Abstract:
In a device for machining, in particular etching and/or developing, substrates, in particular wafers, in particular etching and/or developing, having a turntable, the turntable has a Venturi gap.

Description:
BACKGROUND OF THE INVENTION 
     The invention relates to a device and method for machining, in particular etching and/or developing, substrates, in particular wafers. 
     The prior art discloses many and various devices for machining substrates. In the field of semiconductors, in particular, rotary or spin coaters for applying photoresist to substrates are known. These rotary or spin coaters are also referred to as “coaters”. Wafers or glass disks or the like are used as substrates. In addition to these “coaters”, the prior art also discloses devices for machining, in particular etching and/or developing, substrates. 
     In this context, attention is drawn, in particular, to EP 1 743 220 A1. The device described in the prior art for the rotary coating of substrates describes a spin coater, which has a rotatable substrate table for horizontal placement of a substrate. The machining medium is distributed by rotating the substrate table. One particular problem is that the machining medium also penetrates to the rear side of the substrate to be processed and modifies it. This leads to damage to the rear side, particularly in the case of double-sided wafers. 
     It is the object of the invention to provide a device for machining, in particular etching and/or developing, substrates, in particular round wafers, in order to machine a wafer in such a way that the rear side thereof is not damaged and/or contaminated, and to provide a method for this purpose. 
     SUMMARY OF THE INVENTION 
     The foregoing object is achieved by providing a device for machining, in particular etching and/or developing, substrates, in particular round wafers, has a turntable, which has a Venturi gap. Compressed air or some other medium is preferably delivered through the Venturi gap. This results in several advantages. The first advantage is that, as a result, the substrate is drawn in in accordance with the Venturi principle, and is held on the turntable and not thrown off, despite the rotation of the turntable. Another advantage is that the rear side remains clean and the treatment medium cannot run onto the rear side and contaminate or damage it. This is particularly advantageous for substrates that are coated or machined on both sides. 
     It is expedient if the Venturi gap has a gap size of 0.01 mm to 0.1 mm, preferably 0.58 mm. Fundamentally, the gap size is dependent on the substrate thickness and size to be machined. 
     In typical embodiments, the device comprises a compressed air source. This has the advantage that the Venturi gap can be supplied with compressed air or pressure medium. As a particularly preferred option, the compressed medium source is suitable for producing an excess pressure of 4 to 8 bar, preferably 6 bar. 
     The device preferably comprises defined edges in order to achieve a defined pressure distribution, especially in the Venturi gap. As a particularly preferred option, the edges are arranged upstream of the Venturi gap. 
     In typical embodiments, the device comprises at least one hole. The at least one hole is preferably arranged in a central area of the turntable, said area facing a substrate. A plurality of holes is preferably arranged in the upper surface. This has the advantage that a reduced pressure or vacuum is prevented from arising between the turntable and a central area of the substrate. This is advantageous since it prevents the substrate from bending or being deformed in some other way in the central area. 
     In typical embodiments, the turntable has a dish shape. This has the advantage that the turntable is very robust and is easy and economical to produce. 
     In typical embodiments, the device has a diffuser. The diffuser is preferably inserted into an interior space of the turntable. 
     As a particularly preferred option, the diffuser forms the Venturi gap with the turntable. As an even more preferred option, the upper surface of the diffuser at least partially forms an area in which a vacuum can form between the wafer and the upper surface. 
     As a particularly preferred option, the underside of the diffuser forms an edge which ensures defined pressure distribution of the pressure medium between the upper surface of the turntable and the underside of the diffuser. 
     As a particularly preferred option, the device, in particular the turntable, comprises a plurality of pins, preferably three or four pins. The pins advantageously have the effect that the wafer slides into a predefined position between the pins. When the wafer is resting on one of the pins, this is detected by a sensor unit, and the machining operation is not set in motion. 
     In typical embodiments, the device comprises a turntable that has a plurality of grooves. The grooves are preferably arranged on a circumferential edge of the turntable. The grooves are preferably arranged in such a way that the wafer or the substrate, when correctly positioned, projects over the grooves. 
     In typical embodiments, the device comprises a gripper. The gripper preferably comprises a plurality of lifting pins. The lifting pins of the gripper are preferably arranged at the same angular intervals as the grooves on the turntable. The lifting pins of the gripper are preferably arranged on a diameter which corresponds to a diameter on which the grooves of the turntable are arranged. This has the advantage that the lifting pins of the gripper can engage in the grooves of the turntable, ensuring that the wafer or the substrate comes to rest on the lifting pins of the gripper. 
     It is furthermore advantageous that the gripper can also be used to deposit the wafer on the table without damaging the gripper. 
     In typical embodiments, the turntable is designed in such a way that a flow of medium or air emerging from the Venturi gap is directed in an area underneath an upper surface of the turntable. This has the advantage that better coating is achieved. This is possible because a flow over an upper surface and hence over a substrate is avoided or reduced. Reducing or avoiding a flow over the substrate ensures better application of coating. First of all, there is less turbulence in the coating medium during application. Moreover, the applied coating is not subjected to any flow either, and, as a result, a better drying result is achieved. Finally, the avoidance or reduction in flow over the upper surface of the substrate table and/or of the substrate avoids the disturbance of dirt or particles which could fall on the fresh coating. 
     For this purpose, the turntable preferably has a chamfer. As a particularly preferred option, the chamfer is arranged on an upper circumferential edge of the turntable, in particular a bottom part of the turntable. 
     The chamfer preferably has a width of 0.5 mm to 10 mm, in particular a width of 1 mm to 5 mm, preferably 3 mm. The chamfer preferably has a height of 0.5 mm to 10 mm, in particular a width of 1 mm to 5 mm, preferably 3 mm. 
     It is expedient if an angle formed between the axis of an upper surface of the turntable and the axis of an upper surface of the chamfer is between 5° and 85°, preferably 20 to 50°, in particular 48°. 
     Protection is sought separately for a method for machining, in particular etching and/or developing, substrates, in particular round wafers, comprising the following steps: rotation of the turntable, application of a machining medium to the turntable, removal of a substrate. 
     In typical embodiments, a slide is positioned in order to place the substrate. During this process, the substrate rests on the slide. The slide is preferably a linear motion element. It is expedient if the slide is moved in such a way that the substrate is positioned over the turntable. The gripper is then positioned under the slide and the substrate in such a way that the substrate rests on the three lifting pins of the gripper. It is expedient if the slide is removed from under the substrate, preferably by means of a linear motion. In a subsequent step, the substrate is preferably deposited on the turntable, in particular between the pins of the turntable. Deposition is preferably accomplished by means of a relative movement between the turntable and the gripper along an axis of rotation of the turntable, wherein the lifting pins of the gripper move through the grooves of the turntable. 
     In typical embodiments, the removal of a substrate is accomplished in a similar manner. For this purpose, a gripper is preferably positioned under the substrate on the turntable, thus enabling the lifting pins of the gripper to engage in the grooves of the turntable from below. 
     By virtue of a relative movement between the turntable and the gripper along an axis of rotation of the turntable, the lifting pins of the gripper engage in the grooves of the turntable, with the result that the substrate rests on three points of the gripper, and the substrate is therefore raised from the turntable. 
     As a particularly preferred option, the slide is positioned under the substrate, and the gripper is removed from under the substrate. The substrate is then moved with the slide away from the turntable. 
     The term “relative movement” is intended to indicate that it is possible both for the gripper to be moved along the axis of rotation in the direction of the turntable and for the turntable to be moved along the axis of rotation in the direction of the gripper by means of a lifting movement. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Further advantages, features and details of the invention will become apparent from the following description of preferred embodiments and from the drawings, in which 
         FIG. 1  shows a schematic illustration of a perspective view of a turntable of a device according to the invention; 
         FIG. 2  shows a schematic illustration of a sectioned side view of the turntable shown in  FIG. 1 ; 
         FIG. 3  shows a schematic illustration of a perspective view of a gripper for a device according to the invention; 
         FIG. 4  shows a schematic illustration of a perspective view of another embodiment of a turntable for a device according to the invention with a wafer; 
         FIG. 5  shows a schematic illustration of a side view of another embodiment of a turntable of a device according to the invention; and 
         FIG. 6  shows a schematic illustration of a perspective view of the turntable shown in  FIG. 5 . 
     
    
    
     DETAILED DESCRIPTION 
       FIG. 1  shows a turntable  1  for a device according to the invention. The turntable  1  has an upper surface  2  for a substrate, in particular a wafer. The turntable  1  has a circular shape. The turntable  1  furthermore has a Venturi gap  3 . The Venturi gap  3  is arranged at the upper surface  2  of the turntable  1 . 
     As can be seen from  FIG. 2 , the turntable  1  comprises a dish-shaped bottom part  4 . 
     A diffuser  5  is inserted into the dish-shaped bottom part  4  of the turntable  1 . The upper surface  6  of the diffuser  5  forms part of the upper surface  2 . 
     The circumferential edge  7  of the diffuser  5  and an inner rim  8  of the dish-shaped bottom part  4  of the turntable form the Venturi gap  3 . 
     In the embodiment under consideration, the Venturi gap has a height of 0.58 mm. The height is measured from a bottom part upper surface  9  of the dish-shaped bottom part  4  to an upper edge  10  of the diffuser  5 . 
     The turntable  1  has an axis of rotation D. 
     The diffuser  5  is inserted into the dish-like bottom part  4  of the turntable  1  in such a way that a gap  11  is formed between the diffuser  5  and the turntable  1 . Defined edges  12  project into the gap  11 . The purpose of the edges  12  is to ensure a defined pressure distribution of a pressure medium, in particular compressed air, flowing through the channel  11  into the Venturi gap  3 . The edges  12  are formed on an underside of the diffuser  5 . 
     The turntable  1  furthermore comprises a plurality of holes  13 . The holes  13  are introduced into the diffuser  5 . 
     The turntable  1  has a duct  14 . A compressed air or compressed medium source  33  is connected to one end  15  of the duct  14 . 
     The turntable  1  has a plurality of pins  16 . These are used to position the substrate or wafer. By virtue of the fact that the substrate comes to rest only between the pins  16 , there is the advantage that precisely defined positioning between the pins can be accomplished. Moreover, this advantageously makes it possible, using a sensor device (not shown), to detect whether the substrate or wafer has come to rest in the predefined position. 
     The turntable according to the invention shown in  FIGS. 1 and 2  operates as follows: 
     A substrate (not shown), in particular a round wafer, is placed on the turntable  1  of  FIGS. 1 and 2 . 
     The turntable  1  is supplied with compressed air by means of a compressed air source connected to the end  15  of the duct  14 . In the process, compressed air flows into the duct  14  through the gap  11  and out of the Venturi gap  3  between the bottom part upper surface  9  of the bottom part  4  and the wafer or substrate. As a result, in accordance with the Venturi principle, a reduced pressure is produced, holding the wafer or the substrate (not shown) on the turntable  1  despite a rapid rotary motion of the turntable  1  about the axis of rotation D. 
     Moreover, this prevents treatment medium, e.g. etchant or developer, applied to an upper side of the substrate from running onto a rear side of the medium and damaging or modifying the latter. 
     Compressed air flows out of the duct  14 , between the upper surface  2  and the substrate or wafer, through the holes  13 . This prevents the formation, in the area of the holes  13 , of a vacuum or a reduced pressure, which would bend the substrate downward, deform it and/or damage it. 
       FIG. 3  shows another embodiment of a turntable  26 . Resting on the latter is a substrate  17 . The construction of turntable  26  is substantially similar to that of turntable  1 . 
     Turntable  26  furthermore has a plurality of grooves  18 ,  19  and  20 . The grooves are introduced at a circumferential edge  25  of the turntable  26  and the length thereof corresponds to a height of the turntable. 
     Moreover, a device according to the invention comprises a gripper  21 , as illustrated in  FIG. 4 . The gripper  21  has three lifting pins  22 ,  23  and  24 . The lifting pins  22  to  24  are arranged on a diameter d. The diameter d corresponds substantially to a diameter of a turntable  1  or  26 . 
     The grooves  18 ,  19  and  20  are arranged at the same angular intervals as the lifting pins  22 ,  23  and  24 . The grooves  18 ,  19  and  20  are preferably likewise arranged on the diameter d. 
     The device according to the invention having a turntable  26  operates as follows: 
     In order to deposit the wafer  17  on the turntable  26 , it is positioned by means of a slide (not shown) at a distance above the turntable  26  which corresponds at least to the height of the slide. 
     The gripper  21  is then moved under the wafer  17 , with the result that the wafer  17  comes to rest by its edges on the three lifting pins  22 ,  23  and  24 . 
     By means of a relative movement between the turntable  26  and the gripper  21 , i.e. either by lowering the gripper  21  in the direction of the turntable  26  or raising the turntable  26  in the direction of the gripper  21 , the wafer  17  is then deposited on an upper surface of the turntable  26 , as shown in  FIG. 3 . During this process, the lifting pins  22 ,  23  and  24  slide through the grooves  18 ,  19  and  20  of the turntable  26  of  FIG. 3 . 
     The gripper  21  is moved relative to the turntable  26  in such a way that the lifting pins  22 ,  23  and  24  can be moved downward out of the grooves  18 ,  19  and  20  in arrow direction P, and the gripper  21  is then removed from the turntable  26  again. 
     The wafer  17  can then be machined, using etchant or developer for example. 
     In order to remove the wafer  17  from the turntable  26 , the procedure is substantially similar to that for deposition but in reverse. 
     The gripper  21  is positioned at the turntable  26 , under the turntable  26 , and is then moved with the lifting pins  22 ,  23  and  24  into the corresponding grooves  18 ,  19  and  20 , counter to arrow direction P. As a result, the wafer  17  rests on the upper side of the lifting pins  22 ,  23  and  24  and is moved away from the turntable  26  with the gripper  21 . 
     The slide (not shown) is then moved under the wafer  17 , and the wafer  17  is removed from the area of the turntable  26  together with the slide. 
       FIG. 5  shows another turntable  27 . Turntable  27  is of substantially similar design to either of turntables  1  and  26 . Turntable  27  comprises a chamfer  28 . This can also be seen in the perspective illustration of the turntable  27  in  FIG. 6 . 
     With the chamfer  28 , an upper edge on a circumference  29  of the turntable  27  has been removed. 
     The chamfer  28  is produced in a bottom part  30 . Bottom part  30  is of substantially similar design to bottom part  4 . 
     The chamfer  28  has the effect that a medium, in particular air, is blown out of a Venturi gap  31  and diverted in arrow direction K. This is advantageous because the medium, in particular the air, is directed into a region below the turntable  27 . This has the advantage that unwanted air turbulence above an upper surface  32  of the turntable  27  is avoided and/or reduced. This is advantageous because better coating of a substrate is achieved as a result. This is possible because the coating is not subjected to any flow when there is a reduced flow over the upper surface of the turntable and/or of the substrate and also because fewer particles can be deposited on the coating by an air flow. 
     In the case of turntable  27 , a flow emerging from the Venturi gap  31  is diverted in the direction of a slope of the chamfer  28  or more steeply by an upper surface  32  of the turntable  27  into an area under an upper surface of the turntable  27 . 
     In the embodiment under consideration, the chamfer  28  has a width b of 0.5 mm to 10 mm, in particular a width of 1 mm to 5 mm, preferably 3 mm. The chamfer  28  preferably has a height h of 0.5 mm to 10 mm, in particular a width of 1 mm to 5 mm, preferably 3 mm.