JPH11249316A - Light source output control method, light source device, exposing method and aligner - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the influence of the irregular operation of a shutter and to restrain the dispersion of the line width of a resist pattern formed on a wafer by controlling output from a light source in accordance with the state of the progress of the opening/closing operation of the shutter. SOLUTION: Luminous flux from a mercury lamp 2 is made incident on a beam splitter 4, the luminous flux reflected by the beam splitter 4 is condensed on the other focal position of an elliptical mirror 3, and the shutter 9 is arranged at the focal position. The rotating position of a shutter blade is measured by a rotary encoder 8. The dispersion of the operation of the shutter is known about 3 ms after issuing an opening/closing command for the shutter. Based on the shutter position obtained after 3 ms, supply power to the mercury lamp 2 is changed for only 9 ms from 3 ms to 12 ms after starting closing operation. Even when the supply power is changed, the output of the mercury lamp 2 does not follow the change immediately, so that such a change ratio that integrated exposure may be always its standard value is experimentally obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to control of the output of a light source such as an exposure light source of a projection exposure apparatus, and more particularly to control of the integrated exposure amount of a batch exposure type exposure apparatus.

[0002]

2. Description of the Related Art A projection exposure apparatus is used in a lithography step in a process of manufacturing a semiconductor device, a thin film magnetic head, a liquid crystal display device, and the like. One of the performances required for a projection exposure apparatus is the uniformity of the line width of a pattern formed on a resist. In order to keep the line width of the resist pattern within a certain range, the stability of the integrated exposure energy given to the resist is important together with the stability of the shape of the pattern image represented by the stability of focus. There are two types of exposure equipment: scanning exposure equipment and one-shot exposure equipment. Among these, one-shot exposure equipment uses the following method, for example, to keep the integrated exposure amount given to the resist constant. Had been.

[0003] A first sensor for measuring the amount of light from the light source, a shutter for passing and blocking the light beam from the light source, and a second sensor for measuring the amount of light passing through the shutter are provided. Then, using the second sensor in advance, the reference value E of the integrated exposure amount during the closing operation period from issuing a close command to the shutter at the fully open stop position until reaching the fully closed stop position.
_{Find A0} . Next, in each actual exposure shot, the light amount e that has passed through the shutter is measured by the second sensor, and this is integrated to calculate the integrated exposure amount E. When the reference integrated exposure amount determined for each resist is E ₀ , the integrated exposure amount E that has passed through the shutter is E _S −
When _EA0 is reached, a shutter close command is issued.
By controlling in this manner, it is possible to match the integrated exposure amount E to the reference integrated exposure amount E _0.

The error factors in this control method include:
A first error factor is a fluctuation in the output of the light source after a shutter close command is issued, and a second error factor is a variation in shutter operation. this house,
With respect to the output fluctuation of the light source, which is the first error factor, the fluctuation amount can be reduced by constantly measuring the output of the light source using the first sensor and applying feedback to the output of the light source. On the other hand, as for the variation of the shutter operation, which is the second error factor, only an attempt has been made to reduce the variation. But since the ratio of the integrated exposure amount E _A0 in closing operation occupying the reference integrated exposure amount E ₀ of the total originally small, even if there is some variation in the actual integrated exposure amount E _A during closing operation, a significant disadvantage It was not an invitation.

[0005]

However, in recent years, in order to improve the throughput, the amount of light from a light source is increasing, and the sensitivity of a photoresist as a photosensitive agent is also increasing. Therefore, the ratio of the integrated exposure amount E _A0 in closing operation to the whole of the reference integrated exposure amount E ₀ also been increasing. Therefore, no matter how stable the output fluctuation of the light source, if there is a variation in the closing operation of the shutter, a variation in the integrated exposure amount E to the wafer occurs, and as a result, a variation in the resist line width for each shot occurs, and as a result, the manufacturing is completed. There is a possibility that this may cause malfunction of the semiconductor element or the like. The present invention has been made to solve the above problem, and to provide a light source output control method capable of minimizing the influence of shutter operation unevenness and reducing the line width variation of a resist pattern formed on a wafer. Make it an issue. Another object of the present invention is to provide a light source device, an exposure method, and an exposure apparatus using the light source output control method.

[0006]

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems. That is, in a light source output control method for controlling an output of a light source having a shutter, a shutter position for measuring a position of the shutter is provided. A sensor is provided, and according to the speed of progress of the closing operation of the shutter,
A light source output control method characterized by controlling the output of a light source. The present invention also provides a light source device including a light source, a light source output control device that controls the output of the light source, and a shutter that passes and blocks a light beam from the light source, wherein the light source device has a shutter position sensor that measures the position of the shutter. And the light source output control device is configured to control the output of the light source in accordance with the speed of progress of the closing operation of the shutter. The present invention also relates to an exposure method for illuminating a pattern on a projection original with an illumination optical system, and forming an image of a light beam transmitted through the pattern on a photosensitive substrate by a projection optical system, thereby transferring the pattern onto the photosensitive substrate. In the illumination optical system, at least a light source, a light source output control device that controls the output of the light source, and a shutter that passes and blocks a light beam from the light source,
An exposure method comprising: providing a shutter position sensor for measuring a position of a shutter; and performing exposure while controlling an output of a light source in accordance with a slow progress of a shutter closing operation by a light source output control device. The present invention is also directed to an exposure apparatus that illuminates a pattern on a projection original with an illumination optical system and forms a light flux transmitted through the pattern on a photosensitive substrate by a projection optical system to transfer the pattern onto the photosensitive substrate. The illumination optical system includes a light source, a light source output control device that controls the output of the light source, a shutter that passes and blocks a light beam from the light source, and a shutter position sensor that measures the position of the shutter. The exposure apparatus is configured to control an output of a light source in accordance with a speed of progress of a closing operation of a shutter.

[0007]

Embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a configuration diagram showing a batch exposure type exposure apparatus according to one embodiment of the present invention. A 2.5 kW mercury lamp 2 supplied with power from a power supply (not shown) and controlled by the lamp control device 1 is arranged at one focal position of the elliptical mirror 3. The luminous flux from the mercury lamp 2 is incident on the beam splitter 4, and among the luminous fluxes incident on the beam splitter 4, the luminous flux transmitted through the beam splitter 4 is:
passes through an optical filter (not shown) that transmits only i-line,
The light is condensed by the condenser lens 5 and enters the light amount sensor 6. On the other hand, the light beam reflected by the beam splitter 4 is
Light is condensed at the other focal position of the elliptical mirror 3, and a shutter 9 is arranged at this focal position. The shutter 9 has a plurality of blades, and is configured to pass or block a light beam by rotating the blades. The rotation position of the shutter blade is measured by the rotary encoder 8.

The light beam that has passed through the shutter 9 is filtered by an interference filter 10 to remove components other than the i-line, shaped by an input lens 11, then enters a fly-eye lens 12, and exits from the fly-eye lens 12. Are formed in the vicinity of. An illumination system aperture stop 13 is arranged near the exit surface of the fly-eye lens 12, and in this embodiment, a plurality of types of aperture stops 13 are attached to an aperture stop revolver 13a so that they can be switched and used. Is configured. The light beam that has passed through the illumination system aperture stop 13 passes through the first relay lens 14 and is incident on the beam splitter 15. A part of the light beam reflected by the beam splitter 15 is condensed by a condenser lens 16 and is incident on an integrator sensor 17. The luminous flux transmitted through the beam splitter 15 is projected onto a projection type reticle blind 18 arranged on the Fourier transform surface of the aperture stop 13.
After passing through the second relay lens 19, the reticle 20 arranged on the conjugate plane of the blind 18 is illuminated. The pattern 21 on the reticle 20 is projected by a projection lens 22 on a wafer 24 placed on a wafer stage 23. Reticle 20 is held by reticle stage RST, and reticle stage RST can be moved two-dimensionally by a reticle drive system (not shown).
The wafer stage 23 can also be moved two-dimensionally by a wafer drive system (not shown).

FIG. 2 shows the progress of the closing operation of the shutter 9 and the specific output T of the integrator sensor 17 at that time. That is, the horizontal axis in FIG. 2 indicates the time after the shutter closing command, and the curve S on the vertical axis indicates the relative position of the shutter blade measured by the encoder 8. The relative position S of the shutter blades is a value obtained by standardizing a fully open stop position (hereinafter simply referred to as a fully open position) to S = 1 and a fully closed stop position (hereinafter simply referred to as a fully closed position) to S = 0. is there. A curve T indicates the specific output of the integrator sensor 17. The specific output T of the integrator sensor is the output A when the position S of the shutter blade is at the fully open position (S = 1).
Is normalized to 1. When the shutter is fully closed (S
= 0), the output A of the integrator sensor
Is A = 0, and therefore the specific output T is also T = 0.

Here, when the actual operation of the shutter 9 is viewed, as shown in FIG. 3, the operation of the shutter operates smoothly as shown by the curve S ₀ , and the integrator sensor 1
7 may also decrease steadily as shown by the curve T ₀ , but the operation of the shutter is temporarily delayed halfway as shown by the curve S ₁ , and the specific output T of the integrator sensor 17 is reduced. reduced as it may slow as indicated by the curve T _1. After closing command of the shutter 9, since the total of the output A of the integrator sensor 17 until the shutter is completely closed is equivalent to the energy E _A, variations in the shutter operation is seen to affect the exposure amount control accuracy.

The variation in the shutter operation as shown in FIG. 3 becomes apparent about 3 ms after the shutter closing command. Therefore, the closing operation of the shutter repeated several times, for each round of the closing operation, determine the position S _{3 ms} of the shutter after 3 ms, the relationship between the integrated exposure amount E _A during the closing operation period. This relationship means that the shutter position S after 3 ms
If _3ms is a standard position S _{3ms · 0,} the integrated exposure amount E _A coincides with standard integrated exposure amount E _A0, from the position S _{3ms · 0} Shutter position S _3ms it is standard after 3ms if the open side, the integrated exposure amount E _a is greater than the standard integrated exposure amount E _A0, if the closing side than the position S _{3 ms · 0} shutter position S _{3 ms} is standard after 3 ms, the integrated exposure the amount E _a is less than the standard integrated exposure amount E _A0, the relationship.

Accordingly, the integrated exposure amount E _A during the closing operation period
Is equal to the standard value E _A0 , based on the shutter position S _{3 ms} after 3 ms, the power supply P to the mercury lamp 2 for only 9 ms from 3 ms to 12 ms after the start of the closing operation.
To change. That is, 3 m after the shutter closing operation starts
Until s, the supply power P to the mercury lamp is maintained at a constant value P ₀ , but the supply power P from 3 ms to 12 ms is changed to a constant value P _3-12 ms. Here, the change ratio C of the supplied power
The, C = When _P 3-12ms / P _0, C is the shutter position after 3 ms S _{3 ms} function C (S _3ms). That is, if the shutter position S 3ms after _{3 ms} is at the standard position S _{3ms · 0} , the change ratio C
Is 1 and the shutter position S _{3 ms} is the standard position S
If the shutter position S _3ms is closer to the open side than _{3 ms · 0} , the change ratio C is 1 or less. If the shutter position S _3ms is closer than the standard position S _{3ms · 0} , the change ratio C is 1 or more.

At 3 ms after the shutter closing command,
Also the power supplied to the mercury lamp to change from P ₀ to _P 3-12ms,
Since the output of the mercury lamp does not immediately follow, the integrated exposure amount E
_The change ratio C such that _A always becomes the standard value E _A0 is experimentally obtained. The change ratio C thus obtained
FIG. 4 shows an example of (S _{3 ms} ). The change ratio C (S _3ms ) thus determined is stored in the storage device 1a in the lamp control device 1. The form of storage in the storage device 1a may be a table format or an approximate expression such as a broken line approximation. Change ratio C
The value of (S _3ms ) is preferably stored for each blade of the shutter 9.

At the time of actual exposure, at 3 ms after the shutter closing command, the encoder 9 reads the shutter position S _{3 ms} , and obtains the change ratio C based on the relationship C (S _{3 ms} ) stored in the storage device 1 a. , By multiplying the power supply P ₀ to the lamp at that time by this change ratio,
The change value P _{3-12 ms of the} power supplied to the lamp is calculated. After that, the power supplied to the lamp is changed to the changed power P _3-12 ms for only 9 ms from 3 ms to 12 ms, and
At time s, the original reference power P ₀ is restored. Actually, the lamp output does not change suddenly due to the responsiveness of the lamp power supply.

FIG. 4 shows an operation state when the mercury lamp is controlled by this method. In the figure, S ₀ , T ₀ , R
₀ indicates the relative position of the shutter, the specific output of the integrator sensor 17, and the specific output of the light amount sensor 6 at each time t after the shutter closing command when the shutter closing operation is standard. On the other hand, S ₁ , T ₁ , R
_1, the relative position of the shutter when the shutter closing operation is delayed than standard, specific power of the integrator sensor 17, indicates the specific power of the light amount sensor 6, S _2,
T ₂ and R ₂ indicate the relative position of the shutter, the specific output of the integrator sensor 17, and the specific output of the light amount sensor 6 when the shutter closing operation is faster than the standard case.

[0016] As shown in the drawing, in faster than if the shutter operation is standard, the integrated exposure amount E _A that passes through the shutter after closing command standard integrated exposure amount E _A0
Increase lamp output to be fewer than for slower than shuttering conversely standard, the integrated exposure amount E _A that passes through the shutter after closing command than standard integrated exposure amount E _A0 If also increases, which reduces the lamp power, thereby, the integrated exposure amount E _a that passes through the shutter, respectively, as compared with the case of not the lamp output control, approach the standard integrated exposure amount E _A0 You can see that.

According to a preliminary study, when the illuminance on the wafer surface is 1200 mW / cm ² and the reference integrated exposure amount E ₀ for the wafer is 50 mJ / cm ² , the control of the integrated exposure amount E in the conventional method is performed. Although the accuracy was ± 1.0% in the range, according to the present embodiment, the accuracy of the integrated exposure amount E was ± 0.1%.
It could be controlled at 3%. In the above embodiment,
Although the luminous flux is branched before the shutter and the lamp output is measured by the light amount sensor 6, it is not particularly necessary to measure the lamp output itself, and therefore the light amount sensor 6 may not be provided.

In the above embodiment, the shutter operation state was measured 3 ms after the shutter closing command, but after the shutter operation started, the operation variation became clear, and
If there is enough time left for lamp output control,
It is not limited after 3 ms. Further, the time for changing the lamp output is set to 9 ms in the above embodiment, but this is not limited to 9 ms, and the lamp output returns to the reference power P ₀ before the start of exposure of the next shot.
Any time may be used as long as the time is sufficiently stable. However, since the energy reaching the wafer decreases as the shutter closing operation proceeds, it is meaningless to maintain the changed power for a long time.

The encoder position S _3ms shown in FIG.
And the change ratio C of the power supplied to the lamp depends on the response characteristics of the lamp power supply and the aperture ratio of the shutter.
The relationship shown in FIG. 3 varies depending on the conditions. Further, the type of lamp is not limited to the above-mentioned high-pressure mercury lamp of 2.5 kW output, and other outputs may be used.
A bright line other than the line may be used. Further, the projection optical system does not need to be constituted by a lens, but may be a system using a reflecting mirror. Furthermore, there is no need for a projection optical system,
An exposure apparatus of a contact type or a proximity type may be used. Further, the above-described embodiment may be applied to a so-called scanning type exposure apparatus which performs exposure while moving a reticle stage holding a reticle and a wafer stage holding a wafer in a predetermined scanning direction in synchronization. As a result, the exposure amount can be controlled without being affected by the opening and closing of the shutter, and the time until a stable exposure amount is obtained is shortened, and the throughput is improved.

[0020]

As described above, according to the present invention, the progress of the shutter closing operation is measured, the reference progress is compared with the actual progress, and the operation is shifted according to the deviation of the operation from the reference progress. The output of the light source is increased or decreased. Accordingly, there have been provided a light source output control method capable of accurately stabilizing an integrated exposure amount given to a wafer or the like, and a light source device, an exposure method, and an exposure apparatus using the light source output control method.

[Brief description of the drawings]

FIG. 1 is a schematic view showing a projection exposure apparatus according to one embodiment of the present invention.

FIG. 2 is an explanatory diagram showing a shutter position and a specific output of an integrator sensor during a shutter closing operation period.

FIG. 3 is an explanatory diagram showing variation in progress of a shutter closing operation and variation in specific output of an integrator sensor due to the variation.

FIG. 4 is an explanatory diagram showing a relationship between a position of a shutter and a change ratio of power supplied to a lamp at 3 ms after a close command.

FIG. 5 is a diagram illustrating a case where control according to an embodiment of the present invention is performed.
FIG. 4 is an explanatory diagram showing a shutter position, a specific output of an integrator sensor, and a specific output of a light amount sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Lamp control device 1a ... Storage device 2 ... Mercury lamp 3 ... Elliptical mirror 4 ... Beam splitter 5 ... Lens 6 ... Light amount sensor 8 ... Encoder 9 ... Shutter 10 ... Interference filter 11 ... Input lens 12 ... Fly-eye lens 13 ... Illumination system Aperture stop 13a Aperture stop revolver 14 First relay lens 15 Beam splitter 16 Condenser lens 17 Integrator sensor 18 Projection reticle blind 19 Second relay lens 20 Reticle 21 Reticle pattern 22 Projection lens 23 ... wafer stage 24 ... wafer

Claims (6)

[Claims] 1. A light source output control method for controlling an output of a light source having a shutter, comprising: a shutter position sensor for measuring a position of the shutter; and an output of the light source according to a speed of progress of a closing operation of the shutter. Controlling the light source output. 2. The method according to claim 1, further comprising: measuring a position of the shutter after a lapse of a predetermined time after the command to close the shutter, and controlling an output of the light source based on the position of the shutter after the lapse of the predetermined time. The light source output control method according to claim 1, wherein 3. The output of the light source is controlled such that the integrated light amount passing through the shutter is constant until the shutter is fully closed after the command to close the shutter. The light source output control method according to claim 1 or 2, wherein: 4. A light source device comprising a light source, a light source output control device for controlling the output of the light source, and a shutter for passing and blocking a light beam from the light source, wherein the light source device measures the position of the shutter. A light source output control device configured to control an output of the light source according to a speed of progress of a closing operation of the shutter. 5. An exposure for transferring a pattern on a photosensitive substrate by illuminating a pattern on a projection original with an illumination optical system and forming a light beam transmitted through the pattern on a photosensitive substrate by a projection optical system. In the method, at least a light source, a light source output control device for controlling an output of the light source, a shutter for passing / blocking a light beam from the light source, and a shutter position for measuring a position of the shutter are provided in the illumination optical system. An exposure method, comprising: providing a sensor; and performing the exposure while controlling the output of the light source in accordance with the progress of the closing operation of the shutter by the light source output control device. 6. Exposure for illuminating a pattern on a projection original with an illumination optical system and forming an image of a light beam transmitted through the pattern on a photosensitive substrate by a projection optical system, thereby transferring the pattern onto the photosensitive substrate. In the apparatus, the illumination optical system includes a light source, a light source output control device that controls an output of the light source, a shutter that passes and blocks a light beam from the light source, and a shutter position sensor that measures a position of the shutter. An exposure apparatus, wherein the light source output control device is configured to control an output of the light source in accordance with a speed of progress of a closing operation of the shutter.