JPH0795508B2 - Exposure equipment - Google Patents

Description

The present invention relates to an exposure apparatus for manufacturing a semiconductor device using a pulsed excimer laser as a light source.

(Prior Art) In an exposure apparatus conventionally known as a stepper,
A mercury lamp is used as the light source, and the light from the mercury lamp is uniformly illuminated on the reticle by the exposure illumination system, and the illuminated reticle pattern is imaged on the wafer mounted on the wafer stage by the imaging lens. I am trying.

Further, as alignment measuring means for aligning the reticle and the wafer, a part of the light from the mercury lamp is split as alignment light and the alignment mark on the wafer or the fiducial mark provided on the wafer stage is irradiated by the imaging lens. However, the alignment position is measured from the received light output by the reflected light of the alignment mark.

(Problems to be Solved by the Invention) However, in such a conventional exposure apparatus,
As the microfabrication of semiconductor devices has progressed, the wavelength of mercury lamps has become longer, so there has been a limit to miniaturization.

Therefore, in recent years, practical use of excimer lasers has been promoted as a light source for shortening the wavelength of illumination light.

However, as is well known, the excimer laser is a pulse laser that oscillates pulsed light, and for example, a trigger circuit generates a trigger signal at regular intervals to cause pulsed light emission. Therefore, when a part of the pulsed light from the excimer laser is divided into alignment light, alignment measurement synchronized with the timing at which the alignment light is obtained is required, and movement of the wafer stage and alignment detection for alignment measurement are required. There is a problem in that the storage of signals and the like must be synchronized with an external trigger signal, and the conventional alignment measurement process must be changed so as to be compatible with trigger synchronization.

(Means for Solving Problems) The present invention has been made in view of such a situation, and in an exposure apparatus using a light source that emits light in a pulsed manner such as an excimer laser, one of the light from the light source is used. It is an object of the present invention to provide an exposure apparatus capable of appropriately performing trigger control of light emission timing for using a part as alignment light depending on alignment measurement processing.

To achieve this object, in the present invention, a position coordinate pulse obtained from a position detecting means such as an interferometer for measuring the position of the wafer stage at the time of alignment measurement is used as a reference for pulse emission of a light source and alignment measurement. The pulse is used as a pulse, and the trigger control for pulse-emitting the light source based on the reference pulse and the process of fetching the alignment detection signal as data are performed.

(Operation) According to the exposure apparatus of the present invention as described above, the position coordinate pulse obtained by the alignment measurement is used as a reference pulse to oscillate the excimer laser and store the alignment detection signal. Since there is no time lag in data acquisition and the excimer laser trigger is based on the reference pulse obtained in alignment measurement, it is possible to control the excimer laser emission centering on the alignment measurement processing operation. Alignment position measurement using a light source that emits light in a pulsed manner can be performed with almost no change in function.

(Embodiment) FIG. 1 is a system block diagram showing an embodiment of the present invention.

First, the configuration will be described. 1 is a light source that emits light in a pulsed manner, and specifically, an excimer laser is used. Light source 1
The illumination light SL emitted by the pulsed light emission is separated into the illumination light SL ′ reflected by the half mirror 2 and the alignment light AL transmitted through the half mirror 2. The illumination light SL ′ is made uniform illumination light by the optical system 3 and illuminated on the reticle R.
On the other hand, the alignment light AL transmitted through the half mirror 2 is
An image is formed on the reticle R through the mirror 4, the beam shaping optical system 5, the beam splitter 6, the objective lens 7, and the mirror 8. Alignment light AL transmitted through reticle R
Passes through the image forming lens 9 and is re-imaged on the surface of the wafer W placed on the wafer stage 10.

In addition to the wafer W, a fiducial mark FM serving as a reference for alignment and a slit-shaped photoelectric conversion element 11 are mounted on the wafer stage 10 at the same height as the wafer W. The returned light by re-imaging on the wafer W surface or the fiducial mark FM is backlit by the optical system, passes through the beam splitter 6, and then is placed in a position conjugate with the pupil position 9a of the imaging lens 9. Only the necessary signal component is transmitted by the filter 12, and then an image is formed on the photoelectric conversion element 14 by the condenser lens 13. After the alignment signal photoelectrically converted by the photoelectric conversion element 14 is amplified by the preamplifier circuit 15,
It is input to the A / D conversion circuit 16. The alignment signal A / D converted by the A / D conversion circuit 16 is stored in the memory circuit 17, and then the microcomputer 18 and the arithmetic processor 19 are provided.
The signal is processed by using, and the alignment position is obtained.

Furthermore, in this embodiment, in addition to the alignment system by the alignment light AL that separates the illumination light SL from the light source 1 that emits light in a pulsed manner, another light source (for example, He-Ne laser, etc.)
An alignment system using the alignment light AL 'from is installed. Alignment light from this separate light source AL ′
Is a beam splitter 18, objective lens 19, mirrors 20,2
1. An image is formed on the wafer W surface through the imaging lens 9. The return light from the alignment mark on the wafer W surface or the fiducial mark FM is reflected by the optical system and reflected by the beam splitter 18, and then the pupil position of the imaging lens 9 is reached.
The spatial filter 22 arranged at a position conjugate with 9a transmits only the necessary signal component, and then the condenser lens 23 is used for photoelectric conversion element 24.
Imaged above. The alignment signal photoelectrically converted by the photoelectric conversion element 24 is amplified by the preamplifier circuit 25 and then processed in the same manner as in the case of the alignment light AL. The alignment signals from the two systems of alignment devices obtained by using the alignment lights AL and AL 'are synchronized with the up / down pulse generated by the interferometer 26 for stage coordinate measurement every time the wafer stage 10 is moved by a certain distance. Then, the signal is processed. That is, the number of pulses is counted in the stage controller 27 in synchronization with the up / down pulse generated by the interferometer 26,
At the same time that the address of the memory circuit 17 is generated, a start pulse for A / D conversion in the A / D conversion circuit 16 is generated. Further, the pulse from the stage controller 27 based on the up / down pulse generated in the interferometer 26 is also input to the trigger device 28 that oscillates the light source 1, and the trigger device 28 causes the stage controller 27 to up / down the interferometer 26. Each time the pulse synchronized with the pulse is received, the light source 1 using the excimer laser is triggered to make the illumination light SL emit light in a pulsed manner.

Next, the operation of the above embodiment will be described.

For alignment of the wafer W placed on the wafer stage 10, when the stage controller 27 outputs a control signal to the drive motor 30 of the wafer stage 10 and starts moving the wafer stage 10, the wafer stage 10 moves a certain distance. Each time, the interferometer 26 generates an up pulse or a down pulse depending on the moving direction. The coordinate position pulse from the interferometer 26 is given to the stage controller 27, and the trigger device
A pulse is input to 28 to cause the light source 1 to emit a pulse. A part of the illumination light SL obtained by the pulsed light emission of the light source 1 passes through the half mirror 2 to become the alignment light AL, and is imaged on the wafer W surface or the fiducial mark FM by the optical system of the alignment light AL. The returned light is backlit through the optical system, converted into an alignment signal by the photoelectric conversion element 14, amplified by the preamplifier circuit 15, and input to the A / D conversion circuit 16. At this time, the stage controller 27 moves the A / D conversion circuit 16
Since the A / D conversion start pulse is applied to the alignment signal from the photoelectric conversion element 14, the alignment signal is A / D converted in synchronization with the pulse emission of the light source 1, and the stage controller 2
In the case of 7, the address of the memory circuit 17 is specified by counting the position coordinate pulse from the interferometer 26.
The alignment signal A / D converted by the D conversion circuit 16 is the light source 1
The data is stored in the designated address of the memory circuit 17 in synchronization with the pulse emission of. Wafer stage 10
The pulse light emission of the light source 1 and the storage processing of the alignment signal are repeated every time when is moved by a certain distance. The alignment position is obtained by signal processing using 19. As described above, in the present invention, since the light emission control of the light source 1 using the excimer laser and the storage of the alignment signal are performed by using the position coordinate pulse obtained by the movement of the wafer stage as the reference pulse, the pulse light emission of the light source 1 is performed. Since there is no time lag in capturing the alignment signal and no measurement error occurs, accurate alignment measurement can be performed.

Alignment light AL from the light source 1 that emits light in a pulsed manner
The operation of providing two alignment devices for the alignment light AL 'by another light source will be described.

Since the two types of alignment lights AL and AL 'have different wavelengths and optical systems, when the fiducial mark FM mounted on the wafer stage 10 is used to measure the reference alignment mark position by each alignment device, this measurement is performed. The offset amount generated between the alignment devices can be obtained from the result. In this case, since both alignment devices perform coordinate measurement using the pulse of the interferometer 26 of the same wafer stage 10, the offset amount can be obtained with high accuracy. By correcting the alignment position by using the offset amount generated between the two alignment devices, it is possible to obtain extremely high alignment accuracy as compared with the alignment by the single alignment device. Furthermore, by using both alignment devices properly according to the process state of the wafer W surface, accurate alignment becomes possible.

Next, the processing operation using the slit-shaped photoelectric conversion element 11 placed on the wafer stage 10 will be described.

The slit-shaped photoelectric conversion element 11 mounted on the wafer stage 10 can measure the beam width of the alignment light AL or AL ′ imaged on the wafer W surface by scanning the wafer stage 10. It is like this. The signal photoelectrically converted by the photoelectric conversion element 11 is amplified by the preamplifier circuit 29, and then, similarly to the case of the alignment apparatus, in synchronization with the position coordinate pulse of the interferometer 26, the A / D conversion circuit 1
After A / D conversion in 6 and storage in the memory circuit 17, signal processing is performed.

Here, since the slit-shaped photoelectric conversion element 11 has a very narrow width, the width of the beam imaged on the wafer W surface can be measured with high accuracy, and therefore the slit on the reticle R is transmitted. When the beam width is measured and the beam center is determined, the slit position of the reticle R is relatively determined, and the alignment measurement of the reticle R can be performed.

Further, if the wafer stage 10 is moved in the Z-axis direction (height direction) by a constant distance and the beam width at each moving height is measured to find the height at which the beam width is minimum, the imaging lens 9
The best focus position of the wafer W surface can be obtained by

Further, by providing slit windows on the reticle R at several places for illumination, and measuring the slit image formed through the imaging lens 9 using the slit photoelectric conversion element 11,
The distortion of the imaging lens 9 can be determined by determining the imaging interval of each slit image.

Furthermore, if the image forming interval of the two slits on the reticle R is regularly measured, the magnification variation of the image forming lens 9 can also be measured.

In the above-described embodiment, the reference pulse for capturing the alignment signal at the same time as triggering the light source 1 to emit the pulse is used as the reference pulse generated from the interferometer 26 for measuring the coordinate position of the wafer stage 10. However, if the pulse from the interferometer that measures the position coordinates of the reticle stage is used as the reference pulse, it can be similarly applied to the alignment measurement of the reticle.

(Effects of the Invention) As described above, according to the present invention, the timing of capturing the alignment signal in synchronization with the pulse of the interferometer of the wafer stage and the timing of the oscillation trigger of the illumination light source using an excimer laser or the like are set. Because I tried to take
Since there is no time lag between the emission of the illumination light and the alignment measurement and no measurement error occurs, it is possible to perform accurate alignment measurement.

Also, since the light source emits a pulsed light with a position coordinate pulse synchronized with the movement of the wafer stage for alignment measurement, the light emission of the light source can be controlled in a pulsed manner centering on the alignment measurement processing operation, and the excimer laser emits light in a pulsed manner. Even if a light source such as the above is used for the alignment light, accurate alignment measurement can be performed without changing the function of the conventional alignment apparatus.

[Brief description of drawings]

FIG. 1 is a system block diagram showing an embodiment of the present invention. 1: Light source (excimer laser) 2: Half mirror 3: Optical system (for uniform illumination) 4,8,20,21: Mirror 5: Beam shaping optical system 6,18: Beam splitter 7,19: Objective lens 9: Connection Image lens 10: Wafer stage 11: Slit-shaped photoelectric conversion element 12, 22: Spatial filter 13,23: Condenser lens 14, 24: Photoelectric conversion element 15, 25, 29: Preamplifier circuit 16: A / D conversion circuit 17 : Memory circuit 18: Microcomputer 19: Dedicated processor 26: Interferometer 27: Stage controller 28: Trigger device 30: Stage drive motor R: Reticle W: Wafer FM: Fiducial mark

Claims (2)

[Claims] 1. An exposure apparatus for forming an image of a reticle pattern on a wafer by exposure with illumination light from a light source that emits light in a pulsed manner, and dividing a part of the illumination light from the light source as alignment light. Alignment signal detecting means for forming an alignment signal by receiving reflected light from an alignment mark on the wafer by forming an image on the wafer; position detecting means for generating coordinate position pulse in response to movement of the wafer stage; Trigger means for pulsatingly driving the light source in synchronization with the coordinate position pulse of the position detecting means; Storage means for storing the alignment signal in synchronization with the position coordinate pulse of the position detecting means; Position measuring means for measuring the alignment position based on the stored signal of the coordinate position pulse from the position detecting means. Is used for both the light emission trigger of the light source and the storage operation of the storage means. 2. A pulse light source for illuminating a reticle with pulsed illumination light, an image forming optical system for forming an image of the pattern of the reticle, and a substrate on which the imaged pattern is exposed. A part of illumination light from the pulse light source in an exposure apparatus including a movable stage having a reference mark at a position different from that of the substrate, and an interferometer that outputs a pulse signal according to the movement of the movable stage. An optical splitter that splits the first alignment light as the first alignment light; irradiating the reticle with the first alignment light, irradiating the reference light with the transmitted light through the imaging optical system, and the reference mark. First alignment detecting means for photoelectrically detecting return light from the optical system through the imaging optical system and the reticle; another light source for outputting second alignment light having a wavelength different from that of the pulse light source. Irradiating the substrate or the reference mark with the second alignment light and photoelectrically detecting return light from the mark on the substrate or the reference mark
The alignment detection means of the;
Trigger means for driving the pulsed light source to emit light in synchronism with the pulse signal from the interferometer when detecting by each of the second alignment detecting means; each of the first and second alignment detecting means And a signal processing means for determining the position of the reference mark by processing both signals by capturing a signal photoelectrically detected by the pulse signal from the interferometer. An exposure apparatus, which is used as both a light emission trigger of the pulse light source and a signal acquisition of the signal processing means.