Switch based on phase-change material

Abstract

The present description relates to a switch (200) based on a phase-change material, comprising: - one region (103) made from the phase-change material, connecting first (101A) and second (101B) conduction electrodes of the switch; and - a heating element (205) electrically isolated from the region of phase-change material and connecting first (109A) and second (109B) control electrodes of the switch, wherein the heating element comprises at least two conductive regions (207A, 207B) located vertically above the region of phase-change material, said conductive regions being electrically connected to one another and separated laterally by an isolating region (119), vertically above the region of phase-change material.

Description

[0001] B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0002] DESCRIPTION

[0003] Phase-change material-based switch Technical field

[0004]

[0001] This description relates generally to electronic devices. This description relates more particularly to switches based on a phase-change material, capable of alternating between a crystalline, electrically conductive phase and an amorphous, electrically insulating phase.

[0005] Previous technique

[0006]

[0002] Various applications take advantage of switches, or switches, based on a phase-change material to allow or prevent the flow of an electric current in an electronic circuit. Such switches can be implemented in radio frequency communication applications, for example, to switch an antenna between transmit and receive modes, activate a filter corresponding to a frequency band, etc.

[0007]

[0003] Existing phase-change material switches, however, have several drawbacks. Summary of the invention

[0008]

[0004] It would be desirable to overcome all or part of the disadvantages of existing phase-change material switches.

[0009]

[0005] To this end, one embodiment provides a switch based on a phase-change material comprising:

[0010] - a region in said phase-change material connecting the first and second conduction electrodes of the switch; and

[0011] - an electrically insulated heating element from region B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0012] in said phase-change material and connecting the first and second control electrodes of the switch, wherein the heating element comprises at least two conductive regions situated above the region in said phase-change material, said conductive regions being electrically connected to each other and separated laterally, above the region in said phase-change material, by an insulating region.

[0013]

[0006] According to one embodiment, the switch has:

[0014] - a first dimension equal to a width of said insulating region;

[0015] - a second dimension equal to the width of the heating element;

[0016] - a third dimension equal to the distance separating the first and second conduction electrodes; and

[0017] - a fourth dimension equal to a width of a portion of the region in said phase-change material intended to be melted during a switching step of the switch, the second dimension being between 1.2 times the fourth dimension and one time the third dimension, preferably between 0.6 times the fourth dimension and one time the third dimension, more preferably between 0.6 times and 1.4 times the fourth dimension, even more preferably between 0.8 times and 1.2 times the fourth dimension.

[0018]

[0007] According to one embodiment, the first dimension is less than the second dimension, preferably less than 0.7 times the second dimension, more preferably equal to about 0.6 times the second dimension.

[0019]

[0008] According to one embodiment, the first dimension is less than 0.5 times the third dimension. B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0020]

[0009] According to one embodiment, the second dimension is within a range of 1.5 to 4 pm, preferably equal to about 2 or 3 pm.

[0021]

[0010] According to one embodiment, the third dimension is within a range from 1 to 10 pm, preferably within a range from 1 to 5 pm, more preferably equal to about 4 pm.

[0022]

[0011] According to one embodiment, the fourth dimension is equal to approximately two-thirds of the third dimension.

[0023]

[0012] According to one embodiment, the switch comprises exactly first and second conductive regions laterally isolated by a single insulating region.

[0024]

[0013] According to one embodiment, the heating element comprises at least three conductive regions.

[0025]

[0014] According to one embodiment, the region in said phase-change material is interposed between the heating element and a substrate in and on which the switch is formed.

[0026]

[0015] According to one embodiment, the heating element is interposed between the region in said phase-change material and a substrate in and on which the switch is formed.

[0027]

[0016] According to one embodiment, the switch further comprises a thermally conductive layer, preferably of aluminum nitride, interposed between the substrate and the heating element.

[0028]

[0017] According to one embodiment, the first and second conduction terminals are intended to be connected to a radio frequency circuit. B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0029] Brief description of the drawings

[0030]

[0018] These features and advantages, as well as others, will be described in detail in the following description of particular embodiments, given by way of non-limiting example, in relation to the accompanying figures, among which:

[0031]

[0019] Figure IA is a schematic and partial perspective view of an example of a phase-change material-based switch;

[0032]

[0020] Figure IB is a side and cross-sectional view along plane BB of Figure IA, schematic and partial, of the switch of Figure IA;

[0033]

[0021] Figure 2A is a schematic and partial perspective view of an example of a phase change material switch according to one embodiment;

[0034]

[0022] Figure 2B is a schematic and partial side and cross-sectional view along plane BB of Figure 2A of the switch of Figure 2A;

[0035]

[0023] Figure 3 is a schematic and partial side and cross-sectional view of a variant of the switch in Figure 2A;

[0036]

[0024] Figure 4 is a graph illustrating temperature variations as a function of position within a phase-change material region of the switches in Figures IA, 2A and 3; and

[0037]

[0025] Figure 5 is a graph illustrating temperature variations as a function of position inside a heating element of the switches in Figures IA, 2A and 3.

[0038] Description of the implementation methods

[0039]

[0026] The same elements have been designated by the same reference numerals in the different figures. In particular, the structural and / or functional elements common to B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0040] Different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0041]

[0027] For the sake of clarity, only the steps and elements useful for understanding the described embodiments have been shown and are detailed. In particular, the control circuits of switches based on a phase-change material and the devices and applications in which such switches may be provided have not been detailed, the described embodiments and variants being compatible — possibly subject to adaptations within the grasp of a person skilled in the art upon reading this description — with conventional control circuits of switches based on a phase-change material and with conventional devices and applications implementing switches based on a phase-change material.

[0042]

[0028] Unless otherwise specified, when referring to two elements connected together, this means directly connected without intermediate elements other than conductors, and when referring to two elements coupled together, this means that these two elements can be connected or linked through one or more other elements.

[0043]

[0029] In the following description, when reference is made to absolute positional qualifiers, such as "front," "back," "top," "bottom," "left," "right," etc., or relative positional qualifiers, such as "above," "below," "superior," "lower," etc., or to orientational qualifiers, such as "horizontal," "vertical," etc., reference is made, unless otherwise specified, to the orientation of the figures. B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0044]

[0030] Unless otherwise specified, the expressions "approximately", "about", "substantially", and "in the order of" mean to within 10% or 10°, preferably to within 5% or 5°.

[0045]

[0031] In the following description, the terms "insulating" and "conducting" mean, unless otherwise specified, electrically insulating and electrically conductive respectively.

[0046]

[0032] Unless otherwise specified, the expression "in contact with" means "in mechanical contact with".

[0047]

[0033] Figure IA is a schematic and partial perspective view of an example of a switch 100 based on a phase change material, for example a radio frequency switch.

[0048]

[0034] In the example shown, the switch 100 comprises conduction electrodes 101A and 101B. The conduction electrodes 101A and 101B are intended, for example, to be connected to a radio frequency communication circuit, not detailed in the figures. By way of example, the conduction electrodes 101A and 101B are part of an antenna element of a transmit array or reflect array cell. The conduction electrodes 101A and 101B are made of a conductive material, for example, a metal such as copper or aluminum, or a metal alloy. Furthermore, the conduction electrodes 101A and 101B may have a single-layer or multi-layer structure.

[0049]

[0035] In the illustrated example, the switch 100 further comprises a region 103 made of a phase-change material connecting the conduction electrodes 101A and 101B. In the example shown, the region 103 made of phase-change material extends laterally on and in contact with a B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0050] part of the upper face of each conduction electrode 101A, 101B. In the illustrated example, the region 103 made of phase-change material has a width W PCM The width W PCM corresponds to a lateral dimension of region 103 measured along a horizontal axis Oy. The width W PCM is, for example, on the order of a few tens of micrometers, for example between 10 and 100 pm, for example between 30 and 100 pm. As an example, region 103 in phase-change material has a thickness T PCM on the order of 100 nm. The thickness T PCMcorresponds to a vertical dimension of region 103 measured along a vertical axis Oz orthogonal to the axis Oy.

[0051]

[0036] By way of example, region 103 of switch 100 is made of a so-called "chalcogenide" material, that is to say a material or alloy comprising at least one chalcogen element, for example a material from the family of germanium telluride (GeTe), antimony telluride (SbTe) or germanium-antimony-telluride (GeSbTe, commonly referred to by the acronym "GST").

[0052]

[0037] Generally speaking, phase-change materials are materials capable of alternating, under the effect of a temperature variation, between a crystalline phase and an amorphous phase, the amorphous phase having a higher electrical resistance than the crystalline phase. In the case of the switch 100, this phenomenon is exploited to obtain a blocked state, preventing the flow of current between the conduction electrodes 101A and 101B, when the material of region 103 is in the amorphous phase, and a conducting state, allowing the flow of current between the conduction electrodes 101A and 101B, when the material of region 103 is in the crystalline phase.

[0053]

[0038] In the example shown, the switch 100 further comprises a heating element 105 located on the region 103 in B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0054] phase-change material. In the illustrated example, the heating element 105 includes a conductive region 107 in the form of a substantially rectangular band extending, above the region 103, along the Oy axis. The conductive region 107 has, for example, a thickness T H on the order of 100 nm and a width W H within a range of 1.5 to 4 μm, for example a width W H equal to approximately 2 μm or equal to approximately 3 μm. The thickness T H and the width W HThese correspond respectively to the vertical and lateral dimensions of region 107 measured along the vertical axis Oz and along a horizontal axis Ox orthogonal to the axis Oy. For example, the conductive region 107 is made of a metal, such as tungsten, or a metal alloy, such as titanium nitride. In the example shown, the ends of the conductive region 107 are connected to control electrodes 109A and 109B of the switch 100 by conductive vias or pads 111.

[0055]

[0039] During the switching of the switch 100 between the conducting and blocked states, the control electrodes 109A and 109B of the heating element 105 are, for example, subjected to a control voltage causing a current to flow through the conductive region 107. This current causes, by Joule effect and then mainly by radiation and, secondarily, by conduction inside the structure of the switch 100, a temperature rise of the region 103 in the underlying phase-change material from its upper face, located opposite the conductive region 107.

[0056]

[0040] More specifically, to switch the switch 100 from the blocked state to the conducting state, the phase-change material region 103 is heated, by means of the heating element 105, for example to a temperature Ti and for a duration Di. The temperature Ti and the duration Di are B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0057] chosen to induce a phase change in the material of region 103 from the amorphous phase to the crystalline phase. The temperature Ti, for example, is higher than the crystallization temperature and lower than the melting temperature T FUS of the phase-change material in region 103. For example, the temperature Ti is between 150 and 350 °C and the time Di is less than 1 ps. In the case where region 103 is germanium telluride, the temperature T1 is, for example, approximately 300 °C and the time Di is, for example, between 100 ns and 1 ps.

[0058]

[0041] Conversely, to switch the switch 100 from the conducting state to the blocking state, the phase-change material region 103 is heated, by means of the heating element 105, for example to a temperature T2 higher than the temperature Ti, and for a duration D2 shorter than the duration Di. The temperature T2 and the duration D2 are chosen so as to induce a phase change of the material in region 103 from the crystalline phase to the amorphous phase. The temperature T2 is, for example, higher than the melting temperature T FUS of the phase-change material in region 103. For example, the temperature T2 is between 600 and 1000 °C and the time interval D2 is less than 500 ns. In the case where region 103 is germanium telluride, the temperature T2 is, for example, approximately 700 °C and the time interval D2 is, for example, approximately 100 ns.

[0059]

[0042] The switch 100 is said to be "indirectly heated," the temperature rise of the phase-change material being obtained by the circulation of a current through a heating element electrically isolated from the phase-change material, as opposed to "directly heated" switches which have no heating element and in which the temperature rise results from a circulation B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0060] of current directly through the region in phase-change material.

[0061]

[0043] Figure IB is a schematic and partial side and cross-sectional view along plane BB of Figure IA of the switch 100 of Figure IA. In the illustrated example, plane BB of Figure IA is a vertical plane parallel to a conduction direction of the switch 100.

[0062]

[0044] In figures IA and IB, the direction of conduction of the switch 100 is substantially parallel to the horizontal axis Ox and the plane BB is parallel to a vertical plane Oxz orthogonal to the axis Oy.

[0063]

[0045] In the example shown, the switch 100 is formed in and on a substrate 113. The substrate 113 is, for example, a wafer, or a piece of wafer, made of a semiconductor material such as silicon.

[0064]

[0046] In the illustrated example, the upper surface of the substrate 113 is coated with an insulating layer 115. For example, the layer 115 is made of an oxide, for example silicon oxide, and has a thickness of approximately 500 nm. In the illustrated example, a portion of the layer 115 extends between the conduction electrodes 101A and 101B of the switch 100, and electrically isolates electrode 101A from electrode 101B. The layer 115 is, for example, flush with the upper surface of electrodes 101A and 101B, as illustrated in Figure IB.

[0065]

[0047] In the illustrated example, the conduction electrodes 101A and 101B of the switch 100 are separated laterally from each other by a distance W GA p, measured along the Ox axis. As an example, the distance W GAp is within a range from 1 to 10 pm, for example, within a range from 1 to 5 pm, for example, equal to approximately 4 pm. B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0066]

[0048] In the example shown, the upper surface of the phase-change material region 103 is coated with an insulating layer 117. For example, the layer 117 is made of a dielectric and thermally conductive material, for example, a nitride such as aluminum nitride or silicon nitride. In the illustrated example, the conductive region 107 of the heating element 105 is located on and in contact with the upper surface of the layer 117, directly above the phase-change material region 103. The conductive region 107 is electrically insulated from the region 103 by the layer 117.

[0067]

[0049] The upper face of the conductive region 107 and the portions of the upper face of the insulating layer 117 not covered by the conductive region 107 are, for example, covered with a stack comprising insulating layers 119, 121 and 123. In the example shown, the insulating layer 119 is located on and in contact with the lateral and upper faces of the conductive region 107 and with portions of the upper face of the insulating layer 117 not covered by the region 107. Furthermore, in this example, the insulating layer 121 is located on and in contact with the upper face of the insulating layer 119, and the insulating layer 123 is located on and in contact with the upper face of the insulating layer 121.

[0068]

[0050] The insulating layer 119 is, for example, made of the same material as the insulating layer 115, for example an oxide such as silicon dioxide. The insulating layer 121 is, for example, made of the same material as the insulating layer 117, for example a nitride such as aluminum nitride or silicon nitride. The insulating layer 123 is, for example, made of a nitride such as silicon nitride.

[0069]

[0051] The insulating layer 123 is, for example, thermally insulating and is intended to contain the heat produced by B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0070] the heating element 105 inside the structure of the switch 100.

[0071]

[0052] In order not to overload the drawing, the substrate 113 and the insulating layers 115, 117, 119, 121 and 123 of the switch 100 have not been shown in figure IA.

[0072]

[0053] Figure 2A is a schematic, partial perspective view of an example of a phase-change material switch 200, for example, a radio frequency switch, according to one embodiment. The switch 200 of Figure 2A includes elements common to the switch 100 of Figures IA and IB. These common elements will not be detailed again below.

[0073]

[0054] The switch 200 includes a heating element 205 located on the phase-change material region 103. In one embodiment, the heating element 205 comprises two conductive regions 207A and 207B located directly above the phase-change material region 103. Each region 207A, 207B has, for example, the shape of a substantially rectangular strip extending above the region 103 along the Oy axis. The conductive regions 207A and 207B have thicknesses T, respectively. H A and T HB - Thicknesses T HA and T HB are, for example, identical, except for manufacturing variations. For example, the thicknesses T HA and T H B are approximately equal to the thickness T H of the conductive region 107 of the heating element 105 of the switch 100.

[0074]

[0055] The conductive regions 207A and 207B are electrically connected to each other. In the illustrated example, the ends of the conductive regions 207A and 207B located on the same side of the phase-change material region 103 are electrically connected to each other by a conductive region 208A of the heating element 205 located off-plumb of the region 103. Similarly, the other B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0075] The ends of the conductive regions 207A and 207B, located on the opposite side of the phase-change material region 103, are electrically connected to each other by another conductive region 208B of the heating element 205, located off-center from the region 103. For example, each conductive region 207A, 207B is made of a metal, for example tungsten, or a metal alloy, for example titanium nitride. The conductive regions 208A and 208B are, for example, made of the same material as regions 207A and 207B. In the illustrated example, the conductive regions 208A and 208B are connected, respectively, to the control electrodes 109A, 109B of the switch 200 by the conductive vias or pads 111.

[0076]

[0056] In the example shown, the conducting regions 207A, 207B, 208A and 208B are substantially coplanar. In this example, the conducting regions 207A, 207B, 208A and 208B form, for example, a conducting frame having, in top view, an annular shape.

[0077]

[0057] Figure 2B is a schematic and partial side and cross-sectional view along plane BB of Figure 2A of the switch 200 of Figure 2A. In the illustrated example, plane BB of Figure 2A is a vertical plane parallel to the conduction direction of the switch 200.

[0078]

[0058] In the example shown, the insulating layer 119 is located on and in contact with the lateral and upper faces of each conductive region 207A, 207B of the heating element 205 and on and in contact with portions of the upper face of the insulating layer 117 not covered by regions 207A and 207B. In this example, regions 207A and 207B have widths W, respectively H A and W H B • Each width W H A, W H B corresponds to a lateral dimension of region 207A, 207B measured along the Oy axis. The widths W H A and W H For example, B are essentially identical to B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0079] manufacturing variations nearby. As an example, each width W HA , W HB is equal to approximately 1 pm.

[0080]

[0059] According to one embodiment, the conductive regions 207A and 207B are separated laterally, directly above the phase-change material region 103, by a portion of the insulating layer 119 forming an insulating region extending laterally between regions 207A and 207B. In the illustrated example, regions 207A and 207B are separated laterally from each other by a distance W AB , measured along the Ox axis. The distance W AB In this example, this corresponds to the width of the insulating region extending laterally between the conducting regions 207A and 207B. The distance W AB is, for example, approximately equal to the width W HA , W HB of each region 207A, 207B. As an example, the distance W AB is equal to approximately 1 pm.

[0081]

[0060] In the example shown, the opposite ends of the conductive regions 207A and 207B of the heating element 205 are separated by a distance W T The distance W T is called the "width of the heating element" and is, in this example, equal to the sum of the widths W HA and W HB and the distance W AB For example, the width W T The width of the heating element 305 is approximately equal to the width W H of the conductive region 107 of switch 100.

[0082]

[0061] In order not to overload the drawing, the substrate 113 and the insulating layers 115, 117, 119, 121 and 123 of the switch 200 have not been shown in figure 2A.

[0083]

[0062] Figure 3 is a schematic and partial side and sectional view of a 300 switch based on a phase-change material, corresponding to a variant of the 200 switch. The section plane of Figure 3 is, for example, analogous to section plane BB of Figure 2B. The 300 switch of Figure 3 comprises common elements B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0084] with switch 200 of figures 2A and 2B. These common elements will not be detailed again below.

[0085]

[0063] The switch 300 of Figure 3 differs from the switch 200 of Figures 2A and 2B in that the switch 300 comprises a heating element 305 having a conductive region 307C interposed laterally between the conductive regions 207A and 207B. The conductive regions 207A, 307C, and 207B are located directly above the phase-change material region 103. The region 307C, for example, has the shape of a substantially rectangular band extending parallel to the bands formed by the regions 207A and 207B, above the region 103, along the Oy axis. The conductive regions 207A, 307C, and 207B, for example, have identical thicknesses, apart from manufacturing variations. The thickness of each conductive region 207A, 307C, 207B is, for example, approximately equal to the thickness T H of the conductive region 107 of the heating element 105 of the switch 100.

[0086]

[0064] The conductive regions 207A, 307C and 207B are electrically connected to each other. The ends of the conductive regions 207A, 307C and 207B located on the same side of the phase-change material region 103 are, for example, electrically interconnected by the conductive region 208A located off-plumb of the region 103. Similarly, the other ends of the conductive regions 207A, 307C and 207B, located on the other side of the region 103, are, for example, electrically interconnected by the conductive region 208B located off-plumb of the region 103. As an example, each conductive region 207A, 307C, 207B is made of a metal such as tungsten or of a metal nitride such as titanium nitride. B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0087]

[0065] In the example shown, the conductive regions 207A, 307C, and 207B are substantially coplanar. In the example shown, the insulating layer 119 is located on and in contact with the lateral and upper faces of each conductive region 207A, 307C, and 207B of the heating element 305, and on and in contact with portions of the upper face of the insulating layer 117 not covered by regions 207A, 307C, and 207B. In this example, region 307C has a width W HC The width W HC corresponds to a lateral dimension of region 307C measured along the Ox axis. In the example shown, the width W H c of region 307C is strictly less than the widths W H A and W H B of regions 207A and 207B. As an example, the width W H it is approximately twice as small as each width W H A, W H B - As an example, each width W H A, W HB is approximately 0.5 pm. As an example, the width W H c is equal to approximately 0.2 pm.

[0088]

[0066] According to one embodiment, the conductive regions 207A, 307C, and 207B are separated laterally from each other, directly above the phase-change material region 103, by portions of the insulating layer 119 forming insulating regions extending laterally between region 207A and region 307C, and between region 307C and region 207B. In the illustrated example, regions 207A and 307C are separated laterally from each other by a distance W A c, measured along the Ox axis. The distance W A In this example, c corresponds to the width of the insulating region extending laterally between the conducting regions 207A and 307C. Similarly, regions 307C and 207B are separated laterally from each other by a distance W C B, measured along the Ox axis. The distance WC In this example, B corresponds to the width of the insulating region extending laterally between the conducting regions 3070 and 207B. The distance W A c is, for example, approximately equal to the distance B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0089] W C B • As an example, each distance W AC , W C B is equal to approximately 0.9 pm.

[0090]

[0067] By way of example, the sum of the widths W HA , W HC and W H B and distances W AC and W C B of switch 300 is approximately equal to the width W H of the conductive region 107 of switch 100.

[0091]

[0068] Figure 4 is a graph 400 illustrating, by curves 401, 403 and 405, temperature variations T (in kelvins, K) as a function of a position P (in micrometers, pm) along the Ox axis inside the region 103 in phase change material of each switch 100, 200, 300, for example in the vicinity of an interface between the region 103 and the insulating layer 115.

[0092]

[0069] The temperature variations T illustrated by curves 401, 403, and 405 are, for example, obtained following a heating step designed to induce a phase change in the material of regions 103 from the crystalline phase to the amorphous phase. During this step, the heating element 105, 205, 305 of the switch 100, 200, 300 is, for example, controlled to cause melting of the material in region 103 in a portion of region 103 having a width W FUS The width W FUSis, for example, equal to approximately two-thirds of the distance W GA p. Within this part of region 103 intended to be melted, the temperature T is higher than the melting temperature T FUS of the phase-change material.

[0093]

[0070] In the illustrated example, the distance W GAP is equal to approximately 4 pm, the width W FUS is equal to approximately 2.7 pm and the melting temperature T FUS is equal to approximately 1000 K.

[0094]

[0071] In the example shown, curves 401, 403 and 405 show that the temperature T is inhomogeneous within the regions 103 in phase-change material of B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0095] switches 100, 200, and 300. In particular, the temperature T is, in the case of switch 100, higher in a central part than in the lateral parts of region 103. This is because electrodes 101A and 101B, located near the lateral parts of region 103, are made of thermally conductive materials that help dissipate the heat produced by the heating element 105 in region 103. Region 103 exhibits, along the Ox axis, a temperature difference that is greater the greater the distance W G AP is large. Switches 100, 200, and 300 exhibit temperature differences ΔT1, ΔT2, and ΔT3 between maximum temperatures T MAX1 , T MAX2 and T MAX3 respectively reached by their regions 103 and the melting temperature T FUS -

[0072] In the illustrated example, the maximum temperatures T MAX1 , T MAX2 and T MAX3are respectively equal to approximately 1130 K, 1065 K, and 1040 K. Furthermore, the temperature differences between ATi, AT2, and AT3 are respectively equal to approximately 130 K, 65 K, and 40 K. This corresponds to exceedances of the melting point T FUS of the phase change material 103 respectively equal to approximately 13%, 6%, 5% and 4%.

[0096]

[0073] One advantage of switches 200 and 300 is that they have temperature differences AT2 and AT3 that are lower than the temperature difference AT Fof switch 100. This stems from the fact that, unlike the heating element 105 of switch 100, which comprises only a single conductive region 107 directly above region 103, the heating elements 205 and 305 of switches 200 and 300 comprise several conductive regions 207A, 207B, and possibly 307C directly above region 103. This allows for maximum temperatures TMAX2 and TMAXS to be lower than the maximum temperature TMAXI, thus giving the B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0097] 200 and 300 switches offer increased reliability compared to the 100 switch.

[0098]

[0074] Figure 5 is a graph 500 illustrating, by curves 501, 503 and 505, variations of temperature T (in kelvins, K) as a function of a position P (in micrometers, pm) along the Ox axis inside the heating elements 105, 205 and 305 of the switches 100, 200 and 300, respectively, for example in the vicinity of an interface between the heating element 105, 205, 305 and the insulating layer 117.

[0099]

[0075] The temperature variations T illustrated by curves 501, 503 and 505 are obtained for example at the end of the heating step intended to cause a phase change of the material in regions 103 from the crystalline phase to the amorphous phase as described previously in relation to Figure 4.

[0100]

[0076] In the example shown, the distance W G AP is approximately 4 pm and the width W H is equal to approximately 3 pm.

[0101]

[0077] In the example shown, curves 501, 503, and 505 demonstrate that the temperature T is inhomogeneous inside the heating elements 105, 205, and 305, respectively. The switches 100, 200, and 300 exhibit temperature differences AT4, AT5, and AT6 between maximum temperatures T MAX4 , T MAX5 and T MAX6 respectively reached by their heating elements 105, 205 and 305 and a minimum temperature T MIN reached by the heating element 105 of the switch 100.

[0102]

[0078] In the illustrated example, the maximum temperatures T MAX1 , T MAX2 and T MAX3 are respectively equal to approximately 1315 K, 1240 K and 1215 K, and the temperature T MIN is equal to approximately 1170 K. In addition, the temperature differences AT4, AT5 and ATg are respectively equal to approximately 145 K, 70 K and 45 K.

[0103]

[0079] One advantage of switches 200 and 300 is that they have, within the conductive regions B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0104] 207A, 207B, and possibly 307C of their heating elements 205 and 305, exhibit temperature differences ΔT5 and ΔT6 that are smaller than the temperature difference ΔT4 observed in the heating element 105 of the switch 100. This advantage stems from the fact that, unlike the heating element 105 of the switch 100, which comprises a single conductive region 107 directly above the region 103, the heating elements 205 and 305 of the switches 200 and 300 comprise several conductive regions 207A, 207B, and possibly 307C directly above the region 103. This reduces the maximum temperature reached in the heating elements 205 and 305, thus resulting in switches 200 and 300 with increased reliability compared to the switch 100.

[0105]

[0080] Furthermore, the heating element 105, 205, 305 of each switch 100, 200, 300 consumes, in order to change the phase-change material of region 103 from the crystalline state to the amorphous state, an energy E given by the following formula:

[0106] [Math 1]

[0107] E = ∫₀ᵗ i²_H(t).R(t)dt

[0108]

[0109] '0

[0110]

[0081] In the equation above, i H represents a current flowing through the heating element for a duration of a pulse allowing the phase change and R (t) represents a resistance of the heating element during the pulse.

[0111]

[0082] The energy consumed E is proportional to the temperature T produced by the Joule effect. Since the temperature T is more uniform and the maximum temperature lower in the case of switches 200 and 300 than in the case of switch 100, the energy consumed E by switches 200 and 300 is less than in the case of switch 100. For example, in a case where the width W PC M is B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0112] equals approximately 19 pm and where the distance W GA p is equal to about 4 pm, the energy consumed E to cause a phase change of the material in region 103 from the crystalline phase to the amorphous phase is equal to about 670 nJ for switch 100, compared to about 560 nJ for switch 200. This represents an energy saving of about 16%.

[0113]

[0083] The switches 100, 200 and 300 exhibit radio frequency performance which depends, among other things, on a resistance R O FF and a capacity C O FF of the switch in the blocked state. The resistance R O FF and the C capacity O The FF values ​​in the blocked state of a switch are related and are proportional to the width W. F us of the part of region 103 in phase change material which is amorphized during the phase change from the crystalline phase to the amorphous phase.

[0114]

[0084] Because switches 200 and 300 have a higher energy efficiency than switch 100, the melting and quenching operation enabling the phase change from the crystalline phase to the amorphous phase is more efficient in switches 200 and 300 than in switch 100. For the same energy consumed E, the width W FThe amount of amorphous material is thus greater in the case of switches 200 and 300 than in the case of switch 100. The larger the width W F The larger the us, the larger the resistance RQFF, which allows the switch to exhibit greater electrical insulation, and the larger the capacitance C O FF is low. Furthermore, the wider W F The larger the usable area, the higher the power handling capacity of the switch.

[0115]

[0085] By way of example, in a case where the width W PC M is approximately 19 pm and where the distance W GA p is equal to approximately 4 pm, the resistance R O FF is approximately 1300 kQ for switch 200, compared to approximately 930 kQ for switch 100. This represents a difference in resistance R O FF of B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0116] the order of 40% in favor of switch 200. Furthermore, in this example, the capacity CO FF is approximately 9 fF for the 200 switch, compared to approximately 11 fF for the 100 switch. This represents a difference in capacitance C O FF of around 20% in favor of switch 200.

[0117]

[0086] In addition, each switch 100, 200, 300 has a Figure of Merit (FoM) equal to the product of a resistance R ON in the state passing through the capacitor C O FF of the switch. In order to optimize the radio frequency performance of switches 100, 200, and 300, it is desirable to minimize their factor of merit. The resistance R ON being substantially identical for switches 100, 200 and 300, switches 200 and 300 exhibit, due to their capacity C O FF is lower than that of switch 100, a lower factor of merit than that of switch 100.

[0118]

[0087] In order to ensure that the temperature T in the phase-change material regions 103 of the switches 200 and 300 is as homogeneous as possible and that the temperature differences AT2 and AT3 are as small as possible, the width W T The heating elements 205 and 305 are preferably greater than 80% of the width W F us, more preferably greater than the width W F us -

[0088] In addition, the width W T is preferably less than the distance W GA p.

[0119]

[0089] The space(s) extending laterally between the metallic regions of the heating elements 205 and 305 of the switches 200 and 300 have a total width W s In the case of switch 200, the width W s is equal to the distance W AB In the case of switch 300, the width W s is equal to the sum of the distances W AC and W CB. B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0120]

[0090] The width W s is preferably less than 70% of the width W T , more preferably equal to about 60% of the width W T .

[0121]

[0091] Furthermore, the width W s is preferably less than 50% of the distance W GAP .

[0122]

[0092] By way of example, the width W FUS is equal to approximately two-thirds of the distance W GAP To limit the temperature rise to approximately 160 K above temperature T FUS the width W T is, for example, greater than approximately 50% of the distance W GAP (80% * 2 / 3 * W) GAP ). As an alternative, to limit the temperature rise to approximately 110 K above temperature T FUS the width W T is, for example, greater than about two-thirds of the distance W GAP .

[0123]

[0093] Furthermore, in order to keep the energy consumed E as low as possible, the width W T is preferably within a range of 0.6 times the width W FUS at once the length W GAP The width W T is most preferably within a range of 0.6 times to 1.4 times the width W FUS , and even more preferably within a range of 0.8 to 1.2 times the width W FUS .

[0124]

[0094] By way of example, the width W FUS is equal to approximately two-thirds of the distance W GAP To limit the energy consumed E to 250 nJ, the width W T is between approximately 40% (0.6 * 2 / 3 * W GAP ) and approximately 90% (1.4 * 2 / 3 * W GAP ) of the length W GAP As an alternative, to limit the energy consumed E to 220 nJ, the width W T is between approximately 50% (0.8 * 2 / 3 * W GAP) and approximately 80% (1.2 * 2 / 3 * W GAP ) of the length W GAP .

[0125]

[0095] Advantageously, the width W FUS is maximized while minimizing the temperature rise T and the energy consumed E when:

[0126] - the width W T is within a range of 1, 2 B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0127] times the width W FUS at once the length W GAF ;

[0128] - the width W s is less than 50% of the length W GAF ; And

[0129] - the width W s is equal to approximately 60% of the width W T .

[0130]

[0096] By way of example, the width W FUS is equal to approximately two-thirds of the distance W GA p. If the width W T is between 80% of the length W GA p ( 1, 2 * 2 / 3 * W GA p) and 100% of the length WGA p and that the width W s is equal to approximately 60% of the width W T , then the width W FUS is between 73% and 80% of the length W GA p.

[0131]

[0097] Various embodiments and variants have been described. Those skilled in the art will understand that certain features of these various embodiments and variants could be combined, and other variants will become apparent to them. In particular, those skilled in the art are able, from the indications in this description, to foresee heating elements comprising more than three conductive regions.

[0098] Furthermore, those skilled in the art are able to transpose what has been described in relation to examples of switches 100, 200, and 300 having a structure in which the phase-change material region is interposed between the heating element and a substrate to switches having a structure in which the heating element is interposed between the phase-change material region and a substrate. Examples of such structures are described, for instance, in the article by N.Wainstein et al. entitled “Compact Modeling and Electrothermal Measurements of Indirectly Heated Phase-Change RE Switches” published in November 2020 in the journal IEEE Transactions on Electron Devices, vol. 67, no. 11, pp.

[0132] 5182-5187. B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764

[0133]

[0099] In this case, a person skilled in the art is also able, based on the indications in this description, to provide a thermally conductive layer, for example made of a nitride such as aluminum nitride, interposed between the substrate and the phase-change material region in order to facilitate heat dissipation. For this purpose, a person skilled in the art may, for example, refer to the article by N. El-Hinnawy et al. entitled “Experimental Demonstration of AIN Heat Spreaders for the Monolithic Integration of Inline Phase-Change Switches” published in April 2018 in the journal IEEE Electron Device Letters, vol. 39, no. 4, pp. 610-613.

[0134]

[0100] Finally, the practical implementation of the described embodiments and variants is within the reach of a person skilled in the art, based on the functional specifications given above. In particular, the described embodiments are not limited to the specific examples of materials and dimensions mentioned in this description.

Claims

B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764 DEMANDS 1. A (200; 300) phase-change switch comprising: - a region (103) in said phase-change material connecting the first (101A) and second (101B) conduction electrodes of the switch; and - a heating element (205; 305) electrically isolated from the region in said phase-change material and connecting the first (109A) and second (109B) control electrodes of the switch, in which the heating element comprises at least two conductive regions (207A, 207B; 207A, 307C, 207B) situated directly above the region in said phase-change material, said conductive regions being electrically connected to each other and laterally separated, directly above the region in said phase-change material, by an insulating region (119).

2. Switch (200; 300) according to claim 1, wherein the switch has: - a first dimension (W s ) equal to a width of said insulating region ( 119); - a second dimension (W T ) equal to a width of the heating element (205; 305); - a third dimension (W GA p) equal to a distance separating the first (101A) and second (101B) conduction electrodes; and - a fourth dimension (W FUS ) equal to a width of a portion of the region (103) in said phase-change material intended to be melted during a switching step of the switch, the second dimension (W T ) being between 1, 2 times the fourth dimension (W FUS ) and once the third dimension (W GA p), preferably between 0.6 times the Tl B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764 fourth dimension (W FUS ) and once the third dimension (W GA p), more preferably between 0.6 times and 1.4 times the fourth dimension (W FUS ), even more preferentially between 0.8 times and 1.2 times the fourth dimension (W FUS ).

3. Switch (200; 300) according to claim 2, wherein the first dimension (W s ) is less than the second dimension (W T ), preferably less than 0.7 times the second dimension (W T ), more preferably equal to about 0.6 times the second dimension (W T ).

4. Switch (200; 300) according to claim 2 or 3, wherein the first dimension (W s ) is less than 0.5 times the third dimension (W GA p).

5. Switch (200; 300) according to any one of claims 2 to 4, wherein the second dimension (W T) is within a range of 1.5 to 4 pm, preferably equal to about 2 or 3 pm.

6. Switch (200; 300) according to any one of claims 2 to 5, wherein the third dimension (W G AP) is within a range of 1 to 10 pm, preferably within a range of 1 to 5 pm, more preferably equal to about 4 pm.

7. Switch (200; 300) according to any one of claims 2 to 6, wherein the fourth dimension (W FUS ) is equal to approximately two-thirds of the third dimension (W GAP ).

8. Switch (200) according to any one of claims 2 to 7, comprising exactly first (207A) and second (207B) conductive regions laterally isolated by a single insulating region (119). B23906 PCT – DD24433 BR - 24-GR4CO-0308WO01 - B764 9. Switch (300) according to any one of claims 2 to 7, wherein the heating element comprises at least three conductive regions (207A, 307C, 207B).

10. Switch (200; 300) according to any one of claims 1 to 9, wherein the region (103) in said phase-change material is interposed between the heating element (205; 305) and a substrate (113) in and on which the switch is formed.

11. Switch (200; 300) according to any one of claims 1 to 9, wherein the heating element (205; 305) is interposed between the region (103) in said phase-change material and a substrate (113) in and on which the switch is formed.

12. Switch (200; 300) according to claim 11, further comprising a thermally conductive layer, preferably of aluminium nitride, interposed between the substrate and the heating element.

13. Switch (200; 300) according to any one of claims 1 to 12, wherein the first (101A) and second (101B) conduction terminals are intended to be connected to a radio frequency circuit.

Images