CN117425394A

CN117425394A - Phase change material based switch

Info

Publication number: CN117425394A
Application number: CN202310638920.5A
Authority: CN
Inventors: S·蒙弗莱; A·弗勒雷; B·雷格
Original assignee: STMicroelectronics Crolles 2 SAS; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Current assignee: STMicroelectronics Crolles 2 SAS; Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Priority date: 2022-07-18
Filing date: 2023-06-01
Publication date: 2024-01-19
Also published as: CN220325606U

Abstract

The present description relates to a phase change material based switch comprising: a phase change material region; a heating element electrically insulated from the phase change material region; and one or more pillars extending in the phase change material region, the pillars being made of a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

Description

Phase change material based switch

Cross Reference to Related Applications

The present application claims the benefit of priority of french patent application No. 2207296 (for 21-GR4-0974US 01)/2207297 (for 22-GR4-0006US 01)/2207298 (for 21-GR4-0951US 01) filed on month 18 2022, entitled "Commutateur-base de mat meriau changement de phase", which is incorporated herein by reference to the maximum extent allowed by law.

Technical Field

The present disclosure relates generally to electronic devices. The present disclosure more particularly relates to switches based on phase change materials that are capable of alternating between a conductive crystalline phase and an electrically insulating amorphous phase.

Background

Many applications are known that utilize phase change material based switches or interrupters to allow or prevent current flow in all or part of the circuit. Such a switch may be particularly implemented in radio frequency communication applications, for example, to switch an antenna between a transmit mode and a receive mode, to activate filters corresponding to frequency bands, and the like.

Disclosure of Invention

There is a need to improve existing phase change material based switches and methods of making the same.

One embodiment overcomes all or part of the shortcomings of known phase change material based switches and methods of making the same.

An aspect of one embodiment is more particularly directed to a switch having improved thermal efficiency.

An aspect of another embodiment is more particularly directed to a switch having a reduced size.

An aspect of yet another embodiment is more particularly directed to a switch with enhanced switching speed.

To this end, one embodiment provides a phase change material based switch comprising:

a region made of the phase change material;

an electrical heating element insulated from the phase change material region; and

one or more pillars extending in the phase change material region, the pillars being made of a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

According to one embodiment, the material of the pillars is electrically insulating.

According to one embodiment, the material of the pillars is selected from aluminum nitride or silicon nitride.

According to one embodiment, the phase change material is a chalcogenide material.

According to an embodiment, an electrically insulating layer is interposed between the heating element and the phase change material region.

According to one embodiment, the electrically insulating layer is made of the same material as the pillars.

According to one embodiment, the phase change material region is closer to the substrate than the heating element, and the switch is formed inside and on top of the substrate.

According to one embodiment, the heating element is closer to the substrate than the phase change material region, and the switch is formed inside and on top of the substrate.

According to one embodiment, the phase change material region is covered with a passivation layer.

According to one embodiment, the phase change material region couples the first and second conductive electrodes of the switch.

According to one embodiment, each pillar has a maximum lateral dimension equal to about 300 nm.

According to one embodiment, each pillar is separated from an adjacent pillar by a distance of about 300 nm.

Furthermore, one embodiment provides a phase change material based switch comprising:

a phase change material region coupling the first conductive electrode and the second conductive electrode of the switch;

one or more islands made of electrically insulating material, each island having a first surface extending over and in contact with the first and second electrodes, wherein the phase change material region extends on a side of each island and a second surface opposite the first surface.

According to one embodiment, the side of each island is substantially parallel to the conduction direction of the switch.

According to one embodiment, the switch comprises a single island made of said electrically insulating material.

According to one embodiment, the switch comprises a plurality of islands made of said electrically insulating material.

According to one embodiment, the islands are distributed at regular intervals along the heating element.

According to one embodiment, the electrically insulating material is aluminum nitride.

According to one embodiment, an electrically insulating layer between the phase change material region and the heating element covers all sides of each island.

According to one embodiment, the phase change material region covers all sides of each island.

According to one embodiment, an electrically insulating layer interposed between the phase change material region and the heating element covers the upper surface and the sides of the phase change material region.

According to one embodiment, each island has a trapezoidal cross section.

According to one embodiment, each island has a height equal to about 5 μm.

According to one embodiment, the switch further comprises one or more pillars extending in the phase change material region, the pillars being made of a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

One embodiment provides a method of forming a switch such as described, including the step of forming islands over and in contact with a portion of an upper surface of each control electrode.

a first region and a second region made of the phase change material, each region being connected to a first conductive electrode and a second conductive electrode of a switch, the second region being located above the first region; and

a heating element is located between and electrically insulated from the first and second regions of phase change material.

According to one embodiment, one of the first and second regions of the phase change material is located above and in contact with the first and second electrodes.

According to one embodiment, the further phase change material region is connected to the first electrode and the second electrode by a via.

According to one embodiment, the vias are in contact with the lower surface of the other phase change material region through their upper surfaces.

According to one embodiment, the further phase change material region is below the third electrode and the fourth electrode, and the third electrode and the fourth electrode are in contact.

According to one embodiment, the third electrode and the fourth electrode are connected to the first and second electrode, respectively, through vias.

According to one embodiment, the heating element is made of a metal or metal alloy.

According to one embodiment, the heating element is made of tungsten or titanium nitride.

According to one embodiment, the switch further comprises one or more pillars extending in the first region of the phase change material, the pillars being made of a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

According to one embodiment, the switch further comprises one or more pillars extending in the second region of the phase change material, the pillars being made of a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

One embodiment provides a method of manufacturing a switch such as described, comprising the following successive steps:

a) Depositing a first region of the phase change material;

b) Forming a heating element; and

c) A second region of the phase change material is deposited.

Drawings

The above and other features and advantages of the present disclosure will be discussed in detail in the following non-limiting description of specific embodiments in connection with the accompanying drawings, in which:

FIG. 1 is a simplified and partial perspective view of an example of a phase change material based switch;

FIG. 2 is a cross-sectional view of the switch of FIG. 1 along plane AA of FIG. 1;

FIG. 3 is a simplified and partial perspective view of an example of a phase change material based switch according to one embodiment;

fig. 4 is a cross-sectional view of the switch of fig. 3 along plane AA of fig. 3;

FIG. 5 is a simplified and partial perspective view of an example of a phase change material based switch according to one embodiment;

FIGS. 6A, 6B and 6C illustrate, in simplified and partial cross-sectional views, exemplary successive steps of a method of manufacturing the switch of FIG. 3, according to one embodiment;

FIG. 7 is a simplified and partial perspective view of an example of a phase change material based switch according to one embodiment;

FIG. 8 is a cross-sectional view of the switch of FIG. 7 along plane AA of FIG. 7;

FIG. 9 is a simplified and partial perspective view of an example of a phase change material based switch according to one embodiment;

FIG. 10 is a simplified and partial perspective view of an example of a phase change material based switch according to one embodiment;

FIG. 11 is a simplified and partial perspective view of an example of a phase change material based switch according to one embodiment;

FIGS. 12A and 12B illustrate, in simplified and partial cross-sectional views, exemplary sequential steps of a method of fabricating a phase change material based switch according to one embodiment;

13A, 13B, 13C, and 13D illustrate, in simplified and partial cross-sectional form, successive steps of an example of a method of manufacturing a phase change material-based switch according to one embodiment; and

fig. 14A and 14B illustrate, in simplified and partial cross-sectional form, successive steps of an example of a method of manufacturing a phase change material based switch according to one embodiment.

Detailed Description

Like features have been designated by like reference numerals throughout the various figures. In particular, structural and/or functional features common among the various embodiments may have the same reference numerals and may be arranged with the same structural, dimensional, and material properties.

For clarity, only the steps and elements that are helpful in understanding the embodiments described herein are illustrated and described in detail. In particular, the circuitry for controlling the phase change material based switch and the applications in which such a switch may be provided are not described in detail, the described embodiments and variations being compatible with conventional circuitry for controlling the phase change material based switch and with conventional applications implementing the phase change material based switch.

When referring to two elements being connected together, this means that there is no direct connection of any intermediate element other than a conductor, unless otherwise indicated; and when two elements are referred to as being coupled together, this means that the two elements can be connected or they can be coupled via one or more other elements.

In the following description, when referring to terms that define an absolute position (such as the terms "front", "rear", "top", "bottom", "left", "right", etc.) or a relative position (such as the terms "above", "below", "upper", "lower", etc.), or when referring to terms that define a direction (such as "horizontal", "vertical", etc.), unless otherwise specified, reference is made to the orientation of the drawings.

Unless otherwise specified, the expressions "about", "approximately", "substantially" and "approximately" mean plus or minus 10%, preferably plus or minus 5%.

Fig. 1 is a simplified and partial perspective view of an example of a phase change material based switch 100. Fig. 2 is a cross-sectional view of the switch 100 of fig. 1 along plane AA of fig. 1. Plane AA of fig. 1 is substantially parallel to the conduction direction of switch 100.

In the illustrated example, the switch 100 is formed inside and on top of a substrate 101 (e.g., a wafer or portion of a wafer made of semiconductor material). As an example, the substrate 101 is made of silicon and has a resistivity of about 100 Ω·m (silicon is referred to as having "high resistivity").

In this example, the substrate 101 is covered with an electrically insulating layer 103 on one of its surfaces (the upper surface of the substrate 101 in the orientation of fig. 2). As an example, layer 103 is made of silicon dioxide (SiO ₂ ) Made and has a thickness of about 500 nm.

In the example shown, the switch 100 includes a first conductive electrode 105a and a second conductive electrode 105b that are located over the electrically insulating layer 103 and in contact with an upper surface of the electrically insulating layer 103. The electrodes 105a and 105b are for example intended to be connected to radio frequency communication circuits (not shown in detail in the figures). Electrode 105a is separated from electrode 105b by a distance of, for example, about 1 μm. The electrodes 105a and 105b are made of a conductive material, such as a metal (e.g., copper or aluminum) or a metal alloy. Each electrode 105a, 105b may have a single-layer structure or a multi-layer structure, for example, including a titanium layer having a thickness of about 10nm, a layer of copper and aluminum alloy having a thickness of about 440nm, another titanium layer having a thickness of about 10nm, and a titanium nitride layer (TiN) having a thickness of about 100nm from the upper surface of the layer 103.

In this example, another electrically insulating layer 107 covers the portion of the upper surface of layer 103 that is not covered by electrodes 105a and 105b. In the example shown, the material of layer 107 surrounds electrodes 105a and 105b on all side surfaces of electrodes 105a and 105b. A portion of layer 107 specifically extends between electrodes 105a and 105b and electrically insulates electrode 105a from electrode 105b. Layer 107 is, for example, flush with the upper surfaces of electrodes 105a and 105b, as shown in fig. 2. By way of example, layer 107 is made of the same material as layer 103, such as silicon dioxide.

To avoid overloading the drawing, the substrate 101 and the electrically insulating layers 103 and 107 are not shown in fig. 1.

In the illustrated example, the switch 100 further includes a region 109 made of a phase change material, the region 109 coupling the first conductive electrode 105a and the second conductive electrode 105 b. More precisely, in this example, the region 109 covers the upper surface of the portion of the layer 107 separating the conductive electrodes 105a and 105b, and further extends over and in contact with a portion of the upper surface of each electrode 105a, 105b, for example, a distance exceeding about 1 μm. The region 109 has a thickness T, for example, in the range from 100nm to 300 nm.

As an example, the region 109 of the switch 100 is made of a material known as "chalcogenide", i.e. comprisesAt least one chalcogen material or alloy, for example, a material from the germanium telluride (GeTe), antimony telluride (SbTe) or germanium-antimony-tellurium (GeSbTe, commonly identified by the acronym "GST") family. As a variant, the region 109 is made of vanadium oxide (VO ₂ ) Is prepared.

In general, a phase change material is a material capable of alternating between a crystalline phase and an amorphous phase under the influence of a temperature change, the amorphous phase having a resistance greater than that of the crystalline phase. In the case of the switch 100, this phenomenon is exploited to obtain an off-state when at least a portion of the material of the region 109 located between the conductive electrodes is in an amorphous phase, preventing the flow of current between the conductive electrodes 105a and 105b, and an on-state when the material of the region 109 is in a crystalline phase, allowing the flow of current between the electrodes 105a and 105 b.

In the example shown, the upper surface of the region 109 is covered with an electrically insulating layer 111. As an example, the layer 111 is made of a dielectric and thermally conductive material, such as silicon nitride (SiN) or aluminum nitride (AlN).

In this example, switch 100 further includes a heating element 113, heating element 113 being located above and in contact with the upper surface of layer 111, in a vertical array with phase change material region 109. The heating element 113 is electrically insulated from the region 109 by the layer 111. In the example shown, the heating element 113 has a strip shape extending in a direction substantially perpendicular to the conduction direction of the switch 100. In this example, the ends of the heating element 113 are connected to the third control electrode 115a and the fourth control electrode 115b of the switch 100, respectively, by conductive pads 117. The heating element 113 has a thickness of about 100nm, for example. By way of example, the heating element 113 is made of a metal (e.g., tungsten) or a metal alloy (e.g., titanium nitride).

Although this is not illustrated in the drawings, the structure of the switch 100 may be covered with a heat insulating layer on the upper surface side of the substrate 101, the heat insulating layer being intended to limit the heat generated by the heating element 113.

During switching between the on-state and the off-state, the control electrodes 115a and 115b of the switch 100 are for example intended to be applied with a control voltage that causes a current to flow through the heating element 113. This current is passed through the joule effect and then through radiation and/or conduction inside the structure of the switch 100 (in particular through the layer 111) so that the area 109 situated in front of the heating element 113 rises in temperature from its upper surface.

More precisely, in order to switch the switch 100 from the off-state to the on-state, the region 109 is heated by the heating element 113, for example at a temperature T1 and for a duration d1. The temperature T1 and the duration d1 are selected to cause a phase change of the material of the region 109 from an amorphous phase to a crystalline phase. Temperature T1 is, for example, above the crystallization temperature of the material of region 109 and below the melting temperature. As an example, the temperature T1 is in the range from 150 ℃ to 350 ℃ and the duration d1 is shorter than 1 μs. In the case of region 109 made of germanium telluride, temperature T1 is for example equal to about 300 ℃, and duration d1 is for example in the range from 100ns to 1 μs.

Conversely, to switch the switch 100 from the on-state to the off-state, the region 109 is heated by the heating element 113, for example up to a temperature T2 higher than the temperature T1, and for a duration d2 shorter than the duration d1. The temperature T2 and the duration d2 are selected to cause a phase change of the material of the region 109 from a crystalline phase to an amorphous phase. The temperature T2 is for example above the melting temperature of the phase change material. As an example, the temperature T2 is in the range of 600 ℃ to 1000 ℃ and the duration d2 is shorter than 500ns. In the case of region 109 made of germanium telluride, temperature T2 is for example equal to about 700 ℃, and duration d2 is for example equal to about 100ns.

The switch 100 is referred to as "indirect heating", where the temperature rise of the phase change material is obtained by the flow of an electric current through an electric heating element insulated from the phase change material, in contrast to a "direct heating" type switch, which does not comprise a heating element, and where the temperature rise is caused by the direct flow of an electric current through the phase change material. In the case of a direct heating switch, the control electrodes are connected, for example, to two opposite sides of the phase change material region, for example, in a direction orthogonal to the conduction path of the switch. The disadvantage of a direct heating switch is the fact that: when the switch is turned on, a conductive path is created through the phase change material between the control electrode and the conductive electrode of the switch. This causes leakage currents that can interfere with the signal transmitted between the conductive electrodes.

In order to respond to constraints of various applications (e.g., in the field of radio frequency communications), it is desirable for the switch 100 to have a quality factor as low as possible. In the present disclosure, the quality factor of a switch corresponds to the on-state resistance R of the switch _ON And an off-state capacitance C _OFF Is a product of (a) and (b).

On-state resistance R of the switch of the present disclosure _ON Defined by the following relationship:

[ formula 1 ] ]

In the above related equation 1, L, W and T represent the length, width, and thickness, respectively, of the phase change material region 109, the lengths L and width W corresponding to the dimensions of the region 109 measured in directions parallel and orthogonal, respectively, to the conduction direction of the switch, and σ _ON Indicating the conductivity (in siemens per meter) of the phase change material when in its crystalline phase.

To reduce the quality factor of switch 100, the on-state resistance R of phase change material region 109 may be reduced, for example, by increasing its thickness T _ON . However, this may cause an undesirable increase in the switching duration, or a decrease in the switching speed between the on-state and the off-state. In fact, for the same control voltage, the thicker the region 109, the longer the durations d1 and d2, the durations d1 and d2 corresponding respectively to the duration of the transition between amorphous and crystalline phases and the duration of the transition between crystalline and amorphous phases. In order to reduce the duration d1 and d2, an attempt may be made to increase the control voltage of the heating element 113, but this may cause an undesired increase of the energy consumption of the switch 100.

Fig. 3 is a partial and simplified perspective view of an example of a phase change material based switch 300 according to one embodiment. Fig. 4 is a cross-sectional view of the switch 300 of fig. 3 along plane AA of fig. 3.

The switch 300 of fig. 3 and 4 includes elements common to the switch 100 of fig. 1 and 2. These common elements will not be described in detail hereinafter.

According to one embodiment, switch 300 includes one or more pillars 301 (in the example shown, tens of pillars 301) extending in phase change material region 109. More precisely, in the example illustrated in fig. 3 and 4, the pillars 301 extend vertically through the entire thickness T of the region 109.

According to one embodiment, pillars 301 are made of a material having a thermal conductivity greater than that of the phase change material of region 109. By way of example, the pillars 301 are made of an electrically insulating and thermally conductive material (e.g., silicon nitride, aluminum nitride, etc.). As a variant, the pillars 301 may be made of an electrically and thermally conductive material (e.g. metal). However, for the implementation of the switch 300 in radio frequency communication applications, it is preferable to use a column 301 made of an electrically insulating material to limit or avoid the occurrence of parasitic capacitance phenomena.

In the example shown, the pillars 301 each have a substantially circular cross-section in top view. However, this example is not limiting, and the pillars 301 may have any shape, such as rectangular or square cross-section. As an example, each pillar 301 has a maximum lateral dimension (e.g., diameter in the illustrated example where the pillar has a substantially circular cross-section) equal to about 300 nm. Furthermore, each pillar 301 is separated from adjacent pillars 301 by a distance of about 300nm, for example. The pillars 301 are distributed, for example, according to a periodic pattern. Although an example has been described in which the switch 300 includes tens of columns 301, the switch 300 may include any number of columns 301.

One advantage resulting from the presence of the pillars 301 is the fact that: the heat generated by the heating element 113 propagates more efficiently in the region 109 of the switch 300. In particular, compared to the switch 100 having the region 109 heated mainly from the upper surface of the region 109, the heat originating from the heating element 113 of the switch 300 is further spread in the center of the phase change material of the region 109. Accordingly, the switch 300 has a thermal efficiency greater than that of the switch 100.

In the case of switch 300, the heating element 113 experiences a lower temperature rise relative to switch 100 for the same control voltage applied between electrodes 115a and 115 b. Furthermore, for the same control voltage, region 109 of switch 300 experiences a higher temperature rise relative to region 109 of switch 100. In the case of switch 300, the difference between the temperatures reached by heating element 113 and region 109, respectively, during the switching step is lower than in the case of switch 100.

For a region 109 of similar thickness T, the switch 300 enables a shorter switching duration than the switch 100, or a greater switching speed than the switch 100. Advantageously, the increased thermal efficiency of the switch 300 may be utilized to increase the thickness T of the region 109 relative to the switch 100 to reduce the quality factor of the switch 300 without degrading the switching duration relative to the switch 100. The heating element 113 may also be advantageously pulled away from the region 109. This in turn causes an off-state capacitance C _OFF And thus the quality factor of the switch 300 is reduced relative to the switch 100.

As in the example shown, the upper surface of the region 109 of the switch 300 may be integrally covered with an electrically insulating layer 303. The optional layer 303, for example, enables passivation of the upper surface of the region 109. Layer 303 also enables the off-state capacitance C of switch 300 to be reduced relative to switch 100 _OFF And thus reduce the quality factor of the switch 300. In the example shown, pillars 301 span layer 303 across the entire thickness of layer 303. More precisely, in this example, each pillar 301 extends perpendicularly from the upper surface of layer 303 to the lower surface of region 109. Layer 303 has a thickness, for example, in the range from 200nm to 300 nm. As an example, layer 303 is made of silicon nitride or germanium nitride (GeN).

In the illustrated example, the switch 300 also optionally includes a separate electrically insulating region 305, the electrically insulating region 305 covering the upper surface of the electrically insulating layer 107 and extending over a portion of the upper surface of each conductive electrode 105a, 105 b. Each region 305 has a thickness of about 20nm, for example. By way of example, the electrically insulating region 305 is made of a dielectric material such as silicon nitride.

To avoid overloading the drawing, the substrate 101, the electrically insulating layers 103 and 107 and the electrically insulating region 305 are not shown in fig. 3.

In the example shown, the switch 300 further comprises an electrically insulating layer 307. Layer 307 of switch 300 is, for example, similar to layer 111 of switch 100. In switch 300, layer 307 is interposed between layer 303 and heating element 113. More precisely, in the example shown, layer 307 covers the upper surface of pillars 301, the upper surface and sides of layer 303, the sides of region 109, the exposed portions of electrodes 105a and 105b, and the upper surface and sides of region 305. By way of example, layer 307 is made of an electrically insulating and thermally conductive material, such as the same material as that of pillars 301, such as silicon nitride or aluminum nitride.

Although this is not illustrated in the drawings, the structure of the switch 300 may be covered with a heat insulating layer on the upper surface side of the substrate 101, which is intended to limit the heat generated by the heating element 113.

The switch 300 has a structure in which the heating element 113 is farther from the substrate 101 than the phase change material layer 109. This means a low heat capacity, the heating element 113 can be positioned close to the ambient air. This advantageously results in a fast heat exchange and thus in a low switching duration.

Fig. 5 is a simplified and partial cross-sectional view of an example of a phase change material based switch 500 according to one embodiment.

The switch 500 of fig. 5 includes elements common to the switch 300 of fig. 3 and 4. These common elements will not be described again hereinafter. In contrast to the switch 300 of fig. 3 and 4, wherein the phase change material region 109 is located below the heating element 113, in the orientation of fig. 5, the region 109 of the switch 500 is located above the heating element 113.

In the example shown, more precisely, the heating element 113 is located above and in contact with the upper surface of the electrically insulating layer 103. Further, in this example, the electrically insulating layer 307 covers the upper surface and sides of the heating element 113 and extends further over the portion of the upper surface of the layer 103 not covered by the heating element 113.

In the example illustrated in fig. 5, the phase change material region 109 intersecting the pillars 301 is located above the upper surface of the layer 307 and in contact with the upper surface of the layer 307, in a vertical column with the heating elements 113. In this example, the conductive electrodes 105a and 105b of the switch 500 are above and in contact with the upper surface of the layer 307. In addition, electrodes 105a and 105b each cover a portion of the sides and upper surface of region 109.

In the example shown, an electrically insulating layer 107 extends between the electrodes 105a and 105 b. In the orientation of fig. 5, layer 107 is above and in contact with the upper surface of region 109.

Although this is not illustrated in fig. 5, switch 500 may also include a passivation layer and an electrically insulating layer of region 109, the passivation layer and the electrically insulating layer of region 109 being similar to layer 303 and region 305, respectively, of switch 300 of fig. 3 and 4.

The switch 500 has a structure in which the heating element 113 is closer to the substrate 101 than the switch 300. In the case of switch 500, this means a higher heat capacity, which is advantageous for applying a lower control voltage on heating element 113 with respect to switch 300, to obtain a similar rise in temperature of region 109 during switching.

Fig. 6A-6C illustrate, in simplified and partial cross-sectional form, exemplary sequential steps of a method of manufacturing the switch 300 of fig. 3, according to one embodiment.

Fig. 6A more accurately illustrates a step of forming an electrically insulating layer 103 on an upper surface of the substrate 101, for example, by thermal oxidation of a material of the substrate 101. Fig. 6A also illustrates the step of forming conductive electrodes 105a and 105b on the upper surface of layer 103. As an example, a metallization layer is first deposited on the upper surface side of the substrate 101, for example by Physical Vapor Deposition (PVD) of one or more metal layers. The steps of photolithography and etching then enable only the portions of the metallization layer that are located at the desired locations of the electrodes 105a and 105b to remain. Radio frequency lines (not shown in fig. 6A) may be further formed in the first metallization layer during this step.

Fig. 6B illustrates a step of forming an electrically insulating layer 107 around the electrodes 105a and 105B. As an example, first, the layer 107 is deposited on the upper surface side of the structure of fig. 6A, for example by Plasma Enhanced Chemical Vapor Deposition (PECVD), more precisely by high density plasma enhanced chemical vapor deposition (HDPCVD or HDP PECVD). After deposition, layer 107 may cover electrodes 105a and 105b and may have a thickness of, for example, about 700 nm. Then, a planarization step, such as by chemical mechanical polishing, enables the upper surfaces of the electrodes 105a and 105b to be exposed. Layer 107 then has, for example, a thickness substantially equal to the thickness of electrodes 105a and 105 b.

Fig. 6B also illustrates the step of forming the electrically insulating region 305. As an example, an electrically insulating layer is first deposited on the upper surface side of the substrate 101. The steps of photolithography and etching then enable the portions of the electrically insulating layer at the desired locations of the regions 305 to remain. As a modification, the region 305 may be formed by local deposition of an electrically insulating material on the upper surface side of the substrate 101.

Fig. 6C illustrates a step of forming the phase change material region 109 and the passivation layer 303. As an example, a phase change material layer and a passivation layer are deposited consecutively on the upper surface side of the structure of fig. 6B, for example by physical vapor deposition. The steps of lithography and etching (e.g., by Reactive Ion Etching (RIE) or by Ion Beam Etching (IBE)) then enable only portions of the phase change material layer and passivation layer at the desired locations of regions 109 and layer 303 to remain. During these steps, openings 601 may be further formed in the phase change material layer and in the passivation layer at desired locations of pillars 301. As a variant, the opening 601 may be formed after a step of photolithography and etching following the step of forming the region 109 and the layer 303.

During another step, after the step described with respect to fig. 6C, the openings 601 are entirely filled to form pillars 301. An electrically insulating layer 307 is then deposited over the entire upper surface of the structure. In case pillars 301 and layer 307 are made of the same material, pillars 301 are formed, for example during deposition of layer 307. Then, a heating element 113 is formed over and in contact with the upper surface of layer 307. The control electrodes 115a and 115b and the pad 117 may also be formed during the step of forming the heating element 113, e.g. from the same metallization layer. At the end of these steps, the switch 300 of fig. 3 is obtained.

Those skilled in the art are able to adapt the method of manufacturing switch 300 described above with respect to fig. 6A-6C to form switch 500.

Fig. 7 is a partial and simplified perspective view of an example of a phase change material based switch 700 according to one embodiment. Fig. 8 is a cross-sectional view of the switch of fig. 7 along plane AA of fig. 7. Plane AA of fig. 7 is substantially parallel to the conduction direction of switch 700.

The switch 700 of fig. 7 and 8 includes elements common to the switch 100 of fig. 1 and 2. These common elements will not be described in detail hereinafter.

To avoid overloading the drawing, the substrate 101 and the electrically insulating layers 103 and 107 are not shown in fig. 7.

According to one embodiment, the switch 700 of fig. 7 and 8 includes one or more electrically insulating islands 701 (three islands 701 in the illustrated example), each electrically insulating island having a first surface (lower surface in the orientation of fig. 7 and 8) that extends over and is in contact with the first and second conductive electrodes 105a and 105b of the switch 700. In switch 700, phase change material region 109 extends over a portion of the sides of each island 701 and over a portion of a second surface (upper surface in the orientation of fig. 7 and 8) opposite the first surface. More precisely, in the example shown, the region 109 covers a portion of the side of the island 701, which is substantially parallel to the plane AA of fig. 7, i.e. the side of the island 701 extending in the direction of conduction of the switch 700. In the example shown, the heating element 113 of the switch 700 extends further over and in contact with a portion of the upper surface of the region 109 in a direction perpendicular to the conduction direction of the switch 700.

The island 701 is made of or includes a stack of dielectric materials. By way of example, the islands 701 are made of an electrically insulating and thermally conductive material, such as a material having a thermal conductivity greater than that of the phase change material region 109, such as aluminum nitride. This advantageously enables a lower thermal resistance to be obtained between the heating element 113 and the region 109. Thus facilitating the "quenching" phenomenon that occurs during the transition from the crystalline phase to the amorphous phase of region 109. As a variant, the islands 701 may be made of silicon dioxide.

In the example illustrated in fig. 7, each island 701 has an elongated shape along the conduction direction of the switch 700 and has a substantially trapezoidal cross section, the first surface of each island 701 having a surface area that is greater than the second surface area. The fact that the island 701 having a trapezoidal cross section (the sides of the island 701 are thus inclined) is provided with respect to the case where the island 701 has vertical sides perpendicular to the first and second surfaces advantageously makes it possible to facilitate covering of the island 701 with the region 109. However, the example illustrated in fig. 7 is not limiting, as each island 701 can have a cross-section of any shape, such as rectangular or square, as a variant. Islands 701 are for example distributed at regular intervals along the heating element (113).

In contrast to switch 100 (where region 109 is substantially planar), in switch 700 of fig. 7, phase change material region 109 is formed on a three-dimensional structure, or takes on a concave-convex shape. This advantageously enables increasing the width W of the phase change material region 109 and/or decreasing the outer dimensions of the switch.

More precisely, switch 700 may have a shorter distance between its control electrodes 115a and 115b, as compared to switch 100, while holding region 109 has a width W substantially equal to the width of region 109 of switch 100. This advantageously enables switch 700 to have smaller external dimensions and thus higher integration density than switch 100.

As an example, in the case where the switch 700 includes two islands 701 having a height of about 5 μm, a width corresponding to an average lateral dimension of the islands 701 measured in a direction perpendicular to the plane AA of fig. 7 (a direction parallel to the axis of the heating element 113) is about 1 μm, and the pitch is about 1 μm, and the width W of the region 109 formed on the three-dimensional structure is about 25 μm. In this case, the switch 700 has a width of about 5 μm, which corresponds substantially to the dimensions of the conductive electrodes 105a and 105b taken perpendicular to the plane AA of fig. 7. By comparison, in the case where the region 109 thereof has a width equal to about 25 μm, the width of the switch 100 is about 25 μm.

As a variant, the width W of the region 109 of the switch 700 may be made larger than the width of the region 109 of the switch 100, while keeping the distance between the electrodes 115a and 115b smaller than or equal to the distance between the electrodes 115a and 115b of the switch 100. This advantageously enables switch 700 to have a lower conduction compared to switch 100State resistance R _ON And thus has a lower figure of merit.

As a variant, it is possible to have the region 109 of the switch 700 have a greater width W than the region 109 of the switch 100 and a smaller thickness T than the region 109 of the switch 100, while maintaining a similar on-state resistance R _ON . The fact of reducing the thickness T of the region 109 advantageously enables a faster phase change to be obtained during switching. Furthermore, the reduction of the thickness T of the region 109 enables to obtain a phase change material with better crystalline and stoichiometric quality. Thus, the phase change of the material of region 109 advantageously requires less energy. Accordingly, the thermal efficiency of the switch 700 is improved relative to the switch 100.

Another advantage of the switch 700 resides in the fact that: the presence of island 701 enables the off-state capacitance C to be reduced _OFF . More precisely, the islands 701 enable reducing the parasitic capacitance Cp between the heating element 113 and the conductive electrodes 105a and 105b of the switch 700 due to the fact that each island 701 pulls the heating element 113 away from the electrodes 105a and 105 b. In the case where the width of the switch 700 is smaller than the width of the switch 100, the off-state capacitance C _OFF Further reduced relative to the switch 100.

Another advantage of the switch 700 resides in the fact that: the presence of the island 701 enables to reduce the inductance of the heating element 113 for the same width W with respect to the case of the switch 100. This appears to be due to the fact that: the mutual inductance between adjacent vertical portions of the heating element 113 becomes negative, thus causing a decrease in the total inductance. The reduced inductance of the heating element 113 advantageously enables higher switching speeds to be achieved.

Although this is not illustrated in fig. 7 and 8, the switch 700 may include passivation layers and insulating regions that are the same as or similar to the passivation layers 303 and regions 305 of the switch 300 of fig. 3 and 4.

Fig. 9 is a partial and simplified perspective view of an example of a phase change material based switch 900 according to one embodiment.

The switch 900 of fig. 9 includes elements common to the switch 700 of fig. 7 and 8. These common elements will not be described again in the following.

To avoid overloading the drawing, the substrate 101 and the electrically insulating layers 103 and 107 are not shown in fig. 9.

The switch 900 of fig. 9 differs from the switch 700 of fig. 7 and 8 in that the switch 900 comprises a single island 701 interposed between the phase change material region 109 and the conductive electrodes 105a and 105 b.

In a cross-sectional view along plane AA of fig. 9, switch 900 has a structure similar to that previously discussed with respect to fig. 8.

In switch 900, the island 701 is sized, particularly the width, such that a majority of the area 109 covers the island 701. This advantageously enables the heating element 113 to be further away from the conductive electrodes 105a and 105b relative to the switch 700, and thus reduces the off-state capacitance C of the switch 800 _OFF 。

Fig. 10 is a simplified and partial cross-sectional view of an example of a phase change material based switch 1000 according to one embodiment.

The switch 1000 of fig. 10 includes elements common to the switch 700 of fig. 7 and 8. These common elements will not be described in detail hereinafter.

The switch 1000 of fig. 10 differs from the switch 700 of fig. 7 and 8 in that in the switch 1000 the electrically insulating layer 111 extends over the entire upper surface of the structure. In the example shown, an electrically insulating layer 111 covers the phase change material region 109 and the dielectric material islands 701. More precisely, in this example, layer 111 covers the upper surface and sides of phase change material region 109, the portion of the upper surface of each island 701 not covered by region 109, all sides of each island 701, the portion of the upper surface of each conductive electrode 105a, 105b not covered by island 701, and the portion of the upper surface of electrically insulating layer 107 not covered by island 701.

In particular, the fact that the layer 111 is provided to cover the entire structure enables to simplify the manufacture of the switch 1000, compared to the switch 700 and the switch 900.

Fig. 11 is a simplified and partial cross-sectional view of an example of a phase change material based switch 1100 according to one embodiment.

The switch 1100 of fig. 11 includes elements common to the switch 700 of fig. 7 and 8. These common elements will not be described in detail hereinafter.

The switch 1100 of fig. 11 differs from the switch 700 of fig. 7 and 8 in that in the switch 1100 the phase change material region 109 covers each dielectric material island 701 and the electrically insulating layer 111 extends over the entire upper surface of the structure. More precisely, in the example shown, the phase change material region 109 covers the upper surface and all sides of each island 701 and further extends over and in contact with a portion of the upper surface of each conductive electrode 105a, 105b of the switch 1100. Further, in this example, layer 111 covers the upper surface and sides of phase change material region 109, the portions of the upper surface of each conductive electrode 105a, 105b not covered by region 109, and the portions of the upper surface of electrically insulating layer 107 not covered by islands 701.

In switch 1100, the portion of region 109 extending over and in contact with conductive electrodes 105a and 105b advantageously provides better electrical contact between phase change material region 109 and electrodes 105a and 105b than in switch 700, switch 900, and switch 1000. In particular, this further enables the manufacture of the switch 1100 to be simplified compared to the switch 700, the switch 900, and the switch 1000. Those skilled in the art will be able to adapt the embodiments of switches 1000 and 1100 described with respect to fig. 10 and 11 to a switch comprising any number of islands 701.

Fig. 12A and 12B illustrate, in simplified and partial cross-sectional form, successive steps of an example of a method of manufacturing a phase change material-based switch (e.g., switch 700 of fig. 7) according to one embodiment.

Fig. 12A more accurately illustrates the structure obtained at the end of successive steps of deposition and planarization of the electrically insulating layer 103, of the control electrodes 105a and 105b and of the layer 107. These steps are, for example, performed the same as or similar to those previously discussed with respect to fig. 6A.

Fig. 12B illustrates a step of forming an island 701 on the upper surface side of the structure. As an example, an aluminum nitride layer or a stack including an aluminum nitride layer and a silicon dioxide layer is first deposited on the upper surface side of the structure of fig. 12A, for example, by Plasma Enhanced Chemical Vapor Deposition (PECVD). The steps of photolithography and etching then enable only the portions of the layer or stack that are located at the desired locations of islands 701 to remain.

During subsequent steps, phase change material is deposited on the upper surface side of the substrate 101. An optional passivation layer, identical or similar to layer 303 of switch 300, may be deposited over the phase change material to protect it from oxidation. The steps of photolithography and etching then enable the phase change material and possibly the material of the optional passivation layer at the desired locations of the region 109 to remain.

Deposition of layer 111 may then be performed, for example, by Plasma Enhanced Chemical Vapor Deposition (PECVD) to form a silicon nitride layer or by Physical Vapor Deposition (PVD) to form an aluminum nitride layer. In the case where the electrically insulating layer 111 covers the electrodes 105a and 105b, then an opening may be formed in the layer 111, for example by photolithography and etching (e.g., reactive Ion Etching (RIE)), to expose portions of the upper surface of each electrode 105a, 105 b.

The heating element 113 may then be formed, for example, by a step of depositing a metallization layer on the upper surface side of the substrate 101, followed by a step of photolithography and etching. During this step, conductive vias may also be formed in the previously formed openings to restore contact of the electrodes 105a and 105b of the switch.

Those skilled in the art are able to adapt the method of manufacturing switch 700 described above with respect to fig. 12A and 12B to form switch 900, switch 1000, and switch 1100.

The embodiments of the switch 300 and the switch 500 discussed previously with respect to fig. 3-5 may be combined with the embodiments of the switches 700, 900, 1000, and 1100 of fig. 7-11. More precisely, it may be provided to form pillars in the phase change material region 109 of the switches 700, 900, 1000 and 1100 that are the same or similar to the pillars 301 of the switch 300. The structure of the switches 700, 900, 1000 and 1100 may be further modified to obtain a structure similar to that of the switch 500 in which the heating element 113 is interposed between the substrate 101 and the conductive electrodes 105a and 105 b. Those skilled in the art will be able to adapt the method of manufacturing switch 700 described above with respect to fig. 12A and 12B to form these different structures.

Fig. 13A-13D illustrate, in simplified and partial cross-sectional form, successive steps of an example of a method of manufacturing a phase change material based switch 1300 according to one embodiment.

Switch 1300 includes elements common to switch 100 of fig. 1 and 2. These common elements will not be described in detail hereinafter.

Fig. 13A more accurately illustrates the structure obtained after the steps of forming the electrically insulating layer 103, forming the conductive electrodes 105a and 105b, and deposition and planarization of the layer 107 on the upper surface side of the substrate 101. For example, these steps are implemented as previously discussed with respect to fig. 6A and 6B. Then, a formation step of the phase change material region 109 and the passivation layer 303 is performed, for example, as previously discussed with respect to fig. 6B.

Fig. 13B more precisely illustrates the structure obtained at the end of the step of depositing an electrically insulating layer 307 on the upper surface side of the structure of fig. 13A, followed by the step of depositing another electrically insulating layer 1301 of the cover layer 307. Layer 1301 is then planarized, for example by chemical mechanical polishing, to obtain a structure with a planar upper surface. Layer 1301 is made of silicon dioxide or aluminum nitride, as examples.

Fig. 13C more precisely illustrates the structure obtained at the end of the step of forming heating elements 1303 on and in contact with the upper surface of layer 307, heating elements 1303 being vertically aligned with region 109. The heating element 1303 is, for example, the same or similar to the heating element 113 of the switch 100. During this step, openings are formed in layer 1301 at desired locations of heating element 1303, for example by photolithography and etching. The opening is then filled entirely with the material of the heating element 1303, after which a planarization step is carried out, for example by chemical mechanical polishing, to obtain a structure with a planar upper surface, the heating element 1303 being flush with the upper surface of the layer 1301. Then, a subsequent step of depositing an electrically insulating layer 1305 on the upper surface side of the structure is performed. More precisely, layer 1305 covers the upper surface of layer 1301 and the upper surface of heating element 1303. As an example, layer 1305 is made of aluminum nitride.

Fig. 13D more precisely illustrates the structure of switch 1300 obtained at the end of the sequential steps of forming conductive vias 1307 (each conductive via 1307 extending perpendicularly from the upper surface of layer 1305 to the upper surface of one of the conductive electrodes 105a, 105b of switch 1300), forming another phase change material region 1309 covered with another passivation layer 1311, and depositing an electrically insulating layer 1313 on the upper surface side of the structure.

The conductive via 1307 is formed, for example, by photolithography and etching, at a desired location of the via 1307, for example, by forming an opening through the entire thickness of the layers 1305, 1301, and 307 to expose a portion of the upper surface of each electrode 105a, 105 b. The openings are then filled entirely with the material of the conductive vias 1307, and then a planarization step is performed, for example by chemical mechanical polishing, to obtain a structure with a planar upper surface, the conductive vias 1307 being flush with the upper surface of the layer 1305. As an example, the conductive via 1307 is made of tungsten.

For example, region 1309 and layer 1311 are formed as previously discussed (e.g., discussed with respect to fig. 6C for region 109 and layer 303). As an example, region 1309 and layer 1311 are made of the same material as region 109 and layer 303, respectively.

In the example shown, layer 1313 covers the upper surface and sides of layer 1311, the sides of region 1309, and the portions of the upper surface of layer 1305 not covered by region 1309. Layer 1313, for example, enables passivation of switch 1300 to protect it from oxidation.

The phase change material regions 109 and 1309 are each connected to one of the conductive electrodes 105a and 105b by a conductive via 1307, the region 1309 being located above the region 109 in the orientation of FIG. 13D. Heating element 1303 located between regions 109 and 1309 is electrically insulated from region 109 by layer 307 and from region 1309 by layer 1305.

The phase change material regions 109 and 1309 of switch 1300 may each have a thickness that is twice less than the thickness T of layer 109 of switch 100 while enabling switch 1300 to maintain an on-state resistance R with switch 100 _ON Substantially equal on-state resistance R _ON . This advantageously enables regions 109 and 1309 to have better crystal quality. The use of regions 109 and 1309 that are thinner than region 109 of switch 100 further advantageously enables switch 1300 to achieve higher switching speeds for phase change materialsThe similar cumulative thickness of the material, relative to switch 100, substantially doubles the surface of the phase change material exposed to the heat generated by the heating element in switch 1300. This results in switch 1300 having better energy performance than switch 100, with lower energy required for phase change of the materials of regions 109 and 1309.

Fig. 14A and 14B illustrate, in simplified and partial cross-sectional form, successive steps of an example of a method of manufacturing a phase change material based switch 1400 according to one embodiment.

Fig. 14A more precisely illustrates the structure obtained, for example, from the structure previously described with respect to fig. 13C, after the step of depositing an electrically insulating layer 1413 on the upper surface side of the structure and forming a further region 1409 of phase change material covered with a further passivation layer 1411 over and in contact with the upper surface of the layer 1305.

For example, region 1409 and layer 1411 are formed as previously discussed, for example, with respect to fig. 6C, for region 109 and layer 303. As an example, region 1409 and layer 1411 are made of the same material as region 109 and layer 303, respectively.

As an example, after forming region 1409 and layer 1411, layer 1413 is first deposited on the upper surface side of the structure. For example, after deposition, layer 1413 can cover the sides of region 1409 as well as the sides and upper surface of layer 1411. A planarization step, such as by chemical mechanical polishing, then enables the upper surface of layer 1411 to be exposed. As in the example illustrated in fig. 14A, after planarization, the layer 1413 is, for example, flush with the upper surface of the layer 1411.

Fig. 14B more precisely illustrates the structure obtained at the end of the step of forming conductive vias 1415 (each conductive via 1415 extends vertically from the upper surface of layer 1413 to the upper surface of one of conductive electrodes 105a, 105B), the step of forming other conductive vias 1417 (each conductive via 1417 extends vertically from the upper surface of layer 1411 to the upper surface of region 1409 on two opposite sides of region 1409 near region 1409), the step of forming two conductive electrodes 1419a and 1419B connected to conductive electrodes 105a and 105B, respectively, and the step of depositing an electrically insulating layer 1421 on the upper surface side of the structure.

Conductive vias 1415 are formed, for example, by photolithography and etching, at desired locations of the vias 1415, for example, by forming openings through the entire thickness of the layers 1413, 1305, 1301, and 307, to expose a portion of the upper surface of each electrode 105a, 105 b. The openings are then filled entirely with the material of the conductive vias 1415. Similarly, conductive vias 1417 are formed, for example, by photolithography and etching, at desired locations of vias 1417, for example, by forming openings through the entire thickness of layer 1411, to expose portions of the upper surface of layer 1409. A planarization step is then performed (e.g., by chemical mechanical polishing) to obtain a structure with a planar upper surface, with conductive vias 1415 and 1417 being flush with the upper surface of layer 1413. As an example, conductive vias 1415 and 1417 are made of tungsten.

For example, electrodes 1419a and 1419b are formed similar to that discussed with respect to fig. 6A for electrodes 105a and 105 b. Each of the electrodes 1419a, 1419b is connected to the corresponding electrode 105a, 105b by one of the conductive vias 1415 and to the region 1409 by one of the conductive vias 1417. As an example, electrodes 1419a and 1419b are made of the same material as electrodes 105a and 105b or comprise a stack of the same material layers as electrodes 105a and 105 b.

As an example, after forming electrodes 1419a and 1419b, layer 1421 is deposited on the upper surface side of the structure. For example, after deposition, layer 1413 may cover the upper surfaces and sides of electrodes 1419a and 1419b. A planarization step, for example by chemical mechanical polishing, then enables a structure to be obtained with a planar upper surface.

Switch 1400 has the same or similar advantages as switch 1300.

Although an embodiment of a method of manufacturing a switch comprising two phase change material regions 109 and 1409 has been illustrated with respect to fig. 14A and 14B, one skilled in the art will be able to adapt the method to form a switch comprising a plurality (more than two) of phase change material regions, i.e. an alternating structure comprising phase change material layers and heating element layers. This will enable a further reduction in the thickness of each region of phase change material relative to switch 100, while maintaining a similar conductance On-state resistance R _ON 。

The embodiments of switches 1300 and 1400 previously discussed with respect to fig. 13D and 14B may be combined with the embodiment of switch 300 of fig. 3. In particular, one of the phase change material regions 109, 1309, 1409 of switches 1300 and 1400 may be made to include one or more pillars similar to pillar 301 of switch 300 extending in the phase change material region, the pillars being made of a material having a thermal conductivity greater than that of the phase change material. Thus, switches 1300 and 1400 would benefit from similar advantages as switch 300.

The embodiments of switches 1300 and 1400 discussed previously with respect to fig. 13D and 14B may be further combined with the embodiments of switches 700, 900, 1000, and 1100 of fig. 7, 9, 10, and 11. In particular, at least one of the phase change material regions 109, 1309, 1409 of switches 1300 and 1400 may be formed on a three-dimensional surface that includes at least one island that is the same as or similar to island 701.

Those skilled in the art are able to adjust the method of manufacturing switch 1300 described above with respect to fig. 13A-13D and the method of manufacturing switch 1400 described below with respect to fig. 14A-14B to form these different structures.

Various embodiments and modifications have been described. Those skilled in the art will appreciate that certain features of these various embodiments and variations may be combined and that other variations will occur to those skilled in the art.

Finally, based on the functional indications given above, the actual implementation of the described embodiments and variants is within the ability of a person skilled in the art. In particular, the described embodiments are not limited to the specific examples of materials and dimensions mentioned in this disclosure.

The phase change material based switch (300; 500) may be summarized as including: a phase change material region (109); a heating element (113) electrically insulated from the phase change material region; and one or more pillars (301) extending in the phase change material region, the pillars being made of a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

The material of the pillars (301) may be electrically insulating.

The material of the pillars (301) may be selected from aluminum nitride and silicon nitride.

The phase change material may be a chalcogenide material.

An electrically insulating layer (307) may be interposed between the heating element (113) and the phase change material region (109).

The electrically insulating layer (307) may be made of the same material as the pillars (301).

The phase change material region (109) may be closer to the substrate (101) than the heating element (113), with the switch (300) formed inside and on top of the substrate (101).

The heating element (113) may be closer to the substrate (101) than the phase change material region, the switch (500) being formed inside and on top of the substrate (101).

The phase change material region (109) may be covered with a passivation layer (303).

The phase change material region (109) may couple first and second conductive electrodes (105 a,105 b) of a switch (300; 500).

Each pillar (301) may have a maximum lateral dimension equal to about 300 nm.

Each pillar (301) may be separated from an adjacent pillar (301) by a distance of about 300 nm.

The various embodiments described above may be combined to provide further embodiments. Aspects of the embodiments can be modified if necessary to employ concepts of the various patents, applications and publications to provide yet further embodiments.

These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the present disclosure.

Claims

1. A phase change material based switch comprising:

a phase change material region;

a heating element electrically insulated from the phase change material region; and

A plurality of pillars extending in the phase change material region, the pillars being made of a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

2. The switch of claim 1, wherein the material of the column is electrically insulating.

3. The switch of claim 1, wherein the material of the pillars is selected from aluminum nitride and silicon nitride.

4. The switch of claim 1, wherein the phase change material is a chalcogenide material.

5. The switch of claim 1, wherein an electrically insulating layer is interposed between the heating element and the phase change material region.

6. The switch of claim 5, wherein the electrically insulating layer is made of the same material as the pillars.

7. The switch of claim 1, wherein the phase change material region is closer to a substrate than the heating element, the switch being formed inside and on top of the substrate.

8. The switch of claim 1, wherein the heating element is closer to a substrate than the phase change material region, the switch being formed inside and on top of the substrate.

9. The switch of claim 1, wherein the phase change material region is covered with a passivation layer.

10. The switch of claim 1, wherein the phase change material region couples a first conductive electrode and a second conductive electrode of the switch.

11. The switch of claim 1, wherein each pillar has a maximum lateral dimension equal to about 300 nm.

12. The switch of claim 1, wherein each pillar is separated from an adjacent pillar by a distance of about 300 nm.

13. An apparatus, comprising:

a phase change material switch, the phase change material switch comprising:

a phase change material region;

a heating element on the phase change material; and

a plurality of pillars extending in the phase change material region.

14. The apparatus of claim 13, wherein the plurality of pillars are a material having a thermal conductivity greater than a thermal conductivity of the phase change material.

15. The apparatus of claim 14, wherein the switch comprises a first electrode spaced apart from a second electrode, the phase change material region being on the first and second electrodes.

16. The apparatus of claim 15, wherein the switch comprises a first insulating layer between the first electrode and the phase change material region.

17. An apparatus, comprising:

A substrate;

a first electrode on the substrate;

a second electrode on the substrate;

a phase change material on the first electrode and the second electrode;

a plurality of pillars in the phase change material, the plurality of pillars comprising a different material than the phase change material.

18. The apparatus of claim 17, wherein the material of the plurality of pillars has a thermal conductivity greater than a thermal conductivity of the phase change material.

19. The apparatus of claim 18, comprising a heating element on the phase change material.