JP3919424B2 - Scanning exposure apparatus and device manufacturing method using the scanning exposure apparatus - Google Patents

Description

[0001]
The present invention relates to a scanning exposure apparatus and a device manufacturing method using the scanning exposure apparatus.
[0002]
[Prior art]
In a scanning type semiconductor exposure apparatus, as means for adjusting the uniformity of the exposure amount on a wafer (irradiated surface), Japanese Patent Application Laid-Open No. 62-193125 discloses a case where illuminance is high for each coordinate in the non-scanning direction. Discloses a method of making the amount of light integrated in the scanning direction uniform for each coordinate by narrowing the width of the irradiation range in the scanning direction and conversely adjusting the irradiation range to be widened in places where the illuminance is low. ing.
[0003]
Also, with the increasing demand for fine processing of semiconductor exposure apparatuses, it is essential to use light sources with shorter wavelengths, specifically excimer lasers. The excimer laser is a pulsed light source with high coherence, and when used in an exposure apparatus as it is, the illuminance distribution of the light source is reflected on the irradiation surface as it is. For this reason, in Japanese Patent Laid-Open No. 10-32164, focusing on the coherence anisotropy of illumination light, a vibration means that vibrates in a high direction is set so that the low coherence direction is substantially coincident with the scanning direction. It is provided to reduce the illuminance unevenness and make the illuminance distribution uniform on the irradiated surface.
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional semiconductor exposure apparatus using a coherent light source, the illuminance on the photosensitive substrate changes and uneven exposure occurs.
In other words, in a semiconductor exposure apparatus using a coherent light source, since the influence of fine illuminance unevenness (speckle) that the light source has on the photosensitive substrate, it is active to eliminate the influence of the speckle. By moving the optical element, the optical axis is swung to eliminate the influence of speckle.
However, the influence of shaking the optical axis is on the optical measurement sensor, particularly the detector that controls the exposure amount of the photosensitive substrate. Since this detector derives and measures a part of the light reaching the irradiated surface, as a result, the illuminance on the photosensitive substrate changes and a kind of lumps (illuminance disturbance) as shown in FIG. 1 occurs. End up.
[0005]
On the other hand, the exposure amount of the semiconductor exposure apparatus is represented by time integration of the illuminance on the photosensitive substrate. In particular, in the scanning exposure method, the interval integration of the time required for the exposure light to pass through one point on the irradiated surface (FIG. 2: P). The value is the amount of exposure on the photosensitive substrate. Therefore, in the scanning exposure apparatus, if the passage time P is constant, the exposure amount on the photosensitive substrate can be made constant by making the temporal illuminance constant, but in practice, as described above. In addition, due to the frustration caused by the optical elements, the illuminance on the photosensitive substrate changes and uneven exposure occurs.
[0006]
Accordingly, the present invention is an object to provide a device manufacturing method according to the available scanning exposure apparatus and the scanning exposure apparatus to reduce the exposure unevenness that occurs sensitive optical substrate.
[0007]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a scanning exposure apparatus configured as follows (1) to ( 6 ) and a device manufacturing method using the scanning exposure apparatus.
(1) an illumination optical system for illuminating a mask by the illuminating light having a coherence from the pulsed light source, the mask and the projection optical system, the illumination light for projecting a pattern of a mask illuminated by the illumination optical system to the photosensitive substrate A scanning exposure apparatus having a driving means for periodically driving an optical element in the illumination optical system to periodically move the optical element .
The passing time required for one point on the photosensitive substrate to pass through the illumination area on the photosensitive substrate is an integral multiple of the operating period of the optical element by the driving means, and the oscillation period of the pulsed light source with respect to the operating period A ratio is a non-integer, and the operation period is such that the oscillation period is a value obtained by multiplying the oscillation period by an integer that is an integer or a number close to an integer. A scanning exposure apparatus , wherein a scanning speed, the operation period, and the oscillation period are set .
(2) The scanning exposure according to (1), wherein the passage time is determined by a representative value of the width of the illumination area in the scanning direction of the photosensitive substrate and a scanning speed of the photosensitive substrate. apparatus.
(3) The passing time is determined by an effective width of the illumination area in the scanning direction of the photosensitive substrate based on a light intensity distribution of the illumination area and a scanning speed of the photosensitive substrate. The scanning exposure apparatus according to (1) above.
(4) said driving means, scanning exposure apparatus according to any one of (1) to (3), wherein the Rukoto rotate the wedge plate as the optical element.
(5) said driving means, scanning exposure apparatus according to any one of (1) to (3), wherein the Rukoto by vibrating the mirror as the optical element.
( 6 ) A device manufacturing method comprising manufacturing a device using the scanning exposure apparatus according to any one of (1) to ( 5 ).
[0008]
DETAILED DESCRIPTION OF THE INVENTION
In the embodiment of the present invention, by applying the above-described configuration, it is possible to reduce the illuminance illusion of the non-irradiated surface and the optical measurement sensor caused by the optical element that is not affected by the coherent light and is actively moved. Good exposure that is not received can be performed. As a result of intensive studies by the present inventor, if the operation cycle P_opt of the optical element for speckle removal is proportional to the time P during which the exposure light passes through a certain point on the photosensitive substrate, the interval integral value of the illuminance illusion is obtained. This is based on the knowledge that exposure unevenness due to illuminance illusion can be eliminated.
[0009]
This point will be further explained. Since the exposure light passage time P is derived from the scanning direction distribution width Sw of the exposure light used during exposure and the scanning speed V, the operation period P_opt of the optical element is set in proportion to the scanning speed. It is possible to re-do.
If the exposure light intensity distribution shape in the scanning direction is a rectangular shape, the scanning direction distribution width Sw of the exposure light is uniquely determined. However, if the exposure light intensity distribution is actually rectangular, scanning is performed when a pulse light source is used. It is known that the difference between the speed and the pulse period has a large effect on increasing the exposure unevenness. Therefore, in practice, it is effective to provide a shape in which the irradiation region changes asymptotically, including a trapezoidal distribution shape (FIG. 3). When the exposure light intensity distribution is other than the rectangular shape, it is necessary to have a means for actually measuring the exposure light distribution width that minimizes the exposure unevenness. Further, when the illumination shape changes, the exposure light intensity profile shape also changes. Therefore, a method of measuring the width for each illumination mode and optimizing the operation cycle of the optical element can be considered.
In a scanning exposure apparatus, it is effective to change the scanning direction distribution width of exposure light in order to remove unevenness in illuminance in the non-scanning direction (FIG. 4). In this case, since the exposure light width in the non-scanning direction is not determined, a means for finding a period P_opt that minimizes the influence of exposure unevenness is also required.
[0010]
【Example】
Examples of the present invention will be described below. FIG. 5 is a view showing a schematic configuration of a scanning type exposure apparatus in an embodiment of the present invention.
In FIG. 5, 1 is an excimer laser that is a light source, 3 is a beam shaping optical system that shapes the beam shape of the laser light from the light source 1 and makes it incoherent, 5 is an optical integrator, and 6 is an optical that is a secondary light source. This is a condensing lens for illuminating the surface of the masking blade 9 with the light beam from the integrator 5. A half mirror 7 divides a part of the light beam from the optical integrator 5, and the divided light beam is incident on the detector 12 by the lens 11, and the exposure amount is monitored.
[0011]
Slit 8 is placed at a position shifted in the optical axis direction by a surface or al a predetermined distance of the masking blade 9, the shape is composed of two pairs of light shielding plates for shielding a light flux for a direction perpendicular to the optical axis within the plane Yes. The masking blade 9 is composed of four independently operated light shielding plates, and is projected onto the reticle R by the imaging lens 10. Although the slit 8 is also projected onto the reticle R by the imaging lens 10, the light intensity distribution by the slit 8 is as shown in FIG. As shown in FIG.
[0012]
M1, M2, and M3 are bending mirrors for bending the optical path . The circuit pattern on the reticle R is projected onto the photosensitive substrate W by the projection optical system 13. Reference numeral 16 denotes a stage 16 for holding the photosensitive substrate and performing scanning at a constant speed while synchronizing with the reticle R in the scanning direction indicated by an arrow. An illuminance meter 14 for measuring the illuminance on the surface corresponding to the photosensitive substrate W surface is disposed on the stage 16. 15 is an exposure amount calculation unit for calculating the light emission timing of the next pulse and a target light amount in order to supply an accurate exposure amount on the photosensitive substrate W from the light amount measured by the detector 12, and 17 is a main part of the projection exposure apparatus. It is a control unit.
[0013]
When a light source having high excimer laser coherence is used, fine illuminance unevenness (speckle) possessed by the light source is reflected on the photosensitive substrate W. The uneven illuminance in the scanning exposure apparatus becomes the uneven exposure amount in the non-scanning direction. Therefore, speckles are removed by taking measures such as shaking the illumination light. In FIG. 5, the prescription | regulation which shakes the distribution of light actively is given by methods, such as rotating the wedge board 2 and the vibrating mirror 4 to vibrate. Speckle can be removed by apparently shaking the illumination light source.
[0014]
However, when the illumination light is shaken by the optical element, the illuminance of the illuminometer 14 that measures the illuminance on the surface corresponding to the detector 12 and the photosensitive substrate W due to factors such as the light quantity characteristic of the half mirror 7 that introduces the illumination light into the detector 12. The ratio will change. Therefore, even if the light amount calculation unit calculates the illuminance to be constant in the detector 12, the exposure amount on the photosensitive substrate W results in the rotation period of the wedge plate 2 or the vibration period of the vibrating mirror 4. End up. FIG. 1 shows a detector 12 used for exposure amount control and an illumination error on the photosensitive substrate W. At this time, the rotation period of the wedge plate 2 or the vibration period of the vibrating mirror 4, that is, the period of illumination illusion P_opt. Is riding.
[0015]
The exposure amount in the scanning exposure apparatus is given by the integration of the illuminance on the photosensitive substrate W. Basically, the exposure value is the value integrated by the time P required for the illumination light to pass a certain point on the photosensitive substrate W. This integration time P can be expressed by the relationship of P = Sw / V by the scanning direction width Sw of the illumination light on the photosensitive substrate W and the scanning speed V. At this time, the illuminance fluctuation of the exposure light is expressed as I = b + a exp (2πtj / P_opt) (1)
In this case, the exposure amount E on the photosensitive substrate W is given by the following equation.
E = integral [I] (TP → T) (2)
= BP + aP_opt / (2πj) exp (2πTj / P_opt) (1-exp (2πPj / P_opt))
integral [f] (t0 → t1) represents that the function f is integrated over the interval from t0 to t1.
[0016]
Here, in order to remove the periodic component of equation (2),
exp (2πPj / P_opt) = 1 (3)
Solve this,
P = nP_opt (4)
Sw / V = nP_opt (4) ′
It is necessary to hold. Therefore, it can be seen that this component can be removed by synchronizing so that the time P required to go over the photosensitive substrate W becomes an integral multiple of the fluctuation P_opt of the exposure light.
[0017]
In recent exposure apparatuses, a short wavelength laser, particularly an excimer laser is used as a light source. Since the excimer laser is a pulsed light source, the illuminance illusion period is actually generated from the vibration period of the optical element and the period of the light source. When the oscillation period of the optical element is T and the oscillation period of the pulse light source is t, the illuminance variation on the mth illumination light Im is expressed as follows.
Im = exp (2πmtj / T) (5)
Therefore,
mt / T = integer (6)
Mt becomes the change period P_opt of the illumination light with respect to m.
[0018]
Therefore, if (4) is established for this period and the time P for the stage to pass on the photosensitive substrate, a system without illuminance illusion can be constructed. In setting the exposure amount of a scanning exposure apparatus using a pulsed light source, as one method for changing the illuminance of the light source, a method of changing the oscillation frequency of the light source can be considered. In this case, since the value of t is determined, it is necessary to adjust the vibration period T of the optical element so that the expression (6) is satisfied. At this time, if the value of m is small, the speckle removal effect is weakened. Therefore, it is necessary to determine the minimum value of m to determine how much value of m is necessary for removing speckle.
[0019]
Note that (6) when the t / T is integer in expression, the light beam will always not change on speckle state in appearance at a fixed position, by adjusting the operation period of the optical element in this state Become meaningless.
In addition, there are problems such as operational cycle stability of the optical element, and when equation (6) cannot be satisfied, there exists a mode m in which the value of equation (6) is close to an integer, and it is affected by it. In this case, it is necessary to adjust the mode m so that the equation (4) is established.
[0020]
For example, the oscillation cycle of the light source is 595 Hz, and the drive cycle of the optical element is 10 msec. In this case, t / T = 0.168. At this time, since 0.168 × 125 = 21, the illuminance of the illumination light is 1/595 × 125 = 210.1 [sec. ] Is P_opt. However, since the time required for the exposure light to pass through a certain point on the photosensitive substrate is less than 10 seconds, 210.1 seconds is nonsense. At this time, since 0.168 × 6 = 1.008, 1/595 × 6 = 10.1 [msec. ], The value of P_opt is set to 10.1 [msec. ] Is more practical.
[0021]
In an actual apparatus, it is necessary to synchronize the position of the reticle R, the photosensitive substrate W, and the masking blade 9 that defines the exposure area. At that time, the period of the wedge plate 2 or the vibrating mirror 4 is set so that the period P of the slit 8 in the scanning direction width Sw and the actual scanning speed V is an integral multiple of the period of the wedge plate 2 or the vibrating mirror 4. Is realized by the main control unit 17 controlling.
[0022]
In the scanning exposure apparatus, the illuminance can be adjusted by changing the width of the slit 8 in the scanning direction. Therefore, the slit width Sw is not constant depending on the image height in the non-scanning direction. In this case, the information on the slit width Sw at each image height position in the non-scanning direction is used, and the expression (4) ′ is applied to the representative width Swc that is least affected by the periodic unevenness from the entire exposure region. It is possible. As a method for obtaining the representative width Swc, a method using an average value of the slit width, a method using the maximum and minimum middle values of the slit width as Swc, and the like are conceivable.
[0023]
In the scanning exposure apparatus, since the slit 8 is located at a position shifted from the optical conjugate position, the light intensity distribution of the illumination light basically has a trapezoidal shape. Therefore, the execution slit width for actually making the illuminance uniform may be different from Sw. The most general idea is to use the exposure light width Swi at the 50% threshold of the upper base portion of the trapezoidal intensity distribution. In addition, depending on the illumination shape, there may be a case where the trapezoidal shape distribution is not possible. In this case, it may be possible to actually measure the optimum period by changing the value of P_opt.
[0024]
In addition, this method may be applied to illuminance fluctuations that cannot be removed by the light amount calculation unit 15 that controls the light source 1 so as to give a desired illuminance to the photosensitive substrate W. In this case, the present method may be applied by setting the period of illuminance fluctuation that cannot be removed as P_opt.
[0025]
Further, in a static exposure apparatus that transfers a mask pattern to a photosensitive substrate by a step-and-repeat method, the exposure amount given to the photosensitive substrate is given by illuminance and exposure time. Therefore, by replacing the exposure time with P and applying the equation (4), a stationary exposure apparatus that performs good exposure with no difference in exposure amount between chips can be configured.
[0026]
【The invention's effect】
As described above, according to the present invention, it is possible to realize a device manufacturing method according capable scanning exposure apparatus and the scanning exposure apparatus to reduce the exposure unevenness that occurs on the photosensitive substrate.
[Brief description of the drawings]
FIG. 1 is a diagram showing a detector used for exposure amount control and an illumination error on a photosensitive substrate.
FIG. 2 is a diagram for explaining that an exposure amount of an exposure apparatus is expressed by time integration of illuminance on a photosensitive substrate.
FIG. 3 is a diagram for explaining that an irradiation region has a shape that changes asymptotically in the embodiment of the present invention.
FIG. 4 is a diagram for explaining changing of the scanning direction distribution width of exposure light in order to remove unevenness in illuminance in the non-scanning direction in the embodiment of the present invention.
FIG. 5 is a view showing a schematic configuration of a scanning type exposure apparatus in an embodiment of the present invention.
[Explanation of symbols]
1: Light source 2: Wedge plate 3: Beam shaping optical system 4: Vibrating mirror 5: Optical integrator 6: Condensing lens 7: Half mirror 8: Slit 9: Masking blade 10: Imaging lens 11: Lens 12: Detector 13 : Projection optical system 14: Illuminometer 15: Exposure amount calculator 16: Stage 17: Main controller of the projection exposure apparatus

Claims (6)

Period and an illumination optical system for illuminating a mask by the illuminating light, a projection optical system for projecting a pattern of a mask illuminated by the illumination optical system to a photosensitive substrate, the illumination light to the mask with the coherence of the pulsed light source A scanning exposure apparatus having driving means for periodically driving the optical elements in the illumination optical system to move the optical elements
The passing time required for one point on the photosensitive substrate to pass through the illumination area on the photosensitive substrate is an integral multiple of the operating period of the optical element by the driving means, and the oscillation period of the pulsed light source with respect to the operating period A ratio is a non-integer, and the operation period is such that the oscillation period is a value obtained by multiplying the oscillation period by an integer that is an integer or a number close to an integer. A scanning exposure apparatus , wherein a scanning speed, the operation period, and the oscillation period are set . 2. The scanning exposure apparatus according to claim 1, wherein the passage time is determined by a representative value of the width of the illumination area in the scanning direction of the photosensitive substrate and a scanning speed of the photosensitive substrate. 2. The transit time is determined by an effective width of the illumination area in a scanning direction of the photosensitive substrate based on a light intensity distribution of the illumination area and a scanning speed of the photosensitive substrate. The scanning exposure apparatus described in 1. It said drive means, the scanning exposure apparatus according to any one of claim 1 3, wherein Rukoto rotate the wedge plate as the optical element. It said drive means, the scanning exposure apparatus according to any one of claim 1 3, wherein Rukoto by vibrating the mirror as the optical element. Device manufacturing method characterized by manufacturing a device using a scanning exposure apparatus according to any one of claims 1-5.

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