JPH07283114A - Aligner - Google Patents

Abstract

PURPOSE:To compensate for environmental variation, expansion of a wafer and deviation of a focal position and to realize highly accurate superposition exposure. CONSTITUTION:This device has a laser 1 whose oscillation wavelength is variable, a wavelength control means 14 for controlling an oscillation wavelength of laser light, an illumination optical system 2 for lighting a mask by laser light, a projection optical system 6 having a lens which images a mask pattern of a mask on a wafer, a pressure control means 5 for controlling a pressure applied to a lens inside a projection optical system and an environmental variation detection means 4 for detecting an environmental variation amount which varies a pressure applied to a lens of a projection optical system. Therefore, a wavelength control means controls a wavelength of laser light and a pressure control means controls a pressure applied to a lens inside a projection optical system to correct an environmental variation amount, etc., detected by an environmental variation detection means.

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 more particularly to an exposure apparatus for transferring a pattern on a mask onto a wafer via a projection optical system.

[0002]

2. Description of the Related Art In recent years, semiconductors have become smaller and smaller,
In a 64M DRAM LSI, it is desired to define a design rule of 0.35 μm, and it is inevitable that further finer design rules will be required in the photolithography technology in the future.

The overlay accuracy is required to be as high as one fifth to one third of the design rule.

Generally, the resolving power R is represented by the relationship of (Equation 1) using the numerical aperture (NA) of the projection lens and the exposure wavelength λ. Similarly, the depth of focus (DOF) is also (Equation 2)
It is expressed as. Here, A ₁ and A ₂ are constants of proportionality.

[0005]

[Equation 1]

[0006]

[Equation 2]

Therefore, in order to improve the resolving power from (Equation 1), it is necessary to shorten the exposure wavelength and increase the numerical aperture of the projection lens. On the contrary, as can be seen from (Equation 2), It can be seen that the depth of focus becomes shorter.

For example, the depth of focus at the minimum line width is 1 μm.
Since the height of the wafer is about m, it is very important to detect and align the height position of the wafer during exposure with high accuracy.

A specific configuration for such alignment is as follows.
For example, it is described in JP-A-62-69617.

This conventional example discloses a configuration in which the projection lens is divided into a plurality of air chambers, and the pressure in the air chambers is controlled to control magnification variation and focus variation.

A description will be given below with reference to FIG. In FIG. 5, reference numeral 15 is an illumination optical system, 16 is a reticle, 17 is a projection optical system, 18 is a wafer, 19 is a stage on which the wafer 18 is mounted, 20 is an imaging characteristic adjusting device, 21 is a constant pressure control system, and H is H. An air chamber whose pressure is controlled for magnification adjustment, N is an air chamber whose pressure is controlled for focus adjustment, and G1 to G5 are typical lens elements.

Then, the reticle 16 is projected through the projection optical system 17 using the irradiation light emitted from the illumination optical system 15.
Image is projected and exposed on the wafer 18.

In this structure, in order to correct the fluctuation in magnification and the fluctuation in focus of the illumination optical system 15 caused by the fluctuation in atmospheric pressure, the air chamber H for magnification adjustment and the air chamber N for focus position adjustment in the projection lens are closed. Control the pressure,
The refractive index is changed.

That is, at this time, the respective air chambers H, N
, The pressure is applied within the predetermined range of P1 and P2 by the imaging characteristic adjusting device 20.

Further, the constant pressure control system 21 applies a constant pressure above or below the setting range of P1 and P2 to the air chambers A and B so that the stress applied to each lens element is always in one direction. Is being applied.

The point is that each lens element is
If it is configured to always receive pressure in a fixed direction, it is not necessary to strongly hold the lens in a direction different from the direction in which pressure acts, so there is little possibility of giving unnecessary distortion to the lens and exposure characteristics This is because it will be stabilized.

Next, it is necessary to detect whether or not such correction is accurately performed, and if it is out of the allowable value, it is necessary to correct the zero point or the like of the detector for detecting the height of the wafer. .

Such a structure is disclosed in, for example, Japanese Patent Laid-Open No. 63-63.
There is one disclosed in Japanese Patent Publication No. 58349.

In the same report, a structure is disclosed in which a focus position is detected by using a TTLFA system (focus detection mechanism for performing focus detection via a projection optical system) and a zero point of a wafer height detector is corrected. Has been done.

A description will be given below with reference to FIG. In FIG. 6, 25 is a light source, 26 is a relay lens, 27 is a pattern, 28 is a relay lens, 29 is a half mirror, 30 is a field lens, 31 is a field stop, 32 is a relay lens, 33 is a mirror, 34 is a reticle, Reference numeral 35 is a projection lens, 36 is a reflecting plate, 37 is a prism, and 38 is a linear array.

In such a structure, the illumination light emitted from the light source 25 illuminates the line-and-space pattern 27 via the relay lens 26, and the transmitted light is transmitted to the half mirror 29 via the lens 28. Incident on.

The illumination light reflected by the half mirror 29 passes through the field lens 30, the field stop 31, and the relay lens 32, enters the mirror 33, is reflected here, and enters the reticle 34.

Next, the illumination light transmitted through the reticle 34 is
The reflected light reaches the reflection plate 36 on the same plane as the wafer (not shown) through the projection lens 35, is reflected there, and conversely becomes return light that is incident on the mirror 33 through the projection lens 35 and the reticle 34.

The return light reflected here is split by a splitting prism 37 provided at a position conjugate with the pupil position of the projection lens 35, and the split return light is
A pupil division image is formed on a different portion of the linear array sensor 38.

At this time, as is well known, the respective divided light fluxes are displaced from each other in accordance with the front pinned state and the rear pinned state of the reflecting plate 36.

Therefore, for example, each image is Fourier-transformed, the phase information portion thereof is extracted, and the interval between the two divided images is measured using the transition theorem of Fourier transform to detect the in-focus state. Based on the detection result, the wafer position is adjusted so as to be the regular position.

[0027]

However, in the configuration of the conventional example as described above, attention is paid only to a case where the projection optical system itself causes a magnification change and a focus change due to environmental changes such as atmospheric pressure, and the pressure in the air chamber is reduced. Although it is controlled and corrected, just controlling the pressure does not provide a sufficient correction amount for correction when a large environmental change occurs.

No consideration is given to the expansion and contraction of the wafer itself that occurs during the manufacturing process. This is because the expansion and contraction of the wafer itself cannot be ignored in order to obtain high overlay accuracy, and it is necessary to control the magnification of the projection optical system according to the expansion and contraction amount of the wafer itself.

Further, although the positional shift amount is detected from the phase information, the relationship between the phase and the shift amount obtained at this time is not necessarily linear.

Therefore, in order to detect the zero point, additional correction means is required.

An object of the present invention is to solve the above problems and to provide an exposure apparatus capable of effectively correcting magnification variation and focus variation.

It is another object of the present invention to provide an exposure apparatus capable of correcting the magnification of the projection optical system to an arbitrary imaging magnification according to the amount of expansion and contraction of the wafer itself.

It is another object of the present invention to provide an exposure apparatus capable of detecting whether or not the correction is accurately performed, and correcting the correction result when it is not within the allowable value.

[0034]

SUMMARY OF THE INVENTION The present invention is an exposure apparatus for exposing a mask pattern of a mask onto a wafer, wherein the laser is an illumination light source that emits laser light with a variable oscillation wavelength, and the laser light Wavelength control means for controlling an oscillation wavelength to a desired wavelength, an illumination optical system for illuminating the mask with the laser light, a projection optical system having a lens for forming a mask pattern of the mask on the wafer, It has a pressure control means for controlling the pressure applied to the lens in the projection optical system to a desired pressure, and an environmental change detection means for detecting an environmental change amount for varying the pressure applied to the lens of the projection optical system. However, the wavelength control means adjusts the fluctuation amount of the pressure applied to the lens of the projection optical system corresponding to the environmental change amount detected by the environmental change detection means. The wavelength of the laser light is controlled to a desired wavelength,
In the exposure apparatus, the pressure control unit controls the pressure applied to the lens in the projection optical system to a desired pressure.

In addition to or independently of the above, an expansion / contraction amount measuring means for measuring the expansion / contraction amount of the entire wafer or the chips in the wafer is provided, and the expansion / contraction amount measured by the expansion / contraction amount measuring means is corrected. The wavelength control means may control the wavelength of the laser light to a desired wavelength, and the pressure control means may control the pressure applied to the lens in the projection optical system to a desired pressure.

In addition to or independently of the above, it has a focus state detecting means for detecting the focus state of the projection optical system, and corresponds to the focus state of the projection optical system detected by the focus state detecting means. Then, the wavelength control means may control the wavelength of the laser light to a desired wavelength, and the pressure control means may control the pressure applied to the lens in the projection optical system to a desired pressure.

In addition, a wafer position detector may be provided, and the in-focus position obtained from the in-focus state detecting means may be set as the zero point of the wafer position detector.

In addition, a wafer position detector is provided, and the position of the focus position detection mark obtained from the focus state detecting means in the optical axis direction of the projection optical system and the wafer position of the wafer position detector are used. , The gain of the wafer position detector may be corrected.

[0039]

According to the present invention, with the above structure, the wavelength of the laser as the light source and the pressure in the projection lens are controlled, and the environmental fluctuation amount,
The amount of expansion and contraction of the wafer and the actual focus position are detected, and correction is performed so as to compensate for them.

Furthermore, the zero point of the height detector is corrected with the actual focus position as the normal focus position, and the gain is also corrected so that the normal focus position and the zero point of the height detector match.

[0041]

Embodiments of the present invention will be described in detail below with reference to FIG.

FIG. 1 is a block diagram of the exposure apparatus of the present invention. In FIG. 1, reference numeral 1 denotes a tunable laser which is a light source,
Reference numeral 2 is an illumination optical system, 3 is a mask, 4 is a pressure detector for detecting pressure inside and outside the projection lens, and 5 is pressure control for controlling the pressure inside the projection lens to provide an arbitrary pressure difference with respect to the atmospheric pressure. Apparatus, 6 is a projection lens, 7 is a height detector for detecting the height of the wafer, 8 is a focus position detector for detecting the focus position of the projection lens, 9 is a position alignment detector, and 10 is control The light source 1 is controlled by controlling the device 5 and the detectors 7 and 8 according to environmental changes
Of the laser wavelength and the pressure in the projection lens, 11 is a wafer, 12 is a wafer stage on which the wafer is mounted, 13 is a mask illumination system that illuminates the mask 3, and 14 is a wavelength control device that controls the laser wavelength. Is.

The operation of the above arrangement will be described below with reference to the flow chart of FIG.

First, the projection lens 6 is operated by the pressure detector 4.
Detect the pressure inside and outside the to confirm the amount of environmental change from the standard state. In this embodiment, the environmental fluctuation amount is represented as the pressure fluctuation amount, but other fluctuation amounts may be used as long as they affect the magnification and the like of the projection optical system.

Next, in order to correct the magnification fluctuation and focus fluctuation caused by this environmental change, based on the output result of the pressure detector 4, the calculator 10 calculates the wavelength correction amount and the projection of the laser 1 from the reference state. The pressure correction amount of the entire lens 6 is calculated.

The calculation procedure in this case will be described below. Assuming that the amount of change in atmospheric pressure from the reference atmospheric pressure is Δpre, the change in image formation magnification ΔM ₁ that occurs in the amount of change in atmospheric pressure projection lens 6
The focus variation ΔF ₁ is generally represented by the following (Equation 3) and (Equation 4).

[0047]

[Equation 3]

[0048]

[Equation 4]

However, k ₁ and k ₂ are constants.

On the other hand, assuming that the wavelength difference of the laser 1 from the reference state is Δλ ₁ and the pressure difference between the inside and outside of the projection lens 6 is ΔP ₁ , Δλ ₁ and ΔP ₁ are different from the variations ΔM ₂ and ΔF _{2 in} this case. Since they act independently, they are expressed by (Equation 5) and (Equation 6).

The pressure provided in the projection lens 6 is assumed to be applied to the entire projection lens.

[0052]

[Equation 5]

[0053]

[Equation 6]

However, k _{3 to} k ₆ are constants.

The above k ₁ to k ₆ are values peculiar to the projection lens, and may be theoretical values calculated when designing the projection lens, or experimental values actually calculated by experiment may be used. .

Here, the amount of change from the reference atmospheric pressure is Δpre
In this case, considering that the laser wavelength and the pressure in the projection lens are changed from the reference value in order to correct the image-forming magnification change amount and the focus change amount, respectively, the following (Equation 7), (Equation 8) ) Sum of ΔM ₁ and ΔM ₂ ΔM, Δ
It is sufficient to change the wavelength and the pressure so that the sum ΔF of F ₁ and ΔF ₂ becomes zero. These changes are
Let Δλ ₂ and ΔP ₂ respectively.

[0057]

[Equation 7]

[0058]

[Equation 8]

Therefore, ΔM and ΔF in (Equation 7) and (Equation 8)
Solving for Δpre by setting each to zero, Δλ ₂ , Δ
P ₂ is given by the following (Equation 9) and (Equation 10).

[0060]

[Equation 9]

[0061]

[Equation 10] Therefore, depending on the environmental change from the reference state, ΔP ₂ , Δλ ₂
Is calculated by (Equation 9) and (Equation 10), and if the wavelength control device 14 and the pressure control device 5 are instructed to change the respective amounts ΔP ₂ and Δλ ₂ , the It is possible to correct the magnification variation and focus variation that occur.

For example, in this embodiment, the atmospheric pressure is 95
Control pressure correction amount ΔP for making magnification change and focus change zero at 3 mbar and 1043 mbar
₂ and the laser wavelength correction amount Δλ ₂ can be obtained as shown in (Table 1) below.

[0063]

[Table 1]

As described above, in the present embodiment, by controlling both the pressure and the wavelength, it is possible to surely correct environmental fluctuations, particularly magnification fluctuations and focus fluctuations due to pressure fluctuations.

Next, in this embodiment, in addition to the above correction,
It is also possible to measure the amount of expansion and contraction of the wafer 11 placed on the stage 12 and correct it.

For that purpose, first, the alignment detector 9
Is used to detect a plurality of alignment marks (not shown) provided in the wafer 11.

These alignment marks correspond to the wafer 11
When a plurality of chips for detecting the X direction and a plurality of chips for detecting the Y direction are arranged in one chip, the plurality of alignment marks for the chips of the wafer 11 to be exposed in the X and Y directions, respectively. If the amount of positional deviation is detected, the amount of expansion and contraction of each chip and the amount of expansion and contraction of the wafer 11 become clear.

In this case, it is not necessary to measure the expansion / contraction variation amount for all the chips of the wafer to be exposed 11, and it may be performed only for any extracted chip.

If only one set is measured in the X and Y directions within one chip, it is necessary to measure a plurality of them in the wafer 11
The total amount of expansion / contraction becomes clear.

The expansion / contraction amount of each chip may be calculated from the expansion / contraction amount of the entire wafer 11.

Since the expansion / contraction amount thus obtained corresponds to the magnification variation amount Δm, the wavelength and pressure correction amounts corresponding to this magnification variation amount Δm will be determined respectively.

The calculation procedure in this case will be described below. First, when Δpre is set to zero in (Equation 7) and (Equation 8) and ΔM is solved, Δλ ₃ and ΔP ₃ are obtained by (Equation 1)
1) and (Equation 12). For convenience, ΔM is set to Δ
It was written as m.

[0073]

[Equation 11]

[0074]

[Equation 12]

On the other hand, since the wavelength is corrected by Δλ ₂ and the pressure of the projection lens is corrected by ΔP ₂ in order to correct the magnification variation amount and the focus variation amount from the reference state caused by the above environmental change, finally, The correction amounts of the wavelength Δλ and the pressure ΔP to be corrected are the sum of them and the expansion / contraction amount of the wafer 11, that is, each of the wavelength correction amount Δλ ₃ and the pressure correction amount ΔP ₃ corresponding to the magnification variation amount, and 13) and (Equation 14).

[0076]

[Equation 13]

[0077]

[Equation 14]

Based on the values thus obtained by the arithmetic unit 10, the arithmetic unit 10 has the wavelength controller 14 and the pressure controller 5.
It becomes possible to obtain a desired magnification extremely accurately by sending a command to.

That is, if the above correction is performed, the magnification can be set corresponding to each of the exposed chips or their desired ones, or the actual size of the entire wafer 11,
High overlay accuracy can be obtained.

If the environmental change is so small that it can be ignored, it is possible to make a correction by paying attention only to the expansion / contraction amount of the wafer 11.

Now, in consideration of environmental fluctuation and / or expansion / contraction of the wafer, the wavelength control device and the pressure control device are
After setting the respective desired values, the focus position of the projection optical system is detected by the focus detector to examine whether or not these corrections are accurately performed.

This is because if the correction is accurately performed,
Since the in-focus position should always be kept at the same position, if the actually detected in-focus position deviates from the normal position, it is considered that the correction has not been performed accurately. Based on that.

If the detected deviation amount, that is, the focusing position shift amount is not zero or exceeds the allowable value, it is necessary to recorrect.

For that purpose, first, the actual focus position is obtained by the focus position detector 8. Here, a part of the laser light emitted from the laser 1 is extracted using an optical fiber or the like (not shown), the pattern on the mask 3 is illuminated by the mask illumination system 13, and the reflected light is focused on the focus position detector. 8
An image is formed on an inside TV camera, for example, an ultraviolet camera when the laser light is ultraviolet light.

This pattern is suitable if it is a linear diffraction grating with an equal pitch, but other patterns may be used as long as it suits the purpose.

On the other hand, the illumination light that illuminates the pattern on the mask 3 forms an image on the wafer 11 at the conjugate position via the projection lens 6, is reflected there, returns through the projection lens 6 and returns to the mask 3. It is re-imaged and the image is imaged on a TV camera.

Then, the contrast of those images is detected. Next, the wafer stage 12 is moved in the height direction, the relative position between the pattern on the mask 3 and the wafer 11 is changed, and the contrast is detected each time. The focal position will be calculated.

FIG. 3 shows the results when the horizontal axis represents the height position of the wafer stage 12 and the vertical axis represents the contrast.

Then, this result is interpolated by a quadratic function,
The height of the wafer stage 12 when the contrast is maximized is obtained, and the height position of the wafer 11 is set as the actual normal focus position of the projection lens 6.

If the normal focus position does not match the position of the wafer 11 after being corrected as described above or exceeds the allowable value, it can be determined that further correction is necessary. .

The procedure for calculating the wavelength and the pressure in this case will be described below. If the amount of in-focus position deviation from the normal position obtained by the in-focus position detector 8 is ΔF ′, the re-correction amount can be calculated by the arithmetic unit 10 by using (Equation 7) and (Equation 8). You can ask.

That is, Δp in (Equation 7) and (Equation 8)
When re is zero and ΔF is solved, Δλ ', ΔP'
Is as in (Equation 15) and (Equation 16). For the sake of convenience, ΔF is referred to as ΔF ′.

[0093]

[Equation 15]

[0094]

[Equation 16]

Therefore, the actually necessary correction amount is (Equation 1
3), Δλ and ΔP shown in (Equation 14) are respectively Δ
It is the sum of λ'and ΔP '.

Since such a correction is carried out by transmitting light through a mask, that is, a reticle, TTR (through the.
Reticle) method.

If there is substantially no environmental change or expansion / contraction of the wafer, only the focus position may be corrected.

At this time, since the focus position detector 8 substantially detects the height position of the wafer 11, the measurement result of the focus position detector 8 at each wafer height position, and The zero point and the gain of the height detector 7 can be corrected by comparing the measurement result of the height detector 7.

FIG. 4 shows the contrast measured by the focus position detector 8 and the measurement result of the height detector 7 when the stage height is changed in the height direction.

Originally, the focus position where the contrast of the focus position detector 8 is maximum and the zero point of the height detector 7 must match, but the zero point of the height detector 7 drifted or the gain changed. In this case, these do not match as shown in FIG. 4, so correction is necessary.

Specifically, this is the amount of deviation between the in-focus position detected by the in-focus position detector 8 and the zero point detected by the height detector 7, and, if necessary, the unit of the height detector 7. The output change amount with respect to the height variation is calculated by the calculator 10, and these values are corrected so as to always correspond to the focus position detected by the focus position detector 8.

As described above, if the zero point and the gain of the height detector 7 are corrected, more accurate control in the height direction is possible.

[0103]

As described above, according to the present invention, by using the two control means for correcting the laser wavelength and correcting the pressure of the projection lens, it is possible to perform highly accurate overlay exposure which is not easily affected by environmental changes.

Furthermore, since the magnification of the projection lens is also corrected according to the amount of expansion and contraction of the wafer, higher overlay accuracy can be obtained.

Further, the contrast of the image on the wafer is detected by the TTR method, the value of the contrast is interpolated by a parabola, and the in-focus position is accurately detected and corrected, so that higher overlay accuracy can be obtained. You can

At this time, the focus position of the projection lens can be always maintained at the same position, and the overlay accuracy is further improved.

Further, since the zero point and the gain of the wafer height detector can be corrected, the wafer height can be accurately detected.

[Brief description of drawings]

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

FIG. 2 is a diagram showing an overall flow chart for the same magnification correction.

FIG. 3 is a diagram showing a parabolic approximation for detecting the in-focus position.

FIG. 4 is a diagram showing an output of the in-focus position detector and an output of a height position detector.

FIG. 5 is a block diagram of a conventional exposure apparatus

FIG. 6 is a configuration diagram of a conventional exposure apparatus.

[Explanation of symbols]

 1 Laser 2 Illumination Optical System 3 Mask 4 Pressure Detector 5 Pressure Control Device 6 Projection Lens 7 Height Detector 8 Focusing Position Detector 9 Alignment Detector 10 Calculator 11 Wafer 12 Wafer Stage 13 Mask for Illuminating Mask 3 Illumination system 14 Wavelength control device 15 Illumination optical system 16 Reticle 17 Projection optical system 18 Wafer 19 Stage 20 Imaging property adjusting device 21 Constant pressure control system 25 Light source 26 Relay lens 27 Pattern 28 Relay lens 29 Half mirror 30 Field lens 31 Field stop 32 Relay lens 33 Mirror 34 Reticle 35 Projection lens 36 Reflector 37 Prism 38 Linear array

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 21/30 516 C (72) Inventor Satoru Kimura 1006 Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. In the company

Claims (15)

[Claims] 1. An exposure apparatus for exposing a mask pattern of a mask onto a wafer, wherein a laser is an illumination light source that emits laser light having a variable oscillation wavelength, and the oscillation wavelength of the laser light is controlled to a desired wavelength. Wavelength control means, an illumination optical system for illuminating the mask with the laser light, a projection optical system having a lens for forming a mask pattern of the mask on the wafer, and a lens in the projection optical system. Pressure control means for controlling the pressure applied to a desired pressure,
A lens of the projection optical system corresponding to the environmental change amount detected by the environmental change detection unit, the environmental change detecting unit detecting an environmental change amount that changes the pressure applied to the lens of the projection optical system. The wavelength control means controls the wavelength of the laser light to a desired wavelength so as to correct the fluctuation amount of the pressure applied to the lens, and the pressure control means controls the pressure applied to the lens in the projection optical system. An exposure device that controls to a desired pressure. 2. The wavelength control means is further provided with an expansion / contraction amount measuring means for measuring the expansion / contraction amount of the entire wafer or the chips in the wafer, and correcting the expansion / contraction amount measured by the expansion / contraction amount measuring means. 2. The exposure apparatus according to claim 1, wherein the pressure control means controls the wavelength of the laser light to a desired wavelength, and the pressure control means controls the pressure applied to the lens in the projection optical system to a desired pressure. 3. Further, a focusing state detecting means for detecting a focusing state of the projection optical system is provided, and a wavelength corresponding to a focusing state of the projection optical system detected by the focusing state detecting means. 3. The exposure apparatus according to claim 1, wherein the control means controls the wavelength of the laser light to a desired wavelength, and the pressure control means controls the pressure applied to the lens in the projection optical system to a desired pressure. 4. An exposure apparatus for exposing a mask pattern of a mask onto a wafer, wherein a laser is an illumination light source that emits laser light whose oscillation wavelength is variable, and the wavelength of the laser light is controlled to a desired wavelength. A wavelength control unit, an illumination optical system that illuminates the mask with the laser light, a projection optical system having a lens that forms a mask pattern of the mask on the wafer, and a lens in the projection optical system. Pressure control means for controlling the pressure to a desired pressure, and an expansion / contraction amount measuring means for measuring the expansion / contraction amount of the entire wafer or chips in the wafer, and the expansion / contraction amount measured by the expansion / contraction amount measuring means. The wavelength control means controls the wavelength of the laser light to a desired wavelength and the pressure control means controls the pressure applied to the lens in the projection optical system to a desired pressure so as to correct. Exposure equipment. 5. An exposure apparatus for exposing a mask pattern of a mask onto a wafer, wherein a laser is an illumination light source that emits laser light whose oscillation wavelength is variable, and the wavelength of the laser light is controlled to a desired wavelength. A wavelength control unit, an illumination optical system that illuminates the mask with the laser light, a projection optical system having a lens that forms a mask pattern of the mask on the wafer, and a lens in the projection optical system. Pressure control means for controlling a desired pressure to a desired pressure, and a focus state detection means for detecting a focus state of the projection optical system, and a combination of the projection optical system detected by the focus state detection means. Exposure in which the wavelength control unit controls the wavelength of the laser light to a desired wavelength and the pressure control unit controls the pressure applied to the lens in the projection optical system to a desired pressure according to the focus state. apparatus. 6. The expansion / contraction amount is regarded as the magnification variation amount of the projection optical system, the wavelength control unit controls the wavelength of the laser beam to a desired wavelength so that the magnification variation amount is corrected, and the pressure control unit controls the projection optical system. The exposure apparatus according to claim 2, wherein the pressure applied to the lens in the system is controlled to a desired pressure. 7. The wavelength control means controls the wavelength of the laser light to a desired wavelength so that the variation in the focused state is regarded as the variation in the focal length of the projection optical system, and the variation in the focal length is corrected. The exposure apparatus according to claim 3, wherein the pressure control means controls the pressure applied to the lens in the projection optical system to a desired pressure. 8. The focus state detection means has a TV camera observation system, irradiates a focus position detection mark using laser light to generate irradiation light, and the irradiation light is generated at a mask position and a wafer position. The image is reflected by forming respective images corresponding to the mask position or the wafer position of the in-focus position detection mark in the TV camera observation system, and observing the contrast of the formed image to achieve a focused state. The exposure apparatus according to claim 3, 5 or 7, which detects a. 9. The in-focus state detection means sets a position where the contrast of an image of the in-focus position detection mark obtained by changing the relative position between the in-focus position detection mark and the wafer is maximum as the in-focus position. Item 9. The exposure apparatus according to item 8. 10. The focus state detecting means uses coordinates indicating the relationship between the position of the wafer in the optical axis direction between the projection optical system and the wafer and the contrast of the image obtained each time, and the coordinates are calculated by parabolic approximation. 10. The exposure apparatus according to claim 9, wherein the maximum value of the parabola is set as the in-focus position. 11. The exposure apparatus according to claim 10, wherein the focus position detection marks are linear diffraction gratings with equal intervals. 12. The exposure apparatus according to claim 9, further comprising a wafer position detector, and the focus position obtained from the focus state detecting means is set as a zero point of the wafer position detector. . 13. A wafer position detector is further provided, and the position of the focus position detection mark obtained from the focus state detection means in the optical axis direction of the projection optical system and the wafer position of the wafer position detector are used. 12. The exposure apparatus according to claim 9, wherein the gain of the wafer position detector is corrected. 14. The exposure apparatus according to claim 1, wherein the magnification and the focal length of the projection optical system are kept substantially constant. 15. The exposure apparatus according to claim 2, wherein a plurality of alignment marks formed on the wafer are provided in one chip.