WO2005003863A2

WO2005003863A2 - Device and method for processing a mask pattern used for the production of semiconductors

Info

Publication number: WO2005003863A2
Application number: PCT/EP2004/006763
Authority: WO
Inventors: Thomas J. Moran
Original assignee: Dynamic Microsystems Semiconductor Equipment Gmbh
Priority date: 2003-07-07
Filing date: 2004-06-23
Publication date: 2005-01-13
Also published as: WO2005003863A3; DE10330907A1

Abstract

Disclosed are a device and a method for processing a mask pattern (10) used for the production of semiconductors. Said mask pattern (10) comprises a photomask (11) and a frame (20) that is spanned by a protective film (22) which is stuck to the photomask (11). The frame (20) is removed from the photomask (11). A support (50) for the mask pattern (10) and a heating device (54) that acts upon the mask pattern (10) are provided. A first, motor-operated device (64) grips the frame (20) while a second, motor-operated device (76) lifts the frame (20) from the photomask (11).

Description

Device and method for processing a mask template for semiconductor manufacturing

The invention relates to a device for processing a mask template for semiconductor production, which has a photomask and a frame glued onto the photomask, which is covered with a protective film, the glued frame being removed from the photomask.

The invention further relates to a method for processing a mask template for semiconductor production, which has a photomask and a frame glued onto the photomask, which is covered with a protective film, the glued frame being removed from the photomask. Photomasks (so-called "reticles") are used in semiconductor production. The photo mask consists of a glass plate, one side (the so-called "chrome side") of which bears the image of the semiconductor structure to be produced by exposure.

During this exposure process, it is extremely important that no foreign particles settle on the chrome side, which would lead to a defect on the exposed surface, for example of a wafer. The process therefore runs under the strictest clean room conditions.

In order to further reduce the risk of particles depositing on the chrome side, it is also known to cover the chrome side with a protective film (the so-called "pellicle") arranged at a distance from the chrome side. For this purpose, a frame is usually used, the dimensions of which are slightly smaller than the dimensions of the photomask and which is covered by the protective film. This frame is placed on the chrome side. If particles now settle on the protective film or on the surface of the photo mask opposite the chrome side, these particles are at a distance corresponding to the thickness of the frame or the photo mask from the chrome side. If the distance is, for example, 1/4 "(about 6 mm), the image of the semiconductor structure located on the chrome side can be imaged with an extremely shallow depth of field during exposure, so that the particles located at a distance of about 6 mm fall into a range of one Get blurred, which no longer leads to annoying effects on the exposed surface of the wafer. In current practice, the frame with the protective film is glued to the chrome side immediately after the production of the photo mask, so that the image of the semiconductor structure is immediately protected against dirt. The frame with the protective film remains on the photomask for as long as it is needed.

When handling the photo mask, it can happen that the protective film is accidentally damaged. The protective film is namely an extremely thin structure, for example only 1/8 μm thick, which means it is extremely mechanically sensitive. If the protective film is damaged or bursts, the chrome side is no longer protected against particles. Scraps of the film can also fall onto the chrome side of the photomask, in particular onto the image of the semiconductor structure located there. The scraps stick or stick to the surface of the photomask and can only be removed, if at all, using complicated and elaborate chemical processes. In such a case, the frame must of course also be removed from the chrome side of the photo mask. Since the frame is glued on, this usually leads to adhesive residues remaining on the chrome side, which also have to be removed separately.

Manual methods are used today to remove the frame with the remains of the protective film from the photomask. For this purpose, the frames are provided with blind holes on the outer frame surfaces. You can use tweezers or other pointed objects to reach into these blind holes and thereby detach the frame from the photomask. Due to the very different consistency of the glue used and the quality of the glue joint, this often succeeds not or only imperfectly, so that on the one hand the adhesive residues already mentioned remain on the photomask and on the other hand even more parts of the protective film can get onto the chrome side of the photomask if handled carelessly. All in all, this is a very uncontrolled manual work process with a high potential for interference.

The invention is therefore based on the object of developing a device and a method of the type mentioned at the outset in such a way that the problems mentioned above are avoided. In particular, it should be achieved that in the event of damage to the protective film, the frame with the damaged protective film can be removed from the photomask on the one hand carefully, but on the other hand with high reproducibility, without adhesive residues remaining on the photomask and without the risk that parts or All or part of the protective film can be wholly or partly on the chrome side of the photo mask.

In a device of the type mentioned, this object is achieved according to the invention in that a support for the mask template, a heating device acting on the photomask, a first motor-operated device for gripping the frame and a second motor-operated device for lifting the frame from the photomask are provided.

In a method of the type mentioned in the introduction, the object is achieved according to the invention in that the photomask is first heated and then the frame is lifted off the photomask by a motor. The object underlying the invention is completely achieved in this way.

By heating the photomask, the adhesive located between the photomask and the frame is softened, with the result that the frame can be lifted off the photomask in a reproducible manner with little force. Appropriate control and design of the devices for gripping and lifting the frame can be used in this way to process the mask template, in which the risk of adhesive residues remaining on the photomask is minimized and the risk of damage to the protective film can be practically eliminated.

In a preferred embodiment of the invention, heating to a temperature in the range between 80 and 100 ° C. is effected.

This temperature range has proven to be optimal for the adhesives commonly used.

According to a further embodiment of the invention, the photomask is heated from its surface opposite the frame.

This measure has the advantage that the adhesive becomes warmer and thus softer in the transition between the photomask and the adhesive than in the transition between the adhesive and the frame. It is easy to see that in this way the entire adhesive can be removed from the photomask even more completely. In a further preferred development of the invention, the first device and the second device are connected to one another via a joint, in particular via a cardan joint, for example a ball joint.

This measure has the advantage that when the frame is lifted off, the part of the frame can be the first to detach from the photomask in which the holding force has become the lowest due to the softened adhesive connection present. In this way, the frame is peeled off from the photomask, so that there is no risk that, in the event of a jerky lifting, the adhesive will remain on the photomask in less softened areas of the adhesive connection.

In this case, it is further preferred if a third motor-operated device is provided for mechanically bridging the joint.

This measure has the advantage that, apart from the moment the frame is lifted off the photomask, there is always a rigid connection between the frame and the lifting device, so that uncontrolled movements are avoided.

It is further preferred according to the invention if the first device has means for positively gripping the frame.

This measure has the advantage that the frame is held securely when it is gripped and cannot accidentally come loose again, as could be the case with a frictional grip. It is particularly preferred in this exemplary embodiment if the means are designed as mandrels that can be inserted laterally into an opening in the frame.

This measure has the advantage that on the one hand a reliable positive connection can be established, and on the other hand existing devices, namely the openings mentioned, can be used in the frame. It is therefore not necessary to use specially designed frames to apply the present invention. Rather, you can also work with commercially available frames.

In a further preferred embodiment of the invention, a fourth device is provided which generates a negative pressure on a surface of the protective film facing away from the photomask.

This measure has the advantage that the protective film is sucked away from the photomask during the entire lifting process, so that there is no risk that the protective film itself or parts thereof could come into contact with the chrome side and stick there.

Finally, means for centering the mask template on the support are preferably provided.

This measure has the advantage that spatially defined conditions can be set at the beginning of the machining process. Further advantages of the invention result from the description and the attached drawing.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in the combination indicated in each case, but also in other combinations or on their own without departing from the scope of the present invention.

An embodiment of the invention is shown in the drawing and is explained in more detail in the following description. Show it:

1 is a perspective view of a commercially available mask template;

FIG. 2 shows a section through the edge region of the mask template shown in FIG. 1, on a greatly enlarged scale;

Fig. 3 is a side view, partially broken away, of an embodiment of a device according to the invention.

1 and 2, 10 designates a mask template as it is used for semiconductor production. The mask template 10 has a photo mask 11 in the form of a glass plate 12. The glass plate 12 has a first surface 14, which lies at the top in the figure and forms the so-called “chrome side” of the photomask 11. An image 16 for the semiconductor structure to be produced is located on this first surface 14. The opposite, second surface 18 lies in the figures below.

On the first surface 14 there is a frame 20 which is covered on its upper side with a protective film 22. The protective film 22 thus forms a third, uppermost surface 23.

The frame 20 is attached to the photomask 11 by means of an adhesive 24. The frame 20 is dimensioned such that it surrounds the image 16 on all sides.

As shown in FIG. 2, particles 26a can settle on the third surface 23 and particles 26b on the second surface 18 of the mask template 10. The first surface 14 with the image 16, however, is protected by the protective film 22.

In the right half of FIG. 2, 28, 30 and 32 denote a first level, a second level and a third level. The first level 28 lies at the level of the chrome side, that is to say the first surface 14, the second level 30 at the level of the third surface 23 and the third level 32 at the level of the second surface 18. The distance between the first level 28 and the second Level 30 is indicated by d ₂ and the distance between the first level 28 and the third level 32 is indicated by d _: . These distances d ₂ , d _x are approximately the same size and in practice are 1/4 "(about 6 mm).

If the mask template 10 is used for an exposure process, the exposure optics are adjusted so that the first plane 28, in which the image 16 is located, is extremely small depth of field is imaged on the surface of a wafer to be exposed. The depth of field is in any case much smaller than the distances d _x and d ₂ . The consequence of this is that the particles 26a, 26b are imaged extremely blurred on the surface of the wafer and therefore do not interfere within wide limits.

If the protective film 22 is damaged, the frame 20 with the damaged protective film can be removed from the photomask 11. For this purpose it is known to provide openings 34, for example blind holes, which are positioned in a defined manner on the side faces of the frame 20. A laboratory worker with a pointed object, for example tweezers, pliers or the like, can then reach into these openings 34 and manually detach the frame 20 from the photomask 11. The adhesive connection represented by the adhesive 24 must be destroyed.

The device shown in FIG. 3 is used to make this manual process, which is subject to numerous possible malfunctions, more reproducible.

The device designated overall by reference numeral 40 contains a base plate 42, an intermediate plate 44 and a cover plate 46. The plates 42, 44, 46 are connected to one another via vertical columns 48. If the plates 42, 44, 46 e.g. are rectangular, the columns 48 can be attached in the four corners of the plates 42, 44, 46.

The intermediate plate 44 carries a support 50 for the mask template 10. The support 50 can, for example, consist of four small cuboids exist, which are each provided with a recess for a corner of the photomask 11.

Below the surface of the intermediate plate 44 surrounded by the support 50, the intermediate plate 44 is provided with a recess 52. A heating device 54 is located below the cutout 52. The heating device emits heat radiation 56 upwards, that is to say through the cutout 52. The second surface 18 of the photomask 11 is thus exposed to the heat radiation 56 when a mask template 10 is on the support 50 and the heating device 54 is switched on.

From an underside 60 of the cover plate 46, guide profiles 62 extend downward. The guide profiles 62 serve to guide a vertical slide, designated overall by the reference numeral 64, which is used for gripping and lifting the frame 20. The vertical slide 64 has a support plate 66 which is provided with guide bores 68 for the guide profiles 62. If the support plate 66 has a rectangular shape in plan view, e.g. two guide profiles 62 can be provided in the region of two diagonally opposite corners of the support plate 66.

3 indicates that the support plate 66 moves up and down in the vertical direction when the vertical slide 64 moves on the guide profiles 62.

In order to carry out this movement, a first piston-cylinder unit 76 is attached to the cover plate 46. A downwardly projecting piston rod 78 of the first piston-cylinder inputs Unit 76 is provided with a ball 80 at its front, free end. The ball 80 is held in a bearing 82 which is arranged on the support plate 66. A double arrow 84 indicates that, as a result of this articulated connection, a pivoting movement of the support plate 66 around the center of the ball 80 is possible. The guide bores 68 for the guide profiles 62 are therefore appropriately dimensioned to enable this pivoting movement of the support plate 66.

On the support plate 66 there are two piston-cylinder units 86a, 86b with piston rods 88a, 88b, which wear shoes 90a, 90b at their free ends. When the shoes 90a, 90b are extended, they come into frictional engagement with the surface of the guide profiles 62. This causes the ball joint 80/82 to be bridged and the support plate 66 to be immobilized on the guide profiles 62.

A frame 94 is attached to an underside 92 of the support plate 66. The frame 94 carries a lower suction plate 96. A vacuum device 100, indicated schematically in FIG. 3 by an arrow, is connected via a line 98. In this way, negative pressure can be generated on an underside 102 of the suction plate 96.

Finally, two third piston-cylinder units 104a, 104b are attached to the frame 94. These have piston rods 106a, 106b, the free end of which is in turn provided with arms 108a, 108b pointing downwards. Inwardly pointing mandrels 110a, 110b in turn protrude from the arms 108a, 108b. With 110 'it is finally indicated by dashed lines that the Mandrels 110a, 110b can have a different position and length in order to be able to accommodate different frames.

The device 40 operates as follows:

In the rest position, the first piston-cylinder unit 76 is at its upper end point, i.e. the piston rod 78 is retracted as far as possible. The vertical slide 64 is therefore at the top as far as possible.

A mask template 10 can now be placed on the support 50 by hand or servomechanically.

As soon as this has happened, the heating device 54 is activated, whereupon the heat radiation 56 emerges upwards and heats the second surface 18 from below.

At the same time, the first piston-cylinder unit 76 is activated and the piston rod 78 extends downward. The vertical slide 64 now moves downward on the guide profiles 62 until the bottom of the suction plate 96 rests on the third surface 23 of the mask template 10, that is to say on the protective film 22. The vacuum device 100 is switched on, so that the protective film 22 is sucked against the underside 102.

Now the second piston-cylinder units 86a, 86b are activated, so that the piston rods 88a, 88b extend and the shoes 90a, 90b frictionally engage the guide profiles 62. The vertical slide 64 is thus in the position in FIG. 3 shown position, namely a defined takeover position, rigidly clamped.

In this defined take-over position, the third piston-cylinder units 104a, 104b are now activated, with the result that the piston rods 106a, 106b in their outer end position are retracted until the mandrels 110a, 110b into the associated openings 34 on the side Engage surfaces of the frame 20.

As soon as this has been done, the second piston-cylinder units 86a, 86b are activated such that the shoes 90a, 90b detach from the guide profiles 62 again. A limited pivoting movement of the support plate 66 around the center of the ball 80 is thus possible.

The entire vertical slide 64 is now moved upward by actuating the first piston-cylinder unit 76. The frame 20 is separated from the photomask 11 remaining in the support 50, which can be achieved with appropriate holding means, provided the weight of the photomask 11 is not sufficiently large.

During the lifting process, the frame 20 first detaches from the photomask 11 at the point at which the adhesive 24 was softened most as a result of the heat radiation 56. The frame 20 can therefore be inclined when it is lifted, for example by tipping over a side line or standing up over a corner. This movement is made possible by the gimbal mounting of the support plate 66. During the lifting process, the vacuum device 100 expediently remains switched on in order to ensure that the protective film 22 continues to adhere to the underside 102 of the suction plate 96 and in any case to prevent the protective film 22 from sagging and coming into contact with the chrome side of the photomask 11 ,

When the vertical slide 64 has reached its upper end position, the support plate 66 can in turn be locked on the guide profiles 62 by actuating the second piston-cylinder units 86a, 86b, so that the frame 20 can now be removed under defined conditions, be it manually or by means of a handling device.

The photomask 10 is now removed from the support 50 and the device 40 is ready for a new processing operation.

Claims

claims

1. Device for processing a mask template (10) for semiconductor production, which has a photomask (11) and a frame (20) glued onto the photomask (11), which is covered with a protective film (22), the glued frame ( 20) is removed from the photomask (11), with a support (50) for the mask template (10), with a heating device (54) acting on the photomask (11), with a first, motor-operated device (64) for gripping of the frame (20) and with a second, motor-operated device (76) for lifting the frame (20) from the photomask (11).

2. Device according to claim 1, characterized in that the heating device (54) acts on a surface (18) opposite the frame (20) of the photomask (11).

3. Device according to claim 1 or 2, characterized in that the first device (64) and the second device (76) are interconnected via a joint.

4. The device according to claim 3, characterized in that the joint is a cardan joint, in particular a ball joint (80, 82).

5. The device according to claim 3 or 4, characterized in that a third, motor-operated device (86 - 90) is provided for mechanically bridging the joint.

6. The device according to one or more of claims 1 to 5, characterized in that the first device (64) has means (34, 110) for positively gripping the frame (20).

7. The device according to claim 6, characterized in that the means are designed as mandrels (110) which can be moved laterally into an opening (34) in the frame (20).

8. The device according to one or more of claims 1 to 7, characterized in that a fourth device (100) for generating a negative pressure on a surface of the protective film (22) facing away from the photomask (11) is provided.

9. The device according to one or more of claims 1 to 8, characterized in that means for centering the mask template (10) on the support (50) are provided.

10. A method for processing a mask template (10) for semiconductor production, which has a photomask (11) and a frame (20) glued onto the photomask (11), which is covered with a protective film (22), the glued frame ( 20) is removed from the photo mask (11), in which the photo mask (11) is first heated and then the frame (20) is lifted off the photo mask (11) by a motor.

11. The method according to claim 10, characterized in that the mask template is heated to a temperature in the range between 80 and 100 ° C.

12. The method according to claim 10 or 11, characterized in that the photomask (11) is heated on a surface (18) opposite the frame (20).

13. The method according to one or more of claims 10 to 13, characterized in that the frame (20) is lifted off the photo mask (11) via an articulated connection (80, 82).

14. The method according to claim 13, characterized in that the articulated connection (80, 82) is mechanically bridged before lifting the frame (20).

15. The method according to one or more of claims 10 to 14, characterized in that the frame (20) is positively gripped when lifting.

16. The method according to one or more of claims 10 to 15, characterized in that a negative pressure is generated on a surface (23) of the protective film (22) facing away from the photomask (11).

17. The method according to one or more of claims 10 to 16, characterized in that the mask template (10) is first centered on a support (50).