GB2332534A

GB2332534A - Replaceable mask

Info

Publication number: GB2332534A
Application number: GB9824540A
Authority: GB
Inventors: Seung-Seok Yoo
Original assignee: LG Semicon Co Ltd
Current assignee: SK Hynix Inc
Priority date: 1997-12-19
Filing date: 1998-11-09
Publication date: 1999-06-23
Anticipated expiration: 2018-11-09
Also published as: GB9824540D0; GB2332534B; KR19990051659A

Abstract

A mask comprises a substrate 2 which is optically transparent with an opaque pattern 3 thereon; mask frames 14 placed on the upper and lower edges of the mask; a plurality of holes and screws 15,15a for removably fixing the mask frames round the mask; a pellicle frame 6 attached to top and bottom surfaces of each mask frame; and a pellicle 7 attached to top and bottom surfaces of each pellicle frame and thus covering a centre part of the mask. It is thus possible to replace the mask within the protective frame without scrapping the mask. The mask frames may be fixed by clamps and grooves (Figs 6-8 not shown) rather than screws and the mask may be a single opaque substrate with holes (Fig 5 not shown).

Description

1 2332534 A MASK FOR FABRICATING A SEMICONDUCTOR DEVICE AND METHOD THEREOF

The present invention relates to semiconductor devices, and in particular to a mask for semiconductor device fabrication and a fabrication method thereof.

In semiconductor device fabrication, the process for forming a pattern on a semiconductor substrate using exposure of the substrate to a light source is called photolithography. The photolithography process is described below.

Initially, a photoresist film, which reacts in a particular way when exposed to light, is applied on the semiconductor substrate, and a mask having a partiucular pattern to allow light to pass through certain areas and to prevent light passing through other areas is formed on the semiconductor substrate. The mask is irradiated by an irradiator (i.e. a light source). As a result, the areas of the photoresist film on the semiconductor substrate which are exposed to the light which passes through the mask react. When the semiconductor substrate is subsequently placed into a developing solution, one portion of the photoresist film, which may be the portion which reacted to the light, is removed. In an alternative method, the other portion i.e. that which did not react to the light, may be removed. Such a method thereby forms a pattern on the semiconductor substrate.

A conventional mask used in the above described photolithography process is illustrated in Figures 1 and 2 of the accompanying drawings. In these drawings, Figure 1 is a plan view of a conventional mask apparatus; and Figure 2 is a vertical cross- sectionai view of the conventional mask of Figure 1 taken along the line II-II' of Figure 1.

2 A thin film 1 is provided with an opaque pattern 3 of a predetermined shape on a centre portion of an optically transparent substrate 2 of a predetermined thickness.

A pellicle frame 6 having a predetermined height surrounds the pattern 3 on the thin film 1 since the centre part thereof has a hole. The pellicle frame 6 is attached thereof to each of the upper and surfaces la, lb of the thin film 1 at the edges. A pellicle 7, that is a pattern protection film, is attached to the top and bottom surfaces of the pellicle frame 6. Each pellicle 7 is attached to the pellicle frame 6 by an adhesive, so that the pellicle 7 and the thin film 1 are fixed together and are inseparable from each other. The pellicle 7 protects the patterns 3 formed on the substrate 2.

A method of fabricating the conventional mask will now be described.

Initially, the thin film 1 is fabricated. In other words, a material which does not transmit light, such as a chromium (Cr), is thinly applied onto the substrate 2, which is flat and optically transparent, and is of a predetermined thickness. A chrome film is thus formed. Next, a resist film, which reacts to light, or alternatively to an electron beam, is applied to the chrome f ilm, and the resist film is irradiated to light by means of a light exposing apparatus, or is subjected to an electron beam irradiator, in accordance with a desired pattern. The resist film which was irradiated by the light, or by the electron beam, is developed, thus forming a resist pattern. The chrome film is etched, with the resist pattern forming a protection film, thereby forming the opaque pattern 3. As mentioned above, the opaque pattern 3 of the chrome film is formed on one side la of the thin film 1, and the other side 1b thereof remains as optically-transparent glass material.

In the photolithography process, the opaque pattern 3 of the chrome film does not transmit light, whilst the 3 remaining portion (i.e. without the opaque pattern 3 of the chrome film) transmits the light. However, if the remaining portion of the transparent substrate 2 without the opaque pattern 3 becomes externally damaged, or has a foreign substance deposited thereon, a pattern which is different from the desired pattern is formed on the substrate 2. For this reason, it is necessary to provide a protection film, i.e. the pellicle 7, for protecting both sides la, lb of the thin film 1.

Accordingly, the pellicle frame 6 is attached to the edges of each of the upper and lower surfaces la, lb, of the thin film 1, and each pellicle 7 is attached to the pellicle frame 6 in order to cover the pattern 3.

The thus fabricated mask, constructed of the thin film 1, the pellicle frame 6, and the pellicles 7 can be used repeatedly. However, when a semiconductor product requiring a different pattern needs to be manufactured, the thin film 1 of the conventional mask cannot be used. Accordingly, although the pellicle frame 6 and the pellicle 7 for protecting the thin film 1, may themselves be used again with other patterns, the whole mask has to be disposed of, because the pellicle frame 6 and the pellicle 7 are formed so as to be inseparable from the thin film 1.

Further, the cost of the mask varies depending upon the manufacturing difficulty to the thin film 1. In general, this can prove expensive. Accordingly, scrapping the whole mask is not an economical option, and additionally causes environmental problems due to the increase of waste.

Accordingly, it is an object of the present invention to provide a more efficient mask and a method of fabrication thereof.

According to a first aspect of the invention, there is provided a mask, comprising: a thin film having a predetermined-shaped pattern; a pair of solid mask frames placed on the edge of each of upper and lower surfaces of 4 the thin f ilm, and having an opening in a centre part thereof; a plurality of mask frame holders for securing the mask frames and the thin film together; a respective pellicle frame attached to a portion of top and bottom surfaces of each mask frame; and a pellicle attached to top and bottom surfaces of each pellicle frame.

According to a second aspect of the invention, there is provided a method of fabricating a mask, the method comprising: a first step of fabricating a thin film with a predetermined- shaped pattern; a second step of attaching respective mask frames on an edge portion of upper and lower surfaces of the thin film; a third step of fixing the mask frames and the thin film by a plurality of mask frame holders; a fourth step of attaching a respective pellicle frame on a portion of upper and lower surfaces of the mask frame using an adhesive; and a fifth step of attaching a respective pellicle to top and bottom surfaces of each pellicle frame.

Thus, the mask of the invention is capable of being recycled, whereby only the thin film need be replaced by one having the required pattern, without the need to scrap the entire mask.

The first step may further include the steps of applying an opaque layer on an optical-transparent substrate, forming a resist pattern on the opaque layer, and etching the opaque layer, with the resist pattern as a mask, thus forming opaque layer patterns.

Also, the first step may include forming a resist pattern on an opaque substrate for intercepting light, and selectively etching and aperturing the opaque substrate with the resist pattern as a mask, thereby forming transparent patterns. In addition, the step may further include filling up, with a substance for transmitting light in an open portion of the opaque substrate.

According to a third aspect of the invention, there is provided a mask, comprising a thin film having a pattern arranged thereon; a framework, arranged to be releasably secured around the edge of upper and lower surfaces of the thin film, the framework being apertured over a central region thereof; and wherein the aperturing of the framework is covered so as to provide mechanical protection of the exposed upper and lower surfaces of the film.

According to a fourth aspect of the invention, there is provided a method of fabricating a mask, the method comprising: fabricating a thin film with a predeterminedshaped pattern; locating a framework around the edge of upper and lower surfaces of the thin film, the framework being apertured over a central region thereof; securing the framework and the thin film together in a releasable manner; and covering the aperturing so as to provide mechanical protection of the exposed upper and lower surfaces of the film.

There is further provided a method of exchanging the thin film in a mask comprising: separating mask frame holders from mask frames; separating the mask frames; removing the thin film placed between the mask frames; inserting a new thin film between the mask frames; and securing the mask frames and the new thin film together by means of the mask frame holders.

The invention will now be described by way of example with reference to the drawings in which:

Figure 3 is a plan-view of a recyclable mask according to a first embodiment of the present invention; Figure 4 is a vertical cross-sectional view of the recyclable mask of Figure 3 taken along the line IV-IV'; Figure 5 is a vertical cross-sectional view wherein the thin film of the mask in Figure 3 is modified; Figure 6 is a plan view of a recyclable mask according to a second embodiment of the present invention; 6 Figure 7 is a vertical cross-sectional view of the recyclable mask of Figure 6 taken along the line VII-VIV; Figure 8A shows a mask frame for use with the recyclable mask according to the second embodiment of the present invention; and Figure 8B illustrates a mask frame holder for use with the recyclable mask according to the second embodiment of the present invention.

A recyclable mask according to embodiments of the present invention will be described in detail below. The elements of the embodiments which are the same as those of the conventional art described above with reference to Figures 1 and 2 are labelled with the same reference numbers.

With reference to Figures 3 and 4, a thin film 1 is inserted between a pair of solid or rigid mask frames 14 of a predetermined thickness, and the thin film 1 and the mask frames 14 are secured together by a plurality of mask frame holders 15 to form a single body. To prevent the thin film 1 from being damaged physically or chemically, respective pellicle frames 6 are attached to portions of the top and bottom surfaces of the mask frames 14 by an adhesive, and a pellicle 7 is bonded to the top and bottom surfaces of respective pellicle frames 6. A screw 15 acting as the mask frame holder, is inserted into each of a plurality of holes 15a formed through the mask frames 14 to fix the mask frames 14 and the thin film 1 together.

The thin film may have a structure 1 having an opaque pattern 3 formed on an optically-transparent substrate 2 as shown in Figure 4, or may have a structure 1' provided with a substrate 2' which is optically opaque, having a transparent pattern 31 punched therethrough as shown in Figure S. The transparent pattern 31 may be holes, penetrating through the opaque substrate 2', or may alternatively comprise an optically transparent material 7 such as glass, or silicon dioxide, etc inserted in the opaque substrate 21.

A fabrication method of the mask according to the first embodiment of the present invention will now be described.

Firstly, a fabrication method for the thin film 1 shown in Figure 4 will be described.

An optically opaque material, such as chromium (Cr) is thinly applied on the upper surface of the opticallytransparent substrate 2, which is flat and is of a predetermined thickness, thus forming a chrome film. Next, a resist film is applied onto the chrome film the resist film reacting to the light, or to an electron beam. Next, the resist film is irradiated to the light in accordance with a desired pattern by a light exposing apparatus or an electron beam irradiator. A resist pattern is formed by developing the resist film which was subjected to light or the electron beam. Then the chrome film is etched using the resist pattern as a protection film, thus forming the opaque pattern 3 of the chrome film. Accordingly, on one side la of the thin film 1 formed in this manner, there is provided the opaque pattern 3 formed in a predetermined shape from the chrome film, while on the other side lb thereof the transparent material remains. In the above- described photolithography process, the part of the structure with the opaque pattern 3 thereon does not transmit the light, but a remaining part of the transparent substrate, i.e. without the opaque pattern 3, transmits the light.

Now, a method for fabricating the thin film 1' as shown in Figure 5 will be described.

First, a resist film is applied on an opaque substrate 2' which optically intercepts light, and the resist film is irradiated to light, or by an electron beam, and is then developed, thus forming a resist pattern. With the resist pattern acting as a mask, the opaque substrate 2' is etched, thereby forming transparent pattern 31. The opaque 8 substrate 2' may be apertured by being etched, or alternatively the transparent pattern 31 may be formed by filling up holes where the opaque substrate 2' has been removed with a material which is optically transparent.

The thin film 1, 1' is fabricated as described above, and a plurality of holes (not shown) are then formed along a marginal portion of the thin film 1,1'. Next, a pair of solid or rigid mask frames 14, each of which has an apertured central region so as to surround the pattern 3,31 of the thin film 1,1', the frames having a predetermined thickness to provide physical solidity. In addition, holes 15a are formed in each marginal portion of the mask frames 14, and the thin film 1,1' is inserted between the two mask frames 14. The holes 15a formed through the mask frames 14 correspond with holes (not shown) through the thin film 1, 1'. A screw 15 is inserted into each of the holes 15a formed through the mask frames 14, and fixes the mask frames 14 to the thin film 1,1'. The screws 15 provide the mask frame holder 15.

If the part of the transparent substrate 2 which does not comprise the pattern 3 becomes externally damaged, or has a foreign substance deposited thereon, a pattern which is different from the desired pattern might be formed on the semiconductor substrate 2. Thus, it is necessary to protect the thin film 1.

To protect the thin film 1,1', a respective pellicle frame 6 is attached to the top and bottom surfaces of the mask frames 14, by an adhesive, and a pellicle 7 is attached to each of the top and bottom surfaces of the pellicle frames 6.

Referring to Figures 6 and 7 the recyclable mask according to the second embodiment of the present invention has the same construction as the mask of the first embodiment, with the exception of the mask frame and a mask frame holder. Also, according to the second embodiment the 9 thin film 1 has no holes, this being different from the above described first embodiment.

The mask frame and the mask frame holder according to the second embodiment of the present invention will now be described in detail.

Figure 8A illustrates a mask frame 24 according to the second embodiment of the present invention. Here, the mask frame 24 has a groove 24a hollowed on an outer edge portion thereof so that the groove 24a is formed lower than an inner portion facing the opaque pattern 3. One mask frame 24 is attached to each of the upper and lower surfaces of the thin film 1, and the mask frames 24 and the thin film 1 are fixed together by inserting a c-shaped clamp 25 (hereinafter, called the mask frame holder), as shown in Figure 8B, in the grooves 24a of edge portions of each mask frame 24.

The method of fabricating the mask for recycling according to the second embodiment of the present invention is the same as for the mask according to the first embodiment, except that clamps rather than screws are used as the mask frame holder for fixing the mask frames and the thin film together.

The mask described above, may simply be recycled by performing the steps of: separating the mask frame holders from the mask frames; removing the thin film placed between the mask frames; inserting a new thin film between the mask frames; and fixing the mask frames and the thin film together with the mask frame holders.

As described above, the recyclable mask according to the present invention, which disconnects the mask frames by loosening the mask frame holders, reduces manufacturing costs of semiconductor devices by re-using parts of the mask unless they become physically damaged, and of preventing environmental problems be reducing waste.

Claims

Claims:

1. A mask, comprising:

thin film having a predetermined-shaped pattern; pair of solid mask frames placed on the edge of each of upper and lower surfaces of the thin film, and having an opening in a centre part thereof; a plurality of mask frame holders for securing the mask frames and the thin film together; a respective pellicle frame attached to a portion of top and bottom surfaces of each mask frame; and a pellicle attached to top and bottom surfaces of each pellicle frame.

2. A mask according to claim 1, wherein each of the marginal frames has a plurality of holes in a marginal portion thereof.

3. A mask according to any preceding claims, wherein the mask frame holder comprises a screw.

4. A mask according to claim 1, wherein each of the mask frames has a groove in an edge portion thereof.

5. A mask according to claim 1 or claim 4, wherein the mask frame holder is a c---shaped clamp.

6. A mask according to any preceding claim, wherein the thin film comprises an opaque pattern on a substrate which is optically transparent.

7. A mask according to any of claims 1 to 5, wherein the thin film comprises a transparent pattern formed by aperturing an opaque substrate.

11

8. A method of fabricating a mask the method comprising: a first step of fabricating a thin film with a predetermined-shaped pattern; a second step of attaching respective mask frames on an edge portion of upper and lower surfaces of the thin film; a third step of fixing the mask frames and the thin film by a plurality of mask frame holders; a fourth step of attaching a respective pellicle frame on a portion of upper and lower surfaces of the mask frame using an adhesive; and a fifth step of attaching a respective pellicle to top and bottom surfaces of each pellicle frame.

9. A method according to claim 8, wherein the first step comprises: applying an opaque layer on a substrate which is optically transparent; forming a resist pattern on the opaque layer; selectively etching and aperturing the opaque layer with the resist pattern as a mask; and removing the resist pattern.

10. A method according to claim 8, wherein the first step comprises: forming a resist pattern on an opaque substrate for intercepting light; and selectively etching and aperturing the opaque substrate with the resist pattern as a mask.

11. A method according to claim 10, wherein the first step comprises filling an apertured portion of the opaque substrate with a substance which is optically transparent.

12. A mask, comprising: a thin film having a pattern arranged thereon; 12 a framework, arranged to be releasably secured around the edge of upper and lower surfaces of the thin film, the framework being apertured over a central region thereof; and wherein the aperturing of the framework is covered so as to provide mechanical protection of the exposed upper and lower surfaces of the film.

13. A mask according to claim 12, wherein the framework comprises two mask frame members, a respective mask frame member being secured to the upper and lower surfaces of the thin film.

14. A mask according to claim 12 or 13, wherein the framework is releasably secured using a plurality of mask frame holders.

15. A mask according to claim 14, wherein each mask frame holder comprises a screw.

16. A mask according to claim 14, wherein each mask frame holder comprises a =-shaped clamp.

17. A mask according to any one of claims 12 to 16, wherein the aperturing is covered by a respective pellicle that is secured to the edges of the thin film by means of the framework.

18. A method of fabricating a mask, the method comprising: fabricating a thin film with a predetermined- shaped pattern; locating a framework around the edge of upper and lower surfaces of the thin film, the framework being apertured over a central region thereof; securing the framework and the thin film together in a releasable manner; and 13 covering the aperturing so as to provide mechanical protection of the exposed upper and lower surfaces of the film.

19. A method of changing the thin film in a mask in accordance with any one of claims 1 to 6 and 12 to 17 comprising:

separating the mask frame holders from the mask frames; separating the mask frames; removing the thin film placed between the mask frames; inserting a new thin film between the mask frames; and securing the mask frames and the new thin film together by means of the mask frame holders.

20. A mask constructed and arranged substantially as herein described and shown with respect to Figures 3 to 8B of the drawings.

21. A method of fabricating a mask, substantially as hereinbefore described with respect to Figures 3 to 8B of the drawings.