Phase change material based switch

Abstract

Phase change material based switch The present description relates to a switch (100) comprising: – first, second, third and fourth electrodes (101a, 101b, 101c, 101d); – a first region (105a) of a phase change material connecting the first and second electrodes; – a second region (105b) of a phase change material connecting the second and third electrodes; and – a third region (105c) of a phase change material connecting the second and fourth electrodes. Figure for abstract: Fig. 1A

Description

Title of the invention: Switch based on phase change material Technical field

[0001] The present description relates generally to electronic devices. The present 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. Prior art

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

[0003] Existing phase change material based switches, however, suffer from various drawbacks. Summary of the invention

[0004] There is a need to improve existing phase change material based switches.

[0005] For this, one embodiment provides a switch comprising: - first, second, third and fourth electrodes; - a first region of a phase change material connecting the first and second electrodes; - a second region of a phase change material connecting the second and third electrodes; and - a third region made of a phase change material connecting the second and fourth electrodes.

[0006] According to one embodiment, the switch further comprises first, second and third heating elements located respectively opposite the first, second and third regions of phase change material, each heating element being electrically insulated from said region located opposite.

[0007] According to one embodiment, the third heating element is intended to be controlled independently of the first and second heating elements.

[0008] According to one embodiment, the first and second heating elements are intended to be controlled simultaneously.

[0009] According to one embodiment, the first and second heating elements are connected in series between two control electrodes.

[0010] According to one embodiment, the first, second and third regions of phase change material are made of a chalcogenide material.

[0011] According to one embodiment, each of the first, second and third regions of phase change material is made of germanium telluride or germanium-antimony-tellurium.

[0012] According to one embodiment, the third region of phase change material has a volume smaller than that of the first and second regions of phase change material.

[0013] According to one embodiment, the first and second regions of phase change material have, in top view, different areas.

[0014] According to one embodiment, the first and second regions made of phase change material have, along the conduction direction of the switch, the same lateral dimension.

[0015] According to one embodiment, the first and second regions of phase change material have, along a direction orthogonal to the conduction direction of the switch, different lateral dimensions.

[0016] One embodiment provides a device comprising a switch as described and a ground plane to which the fourth electrode of the switch is connected. Brief description of the drawings

[0017] These characteristics and advantages, as well as others, will be explained in detail in the following description of particular embodiments given without limitation in relation to the attached figures among which:

[0018] [Fig.lA] and [Fig.lB] are schematic and partial views, respectively from above and in section along plane AA of [Fig.lA], of an example of a switch based on a phase change material according to one embodiment;

[0019] [Fig.2A], [Fig.2B] and [Fig.2C] are schematic and partial top views illustrating different states of the switch of Figures 1A and 1B;

[0020] [Fig. 3] is an electrical diagram equivalent to the switch of Figures 1A and 1B;

[0021] [Fig.4] is a schematic and partial top view of an example of a line at mid croruban comprising the switch of figures 1A and 1B according to one embodiment;

[0022] [Fig. 5] is a schematic and partial top view of an example of a coplanar line comprising the switch of Figures 1A and 1B according to one embodiment;

[0023] [Fig.6] is a schematic and partial top view of an example of a switch based on a phase change material according to one embodiment; and

[0024] [Fig.7] is a schematic and partial top view of an example of a switch based on a phase change material according to one embodiment. Description of the embodiments

[0025] The same elements have been designated by the same references in the different figures. In particular, the structural and / or functional elements common to the different embodiments may have the same references and may have identical structural, dimensional and material properties.

[0026] 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 the switches based on a phase-change material and the applications in which such switches may be provided have not been detailed, the described embodiments and variants being compatible with the control circuits of the usual phase-change material switches and with the usual applications implementing switches based on a phase-change material.

[0027] Unless otherwise specified, when referring to two elements connected to each other, this means directly connected without intermediate elements other than conductors, and when referring to two elements connected (in English "coupled") to each other, this means that these two elements can be connected or be connected by means of one or more other elements.

[0028] In the following description, when reference is made to absolute position qualifiers, such as the terms "front", "back", "top", "bottom", "left", "right", etc., or relative position qualifiers, such as the terms "above", "below", "upper", "lower", etc., or to orientation qualifiers, such as the terms "horizontal", "vertical", etc., reference is made, unless otherwise specified, to the orientation of the figures.

[0029] Unless otherwise specified, the expressions “about”, “approximately”, “substantially”, and “of the order of” mean to within 10%, preferably to within 5%.

[0030] [Fig.lA] and [Fig.lB] are schematic and partial views, respectively from above and in section along plane AA of [Fig.lA], of an example of a switch 100 based on a phase change material according to one embodiment.

[0031] In the example shown, the switch 100 comprises coplanar electrodes 101a, 101b, 101c and 101b. The electrodes 101a and 101c are located on either side of the electrode 101b. In the orientation of [Fig.lA], the electrodes 101a and 101c are located at the left and right ends, respectively, of the switch 100. Electrode 101b is interposed laterally between electrodes 101a and 101c. Electrode 101b is located opposite electrode 101b. In the orientation of [Fig.1A], electrode 101b is located at the lower end of switch 100.

[0032] The electrodes 101a and 101c are for example intended to be connected to a radiofrequency communication circuit, not detailed. The electrode 101b is for example an intermediate electrode, or central electrode. The electrode 101b is for example a reference electrode intended to be brought to a reference potential, for example ground.

[0033] By way of example, the electrodes 101a, 101b, 101c and 101b are made of a conductive material, for example a metal or a metal alloy. Each electrode 101a, 101b, 101c, 101b may have a single-layer or multi-layer structure. In order to simplify the production of the switch 100, the electrodes 101a, 101b, 101c and 101b may have, for example, structures and compositions that are substantially identical, apart from manufacturing variations. By way of example, each electrode 101a, 101b, 101c, 101b has, in top view, a periphery of substantially rectangular shape. This example is not, however, limiting, each electrode 101a, 101b, 101c, 101b may have any shape.

[0034] Although this has not been detailed, the electrodes 101a, 101b, 101c and 101d of the switch 100 are for example located on and in contact with one face of an insulating layer, for example made of silicon dioxide, coating a substrate, for example a wafer or a piece of wafer made of a semiconductor material, for example silicon.

[0035] In the example shown, an electrically insulating layer 103 covers the lateral faces of the electrodes 101a, 101b, 101c and 101b and fills the free spaces extending laterally between the electrodes 101a, 101b, 101c and 101b. The layer 103, not shown in [Fig. 1A] so as not to overload the drawing, electrically insulates the electrodes 101a, 101b, 101c and 101b from each other. In the example shown, the insulating layer 103 is flush with the upper face of the electrodes 101a, 101b, 101c and 101b. For example, the insulating layer 103 is made of silicon dioxide.

[0036] In the example shown, the switch 100 further comprises regions 105a, 105b and 105c made of a phase change material. The regions 105a, 105b and 105c are disjoint and each connect two adjacent electrodes of the switch 100. More specifically, in the example shown, the region 105a connects the electrodes 101a and 101b, the region 105b connects the electrodes 101b and 101c, and the region 105c connects the electrodes 101b and 101c. In other words, the electrode 101b is connected to each of the other electrodes 101a, 101c and 101c by the regions of phase change material 105a, 105b and 105c, respectively. Each region 105a, 105b, 105c of phase change material covers the upper face of a portion of the layer 103 extending laterally. between the two adjacent electrodes that it connects, and extends over and in contact with a portion of the upper face of each of said electrodes. Each region 105a, 105b, 105c made of phase-change material has, for example, in top view, a periphery of substantially rectangular shape. This example is however not limiting, each region 105a, 105b, 105c being able to have any shape.

[0037] The switch 100 has, in the orientation of [Fig. 1A], a general T-shape whose horizontal bar, parallel to a conduction direction of the switch 100, comprises the electrodes 101a, 101b and 101c and the regions of phase change material 105a and 105b, and whose vertical bar, extending along a direction orthogonal to the conduction direction of the switch 100, comprises the electrodes 101b and 101b and the region of phase change material 105c.This example is not, however, limiting, the switch 100 being able to have any shape. The conduction direction of the switch 100 and the direction in which the electrode 100 and the region 105c extend can for example be oblique.

[0038] By way of example, each region 105a, 105b, 105c of the switch 100 is made of a so-called “chalcogenide” material, that is to say a material or an alloy comprising at least one chalcogen element, for example a material from the family of germanium telluride, antimony telluride or germanium-antimony-tellurium, more commonly designated by the acronym “GST”. As a variant, at least one of the regions 105a, 105b, 105c may be made of vanadium dioxide.

[0039] The region 105c of the switch 100 is for example dimensioned differently from the regions 105a and 105b. For example, the region 105c has a volume, or an active surface, different from the volume, or the active surfaces, of each of the regions 105a and 105b. As a variant, or in a complementary manner, the region 105c may be made of a phase change material different from that of the regions 105a and 105b.

[0040] In the orientation of [Fig.lB], the upper face of each region 105a, 105b, 105c is coated with an electrically insulating layer 107. For example, the insulating layer 107 is made of a dielectric and thermally conductive material, for example silicon nitride or aluminum nitride. The insulating layer 107 has not been shown in [Fig.lA] so as not to overload the drawing.

[0041] In the illustrated example, the switch 100 further comprises heating elements 109a, 109b and 109c located on and in contact with the upper face of the layer 107 directly above the regions 105a, 105b and 105c, respectively. In this example, each heating element 109a, 109b, 109c is electrically insulated from the underlying region 105a, 105b, 105c by the layer 107. In the example shown, the heating elements 109a and 109b each have the shape of a rectangular strip extending along a direction substantially orthogonal to the direction of conduction of the switch 100, and the heating element 109c has the shape of a rectangular strip extending along a direction substantially parallel to the conduction direction of the switch 100.

[0042] In the example illustrated in [Fig.lA], the heating elements 109a and 109b are connected in series between control electrodes 111-1 and 111-2 located on either side of the electrode 101b. In this example, the heating elements 109a and 109b are part of the same conductive track 113, for example a metal track, the left and right ends of which are respectively connected to the control electrodes 111-1 and 111-2. A part of the track 113 connecting the heating element 109a to the heating element 109b is located directly above a region devoid of phase change material, for example an electrically insulating region. In the illustrated example, the heating elements 109a and 109b are intended to be controlled simultaneously, for example by applying a potential difference between the electrodes 111-1 and 111-2.

[0043] As a variant, the heating elements 109a and 109b may be electrically isolated from each other. In this case, the heating elements 109a and 109b are, for example, formed in separate conductive tracks, isolated from each other and each connected between control electrodes similar to the electrodes 111-1 and 111-2. In this case, the control electrodes of each heating element 109a, 109b are, for example, located on either side of the conduction direction of the switch 100. The heating elements 109a and 109b may, in this variant, be controlled simultaneously, for example by the simultaneous application of a potential difference between the control electrodes of each heating element 109a, 109b.

[0044] In the example shown, the heating element 109c is connected between control electrodes 115-1 and 115-2 and is part of a conductive track 117, for example a metal track, the left and right ends of which are respectively connected to the control electrodes 115-1 and 115-2 of the heating element 109c. In this example, the track 117 of which the heating element 109c is part is electrically insulated from the track 113 of which the heating elements 109a and 109b are part, and the control electrodes 115-1 and 115-2 are electrically insulated from the control electrodes 111-1 and 111-2. This makes it possible to control the heating element 109c independently of the heating elements 109a and 109b.

[0045] By way of example, the control electrodes 111-1 and 111-2 of the heating elements 109a and 109b of the switch 100 are connected or linked to a first control circuit, and the control electrodes 115-1 and 115-2 of the heating element 109c are connected or linked to a second control circuit, for example separate from the first control circuit. In order not to overload the drawing, the control circuits of the heating elements 109a, 109b and 109c have not been shown.

[0046] Each heating element 109a, 109b, 109c has, for example, a thickness of the order of 100 nm and a width of between a few hundred nanometers and a few micrometers. For example, each heating element 109a, 109b, 109c is made of a metal, for example tungsten, or a metal alloy, for example titanium nitride. Although this has not been shown, the switch 100 may be coated with a thermally insulating layer intended to confine the heat produced by the heating elements 109a, 109b and 109c.

[0047] [Fig.2A], [Fig.2B] and [Fig.2C] are schematic and partial top views illustrating different states of the switch of Figures 1A and 1B.

[0048] 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 an electrical resistivity greater than that of the crystalline phase. In the case of the switch 100, this phenomenon is taken advantage of to obtain: - a first state ([Fig.2A]), called “on state”, allowing the circulation of a current between the electrodes 101a, 101b and 101c, when the material of the regions 105a and 105b is in the crystalline phase and when at least part of the material of the region 105c is in the amorphous phase; - a second state ([Fig.2B]), called “reflective blocked state”, preventing the flow of a current between the electrodes 101a and 101c, when at least part of the material of the regions 105a and 105b is in the amorphous phase and when the material of the region 105c is in the crystalline phase; and - a third state ([Fig.2C]), called “absorbing blocked state”, allowing the circulation of a current between the electrodes 101a, 101b and 101c, and possibly between the electrodes 101a, 101b and 101c, when the material of the regions 105a, 105b and 105c is in the crystalline phase.

[0049] When the switch 100 switches between the on and off reflective states, the control electrodes 111-1 and 111-2 of the heating elements 109a and 109b and the control electrodes 115-1 and 115-2 of the heating element 109c are for example simultaneously subjected to control voltages causing a flow of current through the heating elements 109a, 109b and 109c. This current causes, by Joule effect then by radiation and / or conduction inside the structure of the switch 100, in particular through the layers 107, a rise in temperature of the underlying regions 105a, 105b and 105c from their upper faces, located opposite the respective heating elements 109a, 109b and 109c.

[0050] More precisely, to switch the switch 100 from the blocked state refe- in the on state, the regions 105a and 105b made of phase change material are heated, by means of the heating elements 109a and 109b, for example to a temperature Tl and for a duration dl. The temperature Tl and the duration dl are chosen so as to cause a phase change of the material of the regions 105a and 105b from the amorphous phase to the crystalline phase. The temperature Tl is for example higher than a crystallization temperature and lower than a melting temperature of the material of the regions 105a and 105b. For example, the temperature Tl is between 150 and 350 °C and the duration dl is less than 1 ps. In the case where regions 105a and 105b are made of germanium telluride, the temperature Tl is for example equal to approximately 300 °C and the duration dl is for example between 100 ns and 1 ps.

[0051] Furthermore, the region 105c made of phase change material is heated, by means of the heating element 109c, for example to a temperature T2 higher than the temperature T1, and for a duration d2 lower than the duration d1. The temperature T2 and the duration d2 are chosen so as to cause a phase change of the material of the region 105c from the crystalline phase to the amorphous phase. The temperature T2 is for example higher than the melting temperature of the phase change material. For example, the temperature T2 is between 600 and 1000°C and the duration d2 is less than 500 ns. In the case where the region 105c is made of germanium telluride, the temperature T2 is for example equal to approximately 700°C and the duration d2 is for example equal to approximately 100 ns.

[0052] When switching the switch 100 between the reflective blocked state and the conducting state, the heating element 105c and the heating elements 105a and 105b are for example controlled simultaneously. This advantageously makes it possible to reduce the switching time.

[0053] Conversely, to switch the switch 100 from the on state to the reflective off state, the regions 105a and 105b are heated, by means of the heating elements 109a and 109b, for example to the temperature T2 and for the duration d2. Furthermore, the region 105c is heated, by means of the heating element 109c, for example to the temperature T1 and for the duration d1.

[0054] The switching between the reflective off and absorbent off states is for example analogous to the switching between the conducting and reflective off states described above, with the difference that only the heating elements 109a and 109b are implemented for the switching between the reflective off and absorbent off states, the material of the region 105c remaining in the crystalline phase during this switching. For example, to switch the switch 100 from the reflective off state to the absorbent off state, the regions 105a and 105b are heated to the temperature T1 and for the duration d1. Conversely ... mutator 100 from the absorbing blocked state to the reflecting blocked state, the regions 105a and 105b are for example heated to the temperature T2 and for the duration d2.

[0055] Furthermore, the switching between the on and off absorbing states is for example analogous to the switching between the on and off reflecting states described above, with the difference that only the heating element 105c is implemented for the switching between the on state and the off absorbing state, the material of the regions 105a and 105b remaining in the crystalline phase during this switching. For example, to switch the switch 100 from the on state to the off absorbing state, the region 105c is heated to the temperature T1 and for the duration d1. Conversely, to switch the switch 100 from the off absorbing state to the on state, the region 105c is for example heated to the temperature T2 and for the duration d2.

[0056] The values of the temperatures T1 and T2 and of the heating durations d1 and d2 may be identical for each of the regions 105a, 105b, 105c. As a variant, at least one of the regions 105a, 105b, 105c, for example the region 105c, may have values of temperature T1 and / or T2 and / or of heating duration d1 and / or d2 different from those of the other regions (the regions 105a and 105b, in this example).

[0057] The switch 100 is said to be “indirectly heated”, the temperature rise of the phase change material being obtained by circulation of a current through a heating element electrically insulated from the phase change material, as opposed to “directly heated” type switches which are devoid of a heating element and in which the temperature rise results from a circulation of current through the phase change material. In the case of a directly heated switch, the control electrodes are for example connected to two opposite sides of the region of phase change material, for example along a direction orthogonal to the conduction path of the switch.A disadvantage of directly heated switches is that when the switch is on, an electrical conduction path is created through the phase change material between the control electrodes and the conduction electrodes of the switch. This results in leakage currents that disrupt the signal transmitted between the conduction electrodes.

[0058] An advantage of the switch 100 is that the reflective blocked state makes it possible to obtain better isolation, for example improved by approximately -20 dB, between the electrodes 101a and 101c compared to the case of a similar switch but comprising a single region of phase-change material connecting two conduction electrodes. Another advantage of the switch 100 lies in the fact that it is possible to take advantage of the absorbing blocked state to attenuate the signal transmitted between the conduction electrodes 101a and 101c.

[0059] [Fig. 3] is an electrical diagram equivalent to the switch 100 of Figures 1A and 1B.

[0060] In the example shown: - the phase change material region 105a is symbolized by a resistive element Ra and a capacitive element Ca associated in parallel between the electrodes 101a and 101b; - the phase change material region 105b is symbolized by a resistive element Rb and a capacitive element Cb associated in parallel between the electrodes 101b and 101c; and - the phase change material region 105c is symbolized by a resistive element Rc and a capacitive element Ce associated in parallel between the electrodes 101b and 101c.

[0061] The resistive elements Ra, Rb and Rc symbolize the electrical resistance of the phase change material regions 105a, 105b and 105c of the switch 100. The resistance of each resistive element Ra, Rb and Rc varies depending on whether the corresponding region 105a, 105b, 105c is in the crystalline state or in the amorphous state. More precisely, the resistance of each resistive element Ra, Rb, Rc can for example take: - a first value Ra_on, Rb_on, Rc_on corresponding to the resistance of the resistive element Ra, Rb, Rc when the corresponding phase change material region 105a, 105b, 105c is in the crystalline state; and - a second value Ra_off, Rb_off, Rc_off greater than the first value Ra_on, Rb_on, Rc_on and corresponding to the resistance of the resistive element Ra, Rb, Rc when the corresponding phase change material region 105a, 105b, 105c is at least partially in the amorphous state.

[0062] For example, in a case where the regions of phase change material 105a, 105b and 105c are made of germanium telluride, the ratios Ra_off / Ra_on, Rb_off / Rb_on, Rc_off / Rc_on are of the order of 105. In this case, the volume of each region 105a, 105b, 105c is for example dimensioned so that the values Ra_on, Rb_on and Rc_on are substantially equal, and the values Ra_off, Rb_off and Rc_off are substantially equal.

[0063] As a variant, in a case where the regions of phase change material 105a, 105b and 105c are in GST, the ratios Ra_off / Ra_on, Rb_off / Rb_on, Rc_off / Rc_on are for example of the order of 102, that is to say much lower than the ratios obtained in the example where the regions 105a, 105b and 105c are in germanium telluride. In this case, the volume of each region 105a, 105b, 105c is for example dimensioned so that the value Rc_on is for example 10 to 50 times greater than each value Ra_on, Rb_on, and the value Rc_off is for example 10 to 50 times greater than each value Ra_off, Rb_off. The region 105c then has by for example, a volume smaller than that of regions 105a and 105b. This compensates for the fact that the ratios Ra_off / Ra_on, Rb_off / Rb_on, Rc_off / Rc_on are in this case less important than in the case where regions 105a, 105b and 105c are in germanium telluride. For example, in the case where regions 105a, 105b and 105c are in GST: - the values Ra_on and Rb_on are between 0.5 and 5 Q, for example equal to approximately 1 Q; - the Ra_off and Rb_off values are between 50 and 500 Q, for example equal to approximately 100 Q; - the Rc_on value is between 5 and 250 Q, for example equal to approximately 20 Q; and - the Rc_off value is between 500 and 25,000 Q, for example equal to approximately 2,000 Q.

[0064] The presence of the capacitive elements Ca, Cb and Ce is due to the fact that the regions of phase change material 105a, 105b and 105c are separated from the heating elements 109a, 109b and 109c, respectively, by the insulating layer 107. For example, each capacitive element Ca, Cb, Ce has, when the corresponding region 105a, 105b, 105c is in the amorphous phase, a capacitance of the order of 10 fF.

[0065] Furthermore, in the example shown, the conductive track 113, in which the heating elements 109a and 109b are formed, is symbolized by a resistive element RI connected between the control electrodes 111-1 and 111-2, and the conductive track 117, in which the heating element 109c is formed, is symbolized by a resistive element R2 connected between the control electrodes 115-1 and 115-2.

[0066] [Fig. 4] is a schematic and partial top view of an example of a microstrip line 300 comprising the switch 100 of FIGS. 1A and 1B according to one embodiment.

[0067] In the example shown, the switch 100 is located directly above a ground plane 301. The electrode 101 of the switch 100 is connected to the underlying ground plane 301 by a conductive via 303, for example a metal via.

[0068] The implementation of the switch 100 in the microstrip line 300 makes it possible to obtain greater isolation than that which would be obtained with a switch lacking the region 105c, the electrode 101c and the via 303, for example a switch comprising only a single region of phase-change material connecting the electrodes 101a and 101c.

[0069] [Fig. 5] is a schematic and partial top view of an example of a coplanar waveguide 400 (CPW) comprising the switch 100 of FIGS. 1A and 1B according to one embodiment.

[0070] In the example shown, the switch 100 is interposed laterally between two ground planes 401 and 403. The ground planes 401 and 403 and the electrodes 101a, 101b, 101c and lOld of the switch 100 are for example coplanar. In the illustrated example, the electrode lOld of the switch 100 is connected to the ground plane 401.

[0071] The implementation of the switch 100 in the coplanar line 400 makes it possible to obtain greater isolation than that which would be obtained with a switch lacking the region 105c, the electrode lOld and the via 303, for example a switch comprising only a single region of phase change material connecting the electrodes 101a and 101c.

[0072] [Fig.6] is a schematic and partial top view of an example of a switch 500 based on a phase change material according to one embodiment.

[0073] The switch 500 of [Fig. 6] comprises elements common with the switch 100 of figures 1A and 1B. These common elements will not be detailed again below.

[0074] The switch 500 of [Fig. 6] differs from the switch 100 of FIGS. 1A and 1B in that the switch 500 of [Fig. 6] comprises a plurality of intermediate electrodes 501b (three intermediate electrodes 501b-1, 501b-2 and 501b-3, in the example shown) interposed laterally between the electrodes 101a and 101c. Each electrode 501b is for example analogous or identical to the electrode 101b of the switch 100. In the example shown, the switch 500 comprises regions 505a, 505b-1, 505b-2 and 505b-3 made of phase change material. Region 505a connects electrodes 101a and 501b-1, region 505b-1 connects electrodes 501b-1 and 501b-2, region 505b-2 connects electrodes 501b-2 and 501b-3, and region 505b-3 connects electrodes 501b-3 and 101c. Each region 505a, 505b-1, 505b-2, 505b-3 is, for example, analogous or identical to regions 105a and 105b of switch 100.

[0075] In the example shown, the switch 500 further comprises a plurality of electrodes 501d (three electrodes 501d-1, 501d-2 and 501d-3, in the example shown) located respectively opposite the electrodes 501b. Each electrode 501d is for example analogous or identical to the electrode 101d of the switch 100. In the example shown, the switch 500 further comprises regions 505c-1, 505c-2 and 505c-3 made of phase-change material. Region 505c-1 connects electrodes 501b-l and 501d-l, region 505c-2 connects electrodes 501b-2 and 501d-2, and region 505c-3 connects electrodes 501b-3 and 501d-3. Each region 505c-l, 505c-2, 505c-3 is for example analogous or identical to regions 105c of switch 100.

[0076] In the example illustrated in [Fig. 6], the switch 500 further comprises heating elements 509a, 509b-1, 509b-2 and 509b-3 located respectively in line with the regions 505a, 505b-1, 505b-2 and 505b-3 made of phase change material. Each heating element 509a, 509b-1, 509b-2, 509b-3 is connected between control electrodes 511-1 and 511-2 located on either side of the direction of conduction. In this example, each heating element 509a, 509b-1, 509b-2, 509b-3 is part of a conductive track 513, for example a metal track, the upper and lower ends of which are connected respectively to the control electrodes 511-1 and 511-2. The heating elements 509a, 509b-1, 509b-2 and 509b-3 are for example intended to be controlled simultaneously.

[0077] In the example shown, the heating elements 509a, 509b-1, 509b-2 and 509b-3 are insulated from each other. Alternatively, the heating elements 509a, 509b-1, 509b-2 and 509b-3 may be connected, for example by means of a conductive track interconnecting the electrodes 511-1 of the heating elements 509a, 509b-1, 509b-2 and 509b-3.

[0078] In the illustrated example, the switch 500 further comprises heating elements 509c (three heating elements 509c-1, 509c-2 and 509c-3, in the example shown) connected in series between control electrodes 515-1 and 515-2 and forming part of the same conductive track 517, for example a metal track, the left and right ends of which are connected respectively to the control electrodes 515-1 and 515-2. The heating elements 509c-1, 509c-2 and 509c-3 are intended to be controlled simultaneously, for example by applying a potential difference between the electrodes 515-1 and 515-2.

[0079] Alternatively, the heating elements 509c-1, 509c-2 and 509c-3 may be electrically isolated from one another. In this case, the heating elements 509c-1, 509c-2 and 509c-3 are for example formed in separate conductive tracks, isolated from one another and each connected between control electrodes similar to the electrodes 515-1 and 515-2. In this case, the control electrodes of each heating element 509c-1, 509c-2, 509c-3 are for example parallel to the conduction direction of the switch 500. The heating elements 509c-1, 509c-2 and 509c-3 can, in this variant, be controlled simultaneously, for example by the simultaneous application of a potential difference between the control electrodes of each heating element 509c-1, 509c-2, 509c-3.

[0080] The heating elements 509c-1, 509c-2 and 509c-3 are electrically isolated from the heating elements 509a, 509b-1, 509b-2 and 509b-3. This allows the heating elements 509c-1, 509c-2 and 509c-3 to be controlled independently of the heating elements 509a, 509b-1, 509b-2 and 509b-3 as discussed above in relation to FIGS. 1A and 1B for the switch 100.

[0081] The operation of the switch 500 of [Fig. 6] is analogous to the operation of the switch 100 of FIGS. 1A to 1B. The person skilled in the art is able, from the indications of the present description, to control the heating elements 509a, 509b-1, 509b-2, 509b-3, 509c-1, 509c-2 and 509c-3 of the switch 500 to obtain on, off reflective and off absorbing states analogous to those pre previously described in connection with Figures 1A and 1B for the switch 100. The switch 500 has advantages similar or identical to those of the switch 100.

[0082] The fact of providing several regions 505a, 505b-1, 505b-2 and 505b-3 made of phase-change material advantageously makes it possible to reduce the quantity of electrical energy and the duration required for each switching while making it possible, in the off state, to achieve a high voltage resistance, for example greater than or equal to 4 V, between the electrodes 101a and 101c of the switch 500. The switch 500 thus has, compared to the switch 100, a higher switching speed, lower energy consumption and higher reliability.

[0083] [Fig.7] is a schematic and partial top view of an example of a com mutator 600 based on a phase change material according to one embodiment.

[0084] The switch 600 of [Fig.7] comprises elements in common with the switch 500 of [Fig.6]. These common elements will not be detailed again below.

[0085] The switch 600 of [Fig. 7] differs from the switch 500 of [Fig. 6] in that the phase change material regions 505a, 505b-1, 505b-2 and 505b-3 of the switch 600 have, in top view, different areas. In the illustrated example, the regions 505a, 505b-1, 505b-2 and 505b-3 have, along the conduction direction of the switch 600, from the electrode 101a towards the electrode 101c, strictly increasing areas. In the example shown, the regions 505a, 505b-1, 505b-2 and 505b-3 made of phase-change material have the same length, apart from manufacturing dispersions, and different widths, for example strictly increasing between the two electrodes 101a and 101c of the switch 600.For example, the electrode 101c in contact with the region 505b-3 having the largest area is adapted to be brought to a high potential, for example greater than or equal to 4 V, the other electrode 101a, in contact with the region 505a having the smallest area, in this example, being intended to be brought to a reference potential, for example ground. Furthermore, the difference in areas, or widths, between two successive regions 505a, 505b-1, 505b-2, 505b-3 is all the greater as the regions 505a, 505b-1, 505b-2 and 505b-3 are close to the electrode 101c in contact with the region 505b-3 having the largest area (close to the right end, in the orientation of [Fig.7]).

[0086] The width, or area, of each region 505a, 505b-1, 505b-2, 505b-3 is for example determined so that, when the switch 600 is in the off state and a voltage, resulting from the application of the radiofrequency signal, is applied between its electrodes 101a and 101c, the resulting voltages individually applied to each region 505a, 505b-l, 505b-2, 505b-3, that is to say, for each region 505a, 505b-l, 505b-2, 505b-3, the voltage applied between the two electrodes that it connects, are substantially identical, or balanced. This advantageously makes it possible to improve the voltage resistance of the switch 600 compared to the switch 500.

[0087] Various embodiments and variations have been described. Those skilled in the art will understand that certain features of these various embodiments and variations could be combined, and other variations will occur to those skilled in the art. In particular, those skilled in the art are able, in the microstrip line 300 or in the coplanar line 400, to replace the switch 100 with the switch 500 or with the switch 600.

[0088] Finally, the practical implementation of the embodiments and variants described is within the reach of the person skilled in the art from the functional indications given above. In particular, the person skilled in the art is capable, from the indications of the present description, of choosing the material and of dimensioning the volume of each region of phase change material according to the desired electrical characteristics.

Claims

Claims

1. Switch (100; 500; 600) comprising: - first, second, third and fourth electrodes (101a, 101b, 101c, lOld; 101a, 501b-l, 501b-2, 501d-l); - a first region (105a; 505a) made of a phase change material connecting the first and second electrodes; - a second region (105b; 505b-l) made of a phase change material connecting the second and third electrodes; and - a third region (105c; 505c-1) made of a phase change material connecting the second and fourth electrodes, wherein the fourth electrode (lOld) is intended to be brought to a reference potential, preferably ground.

2. A switch according to claim 1, further comprising first, second and third heating elements (109a, 109b, 109c; 509a, 509b-1, 509c-1) located respectively opposite the first, second and third regions (105a, 105b, 105c; 505a, 505b-1, 505c-1) of phase change material, each heating element being electrically insulated from said facing region.

3. A switch according to claim 2, wherein the third heating element (109c; 509c-1) is intended to be controlled independently of the first and second heating elements (109a, 109b; 509a, 509b-1).

4. A switch according to claim 2 or 3, wherein the first and second heating elements (109a, 109b; 509a, 509b-l) are intended to be controlled simultaneously.

5. A switch according to any one of claims 2 to 4, wherein the first and second heating elements (109a, 109b; 509a, 509b-1) are connected in series between two control electrodes (111-1, 111-2).

6. A switch according to any one of claims 1 to 5, wherein the first, second and third regions (105a, 105b, 105c; 505a, 505b-l, 505c-l) of phase change material are of a chalcogenide material.

7. The switch of claim 6, wherein each of the first, second, and third regions (105a, 105b, 105c; 505a, 505b-1, 505c-1) of phase change material is germanium telluride or germanium-antimony-tellurium.

8. A switch according to any one of claims 1 to 7, wherein the third region (105c; 505c-1) of phase change material has a smaller volume than the first and second regions (105a, 105b; 505a, 505b-1) of phase change material.

9. A switch (600) according to any one of claims 1 to 8, wherein the first and second regions (505a, 505b-l) of phase change material have, in top view, different areas.

10. Switch according to any one of claims 1 to 9, in which the first and second regions (105a, 105b; 505a, 505b-l) of phase change material have, along the conduction direction of the switch, the same lateral dimension.

11. A switch (600) according to any one of claims 1 to 10, wherein the first and second regions (505a, 505b-l) of phase change material have, along a direction orthogonal to the conduction direction of the switch, different lateral dimensions.

12. Device (300; 400) comprising a switch (100; 500; 600) according to any one of claims 1 to 11 and a ground plane (301; 401) to which the fourth electrode (101d; 501d-1) of the switch is connected.

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