JPS6097356A - Photomask - Google Patents

Abstract

PURPOSE:To prevent transfer of foreign matter and to improve the yield of a semiconductor product and working efficiency by controlling the air pressure in the hermetic space formed between the surface of a photomask, frames and shielding films thereby changing the space. CONSTITUTION:Bellows-like frames 13, 14 are attached to the peripheral part on the front and rear of a photomask 10 formed with a light non-transmittable film 12 on the surface of a transparent base plate 11 and respective thin transparent shielding films 15, 16 are extended at the other end edges thereof. Air is supplied into the hermetic spaces formed among th photomask 10, the frames 13, 14 and the films 15, 16 inbetween to make the space thereof variable. The space is made large in the stage of exposing to put foreign matter to the outside of the depth of focus even if such foreign matter sticks on the shielding films, thereby preventing transfer and generation of a defect and improving the yield of the semiconductor. The space is decreased to attain tight contact in the stage of inspecting the appearance of the mask 10. The automatic inspection is thus made possible without generation of the deviated focus of the optical system of an inspecting machine by the shielding films and the working efficiency is improved.

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. This technology relates to a technology that allows exposure to light.

[Background technology]

In the photolithography process that is frequently used in the manufacture of semiconductor devices, photomasks and reticles (herein collectively referred to as photomasks) are essential as original plates for element patterns formed on wafers and the like. by the way,
When pattern transfer is performed on this type of photomask using photolithography 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.

Therefore, as shown in FIG. 1, fixing frames 2.3 as spacers are fixed around the front and back surfaces of the photomask 1 at 5, and transparent M4 and M5 are stretched around the periphery of each of these fixing frames 2.30. It is possible to do so. According to this configuration, even if foreign matter adheres to the films 4 and 5, the surface 9 of the photomask 1
Since direct adhesion to the M-plane is prevented, this film 4,
If the gaps between the photomask 5 and the front and back surfaces of the photomask 1, in other words, the heights of the fixed frames 2 and 3, are set to be larger than the depth of focus of the aligner, no foreign matter will be transferred.

However, with this configuration, once the film 4.5 is formed, there is a problem that 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. occurs. For this reason,
The present inventors have discovered that an indirect inspection method such as performing a visual inspection on the transferred object is required, which results in a problem of 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 include:
It will become clear 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.

In other words, by attaching a frame of varying height to the photomask and covering the photomask by attaching a transparent shielding film to this frame, the photomask and the shielding film can be separated during exposure and visual inspection of the photomask. This prevents the transfer of foreign matter while enabling automatic visual inspection, thereby increasing 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 1o has a 11aKC on the surface of a transparent glass substrate 110.
The metal layers such as r and other light-opaque films 12 are formed into a desired pattern shape.

The pattern shape is formed using a conventional IJ lithography technique, but the details will be omitted.

The front and back surfaces 11a and 11bK of the photomask 100 have square frames 13 and 14 attached to their peripheries.

In this example, these frames 13 and 14 are entirely formed in a bellows shape from a soft resin material, and one end thereof is bonded to the surface of the photomask 10 so that the other end t
The position can be changed in the thickness direction of 0. In other words, when the photomask 10 is installed horizontally, each frame 13, 14 allows its height dimension to vary. and.

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, to airtightly cover the front and back surfaces 11a and llb of the photomask 10, respectively. An auxiliary frame 17.18 is attached to the connection portion of the shielding film 15.16 with the frame 13.14, and provides moderation to the frames i3, 14 and the shielding film 15.16.

Further, one end of a small diameter tube 19.20 is connected to a part of the periphery of the frame 13.14, and the front and back surfaces 11a and llb of the photomask 10, the frame 13.14 and the shielding film 15.16 are connected to each other. Airtight space defined 21.22
It communicates with These tubes 19, 20 are equipped with on-off valves 23, 24, and the other end is connected to an air controller 25 capable of supplying clean air or sucking air.

According to the above configuration, if the clean air of the air controller 25 is supplied to the airtight space 21.22 through the tube 19.2 (1-), the pressure inside the space 21.22 becomes more positive than the outside air, and the shielding membrane 15, 16 is frame 13, 14'& photomask 100 table while stretching.

Away from the back surfaces 11a and llb, as shown in FIG.
16, the gap size is increased to about t5 to 15 times. In this state, open/close valves 23, 24'& if closed, shielding film 15
．． 16 is kept in that state.

Therefore, if this photomask is placed in an aligner and a predetermined exposure is performed, even if the foreign matter adheres to the shielding films 15 and 16, it will remain on the front and back surfaces 11a of the photomask 1o.

11b, and the shielding film 15.
Since 16 is a photomask and is separated from the back surfaces 11a and 11b by more than the depth of focus of the aligner, this foreign matter 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 1o, opening/closing/(/l
/7'23. 24 open and air controller 25
The air in the airtight space 21.22 is removed by the pipe 19.20.
suction through. As a result, the inside of the airtight space 21, 22 is depressurized compared to the outside air, and as shown in FIG. Back side 11a, l
It is said that it is in close contact with lb. Therefore, if the photomask 10 is put into 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 become out of focus, and the automatic visual inspection machine will be able to pass the photomask 10 in exactly the same way as a normal photomask. can be done.

From the above, this photomask structure prevents defect transfer and improves the yield of semiconductor products.
On the other hand, it is possible to improve the automatic appearance efficiency and improve the work efficiency and the accuracy.

〔effect〕

(1) A frame with a variable width is attached to the photomask, a transparent shielding film is attached to this frame, and the gap between the shielding film and the front and back sides of the photomask can be changed by the action of the frame. Therefore, at the time of exposure, the gap is thoroughly cleaned and the foreign matter on the shielding film is placed outside the depth of focus to prevent the foreign matter from being transferred, thereby preventing the occurrence of defects and improving the semiconductor yield.

(21) On the other hand, by reducing the gap between the shielding film and the photomask to zero, it is possible to prevent defocusing in the optical system of the visual inspection machine, which makes it possible to perform inspections using automatic visual inspection machines and reduce the work involved in inspection. It is possible to improve efficiency and, on the other hand, increase evaluation accuracy.

(The size of the gap between the photomask and the shielding film can be changed by making the 31 frame bellows-shaped and defining an airtight space between the front and back surfaces of the photomask using a shielding film, and then controlling the air pressure in this airtight space. Because it allows you to simply supply air.

It is possible to create conditions suitable for exposure and appearance inspection by only performing suction (5).

The invention made by the present inventor has been specifically described above based on examples.1 However, it is understood that the present invention is not limited to the above-mentioned examples, and 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 be physical means other than air pressure (eg, heat). Furthermore, if 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 has been mainly applied to photomasks for manufacturing semiconductor devices, which is one field of application, but is not limited to this, and can be applied to reticles as well as reticles. It can be used for all original plates used in Shinkai photographic technology.

[Brief explanation of the drawing]

FIG. 1 is a 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 1E3[1J (A) and (B) are cross sections of a bottom mask for explaining the operation. It is a diagram. 10...bottom mask, lla, llb...front, back, 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. Agent Patent Attorney Akio Takahashi

Claims (1)

[Claims] 1. A frame whose height is variable is attached to the photomask, and a transparent shielding film covering the pattern is attached to the frame, so that the surface of the photomask and the shielding film are connected to each other. A photomask characterized by being configured so that the gap can be changed. 2. The photomask according to claim 1, wherein an airtight space is defined between the photomask surface, the frame, and the shielding film, and the air pressure in this airtight space is controlled to vary the gap. 3. The photomask according to claim 2, wherein the frame is formed into a bellows shape, and a tube connected to an air controller is opened and communicated with the frame.