JPH1116821A - Apparatus and method for x-ray exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable highly-accurate exposure correction against variation in radiated light intensity, by measuring the radiated light intensity a plurality of times, calculating the radiated light intensity during exposure from the result of the measurement, calculating exposure time from the calculated value, and performing exposure based on the calculated exposure time. SOLUTION: A beam current measuring section 11 regularly measures the beam current of a synchrotron ring 12 a plurality of times, and indirectly measures the intensity of radiated light a plurality of times. A beam current calculating section 14 obtains the calculated value of the beam current at the time of t, based on the result transmitted till the time of tc (t>tc). An exposure time calculating section 15 calculates a corrected intensity of radiated light, based on the transmitted calculated value, receives an exposure start time from an exposure control section 68, and calculates an exposure end time and then an exposure time. Finally, the exposure control section 68 closes an X-ray shutter or the like using the received exposure end time, and thereby terminates exposure on a semiconductor wafer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an exposure apparatus and an exposure method using X-rays, and more particularly to an X-ray exposure apparatus and an X-ray exposure method using synchrotron radiation (SOR light).

[0002]

2. Description of the Related Art As the degree of integration of a semiconductor device increases, the circuit pattern of an LSI element constituting the semiconductor device has been further miniaturized. In order to make the pattern finer, not only the line width is reduced, but also the dimensional accuracy and positional accuracy of the pattern are required to be improved. Many technologies have been developed to meet these demands. Among them, the exposure technology using X-ray is regarded as promising as the next generation technology of the exposure technology using ultraviolet rays currently used. ing. As an X-ray exposure apparatus currently under development, an apparatus using synchrotron radiation (SOR light) is typical.

[0003] Synchrotron radiation is emitted in the tangential direction of an orbit when electrons accelerated to high energy have their orbits bent in an arc shape by a magnetic field. As a result, the synchrotron radiation spreads in a band in the plane of the electron orbit (synchrotron ring). On the other hand, the electron energy is several hundred MeV to 1 GeV (used in lithography)
In this case, the radiated light has a spread of only about 2 mrad in each tangential direction, and has the property of extremely good directivity.
This excellent directivity is an extremely excellent property in performing proximity exposure. In this proximity exposure using synchrotron radiation, an X-ray mask and a semiconductor wafer are arranged to face each other in a direction substantially perpendicular to the plane of the synchrotron ring.
A so-called step-and-scan method in which a strip-shaped synchrotron radiation beam is scanned up and down on the X-ray mask to sequentially transfer and transfer the entire pattern area on the X-ray mask onto a semiconductor wafer.
The repeat method is common. Scanning of synchrotron radiation starts from the emission point on the synchrotron ring to the exposure chamber (stepper section).
This is done by rotating an extreme oblique incidence reflection mirror or the like placed in a beam line connecting the two. The beam line is evacuated to a vacuum by a vacuum pump. A Be thin film is provided between an exposure chamber in which an X-ray mask or a semiconductor wafer is arranged and the beam line to form a vacuum partition. The amount of X-ray exposure in the X-ray exposure apparatus is determined by measuring the beam current of the synchrotron ring and determining the required exposure time from the correspondence between the result and the previously calibrated exposure per unit time. After the calculation, the shutter and the like are driven to control the exposure amount. In order to improve the dimensional accuracy of the pattern, it is very important to control the amount of exposure.
In order to obtain a 1 μm pattern with an accuracy of ± 7%, it is necessary to control the exposure amount to about ± 3% over the entire surface of a plurality of exposure regions sequentially exposed on the substrate to be exposed, including the unevenness of the exposure amount. . In the currently known technology, the uniformity in the exposure area immediately before the beam passes through the beam line and enters the exposure chamber due to the deterioration of the reflecting mirror or the Be thin film in the beam line is ±
It is common to degrade to 2-3%.

In order to realize a high-precision pattern by X-ray exposure, it is necessary to eliminate unevenness in exposure amount and control the exposure amount to a desired range. For this purpose, the fluctuation of the beam current and the fluctuation of the exposure amount caused by the measurement error of the beam current are controlled to at least 1% or less, and the exposure amount control of about ± 3% is secured as a whole over the entire surface of the substrate to be exposed. There is a need.

[0005]

However, the beam current of the synchrotron ring may suddenly decrease, and usually attenuates exponentially. Therefore, a difference occurs between the beam current at the time of setting the exposure amount and the beam current at the time of actually performing the exposure, and as a result, the control of the exposure amount may not be within 1%. There is a problem. Similar problems are not only related to beam current, but also, for example,
This also applies to the concentration of impurities such as oxygen contained in He filled in the optical path of the R light. As described above, the beam line is usually evacuated to vacuum, the Be thin film constitutes a vacuum partition, and the exposure chamber is filled with He. Therefore, in the optical path of the SOR light, there is a space filled with He in order to prevent the Be thin film and the SOR light from attenuating. This He
If the impurity concentration in the medium changes between the time when the exposure is set and the time when the exposure is actually performed, similarly, the case where the control of the exposure does not fall within 1% occurs. For example, according to a simple calculation, the optical path length passing through He is 50 at one atmosphere.
cm, a change in oxygen concentration of at most about 50 ppm causes a change in exposure of 1%. Further, it is necessary to consider the fluctuation of the exposure amount due to the deterioration of the Be thin film arranged in the posture of blocking the optical path.

When such a monotonous change in the intensity of the SOR light occurs, in order to secure the measurement accuracy of various parameters such as the beam current, the measurement is repeated for a long time, and the average value is used as the measured value. Has been attempted. However, this method also has a problem that a difference between the measured value and the actual exposure amount occurs.

As described above, when the parameter affecting the SOR light intensity changes between the time when the exposure amount is set and the time when the actual exposure is performed, accurate control of the exposure amount cannot be performed. There is a problem that. Even if the change is monotonic, it is difficult to accurately control the exposure amount. However, in the case of a nonmonotonic change including a sudden change, even if the result of a long-time repeated measurement is used, it is no longer useful. However, there is a problem that accurate control of the exposure amount cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide an X-ray exposure apparatus capable of correcting an exposure amount with a high degree of accuracy in response to a change in the intensity of radiation of a synchrotron ring that is constantly changing.

Another object of the present invention is to provide a quick and appropriate method such as resetting the exposure amount or stopping exposure even when a non-monotonic change in X-ray intensity occurs due to a sudden change in the beam current of the synchrotron ring. An object of the present invention is to provide an X-ray exposure apparatus capable of surely responding.

[0010] Still another object of the present invention is to provide synchrotron radiation (SOR).
An object of the present invention is to provide an X-ray exposure apparatus capable of promptly and accurately coping with a change in other parameters other than a change in a beam current of a synchrotron ring which causes a change in light intensity of light.

Still another object of the present invention is to provide an X-ray exposure method which realizes accurate lithography by performing high-precision exposure correction for a change in a beam current of a synchrotron ring which is constantly changing. That is.

Still another object of the present invention is to provide a method for quickly setting an exposure amount or stopping exposure even for non-monotonic X-ray intensity changes caused by sudden synchrotron ring beam current changes. An object of the present invention is to provide a highly accurate and highly reliable X-ray exposure method capable of taking appropriate measures.

Still another object of the present invention is to provide an X-ray capable of promptly and accurately coping with a change in other parameters which cause a change in light intensity of radiation (SOR light) from a synchrotron ring. It is to provide an exposure method. For example, it is an object of the present invention to improve the lithography accuracy and reliability by enabling sufficient and accurate exposure amount correction even for a change in the impurity concentration in the gas in the optical path of the SOR light.

[0014]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention is directed to an exposure apparatus using radiation (SOR light) emitted from a synchrotron ring as an exposure light source, wherein the intensity of the radiation is directly or indirectly measured. Measuring means for measuring a plurality of times, an intensity calculating means for calculating a radiation light intensity (X-ray intensity) at the time of exposure based on a measurement result by the measuring means, and a time calculating for calculating an exposure time based on the calculated value. A first feature is that the apparatus is an X-ray exposure apparatus including means and exposure control means for performing exposure based on the calculated exposure time.
"Direct measurement" of synchrotron radiation intensity means measurement by X-ray detector, etc., and "indirect measurement" means measurement by indirect means such as measurement of beam current of synchrotron ring. I do.

According to a first aspect of the invention, even if the beam current of the synchrotron ring changes with time,
It is possible to accurately identify at what time during the exposure time the change in the beam current, that is, the change in the X-ray intensity has occurred. Therefore, it is possible to perform effective correction for a change in the light intensity of the SOR light corresponding to a change in the beam current of the synchrotron ring with sufficient accuracy. By correcting the exposure time in response to the abnormality of the beam current, it is possible to remedy the problem caused by the fluctuation of the intensity of the exposure light.
This enables accurate X-ray lithography of a super LSI having a fine pattern of sub-quarter micron or less, so that the product yield of the super LSI can be improved and the productivity can be improved.

The calculating means for calculating the intensity of the emitted light (X-ray intensity) uses an arithmetic device such as a microprocessor configured to approximate / extrapolate an exponential function based on a plurality of measurement data. I just need. Preferably, a storage unit may be added to the calculation unit, and the calculated value may be stored in the storage unit. If the calculated value is stored in the storage means, a discontinuous change in the X-ray intensity occurs during exposure, and even if the difference between the actual X-ray intensity and the calculated value becomes large, quick processing can be performed in real time. . For example, a predetermined comparator is further provided, the stored calculated value is compared with the actually measured X-ray intensity, and the X-ray intensity at the time of exposure is recalculated according to the output of the comparator, and the exposure time is corrected. If you give the process,
X-ray lithography with higher accuracy is possible. Also, if a menu is provided to stop exposure when the output of the comparator becomes larger than a certain value, the performance of a product having strict design specifications can be guaranteed.

The first feature of the present invention is that the change of the beam current of the synchrotron ring is not limited to the adjustment of the exposure amount, but the oxygen contained in the gas in the exposure chamber which affects the SOR light intensity. The change of the impurity concentration such as the above may be monitored. Further, changes in the reflectivity of the mirror, deterioration of the Be thin film, and the like can also be used as input data of the time calculation means. For example, a portion in which at least a part of the space between the light source and the substrate to be exposed is filled with a gas such as He gas, which has a lower absorptivity of exposure light than the standard atmosphere, constitutes an impurity concentration in this gas prior to exposure. And a concentration calculating means for calculating the impurity concentration in the gas at the time of exposure based on the measurement result of the impurity concentration measuring means. It may be added to the input data of the time calculating means. The gas having a low absorptance may be filled in at least a portion between the light source and the substrate to be exposed by a configuration in which the gas has a small absorption rate, a configuration in which the gas is circulated at a constant flow rate, or the like. By adding a storage unit to the density calculation unit and comparing the calculated value and the measured value with a predetermined comparator, it is possible to quickly respond to a change in the light intensity of the SOR light during exposure. That is, processing such as recalculation of the exposure time and stop of the exposure can be performed in accordance with the output of the comparator, so that lithography accuracy can be ensured and the reliability of the product can be improved.

A second feature of the present invention is an exposure method using radiation (SOR light) from a synchrotron ring as an exposure light source, wherein the intensity of the radiation is measured a plurality of times directly or indirectly prior to exposure. Calculating an emission light intensity at the time of exposure based on the measurement result; calculating an exposure time of SOR light required at the time of exposure based on the calculated value; Exposing a substrate to be exposed such as a semiconductor wafer with SOR light based on time.
The most typical indirect measurement of the emitted light intensity is the measurement of the beam current of the synchrotron ring.

According to the second feature of the present invention, even if the beam current of the synchrotron ring changes every moment, it is possible to control the exposure time corresponding to the change of the beam current with sufficient accuracy. In the calculation of the beam current according to the second aspect of the present invention, it is preferable to perform approximation and extrapolation of a plurality of data points to an exponential function based on the results of the plurality of measurements. In particular, if the calculated beam current is stored and compared with the actually measured beam current, the exposure time can be recalculated even for abnormalities such as a sudden change in the beam current during exposure, Processing such as exposure stop can be performed.

In the second aspect of the present invention, the SO
As for other factors that affect the fluctuation of the light intensity of the R light, a plurality of data may be obtained every moment and used as input data for calculating the exposure time. For example, the impurity concentration in a predetermined gas such as He gas filled in a part of the optical path of the SOR light may be measured a plurality of times and added to the input data for calculating the exposure time. Also in this case, by storing the measured impurity concentration and comparing the measured impurity concentration with the actually measured value in real time, it is possible to quickly and appropriately respond to a sudden change in the SOR light.

[0021]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic view of an X-ray exposure apparatus according to an embodiment of the present invention as viewed from above. As shown in FIG. 1, an X-ray exposure apparatus according to an embodiment of the present invention includes a synchrotron ring (storage ring) 12 for emitting synchrotron radiation light (SOR light) as a light source, and a synchrotron ring. The exposure chamber 19 connected to the ring via the beam line 31 is a main component. Inside the exposure chamber 19, an X-ray mask, a semiconductor wafer, a holding device for holding these, an alignment optical system, and the like are arranged. Further, an exposure time control means such as an X-ray shutter and a semiconductor wafer are moved inside the exposure chamber 19.
An exposure controller 68 having a drive mechanism for replacement is provided. The beam line 31 includes a reflection mirror that scans X-rays, a holding unit for the reflection mirror, and a driving unit. A beam current measuring unit 11 serving as a “measuring unit” of the present invention is disposed so as to surround the electron beam orbit in the synchrotron ring 12, and the beam current measuring unit 11 includes a beam current calculating unit 14 having a storage area 14 a. Is connected. The beam current calculator 14 corresponds to a part of “intensity calculator for calculating the intensity of emitted light” of the present invention. The exposure chamber 19 further includes an oxygen concentration measuring unit 16, and the oxygen concentration measuring unit 16 has an oxygen concentration calculating unit 17 having a storage area 17 a.
It is connected to the. The outputs of the beam current calculator 14 and the oxygen concentration calculator 17 are connected to an exposure time calculator 15. The exposure time calculator includes another part of the “intensity calculator for calculating the intensity of the emitted light” of the present invention and a “time calculator”. The exposure time calculator 15 is connected to the exposure controller 68. The exposure controller 68 controls the exposure time by exposure time control means such as a shutter. Exposure controller 6
The "exposure control means" of the present invention is constituted by 8 and the exposure time control means.

FIG. 2 is a flowchart showing an X-ray exposure method according to the embodiment of the present invention. In the following Figure 1
The flowchart of FIG. 2 will be described with reference to FIG. 4 and FIG.

(1) The beam current measuring unit 11 periodically measures the beam current of the synchrotron ring 12 a plurality of times, and indirectly measures the intensity of the emitted light (SOR light) a plurality of times (step S201). . Then, the result is sent to the beam current calculator 14.

(2) Next, as shown in FIG. 4A, the beam current calculation unit 14 performs curve fitting based on the result sent up to time t _c , and at time t (t> t _c ). A calculation value _Ie (t) of the beam current is obtained (step S202). Then, the result is sent to the exposure time calculation unit 15.

(3) The exposure time calculator 15 corrects the radiated light intensity (SOR) based on the calculated value I _e (t) sent.
(Light intensity) S _e (t) is calculated. Exposure time calculator 1 at the same time
5 receives the exposure start time t _i from the exposure control unit 68 and sets the exposure end time t _f so that the integrated exposure amount indicated as the area of the hatched portion in FIG. 3C matches a predetermined value. Is calculated, and the exposure time is calculated (step S203). And it sends the exposure end time t _f in the exposure control unit 68.

[0026] (4) Finally, the exposure control unit 68, to terminate the exposure on the semiconductor wafer by closing the X-ray shutter or the like by using an exposure end time t _f received (step S204). Then, the wafer is sequentially translated into the next exposure area or converted into the next wafer by using a wafer stage driving unit or the like, and the next exposure process is prepared.

The above is the outline of the flowchart shown in FIG. The beam current calculation unit 14 may calculate the emitted light intensity S _e (t), and transmit the result to the exposure time calculation unit 15. Further, in the embodiment of the present invention, step 202 is performed as shown in the flowchart of FIG.
At the same time, it is preferable to measure the oxygen concentration. That is, the oxygen concentration in the He atmosphere in the exposure chamber 19 is periodically measured using the oxygen concentration measurement unit 16 provided in the exposure chamber 19 (Step S221), and the result is sent to the oxygen concentration calculation unit 17. . The oxygen concentration calculation unit 17 performs curve fitting as shown in FIG. 4B based on the transmitted result, obtains a calculated value Pο _e (t) of the oxygen concentration at time t (step S222), and exposes the result to exposure. Time calculator 15
Send to In step 203, the exposure time calculation unit 1
Calculated value sent 5 with I _e (t) and Pomikuron _e (t) to the original, to calculate the corrected SOR light intensity S _e (t).
At the same time, the exposure start time t _i is received from the exposure control unit 68 as described above, and the exposure end time t _f is set so that the integrated exposure amount indicated by the hatched portion in FIG. Is calculated. Subsequent step S204 is as described above.

In the embodiment of the present invention, it is more preferable to calculate the exposure time as follows.

That is, the beam current calculation unit 14 stores the calculated value I _e (t) of the beam current in the storage area 14a, and at the time of actual exposure, the measured value I _e (t) of the beam current during exposure.
_o (t) and I _e (t) are compared. As a result of the comparison, if the difference exceeds a range set in advance in consideration of an error or the like, the calculation of the beam current is newly performed, and a new calculation value I _e ′ (t) is transmitted to the exposure time calculation unit 15. . On the other hand, also in the oxygen concentration calculating section 17, the oxygen concentration calculated value Pο _e (t) is stored in the storage area 7a. The fact of the time of exposure to compare measurements Pomikuron _o of the oxygen concentration in the exposure (t) and Pomikuron _e (t), if the difference exceeds a range set in advance in consideration of an error, etc. , The calculation of the oxygen concentration is newly performed, and the new calculated value Pο _e ′ (t) is
Send to 5. Exposure time calculation section 15, the newly sent calculated value I _e a '(t) and Pο _e' (t) to the original, the new SO
The R light intensity S _e ′ (t) is calculated, and the exposure end time t is corrected based on this value so that the integrated exposure amount matches a predetermined value.
_f ′ is calculated, and the corrected value is sent to the exposure controller 68.
The exposure control unit 68 ends the exposure at the newly received exposure end time t _f ′ by closing the shutter or the like.
Then, the wafer is moved in parallel to the next exposure area or replaced with the next wafer by a wafer stage driving unit or the like, and the next exposure process is started. This method uses the beam current measurement unit 11
Is small and the measurement interval of the beam current is short. That is, in such a case, it is possible to accurately identify at which time during the exposure time the change in the beam current has occurred, so that the effective correction for the change in the beam current can be performed with sufficient accuracy. It is possible to do. Therefore, in response to the abnormal beam current,
By correcting the exposure time, fluctuations in X-ray intensity can be compensated or problems caused by the fluctuations can be remedied to improve the yield of products (LSI) and improve productivity.

In the embodiment of the present invention, the beam current calculator 14 stores the calculated value I _e (t) of the beam current (or the calculated value S _e (t) of the emitted light intensity) in the storage area 14a. On the other hand, at the time of actual exposure, a comparison between the measured values I _o (t) and I _e (t) of the beam current during exposure (or a comparison between the light intensity S _o (t) and S _e (t) during exposure) ) Is preferably performed.
If the difference exceeds a preset range in consideration of an error or the like, the fact that there is an error in the exposure amount setting is notified to the exposure control unit 18 via the exposure time calculation unit 15 and the exposure control unit 68 It is preferable to perform a preset process. Here, the "predetermined process" refers to a predetermined process such as interrupting the exposure of the chip or omitting the remaining exposure of the entire semiconductor wafer and sending it to a reprocessing step. Similarly, the oxygen concentration calculation unit 17 stores the calculated oxygen concentration Pο _e (t) in the storage area 17a, while measuring the oxygen concentration P _{o o} (t) and P _o during exposure during actual exposure. _e (t) is compared, and if the difference exceeds a predetermined range in consideration of errors and the like, the exposure control unit 68 via the exposure time calculation unit 15 has an error in the exposure amount setting. The exposure control unit 68
It is preferable to perform the above-described “preset processing”. This has an advantageous effect that it is possible to specify in advance a chip having a problem in the wafer. Alternatively, there is an advantage that the re-exposure processing can be performed without spending unnecessary exposure time. This method is effective when the time constant of the beam current measurement unit 11 is large or when the measurement interval of the beam current is long. Because, in such a case, it is basically difficult to accurately identify from which time during the exposure time the beam current has changed and the X-ray intensity has changed, and the accuracy required for effective correction is difficult. Because it is difficult to do it. Therefore, it is more realistic to perform “predetermined treatment” for the abnormality at the stage when the abnormality of the beam current is detected, and the productivity is excellent.

FIG. 7 is a schematic diagram showing in detail the reflection mirror 20 and the like in the beam line 31 not shown in FIG. 1, and is a view as seen from a lateral direction orthogonal to FIG. Synchrotron ring 12 and beamline 3 used in the present invention
No. 1 has the same basic configuration as that conventionally used. As shown in FIG. 7, in the synchrotron ring 12, electrons having an energy of 600 MeV circulate, and the radius of curvature of the curved portion is 0.66 m. The SOR light radiated from this is a beam line 31 evacuated to a vacuum.
After being reflected by the reflection mirror 20 in the inside, it passes through a 20 μm-thick Be thin film 21 serving as a vacuum partition wall, and passes through one atmosphere of H.
e is introduced into the exposure chamber 19 filled with e. The SOR light is white light having a spectrum having a peak at about 1 nm on a substrate to be exposed such as a semiconductor wafer. The reflection mirror 20 performs an oscillating motion by a mirror driving unit 22. Mirror drive unit 2
The operation of 2 is controlled by the mirror controller 23 linked to the exposure controller 68 in the exposure chamber 19. To control the exposure time, an exposure time control means 67 such as a shutter
Is controlled and performed. Further, in the exposure chamber 19, a wafer stage 41 holding a substrate to be exposed such as a semiconductor wafer,
A mask stage 51 holding an X-ray mask is arranged to face. The wafer stage 41 is driven by a wafer stage drive unit 42, and the mask stage 51 is driven by a mask stage drive unit 52. The exposure control unit 6
8 is controlled. Further, He in the exposure chamber 19 is connected to the He circulation refining unit 24, so that a decrease in the purity of He in the exposure chamber 9 serving as a stepper unit is suppressed to some extent. An X-ray intensity distribution control means 71 is arranged in the beam line 31 in order to improve X-ray intensity unevenness. The X-ray intensity distribution control means 71 is connected to the X-ray intensity distribution control means control section 72. The X-ray intensity distribution control means 71 may be omitted.

The embodiment of the present invention will be described on the assumption that the beam current in the synchrotron ring 12 changes as shown in FIG. The beam current measurement unit 11 shown in FIG. 1 performs measurement every 3 seconds irrespective of whether exposure is performed or not, and outputs the result to the beam current calculation unit 1.
4 sequentially. Than 40 times results including the time t _c as shown in the beam current calculation unit 14 FIG. 5 (a), the performing fitting an exponential function approximation. The calculated value I _e (t) of the beam current is obtained by this fitting, and the result is sent to the exposure time calculation unit 15 and stored in the storage area 4a. Since the accuracy of I _e (t) reflects the results of the measurement for 40 times, it is possible to reduce the error depending on the variation of the measurement as compared with the case where it is determined by a single measurement, and to further reduce the variation. Can reflect trends. According to this method, the fitting result can be accurately obtained even when a measuring instrument having a large time constant is used. Normally, a measurement with a large time constant results in higher accuracy, so that the present invention can use a measurement device with higher accuracy. Therefore, according to the present invention, higher precision can be achieved. To explain with actual data, the difference between _Ie (t) obtained in this way and the actually measured beam current _Io (t) is less than 0.5% in an integrated amount over 15 minutes. , The calculated value I _e (t) and the actually measured value I _o (t) were in good agreement. on the other hand,
Based only on a single measurement value at time t _c, if you estimate the corresponding beam current I _e (t) to the exposure time, if the error between the measured value I _o (t) becomes 1% or more Was found. That is, when the time constant is small (τ ₁ ), as shown in FIG.
Although it is possible to bring the measurement time t _c1 closer to the exposure start time t _i , the measurement is originally inaccurate, so that the actual current values I _o and 1 are already at the exposure start time t _{i with} a certain probability. % Or more. This difference spreads over time. On the other hand, since the time constant is large (τ ₂ ),
Since the measurement result t _e2 of the accurate measurement results in the measurement time t _c2 being separated from the measurement start time t _i , the difference in the amount already existing at the exposure start time t _i is different from the actual current value I _o (t). Exists between Therefore, even if the accuracy is high at a specific time, the actual current value I _o (t) at the actual measurement start time t _i is not approximated, and the calculated value I _e2 and the actually measured value I _o (t) Because the difference increases as time passes,
A difference of 1% or more occurs.

The exposure time calculator 15 calculates the SOR light intensity based on I _e (t) sent from the beam current calculator 14 and Pο _e (t) sent from the oxygen concentration calculator 17. Obtained by the formula

[0034]

S _e (t) = A × I _e (t) × exp (−B × Po _e (t)) (1) where A and B are coefficients determined in advance from the exposure result.

The exposure time calculator 15 receives the exposure start time t _i from the exposure controller 68, and calculates the exposure end time t _f so that the integrated intensity becomes a specified exposure amount, for example, 170 mJ / cm ^2. Then, it is sent to the exposure control unit 68. The exposure controller 68 controls the exposure time by opening and closing the shutter 67. Note that the calculation of the SOR light intensity S _e (t) does not necessarily have to be performed in each exposure, and it is often necessary to repeat only the calculation of the integrated intensity based on a request from the exposure control unit 68.

When a non-monotonic change as shown in FIG. 6A is observed in the beam current during exposure, the beam current calculator 14 calculates I _e (t) stored in the storage area 14a as follows:
It is determined that there is a significant difference in the measured value I _o (t), and the new calculated value I _e ′ (t) is sent to the exposure time calculator 15. In particular,
It is preferable to set this function to operate when a difference of 1% or more between I _e (t) and I _o (t) is detected. The exposure time calculator 15 calculates the
As shown in (b), as the area of the shaded area is equal to changing the exposure end time in response to exposure to a shortage t _f 'than t _f. However, according to the time constant of the measuring instrument and the measurement interval (τ, 3 seconds in this example), it is possible to identify at which point in the period the change in the beam current has occurred as shown in FIG. Since the result has an uncertainty of about τ, FIG.
The setting error of the exposure amount corresponding to the hatched portion in (c) is inevitable. For this reason, for example, when τ is large and this error becomes a size that cannot be ignored, rather than correcting the exposure time, based on a preset menu,
It is desirable to take measures such as stopping the exposure. Actually, as described above, since the exposure amount is required to have a high accuracy of 1% or less, the exposure amount corresponding to the hatched portion in FIG. 6C exceeds 1% of the total exposure amount. It is desirable to perform processing based on this menu. More specifically, it is necessary to consider a decrease in the accuracy of the exposure amount due to other factors, and if the above value is about 0.5 to 0.7%, taking into account other factors, It is more desirable to perform processing based on this menu.

In the menu, 1) a warning is issued, a portion where an error has occurred is displayed, and exposure is continued.

2) A warning is issued, a portion where an error has occurred is displayed, exposure of that portion is stopped, and the remaining exposure is continued.

3) A warning is issued, exposure is interrupted, and the operator waits for a response.

4) A warning is issued and the exposure of the wafer is stopped.

Such items may be prepared. This makes it possible to select an appropriate response according to the characteristics of the wafer being processed. For example, in the case of a lot requiring strict size control, exposure of the remaining portion of the wafer is stopped when an error occurs. Then, it is desirable that the resist is stripped, the substrate is pre-processed, the resist is re-coated, and the transfer is performed again. However, in this case, a decrease in throughput must be accepted. In the case where it is necessary to give priority to the processing amount even if there is a slight decrease in dimensional accuracy in consideration of the throughput, a process in which exposure is continued as it is is selected. In this case, it is effective to know in advance the places where the dimensional defects are likely to occur, at the time of confirming the dimensions after developing the resist or performing the sampling inspection. Therefore, it is preferable to provide a function of not only continuing the exposure but also displaying which part of the wafer has a problematic part. This display function can contribute to an improvement in productivity.

FIG. 8 is a schematic view showing an exposure chamber, a beam line, and the like of an X-ray exposure apparatus according to a modification of the embodiment of the present invention. The same parts as those in FIG. 7 are denoted by the same reference numerals. In FIG. 7, the exposure time control means (X-ray shutter) 67
Is arranged in the exposure chamber 19, but in the modification shown in FIG. 8, an exposure time control means 65 is arranged in the evacuated beam line 31. As the exposure time control means 65, a means for blocking an optical path such as an X-ray shutter or a means for shifting the optical axis by a reflecting mirror or the like may be used. The exposure time control unit 65 includes an exposure control unit 66
Is controlled by The exposure controller 66 is a mirror controller 23
And the X-ray mirror 20 and the exposure controller can be linked. Although the illustration of the connection relation is omitted, the exposure control unit 66 is connected to the wafer stage driving unit 42 and the mask stage driving unit 52, respectively, and the wafer stage 41 and the mask stage 51 are controlled by the exposure control unit 66. Therefore, after the end of the predetermined exposure time, the exposure control section 66 performs sequential translation of the substrate to be exposed (semiconductor wafer) and conversion of the substrate. Other parts are the same as those in FIG.

FIG. 9 is a view for explaining an X-ray exposure apparatus according to another modification of the present invention. 7 and 8 are denoted by the same reference numerals, and description thereof will be omitted. In FIG. 9, an X-ray detector 81 is arranged in the beam line 31 so that the intensity of light emitted from the synchrotron ring can be directly measured. That is, the emitted light intensity is directly measured a plurality of times, and a characteristic curve showing a change in the emitted light is obtained by fitting the measured data from the plurality of measurement data. The calculation of the radiation light intensity at the time of exposure by fitting is performed by the X-ray intensity calculation unit 82 which is the “intensity calculation means” of the present invention. The calculation result of the X-ray intensity calculation unit 82 is transmitted to the time calculation means for calculating the exposure time, and the exposure control means performs exposure based on the calculated exposure time.

As described above, the present invention can be realized by the indirect measurement of measuring the beam current of the synchrotron ring shown in FIGS. 7 and 8, and the direct measurement of the emitted light intensity shown in FIG. It can also be realized by a method.

Further, the present invention can be achieved not only by the beam current and the oxygen concentration in He but also by a method of monitoring the change in the reflectance of the mirror as long as it is a factor affecting the SOR light intensity. It is.

Further, the present invention provides a 1 × magnification using SOR light.
The present invention can be applied not only to line exposure but also to exposure using a reduction transfer system, and further to a transfer system using extreme ultraviolet using an insertion light source such as an undulator.

[0047]

As described above, according to the present invention, even when the parameter affecting the light intensity of the light source used for exposure changes between the time when the exposure amount is set and the time when the actual exposure is performed, an accurate exposure amount can be obtained. Control becomes possible, and the dimensional controllability of the pattern to be formed can be improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram schematically showing an X-ray exposure apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart schematically showing an X-ray exposure method using the X-ray exposure apparatus shown in FIG.

FIG. 3 is a flowchart showing an outline of a more preferable X-ray exposure method using the X-ray exposure apparatus shown in FIG.

FIG. 4 is a diagram illustrating calculation of SOR light intensity according to the embodiment of the present invention.

FIG. 5 is a diagram illustrating a relationship between a calculated value of a beam current and an actually measured value.

FIG. 6 is a diagram for explaining control of an exposure amount when a beam current changes during exposure.

FIG. 7 is a schematic diagram showing the exposure chamber, the beam line, and the vicinity thereof in the X-ray exposure apparatus according to the embodiment of the present invention in more detail.

FIG. 8 is a schematic diagram illustrating an exposure chamber, a beam line, and the like of an X-ray exposure apparatus according to a modification of the embodiment of the present invention.

FIG. 9 is a schematic diagram showing an exposure room, a beam line, and the like of an X-ray exposure apparatus according to another modification of the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 11 beam current measuring unit 12 synchrotron ring 13 electron beam orbit 14 beam current calculating unit 14a storage area 15 exposure time calculating unit 16 oxygen concentration measuring unit 17 oxygen concentration calculating unit 17a storage area 19 exposure room 20 mirror 21 Be thin film 22 mirror Drive unit 23 Mirror control unit 24 He circulation purification unit 31 Beam line 41 Wafer stage 42 Wafer stage drive unit 51 Mask stage 52 Mask stage drive unit 65, 67 Exposure time control unit 66, 68 Exposure control unit 71 X-ray intensity distribution control unit 72 X-ray intensity distribution control means controller 81 X-ray detector 82 X-ray intensity calculator

Claims (2)

[Claims] 1. An exposure apparatus using light emitted from a synchrotron ring as an exposure light source, wherein the measuring means directly or indirectly measures the intensity of the emitted light a plurality of times, and based on a measurement result by the measuring means. X comprising: an intensity calculating means for calculating an emission light intensity at the time of exposure; a time calculating means for calculating an exposure time based on the calculated value; and an exposure control means for performing exposure based on the calculated exposure time. Line exposure equipment. 2. An exposure method using light emitted from a synchrotron ring as an exposure light source, wherein the intensity of the emitted light is measured directly or indirectly a plurality of times before exposure.
Calculating the emission light intensity at the time of exposure based on the measurement result; calculating the exposure time of the emission light based on the calculated value; and calculating the exposure time on the substrate to be exposed based on the calculated exposure time. Performing the exposure of the radiation light.