time (sampling time) between the open state and the closed state of the shutter 40 is input from the shutter control circuit 44 to predict the fluctuation of the imaging characteristic at the present time. Information is produced, and the magnification adjusting mechanism 18 is controlled based on the information and the relationship between the pressure adjustment amount and the magnification change.

More specifically, in the magnification correction controller 64, the energy of the exposure light, the duty ratio, and the exposure light IL incident within the unit time are calculated using the proportional constants obtained in advance by experiments or the like. The variation amount corresponding to the cumulative energy amount is calculated, the attenuation value after the lapse of the unit time of the variation amount at the end of the previous unit time is read from the memory, and the variation amount is calculated as the total value of these.
When calculating the above-mentioned attenuation value, the time constant (attenuation characteristic) on the above-mentioned magnification variation characteristic is used.

Then, in the magnification correction controller 64,
Based on the variation amount obtained above, the magnification adjusting mechanism 18 is controlled so as to correct only the variation amount caused by the incidence of the exposure light IL and the infrared light IR on the projection lens PL, and the specific configuration of the projection lens PL is controlled. Controls the pressure in the airtight space between the lens elements.

The magnification correction controller 64 repeats such magnification correction control at unit time intervals until the exposure is completed. As a result, the magnification adjustment mechanism 18 corrects the variation in magnification from time to time. As described above, in the first embodiment, the magnification adjustment mechanism 18 and the magnification correction controller 64 are provided.
By using, even the change of the image forming characteristic of the projection lens PL which is changed by the energy absorption of the projection lens PL is also corrected.

As described above, according to the first embodiment, as described above, the infrared irradiation controller 66 controls the irradiation of the infrared IR to the reticle R in synchronization with the opening / closing of the shutter 14 and the exposure light. Since the infrared ray IR is emitted from the sub-light source 16 to the reticle R so that the expansion and contraction amount of the reticle R due to the absorption of IL becomes isotropic and uniform as a whole, the reticle R is not unevenly deformed by heat. Therefore, the reticle R can be corrected by simply correcting the projection magnification by the magnification correction controller using the method described above.
It is possible to satisfactorily correct the optical characteristics due to the thermal deformation of the.

In the implementation, the radiated infrared IR is not incident on the projection lens PL so that the radiated infrared IR is absorbed by the projection lens PL so that the imaging characteristics of the projection lens PL are not affected as much as possible. It is more desirable to have such a configuration of the optical system, for example, a configuration in which the mask is irradiated with infrared rays from an oblique direction.

Further, by installing a shutter and an integrator sensor on the side of the sub light source 16 as well, fine control is possible.

<< Second Embodiment >> Next, a second embodiment of the present invention will be described with reference to FIGS. Here, the same reference numerals will be given to the same or equivalent components as those in the first embodiment described above, and the description thereof will be simplified or omitted.

FIG. 4 schematically shows the structure of a projection exposure apparatus 70 as an exposure apparatus according to the second embodiment.
In this embodiment, the sub-light source 16 and its peripheral components in the first embodiment are omitted, and the infrared irradiation controller 6 is omitted.
In place of 6, a reticle temperature controller 72 as a temperature control means and a plurality (here, eight) of heaters 74a,
74b, 74c, 74d, 74e, 74f, 74g, 7
The feature is that 4h (see FIG. 5) is provided.

The heaters 74a to 74h are, as shown in FIG. 5, a platen portion 28A of the reticle stage 28.
The heaters 74a to 74h heat (heat) the reticle R, respectively. These heaters 74
A to 74h are independently controlled by the reticle temperature controller 72. In this embodiment, the temperature is adjusted at eight locations, but the temperature adjustment location may be arbitrarily selected in consideration of accuracy.

Next, the temperature control of the reticle R by the reticle temperature control controller 72 will be described.

First, before exposure, the reticle temperature control controller 72 estimates the distribution of the expansion / contraction amount of the reticle R from the irradiation area information from the main blind drive section 54 and the known pattern distribution information on the reticle R. The distribution of this expansion / contraction amount may be obtained by obtaining several patterns of the model from several types of reticle R and the result of printing at the time of adjustment and selecting the closest one from the several patterns at the time of actual exposure.

Since the distribution of the expansion / contraction amount is considered to be proportional to the temperature distribution of the reticle R, the reticle temperature adjustment controller 72 ensures that the temperature on the reticle R is uniform, that is, the expansion / contraction amount is the reticle R. The heaters 74a to 74h are controlled so that the entire surface is isotropic and uniform.

FIG. 6 shows the relationship between the actual temperature distribution curve (temperature distribution model) and the correction temperature curve for temperature adjustment in the O--A section of FIG. The temperature control of this embodiment will be described in more detail with reference to FIG.

First, in the reticle temperature controller 72, the temperature distribution curve RT1 of the reticle R due to the absorption of the exposure light IL is calculated in advance based on the pattern distribution information near the OA cross section and the irradiation area information of the reticle R. (presume).

Next, based on this estimated temperature distribution curve RT1, after correction, the temperature distribution curve RT2 becomes OA
A correction temperature distribution curve HT is calculated so that the temperature is constant on the cross section, and the heater 74d is controlled so that the same temperature correction as the correction temperature distribution curve HT can be performed. The above model calculation and heater control are performed for all heaters 74.
By performing the process for a to 74h, the temperature distribution of the reticle R becomes almost uniform over the entire surface, and the expansion and contraction amount is the first.
Similar to the example, the state is isotropic and nearly uniform.

For example, as in the case of FIG. 3, the reticle R
When it is necessary to make the upper right part of the heater have a higher temperature, the desired temperature control effect can be obtained by setting the temperatures of the heaters 74b, 74c, and 74d higher than the other temperatures.

The structure and operation of the other parts are the same as in the first embodiment. As is apparent from the above description, in the second embodiment, the expansion / contraction adjusting means is constituted by the heaters 74a to 74h and the reticle temperature adjustment controller 72.

As described above, according to the second embodiment, the same effect as that of the first embodiment can be obtained, and infrared rays can pass through the reticle R and project the projection lens PL as in the first embodiment.
Since the projection lens PL and the like change little from the normal temperature, the imaging performance (such as aberrations and other aberrations) due to the infrared absorption of the projection lens PL does not deteriorate, and the temperature control is performed. Since the expansion amount of the reticle R can be calculated from the subsequent temperature distribution curve RT2, more accurate magnification correction can be performed by the same method as in the first embodiment.

In the first and second embodiments, the reticle R (mask) is projected via the projection lens PL (projection optical system).
The case where the present invention is applied to the projection exposure apparatus that transfers the above pattern onto the wafer (photosensitive substrate) has been illustrated, but the applicable range of the present invention is not limited to this, and a projection optical system is not used. It can also be applied to a proximity type exposure apparatus. Even in these cases, when the exposure light is applied to a part of the mask, the amount of thermal deformation of the mask is not uniform, and therefore the amount of expansion and contraction of the mask needs to be uniform. . In such a case, if the information of the irradiation area of the exposure light on the mask and the distribution information of the pattern on the mask are known, the infrared irradiation and the temperature control by the heater as described in the above embodiment are based on these. Thereby, the expansion and contraction of the mask can be made uniform. Then, a change in magnification caused by thermal deformation (uniform thermal deformation) of the mask may be corrected by changing the distance between the mask and the wafer.

Further, in the first embodiment described above, the projection lens P which changes due to the energy absorption of the projection lens PL by the magnification adjustment mechanism 18 and the magnification correction controller 64.
Although the case where the magnification correction system that corrects even the change in the image forming characteristic of L is configured is illustrated, the present invention is not limited to this. A magnification adjusting mechanism that changes the magnification of the image of the pattern on the mask formed on the photosensitive substrate, and the magnification adjusting mechanism is controlled based on the energy of the exposure light and a physical quantity related to the expansion and contraction of the mask, for example, the temperature of the mask. Even if the magnification correction system is configured by the control system, the magnification of the image of the pattern on the mask formed on the photosensitive substrate can be adjusted sufficiently accurately. Therefore, in the state after the expansion and contraction of the mask are made uniform, such a configuration of the magnification adjusting system is also effective.

Further, the adjustment for equalizing the expansion / contraction amount of the reticle R as described in the first and second embodiments is sufficient if it is performed within the irradiation area of the exposure light IL on the reticle R. However, it is not always necessary to perform the entire reticle R.

In the apparatus of the first and second embodiments, the reticle R is placed above the mirror (dichroic mirror) 36 as shown by phantom lines in FIGS.
Is provided with a sensor (temperature distribution sensor) 200 for measuring the heat distribution of the liquid crystal element 60A constituting the sub blind 60 according to the heat distribution of the reticle R measured by the sensor 200. May be. In this case, if the sensor 200 for measuring the heat distribution has a resolution of, for example, 16 rows and 16 columns or more, the sub blind 60 may be subdivided into 16 rows and 16 columns or more to control ON / OFF of each liquid crystal element 60A. Good.

<< Third Embodiment >> Next, a third embodiment of the present invention will be described with reference to FIGS. This third
In the embodiment, the auxiliary light source 16 and its peripheral components are omitted from the first embodiment, and a pellicle 80 as a mask protection member described later is mounted on the reticle R, and the temperature inside the pellicle 80 is detected. Temperature sensor 82
(See FIG. 9) and temperature adjusting means for adjusting the inside of the pellicle 80 to a predetermined temperature based on the output of the temperature sensor 82 are characterized in that they are provided. Is the same as in the first embodiment. Therefore, only the above-mentioned characteristic portions will be described here.

FIG. 7 shows a state in which the pellicle 80 is mounted on the reticle R. Here, pellicle 80
Is for avoiding the formation of an image of a foreign substance on the wafer. It has a transparent protective film (thin film) and a predetermined height, and the protective film has a predetermined distance from the reticle in the optical axis direction of the projection optical system. And a frame member for mounting separately. As this protective film, a thin film (for g-line or i-line) having transparency to exposure light is used. The pellicle 80 prevents foreign matter from adhering to the reticle R and defocuses the protective film by a predetermined distance in the optical axis direction from the reticle. Therefore, the image of the foreign matter adhering to the protective film is on the wafer. Not formed.

When exposure is performed with the pellicle 80 mounted on the reticle R as shown in FIG. 7, the pellicle 80 is exposed.
The heat is accumulated inside the reticle R and the temperature of the reticle R rises (in the experiment, the temperature rises 1.5 times as compared with the case without the pellicle), and the unevenness of the temperature distribution of the reticle R becomes large.

In this embodiment, as shown in FIG. 7, an intake hole 84A and an exhaust hole 84B are provided at positions facing each other of a frame serving as a frame member of the pellicle 80. Also, on the reticle stage 28,
An intake nozzle 88 and an exhaust nozzle 90 are provided outside the holes 84A and 84B, respectively. The intake nozzle 88 and the exhaust nozzle 90 are driven by the drive unit 86 (see FIG. 9) in the directions of arrows A and B or in the opposite direction, and the holes 8
It can be inserted into and removed from the inside of 4A and 84B.

FIG. 9 shows the structure of the temperature adjusting means 100 including the intake nozzle 88 and the exhaust nozzle 90.

The temperature adjusting means 100 mainly comprises a pellicle temperature adjusting controller 92 composed of a microcomputer. A pressure sensor 94 and the temperature sensor 82 described above are connected to the input side of the pellicle temperature control controller 92. These sensors 94, 82
Is provided at the tip of the exhaust nozzle 90.

A drive unit 86 is connected to the output side of the pellicle temperature control controller 92, and an intake nozzle 88 and an exhaust nozzle 90 are connected to the drive unit 86. Therefore, the intake nozzle 88 and the exhaust nozzle 90 are driven and controlled by the pellicle temperature control controller (not shown) via the drive unit 86 as described above. Further, an intake / exhaust device 96 including a compressor, an exhaust system, an intake system and the like (not shown) is connected to the output side of the pellicle temperature controller 92. An intake valve and an exhaust valve are provided in the exhaust system and the intake system, respectively.

The operation of the third embodiment thus constructed will be described. The reticle R having the pellicle 80 mounted thereon is conveyed by a reticle loader (not shown), and is transferred onto the reticle stage 28 as shown in FIG.
In this case, the reticle R is supported at four points by reticle holding members (not shown) provided at the four corners of the reticle stage 28. Reticle stage 28
When the reticle R is transferred onto the reticle R, the reticle stage is finely moved in the X, Y, and θ directions based on a signal from a reticle alignment system (not shown), and reticle alignment is performed.

When this reticle alignment is completed,
The pellicle temperature control controller 92 drives the intake nozzle 88 and the exhaust nozzle 90 in the directions of arrows A and B via the drive unit 86. As a result, the tips of the intake nozzle 88 and the exhaust nozzle 90 are inserted into the pellicle 80 through the holes 84A and 84B, respectively (see FIG. 8).

In this state, when the exposure starts, the temperature inside the pellicle 80 gradually rises, so the pellicle temperature controller 92 activates the intake / exhaust device 96 based on the output of the temperature sensor 82. At this time, the intake valve and the exhaust valve are opened. As a result, the cooling air is discharged from the exhaust nozzle 90 into the pellicle 80, and the air inside the pellicle 80 is sucked into the pellicle 80 by the intake nozzle 88 and discharged to the outside. As a result, the inside of the pellicle 80 is cooled and the temperature difference between the reticle R and other parts is relaxed, and the temperature distribution of the reticle R becomes close to a uniform distribution.

Therefore, the optical characteristic (magnification) caused by the thermal deformation of the reticle R can be corrected by the magnification adjusting mechanism 18 in the same manner as in the first and second embodiments described above.

Although the third embodiment has exemplified the case where the inside of the pellicle 80 is cooled based on the output of the temperature sensor 82, the reticle expansion / contraction model (or the reticle expansion / contraction model as described in the first and second embodiments described above). It is also possible to create a temperature rise model) and calculate the temperature of the cooling air based on this.

Strictly speaking, since there is a temperature difference between the air in the pellicle and the reticle R due to heat transfer,
If the temperature inside the pellicle 80 is lowered so as to intentionally cancel the temperature difference so as to suppress the partial thermal expansion of the reticle R, the temperature distribution of the reticle R becomes closer to a uniform distribution.

In the third embodiment, the temperature sensor 8
Although the case where the temperature of the internal space of the pellicle 80 (the space formed by the reticle R and the pellicle 80) is detected by 2 is illustrated, the temperature of the pellicle 80 itself (for example, the temperature of the frame member of the pellicle 80 is detected by the temperature sensor 82. ) May be detected.

In practice, an openable / closable lid is provided inside the holes 84A, 84B provided in the frame of the pellicle 80, and the lid is always urged outward by a spring. This is desirable from the viewpoint of preventing the foreign matter from adhering to the reticle R, which is the original purpose of the pellicle, and preventing the formation of an image of the foreign matter on the wafer.

[0093]

As described above, according to the present invention,
Satisfactory correction for changes in optical characteristics due to thermal deformation of the mask is performed without performing complicated calculation for obtaining changes in the image formation state and only by providing a magnification correction unit having a simple structure. It has an excellent effect that is not possible in the past.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic configuration of a projection exposure apparatus according to a first embodiment.

FIG. 2 is a plan view showing a configuration example of the sub blind of FIG. 1, and is a diagram showing a setting state when exposure light is irradiated to the central portion of the reticle in the case of uniform pattern distribution.

FIG. 3 is a diagram for explaining an example of a setting state of sub blinds in FIG. 2 in the case of a non-uniform pattern distribution.

FIG. 4 is a diagram showing a schematic configuration of a projection exposure apparatus according to a second embodiment.

5 is a plan view showing the arrangement of heaters on the reticle stage of FIG. 4. FIG.

FIG. 6 is a diagram for explaining the temperature control principle of the reticle according to the second embodiment.

FIG. 7 is a schematic perspective view showing the configuration of the main part of the third embodiment.

FIG. 8 is a plan view of the vicinity of a pellicle with the tips of an intake nozzle and an exhaust nozzle inserted into the pellicle.

FIG. 9 is a block diagram showing a schematic configuration of temperature adjusting means according to a third embodiment.

[Explanation of symbols]

10 Projection Exposure Device (Exposure Device) 14 Main Light Source (Light Source for Exposure) 16 Sub Light Source (Light Source for Emitting Light of Second Wavelength Characteristic, Part of Expansion / Contraction Adjustment Means) 18 Magnification Adjustment Mechanism (One of Magnification Adjustment System) 52) Main blind (a part of irradiation area setting means) 54 Irradiation area setting means 60 Sub blind (a part of second irradiation area setting means)
Part of expansion and contraction adjusting means) 62 Sub blind drive part (part of second irradiation region setting means, part of expansion and contraction adjusting means) 64 Magnification correction controller (part of magnification adjustment system) 66 Infrared irradiation controller (second) Part of the irradiation area setting means, part of the expansion and contraction adjusting means) 70 Projection exposure apparatus (exposure device) 72 Reticle temperature control controller (temperature control system, part of expansion and contraction adjusting means) 74a to 74h Heater (of expansion and contraction adjusting means) Part: 80 Pellicle (mask protection member) 82 Temperature sensor 100 Temperature adjusting means IL Exposure light (light of first wavelength characteristic) IR Infrared (light of second wavelength characteristic) R Reticle (mask) PL projection lens (projection) Optical system) W wafer (substrate)

Claims (7)

[Claims] 1. An exposure apparatus for irradiating a mask with light having a first wavelength characteristic emitted from a light source for exposure to form an image of a pattern on the mask on a substrate coated with a photosensitive agent. An irradiation area setting means for setting an irradiation area on the mask which is irradiated with light having the first wavelength characteristic; and based on information about the set irradiation area and known pattern distribution information on the mask. And an expansion / contraction adjusting unit that adjusts the expansion / contraction of the mask by adjusting the physical quantity relating to the expansion / contraction of the mask so as to be substantially uniform over the entire mask when the light having the first wavelength characteristic is irradiated. An exposure apparatus having a magnification adjustment system that adjusts the magnification of the image of the pattern of the mask based on a physical quantity relating to expansion and contraction of the mask. 2. The expansion and contraction adjusting means includes a light source that emits light having a second wavelength characteristic that is not exposed to the photosensitizer, information about the set irradiation area, and known pattern distribution information on the mask. 2. The exposure apparatus according to claim 1, further comprising: a second irradiation area setting unit that sets an irradiation area on the mask that is irradiated with the light having the second wavelength characteristic based on the above. 3. The expansion / contraction adjusting means adjusts the temperature of the heater based on a heater arranged in the peripheral portion of the mask, and information on the set irradiation area and pattern distribution information on the mask. The exposure apparatus according to claim 1, further comprising: 4. The magnification adjusting system includes input means for inputting energy of light having the first wavelength characteristic, a magnification adjusting mechanism for changing a magnification of an image of the mask pattern, and the first input. 2. The exposure apparatus according to claim 1, further comprising: a control unit that controls the magnification adjusting mechanism based on the energy of light having the wavelength characteristic of 1 and a physical quantity related to expansion and contraction of the mask. 5. The image of the pattern of the mask is formed on the photosensitive substrate via a projection optical system, and the magnification adjusting system changes the imaging characteristic of the projection optical system due to energy absorption of the projection optical system. 2. The exposure apparatus according to claim 1, wherein the change of the exposure amount is adjusted. 6. An exposure apparatus for irradiating a mask, to which a mask protection member having a thin film and a frame member is attached, with exposure light to form an image of a pattern on the mask on a photosensitive substrate. A temperature sensor that detects the temperature of the space formed by the member and the mask or the mask protection member; and a temperature adjusting unit that adjusts the temperature of the space or the mask protection member based on the output of the temperature sensor. An exposure apparatus having. 7. An exposure method for irradiating a mask with exposure light to form an image of a pattern on the mask on a photosensitive substrate, wherein a physical quantity relating to expansion and contraction of the mask is at least within an exposure light irradiation area on the mask. In the exposure method, the image of the pattern is formed on the photosensitive substrate in a state where the expansion and contraction of the mask are adjusted so as to be substantially uniform.