Patent Publication Number: US-2023133523-A1

Title: METHOD FOR CO-MANUFACTURING A FERROELECTRIC MEMORY AND AN OxRAM RESISTIVE MEMORY AND DEVICE CO-INTEGRATING A FERROELECTRIC MEMORY AND AN OxRAM RESISTIVE MEMORY

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application claims priority to French Patent Application No. 2111616, filed Nov. 2, 2021, the entire content of which is incorporated herein by reference in its entirety. 
     FIELD 
     The present invention relates to the manufacture of memories and more particularly to the co-manufacture of a FeRAM ferroelectric memory and an OxRAM resistive memory, each of both memories having a layer of active material based on hafnium dioxide. The present invention also relates to a device co-integrating an OxRAM memory and a FeRAM memory. 
     BACKGROUND 
     Developments related to artificial intelligence (Al) have long been confined to the software part. However, Al also has many applications in embedded electronics and it is no longer possible to exclusively rely on the cloud for Al-based calculations. The advent of embedded Al, and the need to process algorithms directly in components, raises, more than ever, the question of hardware. The Al will then need to be processed locally, at the very heart of the components. For this, the use of some microelectronic memories is a particularly promising solution. However, Al-based systems are data-intensive and therefore require a large amount of memory on a single chip to store network states and parameters. Moreover, more than the calculations themselves, it is the data transfers between processors and memories that are very energy-intensive. For this reason, there is a tendency to use small and fast memories with the lowest possible energy dissipation during reading and writing. 
     All neural networks used in Al require at least two phases:
         A first so-called learning and training phase which consists in optimising a set of parameters or weights of a model from a data set; this first phase requires a large number of writing operations in the memories which should therefore have a high writing endurance.   A second, so-called inference phase, which consists in suggesting a test data set to the trained model and waiting for a prediction; this case, unlike the previous one, requires a large number of read operations in the memories, which should therefore have very good read endurance.       

     There are different types of memories that can partially meet the above requirements. 
     For example, ferroelectric memories or FeRAM memories have the main qualities of being non-volatile, namely retaining stored information even when the voltage is cut off, of consuming little energy, of having low write and read times with respect to other types of non-volatile memories such as FLASH memories, of being able to be massively integrated on chips with low operating voltages and of having low latency in accessibility and good immunity to radiation. In addition, this type of memory has a very high write endurance of more than 10 10  cycles. 
     Ferroelectric memories are capacitive memories with two remanent polarisation states +Pr and −Pr. [ FIG.  25   ] illustrates the operation of ferroelectric memories. This operation is based on the ferroelectric properties of their active material placed between two electrodes. By applying a potential difference between both electrodes creating an electric field with a value higher than the positive coercive field +Ec, the ferroelectric memory is placed in a high remanent polarisation state +Pr and by applying a potential difference creating an electric field with a value lower than the negative coercive field −Ec, the ferroelectric memory is placed in a low remanent polarisation state −Pr. The high remanent polarisation state +Pr then corresponds to the binary logic state ‘0’ and the low remanent polarisation state −Pr to the binary logic state ‘1’, allowing the information to be stored. Note that when the potential difference is stopped being applied, the remanent polarisation state remains: this explains the non-volatile nature of ferroelectric memories. When reading a ferroelectric memory, it is not known a priori in which polarisation state the memory is. So, for reading, it is assumed that there is a given state and a voltage, for example positive voltage will be applied, beyond the voltage creating an electric field with a value higher than the positive coercive field +Ec: if the memory was already in the state of high remanent polarisation +Pr, this polarisation state will not be changed and no current peak will be observed (or a very small current peak will be observed). Conversely, if the memory was in the low non-volatile bias state −Pr, a much larger current peak will be observed. The consequence of this reading operation is that it is destructive for the polarisation state. It is therefore easy to see that while ferroelectric memories meet the massive writing criterion necessary for the learning and training phase, nevertheless they are not adapted to the inference phase, which requires very good reading endurance. 
     Another type of so-called resistive memory is known, such as OxRAM memories for “Oxide Resistive RAMs”. These memories can have at least two resistive states, corresponding to a High Resistance State (“HRS”) and a Low Resistance State (“LRS”), when a voltage is applied. 
     The main qualities of OxRAM memories are that they are non-volatile, namely they retain stored information even when the voltage is switched off, they have low write and read times with respect to other types of non-volatile memories such as FLASH memories, they can be massively integrated on chips, and they have low latency in accessibility and good immunity to radiation and temperature. They therefore seem to be good candidates for Al applications. However, their write and erase endurance is rather limited (around 10 5  cycles), making them not very efficient during the learning and training phase. 
     OxRAM memories have an M-I-M (Metal-Insulator-Metal) structure comprising an active material with variable electrical resistance, generally a transition metal oxide (e.g. WO 3 , HfO 2 , Ta 2 O 5 , TiO 2 , etc.), disposed between two metal electrodes. The transition from the “HRS” state to the “LRS” state is governed by the formation and breakage of a conductive filament between both electrodes. This conductive filament is created by virtue of the presence of oxygen vacancies in the active layer of the memory. By changing potentials applied to the electrodes, it is possible to change distribution of the filament, and thus change electrical conduction between both electrodes. In the active layer, the electrically conductive filament is either broken or, on the contrary, reformed to vary the resistance level of the memory cell, during write and then reset cycles of this cell (SET operations, when the filament is reformed, leading to the LRS state, and RESET operations, leading to the HRS state, when the filament is broken again by applying a SET, VSET, or RESET, VRESET, voltage to the electrode terminals respectively). The manufacture of a filament memory comprises a so-called “forming” step, in which the filament is formed for the first time in the active layer, which is initially filament-free. The active layer is initially completely electrically insulating. During the initial forming step, an electrically conductive filament is formed in the active layer, by performing a kind of controlled breakdown of this layer. The formed filament then extends through the active layer, electrically connecting the bottom and top electrodes. To carry out this forming step, an electrical voltage can be applied between the lower and top electrodes of the memory cell in question, and then the value of this voltage can be progressively increased up to a threshold voltage, known as the forming voltage V forming , above which breakdown of the active layer is achieved. After this forming step, the memory cell is ready for use. The conductive filament can then be broken, and then reformed, then broken again and so on, at a voltage value lower than the forming voltage V forming . 
     It is understood upon reading the above that neither ferroelectric memories nor OxRAMs fully meet Al-based system requirements due to either read (for FeRAMs) or write (for OxRAMs) limitations. 
     Even if patent application FR3090196 does not explicitly concern Al applications, it describes the co-integration of an OxRAM memory and a FeRAM memory on the same chip, thus making it possible to combine benefits in writing and reading of both memories. This co-integration takes advantage of the fact that the same active material, HfO2, is used for the active layer of the OxRAM and the FeRAM. 
     The manufacturing method described in patent application FR3090196 for achieving this co-integration is, however, complex to implement insofar as it requires a masking level to differentiate doping of the active layer used for FeRAM from that of the active layer used for OxRAM. The method additionally involves the use of sub-microsecond laser annealing for reducing heating time of the doped active material and ensuring adequate crystallisation of the hafnium dioxide into the form providing it with ferroelectric properties without overheating the underlying layers. Further, the electrical efficiency of the OxRAM obtained by this method is not entirely satisfactory. 
     SUMMARY 
     An aspect of the invention provides a solution to the problems previously discussed by making it easier to manufacture a ferroelectric memory co-integrated with an OxRAM resistive memory while preserving efficient properties of FeRAM and OxRAM memories. 
     To this end, an aspect of the invention is especially a method for co-manufacturing a ferroelectric memory including a first electrode, a second electrode and a layer of hafnium dioxide active-based material disposed between the first electrode and the second electrode, and an OxRAM resistive memory including a first electrode, a second electrode and a layer of hafnium dioxide HfO 2 -based active material disposed between the second electrode and the first electrode, the co-manufacturing method including the following steps:
         A step of depositing a layer of first electrode carried out identically for the zone for forming the OxRAM resistive memory and the zone for forming the ferroelectric memory;   A step of depositing a layer of active material based on hafnium dioxide carried out identically for the zone for forming the OxRAM resistive memory and the zone for forming the ferroelectric memory;   A step of depositing a first conductive layer carried out identically for the zone for forming the OxRAM resistive memory and the zone for forming the ferroelectric memory;   A step of forming a mask at the zone of the first conductive layer for forming the ferroelectric memory, leaving the zone of the first conductive layer for forming the OxRAM resistive memory free;   A step of removing the first conductive layer at the zone of the first conductive layer for forming the OxRAM resistive memory, the zone of the first conductive layer for forming the ferroelectric memory being protected by the mask;   A step of removing the mask at the zone of the first conductive layer for forming the ferroelectric memory;   A step of depositing a second conductive layer, said second conductive layer being in contact with the first conductive layer at the zone of the first conductive layer for forming the ferroelectric memory and in contact with the layer of active material at the zone of the first conductive layer for forming the OxRAM resistive memory, the material of the second conductive layer being selected to create oxygen vacancies in the active layer of the OxRAM when the second conductive layer is in contact with the active layer of the OxRAM;   A step of depositing a third conductive layer carried out identically for the zone for forming the OxRAM resistive memory and the zone for forming the ferroelectric memory, said third conductive layer being in contact with the second conductive layer.       

     By virtue of the invention, unlike in the case of patent application FR3090196, there is no need for additional masking to obtain different doping in the respective active layers of the FeRAM memory and OxRAM memory. Surprisingly, the inventors actually realised that an identical active layer for both memories made it possible to obtain both the ferroelectric effect in FeRAM and the resistive memory effect in OxRAM (as opposed to application FR3090196, where the active layer of the OxRAM memory was much more doped than that of the ferroelectric memory). Thus, the doping of the hafnium dioxide active layer, which is necessary for FeRAM, is also sufficient for the resistive operation of OxRAM. The same reasoning applies to an active layer formed by a hafnium dioxide-based alloy, as for example HfZrO 2 : in the case of HfZrO 2 , the ternary alloy HfZrO 2  does not necessarily require doping of the active layer, but the latter is identical for OxRAM and FeRAM. In general, a hafnium dioxide-based layer of active material is understood to be either a doped HfO 2  layer or a hafnium dioxide-based alloy such as HfZrO 2  that is not necessarily doped. 
     To do this, the method according to an aspect of the invention beneficially uses a modification of the top electrode which will be different for OxRAM and for FeRAM. Indeed, according to an embodiment of the method of the invention, the top electrode will be formed respectively:
         By a bilayer formed by the second conductive layer and the third conductive layer for the OxRAM   By a tri-layer formed by the first conductive layer, the second conductive layer and the third conductive layer for the FeRAM.       

     The second conductive layer is in direct contact with the hafnium dioxide-based active layer for the OxRAM and has the feature of being an “Oxygen scavenging layer” type layer, that is a layer to create oxygen vacancies in the hafnium dioxide-based active layer of the OxRAM when this second conductive layer is in contact with the active layer of the OxRAM. For example, this may be a layer of titanium Ti or hafnium Hf. Conversely, the active layer on the FeRAM side is in contact with the first conductive layer, which is not a layer creating oxygen vacancies, for example a TiN layer, on which the second conductive layer is deposited. By doing so, oxygen vacancies are created in the hafnium dioxide-based layer of the OxRAM without creating oxygen vacancies in the hafnium dioxide-based layer of the FeRAM, thereby ensuring efficient resistive operation of the OxRAM, despite the identical doping in the active layers for the OxRAM and FeRAM. 
     In addition, an aspect of the method according to the invention makes it possible to dispense with localised sub-microsecond laser annealing. Indeed, adequate crystallisation of hafnium dioxide in the orthorhombic form providing it with ferroelectric properties is directly achieved via the thermal budget of the various manufacturing steps, particularly in “back end” integration compatible with CMOS technology. Moreover, the fact of using an HfO 2 -based active layer crystallised in its orthorhombic phase is not detrimental to the operation of the OxRAM memory, for which the person skilled in the art usually uses amorphous or monoclinic HfO 2 . 
     In addition to the features just discussed in the preceding paragraph, the method according to an aspect of the invention may have one or several complementary characteristics among the following, considered individually or according to any technically possible combination:
         the step of making the mask at the zone of the first conductive layer for forming the ferroelectric memory while leaving the zone of the first conductive layer for forming the OxRAM resistive memory free includes the following steps:
           A step of depositing a mask on the first conductive layer at the zone of the first conductive layer for forming the ferroelectric memory and the zone of the first conductive layer for forming the OxRAM resistive memory;   A step of removing the mask at the zone of the first conductive layer for forming the OxRAM resistive memory while leaving the mask at the zone of the first conductive layer for forming the ferroelectric memory.   
           The method according to an embodiment of the invention includes, at the end of the step of depositing the hafnium dioxide-based layer of active material, a step of doping the layer of active material carried out identically for the zone for forming the OxRAM resistive memory and the zone for forming the ferroelectric memory   the doping step is carried out by ion implantation or using a doping precursor or by co-sputtering.   the dopant element used for the doping step is selected from one of the following elements: Si, Al, Zr, Gd, Ge, Y or N;   the dopant element is Si (the doping step being in an embodiment carried out by ion implantation and with a layer of active material thickness in the order of 10 nm) and the layer of active material is exposed to a dopant dose of between 10 14  ions/cm 2  and 5.10 14  ions/cm 2 ;   the method according to an embodiment of the invention includes a heat treatment step to crystallise the layer of active material in an orthorhombic phase.       

     Another aspect of the present invention is a device including an OxRAM resistive memory arranged in a first dedicated zone and a ferroelectric memory arranged in a second dedicated zone, 
     the ferroelectric memory including a first electrode, a second electrode and a layer of hafnium dioxide-based active material disposed between the first electrode and the second electrode,
 
the OxRAM resistive memory including a first electrode, a second electrode and a layer of hafnium dioxide-based active material disposed between the first electrode and the second electrode,
 
the bottom electrodes of the ferroelectric and resistive OxRAM memories being formed by the same layer of first electrode present on the first and second dedicated zones, the layers of hafnium dioxide HfO 2 -based active material of the ferroelectric and resistive OxRAM memories being formed by a same layer of hafnium dioxide-based active material present on the first and second dedicated zones,
 
the second electrode of the ferroelectric memory being formed by a tri-layer including, in the second dedicated zone, a first conductive layer in contact with the active layer, a second conductive layer on the first conductive layer and a third conductive layer on the second conductive layer,
 
the second electrode of the OxRAM resistive memory being formed by a bilayer including in the first dedicated zone, the second conductive layer in contact with the active layer and the third conductive layer on the first conductive layer,
 
the material of the second conductive layer being selected to create oxygen vacancies in the active layer of the OxRAM resistive memory when the second conductive layer is in contact with the active layer of the OxRAM.
 
     The device according to an aspect of the invention may especially be obtained by the co-manufacturing method according to the invention. 
     In addition to the characteristics just discussed in the preceding paragraph, the device according to an aspect of the invention may have one or several complementary characteristics from among the following, considered individually or in any technically possible combination:
         the thickness of the active layer and/or the thickness of the second conductive layer is typically between 3 nm and 15 nm.   the thickness of the third conductive layer is typically between 20 nm and 200 nm.   the ferroelectric memory includes a pit having an inner wall on which the layer of first electrode, the hafnium dioxide-based layer of active material, the tri-layer including the first conductive layer, the second conductive layer and the third conductive layer on the second conductive layer are successively arranged.       

     An aspect of the present invention also relates to a method for training and inferring an artificial intelligence system including a device according to the invention, wherein the ferroelectric memory is used in the training phases and the OxRAM resistive memory is used in the inference phases. 
     The invention and its various applications will be better understood upon reading the following description and upon examining the accompanying figures. 
    
    
     
       BRIEF DESCRIPTION OF THE FIGURES 
       The figures are set forth by way of illustrating and in no way limiting purposes of the invention. 
         FIGS.  1  to  10    illustrate the different steps of the method for co-manufacturing a ferroelectric memory and an OxRAM memory according to a first embodiment of the invention. 
         FIG.  11    shows the flowchart of the method steps according to a first embodiment of the invention illustrated in  FIGS.  1  to  10   . 
         FIG.  12    illustrates an alternative embodiment of the method of  FIG.  11   . 
         FIGS.  13  to  23    illustrate the different steps of the method for co-manufacturing a ferroelectric memory and an OxRAM memory according to a second embodiment of the invention. 
         FIG.  24    shows the flowchart of the method steps according to a second embodiment of the invention illustrated in  FIGS.  13  to  23   . 
         FIG.  25    illustrates the operation of ferroelectric memories. 
         FIG.  26    illustrates a ferroelectric memory and an OxRAM memory according to the invention which are co-integrated in backend on a CMOS transistor. 
     
    
    
     DETAILED DESCRIPTION 
     Unless otherwise specified, a same element appearing in different figures has a unique reference. 
     An aspect of the invention relates to a method for co-manufacturing a FeRAM ferroelectric memory and an OxRAM memory, each having hafnium dioxide HfO 2  or a hafnium dioxide-based material as an active material, as for example an HfZrO 2  alloy (in the case of HfZrO 2 , the steps of depositing and doping the active layer with HfO 2  can be considered equivalent to the deposition of the ternary HfZrO 2  alloy). The latter exhibits ferroelectric properties when doped with a particular dopant element in order to obtain a suitable dopant element concentration, and then crystallised in the orthorhombic phase. This material can also be used in resistive memories of the OxRAM type, based on the formation of a conductive filament when the material has oxygen vacancies. 
       FIGS.  1  to  10    illustrate the different steps  101  to  110  (flowchart of [ FIG.  11   ]) of a first embodiment of the co-manufacturing method  100  according to the invention. 
       FIG.  1    illustrates the first step  101  of the method  100  according to an aspect of the invention. 
       FIG.  2    illustrates the second step  102  of the method  100  according to an aspect of the invention. 
       FIG.  3    illustrates the third step  103  of the method  100  according to an aspect of the invention. 
       FIG.  4    illustrates the fourth step  104  of the method  100  according to an aspect of the invention. 
       FIG.  5    illustrates the fifth step  105  of the method  100  according to an aspect of the invention. 
       FIG.  6    illustrates the sixth step  106  of the method  100  according to an aspect of the invention. 
       FIG.  7    illustrates the seventh step  107  of the method  100  according to an aspect of the invention. 
       FIG.  8    illustrates the eighth step  108  of the method  100  according to an aspect of the invention. 
       FIG.  9    illustrates the ninth step  109  of the method  100  according to an aspect of the invention. 
       FIG.  10    illustrates the tenth step  110  of the method  100  according to an aspect of the invention. 
       FIG.  11    shows the flowchart of the steps of the method according to an aspect of the invention illustrated in  FIGS.  1  to  10   . 
     The method  100  according to an aspect of the invention comprises a step  101  of conformally depositing a layer of first electrode  201  represented in  FIG.  1   . This deposition is carried out identically for the zone Z 1  for forming the OxRAM resistive memory and the zone Z 2  for forming the FeRAM ferroelectric memory. In other words, a single layer of first electrode  201  is deposited: the part of the layer of first electrode located in the first zone Z 1  is to be the layer of first electrode  201  of the OxRAM resistive memory while the part of the layer of first electrode located in the second zone Z 2  is to be the layer of first electrode  201  of the FeRAM ferroelectric memory. For the sake illustrative clarity, the layer  201  has been represented in two parts at Z 1  and Z 2 , but it is understood that it is a single layer that is deposited to form both OxRAM and FeRAM memories, wherein insulation can then be achieved between said memories. 
     The layer of first electrode  201  is, for example, disposed on vias  200   a  and  200   b , for example of tungsten, respectively for connecting the OxRAM and FeRAM memories to lower Cu metal levels. The first electrode  201  is referred to as the bottom electrode for both OxRAM and FeRAM. It will be appreciated that the layer of first electrode  201  may also be deposited on a substrate not represented. 
     The conductive material of the layer of first electrode  201  is for example titanium nitride TiN. TiN is a non-limiting example but other conductive materials such as TaN or W could also be used. 
     The deposition is for example a physical vapour deposition or PVD. 
     The thickness of the layer of first electrode  201  is for example between 10 nm and 200 nm. 
     The method  100  according to an aspect of the invention then includes a step  102  of depositing a layer of active material  202  represented in  FIG.  2    consisting in carrying out conformal deposition of hafnium dioxide HfO 2 . In the same way as for the step  101  of depositing the electrode layer  201 , the step of depositing the layer of active material  202  consists in depositing a single layer of active material  202 , the first zone Z 1  of this single layer of active material  202  being intended to be the layer of active material  202  of the OxRAM resistive memory and the second zone Z 2  of the layer of active material  202  being intended to be the layer of active material  202  of the FeRAM ferroelectric memory. 
     The deposition of the layer of active material  202  may be performed directly on the layer of first electrode  201  or on another layer previously deposited on the layer of first electrode  201 . 
     The deposition is, for example, an atomic layer deposition or ALD between 200 and 300° C., which makes it possible to deposit layers of small thicknesses, in this case between 5 and 10 nm. This type of HfO 2  thickness is compatible with an active layer thickness usable both for OxRAM and FeRAM operations. The thickness of the layer of active material  202  is, for example, about 10 nm. 
     The method  100  also includes a step of doping  103  the layer of active material  202 . By “doping a layer», it is meant the action of introducing atoms of another material called impurities into the material of the layer. 
     According to one embodiment represented in  FIG.  3   , the doping step  103  is carried out by ion implantation. Ion implantation doping consists in accelerating ionised impurities with an electric field, in order to provide them with the necessary energy to enter the material to be doped. 
     The dopant element used is in an embodiment silicon Si. However, other dopant elements such as aluminium Al, zirconium Zr, germanium Ge, gadolinium Gd, yttrium Y or nitrogen N could also be used. 
     According to this step  103 , the entire layer  202  (i.e. both on the zone Z 1  dedicated to making the OxRAM and on the zone Z 2  dedicated to making the FeRAM) is doped identically. 
     The layer of active material  202  is, for example, exposed to a dopant dose between 10 14  ions/cm 2  and 5.10 14  ions/cm 2  at an energy between 2 keV and 4 keV. This doping range is compatible not only with the use of the active layer in an OxRAM resistive memory (subject to the creation of oxygen vacancies that will be further discussed below) but also with the use of the active layer in an FeRAM memory in order to obtain an orthorhombic phase with a suitable thermal budget. Contrary to patent application FR3090196, where the active layer of zone Z 1  was over-doped with respect to the active layer of zone Z 2 , the active layer  202  is here doped identically. 
     According to an embodiment not represented, the doping step  103  may also be performed at the same time as the deposition of the active layer using a doping precursor. For example, the doping precursor is used during ALD deposition by alternating cycles of depositing hafnium dioxide HfO 2  and dopant elements and the number of cycles (i.e. referred to as ALD super-cycles). The doping precursor is for example silicon dioxide SiO 2 . 
     According to another embodiment not represented, doping can also be carried out at the same time as the active layer by co-sputtering via a PVD (Phase Vapour Deposition) or via a PLD (Pulse Laser Deposition). 
     At the end of the doping step  103  represented in step  104  of  FIG.  4   , the layer of active material  202  has become a layer of HfO 2  active material  203 , doped for example with Si. 
     The method  100  according to an aspect of the invention then includes a step  105  ( FIG.  5   ) of depositing a first conductive layer  204  on the doped layer of HfO 2  active material  203 . This deposition is carried out identically for the zone Z 1  for forming the resistive OxRAM and the zone Z 2  for forming the FeRAM ferroelectric memory. 
     The conductive material of the first conductive layer  204  is for example titanium nitride TiN. TiN is a non-limiting example but other conductive materials such as TaN or W could also be used. 
     The deposition is for example a physical vapour deposition or PVD. 
     The thickness of the first conductive layer  204  is in the order of 10 nm or more. 
     The method according to an aspect of the invention then includes a step  106  of making a mask  205  at the zone Z 2  of the first conductive layer  204  for forming the ferroelectric memory, leaving the zone Z 1  of the first conductive layer  204  for forming the OxRAM resistive memory free. The mask  205  is for example made of silicon nitride SiN, silicon oxide SiO 2  or resin. The mask  205  thus covers the part of the first conductive layer  204  located in the zone Z 2 . In a known way, the mask  205  can be made, for example, by:
         conformally depositing a hard mask covering the first conductive layer both in the zone Z 1  and in the zone Z 2 ;   removing the portion of the hard mask at zone Z 1  while stopping on the first conductive layer  204 . The removal step is for example performed by lithography and etching.       

     Thus, at the end of step  106 , only the zone Z 1  of the first conductive layer  204  is directly accessible on the surface. 
     The method  100  includes a step  107  of removing the first conductive layer  204  at the zone Z 1  of the first conductive layer for forming the OxRAM resistive memory, the zone Z 2  of the first conductive layer  204  for forming the ferroelectric memory being protected by the mask  205 . This removal operation is performed, for example, by plasma etching the first conductive layer  204 , for example of TiN, plasma etching of TiN being highly selective towards the HfO 2  material of the active layer  203  so that etching stops on the HfO 2  active layer  203  in the zone Z 1 . 
     The method  100  then includes a step  108  of removing the mask  205  at the zone Z 2  for forming the ferroelectric memory with a stopping on the first conductive layer  204 . At the end of this step  108 , the active layer  203  is bare in the zone Z 1  and covered with the first conductive layer  204  in the zone Z 2 . The operation of removing the mask  205  is carried out, for example, by means of an oxygen plasma (“oxygen stripping”) in the case where the mask  205  is made of resin. 
     The method  100  then includes a step  109  of conformally depositing a second conductive layer  206 , said second conductive layer  206  being in contact with the first conductive layer  204  at the zone Z 2  for forming the ferroelectric memory and in contact with the layer  203  of active material at the zone Z 1  for forming the OxRAM resistive memory, and then conformally depositing a third conductive layer  207  carried out identically for the zone Z 1  for forming the OxRAM resistive memory and the zone Z 2  for forming the ferroelectric memory, said third conductive layer  207  being in contact with the second conductive layer  206 . 
     The deposition of the layers  206  and  207  is for example a physical vapour deposition or PVD. 
     The conductive material of the third conductive layer  207  is for example titanium nitride TiN. TiN is a non-limiting example but other conductive materials, such as TaN, could also be used. It should be noted that the material chosen for the third conductive layer  207  may be different from the material chosen for the first conductive layer  204 . 
     The thickness of the third conductive layer  207  is, for example, between 20 nm and 200 nm. 
     The conductive material of the second conductive layer  206  is chosen to be a material adapted to pump oxygen (“oxygen scavenging layer”) present in the active layer  203  located in the zone Z 1  on which the second conductive layer  206  is deposited. By pumping oxygen into the active layer  206 , the second conductive layer  206  will create oxygen vacancies in the part of the active layer  203  dedicated to making the OxRAM, the oxygen vacancies being necessary for the proper operation of the OxRAM. Since the second conductive layer  206 , on the other hand, is deposited on the first conductive layer  204  in the zone Z 2  dedicated to FeRAM, it is therefore not in contact with the active layer  203  in the zone Z 2  and will therefore not create any vacancies in the active layer  203  on the Z 2  side. The material of the second conductive layer  206  is, for example, titanium Ti or Hafnium when the material of the third conductive layer  207  is TiN. It may also be Tantalum Ta Hafnium when the material of the third conductive layer  207  is TaN. It should be noted that Ti (respectively Ta) is a good bonding material for the TiN (respectively TaN) upper layer. 
     The thickness of the second conductive layer  206  is substantially identical to the thickness of the active layer  203 , for example between 5 nm and 10 nm. 
     According to step  110  of the method  100  illustrated in  FIG.  10   , two upper vias  208   a  and  208   b  are made on the third conductive layer  207 , respectively at the zone Z 1  dedicated to OxRAM and at the zone Z 2  dedicated to FeRAM. 
       FIG.  12    illustrates one alternative  111  of the method  100  according to an aspect of the invention. Thus, between step  108  and step  109 , it is possible to remove a part (referenced here as  203   a ) of the thickness of the active layer at the zone Z 1  dedicated to OxRAM and a part (referenced here as  204   a ) of the thickness of the first conductive layer at the zone Z 2  dedicated to FeRAM. This step  111  takes place before depositing the second and third conductive layers. This removal can be carried out, for example, by argon plasma, which makes it possible to remove a few nanometres of the upper layers in a uniform and controlled manner, regardless of their chemical nature (“preclean” type plasma). It allows both removal of native oxide on the first conductive layer (e.g. TiN) and decrease in the thickness of the active material on the OxRAM side (thus allowing, in particular, a reduction in the forming and writing voltages of the OxRAM). 
     The material of the active layer  203  has to be crystallised in an orthorhombic phase in order to allow the latter to operate as a ferroelectric memory in the zone Z 2 . To do this, several solutions are contemplatable. The first may consist in annealing at a temperature adapted to the backend process, between 300° C. and 500° C., for example in the order of 450° C.: this annealing may, for example, take place in step  105  (before or, in an embodiment, after the deposition of the first conductive layer  204 ). However, this annealing can be dispensed with by using the cumulative thermal budget in the order of 300° C. of the manufacturing method of  FIG.  11   , to which the end of the manufacturing method not represented here is added and including, especially, the encapsulation of the OxRAM and FeRAM memory points by spacers or by a continuous layer of insulator after backend integration of the memory points above the CMOS transistors. In general, heat treatment of the active layer  203  is therefore performed in order to crystallise it in its orthorhombic phase, this heat treatment being either an annealing (for example carried out after the deposition of the first conductive layer  204 ) or a heat treatment ensuring orthorhombic crystallisation without necessarily a specific annealing, via the steps leading to the encapsulation of the OxRAM and FeRAM memories. An example of the encapsulation of the CMOS transistor levels and the OxRAM and FeRAM memory levels integrated in backend and encapsulated in an oxide layer is illustrated in [ FIG.  26   ]. 
     At the end of the method  100  according to an embodiment of the invention, a device co-integrating a ferroelectric memory arranged in the dedicated zone Z 2  and an OxRAM memory arranged in the dedicated zone Z 1  is thus obtained. The ferroelectric memory includes a first electrode (known as the bottom electrode), a second electrode (known as the top electrode) and a layer of hafnium dioxide HfO 2  active material disposed between the first electrode and the second electrode. Similarly, the OxRAM resistive memory includes a first electrode (known as the bottom electrode), a second electrode (known as the top electrode) and a layer of hafnium dioxide HfO 2  active material disposed between the first electrode and the second electrode. The bottom electrodes of the FeRAM and OxRAM memories are formed by the same layer of first electrode  201 . The layers of hafnium dioxide HfO 2  active materials of the FeRAM and OxRAM memories are formed by the same doped layer of HfO 2  active material  203  crystallised in its orthorhombic phase. 
     The top electrode of the FeRAM is formed by a tri-layer including in its dedicated zone Z 2 , the first conductive layer  204 , the second conductive layer  206  and the third conductive layer  207 . 
     The top electrode of the OxRAM is formed by a bilayer including in its dedicated zone Z 1 , the second conductive layer  206  and the third conductive layer  207 . 
     When the device according to an embodiment of the invention is in its original state, just after its manufacture, the switching zone (i.e. the active layer) of the OxRAM memory has to be formed for the first time by applying a forming voltage Vforming greater than its writing voltage Vset between both electrodes of the OxRAM memory. Thereafter, the OxRAM enters a normal operating mode in which the write voltage Vset and the erase voltage Vreset (opposite in sign to the write voltage) are used to switch the resistance state of the OxRAM resistive memory. 
     By applying a Pup programming voltage across the electrodes of the FeRAM memory greater than the voltage creating an electric field of a value greater than the positive coercive field +Ec, the ferroelectric memory will be placed in a high remanent polarisation state +Pr. Similarly, by applying a Pdown voltage greater than the electric field-creating voltage greater than the negative coercive field −Ec across the FeRAM memory, the FeRAM will be placed in a low remanent polarisation state −Pr. 
       FIGS.  13  to  23    illustrate the different steps  101 ′ to  111 ′ (flowchart of  FIG.  23   ) of a second embodiment of the co-manufacturing method  100 ′ according to the invention. 
       FIG.  13    illustrates the first step  101 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  14    illustrates the second step  102 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  15    illustrates the third step  103 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  16    illustrates the fourth step  104 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  17    illustrates the fifth step  105 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  18    illustrates the sixth step  106 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  19    illustrates the seventh step  107 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  20    illustrates the eighth step  108 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  21    illustrates the ninth step  109 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  22    illustrates the tenth step  110 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  23    illustrates the eleventh step  111 ′ of the method  100 ′ according to an aspect of the invention. 
       FIG.  24    shows the flowchart of the steps of the method  100 ′ according to an aspect of the invention illustrated in  FIGS.  13  to  23   . 
     The method  100 ′ according to the second embodiment of the invention is very similar to the method  100  previously illustrated with the difference that it aims at obtaining a three-dimensional architecture for the cointegrated OxRAM and ferroelectric memories. The interest of such a configuration is to be able to increase, in particular in the case of very advanced nodes, the surface area of the capacitance of the FeRAM. 
     The method  100 ′ according to an aspect of the invention comprises a step  101 ′ of conformally depositing a layer of first electrode  201 ′ represented in  FIG.  13   . This deposition is carried out identically for the zone Z 1  for forming the OxRAM resistive memory and the zone Z 2  for forming the FeRAM ferroelectric memory. In other words, a single layer of first electrode  201 ′ is deposited: the part of the layer of first electrode  201 ′ located in the first zone Z 1  is to be the layer of first electrode  201 ′ of the OxRAM resistive memory while the part of the layer of first electrode located in the second zone Z 2  is to be the layer of first electrode  201 ′ of the FeRAM ferroelectric memory. For the sake illustrative clarity, the  201 ′ layer has been represented in two parts on the zones Z 1  and Z 2 , but it is understood that it is indeed a single layer that is deposited to form both memories OxRAM and FeRAM, and an insulation can then be achieved between said memories. 
     In contrast to the first embodiment, the layer of first electrode  201 ′ is deposited, for example, in a pit  300  in the zone Z 1  and a pit  301  in the zone Z 2 , both pits  300  and  301  being disposed, for example, above vias  200   a ′ and  200   b ′, for example made of tungsten, respectively to connect the OxRAM and FeRAM memories to lower metal levels of Cu. The first electrode  201 ′ is referred to as the bottom electrode for both OxRAM and FeRAM. The pits  300  and  301  could be replaced by conductive vias in which the layer of first electrode  201 ′ would be deposited. The pits  300  and  301  are for example made of a TEOS-type oxide. After deposition of the TEOS, or of an oxide/SiN bilayer, a lithography and then an etching is, for example, carried out in order to etch by forming the pits up to the vias  200   a ′ and  200   b ′, and then the resin is removed by means of an oxygen plasma. 
     The conductive material of the layer of first electrode  201 ′ is for example titanium nitride TiN. 
     The deposition of the layer of first electrode  201 ′ is, for example, an atomic layer deposition or ALD as conformal as possible so that the layer  201 ′ snugly fits the respective internal wall of the pits  300  and  301 . 
     The thickness of the layer of first electrode  201 ′ is for example between 10 nm and 200 nm. 
     The method  100 ′ according to an aspect of the invention then includes a step  102 ′ of depositing a layer of active material  202 ′ represented in  FIG.  14   , consisting in carrying out conformal deposition of hafnium dioxide HfO 2 . In the same way as for the step  101 ′ of depositing the electrode layer  201 ′, the step of depositing the layer of active material  202 ′ consists in depositing a single layer of active material  202 ′, the first zone Z 1  of this single layer of active material  202 ′ being intended to be the layer of active material  202 ′ of the OxRAM resistive memory and the second zone Z 2  of the layer of active material  202 ′ being intended to be the layer of active material  202 ′ of the FeRAM ferroelectric memory. 
     The deposition is, for example, a very conformal deposition of atomic thin films or ALD (Atomic Layer Deposition) between 200 and 300° C., which makes it possible to deposit layers of small thicknesses, here for example between 5 and 10 nm. This type of HfO 2  thickness is compatible with an active layer thickness that can be used for both OxRAM and FeRAM operation. The thickness of the layer of active material  202 ′ is for example about 10 nm. It is understood that the use of pits gives a three-dimensional shape to the memories for increasing the surface area of active material, and thus the useful capacitive surface area of the ferroelectric memory. 
     The method  100 ′ also includes a step  103 ′ of doping the layer of active material  202 ′. 
     According to one embodiment represented in  FIG.  15   , the doping step  103 ′ is performed by plasma immersion ion implantation, so as to have a doping as conformal as possible. 
     The dopant element used is in an embodiment silicon Si. However, other dopant elements such as aluminium Al, zirconium Zr, germanium Ge, gadolinium Gd, yttrium Y or nitrogen N could also be used. 
     According to this step  103 ′, the entire layer  202 ′ (i.e. both on the zone Z 1  dedicated to making the OxRAM and on the zone Z 2  dedicated to making the FeRAM) is doped identically. The layer of active material  202 ′ is for example exposed to a dopant dose between 10 14  ions/cm 2  and 5.10 14  ions/cm 2  at an energy between 2 keV and 4 keV, in the case of Si doping. 
     As for the first embodiment, the doping step  103 ′ may also be performed at the same time as the deposition of the active layer using a doping precursor. For example, the doping precursor is used during the ALD deposition by alternating the cycles of depositing hafnium dioxide HfO 2  and dopant elements and the number of cycles (i.e. referred to as ALD super-cycles). The doping precursor is for example silicon dioxide SiO 2 . Doping can also be carried out at the same time as the active layer by co-sputtering via PVD (Phase Vapour Deposition) or PLD (Pulse Laser Deposition). 
     At the end of the doping step  103 ′ represented in step  104 ′ of  FIG.  16   , the layer of active material  202 ′ has become a layer of HfO 2  active material  203 ′, doped for example with Si. 
     The method  100 ′ according to an aspect of the invention then includes a step  105 ′ ( FIG.  17   ) of conformally depositing a first conductive layer  204 ′ on the doped layer of HfO 2  active material  203 ′. This deposition is carried out identically for the zone Z 1  for forming the OxRAM resistive memory and the zone Z 2  for forming the FeRAM ferroelectric memory. 
     The conductive material of the first conductive layer  204  is for example titanium nitride TiN. TiN is a non-limiting example but other conductive materials such as TaN or W could also be used. 
     The deposition is, for example, Physical Vapour Deposition (PVD) or Atomic Layer Deposition (ALD). 
     The thickness of the first conductive layer  204 ′ is in the order of 10 nm or more. 
     The method  100 ′ according to an aspect of the invention then includes a step  106 ′ of making a mask  205 ′ at the zone Z 2  of the first conductive layer  204 ′ for forming the ferroelectric memory, leaving the zone Z 1  of the first conductive layer  204 ′ for forming the OxRAM resistive memory free. The mask  205 ′ is for example made of silicon nitride SiN, silicon oxide SiO 2  or resin. The mask  205 ′ thus covers the part of the first conductive layer  204 ′ located in the zone Z 2 . In a known way, the mask  205 ′ can be made, for example, by:
         depositing a hard mask covering the first conductive layer both in the zone Z 1  and in the zone Z 2 ;   removing the part of the hard mask at the zone Z 1  with stopping on the first conductive layer  204 ′. The removal step is for example performed by lithography and etching.
 
For the sake of illustration, the mask  205 ′ is shown suspended above the pit  301  but it is not necessarily intended to show a hard mask suspended above the pit. If the mask is of resin (spin-off deposited), the resin will fill the pit, which does not alter the method described.
       

     Thus, at the end of step  106 ′, only the zone Z 1  of the first conductive layer  204 ′ is directly accessible on the surface. 
     The method  100 ′ includes a step  107 ′ of removing the first conductive layer  204 ′ at the zone Z 1  of the first conductive layer for forming the OxRAM resistive memory, the zone Z 2  of the first conductive layer  204 ′ for forming the ferroelectric memory being protected by the mask  205 ′. This removal operation is carried out, for example, by plasma etching the first conductive layer  204 ′, for example of TiN, the plasma etching of TiN being highly selective towards the HfO 2  material of the active layer  203 ′ so that the etching stops on the active layer  203 ′ of HfO 2  in the zone Z 1 . 
     The method  100 ′ then includes a step  108 ′ of removing the mask  205 ′ at the zone Z 2  for forming the ferroelectric memory with stopping on the first conductive layer  204 ′. At the end of this step  108 ′, the active layer  203 ′ is bare in the zone Z 1  and covered with the first conductive layer  204 ′ in the zone Z 2 . The operation of removing the mask  205 ′ is carried out, for example, using an oxygen plasma (“oxygen stripping”). 
     The method  100 ′ then includes a step  109 ′ of conformally depositing a second conductive layer  206 ′, said second conductive layer  206 ′ being in contact with the first conductive layer  204 ′ at the zone Z 2  for forming the ferroelectric memory and in contact with the layer  203 ′ of active material at the zone Z 1  for forming the OxRAM resistive memory. Step  109 ′ also includes non-conformally depositing a third conductive layer  207 ′ carried out identically for the zone Z 1  for forming the OxRAM resistive memory and the zone Z 2  for forming the ferroelectric memory, said third conductive layer  207 ′ being in contact with the second conductive layer  206 . The deposition of the third conductive layer  207 ′ is non-conformal so as to fill the respective not yet filled, parts of the pits  300  and  301 . 
     The deposition of the layers  206 ′ and  207 ′ is for example a physical vapour deposition or PVD. The deposition will be either chosen conformal or non-conformal, depending on the diameter of the pit. If the diameter of the pit is typically less than 100 nm, a conformal deposit will be favoured. 
     The conductive material of the third conductive layer  207 ′ is for example titanium nitride TiN. TiN is a non-limiting example but other conductive materials such as TaN could also be used. It will be noted that the material chosen for the third conductive layer  207 ′ may be different from the material chosen for the first conductive layer  204 ′. 
     The thickness of the third conductive layer  207 ′ should be such that the pits  300  and  301 ′ are completely filled. 
     The conductive material of the second conductive layer  206 ′ is chosen to be a material adapted to pump oxygen (“oxygen scavenging layer”) present in the active layer  203 ′ located in the zone Z 1  on which the second conductive layer  206 ′ is deposited. By pumping oxygen into the active layer  206 ′, the second conductive layer  206 ′ will create oxygen vacancies in the part of the active layer  203 ′ dedicated to making the OxRAM, the oxygen vacancies being necessary for the proper operation of the OxRAM. Since the second conductive layer  206 ′, on the other hand, is deposited on the first conductive layer  204 ′ in the zone Z 2  dedicated to FeRAM, it is therefore not in contact with the active layer  203 ′ in the zone Z 2  and will therefore not create any vacancies in the active layer  203 ′ on the Z 2  side. The material of the second conductive layer  206 ′ is, for example, Ti or Hafnium when the material of the third conductive layer  207 ′ is TiN. It may also be Tantalum Ta Hafnium when the material of the third conductive layer  207 ′ is TaN. It will be noted that Ti (respectively Ta) is a good bonding material for the TiN (respectively TaN) upper layer. 
     The thickness of the second conductive layer  206 ′ is substantially identical to the thickness of the active layer  203 ′, for example between 5 nm and 10 nm. 
     According to step  110 ′ of the method  100 ′ illustrated in  FIG.  22   , a removal by controlled chemical mechanical polishing (CMP) of all the layers  207 ′,  206 ′,  203 ′,  201 ′ is carried out with stopping on the upper surface of the pits  300  and  301 . 
     According to step  111  of the method  100  illustrated in  FIG.  10   , two upper vias  208   a ′ and  208   b ′ are made on the third conductive layer  207 ′, respectively at the level of the zone Z 1  dedicated to the OxRAM and at the level of the zone Z 2  dedicated to the FeRAM. 
     At the end of the method  100 ′ according to an embodiment of the invention, a device co-integrating a ferroelectric memory arranged in the dedicated zone Z 2  and an OxRAM memory arranged in the dedicated zone Z 1  is thus obtained. The ferroelectric memory is arranged in three dimensions within a pit  301  in which the internal wall is successively covered with a first electrode (called bottom electrode), a layer of hafnium dioxide HfO 2  active material and a second electrode (called top electrode). Similarly, the OxRAM memory is arranged in three dimension within a pit  300  in which the internal wall is successively covered with a first electrode (referred to as the bottom electrode), a layer of hafnium dioxide HfO 2  active material and a second electrode (referred to as the top electrode). The bottom electrodes of FeRAM and OxRAM memories are formed by the same layer of first electrode  201 ′. The layers of hafnium dioxide HfO 2  active material of the FeRAM and OxRAM memories are formed by the same layer of doped HfO 2  active material  203 ′ crystallised in its orthorhombic phase. 
     The top electrode of the FeRAM is formed by a tri-layer successively including the first conductive layer  204 ′, the second conductive layer  206 ′ and the third conductive layer  207 ′ in the pit  301 . 
     The top electrode of the OxRAM is formed by a bilayer successively including the second conductive layer  206 ′ and the third conductive layer  207 ′ in the pit  300 . 
     According to an alternative of the method  100 ′ according to the second embodiment of the invention, between step  108 ′ and step  109 ′, it is possible to remove part of the thickness of the active layer at the zone Z 1  dedicated to the OxRAM and part of the thickness of the first conductive layer at the zone Z 2  dedicated to the FeRAM. This step takes place before the deposition of the second and third conductive layers. 
     As previously in the case of the method  100  according to a first embodiment, the material of the active layer  203 ′ should be crystallised in an orthorhombic phase for operating it as a ferroelectric memory in the zone Z 2 . 
     The operation in forming, writing and reading the memories is identical to that previously described. 
     According to a third embodiment of the method according to the invention, it is possible to make a two-dimensional OxRAM resistive memory as described with reference to the method  100  according to the first embodiment and a three-dimensional ferroelectric memory (i.e. in a pit in order to increase the capacitive surface area) as described with reference to the method  100 ′ according to the second embodiment of the invention.