JPS58210618A - Method and apparatus for reduced projection exposure - Google Patents

Abstract

PURPOSE:To permit a reticle defect inspection to be effected with a reticle set at a reticle exposure position thereby to obtain a high reliability while suppressing a rise in a cost, by a method wherein in photographing, a picture surface to which the reticle pattern is to be transferred is located at the reticle exposure setting position so as to oppose to the pattern surface of the reticle, and a reduced projection exposure is effected according to the reticle after the photographing. CONSTITUTION:With a reticle 3 and a wafer 6 aligned with each other, a wafer 9 to which the reticle pattern is to be transferred is set under the pattern surface of the reticle 3 by means of a setting device 4. In this case, a picture surface 8 to which the reticle pattern is to be transferred, which is constituted by a resist material 10, is set under the pattern surface of the reticle 3 so that a proximity exposure will be realized. When an exposure light source 1 is actuated, a pattern 13 and all of defects 14, such as dusts and the like, on the reticle 3 are photographed so as to sensitize the resist material 10 of the wafer 9. Since the pattern surface of the reticle 3 and the resist material 10 are disposed in very close proximity to each other, a proximity exposure is effected. Accordingly, the image of the pattern and defects on the reticle 3 is clearly transferred to the picture surface 8, which is constituted by the resist material 10, without substantial magnification.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reduction projection exposure method 2 and a reduction projection exposure apparatus used directly to carry out this method, and particularly relates to a reduction projection exposure method 2 that performs step exposure (in some cases, so-called This is intended to prevent productivity declines caused by "defects in the pellets."

Generally, in the manufacturing process of semiconductor devices, when a pattern on a reticle is exposed on a wafer by reduction projection exposure and sequential step exposure is performed, two particles of dust other than the pattern on the reticle,
If other defects such as foreign matter or scratches are present, the defects will be repeatedly exposed to all chips of the Ueno film, resulting in "all pellet defects." Although the occurrence frequency of this whole pellet failure is small, once it occurs, it has an extremely serious impact, such as a significant drop in production.

For this reason, reticle defects have traditionally been carefully inspected before reduction projection exposure, and recently reduction projection exposure apparatuses equipped with automatic defect inspection mechanisms have been developed.

As an example of this type of device, a reticle to be exposed is transported to a defect inspection section within the device, and the front and back surfaces of the reticle are irradiated with inspection light and the scattered light from the defect is measured with a photo sensor to perform defect inspection. There is a reticle that is determined to be non-defective as a result of inspection and is transported to a predetermined exposure position.

However, in such technology, firstly, the defect inspection position and the exposure position for the reticle are different, so defects may occur after the inspection, such as foreign matter layering on the reticle in the inspection section during transportation to the exposure position. There is a risk of this occurring, as well as the inability to correlate the position of the device pattern and the inspected defect.Secondly, due to incomplete detection due to light scattering, it is not possible to detect foreign objects buried between the defects, etc. The disadvantages are that the nature of the device is unknown, and thirdly, the cost of the device is high.

The purpose of the present invention is to avoid such disadvantages, to enable reticle defect inspection to be performed with the reticle set at the exposure position, and to obtain high reliability while suppressing the increase in cost. The object of the present invention is to provide a reduction projection exposure method and a reduction projection exposure apparatus capable of realizing this method.

In order to achieve this object, the present invention involves, in a reduction projection exposure method, photographing a patterned surface of a reticle immediately before exposure, and performing defect inspection using the reticle image of the patterned surface of the reticle after photographing. The reticle after photographing is subjected to reduction projection exposure.Furthermore, in order to realize the photographing of the reticle image, the reduction projection exposure apparatus according to the present invention allows the image to be transferred to be exposed to the reticle during photographing. It is configured to be located directly opposite the pattern surface of the reticle at the exposure set position.

Embodiments of the present invention will be described in further detail below with reference to the drawings.

FIG. 1 is a perspective view showing the principle of an embodiment of a reduction projection exposure apparatus according to the present invention, and FIG. 2 is an enlarged front sectional view of the main parts.

In FIG. 1, this reduction projection exposure apparatus includes an exposure light source 1 consisting of a mercury lamp or the like, a condenser lens 2, a reticle 3 on which a pattern is formed, and a patterned surface of the reticle 3, which is an image to be transferred. It is equipped with a setting device 4 as a setting means for setting, a reduction lens 5, and an XY table 7 which holds a wafer 6 to be subjected to reduction projection exposure and can move it in steps.

In this embodiment, the transfer target screen 8 is composed of a resist material 10 of a wafer (hereinafter referred to as a transfer target wafer) 9 having the same structure as the wafer 6 to be exposed.

The setting device 4 includes a cassette 11 that stores a plurality of wafers 9 to be transferred, and automatically takes out each 9 ft wafer to be transferred from the cassette 11 and sets the wafers so as to directly face the pattern surface of the reticle 3. Set mechanism 12
I'm ready. Although detailed illustrations are omitted, the setting mechanism 12 includes, for example, a take-out transport unit that takes out the wafer 9 to be transferred and transports the wafer 9 to just below the balloon surface of the reticle 3, and a take-out transport unit that takes out the wafer 9 to be transferred and transports the wafer 9 to a position corresponding to the pattern of the reticle 3. ? °C positioning with alignment and flatness of
In addition, there is a holding unit that holds the wafer 9 as close as possible to the extent that foreign matter such as dust that may stick to the reticle is not transferred to the pattern surface of the reticle, and the wafer from which the reticle image was photographed in this held state after photographing is completed. 9 is provided with a conveying section for conveying the image to the developing process.

Next, a description will be given of a case where the reduction projection exposure apparatus having the above structure is used as an embodiment of the reduction projection exposure method according to the present invention.

The device 4 aligns the reticle 3 and the wafer 6, and sets the wafer 9t to be transferred onto the pattern surface of the reticle 3.
Set by At this time, the transfer target screen 8 made of the resist material 10 is set so as to realize proximity exposure on the pattern surface of the reticle.

When the exposure light source 1 emits light, as shown in FIG.
All of these images are photographed while exposing 10 ft of resist material on the wafer 9 to be transferred. At this time, since the pattern surface of the reticle 3 and the resist material 10 are very close to each other, proximity exposure is performed, and the pattern of the reticle 3 and the image of the defect (hereinafter referred to as a reticle image) are formed of the resist material 10. The image is clearly transferred to the transfer target screen 8 at almost the same magnification.

After photographing the reticle image, the setting device 4 removes the image from the position of the reticle 3 on the wafer 9 to be transferred and automatically transports it to a developing process, where the developing process is performed. Through the development process, the photographed reticle image is clearly transferred to the transfer target wafer 9 as it is.

By performing a defect inspection on this transferred image, a defect inspection on the reticle, which is the original image of this transferred image, is substantially performed tx.

The transferred image may be inspected visually using a comparison microscope or the like, or by irradiating the transferred image with inspection light using an automatic reticle visual inspection device or the like and collecting the reflected light. This may be done automatically. In addition, the inspection method may be to visually or electrically process the difference between the regular reference pattern and the transferred image to determine the difference, or to identify a characteristic image area (defect area) of the transferred image. Alternatively, a defective portion may be detected by comparing it with pattern design data.

On the other hand, in the reduction projection exposure apparatus in which the transfer target wafer 9 has been reset, reduction projection exposure for the reticle 3 is immediately started. That is, the reduction projection exposure work and the development process 2 for the transfer target wafer 9 described above.
and defect inspection work will be carried out simultaneously.

Therefore, there is no waiting time for test results.

As a result of reticle defect inspection using transfer target wafer 9,
If it is determined that the reticle has no defects, the wafer 6 on which the reticle has been subjected to another reduction projection exposure process is directly sent to the next process. However, if the reticle VC is determined to be "defective", the wafer 6 that has been subjected to reduction projection exposure processing for the reticle is prevented from being sent to the next process, and further reduction using the reticle is prohibited. The projection exposure process is stopped, and
The reticle itself is replaced as appropriate.

Therefore, wafers with all pellets defective are prevented from being sent to the next process.

In this way, according to this embodiment, the reticle image is transferred to the reticle after alignment with the wafer, and the transferred image is inspected for defects. There is no risk of such problems, and it becomes easier to correlate the positions of device patterns and inspected defects.

Further, according to this embodiment, since one reticle image is exposed to proximity exposure on the transfer target screen, the reticle image can be clearly transferred as it is to the transfer target screen.

For example, in the case of a reticle used for reduction projection exposure with a reduction ratio of 10:1, when exposed with a gloximitty gap of 20 μm, dust, foreign matter, etc. up to 3 μm can be clearly transferred to the transferred screen. This is 0.3μ in terms of wafer soil.
This becomes a pattern of m. Visual inspection of 0.03 μm or more is an area that cannot be performed at all by general visual inspection of Ueno-developed patterns, and it is extremely effective because it does not cause fatal defects in micro devices of 1 to 2 μm. That is, compared to visually inspecting a developed pin by a wafer technician, this embodiment can inspect a reticle image that is 10 times larger, and the defect inspection accuracy is much higher.

In addition, when using a reticle with other reduction ratios, such as 5:1, when exposed under the same conditions, the foreign matter will be 0.6 μm in terms of wafer soil, but the effect when targeting fine devices with a width of 1 to 2 μm remains unchanged.

In addition, since the wafer is used as a transfer target, it can be used as a light source for photographing the reticle image as well as a light source for exposure. Processing steps are available to carry out the procedure.

Furthermore, since the reticle defect inspection is performed using the transferred image and the reduction projection exposure work on the wafer is performed simultaneously while the reticle is being inspected, inspection time and inspection result waiting time can be eliminated. It is possible to prevent the projection exposure work time from becoming longer and to improve productivity.

Furthermore, if the defect inspection is determined to be defective, the wafers and work that have already been exposed up to the time of the determination will be wasted, but experience has confirmed that the frequency of all pellet defects is extremely small. Therefore, this waste has little negative impact on productivity. However, if all pellets are defective and these defective wafers are sent to the next process, it will have a very serious negative impact on productivity, so it is necessary to prevent wafers with all pellets from being sent to the next process. In this example, it is possible to
There is no doubt that it has an extremely large effect.

According to the reduction projection exposure apparatus according to this embodiment, since the transfer target wafer is used as the transfer target screen, the setting device as a setting means for setting the transfer target screen so as to directly face the reticle can be easily configured. It can be used with existing cassettes, take-out devices, alignment loading devices, vacuum chuck devices, conveyance devices, etc., and
It can also be easily incorporated into an existing reduction projection exposure apparatus.

In the above embodiment, an exposure light source is used as a light source for printing a reticle image onto a resist material of a wafer to be transferred, but the present invention is not limited to this, and a dedicated light source may be used. When using a dedicated light source, for example, a light reticle may be irradiated as shown in FIGS. 3, W, and 4.

In Figure 2, the transfer light is directed to the reticle 3 as shown by the arrow.
The light is irradiated onto the side edge of the reticle 3, enters the inside of the reticle 3, and undergoes repeated total reflection. This total reflection smell "C1 reticle 30
If there is a defect 14 such as a scratch or a foreign object on the front or back surface, diffuse reflection occurs there. This scattered light approaches the front and back surfaces of the reticle 3 and exposes each of the first set wafers 9 to the resist material 1 (l) to transfer defects.

According to this embodiment, only the defect 14 is present on the transfer target wafer 9.
This has the effect that defect inspection can be extremely simplified.

In FIG. 5, as shown by the arrow, the transfer light is entirely irradiated only on the surface of the reticle 3 on which the pattern 13 is formed, and if there is a defect 14 such as dust attached to the surface, There it is diffusely reflected. This scattered light exposes the resist material 10 of the transfer target wafer 9 set close to the surface of the reticle 3, resulting in defective transfer.

In this embodiment as well, it is possible to transfer only defects. Note that the presence of defects such as dust adhering to the back surface of the reticle 3 or defects such as dust adhering to the soil of the pattern 13 does not cause a serious hindrance in reduction projection exposure, and therefore does not need to be detected as a defect.

It goes without saying that the transfer methods shown in FIGS. 2, 3, and 4 and other methods may be used in combination.

In the above embodiment, the case where the transferred screen is constructed using a wafer to be exposed is explained, but the transferred screen is not limited to this, and for example, a highly sensitive glass substrate such as a semiconductor silicon wafer substrate or a glass substrate such as quartz is used. You can use photoresists that have been coated and baked, commercially available photographic plates, and even
It may also be configured using a solid-state imaging device in which a large number of independent light-receiving elements (pixels) are arranged on a semiconductor substrate and the amount of light that reaches each pixel is electrically read out, or a normal imaging device (such as a television camera). .

Further, in the above embodiment, the case where the pattern surface of the reticle, which is the image to be transferred, is brought close to the pattern surface of the reticle and faced directly by 10 degrees has been explained, but the invention is not limited to this. The reticle may be set so as to be optically directly opposed to the patterned surface of the reticle (the reticle and the image to be transferred are perpendicular to the optical axis) using a reflective mirror, prism, or the like.

Further, in the embodiment described above, the case where a chip pattern is exposed on a wafer in a stepwise manner is described, but the invention is not limited to this.
For example, it can be applied to the case of manufacturing a master mask.

As explained above, according to the present invention, defect inspection of the reticle can be performed while it is set at the exposure position.
Moreover, a reduction projection exposure method and apparatus can be obtained which can obtain high reliability while suppressing an increase in cost.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing one embodiment of the present invention, Fig. 2 is an enlarged longitudinal sectional view of the main part, Fig. 3 is an enlarged longitudinal sectional view of the main part showing the second embodiment, and Fig. 4 is an enlarged longitudinal sectional view of the main part. FIG. 3 is an enlarged vertical cross-sectional view of main parts shown in the third embodiment. 1... Exposure light source, 2... Condenser lens, 3...
・Reticle, 4... Setting device, 5... Reducing lens, 6... Wafer, 7... XY table, 8... Transfer target screen, 9... Transfer target wafer, 10...・Resist material, 11...Cassette, 12...Set mechanism, 1
3...Pattern, 14...Defect. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. In a reduction projection exposure method in which a pattern formed on a reticle is subjected to reduction projection exposure on an object to be exposed, after the pattern is transferred to a defective image to be transferred which may exist on the reticle immediately before exposure, Defect inspection is performed using a screen, and the reduction projection exposure is performed on this reticle.
A reduction projection exposure method characterized by f. 2. The reduction according to claim 1, characterized in that defect inspection and reduction projection exposure are carried out simultaneously, and when a defect is determined, the exposed object is treated as a defective product. Projection exposure method. 3. A reduction projection exposure apparatus characterized by being equipped with a setting means for setting a defective image to be transferred, which may exist on a reticle, so as to optically face the pattern surface of the reticle. 4. The reduction projection exposure apparatus according to claim 3, wherein the transfer target screen is made of a resist material. 5. Claim wE3, characterized in that the transfer screen is made of a resist material sensitive to reduction projection, and the photosensitive surface is set as close as possible to the pattern surface of the reticle. Reduction projection exposure apparatus as described in . 6. The reduction projection exposure apparatus according to claim 3, wherein the image to be transferred is formed of an imaging screen of an imaging device. 7. The reduction projection exposure apparatus according to claim 6, wherein the imaging device is a solid-state imaging device.