JPS6370421A - Exposure device - Google Patents

Abstract

PURPOSE:To extend life time of an exposure light source and to obtain an inexpensive and accurate exposure device, by utilizing as an alignment light source a successive light-emitting light source having a wavelength approximately equal to an exposure wavelength of an excimer laser. CONSTITUTION:In order to align a registering mark 20 on a reticle 8 with a reference mark 5 on a stage 4 and an alignment mark 26 on a wafer 6, illumination light from a low pressure mercury lamp 17 as an alignment light source is passed through optical fibers 16 to reach a filter 27. The filter 27 selects therefrom only a wavelength approximately equal to an exposure wavelength. Thus, it becomes possible to use an excimer laser 14 only for exposure and to extend the life time of the laser. Further, since a wavelength close to the exposure wavelength is used for alignment, the alignment can be carried out accurately without difference in lens distortion or deviation in focus.

Description

Detailed Description of the Invention (Technical Field of the Invention) The present invention relates to an excimer laser (Excimer L).
The present invention relates to an exposure apparatus that exposes a pattern on a reticle onto a wafer using a wafer.

(Background of the Invention) In recent years, exposure apparatuses have been proposed that use an excimer laser, which is a type of pulsed laser, as an exposure light source.

These exposure devices photoelectrically detect and align the alignment marks on the reticle and the wafer, and then expose the pattern on the reticle onto the wafer using an excimer laser. It is.

As a positioning method performed prior to exposure, an excimer laser is also used as a light source for positioning, and alignment is performed in synchronization with pulse waves from the excimer laser, or a method different from the excimer laser is used. A method has been proposed in which alignment is performed using a light source that emits light of a certain wavelength.

However, since the former uses the same light source for exposure and alignment, it has the disadvantage of shortening the life of the excimer laser as the exposure light source, while the latter uses different wavelengths for exposure and alignment, so it corrects chromatic aberration of the projection lens. Even if this is done, the distortion map is different for the two wavelengths, and the lens distortion is added as an offset for alignment, resulting in a decrease in alignment accuracy.

(Objectives of the Invention) It is an object of the present invention to solve these drawbacks, extend the life of the exposure light source, and provide an exposure apparatus that is inexpensive and has good alignment accuracy.

(Summary of the Invention) The present invention photoelectrically detects and aligns alignment marks on a reticle and a wafer, and then exposes a pattern on the reticle onto the wafer using an excimer laser. The exposure apparatus is characterized in that a continuous light source having a wavelength substantially equal to the exposure wavelength by the excimer laser is used as the light source for alignment, and the continuous light source is A better embodiment is obtained by using a low pressure mercury lamp.

(Embodiment) FIG. 1 shows an embodiment of the present invention, in which a pulse wave from an excimer laser 14 controlled by a laser control device 15 is expanded to an appropriate size by a diverging lens 13, and an integrator is transmitted by an objective lens 12. I am led to 11.

The integrator 11 makes the illumination light uniform, and the mirror 10
The reticle 8 is illuminated from behind by the condenser lens 9. The pattern of reticle 8 is projected onto wafer 6 by projection lens 7 . The control device 1 monitors the position of the stage 4 measured by the interferometer 2, sends a control signal to the drive device 3 to move the stage 4, repeats step-and-repeat, and synchronizes with the operation of the stage to control the laser control device. The same pattern on the reticle 8 is printed onto the wafer 6 by inputting a driving command for the excimer laser 14 to the reticle 15 and causing the excimer laser 14 to emit light. Furthermore, in order to align the alignment mark (reticle mark) 20 on the reticle 8, the standard mark 5 on the stage 4, and the alignment mark (wafer mark) 26 on the wafer 6, a low-pressure mercury lamp is used as a light source for alignment. The illumination light from 17 passes through the optical fiber 16 and is filtered by a filter 27 where only wavelengths near (almost equal to) the exposure wavelength are selected.

The light selected by the filter 27 passes through the objective lens 24 and half mirrors 23 and 22, and illuminates the reticle mark 20 by the mirror 21. Stage 4 with this lighting
The upper standard mark 5 and wafer mark 26 are also connected to the projection lens 7.
The return light from those marks passes through the projection lens 7, reticle 8, mirror 21, objective lens 22, is reflected by the half mirror 23, passes through the lens 25, and is imaged on the imaging surface of the ITV camera 18. do. As a result, as is well known, a video signal as shown in FIG. 2(b) is obtained,
The amount of positional deviation between the two reticle marks 20 and the standard mark 5 or wafer mark 26 shown in FIG. The alignment is completed by feeding back to the drive device 3 to make the positional deviation amount zero. In addition, in the formula expressing the above-mentioned positional deviation amount, RR is the distance from the reference position to the approximate center of the right reticle mark RR, and RL is the distance from the reference position to the approximate center of the left reticle mark RL. indicates the distance to the center of

Similarly, <WR is the distance from the reference position to the right edge of the wafer mark W, and WL is the distance from the reference position to the left edge of the wafer mark W, and the distance from the center of the mark W. Therefore, the left and right reticle marks RR,
It represents the amount of deviation between the center of RL and the center of wafer mark W.

Because of this structure, the excimer laser 14 only needs to be used for exposure, which can extend its lifespan.Also, since light near the exposure wavelength is used as the alignment wavelength, it is possible to reduce the interaction of lens distortion. On the other hand, there is an advantage in that highly accurate positioning can be performed without causing defocus.

For alignment, use the reticle mark width RR-RL (RR and RL
The sampling value is calculated in microns using the design value (length between the two) as the design value. In other words, when the reticle mark width is expressed by point A, the length per point is ±B (μm
/point) and multiplying the amount of deviation found in points by B to find the amount of deviation in μm. For alignment, (RR+RL)/2-(Wt, +wR)/2 is reported to the control device 1 as the amount of alignment deviation.

(Effects of the Invention) As described above, according to the present invention, since the excimer laser is not used for alignment, there is not only the advantage that the life of the excimer laser can be extended without extending the life of the excimer laser, but also the pulse control of the laser Since it is only necessary to correspond to the above, the effect of simplifying the configuration can be expected. Furthermore, if the alignment wavelength is different from the exposure wavelength, not only will accuracy deteriorate, but the projection lens must also have a complex structure that transmits both wavelengths. If a substantially equal wavelength is used as the alignment wavelength, accuracy is high and a projection lens with a simple structure can be used. Furthermore, if the alignment mark is irradiated with an excimer laser and the resist is exposed to light before alignment is performed in the present invention, the resist will be exposed to light during alignment, its refractive index will change, and the alignment waveform will change. This is effective because it eliminates the need for waiting time for exposure to light for alignment, thereby reducing alignment time.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an embodiment of the present invention, and FIG. 2 is an I
FIG. 3 is a diagram showing the overlap between the reticle mark and the wafer mark on the imaging surface of the TV camera (a) and the signal waveform obtained from one scanning line of the IT camera (b) in correspondence. (Explanation of symbols of main parts)

Claims (2)

[Claims] (1) An exposure device that photoelectrically detects and aligns the alignment marks on the reticle and the wafer, and then exposes the pattern on the reticle onto the wafer using an excimer laser. An exposure apparatus characterized in that a continuous light source having a wavelength substantially equal to the exposure wavelength by the excimer laser is used as the light source for the alignment. (2) The exposure apparatus according to claim (1), wherein the continuous light source is a low-pressure mercury lamp.