JPH09199394A - Illuminating apparatus for exposure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately control the output exposure amount by changing the polarization state of the light from a light source to change the light intensity. SOLUTION: The polarization state of a laser beam L1 from a light source 1 incident on polarization control means 2 is controlled by this polarization control means 2. The polarization control means 2 changes the polarization state of the laser beam L1 by rotating a wavelength plate 5 together with a mount 6 about the optical axis of the laser beam L1. The mount 6 is rotated together with the wavelength plate 5 in a plane perpendicular to the propagation direction of the laser beam L1 by an angle corresponding to a voltage signal from an external controller 7. The light intensity of the laser beam L2 incident on a polarizer 3, which has been transmitted through the wavelength plate 5 of the polarization control means 2, is changed by the polarizer 3 in accordance with the polarization state of the laser beam L2. The laser beam L3, whose light intensity has been changed by the polarizer 3, illuminates an object to be exposed through the illuminating apparatus 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exposure illuminating device used when a semiconductor element is manufactured by using a photolithography technique, and more particularly to accurately controlling the amount of light during exposure. The present invention relates to a novel exposure illumination device that is made possible.

[0002]

2. Description of the Related Art Conventionally, as an exposure illuminator used for exposing a resist when a semiconductor element is manufactured by using a photolithography technique, a short wavelength light is used for fine processing. Light of a certain ultraviolet region, specifically, one that emits g-line or i-line of a mercury lamp is mainly used. In recent years, in order to meet the demand for further fine processing, attempts have been made to use a KrF excimer laser, an ArF excimer laser, or the like that emits light of a shorter wavelength as a light source.

By the way, in a step type projection exposure apparatus (hereinafter referred to as a stepper) which is widely used for manufacturing a semiconductor element, a wafer which is a substrate of the semiconductor element is divided into a plurality of sections, and each section is divided. Expose. Therefore,
When using a stepper, the entire surface of the wafer is exposed by a plurality of exposure steps.

When the stepper is used for the exposure as described above, since the wafer is exposed by a plurality of exposure steps, the exposure amount in each exposure step is uniform so that the exposure amount is not uneven over the entire surface of the wafer. It is important to Specifically, in the current semiconductor element manufacturing process, it is desired that the error in the exposure amount in each exposure step be within 1%.

It is needless to say that accurate control of the exposure amount is important in order to satisfactorily expose the resist even in an exposure apparatus other than a stepper such as a so-called contact exposure apparatus.

As described above, in an exposure apparatus such as a stepper or a contact exposure apparatus, it is important to accurately control the exposure amount, and therefore, an exposure illumination apparatus used in such an exposure apparatus is required. It is required that the light quantity can be adjusted accurately and at high speed.

[0007]

As described above, conventionally, a mercury lamp, an excimer laser, or the like is used as a light source of an exposure illumination device, but these light sources directly change the light emission amount. Is difficult. This is because if the amount of emitted light is directly changed, the oscillation wavelength and the emitted light intensity may change, or the life of the light source may be shortened.

Therefore, in the conventional exposure illumination device, a mechanical shutter that is mechanically closed or opened is inserted in the optical path, and this mechanical shutter is used to perform on / off operation during exposure. . However, with a mechanical shutter, it is difficult to continuously change the amount of light that passes through the mechanical shutter, so it is difficult to accurately control the amount of exposure. In addition, the mechanical shutter has a limitation in high-speed operation, and further has a movable portion that mechanically operates, so that it has a short life and requires periodic maintenance.

As described above, in the conventional illumination device for exposure,
There are various problems in controlling the amount of light at the time of exposure, and there is a demand for an exposure illumination device that can control the amount of light more favorably.

Therefore, the present invention has been proposed in view of such a conventional situation, and an exposure illumination device capable of accurately controlling the light amount at the time of exposure without using a mechanical shutter. Is intended to provide.

[0011]

An exposure illuminator according to the present invention, which has been completed to achieve the above-mentioned object, comprises a light source which emits light in the ultraviolet region having a predetermined polarization state, and Polarization control means for changing the polarization state of the light of,
And a light intensity control unit for changing the intensity of the light from the polarization control unit according to the polarization state.

Here, the light source is, for example, N
Those equipped with a d: YAG laser are preferred. The polarization control means includes, for example, a wavelength plate, which changes the polarization state of light from the light source by rotating the wavelength plate, and an electro-optical modulator. It is preferable to change the polarization state of the light from the light source by changing the applied voltage.

In the above exposure illuminating device, the light source emits light in the ultraviolet region having a predetermined polarization state, and the polarization control means changes the polarization state of the light from the light source. Then, the light intensity control unit changes the intensity of the light whose polarization state has been changed by the polarization control unit, according to the polarization state. That is, in this exposure illumination device, the intensity of the output light is changed by changing the polarization state of the light from the light source, and the mechanical shutter is not required. Further, since the polarization state of light can be easily changed continuously, this exposure lighting device can easily change the intensity of the output light continuously.

The exposure illumination device includes a beam splitter that reflects a part of the light from the light intensity control means, and a photodetector that detects the amount of light reflected from the beam splitter. The polarization control means may be controlled so that the amount of light detected by the photodetector becomes constant. Thereby, the intensity of the output light can be made constant.

Alternatively, the exposure illuminating device includes a beam splitter that reflects a part of the light from the light intensity control means, a photodetector that detects the amount of light reflected by the beam splitter, and the photodetector. And an integrator that integrates the amount of light detected by the container, and the exposure time may be adjusted so that the integrated value of the amount of light integrated by the integrator becomes a predetermined value. As a result, the exposure amount can be made constant even if the intensity of the output light varies.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. Needless to say, the present invention is not limited to the following examples and can be modified without departing from the gist of the present invention.

First Embodiment The exposure illumination apparatus according to the present embodiment is an exposure illumination apparatus that controls the amount of light by controlling the polarization state of laser light from a light source, and is shown in FIG. As described above, the light source 1 that emits the laser light L1 in the ultraviolet region that has a predetermined polarization state, the polarization control unit 2 that controls the polarization state of the laser light L1, and the laser whose polarization state is controlled by the polarization control unit 2 A polarizer 3 that changes the intensity of the light L2 according to the polarization state and an illuminating device 4 that irradiates the exposure target with the laser light L3 whose light intensity is changed by the polarizer 3 are provided.

The light source 1 is equipped with an Nd: YAG laser, generates the fifth harmonic of the Nd: YAG laser, and emits S-polarized ultraviolet light. Here, Nd: YAG
The fifth harmonic of the laser is ultraviolet light having a wavelength of 213 nm.
The laser light L1 of m is emitted.

Then, the laser beam L1 from the light source 1 is incident on the polarization control means 2, and the polarization state is controlled by the polarization control means 2.

Here, the polarization control means 2 has a wavelength of 213n.
1 includes a half-wave plate 5 designed for m light, a mount 6 on which the wave plate 5 is installed, and an external controller 7 that controls the operation of the mount 6.
As indicated by an arrow A in the figure, the polarization state of the laser beam L1 from the light source 1 is changed by rotating the wavelength plate 5 together with the mount 6 about the optical axis of the laser beam L1.

Here, the mount 6 is mounted on the wave plate 5 in a plane perpendicular to the propagation direction of the laser light L1 from the light source 1 at an angle corresponding to the voltage signal from the external controller 7.
Rotate with. That is, the polarization control means 2 can control the rotation angle of the wave plate 5 and the mount 6 by controlling the voltage signal from the external controller 7, whereby the laser light L1 can be controlled.
It is possible to change the polarization state of.

Then, the laser light L2 transmitted through the wave plate 5 of the polarization control means 2 enters the polarizer 3. Here, the polarizer 3 is designed to correspond to light having a wavelength of 213 nm, and the maximum amount of S-polarized light is transmitted on the optical axis of the laser light L2 that has passed through the wavelength plate 5 of the polarization control means 2. The angle is fixed. The polarizer 3 functions as a light intensity control unit and changes the light intensity according to the polarization state of the laser light L2 that has passed through the wavelength plate 5.

Then, the laser light L3 whose light intensity is changed by the polarizer 3 enters the illumination device 4 and is irradiated by the illumination device 4 onto the exposed object.

In the exposure illuminating device as described above, when the rotation angle of the wave plate 5 is θ and the maximum value of the output light amount is I ₀ , the laser light L3 transmitted through the polarizer 3 and output. The intensity I is I = I ₀ cos ² 2θ. That is, in this exposure lighting device, as shown in FIG. 2, the intensity I of the output light changes depending on the rotation angle θ of the wave plate 5. Note that here, the laser light L1 from the light source 1
The rotation angle of the wave plate 5 when the optical axis direction of the wave plate 5 is parallel or perpendicular to the S-polarized light direction is defined as 0 °.

As shown in FIG. 2, when the rotation angle θ of the wave plate 5 is 0 °, the laser light L transmitted through the wave plate 5
Since 2 remains as S-polarized light, the intensity I of the laser light L3 that is transmitted through the polarizer 3 and is output is maximum. Then, when a voltage signal is applied from the external controller 7 to rotate the wave plate 5 together with the mount 6 by an angle θ, the laser light L2 transmitted through the wave plate 5 becomes linearly polarized light with an angle 2θ, whereby the polarizer 3 is rotated. The intensity I of the laser beam L3 that is transmitted and output changes continuously in accordance with the rotation angle θ of the wave plate 5. The rotation angle θ of the wave plate 5 is 45 °.
When, the laser light L transmitted through the polarizer 3 and output is
The intensity I of 3 becomes 0, and it is completely cut off.

As described above, in the exposure lighting apparatus according to the present embodiment, the laser outputted by rotating the wave plate 5 according to the voltage signal from the external controller 7 without using a mechanical shutter. The intensity I of the light L3 is 0
To the maximum value I ₀ can be continuously changed.

Further, in this exposure illuminating device, since the intensity I of the laser beam L3 to be output can be continuously changed, not only the on / off switching at the time of exposure but also the light at the time of exposure can be performed. It is also possible to change the intensity I of the image with time. That is, when the exposure pulse is applied to the object to be exposed by simply switching it on / off during the exposure, the time shape of the exposure pulse becomes a rectangular pulse. Since it can be changed with time, the exposure pulse can have an arbitrary pulse shape. Therefore, in this exposure illumination device, when the resist is exposed, it is possible to reduce the light intensity I in the latter half of the exposure, for example, according to the characteristics of the resist.

As described above, the method of controlling the intensity of light by rotating the wave plate is effective only when a light source that emits polarized light is used, and a mercury lamp or an excimer is used. This is not applicable when using a light source that emits unpolarized light such as a laser.

Second Embodiment In the exposure illumination device according to the present embodiment, the light source 1, the polarization control means 2, the polarizer 3 and the illumination device 4 are the exposure illumination device according to the first embodiment. The device has the same configuration as that of the device, but further reflects a part of the laser beam L3 transmitted through the polarizer 3 and output as shown in FIG. 3 in order to sample the intensity of the laser beam L3 output. And a photodetector 12 that detects the amount of reflected light L4 from the beam splitter 11.

Here, the beam splitter 11 is arranged on the optical axis of the laser beam L3 which is output by passing through the polarizer 3. On the other hand, the photodetector 12 functions as a photodetector that detects the light amount of the reflected light L4 from the beam splitter 11, and is arranged on the optical axis of the reflected light L4 reflected by the beam splitter 11.

In this illuminating device for exposure, a part of the laser beam L3 transmitted through the polarizer 3 and output is reflected by the beam splitter 11, and the reflected beam L4 is detected by the photodetector 12. Here, the photo detector 12 supplies a signal indicating the detected light amount to the external controller 7. Then, the external controller 7 automatically controls the rotation angle θ of the wave plate 5 based on the signal from the photodetector 12 so that the amount of light detected by the photodetector 12 becomes constant. As a result, the intensity of the laser light L3 output from the exposure illumination device during exposure is constant regardless of the variation in the intensity of the laser light L1 output from the light source 1.

Then, for example, when this exposure illumination device is applied to a stepper to expose a wafer, as described above, the intensity of the laser beam L3 output from the exposure illumination device during exposure becomes constant. As described above, while automatically controlling the rotation angle θ of the wave plate 5, the exposure is turned on / off in accordance with the movement cycle of the wafer. Here, the exposure is turned on / off by rotating the wave plate 5 with a constant time width.

An example of a temporal change in the intensity of the laser beam L1 output from the light source 1 when the exposure is performed in this manner is shown in FIG.
As shown in (1), at this time, an example of the time change of the intensity of the laser beam L3 output from this exposure illumination device, that is, an example of the exposure pulse by this exposure illumination device is shown in FIG.
This is shown in (2).

As described above, when the intensity of the laser beam L1 output from the light source 1 fluctuates relatively slowly,
The product of the light intensity and the exposure time at the time of exposure is obtained by performing exposure for a fixed time t1 while automatically controlling the intensity of the laser light L3 output from the exposure illumination device to a constant level I _out. That is, the exposure energy can be kept constant. Therefore, by performing the exposure as described above, the energy of the exposure pulse becomes constant, and it is possible to perform the uniform exposure over the entire surface of the wafer without causing unevenness in the exposure amount.

In this way, in the method of automatically controlling the intensity of the laser beam L3 output from the exposure illuminating device, the time constant of the variation of the intensity of the laser beam L1 from the light source 1 is the wafer movement period (usually It is particularly suitable when it is sufficiently longer than a few seconds or less).

Third Embodiment The exposure illuminator according to the present embodiment comprises a light source 1, a polarization control means 2, a polarizer 3, an illuminator 4, and a beam splitter 1.
1 and the photodetector 12 are configured similarly to the exposure illumination apparatus according to the second embodiment, but as shown in FIG. 5 in order to detect the integrated value of the laser light L3 to be output. , And an integrator 13 that integrates the amount of light detected by the photodetector 12.

In this exposure illuminating device, the photodetector 12 supplies a signal indicating the detected light amount to the integrator 13. Then, the integrator 13 has the photodetector 1
The light amount detected by the photodetector 12 is integrated based on the signal from 2, and when the integrated value reaches a certain value, a trigger signal is generated and supplied to the external controller 7. When receiving the trigger signal from the integrator 13, the external controller 7 generates a voltage signal that rotates the mount 6 by 45 °. This allows
The wave plate 5 rotates by 45 ° together with the mount 6, and as a result, the laser light L output from this exposure illumination device is generated.
The intensity of 3 becomes zero, and the exposure ends.

As described above, in this exposure illuminator, since the integrator 13 can obtain the integral value of the exposure amount in real time, the exposure energy is adjusted by adjusting the exposure time based on the integral value. Can be controlled to a predetermined value.

Then, for example, when the wafer is exposed by applying this exposure illuminating device to a stepper, the integrator 13 obtains an integral value of the exposure amount in real time as described above, and the integral value is obtained. While adjusting the exposure time so as to be constant, the exposure is turned on / off in accordance with the movement cycle of the wafer.

Here, the laser light L output from the light source 1
6 (1) shows an example of the time change of the intensity of 1
At this time, FIG. 6B shows an example of a temporal change in the intensity of the laser beam L3 output from the exposure illumination device, that is, an exposure pulse generated by the exposure illumination device. These Figure 6
As shown in (1) and FIG. 6 (2), when the exposure is performed in this way, even if the temporal change in the intensity of the laser light L1 output from the light source 1 is large, the laser light output from the light source 1 is large. Since the exposure time is adjusted according to the time change of the intensity of L1, the energy of each exposure pulse becomes constant.

That is, in this method, since the exposure time is adjusted on the basis of the integral value of the exposure amount,
Even if the intensity of the laser beam L1 output from the light source 1 is unstable, the energy of the exposure pulse can be controlled extremely accurately.

Therefore, by performing the exposure as described above, the energy of the exposure pulse becomes constant irrespective of the fluctuation of the intensity of the laser beam L1 output from the light source 1, and the exposure amount does not vary, and the entire surface of the wafer is covered. It is possible to perform uniform exposure.

In this method of adjusting the exposure time, the intensity of the laser beam L1 from the light source 1 is unstable,
It is particularly effective when the intensity fluctuation within the exposure time (usually 1 second or less) cannot be ignored.

Fourth Embodiment As shown in FIG. 7, the exposure lighting apparatus according to the present embodiment uses an electro-optic modulator 21 to control the polarization state of the laser light L1 from the light source 1. The polarization control means 20 is provided. Except for the polarization controller 20, it has the same configuration as the exposure illumination device according to the first embodiment.

The polarization control means 20 includes an electro-optic modulator 21 and a laser beam L output from the electro-optic modulator 21.
A quarter-wave plate 22 arranged on the optical axis of a and a modulator driver 2 for controlling the voltage applied to the electro-optic modulator 21.
3 is provided.

Here, the electro-optic modulator 21 is provided with an electro-optic crystal and is arranged so that the laser light L1 from the light source 1 is incident on the electro-optic crystal. Further, the voltage from the modulator driver 23 is adapted to be applied to this electro-optic crystal. Here, the electro-optic modulator 21
The electro-optic crystal used in the above must be transparent to ultraviolet rays, and for example, KH ₂ PO ₄ (KDP), NH
₄ H ₂ PO ₄ (ADP) or β-BaB ₂ O ₄ (β-
BBO) or the like can be used.

Then, the laser beam L1 from the light source 1 is incident on the electro-optic crystal of the electro-optic modulator 21, undergoes the electro-optic effect and the phase delay amount is changed, and then the electro-optic crystal is emitted. It is transmitted and output. Here, the amount of phase delay due to the electro-optic effect changes in proportion to the voltage applied to the electro-optic crystal. That is, the laser light L1 from the light source 1 has a phase delay amount that changes in accordance with the voltage applied from the modulator driver 23 to the electro-optic modulator 21.

Then, the laser light La whose phase delay amount is changed in this way enters the quarter-wave plate 22. Here, when the phase delay amount of the laser light La output from the electro-optic modulator 21 is θ, the light transmitted through the quarter-wave plate 22 becomes linearly polarized light with an angle θ.

That is, in the polarization control means 20, it is possible to control the polarization state of the laser light L1 from the light source 1 by controlling the voltage applied from the modulator driver 23 to the electro-optic modulator 21. As a result, the same operation as the rotation of the half-wave plate 5 in the first embodiment can be obtained.

The intensity of the laser light L2 whose polarization state is controlled by the polarization control means 20 is changed by the polarizer 3 as in the exposure illumination device according to the first embodiment. Then, the light is incident on the lighting device 4.

Here, the electro-optic modulator 21 can be operated at a very high speed. Therefore, this illuminating device for exposure uses the laser beam L3 that is output at extremely high speed.
It is possible to change the intensity of. Specifically, for example, the rise time of the laser beam L3 output at the start of exposure can be set to 10 ns or less.

In addition, this exposure illuminating device uses the electro-optic modulator 21 for controlling the intensity of the output laser beam L3, and since there is no mechanically driven portion, the life of the device is long. , Maintenance is almost unnecessary.

When an electro-optic modulator is used as the polarization control means as in this embodiment, it goes without saying that, as in the second embodiment, a photodetector is used to output light. The intensity of the laser light emitted may be constant, or the exposure time may be adjusted by using an integrator as in the third embodiment.

By the way, in the first to fourth embodiments, as the light from the light source, the fifth Nd: YAG laser is used.
Although the harmonic is used, the fourth harmonic having a wavelength of 266 nm may be used. Further, the light source may be any one as long as it emits light of a specific polarization state, and is not limited to one using an Nd: YAG laser. Further, in the first to fourth embodiments, the light from the light source is S-polarized, but the light from the light source only needs to be in a specific polarization state, and is circularly polarized light, linearly polarized light, or elliptically polarized light. Etc. can also be used.

[0055]

As is apparent from the above description, in the exposure illuminator according to the present invention, the intensity of the output light is changed by changing the polarization state of the light from the light source. The intensity of the output light can be continuously changed without using it, and the exposure amount can be accurately controlled.

In particular, when an electro-optic modulator is used as the polarization control means, there is no mechanically driven part, so that the life of the device is prolonged, and the intensity of the output light can be changed extremely rapidly. Is possible.

[Brief description of drawings]

FIG. 1 is a schematic diagram showing a configuration example of an exposure illumination device to which the present invention has been applied.

FIG. 2 is a diagram showing a relationship between an intensity I of output light and a rotation angle θ of a wave plate.

FIG. 3 is a schematic diagram showing another configuration example of an exposure illumination device to which the present invention has been applied.

FIG. 4 is a diagram showing an example of a temporal change in intensity of laser light output from a light source and a temporal change in laser light output from an exposure illumination device.

FIG. 5 is a schematic diagram showing another configuration example of an exposure illumination device to which the present invention has been applied.

FIG. 6 is a diagram showing an example of temporal changes in intensity of laser light output from a light source and temporal changes in laser light output from an exposure illumination device.

FIG. 7 is a schematic diagram showing another configuration example of an exposure illumination device to which the present invention has been applied.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 light source 2 polarization control means 3 polarizer 4 illuminating device 5 half wave plate 6 mount 7 external controller 11 beam splitter 12 photodetector 13 integrator 20 polarization control means 21 electro-optic modulator 22 quarter wave plate 23 modulation Driver

Claims (6)

[Claims] 1. A light source that emits light in the ultraviolet region having a predetermined polarization state, a polarization control unit that changes the polarization state of the light from the light source, and a polarization state that changes the intensity of the light from the polarization control unit. And a light intensity control unit for changing the light intensity according to the above. 2. The exposure illumination device according to claim 1, wherein the light source includes an Nd: YAG laser. 3. The exposure illuminator according to claim 1, wherein the polarization control means includes a wave plate, and the polarization state of the light from the light source is changed by rotating the wave plate. . 4. The polarization control means comprises an electro-optic modulator, and changes the polarization state of the light from the light source by changing the voltage applied to the electro-optic modulator. Item 2. The exposure illumination device according to item 1. 5. A beam splitter that reflects a part of the light from the light intensity control means, and a photodetector that detects the amount of light reflected by the beam splitter are detected by the photodetector. 2. The exposure illuminating device according to claim 1, wherein the polarization control means is controlled so that the amount of light becomes constant. 6. A beam splitter that reflects a part of the light from the light intensity control means, a photodetector that detects the amount of light reflected from the beam splitter, and a light amount that is detected by the photodetector. 2. An exposure illuminator according to claim 1, further comprising an integrator for integrating, wherein the exposure time is adjusted so that an integrated value of the light amount integrated by the integrator becomes a predetermined value.