Patent Publication Number: US-2023132980-A1

Title: Vapor chamber

Description:
TECHNICAL BACKGROUND 
     The present disclosure generally concerns the cooling of systems, such as mechanical systems or electronic systems. More particularly, the disclosure concerns a cooling device of “vapor chamber” type and its manufacturing method. 
     PRIOR ART 
     Many systems, such as mechanical systems or electronic systems, may be subject to overheating phenomena likely to damage them or to damage the environment where they are operating. An efficient way to counter overheating phenomena is the use of cooling devices. 
     There exist several types of cooling devices, such as air conditioning systems, heat pipes, vapor chambers, etc. It is current to associate a cooling device with a system likely to overheat by positioning it close to a hot spot of the system. 
     It would be desirable to be able at least partly improve the disadvantages of existing cooling devices and of their manufacturing methods. 
     SUMMARY OF THE INVENTION 
     There is a need for higher-performance cooling devices. 
     There is a need for higher-performance vapor chambers. 
     There is a need for higher-performance cooling device manufacturing methods. 
     There is a need for vapor chamber manufacturing methods better adapted to the series manufacturing of vapor chambers. 
     An embodiment overcomes all or part of the disadvantages of known vapor chambers. 
     An embodiment overcomes all or part of the disadvantages of known vapor chamber manufacturing methods. 
     An embodiment provides a method of manufacturing a vapor chamber comprising the following successive steps: 
     (a) etching, in a first substrate, at least one first cavity extending from an upper surface of said first substrate, and at least one channel extending from the upper surface of said first substrate, a first end of said channel emerging into said at least one cavity;
 
(b) bonding a lower surface of a plate to the upper surface of said first substrate, the plate comprising at least a first region made of a ductile material arranged in front of said first end of said channel;
 
(c) filling said channel with a cooling fluid; and
 
(d) closing said cavity by applying a pressure on said region made of a ductile material of the plate to obstruct said first end of said channel.
 
     According to an embodiment, during step (d), said first cavity is tightly closed. 
     According to an embodiment, the first substrate is made of a material selected from the group comprising: a semiconductor material, silicon, a metal, a metal alloy, glass. 
     According to an embodiment, the ductile material is made of a polymer material or of a metal such as copper, silver, aluminum, gold, or an alloy of these metals. 
     According to an embodiment, during step (a), second cavities are etched from the upper surface of said first substrate. 
     According to an embodiment, said channel couples said first cavity and said second cavities. 
     According to an embodiment, the first and second cavities are coupled in series by said channel. 
     According to an embodiment, the first and second cavities are coupled in parallel by said channel. 
     According to an embodiment, said plate comprises an opening arranged above a first portion of said channel. 
     According to an embodiment, the first portion of the channel is a second end of said channel. 
     According to an embodiment, said channel comprises a third end emerging onto an opening at the periphery of the first substrate. 
     According to an embodiment, the method further comprises a step (e) executed between steps (b) and (c), during which a quasi-vacuum or vacuum is created in said at least one first cavity. 
     According to an embodiment, said first region of said plate extends all along the length of said plate. 
     According to an embodiment, the cooling liquid is selected from the group comprising: water, helium, hydrogen, oxygen, nitrogen, sulfur, neon, argon, methane, krypton, mercury, ammonia (NH3), acetone (C3H6O), ethane (C2H6), pentane (C5H12), heptane (C7H16), ethanol (C2H5OH), methanol (CH3OH), ethylene glycol (C2H6O2), toluene (C7H8), naphthalene (C10H8), trichlorofluoromethane (CCl3F, also known under trade name Freon 11), dichlorofluoromethane (CHClL2F, also known under trade name Freon 21), chlorodifluoromethane (CHClF2, also known under trade name Freon 22), 1,1,2-Trichloro-1,2,2-trifluoroethane (C2Cl3F3, also known under trade name Freon 113), the fluid known under trade name Flutec PP2, the fluid known under trade name Flutec PP9, the fluid known under trade name Dowtherm, the fluid known under trade name Novec, and derivatives and mixtures of these fluids. 
     Another embodiment provides a vapor chamber manufactured according to the previously-described method. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The foregoing features and advantages, as well as others, will be described in detail in the rest of the disclosure of specific embodiments given by way of illustration and not limitation with reference to the accompanying drawings, in which: 
         FIG.  1    shows a simplified functional cross-section view of a vapor chamber associated with an electronic device; 
         FIG.  2    shows a simplified cross-section view of an embodiment of a vapor chamber; 
         FIG.  3    shows three simplified top views of embodiments of vapor chambers of  FIG.  2   ; 
         FIG.  4    shows two cross-section views of a portion of a vapor chamber of  FIG.  2   ; 
         FIG.  5    shows two cross-section views of another portion of a vapor chamber of  FIG.  2   ; 
         FIG.  6    shows a top view schematically illustrating an alternative embodiment of a vapor chamber of  FIG.  2   ; 
         FIG.  7    shows three cross-section views illustrating steps of an implementation mode of a method of manufacturing vapor chambers of  FIG.  2   ; 
         FIG.  8    shows three cross-section views illustrating other steps of the implementation mode of the method of  FIG.  7   ; 
         FIG.  9    shows four cross-section views illustrating other steps of the implementation mode of the method of  FIG.  7   ; 
         FIG.  10    shows four cross-section views illustrating steps of an implementation mode of another method of manufacturing the vapor chamber of  FIG.  2   ; 
         FIG.  11    shows four cross-section views illustrating steps of an implementation mode of still another method of manufacturing vapor chambers of  FIG.  2   ; 
         FIG.  12    shows two cross-section views illustrating steps of an implementation mode of still another method of manufacturing the vapor chamber of  FIG.  2   ; 
         FIG.  13    shows six cross-section views illustrating steps of an implementation mode of a method of manufacturing an electronic system; and 
         FIG.  14    shows two cross-section views illustrating other steps of the implementation mode of the method of  FIG.  13   . 
     
    
    
     DESCRIPTION OF THE EMBODIMENTS 
     Like features have been designated by like references in the various figures. In particular, the structural and/or functional features that are common among the various embodiments may have the same references and may dispose identical structural, dimensional and material properties. 
     For the sake of clarity, only the steps and elements that are useful for an understanding of the embodiments described herein have been illustrated and described in detail. 
     Unless indicated otherwise, when reference is made to two elements connected together, this signifies a direct connection without any intermediate elements other than conductors, and when reference is made to two elements coupled together, this signifies that these two elements can be connected or they can be coupled via one or more other elements. 
     In the following disclosure, unless otherwise specified, when reference is made to absolute positional qualifiers, such as the terms “front”, “back”, “top”, “bottom”, “left”, “right”, etc., or to relative positional qualifiers, such as the terms “above”, “below”, “upper”, “lower”, etc., or to qualifiers of orientation, such as “horizontal”, “vertical”, etc., reference is made to the orientation shown in the figures. 
     Unless specified otherwise, the expressions “around”, “approximately”, “substantially” and “in the order of” signify within 10%, and preferably within 5%. 
       FIG.  1    is a functional simplified cross-section view of an electronic system  100  comprising a vapor chamber  150 . 
     Electronic system  100  is assembled on a substrate  200 , for example, via connection balls  201 . Substrate  200  is for example a solid substrate or a printed circuit board, etc. 
     Electronic system  100  is formed of an electronic device  120  and of vapor chamber  150 . 
     Electronic device  120  is of any type, and may comprise all or part of an electronic component, one or a plurality of components, one or a plurality of circuits, for example, one or a plurality of printed circuits, etc. These components are represented, in  FIG.  1   , by a layer  121 . Device  120  further comprises a hot spot  123 , that is, an area likely to generate a significant heat, or an area likely to overheat. This hot spot may correspond to a component, an assembly of components, a lead, etc. Hot spot  123  is represented, in  FIG.  1   , by a block  123 . 
     Vapor chamber  150  comprises a cavity  151  formed in a substrate  153 . Cavity  151  is filled with a cooling fluid  155 . On the walls of cavity  151  is arranged a capillary wick structure  157 . 
     Vapor chamber  150  is arranged to help cooling the hot spot  123  of device  120 . A lower surface  158  of cavity  151  is positioned against the hot spot  123  of electronic device  120 , this surface is called evaporator. An upper surface  159  of electronic device  120 , opposite to surface  158 , is called condenser. Upper surface  159  may be placed against a heat sink, not shown in  FIG.  1   . 
     Vapor chamber  150  operates as follows. In the idle state, that is, when hot spot  123  dissipates no heat, fluid  155  is at equilibrium between its gaseous phase, or vapor phase, and its liquid phase. When hot spot  123  generates heat, the fluid  155  directly close to hot spot  123  evaporates, and creates a motion of vapor within cavity  151 . More particularly, fluid  155  in vapor phase moves away from surface  158 , for example, towards surface  159 , which is symbolized, in  FIG.  1   , by an arrow F 1 . Once the fluid  155  in vapor phase reaches surface  159  of the cavity, it encounters capillary wick structure  157  and condenses to recover its liquid phase. The heat is thus released on the capacitor side, for example in a heat sink. This phenomenon is symbolized by arrows F 2 . The temperature of fluid  155  then decreases and it returns to its initial position by following arrows F 3 . 
       FIG.  2    is a cross-section view of an embodiment of a vapor chamber  300 . 
     Vapor chamber  300  is formed in a substrate  301 . According to an embodiment, substrate  301  is made of a semiconductor material, for example, silicon, or is made of a metal or a metal alloy, or glass. Vapor chamber  300  comprises a cavity  303  extending from an upper surface  305  of substrate  301 . Cavity  303  has a depth smaller than the thickness of substrate  301 , for example in the range from 1 μm to 1 mm, preferably from 10 μm to 800 μm. According to an example, cavity  303  has, in top view, a substantially rectangular shape, for example, substantially square, having an area in the range from 1 mm 2  to 10 cm 2 . A stack of layers  307  is deposited at the bottom of cavity  303  to form a capillary wick structure. According to an example, capillary wick structure  307  is a structure called “wick” capable of comprising porous structures such as grooves or metal foams, such as copper foams having pores with minimum dimensions in the order of 1 μm. According to an example, the capillary wick structure may be a porous structure manufactured from a substrate, for example, made of copper or of silicon, having grooves, for example with a width in the order of from 1 μm to 1 mm, and/or columns, for example with a width in the order of from 1 μm to 1 mm, formed therein. The bottom of cavities  303  is the condenser of vapor chamber  300 . 
     The upper opening of cavity  303  is tightly closed by a plate  309 . Plate  309  is for example made of the same material as substrate  301 , for example, silicon or a metal. Plate  309  is attached, for example, bonded, to substrate  301 . According to an example, when substrate  301  and plate  309  are made of silicon, the upper surface  305  of substrate  301  and the lower surface of plate  309  are oxidized to perform a molecular bonding based on silicon oxide. In  FIG.  2   , the bonding area of substrate  301  and of plate  309  is represented by an adhesive layer  311 . Other examples of tight assembly method are disclosed in relation with  FIG.  9   . Plate  309  forms the evaporator of vapor chamber  300 . According to a variant, plate  309  may be directly formed from an electronic device to be cooled, a manufacturing method illustrating this case is described in relation with  FIGS.  13  and  14   . 
     According to an embodiment, vapor chamber  300  further comprises a channel  313  for filling cavity  303 . Channel  313  is a trench formed from the upper surface  305  of substrate  301 . According to an embodiment, channel  313  is shallower than cavity  303 . Examples of cross-section shapes of channel  313  are described in relation with  FIG.  4   . A first end  315  of the channel emerges onto cavity  303 , and a second end  317  of channel  313  is used as a filling hole. The second end, or filling hole,  317  is closed by a plug  318 . Plug  318  may be formed by seal welding. The arrangement of filling hole  317  is described in further detail in relation with  FIG.  5   . 
     Cavity  303  is filled with a cooling fluid  319 . Fluid  319  has been introduced into cavity  303  through channel  313 , and end  315  has been tightly sealed, after filling, by the ductile material  321  forming part of plate  309 . Ductile material  321  may be made of a polymer material, such an epoxy resin, or of a metal such as copper, silver, aluminum, gold, or an alloy of these metals. Implementation modes of vapor chamber manufacturing methods are described in relation with  FIGS.  7  to  14   . 
     Cooling fluid  319  is a fluid which, at the idle temperature of vapor chamber  300 , is at equilibrium between its liquid phase and its gaseous phase. According to a variant, cooling fluid  319  may be at equilibrium between its liquid phase, its gaseous phase, and its solid phase. The idle temperature of vapor chamber  300  is defined as being the normal operating temperature of the system to be cooled with which vapor chamber  300  is associated, that is, the operating temperature when the system to be cooled is not overheating. According to an embodiment, cooling fluid  319  is selected from the non-exhaustive group comprising: water, helium, hydrogen, oxygen, nitrogen, sulfur, neon, argon, methane, krypton, mercury, ammonia (NH 3 ), acetone (C 3 H 6 O), ethane (C 2 H 6 ), pentane (C 5 H 12 ), heptane (C 7 H 16 ), ethanol (C 2 H 5 OH), methanol (CH 3 OH), ethylene glycol (C 2 H 6 O 2 ), toluene (C 7 H 8 ), naphthalene (C 10 H 8 ), trichlorofluoromethane (CCl 3 F, also known under trade name Freon 11), dichlorofluoromethane (CHCl 2 F, also known under trade name Freon 21), chlorodifluoromethane (CHClF 2 , also known under trade name Freon 22), 1,1,2-Trichloro-1,2,2-trifluoroethane (C2Cl3F3, also known under trade name Freon 113), the fluid known under trade name Flutec PP2, the fluid known under trade name Flutec PP9, the fluid known under trade name Dowtherm, the fluid known under trade name Novec, and derivatives and mixtures of these fluids. 
     A system to be cooled may be associated with vapor chamber  300  by being positioned, for example, on an upper surface  323  of plate  309 , that is, on the evaporator side. 
     The advantages of vapor chamber  300  are described in relation with  FIGS.  3  to  14   . 
       FIG.  3    shows three top views (a), (b), and (c) of a plurality of a vapor chambers  400  of the type of the vapor chamber  300  described in relation with  FIG.  2   . 
     Each view (a), (b), (c) shows an example where nine vapor chambers  400  are simultaneously formed in a same substrate (not shown in views (a) to (c)). It is obvious that it is possible to simultaneously form more or less than nine vapor chambers  400  by adapting the arrangement thereof. Vapor chambers  400  are arranged in three rows and three columns. Vapor chambers  400  are simultaneously filled by being connected to common filling channels. Views (a) to (c) show different embodiments of common filling channels. More particularly, views (a) and (b) show embodiments where vapor chambers  400  are coupled “in series” and view (c) shows an embodiment where vapor chambers  400  are coupled “in parallel”. 
     View (a) shows an embodiment where all the vapor chambers  400  of a same row are coupled “in series” by a same filling channel  410 . More particularly, each vapor chamber  400  comprises an inlet  400 IN and an outlet  400 OUT, each coupled to filling channel  410 . Each vapor chamber  400  is coupled to the next one by filling channel  410 . Each filling channel is ended by a filling hole  412 . In other words, in the embodiment shown in view (a), three vapor chambers  400  are coupled in a same row by a same filling channel  410 , and these three vapor chambers  400  are filled with a cooling fluid through a same filling hole  412 . 
     According to a variant, all the vapor chambers of a same column may be coupled “in series” in the same way. 
     View (b) shows an embodiment, similar to that shown in view (a), where all the vapor chambers  400  of a same row are coupled “in series” by a same filling channel  410 . Conversely to the embodiment of view (a), channels  410  are all coupled to a filing hole  420  common to all channels. In other words, in the embodiment shown in view (b), three vapor chambers  400  are coupled by a same filling channel  410 , and the nine vapor chambers  400  are filled with a cooling fluid through a same filling hole  420 . 
     According to a variant, all the vapor chambers of a same column may be coupled “in series” in the same way. 
     View (c) shows an embodiment where all the vapor chambers  400  are coupled “in parallel” by a filling channel  430 . More particularly, vapor chambers  400  comprise a single inlet  400 IN coupled to filling channel  430 . Filling channel  430  is coupled to a single filling hole  432 . Thus, the nine vapor chambers  400  are coupled by a same filling channel  430  and are filled with a cooling fluid through a same filling hole  432 . 
     An advantage of the embodiments disclosed in  FIG.  3    is that a plurality of vapor chambers may be simultaneously formed and filled with cooling fluid. Once the vapor chambers have been filled, the filling channels are sealed, and the vapor chambers may be individualized by using, for example, sawing methods. 
       FIG.  4    shows two cross-section views (a) and (b) of a filling channel of a cavity of a vapor chamber of the type of the filling channel  313  described in relation with  FIG.  2    or of the channels  410  and  430  described in relation with  FIG.  3   . Views (a) and (b) illustrate different shapes capable of being used to form a channel for filling a cavity of a vapor chamber. 
     View (a) shows a filling channel  501  formed in a substrate  503 . Filling channel  501  has, in cross-section, a rectangular or for example square shape. 
     View (b) shows a preferred embodiment of a filling channel  510  formed in substrate  503 . Filling channel  501  has, in cross-section, a trapezoidal shape. More particularly, channel  510  has an upper opening  511  having a width greater than the width of its bottom  513 . Thus, the walls  515  of channel  510  are not vertical but inclined. 
     Channels  501  and  510  are formed by using a step of masking, for example, by lithography, then a step of etching of substrate  503 . According to an example, the depth of channels  501  and  510  may be in the range, for example, from 1 μm to 1 mm, for example from 10 to 800 μm. 
       FIG.  5    shows two cross-section views (a) and (b) of a hole for filling a cavity of a vapor chamber of the type of the filling hole  317  described in relation with  FIG.  2    or of the type of the filling holes  412 ,  420 , and  432  described in relation with  FIG.  3   . 
     Views (a) and (b) show a partial view of a vapor chamber of the type of that described in relation with  FIG.  2   . Views (a) and (b) more precisely show an end  603  of a filling channel  601  formed in a substrate  605 . An upper surface  607  of substrate  605  is bonded to the lower surface  611  of a plate  609  as described in relation with  FIG.  2   , which is represented by an adhesive layer  613 . 
     View (a) shows an embodiment of a “vertical” filling hole  620  having the end  603  of filling hole  601  coupled thereto. More particularly, filling hole  620  is formed in plate  609 , and is arranged above end  603  during the bonding of plate  609  onto substrate  605 . As illustrated in  FIG.  5   , filling hole  620  may have dimensions similar to the dimensions of filling channel  601 , or filling hole  620  may be wider than channel  601 . According to an example, hole  620  may be formed before or after the bonding of plate  609  onto substrate  601 . 
     View (b) shows an embodiment of a “horizontal” filling hole  630  having the end  603  of filling channel  601  coupled thereto. More particularly, filling hole  630  is formed in substrate  605  and emerges onto the lateral edge of substrate  605 . Filling hole  630  may have dimensions similar to the dimensions of filling channel  601  or, as illustrated in  FIG.  5   , filling hole  630  may be wider than channel  601 . According to an example, hole  630  may be formed at the end of the manufacturing method, for example, by a sawing step. 
       FIG.  6    is a simplified and schematic top view showing an embodiment of a vapor chamber  650 . 
     Vapor chamber  650  is a variant of the vapor chamber  300  described in relation with  FIG.  2   . Vapor chambers  300  and  650  have common elements, only their differences are highlighted herein.  FIG.  6    shows the following elements of vapor chamber  650 : 
     cavity  303 ; 
     filling channel  313 ; and 
     filling hole  317 . 
     Vapor chamber  650  differs from vapor chamber  300  in that it comprises support pillars  651 , or pillars  651 , arranged in cavity  303  enabling to help the mechanical hold of plate  309  (not shown in  FIG.  6   ) on cavity  303 . In  FIG.  6   , four pillars  651  are shown. Those skilled in the art will be able to adjust the number and the location of pillars  651  to optimize the hold of plate  309  on cavity  303 . Further, in  FIG.  6   , the pillars have been shown as having the shape of a beam with a substantially square cross-section but, according to another example, pillars  651  may have a substantially rectangular or substantially circular cross-section. Further, pillars  651  may also be covered with the capillary wick structure. Pillars  651  are for example made of a same material as that of the substrate having cavity  303  formed therein. 
       FIGS.  7  to  9    show cross-section views illustrating steps of an implementation mode of a method of manufacturing three vapor chambers of the type of the vapor chamber  300  described in relation with  FIG.  2   . More particularly,  FIG.  7    shows three cross-section views (a), (b), and (c) illustrating steps of preparation of a plate of the type of the plate  309  described in relation with  FIG.  2   .  FIG.  8    shows three cross-section views (a), (b), and (c) illustrating steps of preparation of a substrate of the type of the substrate  301  described in relation with  FIG.  2   .  FIG.  9    shows four cross-section views (a), (b), (c), and (d) illustrating steps of forming of vapor chambers of the type of that described in relation with  FIG.  2    by assembly of the plate of  FIG.  7    and of the substrate of  FIG.  8   . 
     As previously mentioned,  FIG.  7    illustrates steps of preparation of a plate  700  of the type of the plate  309  described in relation with  FIG.  2   . 
     View (a) of  FIG.  7    illustrates the forming, in a substrate  701 , of cavities  703  and  704 . In view (a), one cavity  704  is shown and two cavities  703  are shown. According to an example, substrate  701  is for example made of a semiconductor material, for example, a material comprising silicon. Cavities  703  and  704  extend from an upper surface  705  of substrate  701 . Cavities  703  are intended to be filled with ductile material, and cavity or cavities  704  are intended to form vertical filling holes of the type of that described in relation with  FIG.  5   . In top view, cavities  703  are wider than the vapor chamber filling channels. According to an alternative embodiment, cavity or cavities  704  may not be formed at this step, but after the assembly with the substrate described in relation with  FIG.  9   . According to another alternative embodiment, when the vapor chambers use one or a plurality of filling holes called horizontal, as described in relation with  FIG.  5   , cavity or cavities  704  are not formed. 
     According to an example, cavities  703  and  704  are formed by using a masking step, for example a lithography step such as a photolithography step, then a step of etching of the unmasked portions, for example by using a wet etching method, or a dry etching method, such as a dry reactive ion etching (DRIE). 
     View (a) further illustrates the optional forming of an adhesive layer  707  on the upper surface  705  of substrate  701 . According to an example, the forming of an adhesive layer may be a deposition of the adhesive layer, for example, by inkjet deposition. According to another example, if substrate  705  is made of silicon, the forming of the adhesive layer may be a step of oxidation of the surface of the substrate to prepare a molecular bonding step. 
     View (b) illustrates a step of deposition of a ductile material  709  in cavities  703 . Ductile material  709  may be a resin, a polymer, a metal, fusible glass, or also a combination or a stack of a plurality of these elements. The method of deposition of ductile material  709  depends on the nature of the ductile material. According to an example, the deposition method may comprise one or a plurality of anneal steps. Similarly, the thickness of ductile material  709  also depends on the nature of the ductile material. 
     According to an example, ductile material  709  may comprise an epoxy resin, such as a filled epoxy resin. In this case, methods of lamination type may be used, such as a WOLM (Plate Level Over Molding) method. The deposition step may be followed by an step of anneal, for example, a polymerization anneal. Ductile material  709  may have a maximum thickness in the order of 500 μm, for example, of 300 μm. 
     According to another example, ductile material  709  may comprise copper, silver, aluminum, gold, an alloy of metals used for solders, etc. In this case, the deposition method may be an electroplating, a metal paste silk-screening, a vapor phase deposition method, etc. The deposition step may be followed by an anneal step. Ductile material  709  may have a maximum thickness in the order of 100 μm. 
     For ductile material  709  to only be deposited in cavities  703 , the rest of the structure of view (a) may be masked. According to a variant, ductile material  709  may be deposited over the entire structure of view (a) and then removed from the areas where it is not useful. In this case, the ductile material may be for example removed by a polishing method. 
     View (c) illustrates a step of thinning of the structure of view (b) to obtain plate  700 . The structure of view (b) is thinned from a rear surface  711  of substrate  701  to reach the bottom of cavities  703  and  704  so as to leave ductile material  709  apparent. The thinning method is for example a grinding method. Plate  700  has thus been formed. Plate  700  may have a thickness in the range from 50 μm to 50 mm. According to an example, if plate  700  is made of silicon, its thickness is in the range from 500 μm to 1 mm. 
     As previously mentioned,  FIG.  8    illustrates steps of preparation of a substrate  750  of the type of the substrate  301  described in relation with  FIG.  2   . 
     View (a) illustrates a step of etching of cavities  751  in substrate  750 . The step of etching of cavities  751  may comprise a masking step and then a step of etching of substrate  750 , such as a Bosch etch step. According to an embodiment, a cavity  751  is formed in substrate  750 , cavity  751  being intended to form a vapor chamber. Cavity  751  extends from an upper surface  753  of substrate  750 . According to an example of embodiment, cavities  751  may have a depth in the range from 5 μm to 1 mm, preferably in the range from 60 to 500 μm. 
     Further, pillars  752  are formed in cavity  751 . Two pillars  752  are shown in the views of  FIG.  8   . Pillars  752  are of the same type as the pillars  651  described in relation with  FIG.  6   . Pillars  752  are for example formed by masking during the etching of cavity  751 . 
     View (b) illustrates a step of etching of a filling channel  755  in substrate  750 . Filling channel  755  has at least one end  757  which emerges onto cavity  751 . Channel  755  has, in top view, a shape similar to those described in relation with  FIG.  3   . The step of etching of channel  755  may comprise a masking step and then a step of etching of substrate  750 , such as a Bosch etch step. Channel  755  extends from the upper surface  753  of substrate  750 . Channel  755  has a depth smaller than the depth of cavity  751 . The channel preferably has a smaller depth than its width in top view, for example with a width-to-depth ratio in the range from 1 to 10. Channel  755  has a depth in the range from 10 to 200 μm. Channel  755  has a width in the range from 10 to 500 μm. 
     View (c) illustrates the optional forming of an adhesive layer  759  on the upper surface  753  of the substrate  701  obtained in view (b). According to an example, the forming of an adhesive layer may be a deposition of the adhesive layer. According to another example, if substrate  750  is made of silicon, the forming of the adhesive layer may be a step of oxidation of the surface of the substrate to prepare a molecular bonding step. 
     View (c) further illustrates the forming of a capillary wick structure  761  in the bottom  763  of cavity  751 . According to an example, capillary wick structure  761  is formed by using a step of Bosch etching of a pillar or of trenches using a lithography and an etching. According to an alternative embodiment, capillary wick structure  761  may be formed at an etch step common with the etching of channels  755 . 
     Substrate  750  is thus ready for its assembly to the plate  700  described in view (c) of  FIG.  7   . 
     As previously mentioned,  FIG.  9    illustrates the carrying out of steps of manufacturing of vapor chambers of the type of that described in relation with  FIG.  2    by assembling the plate  700  of  FIG.  7    and the substrate  750  of  FIG.  8   . 
     View (a) illustrates the positioning of the plate  700  of view (c) of  FIG.  7    on the substrate  750  of view (c) of  FIG.  8   . More particularly, plate  700  is flipped, to have adhesive layer  707  in front of the adhesive layer  759  of substrate  750 . Plate  700  is positioned above the substrate so that the portions of ductile material  709  are arranged in front of an end  757  of channel  755  emerging onto the cavity  751  of substrate  750 , and that cavities  704  are arranged in front of another end of channel  755  intended to be coupled to a filling hole. Plate  700  and substrate  750  are aligned in front of each other with a maximum accuracy in the order of 1 μm. 
     View (a) further illustrates the bonding of plate  700  onto substrate  750 . The bonding method used herein depends on the nature of adhesive layers  707  and  759 . According to an example, the bonding may be a direct bonding, a hydrophilic direct bonding, a molecular bonding, a polymer bonding, a bonding using sintered glass, a eutectic sealing, a thermocompression bonding, etc. The bonding method may comprise polishing steps, anneals, pressurizations or the creation of vacuum. A method requiring no adhesive layers may also be used. 
     View (b) illustrates a step of filling of cavity  751  with a cooling fluid  760  of the type of the cooling fluid  319  described in relation with  FIG.  2   . The filling method used at this step is the following:
         removing the gases present in cavity  751 ;   introducing cooling fluid  760  into cavity  751 .       

     The gases present in cavity  751  are removed by creating vacuum, or quasi-vacuum, in cavity  751  by coupling it to a vacuum pump. The creation of vacuum may be followed by a degassing at high temperature of the walls of cavity  751 , enabling to remove the residual chemical species that may be absorbed by the material of substrate  750 . 
     The introduction of cooling fluid  760  is performed by injection of the precise volume of fluid  760  necessary to fill cavity  751 . Fluid  760  may be degassed before its introduction. Fluid  760  is more particularly introduced into cavity  704  of plate  700  and then passes into channel  755  to fill cavity  751 . 
     View (c) illustrates a step of closing of cavity  704 . The filling of cavity  751  is ended, and the filling holes, that is, cavities  704 , are tightly closed, for example, by a plug  761  installed by seal welding. 
     View (d) illustrates a step of sealing of channel  755  and of cavity  751 . This sealing step comprises crushing ductile material  709  in channel  755  to fill a portion of channel  755  with ductile material  709 , and thus close the access to cavity  751 . This step may in practice be carried out in several ways, for example by thermocompression of ductile material  709 , by pressing by means of a mold, etc. In  FIG.  9   , the method used is a pressing by means of a mold  765 . The maximum pressing force that can be used is in the order of 100 kN. According to an example, mold  765  may be manufactured from a substrate made of the same material as substrate  750 , for example, of silicon, or of a metal. Mold  765  may be the result of a succession of steps of masking, etching, and polishing, for example by nanoimprint. More particularly, the mold comprises raised areas arranged in front of the portions of plate  700  made of ductile material  709 . Raised areas  767  may have a rectangular or trapezoidal cross-section. 
     According to a variant, to improve the tightness of the sealing of channel  755 , the walls of channel  755  may be previously treated with an adhesion promoter material such as hexamethyldisilazane (HDMS), or by depositing on the wall a bonding layer, for example, made of a titanium and copper alloy. 
     A vapor chamber of the type of the vapor chamber  300  described in relation with  FIG.  2    is thus obtained at the end of the method. 
       FIG.  10    shows four cross-section views (a), (b), (c), and (d) illustrating steps of a variant of the manufacturing method described in relation with  FIGS.  7  to  9   . More particularly, views (a) to (d) illustrate an alternative implementation mode of the method of manufacturing plate  700  described in relation with  FIG.  7   , and its assembly to the substrate  750  described in relation with  FIG.  8   . 
     View (a) illustrates a step of deposition, on a substrate  801 , of a layer  803  of ductile material. Layer  803  is more particularly deposited on an upper surface of  805  of substrate  801  and fully covers this upper surface  805 , it is then spoken of a full plate deposition. Substrate  801  is for example made of a semiconductor material, for example, a material comprising silicon. Layer  803  is made of a ductile material of the type of the ductile material  709  described in relation with  FIG.  7   , and its deposition method depends on the nature of the ductile material. Layer  803  has a thickness, for example, in the range from 20 to 200 μm. 
     View (b) illustrates a step of thinning of substrate  801  from its rear surface  807 . The thinning method is for example a grinding method. The thickness of substrate  801  may then be smaller than 200 μm. 
     View (c) illustrates the etching of cavities  809  and  811  in substrate  801 . In view (c), one cavity  809  is shown and two cavities  811  are shown. Cavities  809  and  811  are etched from the rear surface  807  of substrate  801  and all the way to a lower surface  813  of layer  803 . Cavities  809  are intended to become filling holes, like the cavities  704  of  FIG.  7   . Like the cavities  704  of  FIG.  7   , cavities  809  may not be formed at this step, but after the assembly with substrate  750 , or never be formed. Cavities  811  are intended to allow the crushing of the ductile material of layer  803  during the sealing of cavities  751 . According to an example, when substrate  801  is made of silicon, the etch methods used may be via etching methods. 
     View (d) illustrates the assembly of the structure  814  of view (c) with the substrate  750  of view (c) of  FIG.  8   . As described in relation with  FIG.  9   , and more particularly view (a) of  FIG.  9   , the structure of view (c) is flipped, to have its upper surface  815  in front of the adhesive layer  759  of substrate  750 . Like plate  700 , structure  814  is positioned above the substrate so that cavities  811  are arranged in front of the end  757  of channel  755  emerging onto cavity  751 , and so that cavities  809  are arranged in front of another end of channel  755  intended to be coupled to a filling hole. Structure  814  and substrate  750  are aligned in front of each other with a maximum accuracy in the order of 1 μm. 
     View (d) further illustrates the bonding of structure  814  to substrate  750 . The bonding method used herein is similar to that disclosed in relation with view (a) of  FIG.  9   . 
     View (d) further illustrates the forming of the vapor chamber filling hole  817 . Filling hole  817  is formed by etching of the portion of layer  803  present under cavity  809 . 
     The rest of the vapor chamber manufacturing method is similar to that described in relation with views (b) to (d) of  FIG.  9   . 
     An advantage of the method of  FIG.  10    is that it enables to decrease the number of manufacturing steps with respect to the method described in relation with  FIGS.  7  to  9   . 
       FIG.  11    shows four cross-section views (a), (b), (c), and (d) illustrating steps of another variant of the manufacturing method described in relation with  FIGS.  7  to  9   . More particularly, views (a) to (d) illustrate an alternative implementation mode of the method of manufacturing the plate  700  described in relation with  FIG.  7   . 
     View (a) illustrates the temporary bonding of a substrate  901  to a support substrate  903  via an adhesive layer  905 . Substrates  901  and  903  are for example made of a semiconductor material, for example, a material comprising silicon. Adhesive layer  905  is for example a glue layer. It is a temporary bonding with the same type of glue as those used in 3D integration. 
     View (b) illustrates a step of thinning of substrate  901  from its upper surface  906 . The thinning method is for example a grinding method. The thickness of substrate  901  may then be smaller than 200 μm. 
     View (b) further illustrates the etching of cavities  907  and  909  in substrate  901 . In view (b), one cavity  907  is shown and two cavities  909  are shown. Cavities  907  and  909  are etched from an upper surface  906  of substrate  901  and all the way to an upper surface  911  of layer  905 . Cavities  907  are intended to become filling holes, such as the cavities  704  of  FIG.  7    or the cavities  809  of  FIG.  10   . Cavities  909  are intended to be filled with ductile material. The etch methods used are similar to those used for the etch step illustrated in relation with view (a) of  FIG.  7   . 
     View (c) illustrates a step of deposition of a ductile material  913  in cavities  909 . Ductile material  913  is of the type of the ductile material  709  described in relation with  FIG.  7   , and its deposition method depends on its nature. Material  909  has a thickness, for example, in the range from 20 to 100 μm. For ductile material  913  to only be deposited in cavities  909 , the rest of the structure is for example masked in a previous step. 
     View (d) illustrates the assembly of the structure of view (c) with the substrate  750  of view (c) of  FIG.  8   . As described in relation with  FIG.  9   , and more particularly view (a) of  FIG.  9   , the structure  915  of view (c) is flipped, to have its upper surface  906  in front of the adhesive layer  759  of substrate  750 . Like plate  700 , structure  915  is positioned above the substrate so that cavities  909  are arranged in front of the end  757  of channel  755  emerging onto cavity  751 , and so that cavities  907  are arranged in front of another end of channel  755  intended to be coupled to a filling hole. Structure  915  and substrate  750  are aligned in front of each other with a maximum accuracy in the order of 1 μm. 
     View (d) further illustrates the bonding of structure  915  to substrate  750 . The bonding method used herein is similar to that disclosed in relation with view (a) of  FIG.  9   . 
     The next step of the manufacturing method is not shown herein. This step comprises separating support substrate  903  from substrate  901 . For this purpose, glue layer  905  and support substrate  903  are removed, for example, by a thermal treatment, by a UV treatment, or also a chemical treatment. 
     Like the method described in relation with  FIG.  10   , an advantage of the method of  FIG.  11    is that it enables to form a plate having a thickness smaller than 200 μm. 
       FIG.  12    shows two cross-section views (a) and (b) illustrating steps of another variant of the manufacturing method described in relation with  FIGS.  7  to  9   . 
     More particularly, views (a) and (b) illustrate an alternative embodiment where a substrate  1000 , similar to the substrate  750  described in relation with  FIG.  8   , is associated with a plate  700 . Substrate  1000  differs from substrate  750  in that it further comprises raised areas  1001  arranged in filling channels  755 . Substrates  1000  and  750  having common elements, only their differences will be highlighted. 
     View (a) illustrates a step of preparation of a substrate  1000  similar to the step illustrated in relation with view (b) of  FIG.  8   . At this step, channel  755  is etched in substrate  1000 , and raised areas  1001  are formed in this channel  755 . Raised areas  1001  are arranged at the level of the ends  757  of channel  755  emerging onto cavity  751 . Raised areas  1001  may have a height in the range from 1 to 50 μm, for example from 5 to 30 μm. 
     According to an example, the etching of raised areas  1001  and of channel  755  may be performed according to the following succession of steps:
         first etching of the channel down to a first depth P 1 ;   masking of the areas intended to form raised areas  1001 ; and   second etching forming channel  755  down to a second depth P 2 .       

     View (b) illustrates a step of manufacturing of a vapor chamber similar to the step illustrated in relation with view (d) of  FIG.  9   . At this step, channel  755  and cavity  751  are sealed by crushing of ductile material  709 . Raised areas  1001  being arranged under the portions of plate  700  of ductile material  709 , material  709  is crushed on raised areas  1001 . This step may use the same methods as those described in relation with view (d) of  FIG.  9   , such as, for example, the use of mold  765 . According to an example, not shown in  FIG.  12   , raised areas  767  may have their shape adapted to the shape of raised areas  1001 . 
     An advantage of this embodiment is for the raised areas to enable to more efficiently seal the vapor chambers. 
     Another advantage of this embodiment is that the raised areas may enable to more easily position plate  700  above substrate  1000 . 
       FIGS.  13  and  14    show cross-section views (a), (b), (c), (d), (e), (f), (g), and (h) illustrating steps of an implementation mode of a method of manufacturing an electronic system  1100 . 
     View (a) of  FIG.  13    illustrates the result of the assembly of an electronic chip  1101  to a substrate  1103 . Chip  1101  may comprise one or a plurality of electronic components, and/or one or a plurality of integrated circuits. According to an example, electronic chip  1101  may be an electronic device adapted to the field of combinational logic, the radio frequency field, such as radars, telephony, “5G” technology, the field of power electronics, the field of electron optics, such as imaging, photonics, etc. 
     In the example illustrated in  FIGS.  13  and  14   , chip  1101  comprises at least two contacts  1105  arranged on the side of substrate  1103 . Substrate  1103  is intended to be removed at the end of the method and has a support function. Substrate  1103  is for example made of a semiconductor material, for example, a material comprising silicon. According to an embodiment, substrate  1103  may be, in top view, a substrate of rectangular shape. 
     A sacrificial layer  1107  is formed between chip  1101  and substrate  1103 . More particularly, layer  1107  rests directly on an upper surface  1109  of substrate  1103 . Layer  1107  enables to ease the removal of substrate  1103  at the end of the method. According to an example, layer  1107  is a polymer sensitive to temperature, to a UV treatment or to a chemical treatment. A “Tape Revalapha” adhesive polymer of trade mark Nitto may be used. 
     A network of interconnection tracks  1111  is formed between chip  1101  and substrate  1103 . More particularly, network  1111  is directly formed on layer  1107 . In  FIG.  13   , network  1111  is represented as a single layer but, in practice, the network is formed of a more or less complex stack of electrically-insulating layers and of electrically-conductive tracks. The conductive tracks are for example metal tracks, such as copper tracks. 
     Connection terminals  1113  are formed on the network of interconnection tracks  1111 . Connection terminals  1113  are for example under bump metallizations (UBM). According to an example, connection terminals  1113  are made of a metal or of a metal alloy, for example, an alloy comprising titanium, gold, titanium, chromium, or nickel. 
     Electronically-conductive links  1115  enable to couple connection terminals  1113  to the contacts  1105  of chip  1101 . Links  1115  are for example solders, or vias. 
     A layer made of a ductile material  1117  is deposited over the entire upper surface of the structure. This layer  1117  allows a very good mechanical hold of the assembly. Ductile material  1117  is similar to the material  709  described in relation with  FIG.  7   , with the difference that material  1117  is, further, electrically insulating. 
     View (b) of  FIG.  13    illustrates a step of thinning of an upper portion of the structure of view (a). More particularly, at this step, the layer of ductile material  1117 , and more precisely an upper surface  1119  of the layer of ductile material  1117 , is etched to reach an upper surface  1121  of electronic chip  1101 . The etch method used at this step depends on the nature of ductile material  1117 . According to an example, the etch method may be a grinding method. 
     View (c) of  FIG.  13    illustrates a step of preparation of a substrate  1200  similar to the preparation of substrate  750  described in relation with  FIG.  8   . Thus, substrate  1200  comprises a cavity  1201  intended to receive a cooling fluid. Cavity  1201  is formed from an upper surface  1203  of substrate  1200 . Substrate  1200  further comprises a filling channel  11205  emerging onto cavity  1201 . According to the example shown in  FIGS.  13  and  14   , cavity  1201  comprises two pillars  1204  of the type of the pillars  651  described in relation with  FIG.  6   . 
     Substrate  1200  further comprises a lateral opening  1206  intended to form a horizontal filling hole of the type of the filling hole described in relation with view (b) of  FIG.  5   . Opening  1206  is coupled to an end of channel  1205 . 
     View (d) of  FIG.  13    illustrates another step of preparation of substrate  1200  where a capillary wick structure  1207  is formed in the bottom  1209  of cavities  1201 . Structure  1207  is similar to the structure  307  described in relation with  FIG.  2   . In parallel, structure  1207  is also formed on surface  1121  of electronic chip  1101 . This is illustrated in view (e). 
     View (e) of  FIG.  13    illustrates a step of assembly of the structure of view (b) and of the substrate  1200  of view (d). Substrate  1200  is flipped, so that the opening of cavity  1201  is in front of the surface  1121  of electronic chip  1101 . This assembly is similar to the bonding step described in relation with view (a) of  FIG.  9   . Thus, adhesive layers may have been previously formed on substrate  1200  and/or on the structure of view (b). According to an example, the assembly method may be a molecular bonding, a polymer bonding, a bonding using sintered glass, a thermocompression bonding, a metal-to-metal bonding, etc. According to an example, the use of a polymer material or a temporary bonding which does not resist temperatures higher than 200° C. can be envisaged. The assembly method may comprises polishing steps, anneals, pressurizations or the creation of vacuum. 
     Cavity  1201  is positioned to be in front of a potential hot spot of chip  1101 . 
     View (f) of  FIG.  13    illustrates the flipping of the structure obtained at Figure (e) and the removal of substrate  1103  and of sacrificial layer  1109 . This removal may be performed, for example, by thermal treatment, by UV treatment, or by chemical treatment. 
     View (g) of  FIG.  14    illustrates the filling of cavities  1201  with a cooling fluid  1150 . Cooling fluid  1150  is similar to the cooling fluid  319  described in relation with  FIG.  2   . The filling method is similar to that described in relation with view (b) of  FIG.  9   , that is, a method comprising the removal of the gases present in cavity  1201  and then the filling of cavity  1201  with cooling fluid  1150 . Fluid  1150  is introduced through filling hole  1206 , and is then directed by channel  1205  into cavity  1201 . Filling hole  1206  is then obstructed with a plug  1211 . 
     View (h) of  FIG.  14    illustrates the tight sealing of filling channel  1205  by crushing of ductile material  1117 . This step is similar to the step of view (d) of  FIG.  9   . Cavity  1201  then forms a vapor chamber associated with chip  1101 . 
     The association of a vapor chamber with a single electronic chip has been shown herein. It is however obvious to those skilled in the art that the method described in relation with  FIGS.  13  and  14    may apply to the manufacturing of a vapor chamber common to a plurality of electronic chips. It is also obvious to those skilled in the art that the method described in relation with  FIGS.  13  and  14    may apply to the manufacturing of a plurality of vapor chambers common to a single electronic chip. 
     Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants may be combined, and other variants will occur to those skilled in the art. 
     In particular, the use of raised areas as described in relation with  FIG.  12    is compatible with the plates of the embodiments described in relation with  FIGS.  10  and  11   . Similarly, raised areas may be envisaged in the method described in relation with  FIGS.  13  and  14   . 
     Finally, the practical implementation of the described embodiments and variations is within the abilities of those skilled in the art based on the functional indications given hereabove.