JPS63117421A - Exposure device - Google Patents

Abstract

PURPOSE:To effectively use light which is even emitted continuously from a light source so that effective use and high throughput of energy can be achieved, by forming a resist removal optical means, in which laser beam is guided on an alignment mark of a wafer when exposure of a reticle pattern is not performed on the wafer, so that the resist on an alignment mark is vaporized by radiation of laser beam emitted from the exposure light source. CONSTITUTION:Light emitted from a light source 1 is reflected on a movable reflector 2 and further reflected on a reflector 9 and it reaches a shutter 11. When the movable reflector 2 is in a position shown in a solid line, the shutter is opened for a time required to remove a resist, and so the resist is vaporized. During the removal of the resist, position alignment of a wafer 25 is performed. When the shutter 11 is closed, the movable reflector 2 is moved up and the light reaches a shutter 3. When the position alignment of the wafer 25 is completed, the shutter 3 is opened for a fixed time. Light which transmits the shutter 3 passes through a condenser 6 and it illuminates a reticle 7. Then a pattern of the reticle 7 is transcribed on a prescribed chip of the wafer 25.

Description

[Detailed description of the invention] (Industrial application field) The present invention relates to an exposure apparatus.

(Prior art) In recent years, in the process of manufacturing glue for semiconductor devices, 4
There is a growing demand for an exposure apparatus that has alignment accuracy and resolution that can withstand the production of M-bit and 16-Mbit memories. Most of this type of exposure equipment exposes the semiconductor wafer by overlapping the circuit pattern of the mask (or reticle) many times, but the mask (or reticle) and wafer, which mainly determine the overlay accuracy, The alignment accuracy with the wafer varies greatly depending on how precisely the position of the alignment mark formed on the wafer is detected. Typically, wafer alignment is performed by irradiating an alignment mark with light and photoelectrically detecting reflected light, scattered light, diffracted light, etc. from the mark. However, since a resist is necessarily applied to the wafer before exposure, the alignment mark is detected through the resist layer (about 1 to 2 μm thick). Furthermore, since the resist layer has a minute step structure in the area and the implant mark, it is inevitable that the film thickness will be non-uniform around the mark. For this reason, the optical information generated from the alignment mark is weakened by the influence of the resist layer.
Alignment accuracy (mark position detection accuracy) tends to decrease due to interference effects inherent to thin films becoming noticeable near the mark, or asymmetrical unevenness in resist film thickness on both sides of the mark.

Furthermore, when using a multilayer resist to miniaturize patterns on a wafer, the alignment mark itself may become optically invisible under illumination light of the exposure wavelength, so alignment accuracy cannot be ensured. had become quite a difficult problem.

Therefore, a laser light source that emits laser light having a wavelength and energy capable of vaporizing the resist layer is provided separately from the exposure light source, and the resist layer on the alignment mark is removed using this laser light.

[Problem that the invention seeks to solve]

In the conventional technology described above, as a simple exposure device, laser light is not needed except during exposure, so either: ■ The shutter must be closed while the laser continues to oscillate, or
(2) It is conceivable to stop laser oscillation at times other than during exposure, but in (2) it is a waste of energy, and in (2) the throughput decreases by the time required to start the laser. The object of the present invention is to eliminate these drawbacks and provide a projection exposure apparatus with low running costs and high throughput.

(Means for Solving the Problems) In order to solve the above problems, in the present invention, when the pattern of the reticle is not exposed to the wafer, the laser light emitted from the exposure light source is guided onto the alignment mark of the wafer. (A resist removal optical means is provided, and the resist on the alignment mark is vaporized by irradiation with laser light emitted from an exposure light source.

(Function) In the present invention, when the reticle pattern is not exposed on the wafer, the exposure light source is used as a light source for resist removal, so even if the light source is emitting light continuously, the light from the exposure light source is can be used effectively, and efficient use of energy and high throughput can be achieved.

(Embodiment) FIG. 1 is a block diagram of an optical system according to a first embodiment of the present invention viewed from the side.

As the exposure light source 1, an excimer laser (Excimer laser) is used as a pulse laser light source that includes wavelength components in the ultraviolet region.
r Laser) is used. When the movable reflector 2 is in the position shown in the figure, the emitted light from the light source 1 passes through a resist removal optical path that is reflected by the movable reflector 2, and passes through the movable reflector 2.
When is at the position indicated by the broken line, the exposure light passes through the exposure optical path shown by the broken line.

A shutter 3, an integrator 4, a reflector 5, a condenser 6, a reticle 7, and a projection lens 8 are arranged in the exposure optical path shown by the broken line. The pattern is imprinted. In order to align the reticle 7 and the wafer 25, an alignment device is used that aligns the alignment marks provided on the reticle 7 and the wafer 25, but since it is well known, it is omitted from the drawing. .

The resist removal optical path shown by the solid line is provided with a reflecting mirror 9, a shutter 11, an aperture 12, a condensing lens 14, and a reflecting mirror 15, and the light reflected by the reflecting mirror 15 is focused on the wafer 27 on the moving stage 28. be illuminated.

The wafer 2 for the light spot focused in this way
alignment mark detection means 29 for detecting alignment marks on the wafer 27 in order to perform alignment of the wafer 27;
．． 30 is provided integrally with a reflecting mirror 9, a shutter 11, an aperture 12, a condensing lens 14, and a reflecting mirror 15.

With such a configuration, the moving stage is moved so that the alignment mark on the wafer 27 is detected by the alignment mark detection means 29. Perform matching (global alignment). On the other hand, wafer 2
5 is also aligned with the reticle 7 by an alignment device (not shown). And movable reflector 2
When is at the position indicated by the solid line, the light emitted from the light source 1 is reflected by the movable reflecting mirror 2, further reflected by the reflecting mirror 9, and reaches the shank 11. The shutter 11 is opened for a time necessary to remove the resist when the alignment mark detection means 29, 30 detect the alignment mark and the movable reflecting mirror 2 is at the position indicated by the solid line. Then, the resist on the alignment mark irradiated with the light spot is vaporized. In this way, while the movable reflecting mirror 2 is at the position indicated by the solid line and the resist is being removed, positioning is performed using the alignment mark provided for one predetermined chip on the wafer 25.

When the shutter 11 described above is closed, the movable reflecting mirror 2 rises to the position indicated by the broken line. Therefore, the light from the light source 1 reaches the shank 3. The shutter 3 is opened for a predetermined time when the movable reflecting mirror 2 is switched to the position shown by the broken line and the alignment of the wafer 25 using the alignment mark is completed. The transmitted light from the shutter 3 is homogenized by an integrator 4, reflected by a reflecting mirror 5, passes through a condenser 6, and illuminates a reticle 7. The reticle 7 is conjugated to the surface of the wafer 25 by the projection lens 8, and the pattern of the reticle 7 according to the magnification of the projection lens 8 (for example, 115 magnification) is projected onto a predetermined chip of the wafer 25. In this way, while the movable reflection t11.2 is at the position indicated by the broken line and the wafer 25 is being exposed, the movable stage 25 moves by a predetermined amount based on the design value. Then, the alignment mark of the chip whose resist is to be removed next moves to the position where the light spot is irradiated.

Hereinafter, the movable reflector alternately selects the resist removal optical path and the exposure optical path, and when one optical path is selected, the alignment of the wafer in the other optical path is performed, and the shutter 3.11 is It is opened for a certain period of time in relation to the operation of. Then, the wafer 27 from which the resist on the alignment marks for all the chips has been removed is placed on the stage 26 at a transport position (not shown) in place of the wafer 25 from which exposure has been completed for all the chips.

In the case of resist removal, only global alignment is performed using the wafer 27 and the alignment mark detection means 29 and 30, and thereafter the light formed by being reflected by the reflecting mirror 15 is only moved by the stage 28 based on the design values. The spot is aligned with the alignment mark provided for each chip on the wafer 27, and on the other hand,
In the case of exposure, each chip is aligned with the reticle 7 using alignment marks provided for each chip on the wafer 25. This is because the accuracy of alignment is significantly different between the former and the latter, and the latter requires greater accuracy.

Note that the opening time of the shutter 11 may be set to a time long enough to vaporize the resist, assuming that the resist on the alignment mark has a constant thickness, or
Since this cannot necessarily be applied to all cases, a detector is provided to detect whether or not the resist has been removed based on changes in reflectance or fluorescence generated from the resist. By controlling this, it is possible to prevent the resist from not being completely removed or damaging the fine alignment marks due to uneven thickness of the resist.

Next, an electrical block diagram of the first embodiment is shown in FIG. 2 and will be explained.

The first computer 31 is a computer for controlling exposure, the second computer 32 is a computer for controlling resist removal, the third computer 33 is a computer 31.32,
This is the main computer that controls the insertion and removal of the reflector.

The first computer 31 moves the stage 26 through the drive device 34. On the other hand, an alignment markter force is applied from the alignment device 35. In addition, the first computer 3
1 controls opening and closing of the shutter 3.

The second computer 32 moves the stage 28 through a drive device 36. Further, an alignment signal from the alignment mark detection means 30 is input for initial setting. The second computer 32 further controls opening and closing of the shutter 11.

The third computer 33 receives commands from the command center 37, switches the reflector 2, and also exchanges signals with the first computer 31 and the second computer 32.

That is, first, when the third computer 33 receives an instruction to start operation from the command center 37, it sets the reflector 2 at a predetermined position (in this example, the third computer 33 sets the reflector 2 to a predetermined position to remove the resist first). ). The third computer 33 then instructs the first computer 31 and the second computer 32 to align the wafers 25 and 27 on the stages 26 and 28 that each of them has. Even if the alignment is the same, the former is an alignment for each chip or an alignment based on statistical processing,
The latter is global alignment. The first computer 31 and the second computer 32 each have a drive device i34.
．． 36, the alignment device 35,
The stages 26 and 28 are moved until an alignment completion signal is obtained from the alignment detection means 30. The second computer 32 has received a command from the third computer 33 indicating that it is in the resist removal mode, and when the alignment completion signal is obtained from the alignment detection means 30, the stage 2
8 is stopped, and the shutter 11 is opened for a predetermined time.

When the shutter 11 is closed, the second computer 32
A signal indicating that the resist on the alignment mark of the first chip has been removed is sent to the third computer 33. The third computer 33 uses this signal to set the reflecting mirror 2 to perform exposure, and when the switching of the reflecting mirror 2 is completed, sends an exposure start signal to the first computer 31. The first computer 31 instructs the drive device 34 to bring the stage 2i to the initial position, and further, upon receiving a signal from the alignment device 35 that the alignment using the alignment marks 7 has been completed, sends a signal to stop the stage 26. When the exposure start signal is input, if the signal indicating that alignment has been completed is not input, wait until then, and send the signal indicating that alignment has already been completed. As soon as a signal is input, the shutter 3 is opened for a predetermined period of time. When the shutter 3 is closed, an exposure end signal is sent to the computer 33.

On the other hand, from the third computer 33 to the first computer 31
At the same time as the exposure start signal is sent to the second computer 32, a signal is sent to the second computer 32 to move the stage 28 by a predetermined amount in order to remove the resist on the alignment mark of the next chip.

The second computer 32 sends a signal to the drive device 36 according to a preset amount of movement of the stage. The drive device 36 moves the stage 28 by a predetermined amount. As a result, the wafer 27 is moved so that a light spot is formed on the alignment mark of the next chip.

Therefore, when the third computer 33 switches the reflector 2 in response to the exposure end signal from the first computer 31 and sends the resist removal signal to the second computer 32, the opening and closing of the shutter 11 can be controlled immediately.

Thereafter, exposure and resist removal are repeated until a preset number of chips are exposed and all alignment marks are removed.

Note that all conventional techniques can be used as-is for the configuration related to exposure, except for the sequence related to resist removal.

In Figure 1 shown in Figure 7 as the first embodiment above, the optical system for resist removal is simplified and only its principle is shown, but in reality the alignment marks are aligned in two directions, X and Y, and in rotation. In order to perform correction, two or more are provided for one chip. FIG. 3 shows a perspective view of the main parts of an optical system that simultaneously removes the resist on two or more alignment marks. ζ In FIG. 3, the same reference numerals as in FIG. 1 indicate the same members.

After the reflected light from the movable reflecting mirror 2 is reflected by the reflecting mirror 9,
The beam enters the beam splinter 10. beam splinter 1
The transmitted light of 0 reaches the shutter 11. If the shutter 11 is open, the light passing through the shutter 11 passes through the aperture of the diaphragm 12 and is reflected by the dichroic reflecting mirror 13. This reflected light passes through the condensing lens 14 and the reflecting mirror 15 to the chip CP.
The light is focused on the X-direction alignment mark 16 of I.

The dichroic reflector 13 reflects light with a wavelength of the oscillation line of the laser 1 and transmits light with a longer wavelength. It is observed by the observation device 17 via the mirror 13. The observation device 17 has a built-in light source for illumination, and may illuminate the fine alignment mark 16 through an optical system 13, 14, 15, and detects fluorescence generated from the resist on the fine alignment 16 by illumination of the laser 1. You may. Further, it may be possible to switch between these two as appropriate.

The reflected light from the beam splinter 10 reaches the shutter 18. If the shutter 18 is open, the light passing through the shutter 180 passes through the aperture of the diaphragm 19 and is reflected by the dichroic ink reflecting mirror 13. This reflected light is transmitted through a condensing lens 21 and a reflecting mirror 22.
Y-direction alignment mark 23 of chip CP, through
The light is focused on the top. The dichroic reflector 20 is the same as 13, and the Y-direction alignment mark 23 is observed by the observation device 24 via the reflector 22, the condenser lens 21, and the dichroic reflector 20.

According to the optical system shown in FIG. 3, the removal operation is performed on two alignment marks at the same time, thereby improving throughput. If necessary, the light can be further divided to remove three or more alignment marks at the same time. The position of the light spot and the state of resist removal on the wafer are monitored by an observation device 17.24.

In addition, members 13, 14, 15, 17 are arranged so that alignment marks 16, 23 can be applied no matter where they are placed.
A holding member that integrally holds the , and member 20.21.22
．． 24 in the X direction and Y direction, respectively.
If the wafer is held in a moving device so as to be movable in different directions, it is convenient to be able to handle different types of wafers.

Next, FIG. 4 shows a third embodiment of the present invention. Components with the same symbols as in FIG. 1 have the same functions.

The difference between the embodiment shown in FIG. 4 and the embodiment shown in FIG. 1 is that the embodiment shown in FIG. In this embodiment, resist is removed from alignment marks on a wafer during exposure.

The beam splinter 2' uses a transmitted optical path as an exposure optical path and a reflected optical path as a resist removal optical path. Of course, a movable reflecting mirror such as that used in FIG. 1 may be used instead of the beam splitter 2' (on the contrary, the movable reflecting mirror 2 in FIG. 1 can be replaced with a beam splitter).

Optical members 3.4.5.6 disposed in the exposure optical path
．． 7.8 is exactly the same as the embodiment of FIG. The optical members 9.11.12.14.15 in the resist removal optical path are also exactly the same as in the embodiment shown in FIG. The difference is that the projection lens 8 and the optical members in the resist removal optical path 9.11.12.
14 and 15 are integrally connected, and their positional relationship is such that when fine alignment for exposure is performed, the light spot from the resist removal optical path is on the alignment mark of the chip other than the chip being exposed. It is set. Before fine alignment for exposure, the resist on the fine alignment mark must be removed, so first, only resist removal is performed by global alignment, and then, when possible, exposure and resist removal are performed simultaneously. If this is not possible, it is sufficient to perform only one of them.

Note that it is more effective if the optical member in the resist removal optical path is configured to remove a plurality of fine alignment marks at the same time, as shown in FIG.

Furthermore, multiple sets of optical members for resist removal are arranged around the projection lens 8 so that a light spot is generated for each fine alignment mark of a plurality of chips surrounding the chip aligned with the reticle. You may do so. If the light spots 7) caused by these light spots are appropriately selected and generated by controlling the opening and closing of the shutter, it is possible to avoid problems caused by light spots occurring at unnecessary locations. Specifically, damage to the wafer, decrease in the light intensity of the light spot, etc. can be suppressed.

〔Effect of the invention〕

As described above, according to the present invention, exposure and resist removal can be performed with almost no reduction in throughput.
It is possible to increase the utilization efficiency of light sources and reduce running costs.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the optical system of the first embodiment of the present invention viewed from the side, FIG. 2 is an electrical block diagram of the first embodiment, and FIG.
FIG. 4 is a perspective view showing the main parts of a resist removal optical system according to a second embodiment of the present invention, and FIG. 4 is a block diagram of the optical system according to a third embodiment of the present invention viewed from the side. (Explanation of symbols of main parts) 1...Exposure light source, 2...Movable reflecting mirror, 2'...Beam splitter, 11...Shutter, 16.23...
- Fine alignment mark, 19. 30... Alignment mark detection means, 32... Second computer, 33... Third computer, 36... Drive device.

Claims (1)

[Scope of Claims] A pulsed laser light source that includes wavelength components in the ultraviolet region is used as an exposure light source, and after aligning a reticle and a wafer based on their respective alignment marks, laser light emitted from the pulsed laser light source In the exposure apparatus that exposes the pattern of the reticle onto the wafer, when the pattern of the reticle is not exposed to the wafer, resist removal optical means guides a laser beam emitted from the exposure light source onto an alignment mark of the wafer. is provided, and by irradiation with laser light emitted from the exposure light source,
An exposure device characterized by vaporizing resist on alignment marks.