JP2004245744A - Measuring device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a measuring device having high measuring precision of aberration of a wave surface by making detection of the aberration of the wave surface possible by a Moire fringe, having a good contrast while using a F<SB>2</SB>laser of a wavelength of 157 nm. <P>SOLUTION: The measuring device is a device for measuring an aberration of wave surface of a measuring body and comprises: a light focusing optical system focusing an emission light from a light source on a body or an image; a reflection light system having a center of curvature, arranged on the image of the body or on the surface of the body under measurement; a detection optical system for observation of the Moire fringe, wherein the F<SB>2</SB>laser is used for the light source. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates generally to measuring devices, and in particular, to F ₂ The present invention relates to a measuring apparatus for measuring a wavefront aberration of an optical system used for a laser.
[0002]
[Prior art]
When a fine semiconductor element such as a semiconductor memory or a logic circuit is manufactured using a photolithography (printing) technique, a circuit pattern drawn on a reticle or a mask (these terms are used interchangeably in the present application). A projection exposure apparatus that projects a circuit pattern onto a wafer or the like by a projection optical system to transfer a circuit pattern has conventionally been used.
[0003]
The minimum dimension (resolution) that can be transferred by the projection exposure apparatus is proportional to the wavelength of light used for exposure and inversely proportional to the numerical aperture (NA) of the projection optical system. Therefore, the shorter the wavelength, the better the resolution. For this reason, with the recent demand for miniaturization of semiconductor elements, the exposure light source is an ultra-high pressure mercury lamp (i-line (wavelength: about 365 nm)), KrF excimer laser (wavelength: about 248 nm), ArF excimer laser (wavelength: about 193 nm) And the wavelength has been shortened. ₂ The use of lasers (wavelength about 157 nm) is promising.
[0004]
Further, when the projection lens constituting the projection optical system is deformed, the optical path is refracted before and after the deformation, and the light rays to be imaged at one point do not converge at one point, causing an aberration. The aberration causes a displacement and a short circuit of the circuit pattern on the wafer. On the other hand, if the pattern size is increased in order to prevent a short circuit, it is against the demand for miniaturization. Therefore, it is necessary to assemble and adjust the wavefront aberration of the projection lens so as to be close to that of the ideal lens. For that purpose, it is essential to measure the wavefront aberration of the projection lens.
[0005]
At the wavelength of 365 nm, projection is performed by forming a stable interferometer represented by a Fizeau type using an oscillation wavelength of 363.8 nm of an Ar ion laser having a long coherence distance with respect to an exposure wavelength of 365 nm of i-line. Measurement of the wavefront aberration of the lens is possible. For the difference between the two wavelengths, the wavefront aberration at the exposure wavelength can be obtained by correcting the measured value using, for example, chromatic aberration in design.
[0006]
In addition, at a wavelength of 248 nm, a stable interferometer represented by a Fizeau-type using a second harmonic of 248.248 nm of an Ar ion laser having a long coherence distance with respect to an exposure wavelength of 248.248 nm of a KrF excimer laser. Is configured, it is possible to measure the wavefront aberration of the projection lens. In such a case, there is no need to correct the measured values using chromatic aberration, because the two wavelengths are exactly the same.
[0007]
Further, at a wavelength of 193 nm, it is difficult to obtain a stable light source with good coherence, but it is possible to oscillate pulsed light at a high frequency, and by constructing an interferometer using such oscillation wavelength, the projection lens Measurement of wavefront aberration is possible.
[0008]
[Problems to be solved by the invention]
However, at a wavelength of 157 nm, it is very difficult to obtain a stable light source with good coherence. Therefore, the actual F ₂ The use of a laser is also conceivable. However, when the test lens has chromatic aberration such as a projection lens, F ₂ Since the spectral width of the laser is as wide as about 1 pm, the interference fringes are shifted little by little and overlap, thereby lowering the measurement accuracy of the wavefront aberration.
[0009]
Therefore, at this stage, at a wavelength of 157 nm, an interferometer for measuring the wavefront aberration cannot be configured. Therefore, a method other than actually printing a pattern by exposure and assembling and adjusting a projection lens from the printing characteristics is used. Absent. In such a method, there is a problem that it takes a long time for exposure and an adjustment accuracy is insufficient.
[0010]
Therefore, the present invention provides an F ₂ An exemplary object of the present invention is to provide a measuring apparatus which enables detection of wavefront aberration by interference fringes having good contrast while using a laser, and which has excellent measurement accuracy of such wavefront aberration.
[0011]
[Means for Solving the Problems]
In order to achieve the above object, a measuring apparatus according to one aspect of the present invention includes a condensing optical system that condenses light emitted from a light source on an object plane or an image plane of a measurement object, and the measurement object. A reflection optical system in which the center of curvature is arranged on the image plane or the object plane, and a detection optical system for observing interference fringes, which is a measuring device for measuring the wavefront aberration of the object to be measured. , The light source is F ₂ It is a laser.
[0012]
A measuring method according to another aspect of the present invention is a measuring method for measuring a wavefront aberration of an object to be measured. ₂ To reduce the spectral width of the laser, the F ₂ Changing the gas pressure of the laser; ₂ Irradiating the object to be measured with a laser. The F ₂ The gas pressure of the laser is not less than 100 kPa and not more than 500 kPa. The F ₂ The laser has a spectrum width of 0.2 pm or more and 1.0 pm or less.
[0013]
A measurement method according to still another aspect of the present invention is a measurement method for measuring a wavefront aberration of an object to be measured, wherein F is applied to the object to be detected. ₂ Changing the gas pressure of the laser; and ₂ Calculating the center wavelength of the laser; and calculating the F ₂ Correcting the wavefront aberration of the measured object based on the center wavelength of the laser and the wavefront aberration sensitivity of the measured object. The correction step is a step of obtaining a wavelength difference between the center wavelength and the reference wavelength calculated in the calculation step, a step of obtaining a correction value from the wavelength difference and the wavefront aberration sensitivity of the measured object, Subtracting the correction value from the measured wavefront aberration of the measured object.
[0014]
A measuring device as still another aspect of the present invention is a measuring device for measuring a wavefront aberration of a device under test, wherein the light source that emits light having a predetermined spectral width interferes with the wavefront aberration of the device under test. It is characterized by having a detection optical system for detecting as a fringe, and adjusting means for adjusting the spectral width of light emitted from the light source. The light is F ₂ It is a laser. The adjustment means adjusts the spectrum width so that the detection optical system can detect the interference fringes. The adjusting means adjusts the spectrum width by changing a gas pressure of the light.
[0015]
An adjustment method according to still another aspect of the present invention is an adjustment method for adjusting an exposure apparatus having a light source that emits light having a predetermined spectral width. Correcting the wavefront aberration so as to show a state before the adjustment of the spectrum width.
[0016]
According to still another aspect of the present invention, there is provided an exposure method for illuminating a pattern formed on a mask using light having a predetermined spectral width during exposure, and exposing the pattern to an object to be processed via an optical system. A method, the step of narrowing the predetermined spectral width of the light than at the time of the exposure, and measuring the wavefront aberration of the optical system using the light of the narrowed spectral width, Correcting the measured wavefront aberration from the center wavelength of the light having the narrowed spectral width and the wavefront aberration sensitivity of the optical system, so that the corrected wavefront aberration is reduced. The method includes adjusting an optical system and returning the light having the narrowed spectral width to the predetermined spectral width.
[0017]
An exposure apparatus according to still another aspect of the present invention is an exposure apparatus that exposes a pattern formed on a mask to a target object via a projection optical system including an optical element, and the measurement apparatus described above. A driving unit for driving the optical element based on the wavefront aberration of the projection optical system measured by the measuring device.
[0018]
A device manufacturing method according to still another aspect of the present invention includes a step of exposing an object to be processed using the above-described exposure apparatus, and a step of performing a predetermined process on the exposed object to be processed. And
[0019]
Further objects and other features of the present invention will become apparent from preferred embodiments described below with reference to the accompanying drawings.
[0020]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, a measurement apparatus 100 and an exposure apparatus 200 according to one aspect of the present invention will be described with reference to the accompanying drawings. In each of the drawings, the same members are denoted by the same reference numerals, and redundant description will be omitted. Here, FIG. 1 is a schematic configuration diagram illustrating an exemplary embodiment of a measuring apparatus 100 according to one aspect of the present invention.
[0021]
The measuring device 100 is used for the F ₂ With a laser as a light source 110, a Twyman-Green interferometer is configured, and a wavefront aberration measuring apparatus capable of automatically measuring a wavefront aberration of a measurement target T such as a projection optical system of an exposure apparatus with respect to an arbitrary measurement point on a screen. is there. Hereinafter, in the present embodiment, the measurement target T will be described as a projection optical system. As shown in FIG. 1, the measuring apparatus 100 includes a light source 110, an interferometer unit 120, a routing optical system 130, a TWG-XYZ stage 140, a Twyman green unit 150, an RS-XYZ stage 160, It has a unit 170 and an adjusting unit 180.
[0022]
The measuring apparatus 100 forms interference fringes by superimposing the test light and the reference light, and measures the wavefront aberration of the test object T. First, the test light will be described. F from light source 110 ₂ The laser light is guided to the interferometer unit 120. Inside the interferometer unit 120, a light beam is collected on a spatial filter 122 by a condenser lens 121. Here, the diameter of the spatial filter 122 is set to about 1/2 of the Airy disk diameter determined by the numerical aperture (NA) of the collimator lens 124. Thereby, the light emitted from the spatial filter 122 becomes an ideal spherical wave, passes through the half mirror 123, is converted into parallel light by the collimator lens 124, and is emitted from the interferometer unit 120. After that, the TWG-XYZ stage 140 (the TWG-XYZ stage 140 includes the X stage 142, the Y stage 144, and the Z stage 146) is guided by the routing optical system 130 to an upper portion of the object surface (reticle surface) of the measured object T. ).
[0023]
The parallel light incident on the TWG-XYZ stage 140 is reflected in the Y direction by a mirror M1 fixedly disposed on the stage base SB, and is reflected in the X direction by a mirror M2 movable on the Y stage disposed on the Y stage 144. Then, the light is reflected in the Z direction by a mirror M3 that can be moved in the X direction and is incident on the Wyman green unit 150.
[0024]
Inside the Twyman green unit 150, after passing through the half mirror 151, it is condensed by the collimator lens 154 onto the object surface (reticle surface) of the measured object T, and after passing through the measured object T, the image plane ( (The wafer surface). The Twyman green unit 150 has a function as an imaging optical system.
[0025]
Thereafter, the re-imaged light is reflected by the RS mirror 168 arranged on the RS-XYZ stage 160 (the RS-XYZ stage 160 includes the X stage 162, the Y stage 164, and the Z stage 166), and The measurement object T, the collimator lens 154, the half mirror 151, the mirror M3, the mirror M2, the mirror M1, and the routing optical system 130 travel backward in almost the same optical path, and then enter the interferometer unit 120 again.
[0026]
The light that has entered the interferometer unit 120 is reflected by the collimator lens 124 and the half mirror 123 and is collected on the spatial filter 125. Here, the spatial filter 125 blocks stray light and steeply inclined wavefronts. The light having passed through the spatial filter 125 is incident on the CCD camera 127 by the imaging lens 126 as a substantially parallel light beam.
[0027]
On the other hand, in the Twyman Green unit 150, the reference light is reflected by the half mirror 151 so that the luminous flux is reversed by the reference mirror 152, reflected again by the half mirror 151, and guided to the CCD camera 127. Here, the distance between the half mirror 151 and the reference mirror 152 is designed to be equal to the optical path length from the half mirror 151 to the RS mirror 168. Usually, in the case of a projection lens mounted on an exposure apparatus, such an optical path length is 3 m or more, and the Twyman Green unit 150 needs to be disposed on the Z stage 146. ing. Here, a so-called fringe scanning method, that is, by scanning the PZT element 153 about the wavelength in the optical axis direction, enables highly accurate phase detection. In this way, the reference light and the test light are superimposed to form interference fringes, which can be detected by the CCD camera 127. The interferometer unit 120 has a function as a detection optical system.
[0028]
Here, the TWG-XYZ stage 140 (the X stage 142, the Y stage 144, the Z stage 146) and the RS stage 160 (the X stage 162, the Y stage 164, the Z stage 166) are controlled by the control unit 170 to control the TWG-XYZ. The target T can be moved to an arbitrary image height position via the stage driving unit 140a and the RS-XYZ stage driving unit 160a. Therefore, for example, it is possible to continuously measure the wavefront aberration at an arbitrary image point in the exposure area.
[0029]
Next, the light source 110 will be described in detail. The light source 110 is used as a light source for measuring interference fringes. ₂ Use a laser. F ₂ The half-width of the spectrum of the laser is about 1 pm, and it is possible to construct an interferometer for measuring the surface shape or the like as it is. However, an interferometer for measuring the wavefront aberration of a projection lens for an exposure apparatus is used. Is difficult to configure for the following reasons.
[0030]
Usually, the projection lens for the exposure apparatus is F ₂ The chromatic aberration is designed to be sufficiently small so that the resolution characteristics (contrast and the like) of the pattern are not deteriorated even under the condition that the laser half width at half maximum is 1 pm. However, under such conditions, the contrast of interference fringes deteriorates too much, and it is difficult to obtain sufficient accuracy. Therefore, it is necessary to narrow the spectrum of the light source 110 to prevent the contrast of the interference fringes from deteriorating.
[0031]
However, for example, due to the narrowing unit, F ₂ When the band of the laser is narrowed, unlike conventional KrF excimer lasers and ArF excimer lasers, ₂ A significant decrease in laser power occurs. Further, it is difficult to obtain an optical member having good transmission characteristics at such a wavelength, and thus it is also difficult to manufacture a band narrowing unit. That is, F of a wavelength of 157 nm ₂ In a laser, it is extremely difficult to reduce the spectral half width by a band narrowing unit.
[0032]
Therefore, in the present invention, F ₂ Adjustment means 180 for adjusting the half-width of the spectrum of the laser is provided. More specifically, the adjusting unit 180 is controlled by the control unit 170 so that the interferometer unit 120 can detect the interference fringe so that the interference fringe can be detected. ₂ Adjust the half bandwidth of the laser spectrum. In the present embodiment, the adjusting means 180 ₂ Focusing on the fact that the spectrum half-width changes due to the change in laser gas pressure, F ₂ By changing the laser gas pressure, F ₂ The narrow band of laser is realized. However, the adjusting means 180 ₂ The present invention is not limited to changing the gas pressure of the F2 laser as long as it is possible to change the laser half width.
[0033]
FIG. 2 is a graph showing the relationship between the half width of the spectrum of the light source 110 and the contrast of interference fringes. In the figure, the horizontal axis represents the half width of the spectrum of the light source 110, and the vertical axis represents the contrast of the interference fringes. Note that the calculation is performed by setting the chromatic aberration amount of the measured object T to 0.2λ / pm (single pass) and integrating the interference intensity generated at each wavelength within the spectrum width. Here, the shape of the spectrum was assumed to be both Gaussian type and Lorentz type. Hereinafter, the description will be made mainly about the Lorentz type in which the contrast is greatly reduced.
[0034]
Referring to FIG. 2, when the spectral half width of the light source 110 is 1 pm, the contrast is reduced to 30% in the Lorentz type (60% in the Gaussian type). On the other hand, in order to measure interference fringes with high accuracy, it is necessary to suppress the decrease in contrast due to chromatic aberration to 40%, although it depends on disturbance conditions such as vibration. In this case, FIG. 2 shows that the half width of the spectrum of the light source 110 may be set to 0.7 pm or less.
[0035]
Further, FIG. ₂ FIG. 3B is a graph showing the relationship between the gas pressure of the laser and the half width of the spectrum. ₂ 3 is a graph showing a relationship between a laser gas pressure and a center wavelength. FIG. 3A shows that F is plotted on the horizontal axis. ₂ The gas pressure of the laser is adopted, and the half-width of the spectrum is adopted on the vertical axis. In FIG. ₂ The gas pressure of the laser is employed, and the center wavelength is employed on the vertical axis. The graphs in FIGS. 3A and 3B are shown in APPLIED OPTICS / 20 April 2001 / Vol. 40, no. 12 was prepared.
[0036]
Referring to FIG. 3A, it can be seen that, when the gas pressure is reduced by about 200 kPa with respect to the use state at the time of exposure, the half width of the spectrum can be reduced from 1 pm to 0.5 pm. However, as shown in FIG. 3B, the center wavelength changes simultaneously with the change in gas pressure, and under the conditions of the present embodiment, a center wavelength shift of −0.3 pm occurs. This is an amount exceeding the measurement accuracy required for the wavefront aberration for the projection lens and cannot be ignored. Therefore, it is necessary to use the measurement method 1000 described below with reference to FIG.
[0037]
FIG. 4 is a flowchart for explaining the measuring method 1000 of the present invention. The measurement method 1000 is a measurement method for measuring the wavefront aberration of the measured object T, and is an example in which a center wavelength shift caused by changing a gas pressure is considered. In the measurement method 1000, the following processing is performed in the control unit 170 to correct the measured wavefront aberration. First, a gas pressure is received from the light source 110 by communication (step 1002). Next, the central wavelength after changing the gas pressure is calculated from the relationship between the gas pressure received in step 1002 and the gas pressure and the central wavelength shown in FIG. 3B (step 1004). Further, a wavelength difference between the center wavelength after changing the gas pressure and the reference wavelength (center wavelength at the time of exposure) is calculated (step 1006). Further, the control unit 170 records the wavefront aberration sensitivity of the design wavefront aberration of the measured object T, and calculates a correction value from the wavelength difference obtained in step 1006 and the wavefront aberration sensitivity (step 1006). 1008). Then, by subtracting the correction value from the measured wavefront aberration (that is, the measured value) (step 1010), the wavefront aberration at the time of exposure can be obtained.
[0038]
As described above, the description has been given on the condition that the contrast of the interference fringes is required to be 50% or more in order to measure the interference fringes with high accuracy. The contrast of the fringe is determined, and the half-width, the gas pressure, and the center wavelength shift are sequentially obtained from FIGS. 2 and 3 using the above-described measurement method 1000, and the measured wavefront aberration may be corrected as necessary. .
[0039]
As a result, at a wavelength of 157 nm, the exposure light source F ₂ Even when a laser is used, interference fringes with good contrast can be obtained, and highly accurate measurement of wavefront aberration becomes possible.
[0040]
Hereinafter, an exposure apparatus 200 according to one aspect of the present invention will be described with reference to FIG. FIG. 5 is a schematic configuration diagram illustrating an exemplary embodiment of an exposure apparatus 200 according to one aspect of the present invention. The exposure apparatus 200 is obtained by applying the measurement apparatus 100 to an exposure apparatus. The exposure apparatus 200 uses F as exposure illumination light. ₂ This is a projection exposure apparatus that exposes a circuit pattern formed on the mask 210 to the wafer 214 by using, for example, a laser in a step-and-scan method or a step-and-repeat method. Such an exposure apparatus is suitable for a submicron or quarter-micron lithography process. Hereinafter, in this embodiment, a step-and-scan type exposure apparatus (also referred to as a “scanner”) will be described as an example. Here, the “step-and-scan method” means that a wafer is continuously scanned (scanned) with respect to a mask to expose a mask pattern to the wafer, and the wafer is step-moved after one-shot exposure is completed. This is an exposure method for moving to the next exposure area. The “step-and-repeat method” is an exposure method in which the wafer is step-moved for each batch exposure of the wafer and moved to the next exposure area.
[0041]
The basic configuration of the exposure apparatus 200 is the same as that of the prior application, Japanese Patent Application Publication No. 2000-277412. Referring to FIG. 5, F emitted from light source 110 ₂ The laser is converted into a beam shape symmetric with respect to the optical axis by the beam shaping optical system 202, and is guided to the optical path switching mirror 204. The optical path switching mirror 204 is arranged outside the optical path during normal exposure.
[0042]
The light beam emitted from the beam shaping optical system 202 is incident on the incoherent optical system 206, passes through the illumination optical system 208 after reducing the coherence, and illuminates the mask (or mask surface) 210. Light that passes through the mask 210 and reflects the mask pattern is imaged by the projection optical system 212 at a wafer surface position 214a where the wafer 214 is arranged. In FIG. 5, the wafer 214 is not positioned at the wafer surface position 214a because the exposure is not shown, but is moved to the wafer surface position 214a by the wafer stage 216 during the exposure.
[0043]
On the other hand, except during exposure, the optical path switching mirror 204 is disposed in the optical path. The light beam from the beam shaping optical system 202 is reflected by the optical path switching mirror 204, guided to the routing optical system 220, and guided to the vicinity of the interferometer unit 120 arranged near the mask 210. The light beam emitted from the routing optical system 220 is collected at one point by the condenser lens 222. Here, a pinhole 224 is arranged near the focal point of the condenser lens 222.
[0044]
The light beam that has passed through the pinhole 224 is converted by the collimator lens 226 into parallel light. The diameter of the pinhole 224 is set to be approximately the same as the diameter of the Airy disk determined by the numerical aperture (NA) of the collimator lens 226. As a result, the light beam emitted from the pinhole 224 is an almost ideal spherical wave. The parallel light from the collimator lens 226 is reflected by the half mirror 228 and enters the Twyman Green unit 150 mounted on the TWG-XYZ stage 140. The light beam incident on the Twyman Green unit 150 is split into the test light and the reference light as described above, and is overlapped by the interferometer unit 120 to form interference fringes.
[0045]
When the Twyman Green unit 150 is not mounted, the interferometer unit 120 has a function of detecting the above-described interference fringes (that is, the condenser lens 121, the spatial filter 122, the imaging lens 126, and the CCD camera 127). However, when the Twyman Green unit 150 is not mounted, as shown in Japanese Patent Application Laid-Open Publication No. 2000-277412, the interference with the reference light test light is divided and superposed in the interferometer unit 120. What is necessary is just to be the structure which implement | achieves a system. For example, there are a lateral shear type and a radial shear type interferometer type.
[0046]
Here, an exposure method 2000 using the exposure apparatus 200 will be described with reference to FIG. FIG. 6 is a flowchart for explaining the exposure method 2000 of the present invention. The exposure method 2000 is a method for performing exposure by adjusting the projection optical system 212 (that is, adjusting the wavefront aberration of the projection optical system 212 to be within the range of the wavefront aberration optimal for exposure).
[0047]
Normally, the light source 110 is set to the gas pressure at the time of exposure, but before measuring the wavefront aberration of the projection optical system 212, the control unit 170 transmits a command to change the gas pressure to the adjusting unit 170 (step 2002). According to such a command, F ₂ The bandwidth of the laser half-width is narrowed (for example, 0.5 pm or less) (step 2004). F ₂ After narrowing the bandwidth of the laser half width, a command for measuring the wavefront aberration of the projection optical system 212 is transmitted.For example, in the case of the Twyman Green type, by driving the reference mirror, a so-called Wavefront aberration is measured by the fringe scan method (step 2006). After measuring the wavefront aberration, the control unit 170 changes the changed F ₂ The gas pressure of the laser is received (Step 2008), and the center wavelength after changing the gas pressure is calculated (Step 2010). Further, a wavelength difference between the center wavelength after changing the gas pressure and the reference wavelength (center wavelength at the time of exposure) is calculated (step 2012), and a correction value is calculated from the wavelength difference and the wavefront aberration sensitivity (step 2012). 2014). Then, the wavefront aberration at the time of exposure (exposure wavelength) is obtained from the wavefront aberration (that is, the measured value) measured in step 2006 and the correction value obtained in step 2014 (step 2016). Thereafter, a command to return to the normal gas pressure (gas pressure at the time of exposure) is transmitted from the control unit 180 (step 2018), and the F in the exposure state is transmitted. ₂ The spectrum half width and the center wavelength of the laser are reset (step 2020). If the wavefront aberration obtained in step 2016 exceeds the allowable range (that is, if the imaging performance is adversely affected), the control unit 170 causes the driving unit 212a to reduce the projection optical system so that the wavefront aberration is reduced. The projection optical system 212 is adjusted by driving the optical elements constituting the 212 (step 2022). In this way, exposure is performed after the wavefront aberration of the projection optical system 212 is adjusted to a range suitable for exposure.
[0048]
Next, an embodiment of a device manufacturing method using the exposure apparatus 200 will be described with reference to FIGS. FIG. 7 is a flowchart for explaining the manufacture of devices (semiconductor chips such as ICs and LSIs, LCDs, CCDs, etc.). Here, the manufacture of a semiconductor chip will be described as an example. In step 1 (circuit design), the circuit of the device is designed. Step 2 (mask fabrication) forms a mask on which the designed circuit pattern is formed. In step 3 (wafer manufacturing), a wafer is manufactured using a material such as silicon. Step 4 (wafer process) is called a preprocess, and an actual circuit is formed on the wafer by lithography using the mask and the wafer. Step 5 (assembly) is called a post-process, and is a process of forming a semiconductor chip using the wafer created in step 4, and includes processes such as an assembly process (dicing and bonding) and a packaging process (chip encapsulation). . In step 6 (inspection), inspections such as an operation check test and a durability test of the semiconductor device created in step 5 are performed. Through these steps, a semiconductor device is completed and shipped (step 7).
[0049]
FIG. 8 is a detailed flowchart of the wafer process in Step 4. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the surface of the wafer. Step 13 (electrode formation) forms electrodes on the wafer by vapor deposition or the like. Step 14 (ion implantation) implants ions into the wafer. In step 15 (resist processing), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus 200 to expose a circuit pattern on the mask onto the wafer. Step 17 (development) develops the exposed wafer. Step 18 (etching) removes portions other than the developed resist image. Step 19 (resist stripping) removes unnecessary resist after etching. By repeating these steps, multiple circuit patterns are formed on the wafer. According to such a device manufacturing method, it is possible to manufacture a device of higher quality than before. As described above, the device manufacturing method using the exposure apparatus 200 and the resulting device also constitute one aspect of the present invention.
[0050]
The preferred embodiments of the present invention have been described above. However, it goes without saying that the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the invention.
[0051]
The present application further discloses the following matters.
[0052]
[Embodiment 1] A condensing optical system for condensing light emitted from a light source on an object plane or an image plane of a measured object, and a center of curvature is arranged on an image plane or an object plane of the measured object. Reflection optical system, having a detection optical system for observing interference fringes, a measuring apparatus for measuring the wavefront aberration of the measured object,
The light source is F ₂ A measuring device characterized by being a laser.
[0053]
[Embodiment 2] A measurement method for measuring a wavefront aberration of a measured object,
F to irradiate the object to be measured ₂ To reduce the spectral width of the laser, the F ₂ Changing the gas pressure of the laser;
The F having reduced spectrum width ₂ Irradiating the object to be measured with a laser.
[0054]
[Embodiment 3] The above F ₂ The measurement method according to embodiment 2, wherein the laser gas pressure is 100 kPa or more and 500 kPa or less.
[0055]
[Embodiment 4] The above F ₂ 3. The measuring method according to claim 2, wherein the spectrum width of the laser is 0.7 pm or less.
[0056]
[Embodiment 5] A measurement method for measuring a wavefront aberration of an object to be measured,
F applied to the object to be detected ₂ Changing the gas pressure of the laser;
Based on the gas pressure, the F ₂ Calculating the center wavelength of the laser;
The F calculated in the calculation step ₂ Correcting the wavefront aberration of the measured object based on the center wavelength of the laser and the wavefront aberration sensitivity of the measured object.
[0057]
[Embodiment 6] The correction step includes:
Obtaining a wavelength difference between the center wavelength and the reference wavelength calculated in the calculation step,
Obtaining a correction value from the wavelength difference and the wavefront aberration sensitivity of the measured object,
Subtracting the correction value from the measured wavefront aberration of the measured object.
[0058]
[Embodiment 7] A measuring device for measuring a wavefront aberration of a measured object,
A light source that emits light having a predetermined spectral width,
A detection optical system that detects the wavefront aberration of the measured object as interference fringes,
Adjusting means for adjusting the spectral width of light emitted from the light source.
[0059]
Embodiment 8 The light is F ₂ The measuring device according to embodiment 7, wherein the measuring device is a laser.
[0060]
[Embodiment 9] The measuring apparatus according to embodiment 7, wherein the adjusting means adjusts the spectrum width so that the detection optical system can detect the interference fringes.
[0061]
[Embodiment 10] The measuring apparatus according to Embodiment 7, wherein the adjusting means adjusts the spectrum width by changing a gas pressure of the light.
[0062]
Embodiment 11 is an adjustment method for adjusting an exposure apparatus having a light source that emits light having a predetermined spectral width,
Obtaining the wavefront aberration by adjusting the spectral width;
Correcting the wavefront aberration so as to show a state before adjusting the spectrum width.
[0063]
(Embodiment 12) An exposure method of illuminating a pattern formed on a mask with light having a predetermined spectral width at the time of exposure, and exposing the pattern to an object to be processed via an optical system,
Step of narrowing the predetermined spectral width of the light to a band narrower than at the time of the exposure,
Measuring the wavefront aberration of the optical system using the light of the narrowed spectral width,
Correcting the measured wavefront aberration from the center wavelength of the light having the narrowed spectral width and the wavefront aberration sensitivity of the optical system,
Adjusting the optical system so that the corrected wavefront aberration is reduced; and
Returning the light having the narrowed spectral width to the predetermined spectral width.
[0064]
[Embodiment 13] An exposure apparatus for exposing a pattern formed on a mask to an object to be processed via a projection optical system including an optical element,
Embodiment 1, the measuring device according to any one of 7 to 10,
An exposure device, comprising: driving means for driving the optical element based on the wavefront aberration of the projection optical system measured by the measurement device.
[0065]
[Embodiment 14] A step of exposing an object to be processed using the exposure apparatus according to Embodiment 13;
Performing a predetermined process on the exposed object to be processed.
[0066]
【The invention's effect】
According to the present invention, at a wavelength of 157 nm, F ₂ It is possible to detect a wavefront aberration due to interference fringes having a good contrast while using a laser, and it is possible to provide a measuring apparatus excellent in the measurement accuracy of the wavefront aberration.
[Brief description of the drawings]
FIG. 1 is a schematic configuration diagram showing an exemplary embodiment of a measuring device as one aspect of the present invention.
FIG. 2 is a graph showing the relationship between the half width of the spectrum of a light source and the contrast of interference fringes.
FIG. 3 (a) is an illustration of F ₂ FIG. 3B is a graph showing the relationship between the gas pressure of the laser and the half width of the spectrum. ₂ 4 is a graph showing the relationship between laser gas pressure and center wavelength.
FIG. 4 is a flowchart for explaining the measurement method of the present invention.
FIG. 5 is a schematic configuration diagram illustrating an exemplary embodiment of an exposure apparatus according to one aspect of the present invention.
FIG. 6 is a flowchart for explaining an exposure method of the present invention.
FIG. 7 is a flowchart for explaining the manufacture of devices (semiconductor chips such as IC and LSI, LCDs, CCDs, and the like).
FIG. 8 is a detailed flowchart of a wafer process in Step 4 shown in FIG. 7;
[Explanation of symbols]
100 measuring device
110 light source
120 interferometer unit
121 Condensing lens
122 Spatial Filter
123 half mirror
124 collimator lens
130 Routing optical system
140 TWG-XYZ stage
140a TWG-XYZ stage driver
150 Twyman Green Unit
151 half mirror
152 Reference mirror
153 PZT element
160 RZ-XYZ stage
160a RZ-XYZ stage driver
168 RZ mirror
170 control unit
180 adjustment means
T DUT
M1 to M3 mirror
200 Exposure equipment
204 Optical path switching mirror
212 Projection optical system
212a driving means
214 wafer
216 Wafer stage

Claims (1)

A condensing optical system that condenses the light emitted from the light source on the object plane or the image plane of the measured object, and a reflective optical system in which the center of curvature is arranged on the image plane or the object plane of the measured object Having a detection optical system for observing interference fringes, a measuring apparatus for measuring the wavefront aberration of the object to be measured,
It said light source, measurement device, characterized in that the F ₂ laser.

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