DE19947174A1 - Mask holder with clamps on disc-shaped frame for exposure of semiconductor wafers in ion lithography - Google Patents

Abstract

The mask (3) is weld by clamps (2) on a disc-shaped frame (1). The clamps are held on the frame via levers (5,6,2) enabling their relative motion w.r.t. the frame. In the latter plane, the levers are formed from it by incisions (8), while the lever joints (9-13) are formed by narrow interruptions of the incisions. Preferably at least three positioning levers (5) are provided, each coupled by the first joint (9) to a clamp and to the frame by a second joint (10), with the positioning levers enabling the clamp motion in radial direction.

Description

The invention relates to a holding device for a mask, with a disk-shaped frame for holding the mask using several clamps.

Masks for use in semiconductor technology, for example for ion lithography, must be kept extremely precise in devices for the exposure of semiconductor wafers.

Here is a mask, which is generally circular, often foil-like, with the help of the clamps held in the frame, endeavoring to prevent any deformation of the mask avoid such deformations to a corresponding faulty optical imaging to lead.

Possible deformations can, for example, in the plane of the mask in radial and tan potential direction, deformations are caused by bending in the direction of Axis, d. H. perpendicular to the mask possible, also due to deformations of temperature below distinguished the holding device and the mask, deformations due to carding elements the restraint at the edge of the mask and finally also deformations due to the different position of the holding device including the mask in the gravitational field of the earth are caused.

Although the invention is based on a mask used in the ion lithography of the manufac development of semiconductor wafers is used under "mask" in the context of this description any thin structure can be understood, in which the aforementioned balancing of forces is necessary is so as not to disturb a certain geometry of the "mask". Accordingly, it can also are masks for other imaging processes, regardless of whether they are with particles, such as Electrons, ions or work with radiation such as light or X-rays. Likewise must it is not a transmission structure, but it could also be under "mask" reflective structure can be understood in which the requirements mentioned occur.

In a far away area, namely the construction of mirror telescopes is a weight Relief has become known that is applied to telescopic mirrors to such mirrors to relieve gravity. Please refer to N. N. Michelson, "Optical Telesko pe, theory and construction "(Russ. Moscow) Verlag Nauka 1976. In one shown there Mirror, which is a 20/80 mm diameter telescopic mirror of the McDonald Observato riums on Mount Locke / U. S. A. shows that counterweights work via lever mechanisms on the mirror that in any possible mirror position that occurs due to gravity Forces are compensated. There are axial and radial relief systems with corresponding  provided counterweights and levers, which cause that with increasing Tilt angle of the mirror decreases the force effect of the axial relief systems, whereas the effect of the radial relief systems increases until finally when the Mirror, according to a horizontal position of the mirror axis, only the radial Ent load systems are effective, with the weight from the axial systems finally the relief lever is taken up by the bearings.

Relief systems of the type described are used for large mirrors with masses over 1,000 kg used, with accuracies of the equilibrium state in the order of 0.1 up to 1 kg can be reached. Rigid telescopic mirrors are required, on which the Relief systems can be securely attached. Allow the dimensions of the mirrors the penetration of holes, or can be attached by gluing or milling attachment points be created. In any case, the relief systems described cannot be used for Modify or use mask holding devices.

The invention has for its object to provide a holding device which Taking into account the dimensions of masks, which for example have diameters between rule 150 and 300 mm, and the only small possible thickness of the disc-shaped frame, which is in the order of 6 to 10 mm, a Storage of the clamps to create a balance of various undesirable forces Forces, as already mentioned above, enables the small size of the occurring Forces must be taken into account.

This object can be achieved with a holding device of the type mentioned at the beginning which according to the invention the clamps with respect to the frame are mounted on levers, which allow a relative movement of the clamps with respect to the frame, the levers in the plane of the frame are formed by cut-outs delimiting them and lever joints are formed by narrow interruptions in the cutouts.

The invention provides a relief system which meets the special requirements of a Mask holder meets, and which allows the mask to deform due to various forces, for example by gravity or by temperature sub different forces, are compensated or do not occur at all. Another Advantage of the invention is that the radial extension of the holding device on the essentials remains limited and that no bearing friction and thus particle abrasion occur can.

An expedient variant of the invention is characterized in that at least three Positioning levers are provided, each via a first joint with a clamp and over  a second joint is connected to the frame, the positioning lever being a move allow the clamps to move in the radial direction.

In this way it can be achieved that the clamps occurring in the radial direction force Give in accordingly so that undesirable forces do not occur from the outset can. With this in mind, it is particularly advisable when connecting the joints is essentially tangential.

This is also advantageous if the levers have a relative movement of the clamps with respect to the Enable frame in its level, because above all the forces occurring in this level are taken into account.

In the sense of a compensation of gravitational forces in the mask is recommended an embodiment in which two-armed weight levers are provided, in which a first arm forms a counterweight, and the second arm is operatively connected to one Clamp stands, and a joint is formed between the arms, which twists the Weight lever in the frame level allows. This results in a simple execution shape when the second arm of the weight lever has a joint with associated clamps connected is.

On the other hand, in many cases it will be useful to choose an apprenticeship where the second arm is articulated to the clamp via at least one intermediate lever because of this This ensures that only forces are introduced in the mask plane.

Positioning levers can be used on their own, or both positioning lever and weight lever can be provided. In many cases, however, it becomes useful be when a clamp is assigned both a positioning lever and a weight lever is because space-saving arrangements can be achieved in this way.

To actually hold the mask or its edge, it is recommended that each clamp me consists of a fixed frame and a spring element, the mask with its edge can be clamped between the frame-shaped support and the spring element.

By means of spring elements, a precisely defined, and relatively small one at that can be achieved Determine force, which on the one hand is so large that it meets the respective required conditions, e.g. B. vibrations, is sufficient, and on the other hand is not so large that undesirable Forces at the edge of the mask come, such as. B. clutter forces.  

To facilitate the clamping of the mask, it is useful if the spring element with With the help of a spreading device, it can be temporarily lifted off the frame-fixed support.

In the sense of a simple embodiment, the expansion means can be an axial Boh of the frame can be used mounting pin. On the other hand, there is also an execution possible, in which the expanding means a radially movable mounting pin with a conical End surface is, which cooperates with an inclined surface of the spring element. To this Way, especially if the mounting pin is movable by means of a screw, a very Carry out fine movements.

In another practical embodiment, it is provided that the spring element is a resilient wire bracket is between two stable positions, namely an open and one Clamp position is movable.

To solve the problem, one can also use a holding device for a mask a disc-shaped frame for holding the mask, in which the frame in one Device can be used and frame-side holding / positioning means are provided, which with device-side holding / positioning means interact, in which according to the Invention is provided that the frame-side holding / positioning means on the frame Levers are articulated, which relate to a radial relative movement of the holding / positioning means Lich of the frame allow, the levers in the plane of the frame from this they are formed cut-outs and lever joints of narrow widths cutouts are formed.

In this way, a radial mobility of the frame-side holding / Reach positioning means with respect to the frame that are adequate for the forces that occur the size, in particular the radial extent of the holding device is not expanded unduly and which because of the lack of friction occurring between Parts also avoids any particle abrasion, which with regard to the extreme clean room Requirements would be extremely undesirable.

In practice, an embodiment in which the Lever seen in the circumferential direction, arranged on both sides of a holding / positioning means are.

For good radial guidance of the frame-side holding / positioning means with respect to the Framework is also recommended an embodiment in which several levers in parallel are arranged one another.  

Also in the sense of a simplified production, it is expedient if the holding / Positioning means a holding section of the frame articulated to the frame via the levers have, so that this holding portion with respect to the frame in the radial direction can move. A holding flange can be attached to such a holding section interacts with a holding / positioning device of the device and from a corresponding one Material that may be other than that of the frame is made.

In order to obtain a simple and precise adjustment in the device, it is advantageous if the Retaining flange has a frustoconical recess, which has a device-fixed projection assigned. This advantage can - also in terms of precise positioning - be a ball.

To enable the required adjustment of the mask, it is recommended that the Position of the frame-side holding / positioning means with respect to the frame using jus animal funds can be preset. For example, underlay pieces, Set screws or the like can be used.

The invention together with further advantages is as follows with reference to the drawings explained in more detail. Show in the drawings

Fig. 1 is a schematic front view of a holder according to the invention,

Fig. 2 in a section and in a schematic front view of an edge portion of a mask and it attacking terminal and a weight lever FIG. 3 is a representation as in FIG. 2, but lever with a combined weight and positioning,

Fig. 4 is a schematic, but only partial front view of a further exporting approximate shape of the device of the invention with weight and Positionierhebeln,

Fig. 5 pry in a view similar to Fig. 4 twin arrays of weight and positioning,

Figure in a partial front view nierhebeln. 6 shows a device according to the invention in a further variant with a space-saving arrangement of weight and positio,

Fig. 7 shows a schematic plan view of a part of a holding device according to the invention in the region of a clamp,

Fig. 8 in a radial section through part of a device according to the invention in the clamping region,

Fig. 9 is a view like Fig. 8, however, with a special flexure

Fig. 10 is a section similar to FIG. 8 and 9, but, in another variant

Fig. 11 is a plan view of a section of the inventive device in the region of a clamp,

Fig. 12 shows a section along line 12-12 of Fig. 11,

Fig. 13 is a schematic front view of a 90 ° section of a device according to the invention in a further variant with a special storage of the holding / positioning means, and

FIG. 14 shows a section along line 14-14 of FIG. 13.

In Fig. 1, a holding device according to the invention is shown, which consists of a scheibenförmi gene frame 1 , which has clamps 2 on its inner frame, with the help of which a mask 3 , shown here as a ring, is to be held.

The frame 1 also has frame-side holding / positioning means 4 , which are only indicated in FIG. 1, and whose function and structure is to be explained below.

In the embodiment shown, the mask 3 is held at a total of nine terminals 2. Three of these terminals are connected to positioning levers 5 and six of the terminals 2 are connected to weight levers 7 via intermediate levers 6 . The construction of these lever arrangements will now be discussed in more detail below.

All levers 5 , 6 and 7 are formed in the plane of the frame 1 from these by cutouts 8 , lever joints 9 , 10 , 11 , 12 and 13 being produced by narrow interruptions in the cutouts.

The cutouts 8 are produced, for example, by wire erosion of the plate-shaped, relatively thin frame 1 . Whether or not the ends of the corresponding cuts at the joints end in enlarged openings, as is usually shown here, is a question of the manufacturing technology and the dimensioning of the joints with regard to the rigidity in the various degrees of freedom. On the whole, it can be stated that the joints have de facto joint axes which are perpendicular to the frame 1 or to the plane of the cutouts 8 in the joint, so that, for example, the positioning lever 5 around the joint 10 in the direction of the arrow in the plane of the frame is pivotable, which, thanks to the articulation of the lever 5 in the joint 9 to the clamp 2 , this clamp is movable in the radial direction.

Already the use of the positioning levers 5 articulated on the clamps 2 via joints 9 enables an excellent balance of forces within the mask 3 in accordance with the task set out above.

Often, a compensation of the forces occurring in the gravitational field of the earth at different positions of the mask is desired and here the weight levers 7 offer the corresponding relief. These weight levers 7 have two arms, the two arms ( 7 a, 7 b) being rotatable about the joint 13 in the plane of the frame. The first arm 7 a forms a counterweight which acts via the second lever arm 7 b and via the joint 12 on the intermediate lever 6 , which is articulated on a clamp 2 via the joint 11 . With a radially symmetrical arrangement of the weight levers, the desired weight relief will result in every vertical position of the mask. In practice, the most important case is that in which the mask is inserted from an initially horizontal position into a vertical position in a device.

As can be seen, both the weight lever 7 and the positioning lever 5 are arranged tangentially in wesentli Chen. If this is also not a prerequisite, it is in any case expedient if the lines of action of the levers mentioned are essentially tangential ver, which on the one hand is not insignificant for the balancing of forces and on the other hand thereby the width of the frame 1 (always seen in the radial direction ) doesn't get too big.

In Fig. 1 it is shown that the weight lever 7 are connected via an intermediate lever 6 to the associated clamp 2 , but can also be omitted in embodiments not shown, the intermediate lever 6 , in which case the second arm 7 b of the weight lever 7 with the associated gene clamp 2 is connected via a joint, similar to the joints 9 in the positioning levers. The version with an intermediate lever 6 is shown in Fig. 2 on an enlarged scale Darge, in which one can clearly see the narrow interruptions of the cutouts 8 , which form the joints 11 , 12 and 13 .

Fig. 3 shows a combined lever system, wherein at a terminal 2, both a positi onierhebel 5 - attack as well as a weight lever 7 by means of an intermediate lever 6, the lever 6 engages the terminal 2 via a joint 11 - by a joint 9. The system as shown in Fig. 3 is ultimately nothing more than a combination of the two types of levers shown in Fig. 1, and it is clear that such a combination can lead to a more compact construction of the holding device.

The embodiment according to FIG. 4 shows weight levers 7 arranged in pairs, mirror-symmetrical to each other, each acting on a clamp 2 via intermediate lever 6 . The positioning levers 2 already shown and described are located between such pairs of weight levers.

Another embodiment, likewise with weight levers arranged in pairs, is shown in FIG. 5, but here two weight levers engage together on a clamp 2 . It should be noted at this point that three positioning levers 5 will be used for positive positioning. In the embodiment shown, the positioning levers 5 are integrated in pairs of levers (left and right in FIG. 5). The number of weight levers 7 , on the other hand, can be significantly larger, so that embodiments with, for example, twelve weight levers 7 and three positioning levers 5 can also be practical.

In the embodiment of Fig. 6, engages in the position shown in the upper part of terminal 2, a Ge weight lever 7 via an intermediate lever 6 on, while at the position shown in the lower part of FIG. 6 terminal 2 in both a weight lever 7 via an intermediate lever 6 and attack a positioning lever 5 . In this embodiment there are a total of six clamps 2 , but three positioning levers 5 and six weight levers 7 .

The embodiment shown in Fig. 7 shows that the joints 11 are placed at the end of the weight lever 7 in the middle of the area of the terminals 2 . This training leads to a complete avoidance of undesired torques at the terminals 2 . The clamp shown in FIG. 7 has a spring element 14 , the mask 3 being held between this spring element 14 and a frame-fixed support 15 , which will be shown in more detail later. In Fig. 7 nor a tapered bore 16 is also seen in which a not shown here cone-shaped pin can be inserted in order to fix the terminal 2 of the frame 1 in the transport, assembly and adjustment state respect. Since the solid state joints formed here must be designed to be very soft to avoid disturbing forces, the articulated parts would move very uncontrolled if the frame 1 was not installed without such a securing device, which could lead to damage.

In the sectional drawing of FIG. 8 is, in turn, recognizes a spring element 14, here a leaf spring which is secured by two screws 17 to the frame 1, wherein between the free end of this spring element 14 and a frame-fixed support 15, which is an insertable pin here , the mask 3 is clamped. To insert or remove the mask 3 , the spring element 14 can be temporarily lifted off the mask with the aid of a mounting pin 18 which penetrates an axial bore 19 , so that the mask is released.

Also in the embodiment of Fig. 9, such a mounting pin 18 is provided as spreading means for the spring element 14, but the embodiment of the preceding shown here differs in that a flex joint is formed by thinning of the material of the frame 20. Here in the frame 1. This bending joint 20 transmits radial forces more or less unhindered, but allows bending movements.

The embodiment of FIG. 10 shows another expander member for a spring element 14. Here, a radially movable mounting pin 21 is provided with a conical end surface 22 , which end surface 22 can interact with an inclined surface 23 of the spring element 14 . If the pin 21 is moved , for example by a screwing movement, in the direction of the inclined surface 23 , the end piece of the spring element 14 lifts off the mask 3 and releases it.

Another configuration of the spring element is shown in FIGS. 11 and 12. Here, the spring element consists of a resilient wire bracket 24 which is clamped with two bent ends 25 , 26 with the aid of a holding block 27 and two screws 28 on the frame 1 . This wire bracket has two stable positions, namely a position in which, as can best be seen from FIG. 12, it presses the mask 3 against a frame-fixed support 15 , and a second position in which the radially inner end of the wire bracket of the mask 3 is lifted off. The movement of the wire bracket 24 between these two layers can be carried out with the aid of suitable tools which, for example, can also engage on an extended end 25 or 26 of the wire bracket 24 - not shown here.

The embodiment according to FIGS. 13 and 14 shows the fastening of holding / positioning means on the frame side, although another embodiment of the lever system is also shown in FIG. 13, but this is not dealt with in any more detail here. The frame 1 has on its periphery three holding sections 29 of the frame 1 , only one of which is shown here, such a holding section 29 being articulated via levers 30 to the rest of the frame. The levers 30 are formed in the plane of the frame 1 from cut-outs 31 delimiting them, lever joints 32 being produced by narrow interruptions in these cut-outs. The formation of the lever 30 therefore corresponds to the formation of the positioning lever 5 between lever 6 and weight lever 7 , which have already been described above. The levers 30 in FIG. 13 are arranged on both sides of the holding section 29 , in each case seven parallel to one another.

A holding flange 34 is fastened on the holding section 29 by means of screws 33 and has a frustoconical recess 35 (see FIG. 14). If the entire holding device for the mask 3 in one device, for. B. such a for ion lithography, the frustoconical recess 35 acts together with a fixed projection, such as a ball 36 indicated here, resulting in a good centering of the entire holding device. At this point it should also be mentioned that the position of the frame-side holding / positioning means, here the holding flange 34 , can be preset with respect to the frame 1 with the aid of adjusting means. In the present case, corresponding supplements 37 are provided as adjusting means, but the adjustment can also be made continuously by adjusting screws or the like.

Claims (21)

1. holding device for a mask, with a disk-shaped frame ( 1 ) for holding the mask ( 3 ) by means of several clamps ( 2 ),
characterized in that
the clamps ( 2 ) are mounted with respect to the frame ( 1 ) via levers ( 5 , 6 , 2 ), which enable a relative movement of the clamps with respect to the frame,
the levers are formed in the plane of the frame from the cutouts ( 8 ) delimiting them and lever joints ( 9 , 10 , 11 , 12 , 13 ) are formed by narrow interruptions in the cutouts. 2. Holding device according to claim 1, characterized in that at least three positioning levers ( 5 ) are provided, each having a first joint ( 9 ) with a clamp ( 2 ) and a second joint ( 10 ) with the frame ( 1 ) are connected, wherein the positioners allow movement of the clamps in the radial direction. 3. Holding device according to claim 1 or 2, characterized in that the connection of the joints ( 9 , 10 , 12 , 13 ) is substantially tangential. 4. Holding device according to one of claims 1 to 3, characterized in that the levers ( 5 , 6 , 7 ) allow a relative movement of the terminals ( 2 ) with respect to the frame ( 1 ) in the sen plane. 5. Holding device according to one of claims 1 to 4, characterized in that two-armed weight levers ( 7 ) are provided, in which a first arm ( 7 a) forms a Ge counterweight, and the second arm ( 7 b) in operative connection with a clamp ( 2 ) stands, and between the arms ( 7 a, 7 b) a joint ( 13 ) is formed, which allows the weight lever to rotate in the plane of the frame. 6. Holding device according to claim 5, characterized in that the second arm ( 7 b) of the weight lever ( 7 ) via a joint with the associated clamp ( 2 ) is directly connected. 7. Holding device according to claim 5, characterized in that the second arm ( 7 b) is articulated via at least one intermediate lever ( 6 ) to the clamp ( 2 ). 8. Holding device according to one of claims 2 to 4 and one of claims 5 to 7, characterized in that both a positioning lever ( 5 ) and a weight lever ( 7 ) is assigned to a clamp ( 2 ). 9. Holding device according to one of claims 1 to 8, characterized in that each clamp ( 2 ) consists of a frame-fixed support ( 15 ) and a spring element ( 14 ), the mask ( 3 ) with its edge between the frame-shaped support and the Fe derelement can be pinched. 10. Holding device according to claim 9, characterized in that the spring element ( 14 ) with the aid of an expanding means ( 18 , 21 ) can be temporarily lifted off the frame-fixed support ( 15 ). 11. Holding device according to claim 10, characterized in that the expanding means is a through an axial bore ( 19 ) of the frame ( 1 ) insertable mounting pin ( 18 ). 12. Holding device according to claim 10, characterized in that the expanding means is a radially movable mounting pin ( 21 ) with a conical end surface ( 22 ) which cooperates with an inclined surface ( 23 ) of the spring element ( 14 ). 13. Holding device according to claim 9 or 10, characterized in that the spring element is a resilient wire bracket ( 24 ) which is movable between two stable positions, namely an open and a clamped position. 14. Holding device for a mask ( 3 ), with a disc-shaped frame ( 1 ) for holding the mask, in which the frame can be inserted into a device and frame-side holding / positioning means ( 34 ) are provided, which with device-side holding / Interacting positioning means,
characterized in that
the frame-side holding / positioning means ( 34 , 29 ) are articulated on the frame ( 1 ) via levers ( 30 ), which enable a radial relative movement of the holding / positioning means with respect to the frame,
wherein the levers ( 30 ) are formed in the plane of the frame from this through cutouts ( 31 ) and lever joints ( 32 ) are formed by narrow interruptions in the cutouts. 15. Holding device according to claim 14, characterized in that the levers ( 30 ) seen in the circumferential direction on both sides of a holding / positioning means ( 34 , 29 ) are arranged. 16. Holding device according to claim 14 or 15, characterized in that a plurality of levers ( 30 ) are arranged parallel to one another. 17. Holding device according to one of claims 14 to 16, characterized in that the holding / positioning means ( 34 ) via the lever ( 30 ) to the frame ( 1 ) articulated holding section ( 29 ) of the frame. 18. Holding device according to claim 17, characterized in that on the Halteab section ( 29 ) of the frame ( 1 ), a holding flange ( 34 ) is attached. 19. Holding device according to claim 18, characterized in that the holding flange ( 34 ) has a frustoconical recess ( 35 ) which is associated with a device-fixed projection ( 36 ). 20. Holding device according to claim 19, characterized in that the projection is a ball ( 36 ). 21. Holding device according to one of claims 14 to 20, characterized in that the position of the frame-side holding / positioning means ( 34 ) with respect to the frame ( 1 ) can be preset with the aid of adjusting means ( 37 ).