JP2004101335A - Method and apparatus for measuring interference, optical element, optical system, and projection aligner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an interference measuring method, an interference measuring apparatus, an optical element, an optical system, and a projection aligner which enables measurement without errors, by solving the following problem, wherein measurement results have errors due to the infiltration of oxygen into an interference optical system, the strains in the interference optical system, and the fluctuations in the interference optical system caused by the strains of the containers of an interference-measuring apparatus. <P>SOLUTION: This interference-measuring method performs interference measurement of an optical element or optical system to be measured by using an interference-measuring apparatus composed of a first container 15, a second container 1, which is housed in the first container and has inside it an interference optical system for performing interference measurement of the optical system or optical element, a light source 2, and a detector 8. The method has a first supply process for supplying a first gas which is different from the atmosphere into the first container, a second supply process for supplying a second gas different form the atmosphere into the second container, and an interference-measuring process for performing the interference measurement of the optical element or optical system. The interference-measuring process is carried out, after the finishing of the second supply process. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an interference measurement method, an interference measurement device, an optical element, an optical system, and a projection exposure device.
[0002]
[Prior art]
The projection exposure apparatus is an apparatus that accurately projects and exposes a fine circuit pattern drawn on a mask onto a wafer surface. In particular, recently, an apparatus using light having a wavelength of 200 nm or less called vacuum ultraviolet light as a light source has been developed, and the processing accuracy of a circuit pattern manufactured by a projection exposure apparatus has been increasingly higher.
[0003]
It is necessary to use optical elements and optical systems incorporated in these projection exposure apparatuses after measuring optical characteristics with high precision. This is because the accuracy of the measurement of the optical characteristics greatly affects the accuracy of the semiconductor to be processed.
[0004]
As an apparatus for measuring optical characteristics of an optical element or an optical system used in a projection exposure apparatus with high accuracy, an interference measuring apparatus is exemplified. 2. Description of the Related Art An interference measurement apparatus is an apparatus that measures optical characteristics of an optical element or an optical system by using light interference. Specifically, the reference light having a uniform wavefront shape is superimposed on the measurement light passing through the optical element or the optical system, and the optical characteristics of the optical element or the optical system are changed by interference fringes resulting from the phase shift. Measure.
[0005]
Since the optical characteristics of these optical elements and optical systems have wavelength dependence, even if the optical characteristics are measured at a wavelength different from the used wavelength, an error will occur from the optical characteristics at the used wavelength. Therefore, the optical characteristics of the optical element and the optical system are measured using the wavelength to be used. Therefore, when measuring the optical characteristics of an optical element or an optical system used in a projection exposure apparatus using vacuum ultraviolet light as a light source, it is necessary to use vacuum ultraviolet light.
[0006]
However, the energy of vacuum ultraviolet light is attenuated by the absorption of energy by oxygen. In the interference measurement device, it is difficult to perform accurate measurement because the interference effect is weakened particularly when the reference light and the measurement light are attenuated, and therefore, at least in the interference measurement device using vacuum ultraviolet light as a light source, It is necessary to avoid disposing the interference optical system relating to the reference light and the measurement light in the atmosphere.
[0007]
Therefore, it is necessary to use a gas which does not easily absorb the vacuum ultraviolet light for the atmosphere of the interference optical system using the vacuum ultraviolet light as a light source. Examples of such a gas include a nitrogen gas and a helium gas. Specifically, after placing the interference optical system in a sealable container, exhausting the atmosphere inside the container, and then replacing the atmosphere of the interference optical system with nitrogen from the atmosphere by introducing nitrogen gas or the like into the container, The optical characteristics are measured.
[0008]
FIG. 4 is a conceptual diagram of a conventional interference measurement device. In FIG. 4, 51 is a container, 52 is a transparent optical window, 50 and 56 are half mirrors, and 53, 54 and 55 are folding mirrors. In FIG. 4, the portion accommodated in the container 51 is the interference optical system, and the atmosphere of the optical path included in this portion needs to be replaced from the atmosphere with nitrogen gas or the like.
[0009]
The measuring method using the apparatus shown in FIG. 4 will be described below. The container 51 in which the interference optical system is set is tightened with the lid 57 with the bolt 58 via the hermetic seal 59 so that the container 51 is sealed. The atmosphere inside the container 51 is exhausted by an exhaust device (not shown). Next, nitrogen gas is introduced into the evacuated container 51. In this way, the optical characteristics of the optical system to be measured are measured with the atmosphere inside the container 51 being set to the nitrogen gas. The specific measurement is performed as follows.
[0010]
The light emitted from the light source 2 passes through the transparent optical window 52 and is split by the half mirror 50 into two light beams. The light beam passing through the half mirror 50 is the measurement light, and the light beam reflected by the half mirror 50 is the reference light. The light beam of the measurement light passes through the transparent optical window 52 and reaches the optical system to be measured via the condenser lens 20. The light beam transmitted through the measured optical system is reflected by the reflection mirror 21, passes through the measured optical system and the condenser lens 20, passes through the transparent optical window 52, and returns to the container 51. The light flux returned to the container 51 is partially reflected by the half mirror 50 in the direction of the bending mirror 55, and after being reflected by the bending mirror 55, enters the half mirror 56.
[0011]
On the other hand, the light beam of the reference light enters the half mirror 56 after passing through the bending mirrors 53 and 54. In the half mirror 56, the reference light is partially reflected by the half mirror 56 and travels toward the detection unit 8, and the measurement light partially passes through the half mirror 56 and travels toward the detection unit 8. The light in which the reference light and the measurement light overlap each other passes through the transparent optical window 52 and reaches the detection unit 8, so that the detector 8 can observe interference fringes corresponding to the phase difference between the two.
[0012]
Since the state of the interference fringes corresponds to the disturbance of the wavefront caused by the measured optical system, the optical characteristics of the measured optical system can be measured.
A configuration as shown in the conceptual diagram of FIG. 5 has also been proposed. In FIG. 5, an opening is provided in the container 61, and a gas supply unit 63 for supplying nitrogen gas is provided. The same measurement optical system as that shown in FIG. 4 is used.
[0013]
The operation of the device shown in FIG. 5 will be described below. The opening of the container 61 in which the interference optical system is set is closed with a lid. At this time, the lid and the container are not fastened with bolts or the like so as not to seal the container 61. Therefore, a gap exists between the lid and the opening in the container 61. Next, nitrogen gas is introduced into the container 61 from the gas supply unit 63 at a pressure higher than the atmospheric pressure. The atmosphere inside the container 61 is discharged outside through a gap between the lid and the opening by the introduced nitrogen gas, and the inside of the container 61 is replaced with nitrogen gas. Even after the inside of the container 61 is replaced with the nitrogen gas, the supply of the nitrogen gas is continued to prevent the intrusion of the atmosphere from the gap between the opening and the lid. Thus, the optical characteristics of the optical system to be measured are measured in a state where the atmosphere inside the container 61 is set to the nitrogen gas. The measuring method is the same as that of the apparatus shown in FIG.
[0014]
[Problems to be solved by the invention]
However, in the case of the configuration shown in FIG. 4, the container 58 is distorted because the bolt 58 is tightened and pressure is applied to the airtight seal 59 via the lid 57. When distortion occurs in the container 51, distortion also occurs in the interference optical system housed inside the container 51, and there is a problem that an error occurs in the measurement result of the optical characteristics of the optical system to be measured.
[0015]
Further, in the apparatus shown in FIG. 5, even during the measurement, the nitrogen gas in the container 61 flows due to the supply of the nitrogen gas, so that the optical path of the interference optical system fluctuates. Fluctuations generated in the interference optical system disturb the phases of the reference light and the measurement light, and thus have a problem that errors occur in the measurement results of the measured optical system. If the supply of gas is stopped during the measurement to suppress the generation of fluctuation, in this case, there is a problem that oxygen enters the container 51, thereby causing an error in the measurement result.
[0016]
The present invention solves the above problems and provides an interference measurement device that does not generate an error by preventing distortion of the interference optical system, fluctuation in the interference optical system, and mixing of oxygen into the interference optical system. The purpose is to do.
[0017]
[Means for Solving the Problems]
A first invention provides a first container, and a second container housed in the first container, in which an interference optical system for measuring interference of the measured optical system or the measured optical element is disposed. And a light source, and a detector, using an interference measurement device including: an interference measurement method for performing interference measurement of the optical element to be measured or the optical system to be measured; A first supply step of supplying one gas, a second supply step of supplying a second gas different from the atmosphere into the second container, and interference measurement of the measured optical element or the measured optical system. And performing the interference measurement step after the end of the second supply step.
[0018]
With such a configuration, it is possible to provide an interference measurement method in which an error hardly occurs.
A second invention is characterized in that, in the interference measurement method according to the first aspect, the first supply step is performed during the interference measurement step.
[0019]
With such a configuration, the intrusion of oxygen into the interference optical system can be reliably prevented, so that it is possible to provide an interference measurement method with less error.
According to a third aspect of the present invention, in the interference measurement method according to the first aspect, the first gas and the second gas are any one of nitrogen, helium, and argon, respectively. .
[0020]
With such a configuration, since the light is not attenuated in the interference optical system, it is possible to provide an interference measurement method with less error.
A fourth aspect of the present invention is the interference measurement method according to the third aspect, wherein the first gas is of the same type as the second gas.
[0021]
With such a configuration, since an airflow is not disturbed due to mixing of gases, an interference measurement method that does not cause an error can be provided.
A fifth aspect of the present invention is the interference measurement method according to the first aspect, wherein the wavelength of the light from the light source is 200 nm or less.
[0022]
With such a configuration, it is possible to provide an interference measurement method in which an error does not occur in the interference measurement of the optical element and the optical system corresponding to light having a wavelength of 200 nm or less.
[0023]
According to a sixth aspect, in the interference measurement method according to claim 1, the second supply step is a step of supplying a gas inside the first container to the inside of the second container. It is characterized by.
[0024]
With such a configuration, since the light is not attenuated in the interference optical system, it is possible to provide an interference measurement method with less error.
A seventh invention is an interference measurement apparatus that performs interference measurement of an optical system to be measured or an optical element to be measured, wherein the first container and the optical system to be measured are housed in the first container. A second container in which an interference optical system for performing interference measurement of the measured optical element is arranged, a light source, a detector, and a first gas supply unit that supplies gas to the inside of the first container. Wherein the first container has an opening communicating with the outside of the first container, and the second container has an opening communicating with the first container.
[0025]
With such a configuration, it is possible to provide an interference measurement device in which an error hardly occurs.
According to an eighth aspect of the present invention, in the interferometer according to the seventh aspect, a second gas supply unit that supplies the gas into the second container is provided.
[0026]
With such a configuration, the gas in the second container can be surely replaced, so that it is possible to provide an interference measurement device with less error.
According to a ninth aspect, in the interferometer according to the seventh aspect, the wavelength of the light emitted from the light source is 200 nm or less.
[0027]
With such a configuration, it is possible to provide an interference measurement device that does not cause an error in interference measurement of an optical element and an optical system corresponding to light having a wavelength of 200 nm or less.
[0028]
A tenth invention is characterized in that the optical characteristics of the optical element are measured by the method according to any one of the first to sixth aspects.
With such a configuration, it is possible to provide an optical element with good measurement accuracy of optical characteristics.
[0029]
An eleventh invention is characterized in that the optical characteristics of the optical system are measured by any one of the first to sixth methods.
With such a configuration, it is possible to provide an optical system with good measurement accuracy of optical characteristics.
According to a twelfth aspect, an optical system according to the eleventh aspect is used in a projection exposure apparatus.
[0030]
According to the present invention, it is possible to provide a projection exposure apparatus having good optical characteristic accuracy.
[0031]
BEST MODE FOR CARRYING OUT THE INVENTION
[0032]
Embodiment 1
FIG. 1 is a conceptual diagram showing a first embodiment of the present invention. An embodiment of the present invention will be described below with reference to FIG.
[0033]
In FIG. 1, reference numeral 2 denotes a vacuum ultraviolet light source that generates light having a wavelength of 200 nm or less, 3 and 7 denote half mirrors, 4, 5 and 6 denote mirrors, 20 denotes a condenser lens, 21 denotes a reflection mirror, and 12 denotes a transparent mirror. The optical window 8 is a detector that can detect a two-dimensional image of vacuum ultraviolet light. Reference numeral 1 denotes a container housing a part of the measurement optical system, and 15 denotes another container housing the container 1. Reference numerals 97 and 98 denote gas supply units for supplying nitrogen gas to the container 1 and the container 15, respectively, and reference numerals 81, 82, 83 and 84 denote valves. The container 1 and the container 15 are provided with openings. Here, the opening includes a portion between the container 1 and the container 15 and their respective lids.
[0034]
Next, a method for measuring the optical characteristics of the optical system using the interference measurement device shown in FIG. 1 will be described. First, after adjusting each optical element of the measurement optical system, the openings of the container 1 and the container 15 are covered with respective lids. At this time, the lid and the container main body are not tightened with bolts or the like so as not to generate distortion in the container 1 and the container 15.
[0035]
Next, the valve 83 and the valve 84 are opened, and nitrogen gas is supplied to the container 1 and the container 15 from the gas supply unit 97 and the gas supply unit 98. At the same time, the valve 81 and the valve 82 are opened, and the atmosphere in the container 1 and the container 15 is discharged to the outside of the container through the valves 81 and 82, respectively. Next, after the gas inside the container 1 and the container 15 is sufficiently replaced with nitrogen gas, the valves 81 and 82 are closed. Next, the valve 83 is closed, and the gas supply to the container 1 is stopped.
[0036]
In this state, the interference fringes of the measured optical system are measured. During the measurement, the valve 84 is kept open, and the gas supply unit 98 supplies the gas to the container 15 at a pressure higher than the atmospheric pressure. Thereby, the nitrogen gas is released from the container 15 to the atmosphere through the gap existing in the container 15. Since the pressure inside the container 15 is higher than the atmospheric pressure, the atmosphere cannot enter the container 15 and the state without oxygen in the container 15 is maintained.
[0037]
Here, the measurement of interference fringes will be specifically described below. After the light emitted from the light source 2 passes through the transparent optical window 12, the light is split by the half mirror 3 into two light beams. The light beam partially reflected by the half mirror 3 is reference light, and the light beam partially transmitted by the half mirror 3 is measurement light. The light beam of the reference light enters the half mirror 7 after passing through the bending mirrors 4 and 5.
[0038]
On the other hand, the luminous flux of the measurement light passes through the transparent optical window 12, once passes through the container 15, and then enters the optical system to be measured via the condenser lens 20. The light beam that has passed through the measured optical system is reflected by the reflection mirror 21, passes through the measured optical system and the condenser lens 20, passes through the transparent optical window 12, and returns to the container 15. The light flux returned to the container 15 is partially reflected by the half mirror 3, reflected by the bending mirror 6, and then enters the half mirror 7.
[0039]
In the half mirror 7, the light obtained by superimposing the partially reflected reference light and the partially transmitted measurement light passes through the transparent optical window 12 and reaches the detection unit 8. The detector 8 observes interference fringes corresponding to the phase difference between the two. Since the phase difference corresponds to the disturbance of the wavefront due to the measured optical system, the optical characteristics of the measured optical system can be measured based on the state of the interference fringes.
[0040]
In such a configuration, as described above, fluctuation of the optical path in the optical attenuation / interference optical system due to mixing of oxygen does not occur. Further, since the container 1 is not deformed, no error occurs due to the distortion of the interference optical system.
[0041]
Therefore, in the present embodiment, by preventing distortion of the interference optical system, fluctuation in the interference optical system, and entry of oxygen into the interference optical system, it is possible to provide an interference measurement device in which no error occurs.
[0042]
It should be noted that a configuration in which the nitrogen gas supply unit 97 and the valve 84 are omitted from the configuration described above may be adopted. In such a case, when the inside of the container 15 is replaced with nitrogen gas, the internal gas between the container 15 and the container 1 is exchanged through the gap of the container 1. The inside of the container 1 is also replaced with nitrogen gas.
[0043]
Embodiment 2
FIG. 2 is a conceptual diagram showing a second embodiment of the present invention. Hereinafter, an embodiment of the invention will be described with reference to FIG.
[0044]
In FIG. 2, 13, 14 and 17 are half mirrors, and 19 and 16 are bending mirrors. 25 is a condenser lens, 26 is a pinhole, and 27 is a collimator lens. Other configurations are the same as in the first embodiment, and a description thereof will not be repeated.
[0045]
The present embodiment is configured to generate reference light from measurement light in order to prevent a decrease in contrast of interference fringes caused by a decrease in the amount of measurement light passing through the measured optical system.
[0046]
A method for measuring the optical characteristics of the optical system using the interference measurement device according to the present embodiment will be described. First, the process of adjusting the interference optical system through the openings of the container 1 and the container 15 and covering the openings is performed in the same manner as in Example 1, and the inside of the container 1 and the container 15 is replaced with nitrogen.
[0047]
Here, the measurement of interference fringes will be specifically described below. The light emitted from the light source 2 passes through the transparent optical window 12 and enters the half mirror 13. The light beam partially transmitted through the half mirror 13 reaches the optical system to be measured via the transparent optical window 12 and the condenser lens 20. The light beam transmitted through the optical system to be measured is reflected by the reflection mirror 21, passes through the optical system to be measured, the condenser lens 20, and the transparent optical window 12, returns to the container 15, and reaches the half mirror 13 again. The light beam partially reflected by the half mirror 13 is split by the half mirror 14 into two light beams.
[0048]
Of the split light beams, the light beam partially transmitted through the half mirror 14 is incident on the half mirror 17 via the bending mirror 16 and partially transmitted through the half mirror 17. This light beam is the measurement light.
[0049]
On the other hand, the light beam partially reflected by the half mirror 14 is condensed by the condensing lens 25 via the bending mirror 19 and enters the pinhole 26. The wavefront of the light emitted from the pinhole 26 becomes a substantially ideal spherical wave, and becomes the reference light. The reference light enters the half mirror 17 after passing through the collimator lens 27, and is partially reflected.
[0050]
In the half mirror 17, the light in which the partially reflected reference light and the partially transmitted measurement light overlap each other passes through the transparent optical window 12 and reaches the detection unit 8. The detector 8 observes interference fringes corresponding to the phase difference between the two. Since the phase difference corresponds to the disturbance of the wavefront due to the measured optical system, the optical characteristics of the measured optical system can be measured based on the state of the interference fringes.
[0051]
Even in such a configuration, the optical path in the optical attenuation / interference optical system does not fluctuate due to mixing of oxygen. Further, since the container 1 is not deformed, no error occurs due to the distortion of the interference optical system.
[0052]
Therefore, in the present embodiment, by preventing distortion of the interference optical system, fluctuation in the interference optical system, and entry of oxygen into the interference optical system, it is possible to provide an interference measurement device in which no error occurs.
[0053]
Embodiment 3
In the configuration shown in FIG. 1, the optical path length of the measurement light is longer than the optical path length of the reference light because it passes through the optical system to be measured. In such a configuration, if a short pulse laser such as an excimer laser is used as the light source, the optical path difference between the measurement light and the reference light may be longer than the pulse length of the light source light. In this case, the measurement light and the reference light do not overlap in the detection unit, and no interference fringe is generated. FIG. 3 shows a configuration in which the optical path lengths of the measurement light and the reference light are adjusted so that the optical path of the measurement light and the optical path of the reference light have substantially the same distance.
[0054]
That is, FIG. 3 is a conceptual diagram showing a third embodiment of the present invention. Hereinafter, an embodiment of the invention will be described with reference to FIG. In FIG. 3, 31 and 34 are half mirrors, 32 and 33 are bending mirrors, and 42 is a light source. The light source 42 is an excimer laser that oscillates short pulse light in a vacuum ultraviolet region. Other configurations are the same as in the first embodiment.
[0055]
In this configuration, light from the light source 42 is split by the half mirror 31. Of the split light beams, the light beam partially transmitted through the half mirror 31 is used as measurement light. On the other hand, the light beam partially reflected by the half mirror 31 passes through the bending mirrors 32 and 33 and the half mirror. This light beam is used as reference light. With such a configuration, the optical path length of the reference light can be extended, and the optical path of the measurement light and the optical path of the reference light can be made substantially the same distance, so that interference fringes can be generated.
[0056]
A method for measuring the optical characteristics of the optical system using the interference measurement device according to the present embodiment will be described. First, the process of adjusting the interference optical system through the openings of the container 1 and the container 15 and covering the openings is performed in the same manner as in Example 1, and the inside of the container 1 and the container 15 is replaced with nitrogen.
[0057]
Here, the measurement of interference fringes will be specifically described below. After the light beam emitted from the light source 42 passes through the transparent optical window 12, the light beam is split by the half mirror 31 into two light beams.
[0058]
Of the divided light beams, the light beam partially transmitted through the half mirror 31, that is, the measurement light partially transmits the half mirror 34 and the half mirror 3, further passes through the transparent optical window 12, and passes through the condensing lens 20. And enters the optical system to be measured. The light beam that has passed through the measured optical system is reflected by the reflection mirror 21, passes through the measured optical system and the condenser lens 20, and passes through the transparent optical window 12 again. Further, after being partially reflected by the half mirror 3 and reflected by the bending mirror 6, the light enters the half mirror 7.
[0059]
On the other hand, the light beam partially reflected by the half mirror 31, that is, the reference light, passes through the bending mirror 32 and the bending mirror 33, is partially reflected by the half mirror 34, and is partially reflected by the half mirror 3. Further, the light enters the half mirror 7 after passing through the bending mirrors 4 and 5.
[0060]
The measurement light partially transmitted through the half mirror 7 and the reference light partially reflected by the half mirror 7 are overlapped to generate an interference fringe. Then, the optical characteristics of the measured optical system are measured by observing the interference fringes.
[0061]
Also in the present embodiment, it is possible to provide an interference measurement device that does not generate an error by preventing distortion of the interference optical system, fluctuation in the interference optical system, and mixing of oxygen into the interference optical system.
[0062]
The case where the optical characteristics of the optical system are measured has been described above, but the measurement results are good even when the optical characteristics of the optical element are measured using any of the embodiments.
[0063]
Embodiment 4
FIG. 6 is a conceptual diagram of a projection exposure apparatus using the optical system of the present invention. The projection exposure apparatus is an apparatus that performs a reduced projection exposure of a mask pattern of a reticle on a wafer having a surface coated with a photoresist.
[0064]
6, reference numeral 100 denotes a light source that emits vacuum ultraviolet light such as an excimer laser, R denotes a reticle having a mask pattern, 101 denotes an illumination optical system that irradiates light from the light source 100 onto the reticle R, and W denotes a photoresist 701. A wafer coated on the surface, 500 is a projection optical system for reducing and exposing the mask pattern of the reticle R onto the wafer W, 301 is a wafer stage for moving the wafer W, and 201 is a reticle stage for moving the reticle R.
[0065]
The vacuum ultraviolet light emitted from the light source 100 is shaped and uniformed by the illumination optical system 101, and then is applied to the reticle R and transmitted through the reticle R. The projection optical system 500 irradiates the wafer W with the light transmitted through the reticle R, thereby reducing and exposing the mask pattern of the reticle R on the surface of the wafer W.
[0066]
The projection optical system 500 is an optical system that projects the pattern of the reticle R onto the wafer W in a very small scale, and requires high resolution. In order to manufacture the projection optical system 500 with high resolution, it is necessary to measure and adjust the optical characteristics of the projection optical system 500 with high accuracy. Since the optical system of the present invention has no measurement error of the optical characteristics, the adjustment is good, and the projection exposure apparatus using the optical system can secure high imaging performance.
[0067]
It is needless to say that an optical system other than the projection optical system 500 can be a projection exposure apparatus having high imaging performance if it is configured by the present invention.
[0068]
【The invention's effect】
According to the present invention, inside the first container having an opening communicating with the outside, a second container having an opening communicating with the first container is provided, and distortion of the interference optical system housed in the second container is provided. By preventing fluctuations in the interference optical system and the incorporation of oxygen into the interference optical system, it is possible to provide an interference measurement device that does not generate an error.
[Brief description of the drawings]
FIG. 1 is a conceptual diagram of an interference measurement device according to a first embodiment of the present invention.
FIG. 2 is a conceptual diagram of an interference measurement device according to a second embodiment of the present invention.
FIG. 3 is a conceptual diagram of an interference measurement device according to a third embodiment of the present invention.
FIG. 4 is a conceptual diagram showing a conventional interference measurement device.
FIG. 5 is a conceptual diagram showing another conventional interference measurement device.
FIG. 6 is a conceptual diagram of a projection exposure apparatus.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 2nd container 15 1st container 2, 42 Light source 3, 7, 13, 14, 17, 31, 34 Half mirror 4, 5, 6, 16, 19, 32, 33 Bending mirror 8 Detector 12 Transparent optics Windows 20, 25 Condensing lens 21 Return reflecting mirror 26 Pinhole 27 Collimator lenses 81, 82, 83, 84 Valves 97, 98 Gas supply unit

Claims (12)

A first container, a second container housed in the first container, in which an interference optical system for performing interference measurement of an optical system to be measured or an optical element to be measured is arranged, a light source, and detection. An interference measurement method for performing interference measurement of an optical element to be measured or an optical system to be measured, using an interference measurement device comprising:
A first supply step of supplying a first gas different from the atmosphere into the first container; a second supply step of supplying a second gas different from the atmosphere into the second container; An interference measurement step of performing interference measurement of the measurement optical element or the optical system to be measured, wherein the interference measurement step is performed after the second supply step is completed. In the interference measurement method according to claim 1,
The interference measurement method, wherein the first supply step is performed during the interference measurement step. In the interference measurement method according to claim 1,
The first gas and the second gas are each one of nitrogen, helium, and argon. The interference measurement method according to claim 3,
The said 1st gas is the same kind as the said 2nd gas, The interference measuring method characterized by the above-mentioned. In the interference measurement method according to claim 1,
The wavelength of light from the light source is 200 nm or less. In the interference measurement method according to claim 1,
The said 2nd supply process is a process of supplying the gas inside the said 1st container inside the said 2nd container, The interference measurement method characterized by the above-mentioned. An interference measurement apparatus that performs interference measurement of the measured optical system or the measured optical element,
A first container, housed in the first container, a second container in which an interference optical system for performing interference measurement of the measured optical system or the measured optical element is disposed, and a light source. Having a first gas supply means for supplying a gas to the inside of the first container,
The first container has an opening communicating with the outside of the first container,
The said 2nd container has an opening part connected to the said 1st container, The interference measuring apparatus characterized by the above-mentioned. The interference measurement apparatus according to claim 7,
An interferometer having a second gas supply means for supplying the gas inside the second container. The interference measurement apparatus according to claim 7,
The wavelength of light emitted from the light source is 200 nm or less. 7. An optical element whose optical characteristics have been measured by the method according to claim 1. 7. An optical system, wherein the optical characteristics are measured by the method according to claim 1. A projection exposure apparatus using the optical system according to claim 11.

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