Abstract:
The invention concerns an electrostatic chuck ( 250 ) comprising an upper ceramic ( 205 ) bearing the substrate ( 200 ) to be treated and a lower ceramic ( 215 ) bearing heating elements ( 225 ) and radio frequency electrodes ( 220 ), said ceramics being permanently bonded together. Said ceramics are preferably bonded together by heated glass and the lower ceramic is fixedly assembled to a pedestal, for example through a soldered bonding.

Description:
RELATED U.S. APPLICATIONS  
       [0001]     Not applicable.  
       STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT  
       [0002]     Not applicable.  
       REFERENCE TO MICROFICHE APPENDIX  
       [0003]     Not applicable.  
       FIELD OF THE INVENTION  
       [0004]     This invention concerns an electrostatic maintenance chuck with radio frequency electrode and built-in thermostatic components. It applies but is not limited to the fabrication of electronic components.  
       BACKGROUND OF THE INVENTION  
       [0005]     In order to achieve the metallization of silicon substrates used for the fabrication of electronic components, for example MOS (Metal Oxide Semiconductor) transistors, aluminum is deposited using PVD (Physical Vapor Deposition). The sought-after optimization of electric performances connected to the gradual decrease of the component sizes, the problems of connection welds and the execution of connecting wells leads the industry to using copper in place of aluminum for the metallization step. It is to be noted that copper is deposited mainly through an electroplating reaction in liquid medium that requires prior depositing of a copper base layer using PVD.  
         [0006]     This base layer has highly critical characteristics. This invention, through its specific properties, contributes to achieving these characteristics.  
         [0007]      FIG. 1  shows a chuck according to the prior art. It shows a substrate  100 , for example a silicon wafer, that rests on an electrostatic chuck  110  provided with a central opening  120  and laterally held by hooks  130 . The chuck itself  110  rests on a support  140  (or base) that contains cooling circuits  150 , heaters  160 . The chuck has a central opening  180 , in the axis of central opening  120  of chuck  110 . Through these openings, gas  190  is injected, for example helium or argon, promoting heat transfers between support  140 , chuck  110  and substrate  100 . RF  170  radio frequency electrodes, if any, are placed on support  140 .  
         [0008]     The presence of two gaps between, on one hand, substrate  100  and electrostatic chuck  110  and, on the other hand, between electrostatic chuck  110  and support  140 , implies problems of temperature rise, temperature control (each gap causes a temperature difference of several tenths of degrees) and temperature uniformity over the surface of substrate  100 .  
         [0009]     The purpose of this invention is to eliminate these disadvantages.  
       BRIEF SUMMARY OF THE INVENTION  
       [0010]     To that effect, this invention concerns an electrostatic chuck characterized in that it includes: 
        an upper ceramic suitable to bear the substrate to be treated, and     a lower ceramic bearing heating elements and radio frequency electrodes, said ceramics being bonded together in a durable manner.        
 
         [0013]     Because of these arrangements, only one gap is present and temperature control and uniformity are made easier and safer and temperature rises quicker. The radio frequency electrodes make it possible to modulate the plasma around the substrate to be treated.  
         [0014]     According to special characteristics, the ceramics are bonded together with heated glass. Because of these arrangements, the bonding is isolating and heavy duty and the stresses and arrangements relating to RF electrode isolation can be reduced as the base can be grounded.  
         [0015]     According to special characteristics, the electrostatic chuck includes a base bearing cooling elements, with the lower ceramic attached to the base in a durable manner.  
         [0016]     According to special characteristics, the lower ceramic is attached to the base through a brazed connection.  
         [0017]     According to special characteristics, the brazing of the brazed connection is made with indium.  
         [0018]     According to special characteristics, the lower ceramic is attached to the base by bonding.  
         [0019]     According to special characteristics, bonding is silver-based.  
         [0020]     Because of each of these arrangements, the lower ceramic and base have a good heat bond and the RF electrodes are isolated from the base.  
         [0021]     According to special characteristics, the lower ceramic has cooling elements.  
         [0022]     According to special characteristics, the lower ceramic is borne by lateral supports attached in a durable manner to said lower ceramic.  
     
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       [0023]     Other advantages, goals and characteristics will become clear from the description below, made in an explanatory but not at all limiting manner based on the attached drawing where:  
         [0024]      FIG. 1  is a schematic cross-section of a chuck according to the prior art,  
         [0025]      FIG. 2  is a schematic cross-section of a first embodiment of an electrostatic chuck according to this invention,  
         [0026]      FIG. 3  is a schematic cross-section of a second embodiment of an electrostatic chuck according to this invention,  
         [0027]      FIG. 4  is a cross-section of the electrostatic chuck shown in  FIG. 2 , and  
         [0028]      FIG. 5  is a perspective view of the electrostatic chuck shown in  FIG. 2 . 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     The components shown in  FIG. 1  have already been presented above.  
         [0030]      FIG. 2  shows an electrostatic chuck  250  according to one embodiment of this invention. It shows a substrate (wafer)  200  resting on an upper ceramic  205  of electrostatic chuck  250 , provided with a gas inlet central opening  210 . Upper ceramic  205  is bonded using bonding agent  260  to a lower ceramic  215  that bears radio frequency RF electrodes  220  and heating elements  225 . The lower ceramic  215  is itself attached in a durable manner to a support  230  (or base) that contains cooling circuits  235 . The lower ceramic  215  has a gas inlet central opening  240  in the axis of the gas inlet central opening  210  on upper ceramic  205 . The base  230  has a gas inlet central opening  245  in the axis of gas inlet central openings  210  and  240  on upper and lower ceramics.  
         [0031]     Through these gas inlet central openings  210 ,  240  and  245 , gas  255  is injected, for example helium or argon, facilitating heat transfers between the upper ceramic  205  and the substrate  200 .  
         [0032]     Thus, according to this invention, there is only one gap between substrate  200  and each of the heating, cooling or radiation elements, which reduces constraints with regard to temperature rise, temperature control (each gap causes a temperature difference of 30 cl) and temperature uniformity over the surface of the substrate  200 .  
         [0033]     Under an especially interesting embodiment, the bonding agent  260  is a bonding agent made of glass that is applied at a temperature where glass is liquid and malleable. The bonding also provides electric isolation between both ceramics. RF  220  radio frequency electrodes are, for example, flat electrodes positioned on the upper face of the lower ceramic  215 . The heating elements  225  are, for example, flat electrodes positioned on the lower face of the lower ceramic  215 .  
         [0034]     The assembling between lower ceramic  215  and base  230  is for example achieved through a brazed connection using indium brazing  270  for good heat conduction bond. Under an alternative embodiment, the assembling between the lower ceramic  215  and the base  230  is achieved through bonding, for example with a silver-based bonding agent  270 . The pins  265  make it possible to handle the wafers.  
         [0035]      FIG. 3  shows an electrostatic chuck  350  according to an embodiment of this invention. It shows a substrate (wafer)  300  resting on an upper ceramic  305  of the electrostatic chuck  350 , provided with a gas inlet central opening  310 . The upper ceramic  305  is bonded, using bonding agent  360 , to a lower ceramic  315  that bears RF radio frequency electrodes  320 , heating elements  325  and cooling circuits  335 . The lower ceramic  315  is itself attached in a durable manner, through its lateral faces, to a support  330 . The lower ceramic  315  has a gas inlet central opening  340  in the axis of the gas inlet central opening  310  on the upper ceramic  305 .  
         [0036]     Through these gas inlet central openings  310  and  340 , gas  350  is injected, for example helium or argon, facilitating heat transfers between the upper ceramic  305  and the substrate  300 . Thus, according to this invention, there is only one gap between substrate  300  and each of the heating, cooling or radiation elements, which reduces constraints with regard to temperature rise, temperature control and temperature uniformity over the surface of the substrate  300 .  
         [0037]     Under an especially interesting embodiment, the bonding agent  360  is a bonding agent made of glass that is applied at a temperature where glass is liquid and malleable. The bonding also provides electric isolation between both ceramics. RF radio frequency electrodes  320  are, for example, flat electrodes positioned on the upper face of the lower ceramic  315 . The heating elements  325  are, for example, flat electrodes positioned on the lower face of the lower ceramic  315 .  
         [0038]     The assembling between lower ceramic  315  and base  330  is for example achieved through a brazed connection using indium brazing  370  for good heat conduction bond. Under an alternative embodiment, the assembly between the lower ceramic  315  and the base  330  is achieved through bonding, for example with a silver-based bonding agent  370 .  
         [0039]      FIG. 4  shows a cross-section and  FIG. 5 a  perspective view of the electrostatic chuck shown in  FIG. 2 . In  FIG. 5 , both ceramics  205  and  215  are separated for explanatory purposes.  
         [0040]      FIGS. 4 and 5  show electrostatic chuck  250  that comprises the upper ceramic  205  and the lower ceramic  215 , central openings  210  and  240 , the layer of bonding agent  260 , RF radio frequency electrodes  220  and heating elements  225 . Six lateral cylindrical recesses  400  parallel to the ceramic axis are made at regular intervals on the ceramics to receive pins  365  used to handle the wafers.