METHOD OF FORMING OF A SEMI-TRANSPARENT DEVICE INTEGRATING A CAPACITOR STRUCTURE

Abstract

A method for producing an at least partially transparent device is provided, including producing, on a first substrate, first and second separation layers one against the other; producing, on the second separation layer, an at least partially transparent functional layer; making the functional layer integral with a second at least partially transparent substrate; forming a mechanical separation at an interface between the separation layers; removing the second separation layer; producing a first at least partially transparent electrode layer on the functional layer; where the materials of the stack are chosen such that the interface between the separation layers corresponds to that, among all the interfaces of the stack, having the lowest adherence force.

Claims

1.-13. (canceled)

14. A method for producing an at least partially transparent device, comprising: producing, on one face of a first substrate, first and second separation layers arranged one against the other and such that the first separation layer is arranged between the first substrate and the second separation layer; producing, on the second separation layer, at least one at least partially transparent functional layer; making the functional layer integral with a second at least partially transparent substrate, forming a stack of different materials; forming a mechanical separation at an interface between the first and the second separation layers, such that the first separation layer remains integral with the first substrate and that the second separation layer remains integral with the functional layer; removing the second separation layer; producing at least one first at least partially transparent electrode layer on the functional layer, wherein materials of the stack are chosen such that the interface between the first and the second separation layers corresponds to that having a lowest adherence force among all interfaces of the stack, wherein one of the first and the second separation layers comprises at least SiO.sub.2 and/or silicon nitride, and the other of the first and the second separation layers comprises at least one noble metal; and/or between the step of producing the first and the second separation layers and the step of making the functional layer integral, implementing at least one step of reducing an initial adherence force of the interface between the first and the second separation layers.

15. The method according to claim 14, wherein the noble metal comprises platinum.

16. The method according to claim 14, wherein the step of making the functional layer integral is implemented: through at least one at least partially transparent adhesive layer produced on the functional layer and/or on the second substrate, or by direct bonding between a first at least partially transparent bonding layer produced on the functional layer, and a second at least partially transparent bonding layer produced on the second substrate.

17. The method according to claim 16, wherein: the adhesive layer comprises a polymer glue, or the first and the second bonding layers comprise SiO.sub.2.

18. The method according to claim 14, wherein the functional layer comprises at least one pyroelectric material and/or piezoelectric material and/or ferroelectric material and/or dielectric material.

19. The method according to claim 18, wherein: the pyroelectric material and/or the piezoelectric material and/or the ferroelectric material and/or the dielectric material comprises lead, the one of the first and the second separation layers comprises SiO.sub.2, and the at least one step of reducing the initial adherence force of the interface between the first and the second separation layers comprises implementing at least one thermal treatment forming, at the interface between the first and the second separation layers, an alloy of lead and SiO.sub.2 in a liquid phase, then a cooling forming cavities at the interface between the first and the second separation layers.

20. The method according to claim 14, wherein: the first separation layer comprises the noble metal, the second separation layer comprises SiO.sub.2 and/or silicon nitride, and the functional layer comprises AlN, or the first separation layer comprises SiO.sub.2 and/or silicon nitride, the second separation layer comprises the noble metal, and the functional layer comprises PZT.

21. The method according to claim 14, further comprising, between the step of producing the functional layer and the step of making the functional layer integral with the second substrate, producing at least one second at least partially transparent electrode layer on the functional layer, and wherein, during the step of making the functional layer integral with the second substrate, the second electrode layer is arranged between the second substrate and the functional layer.

22. The method according to claim 14, further comprising, after the step of producing the first electrode layer, etching the first electrode layer according to an interdigitated comb pattern and forming the electrodes of the device.

23. The method according to claim 14, further comprising, after the step of making the functional layer integral with the second substrate, producing at least one cavity in the second substrate, through a face opposite to that on which the functional layer is made integral.

24. The method according to claim 14, wherein the second substrate comprises at least one polymer material, and wherein the step of making the functional layer integral with the second substrate is implemented at a temperature less than or equal to around 150 C.

25. An at least partially transparent device, comprising: an at least partially transparent substrate; first and second at least partially transparent electrode layers arranged on a side of a first face of the substrate and each including at least one electrically conductive material; an at least partially transparent functional layer, arranged between and in direct contact with the first and the second electrode layers; and at least one cavity crossing at least one part of the substrate from a second face of the substrate opposite to the first face.

26. The at least partially transparent device according to claim 25, wherein: the substrate comprises glass and/or at least one polymer material, and/or the first and the second electrode layers comprise ITO and/or ZnO doped with Ga and/or ZnO doped with Al, and/or the functional layer comprises at least one of the following materials: PZT, PMN-PT, KNN, NBT-BT, BaTiO.sub.3.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0065] The present invention will be better understood on reading the description of exemplary embodiments given for only illustrative purposes and in no way limiting while referring to the appended drawings in which:

[0066] FIGS. 1A to 1D show the steps of a method for producing an at least partially transparent device according to a first embodiment;

[0067] FIG. 2 shows an at least partially transparent device obtained by the implementation of a production method according to an alternative of the first embodiment;

[0068] FIGS. 3A to 3D show the steps of a method for producing an at least partially transparent device according to a second embodiment;

[0069] FIG. 4 shows an at least partially transparent device obtained by the implementation of a production method according to an alternative of the second embodiment.

[0070] Identical, similar or equivalent parts of the different figures described hereafter bear the same numerical references so as to make it easier to go from one figure to the next.

[0071] The different parts shown in the figures are not necessarily according to a uniform scale, in order to make the figures more legible.

[0072] The different possibilities (alternatives and embodiments) should be understood as not being mutually exclusive and may be combined together.

Detailed Description of Particular Embodiments

[0073] Reference is firstly made to FIGS. 1A to 1D which show the steps of a method for producing an at least partially transparent device 100 according to a first embodiment.

[0074] As shown in FIG. 1A, a first substrate 102, also called donor substrate, is used to produce at least one part of the layers of the device 100. The first substrate 102 here corresponds to a semiconductor substrate, including for example silicon, and of which the thickness is for example between around 100 m and 1 mm.

[0075] A low adherence force interface is firstly formed on the first substrate 102. In this first embodiment, this interface is formed thanks to a first separation layer 104 here including at least one noble metal and a second separation layer 106 including at least SiO.sub.2 and/or silicon nitride such as SiN and/or Si.sub.3N.sub.4. The low adherence force interface corresponds to the interface between these two separation layers 104, 106, and is obtained thanks to the nature of the materials of the separation layers 104, 106 which only adhere weakly to each other.

[0076] The noble metal of the first separation layer 104 comprises at least one of the following elements: platinum, gold, silver, rhodium, osmium, palladium, ruthenium, iridium. The thickness of the first separation layer 104 is for example between around 1 nm and 200 nm. The material of the second separation layer 106 may advantageously correspond to SiO.sub.2. The thickness of the second separation layer 106 is for example between around 1 nm and 20 m. The first separation layer 104 that comprises the noble metal may be formed by deposition, for example by PVD (physical vapour deposition). The second separation layer 106 which comprises SiO.sub.2 and/or silicon nitride may also be formed by PVD.

[0077] An at least partially transparent functional layer 108 is produced, for example by cathodic sputtering, on the second separation layer 106. In the first embodiment described here, the device 100 corresponds to an at least partially transparent piezoelectric transducing device, and the layer 108 thus comprises an at least partially transparent piezoelectric material, such as for example AlN, optionally doped (for example with Sc) to optimise the piezoelectric properties thereof, or ZnO. The thickness of the layer 108 is for example between around 1 nm and 100 m. Moreover, due to the fact that the material of the layer 108 is formed on the second separation layer 106, this material of the layer 108 has an optimal texturing which will result in fine in good transducing performances of the device 100.

[0078] In an alternative, the layer 108 may comprise PZT or a material of the same family as PZT, which can also be doped for example by La, Nb, Mn, etc., or instead PMN-PT ((1-x)Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3-xPbTiO.sub.3), KNN ((K,Na)NbO.sub.3), NBT-BT ((Na.sub.0.5Bi.sub.0.5)TiO.sub.3BaTiO.sub.3), BaTiO.sub.3, or any other at least partially transparent transducing material. The material of the layer 108 is for example deposited by sol-gel process or by cathodic sputtering. In this case, the first separation layer 104 preferably comprises SiO.sub.2 and/or silicon nitride, and the second separation layer 106 preferably comprises the noble metal in order that the transducing material is formed on the noble metal, conferring an optimal texture (preferential crystallographic orientation) on the transducing material.

[0079] An at least partially transparent electrode layer 110 is formed, for example by deposition, on the layer 108. This electrode layer 110 is intended to form one of the electrodes of the device 100. This layer 110 comprises an electrically conductive material, for example a metal oxide, and at least partially transparent, such as for example ITO (indium tin oxide), ZNO doped with Ga (also called GZO), or ZNO doped with Al (also called AZO) or any other at least partially transparent conductive material such as for example a very thin metal (thickness for example between around 1 nm and 10 nm). The thickness of the layer 110 is for example between around 1 nm and 200 nm.

[0080] A first bonding layer 112 is next produced, for example by deposition, on the electrode layer 110. This first bonding layer 112 is intended to serve for the implementation of a direct bonding, or molecular bonding, with a second bonding layer enabling the transfer of the layers 108 and 110 onto a second at least partially transparent substrate intended to form the support of the device 100. The first bonding layer 112 has properties suited to the implementation of a direct bonding: very low roughness, suitable material, etc. This first bonding layer 112 comprises for example SiO.sub.2, and has a thickness for example between around 1 nm and 20 m.

[0081] As shown in FIG. 1B, the first substrate 102 and the layers 104, 106, 108, 110 and 112 formed on the first substrate 102 are transferred onto a second at least partially transparent substrate 114 and on which is formed beforehand a second bonding layer 116 suitable for the implementation of a direct bonding with the first bonding layer 112. The second bonding layer 116 comprises for example SiO.sub.2 and is formed by PVD.

[0082] The second substrate 114 comprises at least one partially transparent material corresponding for example to glass, or instead a polymer material. In the case of a second supple/flexible substrate 114, this may be arranged on a rigid support during the transfer of the first substrate 102 and layers 104-112 thereon. The thickness of the second substrate 114 is for example equal to several hundreds of microns. When the second substrate 114 corresponds to a substrate made of polymer material, its thickness is for example between around 1 m and 1 mm.

[0083] Within the stack thereby obtained, the low adherence force interface formed between the separation layers 104, 106 corresponds, among all the interfaces of the stack, to that which has the lowest adherence force between two successive layers of the stack.

[0084] A mechanical separation is next carried out at this low adherence force interface between the separation layers 104, 106. This mechanical separation is for example carried out by introducing a blade between the two wafers. At the end of this mechanical separation, the stack remaining conserved comprises the second substrate 114 on which the layers 108 and 110 are made integral through the bonding layers 112+116. The remaining first substrate 102 may be reused later, for example for the production of another device 100. The material and the thickness of the bonding layers 112, 116 are chosen such that the assembly of these two bonding layers forms together an at least partially transparent element.

[0085] The second separation layer 106 is removed after the separation step, for example by dry RIE (reactive ion etching). Another at least partially transparent electrode layer 118, for example similar to the electrode layer 110, is next produced on the layer 108 (see FIG. 1C).

[0086] The device 100 is next completed by structuring, by the implementation of lithography and etching steps, of the layers 110, 108 and 118 according to the pattern desired for the device 100. In FIG. 1D, the layers 108 and 118 are etched in order that parts of each of these layers are electrically accessible, that is to say not covered by the other layers.

[0087] In the first embodiment described previously, the first separation layer 104 comprises the noble metal and the second separation layer 106 comprises SiO.sub.2 and/or silicon nitride. According to an alternative, it is possible that the first separation layer 104 comprises SiO.sub.2 and/or silicon nitride, and that the second separation layer 106 comprises the noble metal. In this case, the first separation layer 104, when it comprises SiO.sub.2, is for example produced by thermal oxidation of the upper face of the first substrate 102 when this first substrate 102 comprises silicon.

[0088] In the first embodiment described previously, the making integral of the first substrate 102 and the layers 104-110 with the second substrate 114 is carried out by the implementation of a direct bonding between the two bonding layers 112, 116 formed beforehand on each of the parts of the device 100 to be made integral. In an alternative, this making integral may be obtained by forming on the first electrode layer 110 and/or on the second substrate 114 at least one at least partially transparent adhesive layer, corresponding for example to a layer of polymer glue of thickness for example between around 1 m and 100 m.

[0089] Other bonding means may also be envisaged to achieve making the first substrate 102 and the layers 104-110 integral with the second substrate 114, from the moment that this making integral forms an at least partially transparent interface and having an adherence force greater than that formed between the separation layers 104, 106.

[0090] In the first embodiment described above, the device 100 corresponds to a piezoelectric transducer device and the layer 108 thus comprises an at least partially transparent piezoelectric material. In an alternative, the device 100 may be configured to carry out a different transduction from a piezoelectric transduction. The nature of the material used for the layer 108 is in this case suited to the type of transduction intended to be carried out by the device 100. It is for example possible that the material of the layer 108 is a pyroelectric and/or piezoelectric and/or ferroelectric and/or dielectric material. According to another alternative, the device 100 may correspond to a component other than a transducer device, such as for example a capacitor or a memory. The nature of the material of the functional layer 108 is in all cases suited to the function that has to be fulfilled by the functional layer 108 (isolation, memorisation, transduction, etc.).

[0091] In the first embodiment described previously, the low adherence force interface is formed thanks to the intrinsic properties of the materials of the separation layers 104, 106, due to the fact that SiO.sub.2 and silicon nitride adhere poorly to noble metals. In an alternative, it is possible that the low adherence force of the interface between the donor substrate (first substrate 102) and the layers 108, 110 to transfer onto the receiver substrate (second substrate 114) is obtained thanks to the implementation of at least one step degrading the adherence properties of this interface and reducing the adherence force at this interface between the materials of the first and second separation layers 104, 106. As an example, during the deposition of a layer 108 comprising PZT on the second separation layer 106, it is possible to implement a thermal treatment making atoms of lead coming from the PZT diffuse from the layer 108 into the SiO.sub.2 of one of the separation layers 104, 106. With such a thermal treatment, for example implemented at a temperature greater than or equal to around 700 C., a SiO.sub.2+Pb mixture in liquid phase forms at the interface between the first and second separation layers 104, 106. When the temperature drops, cavities are then created at this interface, in the layer formed of the SiO.sub.2 and lead mixture. These cavities reduce the adherence between the separation layers 104, 106. The mechanical separation next carried out is similar to that described previously.

[0092] This degradation, or reduction, of the adherence force of the interface between the separation layers 104, 106 may thus be advantageously carried out when the intrinsic properties of the materials used for these separation layers 104, 106 do not bring about, without additional intervention, the formation of a low adherence force interface.

[0093] In the first embodiment described previously, the second at least partially transparent substrate 114 corresponds to a layer of non-structured material. In an alternative, it is possible that one or more cavities are produced by etching through at least one part of the thickness of the second substrate 114, from a rear face 120 of this second substrate 114, in order to confer a certain degree of mobility on the layers 108, 110, 118. FIG. 2 shows the device 100 according to this alternative embodiment, the reference 122 designating a cavity formed through a part of the thickness of the second substrate 114.

[0094] A method for producing the device 100 according to a second embodiment is described below in relation with FIGS. 3A to 3D.

[0095] As for the first embodiment, the layers 104, 106 and 108 are produced on the first substrate 102 (FIG. 3A). However, unlike the first embodiment in which the electrode layer 110 is formed on the layer 108, no electrode layer is here formed on the layer 108. In addition, in this second embodiment, the bonding between the substrates 102, 114 will be achieved by an adhesive layer. Thus, the bonding layer 112 is not produced at the top of the stack formed on the first substrate 102.

[0096] The substrates 102, 114 are made integral with each other through an adhesive layer 119 formed on the second substrate 114 and with which the layer 108 is made integral (FIG. 3B). The adhesive layer 119 comprises for example a polymer glue.

[0097] In an alternative or as a complement, the adhesive layer may be produced on the layer 108.

[0098] A mechanical separation is next carried out between the separation layers 104, 106, then the second separation layer 106 is removed and the electrode layer 118 is produced on the layer 108 (FIG. 3C).

[0099] The device 100 according to this second embodiment is completed by etching the electrode layer 118 in order that the remaining portions 120 of this layer 118 form, on a single face of the layer 108, the electrodes of the device 100 (FIG. 3D). These electrodes 120 form for example interdigitated combs.

[0100] FIG. 4 shows the device 100 according to an alternative of the second embodiment, including the cavity 122 formed through at least one part of the thickness of the second substrate 114.

[0101] The different exemplary embodiments and the different alternative embodiments described may apply for each of the embodiments.