Abstract:
The invention concerns a device and a method for tempering a substrate (S), as well as a method for making such a device, which comprises the following elements: a first subelements ( 10 ) provided with a support surface ( 20 ) to be pressed against the substrate (S) and with a first connecting surface, a second subelement ( 12 ) provided with a second connecting surface ( 28 ) whereby it is pressed at least partly against the first connecting surface ( 10 ). At least one of the two subelements ( 10, 12 ) contains a ceramic material. At least one of the two connecting surfaces ( 22, 28 ) comprises at least one recess ( 24, 30 ) which defines at least one cavity ( 32 ) in the device. At least one first connecting opening enables a thermostatic liquid to be circulated and/or supplied towards and/or from the cavity ( 32 ).

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    The invention relates to a device and a method for regulating the temperature of a substrate, and to a method for producing such a device. 
         [0003]    2. Description of the Related Art 
         [0004]    A substrate holding device in particular for testing circuit arrangements on wafer-type substrates is known from DE 101 22 036 A1. The device described therein has a surface for receiving a substrate to be tested and is formed as an integral ceramic body having layers doped to different extents. In particular, the device can be configured with a doped layer region within the ceramic body which serves as heating. It is thus possible to measure the substrate at relatively high temperatures. Cooling of the substrate is not provided in said device. For this purpose, the holding device has to be combined with a conventional thermochuck. 
         [0005]    Besides an electrical heating, a substrate holding device known from U.S. Pat. No. 5,610,529 B also has electrical cooling elements. Such electrical heating and cooling elements always also cause electrical interference signals which can influence electrical measurements on the substrate whose temperature is to be regulated. For shielding from electrical interference signals, the construction has a layer system composed of electrically conductive and insulating regions between a substrate support area and the heating and cooling elements. 
         [0006]    A cooling in a substrate holding device in which such electrical interference effects are avoided is known from U.S. Pat. No. 6,188,563 B1, which discloses a holding device comprising a ceramic body, in which are formed cooling channels through which a cooling fluid can be conducted, said cooling fluid bringing about a cooling of the substrate. A configuration of said cooling channels in the ceramic body which leads to a homogeneous temperature distribution is difficult, however. A homogeneous temperature distribution which can, moreover, also be controlled in a wide temperature range is particularly important, however, for many applications. 
         [0007]    Therefore, it is an object of the present invention to provide a device and a method for regulating the temperature of substrates which enable a control of the temperature for cooling and/or for heating the substrate in conjunction with a high homogeneity of the temperature distribution, and also a method for producing such a device for regulating the temperature of substrates. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention provides a device for regulating the temperature of a substrate comprising:
       a first partial element which has a bearing area for bearing against the substrate and also a first connecting area, and   a second partial element, which has a second connecting area, via which it bears indirectly or directly at least partly against the first connecting area of the first partial element,   wherein at least one of the two partial elements comprises ceramic material,   at least one cutout which defines at least one cavity in the device is provided at least in one of the two connecting areas, and   at least one first connection opening is provided via which a temperature-regulating fluid inflow and/or outflow to and/or from the at least one cavity is made possible.       
 
         [0014]    The device according to the invention therefore provides an integral device for regulating the temperature of a substrate by means of a temperature-regulating fluid which can be introduced into the cavity of the device or passed out from the cavity via the connection opening. In particular, the two-part construction of the device enables diverse configurations—adapted to the respective application—of the cavity that is arranged between the two partial elements or is provided at or by the interface. A homogeneous temperature distribution and also a good thermal coupling of the temperature-regulating fluid to the device are made possible as a result. Moreover, the use of ceramic material increases the thermal stability. 
         [0015]    Preferably, the two partial elements essentially comprise ceramic material, that is to say that they comprise at least one ceramic core or an element body on ceramic material (e.g. aluminum oxide or aluminum nitride) which forms the major constituent or the main constituent of the partial elements. In this case, the main constituent represents the essentially shaping part of the partial elements. 
         [0016]    Preferably, in the device in addition to the first connection opening at least one second connection opening is provided via which a fluid outflow and/or inflow from and/or to the at least one cavity is made possible. Moreover, the cavity preferably forms at least one continuous channel between the first and the second connection opening. This enables a continuous through-flow of the temperature-regulating fluid, wherein one connection opening serves as inflow and the other as outflow for the fluid. The open-loop or closed-loop control of the substrate temperature is thereby facilitated by means of an open-loop or closed-loop control of the temperature and/or a quantity or flow rate of the flowing fluid. 
         [0017]    Preferably, the at least one continuous channel runs essentially in meandering fashion, that is to say that it preferably has loops in which it essentially reverses its course locally. This improves the thermal coupling of the temperature-regulating fluid to the device, on the one hand, and the homogeneity of the temperature distribution, on the other hand. 
         [0018]    The continuous channel is further preferably arranged in such a way that a fluid throughflow from the first connection opening through the channel to the second connection opening takes place essentially on the basis of the countercurrent principle. The channel is thus arranged in such a way that, at least with respect to a first section of the channel, a second section of the channel exists which runs essentially parallel and is adjacent to said first section, wherein the fluid flows in approximately opposite directions in the two channel sections. This has the effect that a temperature gradient that forms in the flow direction of the fluid on account of the energy transfer between fluid and device in the first channel section opposes an approximately opposite temperature gradient on account of the opposite flow direction in the adjacent second channel section. An improved temperature homogeneity is thus achieved at the bearing area for the substrate. In this case, it is particularly preferred if two connection openings of the same channel are already adjacent and the channel sections run essentially parallel to one another in meandering fashion from the connection openings through the entire device. 
         [0019]    Preferably, ribs are formed in the channel, the longitudinal direction of said ribs running essentially in the direction of the channel. This brings about a large surface area in the channel region and hence a good thermal coupling of the temperature-regulating fluid to the device. 
         [0020]    Preferably, in each case at least one cutout is provided in both partial elements, which cutouts together form the at least one cavity. Particularly preferably, the connecting areas lie essentially in a connecting plane, wherein the cutouts are formed in the two partial elements symmetrically with respect to the connecting plane. A symmetrical configuration of the two partial elements is particularly advantageous for the production of ceramic partial elements since an adaptation of the partial elements to one another is largely maintained even after a possible shrinkage of the partial elements during the firing of the ceramic. Moreover, a symmetrical configuration of the partial elements brings about an essentially identical thermal expansion behavior. 
         [0021]    Preferably, the partial elements are connected to one another in fluid-tight fashion at the connecting areas in such a way that a fluid can emerge from the cavity essentially only via the at least one connection opening. 
         [0022]    Preferably, a connecting layer is arranged at least at one of the two connecting areas. Said connecting layer facilitates, inter alia, the sealing of the connecting areas and/or the adhesion of the partial elements to one another. In this case, it is particularly preferred if the at least one connecting layer is configured at least in part as an electrically conductive layer preferably comprising nickel or copper. Electrical interference signals can be shielded by this electrically conductive layer, which is desirable particularly for electrical measurements on the substrate whose temperature is to be regulated. It is most preferred if, for this purpose, the conductive connecting layer projects beyond the connecting area in order to form an electrical connection contact which is accessible in particular from outside the device. 
         [0023]    Preferably, an electrically conductive first shielding layer is arranged at least partly or in regions at the bearing area of the first partial element. Said first shielding layer enables the shielding of electrical interference signals in addition or as an alternative to an electrically conductive connecting layer. However, it could also be electrically conductively connectable to the substrate in order thus to bring the substrate to a specific electrical potential. Particularly preferably, said first shielding layer has at least one electrical connection contact. 
         [0024]    Preferably, the second partial element additionally has an outer area or mounting area at which an electrically conductive second shielding layer is arranged at least in regions. Particularly preferably, said outer area or mounting area is an area which is remote from the connecting area and plane-parallel thereto. Like the first shielding layer or the connecting layer, the second shielding layer could bring about a shielding from electrical interference signals and preferably have an electrical connection contact. 
         [0025]    The simultaneous configuration of the temperature-regulating device with the electrically conductive connecting layer and the first and second electrically conductive shielding layer is particularly preferred. It is thus advantageously possible to bring about a triax connection of the three layers, wherein the first shielding layer is or can be connected to force potential, the electrically conductive connecting layer is or can be connected to guard potential and the second shielding layer is or can be connected to shield or ground potential. This brings about a particularly good shielding from electrical interference signals and thus permits highly sensitive noise-free electrical measurements on the substrate. 
         [0026]    Preferably, an integrated heating element is arranged and/or an external heating element can be fitted at the outer area or mounting area of the second partial element. Particularly in the combination of a cooling fluid with a heating element, a rapid and advantageously precise closed-loop or open-loop control of temperature is possible. Moreover, the device can be used with conventional thermochucks or hot plates. 
         [0027]    The first partial element is preferably configured in a cylindrical fashion, wherein the first connecting area and the bearing area form plane-parallel base areas. 
         [0028]    Moreover, the present invention provides a method for producing a device for regulating the temperature of a substrate comprising the following steps in this order:
   (a) providing a first partial element having a bearing area and a first connecting area and a second partial element having a second connecting area, wherein at least one of the two partial elements comprises ceramic material;   (b) forming at least one cutout in at least one of the two connecting areas;   (c) connecting the first connecting area of the first partial element to the second connecting area of the second partial element in such a way that the cutout forms a cavity in the device.   
 
         [0032]    The production according to the invention of a device for regulating the temperature of a substrate composed of two partial elements simplifies the configuration of the at least one cutout that forms the cavity after the connection of the partial elements, whereby a particularly individual cavity configuration adapted to the problem can be performed. Moreover, the use of ceramic material increases the thermal stability or enables higher temperatures and/or leads to a higher strength. 
         [0033]    Preferably, step (c) of connecting the two partial elements comprises a step of brazing. 
         [0034]    Preferably, step (a) of providing the first and second partial element comprises a step of forming the first and/or second partial element as a first and/or a second green blank composed of ceramic material. In this case, preferably a green blank composed of ceramic raw material which preferably comprises a ceramic powder mixture is produced in a form determined by the desired final form of the first and/or second partial element taking account of the dimensional change arising in the subsequent method steps. Consequently, preferably a first and/or a second green blank having a first or a second connecting area is produced. 
         [0035]    Preferably, the method additionally comprises a step of firing the first and/or second green blank. As a result, a (preferably very much) harder first and/or second partial element arises from the preferably relatively readily deformable green blank. This is preferably done by means of a sintering process which the firing step preferably comprises and in which mechanically stronger ceramic material arises from a low-strength ceramic raw material at high temperatures. 
         [0036]    Preferably, step (b) of forming the at least one cutout is effected before the step of firing the corresponding partial element in which the cutout is formed. A mechanical processing of the corresponding partial element can be carried out more easily in the non-fired state, that is to say in the green state, than in the fired, that is to say hardened, state. Preferably, a post-processing is effected after firing in order to carry out corrections in particular of faults produced by deformation of the partial element during firing. Typically, such partial elements shrink by 20% to 30% from the green state to the fired state. This shrinkage can possibly take place non-uniformly. 
         [0037]    Preferably, the method additionally comprises a step of forming at least a first electrically conductive shielding layer at the bearing area of the first partial element and/or a second electrically conductive shielding layer at an outer area of the second partial element. Preferably, forming the first and/or second shielding layer comprises a step of sputtering and/or vapor deposition of electrically conductive material, which preferably comprises metal. The step of forming the first and/or second shielding layer further preferably takes place after a step of firing the corresponding partial element. In this case, the at least one shielding layer could be formed before or after step (c) of connecting the two partial elements. 
         [0038]    Moreover, the method comprises (preferably before step (c) of connecting the two partial elements) an additional step of depositing an electrically conductive layer on at least one part or region of at least one of the two connecting areas. Particularly preferably, said step takes place after step (b) of forming the at least one cutout. The at least one conductive layer is preferably formed as part of a connecting layer, via which the two partial elements are connected in step (c). The step of depositing said at least one conductive layer preferably comprises a step of sputtering and/or vapor deposition of electrically conductive material, which preferably comprises metal. Said layer preferably forms an essentially closed, continuous layer, which is particularly preferably arranged at the entire at least one connecting area. 
         [0039]    Moreover, the present invention provides a method for regulating the temperature of a substrate, comprising the following steps:
       providing a device for regulating the temperature of a substrate according to the present invention or a preferred embodiment;   arranging the substrate at least partly against the bearing area;   supplying and/or discharging a fluid to and/or from the at least one cavity via the at least one first connection opening.       
 
         [0043]    Preferably, in this case the fluid is supplied to the at least one cavity via the at least one first connection opening and is discharged from the at least one cavity via the at least one second connection opening. 
         [0044]    Particularly preferably, in this case, the temperature and/or the flow rate of the supplied fluid is varied for the open-loop or closed-loop control of the temperature of the substrate. In this case, the temperature and/or the flow rate of the supplied fluid can preferably be controlled in a manner dependent on a signal of a temperature sensor provided in or at the device and/or at the substrate. 
         [0045]    Preferably, a device according to the invention with vacuum grooves formed in the bearing area of said device is provided in the temperature-regulating method and the temperature-regulating method in this case preferably additionally comprises a step of sucking up the substrate by means of the vacuum grooves. 
         [0046]    Preferably, a device having an electrically conductive connecting layer at at least one of the two connecting areas, an electrically conductive first shielding layer at the bearing area and an electrically conductive second shielding layer at an outer area of the second partial element is provided in the temperature-regulating method, wherein
       the first shielding layer is electrically conductively connected to force potential, the second shielding layer is electrically conductively connected to shield potential, and   the connecting layer is electrically conductively connected to guard potential.       
 
         [0049]    Preferably, in the temperature-regulating method, a heating element is arranged at an outer area of the second partial element, wherein an open-loop or closed-loop control of the temperature of the substrate comprises an open-loop or closed-loop control of the temperature and/or of the heating power of the heating element. 
         [0050]    Overall, preferably the device according to the invention and its preferred embodiments can be produced by the production method according to the invention. Preferably, moreover, the method products of the preferred embodiments of the production method according the invention represent preferred embodiments of the device according to the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0051]    The invention is described by way of example below with reference to accompanying drawings of preferred embodiments. In this case: 
           [0052]      FIG. 1  shows a cross section of a first preferred embodiment of a device according to the invention for regulating the temperature of a substrate. 
           [0053]      FIGS. 2A-2C  in each case show a plan view of the first connecting area of the first partial element in accordance with further preferred embodiments of the device according to the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0054]      FIG. 1  shows a cross section of a preferred embodiment of the device according to the invention for regulating the temperature of a substrate, wherein a first partial element  10  and a second partial element  12  are shown, which each comprise a preferably essentially cylindrical first ceramic body  14  and second ceramic body  16 , respectively. By way of example, aluminum oxide or aluminum nitride is suitable as ceramic material therefor. At an essentially planar (preferably circular) base area of the first ceramic body  14 , an electrically conductive first shielding layer  18  is provided which forms a bearing area  20  of the first partial element  10 . For regulating the temperature of a substrate S (e.g. semiconductor wafer), the latter is brought into contact at least in regions with the bearing area  20 . In this case the substrate S is preferably in areal contact with the bearing area  20 . 
         [0055]    The first shielding layer  18  preferably comprises metal (e.g. gold or nickel) and has a layer thickness in the direction of the normal to the bearing area  20  which lies within a range of approximately 1 μm to a few 10 μm. In the embodiment shown, the first shielding layer  18  projects beyond the bearing area  20  and not only covers the planar area of the first ceramic body  14  but additionally has edge regions that at least partly cover the cylindrical lateral area of said ceramic body. Besides an additional electrical shielding effect, said edge regions can also serve as electrical connections. Consequently, the electrically conductive first shielding layer  18  preferably has at least one contact-making region which projects beyond the bearing area  20  and is electrically conductively connected to the first shielding layer  18  arranged at the bearing area  20 . Preferably, vacuum grooves for sucking up the substrate S are formed in or at the bearing area. 
         [0056]    Moreover, the first partial element  10  has a first connecting area  22 , which is essentially remote from the bearing area  20  and is plane-parallel thereto. First cutouts or recesses  24  are provided in the first connecting area  22  of the first partial element  10 . Moreover, an electrically conductive connecting layer  26  is arranged at the first connecting area  22 . The connecting layer  26  is interrupted in the region of the first cutouts  24 . Preferably, however, the interfaces or surfaces of the first cutouts  24  could also be coated with an electrically conductive layer which, together with the connecting layer  26 , forms a closed electrically conductive layer. The electrically conductive connecting layer  26  preferably projects beyond the first connecting area or is formed in such a way as to form an electrical connection contact. 
         [0057]    The second partial element  12  has an essentially planar second connecting area  28 , via which it is arranged onto the first connecting area  22  of the first partial element  10  and is or can be connected to said partial element (indirectly/directly). In this case, the connecting layer  26  preferably comprises copper or nickel and connects the two partial elements to one another by brazing. 
         [0058]    In the second connecting area  28  of the second partial element  12 , second cutouts  30  are formed in such a way that, together with the first cutouts  24  in the first partial element  10 , they form cavities  32 . As at the interfaces or surfaces of the first cutouts  24 , at least one conductive layer could alternatively or additionally be arranged at the interfaces or surfaces of the second cutouts  30 , which, together with the connecting layer  26 , forms a closed electrically conductive layer. One or a plurality of ribs  34  are formed in the cutouts  24 ,  30  and project into the cavities  32  in order to enlarge the surface areas of the cutouts  24 ,  30  which serve as contact areas for a temperature-regulating fluid. The energy transfer between temperature-regulating fluid and temperature-regulating device is thus improved. The good thermal coupling of the temperature-regulating fluid to the device is particularly advantageous for a rapid and/or precise closed-loop or open-loop control of the temperature. 
         [0059]    The second cutouts  30 , with regard to the connecting areas, are preferably arranged essentially symmetrically or mirror-symmetrically with respect to the first cutouts  24 . Preferably, the entire second partial element  12  is formed essentially symmetrically or mirror-symmetrically with respect to the first partial element  10 . In particular, the ceramic bodies  14 ,  16  are formed essentially symmetrically with respect to one another. This facilitates in particular the adaptation of the two partial elements during the production of the temperature-regulating device. 
         [0060]    Moreover, the second partial element  12  has an outer area or mounting area  38 , at which an electrically conductive second shielding layer  38  is or can be arranged. The second shielding layer  38  is preferably configured analogously to the first shielding layer  18 . Preferably, a heating element  40  is arranged at the outer area  36 . The heating element  40  can either be fixedly connected to the outer area  36  or be arranged onto the outer area  36  in a releasable manner. The closed-loop or open-loop control of the temperature can additionally be supported with the aid of said heating element  40 . In order to enable an accurate closed-loop control of the temperature, the first partial element  10  or lower part has a temperature sensor  42 , which is preferably formed by a thermistor (e.g. PT100). 
         [0061]    In one preferred embodiment of the method according to the invention for regulating the temperature of a substrate, electrical potentials are respectively applied to the electrically conductive shielding layers  18 ,  38  illustrated in  FIG. 1  and the electrically conductive connecting layer  26  in a triaxial interconnection. For this purpose, they are electrically conductively connected at laterally formed contacts. In this case, preferably, the first shielding layer  18  is connected to force potential, the connecting layer  26  is connected to guard potential and the second shielding layer  38  is connected to shield or ground potential. For regulating the temperature of the substrate S, preferably a temperature-regulating fluid (that is to say a cooling or heating fluid) is introduced into the cavities  32 , heating or more accurate temperature control preferably being effected by means of the heating element  40 . As an alternative, the temperature of the substrate could also be increased by a heating fluid without the heating element  40  being necessary for this purpose. 
         [0062]      FIGS. 2  show preferred configurations of the first cutouts  24  in a plan view of the first connecting area  22  of the first partial element  10 . 
         [0063]    In  FIG. 2A , the cavities  32  are formed as a multiplicity of annular channels  44  which are connected to a first connection opening  50  via an essentially radially running inflow channel  46  and to a second connection opening  52  via an essentially radially running outflow channel  48 . A temperature-regulating fluid introduced through the first connection opening  50  can therefore be distributed between the annular channels  44  via the inflow channel  46  and can be conducted out of the device again through the second connection opening  52  via the outflow channel  48 . An essentially continuous flow of the temperature-regulating fluid is thus achieved. In particular, the fluid emerging through the second connection opening  52  can be fed back into the device again through the first connection opening  50  after it has been brought to a desired temperature by an external heating or cooling. Said temperature can be controlled for example in a manner dependent on a signal from the temperature sensor  42 . In this embodiment, it is particularly preferred if the through-flow cross section of the individual annular channels  44  is individually adapted to its length. Thus, by way of example, a larger through-flow cross section of the outer annular channels can lead to an increase in the flow rate and thus to a matching of the through-flow times of the fluid through the individual annular channels. It is particularly preferred if the average through-flow time in all the channels is essentially identical in magnitude. A higher homogeneity of the temperature distribution can thus be achieved. 
         [0064]      FIG. 2B  shows a further preferred embodiment of the cavities  32 . The latter are formed as a singly continuous, that is to say non-branched, channel which runs essentially in meandering fashion. 
         [0065]      FIG. 2C  likewise shows an essentially meandering course of a singly continuous channel. In particular, said channel is designed on the basis of the countercurrent principle, that is to say that, with respect to each first channel section  54 , there is an adjacent second channel section  56  which runs essentially parallel thereto and in which the temperature-regulating fluid flows essentially oppositely to the direction in the first channel section  54 . As a result, an oppositely running temperature gradient in the second channel section  56  is adjacent to a temperature gradient in the first channel section  54  which arises as a result of the fluid taking up or emitting energy from or to the temperature-regulating device. Consequently, it is possible to compensate for local temperature differences between the channel sections at least over distances that are larger than the channel spacing, which results in a particularly homogeneous temperature distribution in the region of the bearing area  20 . In the case of the channel shown in  FIG. 2C , the countercurrent principle is realized essentially in the entire course of the channel. 
         [0066]    In a further embodiment (not shown), the first partial element  10  preferably has a vacuum connection, with the aid of which the substrate S can be sucked up via grooves in the bearing area  20 . Said grooves preferably have flanked areas which form an angle of less than 90° with the bearing area  20 . A closed conductive layer can thus be achieved when the first shielding layer  18  is applied by sputtering. If the grooves had flank areas running perpendicular to the bearing area  20 , or if the flanks even had an overhanging structure, a metal film applied by sputtering from a direction perpendicular to the bearing area  20  could be interrupted at said flanks and regions of the first shielding layer  18  would be formed which were not electrically conductively connected to the rest of the shielding layer. Preferably, the cutouts  24 ,  30  could also have a corresponding flank structure in order to be able to achieve a closed conductive layer also in the region of the cutouts and the connecting areas  22 ,  28 . 
         [0067]    In a departure from the preferred embodiments shown, in a further preferred embodiment (not shown) of the present invention, the cutouts could be provided only in one of the two partial elements. The other partial element would then preferably have a continuous or closed planar connecting area. Moreover, the first shielding layer  18  could form only a part of the bearing area  20 . The size and form of the shielding layer could be adapted in particular to the substrate S whose temperature is to be regulated. In this case, the remaining areas of the bearing area  20  could be formed by the first ceramic body  14 . Likewise, the second shielding layer  38  could form only a part of the outer area  36 . One of the conductive layers (e.g. the conductive layer  38 ) can likewise serve as a temperature sensor by virtue of the temperature dependence of the resistance of the layer being used for determining the temperature (in a manner similar to a PT100 sensor). 
         [0068]    In one preferred embodiment of the production method according to the invention, firstly the ceramic bodies  14 ,  16  of the two partial elements  10 ,  12  are produced as green blanks in an essentially cylindrical form. In the as yet unhardened state, that is to say as green blanks, the ceramic bodies  14 ,  16  can still be shaped relatively easily. Therefore, the cutouts  24 ,  30  are at least partly formed as early as in this state. In this case, the cutouts could be produced together with the cylindrical form. Afterward, the green blanks are dried and fired. The ceramic bodies thereby essentially attain their final hardness and thermal stability. The ceramic bodies  14 ,  16  shrink typically by about 20% to 30% during drying and hardening. Their form can also change slightly in the process. In the case of a symmetrical configuration of the ceramic bodies  14 ,  16 , an essentially symmetrical deformation (e.g. shrinkage) also results, whereby the adaptation of the two ceramic bodies with respect to one another is largely maintained. Preferably, the ceramic bodies  14 ,  16  and in particular the cutouts  24 ,  30  thereof are post-processed (preferably mechanically) after firing. In this case, the connecting areas  22 ,  28  are preferably also planarized. 
         [0069]    Preferably, grooves are provided at the bearing area  20 , via which grooves the substrate can be held against the bearing area by means of a vacuum. Said grooves can already be formed in the green blanks. However, it is also possible for the grooves to be produced in the fired state. 
         [0070]    Preferably electrically conductive shielding layers  18 ,  38  are then deposited on the ceramic bodies. This is preferably done by sputtering, vapor deposition, in particular by CVD (chemical vapor deposition), electrolytic deposition or application (e.g. by means of a solvent). 
         [0071]    In this case, the grooves previously formed in the bearing area preferably have a profile which results as cross section of the grooves in a plane perpendicular to their longitudinal direction and which preferably has essentially a “V” or “U” form. Some other form of the profile of the grooves which results from a combination of straight and/or curved lines is also conceivable. Consequently, the surfaces of the grooves are preferably formed by a combination of planar and/or curved areas. In this case, the surfaces of the grooves preferably form an angle of less than 90° with the bearing area. In the case of an essentially “U”-shaped profile, this essentially means an extension of the cross section from the groove base or vertex to the edge thereof via which the grooves adjoin the bearing area. During the deposition of the shielding layer  18 , this results in a closed covering of the ceramic body in the region of the bearing area and the grooves. This avoids regions of the shielding layer  18  with which electrical contact is not made. 
         [0072]    The two partial elements are finally preferably connected to one another by brazing. Copper or silver solder on nickel used for brazing can in this case simultaneously serve as an electrically conductive connecting layer which brings about a shielding from electrical interference signals. Furthermore, a co-fixing method, in which the two partial elements are fired together by the use of a glaze layer, or likewise an adhesive bonding of the two partial elements is conceivable. 
         [0073]    In this case, it is particularly advantageous if the bearing areas are connected to one another in fluid-tight fashion in such a way that the temperature-regulating fluid can flow in and out only via the connection openings and does not emerge from the channels in other regions.