JP2009036601A - Calibration method for interference measuring instrument, interference measuring instrument, exposing device, and device manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the number of times of absolute value measurement by compensating system errors that an interference measuring instrument has simply in a short time. <P>SOLUTION: When measuring a transmitted wave front of a tested object 1 from measurement data on interference fringes obtained by causing tested light and reference light to interfere with each other, wave front measurement is performed by causing a spherical mirror 2 for measurement to reflect a light beam for test, and wave front measurement is performed by causing each of a plurality of spherical mirrors 4, 5, 6, and 7 for calibration to reflect the light beam. On and after a second transmitted wave front measurement, changes in system errors from those in measurement last time are detected based on data obtained this time and last time. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a calibration method for an interference measuring apparatus that measures a transmitted wavefront of a test object. The present invention further relates to an exposure apparatus and a device manufacturing method using the exposure apparatus.

Conventionally, an interference measurement device using light interference has been used for transmission wavefront measurement of a test object.
In the interference measurement apparatus, it is common to perform relative measurement between a transmitted wavefront of a test object and a reference surface. In order to measure the transmitted wavefront of the test object with high accuracy, it is desirable that the spherical mirror that reflects the test light transmitted through the reference surface and the test object is an ideal surface. However, the surface accuracy of the reference surface is often PV = λ / 10 to λ / 20, where λ is the wavelength of the light source, and the measurement accuracy cannot be higher than this surface accuracy. Therefore, in order to perform measurement with higher accuracy than this, it is necessary to measure the shape error (system error of the apparatus) of the reference surface and the spherical mirror and perform absolute calibration.

  As a method for measuring the system error, for example, a wavefront averaging method is known. Patent Document 1 discloses an example of an absolute shape measurement method using a wavefront averaging method.

  FIG. 2 shows a schematic diagram of a system error measuring apparatus using a reference plane. In this apparatus, the dummy true sphere 21 is used to cause interference between the reference light from the lens 3 having the reference surface and the test light from the dummy true sphere 21. Then, this interference measurement is performed a plurality of times while rotating the test light so that the test light strikes all the spherical surfaces of the dummy true sphere 21 by the rotation mechanism 22, and the obtained measurement data is averaged. By averaging, the influence on the measurement data due to the shape error of the dummy true sphere 21 can be reduced. As a result, the shape error of only the lens 3 can be obtained. However, this method assumes that the shape error of the dummy true sphere 21 is random.

The above is expressed as a mathematical formula as follows. When the measurement data is M _k , the shape error of the lens 3 is F, the shape error of the dummy true sphere 21 is W _k , and the measurement data M _k is averaged, the relationship of Expression (1) is established.

計測回数ｎを増やしていくと式１の右辺第二項は０に近づいていくので、レンズ３によるシステムエラーを求めることができる。
特開平５−２０３４２４号公報

As the number of measurements n is increased, the second term on the right side of Equation 1 approaches 0, so that a system error due to the lens 3 can be obtained.
Japanese Patent Laid-Open No. 5-203424

The system error of the interferometric measurement device may change due to environmental changes such as temperature and disturbances such as vibrations. System error needs to be measured. However, system error measurement including the above-described methods generally requires a relatively long time to measure with high accuracy.
Therefore, it is not efficient to perform system error measurement for a long time in order to confirm the stability of the system each time measurement is performed.
Accordingly, an object of the present invention is to provide a method for calibrating a measurement value of an interference measuring apparatus and a measuring apparatus that can solve the above-described problems.

  In order to solve the above-described problem, the first calibration method according to the present invention measures the transmitted wavefront of the test object from interference fringes caused by interference between the test light transmitted through the test object and the reference light. A calibration method for calibrating a measured value at the time, a first measurement step of measuring an interference fringe between the light transmitted through the test object and reflected by the spherical mirror for measurement of the transmitted wavefront and the reference light; A second measurement step of measuring interference fringes between the light transmitted through the test object and reflected by the calibration spherical mirror and the reference light, and the first measurement step and the second measurement step are performed once. And a calculation step for calculating a change amount during which the measurement error caused by the measurement spherical mirror is changed a plurality of times based on a measurement value obtained by performing the plurality of times, and a calculation amount calculated in the calculation step. When measuring the transmitted wavefront of the test object using And having a calibration step to calibrate the Hakachi.

  Further, the second calibration method according to the present invention is a measurement method for measuring the transmitted wavefront of the test object from interference fringes generated by interference between the test light transmitted through the test object and the reference light from the reference surface. A calibration method for calibrating a value, a measurement step of measuring interference fringes between light reflected by a calibration spherical mirror disposed in an optical path between the reference surface and a test object and the reference light, and Based on the measurement value obtained by executing the measurement step a plurality of times, a calculation step for calculating the amount of change that has occurred while the measurement error caused by the reference surface is executed a plurality of times, and the calculation step is calculated in the calculation step. And a calibration step of calibrating the measured value when measuring the transmitted wavefront of the test object using the amount of change.

  The first interference measurement apparatus according to the present invention is an interference measurement apparatus that measures a transmitted wavefront of a test object from interference fringes generated by interference between the test light transmitted through the test object and reference light, A reference surface that generates the reference light, a measuring spherical mirror that reflects the light transmitted through the test object as a first test light, and a second light that reflects the light transmitted through the test object. Measuring spherical surface mirror, measurement interference means for measuring interference fringes between the first test light and the reference light, and interference fringes between the second test light and the reference light And based on the measurement value obtained by executing the measurement by the measurement means a plurality of times, the amount of change that occurs while the measurement error caused by the spherical mirror for measurement is executed a plurality of times is calculated. Means for calibrating the measured value when measuring the transmitted wavefront of the test object using the measured change amount It is characterized in.

  The second interference measurement apparatus according to the present invention is an interference measurement apparatus that measures a transmitted wavefront of a test object from interference fringes generated by interference between the test light transmitted through the test object and the reference light, A reference spherical surface that generates the reference light, a calibration spherical mirror that is disposed in an optical path between the reference surface and the test object, and reflects the light from the reference surface to be test light, and the test A measurement error caused by the reference surface is executed a plurality of times based on a measurement unit that measures an interference fringe between light and the reference light, and a measurement value obtained by executing the measurement by the measurement unit a plurality of times. And a means for calibrating a measured value when the transmitted wavefront of the test object is measured using the calculated amount of change.

  According to the present invention, it is possible to shorten the time required for calibration of a system error included in the interference measuring apparatus.

Hereinafter, preferred embodiments of the present invention will be described based on the following examples.
[Example 1]
FIG. 1 is a schematic diagram of a main part of an interference measuring apparatus according to Embodiment 1 of the present invention. This interference measurement apparatus is disposed inside the chamber 20.
In FIG. 1, the light beam emitted from the light source 8 passes through the half mirror 9, passes through the mirror 10, and reaches the TS lens 3 (transmission type spherical lens) held on the XYZ stage 11. The XYZ stage 11 can be driven independently with respect to the three axes in the XYZ directions with high accuracy by a command from the computer 16.

On the XYZ stage 11, a TS lens 3 for generating a light beam having a desired NA is installed via a piezoelectric element (optical path length changing element) 12. A voltage can be applied to the piezoelectric element 12 from the computer 16, and when scanning the wavefront of the test object (test optical system) 1, fringe scanning (change in optical path length difference) synchronized with the CCD camera 15 is possible. ing.
Here, for the TS lens 3, the radius of curvature of the reference surface 3a that generates the reference light and the distance between the reference surface 3a and the focal point 13 are equal, and the reference surface 3a reflects light by about 5%. Hereinafter, the light reflected by the reference surface 3a of the TS lens 3 is referred to as reference light.

Adjustment in the optical axis direction is made by the XYZ stage 11 so that the focal point 13 of the TS lens 3 coincides with the object plane of the test object 1. The light beam transmitted through the test object 1 is collected on the image plane of the test object 1 and then reflected by an RS mirror (reflection spherical mirror) 2 which is a measuring spherical mirror. Hereinafter, the light reflected by the RS mirror is referred to as test light.
Here, like the TS lens 3, the RS mirror 2 is provided on an XYZ stage 18 that can be controlled by the computer 16, and at the time of measurement of transmitted wavefront aberration, the center of curvature of the RS mirror 2 and the image side focal point 19 coincide with each other. The direction has been adjusted.

  The reference light and the test light are combined by the TS lens 3 to form the same optical path, and are reflected by the half mirror 9 through the mirror 10. Then, the light reflected by the half mirror 9 forms interference fringes corresponding to the optical path length difference between the reference light and the test light on the CCD camera 15 as the measuring means via the pupil imaging lens 14 and the spatial filter 17. Form.

  The spatial filter 17 is installed on a conjugate plane with the focal point 13 of the TS lens 3 in the pupil imaging lens 14. The spatial filter 17 is used to shield a spatial frequency component higher than the Nyquist frequency caused by the pixel pitch of the CCD camera 15 and prevent so-called aliasing. Interference fringe image data captured by the CCD camera 15 is transferred to a computer 16 as a processing system.

  The computer 16 drives the piezoelectric element 12 to change the optical path length difference, thereby acquiring a plurality of interference fringe image data when the interference fringe is scanned, and calculating the phase (phase difference distribution) of the interference fringes. In calculating the phase from the interference fringes, a phase recovery algorithm for reducing error transmission such as stage vibration characteristics is used.

The obtained interference fringe phase distribution (measured value) includes the shape error (system error) of the RS mirror 2 and the TS lens 3. Therefore, using the system error measurement method such as the wavefront averaging method described above, the shape errors of the RS mirror 2 and the TS lens 3 are measured with high accuracy, and the measurement data is calibrated.
Thus, the procedure for measuring the interference fringe phase distribution (wavefront aberration) of the object 1 to be measured by the interference measuring apparatus is completed.

  The system error of the interference measuring apparatus may change due to environmental changes such as temperature and disturbances such as vibration. Therefore, conventionally, in order to guarantee the absolute value accuracy of a measured value in the long term, it is necessary to measure a system error that requires a long time each time as in the measurement method described above. Therefore, in this embodiment, in the second and subsequent measurements, the system error itself is not directly measured, but the change amount of the system error relative to the previous measurement is measured by using the calibration RS mirror.

First, common operations during each measurement will be described.
The XYZ stage 18 (first stage) is driven to move the transmitted wavefront measuring RS mirror 2 to the measurement position. Then, the first test light obtained by transmitting the light beam from the light source 8 to the test object 1 and reflected by the measurement RS mirror 2, and the reference light obtained by reflecting the reference surface 3 a of the TS lens 3 To obtain first measurement data (first measurement step). Since the first measurement data includes measurement data of the transmitted wavefront of the test object 1 and a system error, the transmitted wavefront of the test object 1 can be obtained except for the system error.

  Further, the XYZ stage 18 (first stage) is driven to move the calibration RS mirror (first calibration spherical mirror) 4 to the measurement position. Then, the second test light that is transmitted through the test object 1 and reflected by the calibration RS mirror 4 interferes with the reference light that is reflected by the reference surface 3a of the TS lens 3 to cause interference. 2 measurement data is obtained (second measurement step).

  Further, the third test light obtained by reflecting with a calibration RS mirror (second calibration spherical mirror) 6 disposed between the reference surface 3 a and the test object 1 and the TS lens 3 reference. Third measurement data is obtained by interfering with reference light obtained by reflection on the surface 3a. The XYZ stage 11 (second stage) moves the TS lens 3 (an optical system for guiding the light beam from the light source 8 to the second calibration spherical mirror) when obtaining the third measurement data. Note that the RS mirror 6 may be inserted into and retracted from the optical path of the measurement light without moving the second stage.

  When performing measurement and calibration of measurement values using the interference measurement apparatus shown in FIG. 1, first, the first measurement is performed, and the first measurement data (1-1) and the second measurement data (1) described above are performed. -2). Then, the second measurement is performed, and similarly, the first measurement data (2-1) and the second measurement data (2-2) described above are obtained. Based on the second measurement data (2-1, 2) and the first measurement data (1-1, 2), the change amount of the system error (measurement error) caused by the measurement RS mirror is calculated. measure. That is, the change amount of the system error is measured based on the two measurement data before and after.

  The same applies to the first measurement data and the third measurement data. For example, the first measurement is performed to obtain the first measurement data (1-1) and the third measurement data (1-3) described above. Then, the second measurement is performed, and similarly, the first measurement data (2-1) and the third measurement data (2-3) described above are obtained. Then, based on the second measurement data (2-1, 3) and the first measurement data (1-1, 3), the change amount of the system error (measurement error) caused by the reference surface 3a is measured. To do.

  The above is the basic operation of the portion according to this embodiment. In this embodiment, as shown in FIG. 1, two first calibration spherical mirrors are arranged on the measurement RS mirror 2 side (on the stage 18). ing. Therefore, it is possible to further obtain measurement data by causing the test light reflected by the second calibration RS mirror (first calibration spherical mirror) 5 to interfere with the reference light. Then, by using the measurement data for measuring the system error change amount in addition to the first and second measurement data described above, the absolute value of the system error can be obtained as compared with the case where there is one first calibration spherical mirror. The probability that measurement is unnecessary is increased. That is, the interference measurement apparatus may include a plurality of first calibration spherical mirrors, and the number of calibration RS mirrors (first calibration spherical mirrors) may be three or more.

Next, a system error calibration method using the transmitted wavefront measuring RS mirror 2 will be described in detail.
The XYZ stage 18 is driven so that the center of curvature and the image side focal point 19 of the transmitted wavefront measuring RS mirror 2 and the calibration RS mirrors 4 and 5 arranged on the XYZ stage 18 coincide with each other. Then, using the CCD camera 15 as measurement means, wavefront measurement is performed on each RS mirror. The transmitted wavefront of the test object 1 is W, the shape error of the TS lens 3 (reference surface 3a) is TS0, the shape error of the RS mirror 2 is RS0, and the shape errors of the calibration RS mirrors 4 and 5 are RS1 and RS2, respectively. . When the transmission wavefront measurement RS mirror 2 is used, the measurement result (first measurement data) is M0, and when the calibration RS mirror 4 is used, the measurement result is M1, and the calibration RS mirror 5 is used. Let M2 be the measurement result. This is expressed as follows.
M0 = W + TS0 + RS0
M1 = W + TS0 + RS1
M2 = W + TS0 + RS2

Then, the computer 16 performs the following processing using the above three results. First, each difference of M0 to M2 is taken to obtain respective difference data S1, S2, and S3.
S1 = M0−M1 = RS0−RS1
S2 = M0-M2 = RS0-RS2
S3 = M1-M2 = RS1-RS2
This completes the first measurement.

  In the second measurement, the same measurement as described above is performed to obtain M0 ', M1', and M2 '. Then, difference data S1 ', S2' and S3 'are obtained by taking the respective differences.

  Subsequently, using the data S1, S2, S3, S1 ′, S2 ′, S3 ′ obtained by the above measurement, the computer 16 calculates a change amount of the system error (determining whether the system error has changed). I do. This will be described with reference to FIG. However, this method is a very specific phenomenon (for example, when the RS mirrors 2, 4 and 5 undergo surface deformation, the same surface deformation occurs, and the amount of change in the shape errors RS0, RS1 and RS2 is the same. It is assumed that this does not happen.

  First, in the first step (STEP 1), S1 is compared with S1 '. When S1 and S1 ′ coincide, the surface shapes RS0 and RS1 of the RS mirrors 2 and 4 are not changed, that is, there is no change in system error due to the transmitted wavefront measuring RS mirror 2, and the measured values are calibrated. It is determined that the transmitted wavefront measurement of the test object 1 is possible without performing the above. On the other hand, in the case of disagreement, it corresponds to whether only RS0 is changing, only RS1 is changing, or both RS0 and RS1 are changing. In this case, since it cannot be determined whether the system error has changed due to the RS mirror 2, the process proceeds to the second step.

  In the second step (STEP 2), S2 and S2 'are compared. When S2 and S2 ′ coincide with each other, the surface shapes RS0 and RS2 of the RS mirrors 2 and 5 are not changed, that is, there is no change in the system error due to the RS mirror 2, and the measured values are not calibrated. It is determined that the transmitted wavefront measurement of the specimen 1 is possible. On the other hand, in the case of disagreement, only RS0 is changing, only RS2 is changing, or both RS0 and RS2 are changing. Also in this case, since it cannot be determined whether the system error has changed due to the RS mirror 2, the process proceeds to the next third step.

  In the third step (STEP 3), S3 and S3 'are compared. When S3 and S3 'match, it is considered that RS1 and RS2 are not changed and only RS0 (system error) is changed based on the results of the first and second steps. Therefore, (S1'-S1) or (S2'-S2) corresponds to the change amount of the system error (RS0). If the system error at the time of the first measurement is known, the system error at the time of the second measurement can be calculated by adding the obtained change amount of the system error to the known system error. it can. Therefore, by measuring only the change amount of the system error, the system error itself can be obtained without re-measurement. On the other hand, if S3 and S3 'do not match, it cannot be determined whether or not the system error has changed, and the system error itself cannot be obtained without re-measurement.

  This is the end of the description of the method for calibrating the system error (determining whether measurement is possible) by the RS mirror 2. In determining whether the difference data matches, the numerical values to be compared do not completely match, but even if they are slight differences, they may be handled as matching. For example, a numerical range that can be recognized as matching may be determined, and if the difference data is within the range, it may be treated as matching (same).

  In addition to comparison of the first and second measurement data, for example, comparison with the second and third measurement data and comparison of the first and third measurement data. The amount of change in system error can be obtained. That is, according to the present embodiment, the measurement when the transmitted wavefront measuring RS mirror 2 is used and the measurement when the calibration RS mirror is used are performed multiple times as one time. Then, based on each measurement value obtained by a plurality of executions, it is possible to obtain the amount of change that has occurred while the system error caused by the measuring spherical mirror is being executed a plurality of times.

  Next, a method for calibrating a system error (determining whether measurement is possible) using the TS lens 3 will be described. In this embodiment, as shown in FIG. 1, the number of calibration RS mirrors (second calibration spherical mirrors) arranged on the TS lens side (between the reference surface 3a and the test object 1) is the same as that of the RS mirror 6. However, the present invention is not limited to this. As in the case of the first calibration spherical mirror, the number of second calibration spherical mirrors may be one or more.

For the calibration RS mirrors 6 and 7 arranged outside the angle of view of the test object 1, the XYZ stage 11 is driven so that the respective centers of curvature coincide with the focal point 13 of the TS lens 3, and a CCD camera 15 is used. The wavefront measurement is performed on each RS mirror. The shape error of the TS lens 3 is TS0, the shape error of the RS mirrors 6 and 7 for calibration is RS3 and RS4, and the measurement result when the RS mirror 6 for calibration is M3 and the measurement result when the RS mirror 7 for calibration is used If the measurement result is M4, it can be shown as follows.
M3 = TS0 + RS3
M4 = TS0 + RS4
This completes the first measurement.

Next, even during the second measurement, the same measurement as described above is performed to obtain measurement values M3 ′ and M4 ′.
Subsequently, using the data M3, M4, M3 ′, and M4 ′ obtained by the measurement, the computer 16 calibrates the system error (determines whether measurement is possible). This will be described with reference to FIG. However, this method is a very specific phenomenon (for example, when the RS mirrors 6 and 7 undergo surface deformation, the same surface deformation occurs, and the amount of change in the shape errors RS3 and RS4 becomes the same). Is assumed not to occur.

  First, in the first step (STEP 1), M3 and M3 'are compared. When M3 and M3 ′ coincide with each other, the surface shapes TS0 and RS3 of the TS lens 3 and the RS mirror 6 are not changed, that is, there is no change in system error, and the test object is not calibrated. It is determined that 1 transmitted wave measurement is possible. On the other hand, in the case of mismatch, it corresponds to whether only TS0 has changed, only RS3 has changed, or both TS0 and RS3 have changed. In this case, since it cannot be determined whether or not the system error has changed due to the TS lens 3, the process proceeds to the second step.

  Subsequently, in the second step (STEP 2), M4 and M4 'are compared. When M4 and M4 ′ coincide with each other, the surface shapes TS0 and RS4 of the TS lens 3 and the RS mirror 7 are not changed, that is, the system error does not change, and the test object is not calibrated. It is determined that 1 transmitted wave measurement is possible. On the other hand, if they do not match, only TS0 is changed, only RS4 is changed, or both TS0 and RS4 are changed. Also in this case, since it cannot be determined whether or not the system error has changed, the process proceeds to the next third step.

  Subsequently, in the third step (STEP 3), (M3'-M3) and (M4'-M4) are compared. When (M3′−M3) and (M4′−M4) match, based on the results of the first and second steps, there is no change in RS3 and RS4, and only the TS lens 3 (system error) changes. It is possible that Therefore, (M3'-M3) or (M4'-M4) corresponds to the change amount of the system error (TS0). If the system error at the time of the first measurement is known, the system error at the time of the second measurement can be calculated by adding the obtained change amount of the system error to the known system error. it can. Therefore, by measuring only the change amount of the system error, the system error itself can be obtained without re-measurement. On the other hand, if (M3'-M3) and (M4'-M4) do not match, it cannot be determined whether or not the system error has changed, and the system error itself cannot be obtained without re-measurement.

  This is the end of the description of the method for calibrating the system error (determining whether measurement is possible) using the TS lens 3. In determining whether the data match, the numerical values to be compared do not match completely, but even if there is a slight difference, it may be handled that they match. For example, a numerical range that can be recognized as matching may be determined, and if the data is within the range, it may be treated as matching (same).

  In addition to comparison of the first and second measurement data, for example, comparison with the second and third measurement data and comparison of the first and third measurement data. The amount of change in system error can be obtained. In other words, according to the present embodiment, based on the measurement value obtained by performing the measurement when the calibration RS mirror is used a plurality of times, the system error caused by the reference surface is changed while the measurement is being performed a plurality of times. The amount of change can be determined.

  So far, the method of calibrating the system error with the RS mirror and TS lens has been described. When the above method is applied, the system error is measured by the RS mirror and the TS lens only at the first measurement, and only the change amount of the system error is measured after that. By these measurements, it is possible to determine whether or not the system error has changed, and to calculate the amount to be calibrated of the measured value when the system error has changed. Therefore, since it is not necessary to measure the system error itself every time the transmitted wavefront is measured, the measurement time of the transmitted wavefront can be shortened.

[Example 2]
A second embodiment of the present invention will be described with reference to the accompanying drawings.
FIG. 5 shows an exposure apparatus to which the interference measuring apparatus according to the first embodiment is applied. The projection optical system 23 in FIG. 5 corresponds to the test object 1. In this embodiment, it is possible to perform wavefront measurement using an exposure light source for exposing a mask pattern as an original to a wafer as a substrate.
At the time of wafer exposure, the light flux from the light source 8 is guided to the illumination optical system 29 by retracting the switching mirror 30, the mirror 31, and the TS lens 3. Thereby, the wafer held on the wafer chuck 26 can be exposed without blocking the light beam from the illumination optical system 29.

  Hereinafter, the wavefront measuring method will be briefly described. Since the exposure light source is usually incoherent light, the configuration of the interferometer in the present embodiment is shown as an example of a Twiman Green type. The light beam emitted from the light source (exposure light source) 8 is reflected by the switching mirror 30 and the mirror 31 and enters the beam expander 27. Thereafter, the light beam passes through the half mirror 32.

  Thereafter, the light beam is divided into a reference light beam and a test light beam by the half mirror 33. The reference light beam is reflected by the reference mirror 28 to become reference light, passes through the half mirror 33 again through the same optical path, is reflected by the half mirror 32, and then is vertically guided to the interference fringe measuring unit 24. On the other hand, the test light beam passes through the TS lens 3 and is guided to the projection optical system 23. The test light beam that has passed through the projection optical system 23 is reflected by the measurement RS mirror 2 placed on the wafer stage 25 to become test light, passes through the projection optical system 23 again, and then exits the TS lens 3. . The test light emitted from the TS lens 3 is reflected by the half mirror 32 and the half mirror 33 and is guided to the interference fringe measuring unit 24 to obtain interference fringes. A phase recovery algorithm is used to calculate the phase from the interference fringes.

The obtained interference fringe phase distribution (measured value) includes the shape error (system error) of the RS mirror 2 and the TS lens 3. Therefore, the system errors of the RS mirror 2 and the TS lens 3 are measured with high accuracy by using a system error measurement method such as the wavefront averaging method described above, and the measurement data is calibrated.
By the above method, the interference fringe phase distribution (wavefront aberration) of the projection optical system 23 can be measured.

  The system error of the RS mirror 2 and the TS lens 3 may change due to environmental changes such as temperature and disturbances such as vibration. Therefore, in order to guarantee the absolute value accuracy of the measured value in the long term, it is necessary to measure a system error that requires a long time each time as in the conventional transmitted wavefront measuring method described above.

  Therefore, in this embodiment, in accordance with the system error calibration method described in the first embodiment, the second and subsequent measurements using the measurement unit 24 and a computer (not shown) do not directly measure the system error itself. Only the amount of change is measured. For example, by using the calibration RS mirrors 4 and 5 mounted on the wafer stage 25 and the calibration RS mirrors 6 and 7 arranged outside the angle of view on the projection optical system 23, the system error changes from the previous measurement. Is detected.

  If the above method is applied and the system error measurement of the RS mirror and TS lens is performed only at the first measurement, the subsequent measurement checks whether there is a change in the system error without measuring the system error every time. can do. That is, the measurement time can be shortened.

[Example 3]
Next, an embodiment of a device manufacturing method using the above-described exposure apparatus will be described with reference to FIGS. FIG. 6 is a flowchart for explaining how to fabricate devices (ie, semiconductor chips such as IC and LSI, LCDs, CCDs, and the like). Here, a semiconductor chip manufacturing method will be described as an example.
In step 1 (circuit design), a semiconductor device circuit is designed. In step 2 (mask production), a mask (also called a reticle) is produced based on the designed circuit pattern. In step 3 (wafer manufacture), a wafer (also referred to as a substrate) is manufactured using a material such as silicon. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed on the wafer using the mask and the wafer by the above exposure apparatus using the lithography technique. Step 5 (assembly) is referred to as a post-process, and is a process for forming a semiconductor chip using the wafer produced in step 4. including. In step 6 (inspection), the semiconductor device manufactured in step 5 undergoes inspections such as an operation confirmation test and a durability test. Through these steps, a semiconductor device is completed and shipped (step 7).

  FIG. 7 is a detailed flowchart of the wafer process in Step 4. In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), an electrode is formed on the wafer by vapor deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied to the wafer. Step 16 (exposure) uses the exposure apparatus to expose a circuit pattern on the mask onto the wafer. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are removed. In step 19 (resist stripping), the resist that has become unnecessary after the etching is removed. By repeatedly performing these steps, multiple circuit patterns are formed on the wafer.

It is a figure which shows the structure of the interference measuring device which concerns on Example 1 of this invention. It is explanatory drawing of the system error measurement method of the TS lens which concerns on a prior art. It is a figure which shows the stability confirmation and system error recalculation flow which concern on RS mirror for measurement in the apparatus of FIG. It is a figure which shows the stability confirmation and system error recalculation flow which concern on the TS lens in the apparatus of FIG. It is a figure which shows the structure of the exposure apparatus which concerns on Example 2 of this invention. It is a flowchart for demonstrating manufacture of the device using an exposure apparatus. It is a detailed flowchart of the wafer process of step 4 in the flowchart shown in FIG.

Explanation of symbols

1 Object 2 RS mirror for measurement (spherical mirror for measurement)
3 TS lens 3a Reference surface of TS lens 4 RS mirror for calibration (first calibration spherical mirror)
5 RS mirror for calibration (first calibration spherical mirror)
6 RS mirror for calibration (second calibration spherical mirror)
7 RS mirror for calibration (second calibration spherical mirror)
8 Light source 14 Pupil imaging lens 15 CCD camera 16 Control computer 23 Projection optical system 24 Interference fringe measuring unit 28 Reference mirror (reference surface)
29 Illumination optics

Claims (11)

A calibration method for calibrating a measurement value when measuring a transmitted wavefront of the test object from interference fringes generated by interference between the test light transmitted through the test object and reference light,
A first measurement step of measuring an interference fringe between the light transmitted through the test object and reflected by the measurement spherical mirror of the transmitted wavefront and the reference light;
A second measuring step of measuring an interference fringe between the light transmitted through the test object and reflected by the calibration spherical mirror and the reference light;
While the measurement error caused by the measurement spherical mirror is executed a plurality of times based on the measurement value obtained by executing the first measurement step and the second measurement step a plurality of times as one time A calculation step for calculating the amount of change,
And a calibration step of calibrating a measurement value when measuring the transmitted wavefront of the test object using the amount of change calculated in the calculation step.   In the calculation step, a difference between the measurement value obtained in the first measurement step and the measurement value obtained in the second measurement step at the same time is obtained, and each difference in the plurality of times is compared. The calibration method according to claim 1, wherein the amount of change is calculated.   The calibration method according to claim 1, wherein in the second measurement step, measurement is performed on the plurality of calibration spherical mirrors. A calibration method for calibrating a measurement value when measuring the transmitted wavefront of the test object from interference fringes generated by interference between the test light transmitted through the test object and the reference light from the reference surface,
A measuring step of measuring interference fringes between the light reflected by the calibration spherical mirror disposed in the optical path between the reference surface and the test object and the reference light;
Based on the measurement value obtained by executing the measurement step a plurality of times, a calculation step for calculating the amount of change that has occurred while the measurement error caused by the reference surface is executed a plurality of times;
And a calibration step of calibrating a measurement value when measuring the transmitted wavefront of the test object using the amount of change calculated in the calculation step.   5. The calibration method according to claim 4, wherein in the measurement step, measurement is performed on a plurality of the calibration spherical mirrors. An interference measurement device that measures a transmitted wavefront of a test object from interference fringes generated by interference between the test light transmitted through the test object and the reference light,
A reference surface for generating the reference light;
A measuring spherical mirror that reflects light transmitted through the test object to form first test light;
A calibration spherical mirror that reflects the light transmitted through the test object to form a second test light;
Measuring means for measuring interference fringes between the first test light and the reference light, and interference fringes between the second test light and the reference light;
Based on the measurement value obtained by performing the measurement by the measurement means a plurality of times, the amount of change that occurs while the measurement error caused by the spherical mirror for measurement is performed a plurality of times is calculated, and the calculated change Means for calibrating a measured value when measuring a transmitted wavefront of the test object using a quantity.   The interference measuring apparatus according to claim 6, comprising a plurality of calibration spherical mirrors. An interference measurement device that measures a transmitted wavefront of a test object from interference fringes generated by interference between the test light transmitted through the test object and the reference light,
A reference surface for generating the reference light;
A calibration spherical mirror that is arranged in an optical path between the reference surface and the test object and reflects light from the reference surface to be test light, and interference fringes between the test light and the reference light. Measuring means for measuring;
Based on the measurement value obtained by performing the measurement by the measurement unit a plurality of times, the amount of change that occurs while the measurement error caused by the reference surface is performed a plurality of times is calculated, and the calculated change amount is calculated. And a means for calibrating a measured value when the transmitted wavefront of the test object is measured.   The interference measurement apparatus according to claim 8, comprising a plurality of calibration spherical mirrors.   An exposure apparatus comprising: a projection optical system as the test object; and the interference measurement apparatus according to any one of claims 6 to 9.   11. A device manufacturing method comprising: exposing a substrate using the exposure apparatus according to claim 10; and developing the exposed substrate.

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