Patent Publication Number: US-2023163057-A1

Title: Electronic ic device comprising integrated optical and electronic circuit component and fabrication method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of United States Application for patent Ser. No. 17/015,634, filed Sep. 9, 2020, which claims the priority benefit of French Application for Patent No. 1909937, filed on Sep. 10, 2019, the contents of which are hereby incorporated by reference in their entireties to the maximum extent allowable by law. 
    
    
     TECHNICAL FIELD 
     The present invention relates to the field of microelectronics and, more particularly, to the field of the electronic integrated circuit devices or electronic integrated circuit chips which comprise external light-sensitive integrated optical circuit components, forming pixel zones, and integrated electronic circuit component such as transistors generally situated under the optical circuit components. 
     BACKGROUND 
     There is a difficulty in including and making coexist electrical connections, linking the optical circuit components and the electronic circuit component, and a layer made of an electrically-conductive material or ground plane, so as to effectively prevent a coupling capacitance between the optical circuit components and the electronic circuit component. 
     SUMMARY 
     According to one embodiment, an electronic IC device comprises: a first circuit structure comprising light-sensitive optical circuit components; a second circuit structure comprising electronic circuit component and an electrically-conductive layer extending between and at a distance from the optical circuit components and the electronic circuit component; electrical connections configured to link the optical circuit components and the electronic circuit component and formed in holes which pass through dielectric layers and the conductive layer, and electrical insulation rings between the conductive layer and the electrical connections and formed around the electrical connections and in the thickness of the conductive layer. 
     Thus, the conductive layer can extend to close to the electrical connections and the electrical insulation rings can be reduced, so that any coupling capacitance between the optical circuit components and the electronic circuit component can be avoided. 
     The electrical insulation rings can be composed of portions of the conductive layer, rendered dielectric. 
     The conductive layer can be made of doped polysilicon and the electrical insulation rings can be made of oxidized doped polysilicon. 
     The first circuit structure can comprise, in succession, between an outer rear face and a front mounting face, a substrate layer provided on the side of the mounting face with said optical circuit components and a dielectric layer. 
     The second circuit structure can comprise, in succession, from a mounting face attached to the mounting face of the first circuit structure, a first dielectric layer including said conductive layer, a local substrate layer provided with said electronic circuit component and having through-openings and a second dielectric layer comprising parts filling these through-openings. 
      Said electrical connections can be formed in holes which pass through the dielectric layers of the second circuit structure, by passing through the openings of the substrate layer of this second circuit structure and at a distance from the edges of these openings, the conductive layer and the dielectric layer of the first circuit structure, to electrical contacts of the optical circuit components of the first circuit structure. 
     The electronic IC device can comprise electrical connections formed in holes which pass through the second dielectric layer of the second circuit structure, to electrical contacts of the electronic circuit component of the second circuit structure. 
     The electronic IC device can comprise an additional dielectric layer including a network of electrical connections selectively linking said electrical connections and outer electrical contacts formed in a face of the additional dielectric layer opposite said second dielectric layer. 
     The electronic IC device can comprise a third circuit structure attached to the second circuit structure and including electronic circuit component linked to said network of electrical connections. 
     There is also proposed a method for fabricating an electronic IC device, which comprises: fabricating a first circuit structure comprising, in succession, between an outer face and a mounting face, a substrate layer provided on the side of the mounting face with light-sensitive optical circuit components and a dielectric layer; fabricating, separately from the first circuit structure, a part of a second circuit structure comprising, in succession, between a mounting face, a first dielectric layer including an intermediate electrically-conductive layer, and a local substrate layer; assembling the first circuit structure and said part of the second circuit structure by attaching the mounting face of the first circuit structure and the mounting face of the second circuit structure; producing electronic circuit component on the substrate layer of the second circuit structure and through-openings through this substrate layer; producing a second dielectric layer above the substrate layer of the second circuit structure, this second layer filling said openings to the first dielectric layer; producing holes through the dielectric layers of the second circuit structure, by passing through the openings of the substrate layer of this second circuit structure and at a distance from the edges of these openings, the conductive layer and the dielectric layer of the first circuit structure, to electrical contacts of the optical circuit components of the first circuit structure; producing electrical insulation rings by a transformation of portions of the conductive layer, adjacent to the holes, via said holes; and filling said holes with an electrically-conductive material so as to form electrical connections linked to the electrical contacts of the optical circuit components of the first circuit structure. 
     The method can comprise: producing holes through the second dielectric layer of the second circuit structure to electrical contacts of the electronic circuit component; and filling these holes with an electrically-conductive material so as to form electrical connections linked to the electrical contacts of the electronic circuit component of the second circuit structure. 
     The method can comprise: producing, above the second dielectric layer of the second circuit structure, an additional dielectric layer including networks of electrical connections selectively linking said electrical connections and outer electrical contacts of an outer face of the additional dielectric layer. 
     The method can comprise: mounting a third circuit structure above the additional dielectric layer of the second circuit structure, by linking electronic circuit component of this third circuit structure to said networks of electrical connections via said outer electrical contacts. 
     The conductive layer can be made of doped polysilicon and the electrical insulation rings can be obtained by oxidation of the portions of this layer, adjacent to said holes. 
     The oxidation can be obtained by thermal or plasma oxidation. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       An electronic IC device including optical circuit components and electronic circuit component will now be described by way of non-limiting exemplary embodiment, illustrated by the drawings in which: 
         FIG.  1    shows a cross section of an electronic IC device; and 
         FIGS.  2 - 7    show steps of fabrication of the electronic IC device of  FIG.  1   . 
     
    
    
     DETAILED DESCRIPTION 
     According to an embodiment illustrated in  FIG.  1   , an electronic integrated circuit (IC) device  1 , or electronic IC chip, comprises a plurality of adjacent zones of pixels  2 . 
     The electronic IC device  1  comprises a first circuit structure  3  which comprises a substrate layer  4 , made of silicon, which has an outer rear face  5  and a front face  6  opposite this rear face  5 . 
     The front face  6  of the substrate layer  4  is provided, in the zones of pixels  2 , with integrated optical circuit component  7  which are sensitive to the light passing through the rear face  4  so as to deliver electrical signals as a function of the light. 
     The first circuit structure  3  comprises, above the front face  6 , a dielectric encapsulation layer  8 , for example made of silicon oxide, which has a front mounting face  9 . 
     The electronic IC device  1  comprises a second circuit structure  10  which comprises a local substrate layer  11 , for example made of silicon, which has a front face  12  and a rear face  13  on the side of the first circuit structure  3 . 
     Between the rear face  13  of the substrate layer  11  and the mounting face  9  of the first circuit structure  3 , the second circuit structure  10  comprises a dielectric layer  14  above the rear face  13  of the substrate layer  11 , then an intermediate electrically-conductive layer  15 , or ground plane, above the dielectric layer  14 , then a dielectric layer  16  above the conductive layer  14 , this dielectric layer  16  having a rear mounting face  17  attached to the front mounting face  9  of the first circuit structure  3 . 
     The dielectric layers  14  and  16  are, for example, made of silicon oxide and the conductive layer  15 , or ground plane, is, for example, made of doped polysilicon. 
     The front face  12  of the substrate layer  11  is provided, in the zones of pixels  2 , with integrated electronic circuit components  18 , including transistors, formed on local portions of the substrate layer  11 , this substrate layer  11  having openings  19 . 
     The result of the above is that the conductive layer  15  extends between and at a distance from the optical circuit components  7  and the electronic circuit components  18 . 
     The second circuit structure  10  comprises, above the front face  12  of the substrate layer  11 , a dielectric encapsulation layer  20 , for example made of silicon oxide, this dielectric layer  20  filling the openings  19  to the dielectric layer  14  and having a front face  21 . 
     The electronic IC device  1  comprises, in the zones of pixels  2 , a plurality of electrical connections  22  which are formed in holes  23  which extend between the front face  21  of the dielectric layer  20  and front electrical contacts  24  of the electronic circuit component  7  of the first circuit structure  3  and which pass through the dielectric layer  20 , through and at a distance from the flanks of the openings  19  of the substrate layer  11 , the dielectric layer  16 , the conductive layer  15  and the dielectric layer  8 . 
     The electrical connections  22  are electrically insulated from the conductive layer  15  by virtue of electrical insulation rings  25  which surround the electrical connections  22  and which are distinct from the dielectric layers  14  and  16 . The electrical insulation rings  25  are formed in the thickness of the conductive layer  15 . 
     In particular, the electrical insulation rings  25  are composed of reduced local annular portions of the conductive layer  15  surrounding the electrical connections  22 , these local portions being rendered dielectric. 
     For example, where the conductive layer  15  is made of doped polysilicon, the electrical insulation rings  25  are made of oxidized doped polysilicon. 
     The electronic IC device  1  comprises, in the zones of pixels  2 , a plurality of electrical connections  26  which are formed in holes  27  which extend between the front face  21  of the dielectric layer  20  and the front electrical contacts  28  of the electronic circuit components  18  of the second circuit structure  3  and which pass through the dielectric layer  20 . 
     The second circuit structure  10  of the electronic IC device  1  comprises a front dielectric layer  29  above the front face  21  of the dielectric layer  20 . 
     The front dielectric layer  29  includes, in the zones of pixels  2 , networks of electrical connections  30  configured so as to selectively link the electrical connections  22  and  25  and outer front contacts  31  formed in a front face  32  of the front dielectric layer  29 . 
     More particularly, the networks of electrical connections  30  are configured so as to ensure, in the zones of pixels  2 , electrical links between the optical circuit components  7  and the electronic circuit components  18 , which convert the electrical signals from the optical circuit components  7 , and electrical links between the electronic circuit components  18  and the front electrical contacts  31  to deliver the converted electrical signals. 
     Moreover, the conductive layer  15  can be linked to the ground by electrical connections, not represented, formed in holes passing through the dielectric layers  11 ,  14  and  20  and linked to the networks of electrical connections  30 . 
     The electronic IC device further comprises a third circuit structure  33 , not detailed in the figure, which is attached to the front face  33  of the layer  29  of the second circuit structure  10 . 
     This third circuit structure  33  comprises electronic circuit components, notably transistors, which are linked to the electrical contacts  31  and which are capable of processing the electrical signals coming from electronic circuit components  18  of the second circuit structure  10  via the networks of electrical connections  30 . 
     The electronic IC device  1  can be fabricated according to the following steps. 
     As illustrated in  FIG.  2   , on the one hand, there is completed the first circuit structure  3 , the dielectric layer  8  being integral. Advantageously, the substrate layer  4  is thick. 
     On the other hand, there is a completed part  10 A of the second circuit structure  10 , this completed part  10 A comprising the integral substrate layer  20 , not provided with the openings  19  and not provided with the electronic circuit components  18 , the integral dielectric layer  14 , the integral conductive layer  15  and the integral dielectric layer  16 . 
     The adjective “integral” means that the abovementioned layers are not provided with any holes. 
     The first circuit structure  3  is assembled by attaching the mounting face  9  of the dielectric layer  8  and the mounting face  17  of the dielectric layer  16 . 
     After which, as illustrated in  FIG.  3   , the electronic circuit components  18  are produced on the front face  12  of the substrate layer  11 , and the openings  19  are produced through the substrate layer  11 , in that order, or in the other order. 
     After which, as illustrated in  FIG.  4   , the dielectric layer  20  is produced above the substrate layer  11 , this layer  20  filling the openings  19  of the substrate layer  11  to the dielectric layer  14 . 
     After which, as illustrated in  FIG.  5   , the holes  23  and  27  are produced by etching. 
     Then, as illustrated in  FIG.  6   , the portions of the conductive layer  15  adjacent to the holes  23  are transformed into a dielectric material, via the holes  23 . 
     For example, where the conductive layer  15  is made of doped polysilicon, an oxidation gas is introduced into the holes  23  so that, by thermal or plasma oxidation, the annular portions surrounding the holes  23  of the oxidation layer  15  are transformed into dielectric oxidized doped polysilicon and form the electrical insulation rings  25 . 
     After which, as illustrated in  FIG.  7   , the holes  23  and  27  are filled with an electrically-conductive material so as to produce the electrical connections  22  and  26 , this material being, for example, tungsten. 
     According to a variant embodiment, on the one hand the holes  23  and the electrical connections  22  filling them and on the other hand the holes  27  and the electrical connections  26  filling them can be produced according to distinct steps. 
     After which, the dielectric layer  29  provided with the networks of electrical connections  30  is produced. 
     The electronic IC device  1  illustrated in  FIG.  1    is then obtained, without the third circuit structure  33 . 
     After which, the third circuit structure  33  is assembled on the face  32  of the second circuit structure  10 . 
     After which, the back of the substrate layer  4  of the first circuit structure  3  is thinned, so that the light appropriately reaches the optical circuit components  7 . 
     The electronic IC device  1  can be fabricated by implementing the means and the procedures used routinely in the field of microelectronics. 
     As an indication, the thicknesses of the different layers can be as follows. 
     The thickness of the substrate layer  4  can be approximately four micrometers. 
     The thickness of the dielectric layer  8  can be approximately two hundred nanometers. 
     The thickness of the substrate layer  11  can be approximately twenty-five nanometers. 
     The thickness of the dielectric layer  14  can be approximately twenty-five nanometers. 
     The thickness of the conductive layer  15  can be approximately thirty nanometers. 
     The thickness of the dielectric layer  16  can be approximately twenty nanometers. 
     The thickness of the dielectric layer  20  can be approximately three hundred nanometers. 
     The thickness of the dielectric layer  29  including the networks of electrical connections  30  can be approximately three micrometers. 
     The result of the above is that the electronic IC device  1  obtains the following advantages. 
     The conductive layer  15  forming a ground plane, because of its large surface area going as far as short distances from the electrical connections  22 , effectively prevents any capacitive coupling between the optical circuit components  7  and the electronic circuit components  18 . 
     The electrical connections  22  linking the optical circuit components  7  and the electronic circuit components  18  are produced through only the dielectric layers  8 ,  14  and  20  and the conductive layer  15 . 
     The electrical insulation between the conductive layer  15  and the electrical connections  22 , via the electrical insulation rings  25  resulting from a local transformation of the conductive layer  15  into reduced dielectric portions, is produced simply via the holes  23 , before the filling of these holes  13  to obtain the electrical connections  22 .