JPH09199403A - Peojection aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To lessen the chances of appearance of defective exposure even if the wavelength of illumination light for exposure drifts. SOLUTION: The illumination light emitted from a KrF or ArF excimer laser 10 transfers a pattern on a reticle 18 onto a wafer 22 through a projection lens 20. A wavelenght monitor 50 monitors the drift of the wavelength of the illumination light and an excimer laser controller 52 controls the wavelength of the illumination light. When a main controller 54 determines that an amount of drift is out of an allowable range of an image formation characteristic, the amount of drift of the wavelength is converted to the fluctuation in focus on the wafer 22 or the change in magnification on the projection lens 20 and then the focus is corrected by a focus optical system 34, 36 or the magnification is corrected by a magnification correcting mechanism 46.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a projection exposure apparatus for manufacturing semiconductor elements such as ICs and LSIs, liquid crystal substrates, thin film magnetic heads, and the like, and more specifically to a KrF or ArF excimer. The present invention relates to a projection exposure apparatus suitable when using a light source such as a laser whose illumination wavelength varies.

[0002]

2. Description of the Related Art In a projection exposure apparatus, various improvements have been made to project a minute pattern as the degree of integration of semiconductor elements has improved. Generally, the resolution L is expressed by L = (K · λ) / NA, where λ is the illumination wavelength, K is a factor depending on the resist performance, and NA is the numerical aperture of the projection lens.
According to this, it is necessary to reduce the factor K, increase the numerical aperture NA, use illumination light having a short wavelength λ, and the like in order to form a minute pattern.

Among these elements, a KrF excimer laser (wavelength 248n is used for the purpose of shortening the wavelength.
m) or an ArF excimer laser (wavelength 193 nm) as an illumination light source is drawing attention and is being developed. However, when these lasers are used, the lens glass material is limited, and only quartz glass or fluorite glass can be used. Further, even if these glass materials are used, it is difficult to achromatize, and the wavelength fluctuation range allowed by the combination of only the lenses is several pm to several tens pm.
Therefore, it is necessary to narrow the laser band.

Therefore, conventionally, the band is narrowed by using an injection locking device. However, since the oscillation wavelength fluctuates due to drift of the reflection mirror, grating, etalon, etc. in the excimer laser, the oscillation wavelength is monitored, and the wavelength is corrected in the excimer laser each time.

[0005]

However, in such background art, when the wavelength drift greatly exceeds the control range, the control cannot be performed, and as a result, the illumination wavelength may drift. . If the illumination wavelength drifts, the reticle 100 to the projection lens 10
The focus position of the image projected on the wafer 104 via 2 changes from the focus position of FIG. 6 (A) to that of FIG. 6 (B), and an error of Δ occurs. Furthermore, when the wavelength drifts, not only the focus position but also the projection magnification and aberration change, making it impossible to form a desired reticle pattern image on the wafer.

The present invention focuses on the above points,
An object of the present invention is to provide a projection exposure apparatus capable of forming a desired reticle pattern image even if the illumination wavelength (exposure wavelength) drifts.

[0007]

[Means for Solving the Problems]

DISCLOSURE OF THE INVENTION In order to achieve the above object, the present invention provides an excimer laser (10) such as KrF or ArF.
In an apparatus for projecting and exposing a pattern on a reticle (18) onto a wafer (22) via a projection means (20) by an illumination light emitted from an illumination light source using a wavelength monitor means (50), Drift is monitored. When the drift amount determining means (54) determines that the drift amount is out of the allowable range of the imaging characteristics, the focus variation amount converting means (54) converts the drift amount of the wavelength into the focus variation amount to perform focus correction. Means (28,34,
The focus is corrected by 36). Further, according to the present invention, when it is determined that the drift amount is out of the allowable range,
The magnification change amount conversion means (54) converts the magnification change amount in the projection means, and the magnification correction means (46, 48) corrects the magnification.

According to the present invention, it is possible to prevent the occurrence of the exposure failure due to the wavelength drift and to eliminate the downtime caused by stopping the apparatus by causing the exposure error when the wavelength drift occurs.

In another aspect of the invention, when the wavelength drift amount is determined to be outside the allowable range, the dimming means (60, 62) dims the illumination light according to the wavelength drift amount. This allows re-exposure of the dimmed shot. This method is particularly effective for repairing an exposure shot when a wavelength drift occurs in a scan type exposure apparatus.

The above and other objects, features and advantages of the present invention will become apparent from the following detailed description and the accompanying drawings.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail with reference to Examples. The projection exposure apparatus shown in the following embodiments is a so-called stepper & scan type.

[0012]

First Embodiment FIG. 1 shows the arrangement of a projection exposure apparatus according to the first embodiment. First, the basic exposure operation will be described. Of the pulsed illumination light output from the excimer laser 10, the light that has passed through the half mirror 12 is reflected and deflected by the mirror 14, and then enters the illumination optical system 16. To do.
A beam expander, a fly-eye lens, a relay optical system (all not shown), etc. are arranged in the illumination optical system 16 to make the illuminance as illumination light uniform and to obtain a desired illumination condition (for example, The pulsed light is shaped so as to satisfy (σ value determination, etc.). Then, the shaped pulsed light illuminates the reticle 18 as exposure illumination light. The light transmitted through the reticle 18 is condensed on the wafer 22 by the projection lens 20, the pattern on the reticle is projected on the wafer 22, and the wafer 22 is exposed.

By the way, the wafer 22 is placed on the Z tilt stage 26 on the XY stage 24.
X, Y by the motor 70 via the stage controller 28
And Z tilt (inclination θ) direction. For this movement control, a movable mirror 30 is arranged on the Z tilt stage 26, and the position of the movable mirror 30 can be measured with high accuracy in the X and Y directions using the movable mirror 30 and the interferometer 32. XY based on position information from total 32
Positioning control of the stage 24 is performed. Further, the surface of the wafer 22 is observed by the focus detection optical systems 34 and 36, which enables highly accurate positioning control also in the Z tilt direction.

On the other hand, the reticle 18 is mounted on the reticle stage 40 on the reticle support 38.
The reticle stage 40 can also be moved in the X, Y, and Z tilt (tilt θ) directions by the motor 71 via the stage control device 28. Then, similarly to the wafer stage side, the moving mirror 42 and the interferometer 44 on the reticle stage 40 are used.
The stage control device 28 performs positioning control in the X, Y, and Z tilt (inclination θ) directions using.

As described above, in this embodiment, the stage controller 28 controls the drive of the reticle 18 and the wafer 22. Then, particularly during the exposure operation, the exposure is performed by scanning the reticle 18 and the wafer 22 relative to the projection lens 20.
For a scan speed V of 2, the projection magnification m (for example, 1/4
Alternatively, synchronous control is performed so that the reticle 18 is scanned at a speed V / m divided by 1/5.

Next, the projection lens 20 has a magnification correction mechanism 4
6 is installed, and the projection lens magnification can be changed by minutely controlling the lens interval of the lens element on the reticle side of the projection lens 20. The magnification correction mechanism 46 is controlled by a magnification controller 48. Such a magnification correction mechanism 46
Is disclosed in, for example, Japanese Patent Laid-Open No. 4-134813.

Next, the light deflection side (reflection side) of the half mirror 12 provided on the emission side of the excimer laser 10 described above.
Is provided with a wavelength monitor 50. The wavelength monitor 50 is for sampling incident light in synchronization with pulsed light emission, and its output side is connected to an excimer laser control device 52. Excimer laser controller 52
Is for monitoring the presence or absence of wavelength drift and finely controlling a reflecting mirror (not shown) in the excimer laser 10 according to the monitoring result.

The stage controller 28, the magnification controller 48, and the excimer laser controller 52 described above are all connected to a main controller 54. The main controller 54 of the present embodiment executes the operation as shown in FIG.

Next, the operation of this embodiment when the wavelength changes will be described. Of the pulsed light emitted from the excimer laser 10, the light that has passed through the half mirror 12 is exposed as described above. On the other hand, the light reflected and deflected by the half mirror 12 enters the wavelength monitor 50 and is sampled here in synchronization with pulsed light emission (step S1 in FIG. 2).
0). The sampling result of the wavelength monitor 50 is supplied to the excimer laser control device 52, where the presence or absence of wavelength drift of the excimer laser 10 is monitored. The excimer laser control device 52 performs feedback control by finely controlling the reflection mirror in the excimer laser 10 so as to prevent the occurrence of wavelength drift. As a result, normally, the wavelength drift of the excimer laser 10 is controlled within a predetermined range (Y in step S12).
s).

Allowable value ± Δ for the target value λο of wavelength control
The value of λ, that is, the permissible range of the imaging characteristics can be set from the outside, but here it is assumed that a value that is twice the measurement reproducibility of the wavelength monitor 50 is set as the default. If the measured value λ of the wavelength monitor 50 is λ ≧ λο−Δλ, S10 → S12 → S10 →
The operation of the loop is repeated during exposure.

However, when a large wavelength drift that exceeds the control range of the excimer laser control device 52 occurs, exposure is performed with light of a changed wavelength,
Imaging defects will occur. For example, λ> λο−Δλ
In this case, the wavelength drift amount Δλ = λ−λο is converted by the main controller 54 into the focus shift ΔF on the wafer 22 and the magnification change ΔM of the projection lens 20 (step S14). Then, the magnification change Δm is supplied to the magnification control device 48, and the magnification correction mechanism 46 is instructed to correct the magnification change Δm (step S16). The focus shift ΔF is supplied to the stage controller 28, and is corrected by offsetting the servo values of the focus optical systems 34 and 36 here (step S18).

Then, the excimer laser control device 52 checks the response of the tracking control of the focus and magnification correction from the change of the wavelength drift (step S2).
0). As a result, when it is considered that the wavelength drift changing speed is slow and the focus and magnification control are sufficiently followed, there is no problem in the imaging characteristics, and the exposure operation is continued (Yes in step S22). However, when the wavelength drift change is abnormal, for example, when the synchronization is short or the change amount is too large (No in step S22), other aberrations also deteriorate, so the excimer laser control device 52 causes the main control device 54 to shoot. A printing error display is instructed (step S24), and an operator's action is required.

As described above, according to the present embodiment, when the illumination wavelength drifts beyond the allowable value of the imaging characteristic, the focus variation amount and the magnification variation amount corresponding to the drift amount are calculated, and these The focus and magnification corresponding to the calculated value are corrected. As a result, the occurrence of exposure failure due to wavelength drift is favorably reduced, and the yield is improved. In addition, downtime due to stopping the entire apparatus by causing an exposure error when a wavelength drift occurs is reduced, and work efficiency is improved.

[0024]

Second Embodiment Next, a second embodiment will be described with reference to FIGS.
Will be described. The same reference numerals are used for the components corresponding to those in the first embodiment described above. In the above embodiment,
Although the focus and the magnification are corrected when the wavelength drift exceeds the allowable value, the dimming process is performed in the second embodiment.

In FIG. 3, a continuous dimming driving device (darkening filter) 60 is arranged on the light emission side of the excimer laser 10, and the illumination light is dimmed to an arbitrary amount by this. ing. The degree of dimming is controlled by the dimming controller 62, and the amount of dimming is determined by the main controller 54 according to the output result of the wavelength monitor 50 described above. Further, a half mirror 64 is provided in the illumination optical system 16, and a part of the light flux extracted by the half mirror 64 enters the integrator sensor 66. This integrator sensor 66 is
The illuminance of the exposure light is constantly monitored, and its output side is connected to the main controller 54 via an illuminance calculation device 68. As a result, error information regarding dimming is supplied to the main controller 54.

Next, the operation of the second embodiment configured as described above will be described with reference to FIG. 4 showing the sequence. First, the sampling of the laser light wavelength by the wavelength monitor 50 (step S30 in FIG. 4) and the drift check (step S32) to see if it is within the allowable range of the imaging characteristics are the same as in the first embodiment. And
If the wavelength drift exceeds the allowable range (step S
32), the main controller 54 controls the dimming controller 6
2 is commanded, and the dimming driving device 60 continuously dims the light according to the wavelength drift Δλ (step S
34). This is because if the pulse is stopped immediately, the shot during the exposure cannot be restored, but in the case of scan exposure, if the correction exposure is performed according to the exposure amount during the correction exposure,
This is because restoration becomes possible.

In this way, when a wavelength drift exceeding the allowable range occurs, in other words, it is determined whether the wavelength drift affects the imaging characteristics. By performing the light reduction by the driving device 60, the occurrence of exposure failure can be prevented. When this dimming is performed, dimming data, that is, data of the exposure target and the exposure state such as the dimmed wafer, shot, in-shot dimming start position, dimming amount, etc. It is stored for re-exposure (step S36).

Since the wavelength drift may have returned when stepping is performed after the exposure of the shot, dummy pulse light emission is performed and the illuminance is also monitored by the integrator sensor 66 (step S38). Then, it is confirmed that the dimming, that is, the illuminance is lower than the target illuminance and the wavelength drift is other than the allowable value,
It is confirmed by the main controller 54 that the wavelength drift has occurred during the exposure (step S40), the wafer is stored in the wafer retracting cassette (not shown), and the stored extinction data is corrected by the exposure. It is saved as a file for use (step S42).

After that, the exposure apparatus performs S4 for a predetermined time.
A waiting state in which the sequence of 9 → S50 is repeated is entered (step S46). If the wavelength drift does not fall within the allowable value even after the lapse of a predetermined time, the main controller 54 determines that the error end mode is in effect, displays an error (step S48), and ends the process. However, since the correction exposure file is saved even when the error ends, it is possible to perform the correction exposure of the wafer in the accommodated cassette again after investigating the cause of the error.

On the other hand, when the wavelength drift is within the allowable value within the predetermined time in the waiting state in which the sequence of S49 → S50 is repeated, the wafer is automatically taken out from the evacuation cassette and the information of the corrected exposure file is read. Exposure for correction is carried out according to (step S4).
4). After the correction exposure, the exposure is continued in the normal sequence.

Further, returning to S40, when the illuminance is lower than the target illuminance but the wavelength drift is within the allowable value,
Since the wavelength drift has already disappeared at the time of stepping, according to the stored extinction data,
Correction exposure for that shot will be performed (step S
51). After the correction exposure, the exposure is continued in the normal sequence.

FIG. 5 shows a state of the above operation. FIG. 6A shows the amount of pulsed light during shot exposure, where the horizontal axis represents time and the vertical axis represents wavelength. The circles in the figure correspond to one pulse, and the range of ± Δλ is the range that does not affect the imaging characteristics. In the example of the figure, time t1
Therefore, the wavelength drift exceeds the allowable range. At this time point t1, as shown in FIG. 7B, the pulse exposure amount is gradually reduced, and the light amount is controlled so as to decrease in accordance with the wavelength drift. Then, at the time t2 when the wavelength drift is corrected, the correction exposure is performed as shown by the graph G1 in FIG. The graph G2 is the dimming graph of the same figure (B) described above, and the insufficient light amount due to this dimming is represented by the graph G.
Correction exposure (re-exposure) is performed so that the total exposure amount becomes equal by performing the correction exposure at 1. Graph G3
Is the total exposure amount obtained by adding the graphs G1 and G2.
The method of the second embodiment as described above is particularly effective for repairing the exposure shot at the time of wavelength drift in the scanning exposure apparatus.

As described above, according to the second embodiment, when the wavelength drift exceeding the allowable value occurs, the light is reduced, and the correction exposure is performed when the wavelength drift disappears. Even if the drift occurs, it is possible to reduce the occurrence of exposure failure and reduce the downtime of the apparatus. Further, even if a wavelength drift more than an allowable amount occurs during shot exposure, it is possible to restore the shot with uniform and excellent image formation.

When a neutral density filter is inserted by the neutral density drive unit 60 (the laser 10 itself may be neutralized), the resist on the wafer 22 is slightly exposed to form a latent image. By investigating, it is possible to know how far the wavelength was drifted when the exposure was performed.

[0035]

Other Embodiments The present invention has many embodiments and can be variously modified based on the above disclosure. For example, the following is also included. (1) The present invention is suitable for a so-called step & scan type exposure apparatus, but it does not prevent application to a so-called step & repeat type exposure apparatus in which static exposure and stepping are repeated. (2) In addition, the configuration of each part can be modified in design so as to achieve the same operation within the scope of the present invention.

[0036]

As described above, according to the present invention, even if the wavelength drift of the exposure illumination light occurs, the focus and magnification are corrected or the light is reduced so that the imaging defect does not occur. Therefore, it is possible to reduce the occurrence of exposure failure and to reduce the downtime of the apparatus.

[Brief description of drawings]

FIG. 1 is a block diagram showing a device configuration of a first embodiment of the present invention.

FIG. 2 is a flowchart showing an operation sequence of the first embodiment.

FIG. 3 is a block diagram showing a device configuration of a second embodiment of the present invention.

FIG. 4 is a flowchart showing an operation sequence of the second embodiment.

FIG. 5 is a graph showing the effects of dimming and correction exposure of Example 2.

FIG. 6 is a diagram showing a focus variation at the time of wavelength drift in the background art.

[Explanation of reference numerals] 10 ... Excimer laser 16 ... Illumination optical system 18 ... Reticle 20 ... Projection lens 22 ... Wafer 28 ... Stage control device 34, 36 ... Focus optical system 46 ... Magnification correction mechanism 48 ... Magnification control device 50 ... Wavelength monitor 52 ... Excimer laser control device 54 ... Main control device 60 ... Continuous dimming drive device 62 ... Dimming control device 66 ... Integrator sensor 68 ... Illuminance calculation device 70, 71 ... Motor

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location H01L 21/30 516C

Claims (6)

[Claims] 1. A projection exposure apparatus for projecting a pattern formed on a reticle onto a wafer by a projection means by using illumination light output from an excimer laser as a light source, and monitoring a wavelength drift of the illumination light. Wavelength monitor means for controlling the wavelength drift; a drift range determining means for determining whether the wavelength drift monitored thereby is within the allowable range of the imaging characteristics;
Focus variation amount conversion means for converting the wavelength drift amount into the focus variation amount in the projection means when it is determined that the wavelength drift is out of the allowable range; the projection variation amount is obtained based on the focus variation amount thus obtained. A projection exposure apparatus comprising: a focus correction unit that corrects a focus position in the unit. 2. A projection exposure apparatus for projecting a pattern formed on a reticle onto a wafer by a projection means by using illumination light output from an excimer laser as a light source, and monitoring a wavelength drift of the illumination light. Wavelength monitor means for controlling the wavelength drift; a drift range determining means for determining whether the wavelength drift monitored thereby is within the allowable range of the imaging characteristics;
When it is determined that the wavelength drift is out of the allowable range, the magnification change amount conversion means for converting the wavelength drift amount into the magnification change amount in the projection means; the projection change amount based on the magnification change amount thus obtained. A projection exposure apparatus comprising: a magnification correction means for correcting the magnification in the means. 3. The projection exposure apparatus according to claim 1, wherein a follow-up detection unit that detects the follow-up property of the correction by the correction unit; when a deterioration of the follow-up property is detected by this, an error display to that effect is displayed. A projection exposure apparatus, comprising: an error display means for performing. 4. A projection exposure apparatus for projecting a pattern formed on a reticle onto a wafer by a projection means by using illumination light output from an excimer laser as a light source, and monitoring a wavelength drift of the illumination light. Wavelength monitor means for controlling the wavelength drift; a drift range determining means for determining whether the wavelength drift monitored thereby is within the allowable range of the imaging characteristics;
Accordingly, the projection exposure apparatus is provided with a light reducing unit that reduces the illumination light according to the wavelength drift amount when it is determined that the wavelength drift is out of the allowable range. 5. The projection exposure apparatus according to claim 4, wherein a light quantity monitor means for monitoring the light quantity of the illumination light with respect to the wafer; an exposure control means for confirming dimming from the monitored light quantity value and stopping the exposure processing. And a projection exposure apparatus. 6. The projection exposure apparatus according to claim 4 or 5, wherein dimming data storage means for storing data of an exposure target and an exposure state at the time of dimming by the dimming means; A projection exposure apparatus comprising: a correction exposure control unit that performs a correction exposure by referring to the data stored in the dimming data storage unit.