Vacuum clamping device

Abstract

A vacuum clamping device is used for clamping workpieces, in particular for clamping planar substrates such as wafers, comprising a base plate with an adsorption surface, wherein a plurality of adsorption openings are designed in the adsorption surface of the base plate, wherein the base plate can be connected to at least one negative pressure device through at least one suction pipe, and is characterized in that the adsorption openings are arranged in the edge area of ​​the adsorption surface of the base plate.

Description

Technical Field

[0001] The present invention relates to a vacuum clamping device for clamping workpieces, in particular for clamping flat substrates such as wafers, comprising a bottom plate having an adsorption surface and a plurality of adsorption openings designed in the adsorption surface of the bottom plate, wherein the bottom plate is connected to at least one negative pressure device through at least one suction pipe. Background Art

[0002] In the prior art, such vacuum clamping devices are generally known. Such vacuum clamping devices usually have a vacuum clamping plate (bottom plate) which includes a plurality of adsorption openings distributed on its surface. Vacuum clamping devices of this type are used in various different technical fields.

[0003] Such a technical field is, for example, the processing and inspection of substrates in the form of wafers. In principle, wafers are mostly circular or quadrilateral thin sheets on which there are a plurality of electronic components. During the processing of such wafers, they are usually located on a processing device which may include, for example, a processing table, or within it. The processing table has a holding device, and the wafer to be processed is arranged on the holding device during the processing, and the wafer is, for example, adsorbed on the holding device by means of vacuum.

[0004] According to DE 20 2013 100 632 U1, for example, a vacuum clamping device is known which includes a vacuum clamping plate, wherein the vacuum clamping plate has a plurality of adsorption openings uniformly designed in the adsorption surface. In this known device, another vacuum plate is placed on the vacuum clamping plate. In this known solution, the vacuum plate is designed as a mat which can be closely attached to the workpiece to be clamped when a vacuum is applied. The vacuum plate has a plurality of vacuum channels for this purpose. The vacuum channels are connected to the adsorption openings in the vacuum clamping plate located below the vacuum plate, so that a vacuum can be generated on the surface of the workpiece to be clamped.

[0005] In addition to processing, the inspection of wafers is also an important field of operation. Therefore, after manufacturing the wafers, optical inspection is usually also necessary to detect and eliminate production defects. In this case, the surface of the wafer to be inspected must be inspected by means of light. Particularly preferably, during this optical inspection process, the wafer can be inspected both with incident light and with transmitted light. Before this inspection, it is important to "flatten" the wafer to be inspected. This is usually achieved by means of the vacuum clamping device described above. In this case, vacuum clamping is particularly based on the principle that, outside and inside the vacuum clamping device, which can be designed as a vacuum table, the standard atmospheric pressure of approximately 1 bar is first applied. At this time, the wafer to be clamped is placed on the vacuum clamping device. By means of a vacuum device, such as a vacuum pump, the air inside the vacuum clamping device is evacuated. Thereby, a pressure difference is generated between the inside and the outside, and the boundary layer thereof is the workpiece to be clamped. Thereby, a vacuum is generated between the workpiece (especially the wafer) and the vacuum clamping device. Here, it particularly refers to a negative pressure, which is significantly (i.e., multiplicatively) lower than the ambient pressure, such as the atmospheric pressure. The atmospheric pressure then presses the workpiece onto the vacuum clamping device. Now, the upper side of the workpiece that is already flat can be inspected, and the workpiece will not slip away during this process.

[0006] The disadvantage of the vacuum clamping device known from the prior art is that the optical inspection of the clamped workpiece (especially the wafer) can only be carried out insufficiently, because the suction openings evenly distributed in the suction surface designed on the bottom plate will interfere with the optical inspection or even make it impossible to carry out. These suction openings generate, for example, shadows, which are very disturbing for the optical inspection by incident light or transmitted light. Summary of the Invention

[0007] The object of the present invention is to overcome the disadvantages of the vacuum clamping device originating from the prior art. The object of the present invention is particularly to provide a vacuum clamping device by means of which the workpiece (especially the wafer) can be clamped flat on the bottom plate on the one hand and at the same time undergo optimal optical inspection.

[0008] According to the present invention, this object is achieved by a vacuum chucking device of the type described at the beginning, characterized in that the suction openings are arranged in the edge region of the suction surface of the bottom plate. Here, it is particularly preferable that the suction openings are only arranged at the edge of the suction surface of the bottom plate. It has surprisingly been proven that with the vacuum chucking device according to the present invention, it is possible to optimally clamp and "flatten" the wafer, even if the suction openings are not evenly distributed on the suction surface of the bottom plate, but are arranged in the edge region of the suction surface of the bottom plate. Given the fact that the suction openings are located in the edge region of the suction surface of the bottom plate, the wafer can be detected almost entirely by transmitted light, because there are no interfering openings in the form of suction openings in the surface to be inspected. Thereby, the structure can be detected with maximum contrast. By the vacuum generated between the wafer to be inspected and the suction surface of the bottom plate, the wafer can be pulled completely flat onto the bottom plate designed in the same plane. Therefore, the optical system requires as small a depth of field as possible. Thereby, it is possible to achieve the best optical resolution and the best light efficiency during the detection process.

[0009] To enable optimal optical detection, the bottom plate is usually transparent, particularly made of glass or transparent plastic, such as plexiglass, substantially.

[0010] Advantageously, there is a gap between the suction opening and the edge of the bottom plate, particularly a gap of about 1 mm to about 30 mm. Given the fact that the suction opening is arranged slightly spaced from the edge of the bottom plate, an edge section is created between the suction opening and the outermost edge of the bottom plate, which serves as an external seal when placing the film elaborated in detail below. Thereby, a particularly strong vacuum can be applied between the bottom plate and the workpiece to be inspected.

[0011] Advantageously, the suction opening is designed as circular and preferably has a diameter of about 0.3 mm to 1.5 mm, particularly 0.8 mm to 1.3 mm. This embodiment is easier to manufacture and at the same time has optimal suction characteristics.

[0012] In a preferred embodiment of the vacuum chucking device according to the present invention, the suction channels extending through the bottom plate are each connected to at least two suction openings, and the suction channels preferably expand relative to the suction surface. Through this embodiment, a particularly strong vacuum can be generated quickly between the bottom plate and the workpiece.

[0013] Generally, at least two suction openings have interfaces for the suction pipes and / or are connected to the suction pipes.

[0014] Preferably, the suction openings are arranged on a contour line substantially corresponding to the outer shape of the object to be clamped. Thus, if the object is designed as a square, for example, the suction openings are also arranged in the form of a square.

[0015] If the object to be clamped is a wafer, the suction openings are preferably arranged on an imaginary ring in the suction surface of the bottom plate, which is specifically designed to be flattened at certain parts, and the size of the ring is slightly smaller than the size of the wafer, so that the suction openings can just be covered by the wafer. Through this annular arrangement, a particularly high and uniform vacuum can be generated between the bottom plate of the vacuum clamping device and the wafer to be inspected.

[0016] An improved version of the vacuum clamping device according to the present invention is characterized by a transparent and flexible film arranged between the bottom plate and the workpiece to be clamped, which has suction holes within the range of the edge of the workpiece. Through this film, a significantly arched workpiece can also be flattened onto the bottom plate by means of the vacuum applied between the film and the workpiece. When the vacuum is applied, the film adheres tightly to the workpiece and pulls it almost together onto the bottom plate of the device according to the present invention. In this way, even more arched workpieces can also be placed flat on the bottom plate designed to be flat. Wafers are usually arched (up to 500 μm at most). Since the film is designed to be transparent and also has suction holes only at its edges, it is also possible to perform interference-free optical inspection by means of transmitted light when using this film. When the workpiece is adsorbed onto the bottom plate, the film first takes the shape of the workpiece. If this is achieved, an even stronger vacuum will be built between the film and the bottom plate, causing the entire film to be pulled onto the bottom plate and take the shape of the workbench.

[0017] Preferably, the flexible film described above is made of glass. This film has proven to be particularly advantageous because it is not easily scratched. Different from glass films, films made of, for example, plexiglass are easily scratched, which is disadvantageous during optical inspection with a resolution of 1 μm.

[0018] Advantageously, the film described above protrudes beyond the edge of the workpiece and / or the edge of the bottom plate. Thereby, a particularly stable vacuum can be generated between the film and the bottom plate and thus also between the film and the workpiece to be inspected. Description of the Drawings

[0019] Other features of the present invention result from the following description of the preferred embodiments of the present invention in conjunction with the drawings and the dependent claims. Here, the individual features can be implemented alone or in combination with each other.

[0020] In the drawings:

[0021] Figure 1 A perspective view of the vacuum clamping device according to the present invention is shown;

[0022] Figure 2 Shows Figure 1 The top view of the vacuum clamping device of

[0023] Figure 3a The side view of the vacuum chuck device shown in the open state; Figure 1 ;

[0024] Figure 3b The side view of the vacuum chuck device shown in the closed state; Figure 1 ;

[0025] Figure 4a Shows a cross-section along line B-B of the vacuum chuck device; Figure 3a ;

[0026] Figure 4b Shows a cross-section along line G-G of the vacuum chuck device; Figure 3b ;

[0027] Figure 5 Shows Figure 4b An enlarged partial view (partial K);

[0028] Figure 6 Shows Figure 4a An enlarged partial view (partial C);

[0029] Figure 7 Shows a side view of the vacuum chuck device according to Figure 1 within the vacuum interface range;

[0030] Figure 8 Shows Figure 2 An enlarged partial view (partial A) within the adsorption opening range;

[0031] Figure 9 Shows the vacuum interface shown enlarged;

[0032] Figure 10 Shows Figure 6 An enlarged partial view. DETAILED DESCRIPTION

[0033] Hereinafter, the same or functionally identical features are denoted by the same reference numerals.

[0034] In Figure 1 and Figure 2Shown is a vacuum chucking device according to the invention in the form of a vacuum table 1. Clamped on the vacuum table 1 is a wafer 2 to be optically inspected. The vacuum table 1 includes a bottom plate 3 having a suction surface 4. The bottom plate 3 is made of glass. The wafer 2 lying flat on the bottom plate 3 is designed to be substantially circular, wherein the wafer 2 is designed to be flattened at a location 5 to enable better gripping. A plurality of suction openings 6 are designed in the suction surface 4 of the bottom plate 3. The suction openings 6 are arranged on a virtual ring 6a in the suction surface 4 of the bottom plate 3, which is designed to be flattened at a certain location. The shape of the virtual ring 6a corresponds to the shape of the wafer 2, wherein the ring 6a is designed to be slightly smaller than the wafer 2 such that the wafer 2 just covers the virtual ring 6a together with the suction openings 6. In Figure 8 This arrangement of the suction openings 6 and the wafer 2 can be well recognized. Here, for better illustration, the wafer is shown as transparent so that the suction openings can be seen.

[0035] The vacuum table 1 further includes an upper ring 7, a stop ring 8 connected to the upper ring 7 and for fixing the bottom plate 3, and a lower ring 9. The rings 7, 8 and 9 are made of aluminum and are connected to each other by bolt connections. In Figure 1 and Figure 2 The holes 10 for inserting fastening bolts in the upper ring 7 can be seen. In addition, the upper ring 7 includes a plurality of notches 19. These notches 19 are for embedding correction devices that define a specific degree of vertical mobility of the rings 7, 8 and 9. To relieve the vacuum, the stop ring 8 is slightly lifted. In Figure 3a 、 Figure 4a and Figure 6 This "open position" is shown. In Figure 3b 、 Figure 4b and Figure 5 The "closed position" where the rings 8 and 9 are stacked together is shown.

[0036] The stop ring 8 further includes an O-ring 20, which ensures the best external seal in the closed state of the vacuum table 1. The lifting mechanism of the vacuum table 1 further includes guide rods 11 and a ball bushing 12 connected to the guide rods 11. A cover 13 is preset at the upper end of the ball bushing. In Figure 5 and Figure 6 These components can be well recognized.

[0037] A flexible glass film 14 including suction holes is arranged between the bottom plate 3 and the wafer 2. The suction holes of the glass film 14 are arranged such that they are above the suction openings 6 in the suction surface 4 of the bottom plate 3. Thus, the suction holes in the glass film 14 are also arranged on a virtual ring designed to be flattened at a certain location. To fix the glass film 14, it is clamped between the upper ring 7 and the stop ring 8.

[0038] On the lower side of the vacuum table 1 opposite the bottom plate 3, the vacuum table is enclosed externally by a closing plate 15. In the closed state, the closing plate 15 provides an airtight seal for the internal space 16 between the bottom plate 3 and the closing plate 15.

[0039] To clamp the wafer, the operation is as follows.

[0040] First, with the aid of a transport guide funnel (not shown here), the wafer 2 is placed on the bottom plate 3 such that the wafer 2 covers all the suction openings 6 in the suction surface 4 of the bottom plate 3. As already mentioned above, the arrangement of the suction openings 6 in the bottom plate 3 corresponds to the shape of the wafer 2, where the wafer 2 is designed to be slightly larger than the imaginary, flattened ring 6a on which the suction openings 6 are arranged. Given the fact that the wafer 2 is designed to be only slightly larger than the imaginary ring 6a, the wafer 2 protrudes only minimally beyond the imaginary ring including the suction openings 6 and thus, only a very small section 21 of the wafer 2 extends outside the ring 6a. In this way, wafer material can be saved. There is a glass film 14 between the wafer 2 and the bottom plate 3, and its suction holes are directly positioned above the suction openings 6 of the bottom plate 3.

[0041] The vacuum table 1 enters the closed position at the latest at this time. This is achieved by lowering the stop ring 8 onto the lower ring 9.

[0042] Since the wafer 2 is not straight but is designed to be slightly curved and must be flattened by means of the vacuum table 1, the glass film 14 forms an angle of approximately 3° with the stop ring 8. Thereby, adaptation to the non-planar designed wafer 2 is achieved. In this way, a sufficiently strong vacuum can be built up between the wafer 2 and the glass film 14 more quickly. In Figure 10 the arrangement of the glass film 14 can be well recognized.

[0043] To create a vacuum, air is pumped out of the internal space 16 through the vacuum interfaces 17a and 17b at this time. At least one of these suction openings 6 is connected to a vacuum channel 18, which in turn is in open connection with one of the vacuum interfaces 17a or 17b. By means of the vacuum generated, the wafer 2 is first pulled onto the glass film 14 in the area of the suction opening connected to the vacuum channel 18. This is particularly well achievable because the suction holes in the glass film 14 are positioned directly above the suction openings 6 and the vacuum can act directly on the wafer 2 in this way. All the suction openings 6 are in open connection with each other. This can be achieved, for example, in such a way that the suction openings 6 pass completely through the bottom plate 3 from its upper side to its lower side and are thus in open connection with each other through the internal space 16. Given the fact that the suction openings 6 are in open connection with each other, the vacuum quickly spreads to all the suction openings 6, so that the wafer is finally pulled onto the glass film 14 or the bottom plate 3 through all the suction openings 6. The wafer 2 serves as a kind of "cover plate", and only through this cover plate is it possible to create a vacuum between the wafer and the bottom plate 3 or the glass film 14 and thus pull the wafer 2 flat onto the bottom plate 3. In this flat shape, the wafer 2 can be optically inspected optimally at this time. Given the fact that all the suction openings 6 are arranged in the edge area of the bottom plate 3 and the outermost edge area of the wafer 2 to be inspected, these suction openings 6 do not interfere with the optical inspection of the wafer 2. Thus, except for the outermost edge area, the optical inspection of the wafer 2 can be carried out without disturbing shadows caused by the suction openings because no suction openings are provided within the ring 6a. At the same time, it has been proven that by arranging the suction openings 6 in the outermost edge area of the wafer 2 to be inspected, a very strong vacuum can be generated, through which a non-planar wafer can be pulled flat powerfully and safely.

[0044] In the current embodiment, the diameter of the wafer 2 is 15 cm. The diameter of the suction opening is 0.5 mm.

Claims

1. A vacuum clamping device, the vacuum clamping device is used to clamp a workpiece, the workpiece is a planar substrate, the vacuum clamping device comprises a base plate (3) having an adsorption surface (4), wherein a plurality of adsorption openings (6) are designed in the adsorption surface (4) of the base plate (3), wherein the base plate (3) can be connected to at least one negative pressure device via at least one suction pipe, characterized in that: The adsorption opening (6) is arranged in the edge region of the adsorption surface (4) of the base plate (3), and the vacuum clamping device has a transparent and flexible film (14) arranged between the base plate (3) and the workpiece to be clamped, and the film has adsorption holes in the edge region of the workpiece.

2. The vacuum clamping device according to claim 1, characterized in that: The workpiece is a wafer (2).

3. The vacuum clamping device according to claim 1, characterized in that: There is a gap between the adsorption opening (6) and the outer edge of the bottom plate (3).

4. The vacuum clamping device according to claim 1, characterized in that: There is a gap of 1 mm to 30 mm between the adsorption opening (6) and the outer edge of the bottom plate (3).

5. The vacuum clamping device according to any one of claims 1 to 4, characterized in that: The adsorption opening (6) is designed to be circular.

6. The vacuum clamping device according to claim 5, characterized in that: The suction opening (6) has a diameter of 0.3 mm to 1.5 mm.

7. The vacuum clamping device according to claim 5, characterized in that: The suction opening (6) has a diameter of 0.8 mm to 1.3 mm.

8. The vacuum clamping device according to any one of claims 1 to 4, characterized in that: The adsorption channel (18) extending into the bottom plate (3) is connected to at least one adsorption opening (6).

9. The vacuum clamping device according to claim 8, characterized in that: The adsorption channel expands toward the adsorption surface (4).

10. The vacuum clamping device according to any one of claims 1 to 4, characterized in that: At least two suction openings (6) have a connection for a suction line and / or are connected to a suction line.

11. The vacuum clamping device according to any one of claims 1 to 4, characterized in that: The suction opening (6) is arranged on a contour line corresponding to the outer shape of the workpiece to be clamped.

12. The vacuum clamping device according to claim 11, characterized in that: The suction opening is arranged on a ring (6a) in the suction surface (4) of the base plate (3).

13. The vacuum clamping device according to claim 12, characterized in that: The ring (6a) is designed to be flattened at the location (5).

14. The vacuum clamping device according to claim 11, characterized in that: The suction opening (6) is arranged such that it can be covered by the workpiece to be clamped.

15. The vacuum clamping device according to any one of claims 1 to 4, characterized in that: The bottom plate is made transparent.

16. The vacuum clamping device according to any one of claims 1 to 4, characterized in that: The bottom plate is made of glass or transparent plastic.

17. The vacuum clamping device according to claim 1, characterized in that: The adsorption hole is arranged directly above the adsorption opening (6).

18. The vacuum clamping device according to claim 1, characterized in that: The film (14) is made of glass.

19. The vacuum clamping device according to any one of claims 1, 17 and 18, characterized in that: The film (14) protrudes beyond the edge of the workpiece and / or the edge of the base plate (3).

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