JPH0544662B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to exposure technology, and in particular to a photomask applied to a semiconductor photomask, a reticle for a reduction aligner, etc. The present invention relates to a photomask that is applied to a semiconductor photomask, a reticle for a reduction aligner, etc. It relates to technology that can be used for exposure.

[Background technology]

In the photolithography process, which is often used in the manufacture of semiconductor devices, a photomask or reticle (herein referred to collectively as a photomask) is essential as a master plate for element patterns formed on a wafer or the like. By the way, when pattern transfer is performed on this type of photomask using photoxography technology, if foreign matter such as dust adheres to the front or back surface of the photomask, this foreign matter will be transferred at the same time as the pattern, resulting in pattern defects.

For this purpose, fixed frames 2 and 3 as spacers are fixed around the front and back surfaces of the photomask 1 as shown in FIG. It is conceivable to set up According to this configuration, foreign matter is removed from the membranes 4 and 5.
Since it is prevented from directly adhering to the front and back surfaces of the photomask 1 even if it adheres to If the depth of focus is set to be greater than or equal to the depth of focus of the aligner, foreign matter will not be transferred.

However, with this configuration, once the films 4 and 5 are formed, when the photomask 1 is placed in an automatic visual inspection machine, the films 4 and 5 cause a focus shift in the inspection optical system, making automatic visual inspection impossible. A problem arises. For this reason, the inventors have found that indirect inspection methods such as visual inspection of the transferred object have to be used, resulting in problems such as longer inspection time and lower evaluation accuracy.

[Purpose of the invention]

The purpose of the present invention is not only to prevent foreign matter from adhering to the front and back surfaces of a photomask and to prevent foreign matter from being transferred, but also to perform a good inspection without causing any defects even when the photomask is subjected to an automatic visual inspection machine. An object of the present invention is to provide a photomask that can improve the yield of semiconductor products and improve work efficiency.

The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

[Summary of the invention]

A brief overview of typical inventions disclosed in this application is as follows.

That is, by attaching a frame whose height is variable to the photomask and attaching a transparent shielding film to the frame to cover the photomask, the difference between the photomask and the shielding film can be maintained during exposure and visual inspection of the photomask. The present invention is designed to prevent the transfer of foreign matter while enabling automatic visual inspection, thereby improving the yield of semiconductor products and improving work efficiency.

〔Example〕

FIG. 2 is a partially cutaway perspective view of an embodiment of the present invention, in which a photomask 10 forms a metal film such as Cr or other light-opaque film 12 in a desired pattern shape on the surface 11a of a transparent glass substrate 11. are doing.
A conventional photoxography technique is applied to form this pattern shape, but the details will be omitted.

Front and back surfaces 11a and 11b of the photomask 10
Square frames 13 and 14 are attached to the periphery of the frame. In this example, these frames 13 and 14 are formed entirely in a bellows shape from a soft resin material, and by bonding one end of the frame to the surface of the photomask 10, the other end of the frame changes its position in the thickness direction of the photomask 10. can. In other words, photomask 1
0 is installed horizontally, each frame 13, 14
allows its height dimension to be changed. Shielding films 15 and 16 made of a thin transparent resin material are stretched over the other edges of the frames 13 and 14, respectively, and the front and back surfaces 11a of the photomask 10 are covered with shielding films 15 and 16, respectively.
11b is airtightly covered. Shielding film 1
Auxiliary frames 17 and 18 are attached to the connecting portions of frames 13 and 14, and moderation of frames 13 and 14 and shielding films 15 and 16 is considered.

Furthermore, one ends of small-diameter tubes 19 and 20 are connected to part of the periphery of the frames 13 and 14, and the front and back surfaces 11a and 11b of the photomask 10, the frames 13 and 14, and the shielding films 15 and 16 are connected to each other. It communicates with defined airtight spaces 21 and 22.
These tubes 19, 20 have on-off valves 23,
24 is interposed therebetween, and the other end is connected to an air controller 25 capable of supplying clean air or sucking air.

According to the above configuration, when clean air from the air controller 25 is supplied to the airtight spaces 21 and 22 through the tubes 19 and 20, the pressure inside the spaces 21 and 22 becomes more positive than the outside air, and the shielding membranes 15 and 16 , 14 away from the front and back surfaces 11a and 11b of the photomask 10, and as shown in FIG. Make it bigger. If the on-off valves 23 and 24 are closed in this state, the shielding films 15 and 16 are maintained in that state. Therefore, if this photomask is placed in an aligner and a predetermined exposure is performed, the foreign matter will be removed from the shielding film 1.
5 and 16, it does not directly adhere to the front and back surfaces 11a and 11b of the photomask 10, and the shielding films 15 and 16 do not directly adhere to the front and back surfaces 11a and 11b of the photomask 10.
Since the distance from 1a and 11b is greater than the depth of focus of the aligner, this foreign material is never transferred. Thereby, pattern defects caused by transfer of foreign matter can be reliably prevented.

On the other hand, when inspecting the appearance of the photomask 10, the on-off valves 23 and 24 are opened, and the air in the airtight spaces 21 and 22 is sucked through the tubes 19 and 20 by the air controller 25. As a result, the pressure inside the airtight spaces 21 and 22 is made more negative than the outside air, and as shown in FIG. , are in close contact with the back surfaces 11a and 11b. Therefore, if the photomask 10 is subjected to an automatic visual inspection machine in this state, the shielding films 15 and 16 will not cause the optical system of the inspection machine to be out of focus, and the automatic visual inspection will be performed in exactly the same way as for a normal photomask. can be done.

From the above, this photomask structure prevents defect transfer and improves the yield of semiconductor products, while also enabling automatic visual inspection to improve work efficiency and improve evaluation accuracy. can.

〔effect〕

(1) A frame that can be adjusted in height is attached to the photomask, and a transparent shielding film is stretched over the frame, and the shielding film and the photomask surface are separated by the action of the frame.
Since the structure is configured so that the distance from the back surface can be changed, the distance from the shielding film is increased during exposure, and the foreign matter on the shielding film is placed outside the depth of focus to prevent the foreign matter from being transferred and the generation of defects. Improved yield can be achieved.

(2) Conversely, by making the distance between the shielding film and the photomask small or zero, it is possible to prevent defocusing in the optical system of the visual inspection machine, thereby making it possible to perform inspections using automatic visual inspection machines. It is possible to improve the efficiency of related work and, on the other hand, to improve the accuracy of evaluation.

(3) By making the frame bellows-shaped and defining an airtight space between the front and back surfaces of the photomask using a shielding film, and controlling the air pressure in this airtight space, the distance between the photomask and the shielding film is reduced. Since the temperature can be changed, conditions suitable for exposure and visual inspection can be created simply by supplying and suctioning air.

Although the invention made by the present inventor has been specifically explained based on the examples above, the present invention is not limited to the above examples, and it is understood that various changes can be made without departing from the gist of the invention. Needless to say. For example, the frame may have other configurations as long as it is expandable, and the means for expanding and contracting the frame may utilize physical means other than air pressure (eg, heat). Further, when the glass substrate of the photomask is sufficiently thick, the shielding film may be formed only on the surface side of the photomask where the pattern is formed.

[Application field]

In the above explanation, the invention made by the present inventor was mainly applied to a photomask for manufacturing semiconductor devices, which is the background field of application, but the invention is not limited to this. Of course, it can be used for all original plates used in so-called photographic techniques.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view of a possible photomask structure,
FIG. 2 is a cutaway perspective view of a photomask according to an embodiment of the present invention, and FIGS. 3A and 3B are sectional views of the photomask for explaining the operation. 10...Photomask, 11a, 11b...Table,
Back side, 12... Pattern, 13, 14... Frame, 15, 16... Shielding film, 17, 18... Auxiliary frame, 19, 20... Tube, 21, 22
...airtight space, 23, 24...opening/closing valve, 25
...Air controller.

Claims (1)

[Scope of Claims] 1. One end edge of a frame whose height from the one surface can be varied within and outside the depth of focus is attached to the periphery of one surface of the transparent glass substrate on which the light-opaque film is partially formed. a transparent shielding film covering one surface of the transparent glass substrate is provided on the other edge of the frame, and one surface of the transparent glass substrate is surrounded by the frame and the transparent shielding film. forming an airtight space, supplying clean air into the airtight space,
The transparent shielding film can be separated from one surface of the transparent glass substrate to set the transparent shielding film at a position exceeding the depth of focus, and the air in the airtight space can be sucked to cover the one surface of the transparent glass substrate. A photomask characterized in that an air controller is communicated in the airtight space, and the air controller can bring the transparent shielding film close to set the transparent shielding film within a depth of focus range. 2. The photomask according to claim 1, wherein the frame is formed in a bellows shape, and the airtight space and the air controller are communicated through a tube.