Phase change switch with self-aligned heater and RF terminal

Abstract

A method of forming a phase change switching device is disclosed, the method comprising: providing a substrate; forming first and second RF terminals on the substrate; forming a strip of phase change material connected between the first and second RF terminals on the substrate; forming a heating element adjacent to the strip of phase change material such that the heating element is configured to control a conductive state of the strip of phase change material. The first and second RF terminals and the heating element are formed by a photolithography process that self-aligns the heating element with the first and second RF terminals.

Description

Background Technology

[0001] Modern electronic applications require switching devices capable of handling very high-frequency signals. For example, fifth-generation wireless applications (5G) will operate in frequency bands of 24.25 GHz or higher. In current semiconductor switching technologies (such as CMOS technology), maintaining the correct on / off ratio / isolation and insertion loss / R... ON (On-resistance) and C OFF (Switch-off capacitor) is difficult or impossible to implement. Phase-change switches represent a promising alternative technology that can meet the requirements of high-frequency applications. Phase-change switches utilize phase-change materials to control the conductive connection between two terminals. Switching operation is performed by changing the phase-change material between states (e.g., by applying heat to the phase-change material). While promising, phase-change switches are still in the early stages of development, and several design challenges remain to be addressed. For example, the device concept is subject to small variations in the physical characteristics of the device due to variations in manufacturing processes, such as R... ON (On-resistance), C OFF The device parameters, such as the shut-off capacitor, power consumption, and linearity, are sensitive to changes. Therefore, it is necessary to improve the manufacturing technology used to form phase-change switches. Summary of the Invention

[0002] A method for forming a phase change switch device is disclosed. According to an embodiment, the method includes: providing a substrate; forming first and second RF terminals on the substrate; forming a phase change material strip connected between the first and second RF terminals on the substrate; forming a heating element adjacent to the phase change material strip, such that the heating element is configured to control the conductive state of the phase change material strip, wherein the first and second RF terminals and the heating element are formed by a photolithography process that enables the heating element to self-align with the first and second RF terminals.

[0003] The method may be used alone or in combination to further include forming an electrically insulating material region on a substrate, and forming a first trench and a second trench in the electrically insulating material region by photolithography, wherein first and second RF terminals are formed in the first and second trenches, respectively.

[0004] Alone or in combination, the method further includes forming a third trench in an electrically insulating material region by photolithography, wherein a heating element is formed in the third trench.

[0005] Individually or in combination, the first, second, and third trenches are formed simultaneously through a single mask etching step.

[0006] Individually or in combination, first and second RF terminals are formed in first and second trenches, respectively, prior to the formation of the third trench, and wherein forming the third trench includes using the first and second RF terminals as etching masks.

[0007] Individually or in combination, the heating element has a different metallic composition than the first and second RF terminals.

[0008] The heating element is positioned below the phase change material strip, either alone or in combination.

[0009] Heating elements are positioned above the phase change material strip, either individually or in combination.

[0010] According to another embodiment, the method includes: forming an electrically insulating material region on a substrate; depositing a first metal layer on the electrically insulating material region; structuring the first metal layer to form first, second, and third lateral isolation portions of the first metal layer; and configuring the first, second, and third lateral isolation portions of the first metal layer such that the first and second lateral isolation portions are respectively first and second RF terminals of a phase-change switching device, and that the third lateral isolation portion is a heating element of the phase-change switching device.

[0011] Structuring the first metal layer individually or in combination includes: forming first, second, and third trenches in an electrically insulating material region; depositing the first metal layer on the electrically insulating material region to fill the first, second, and third trenches; and planarizing the upper surface of the first metal layer to form first, second, and third lateral isolation portions of the first metal layer, wherein the first, second, and third trenches are formed by a photolithography process that self-aligns the third trench with the first and second trenches.

[0012] Forming the first, second, and third trenches individually or in combination includes performing a mask etching process that simultaneously forms the first, second, and third trenches.

[0013] Alone or in combination, the method further includes providing an etch stop layer in an electrically insulating material region, and wherein a mask etching process is performed by etching the electrically insulating material region until each of the first, second, and third trenches reaches the etch stop layer.

[0014] The first metal layer may be individually or in combination with any one or more of the following: tungsten, tantalum, titanium, and platinum.

[0015] Alone or in combination, the method further includes forming a phase change material strip on a substrate, wherein a heating element is formed adjacent to the phase change material strip such that the heating element is configured to control the electrical conductivity state of the phase change material strip.

[0016] According to another embodiment, the method includes: providing a substrate; forming an electrically insulating material region on the substrate; depositing a first metal layer on the electrically insulating material region; structuring the first metal layer to form first and second lateral isolation portions of the first metal layer; forming a central trench in the electrically insulating material region between the first and second lateral isolation portions of the first metal layer; forming a second metal region in the central trench; configuring the first and second isolation portions of the first metal layer as first and second RF terminals of a phase-change switching device, respectively; and configuring the second metal region as a heating element of the phase-change switching device, the heating element being configured to control a conductive connection between the first and second RF terminals, wherein the central trench is formed by a photolithography process that self-aligns the central trench with the first and second lateral isolation portions of the first metal layer.

[0017] Alone or in combination, the photolithography process includes: forming a hard mask layer over first and second lateral isolation portions of a first metal layer; forming openings in the hard mask layer that expose the inner ends of the first and second lateral isolation portions of the first metal layer; and etching an electrically insulating material region through the openings to form a central trench.

[0018] Alone or in combination, the method further includes: depositing a dielectric layer after forming a central trench to cover the inner ends of the first and second lateral isolation portions with the dielectric layer; depositing a second metal layer on top of the dielectric layer in the central trench; and planarizing the upper surface of the second metal layer to remove the portion of the second metal layer outside the central trench, wherein the second metal region is formed by the second metal layer.

[0019] Structuring a first metal layer, either individually or in combination, to form first and second lateral isolation portions of the first metal layer includes: forming first and second trenches in an electrically insulating material region; depositing a first metal layer to fill the first and second trenches; and planarizing an upper surface of the first metal layer to form a first lateral isolation portion of the first metal layer in a first trench and a second lateral isolation portion of the first metal layer in a second trench.

[0020] Individually or in combination, the heating element has a different metallic composition than the first and second RF terminals.

[0021] Alone or in combination, the method further includes forming a phase change material strip on a substrate, wherein a heating element is formed adjacent to the phase change material strip such that the heating element is configured to control the electrical conductivity state of the phase change material strip. Attached Figure Description

[0022] The elements in the accompanying drawings are not necessarily proportional to each other. Similar reference numerals denote corresponding similar parts. Features of the various illustrated embodiments can be combined unless they are mutually exclusive. Embodiments are depicted in the accompanying drawings and described in detail below.

[0023] Figure 1 A phase-change switching device according to an embodiment is shown.

[0024] Figure 2 includes Figure 2A-2C This illustrates a method for forming according to an embodiment. Figure 1 The steps for selecting the phase change switching device are shown.

[0025] Figure 3 A phase-change switching device according to an embodiment is shown.

[0026] Figure 4 includes Figures 4A-4D This illustrates a method for forming according to an embodiment. Figure 3 The steps for selecting the phase change switching device are shown.

[0027] Figure 5 A phase-change switching device according to an embodiment is shown.

[0028] Figure 6 includes Figures 6A-6E This illustrates a method for forming according to an embodiment. Figure 5 The steps for selecting the phase change switching device are shown.

[0029] Figure 7 A phase-change switching device according to an embodiment is shown.

[0030] Figure 8 includes Figures 8A-8E This illustrates a method for forming according to an embodiment. Figure 7 The steps for selecting the phase change switching device are shown. Detailed Implementation

[0031] This document describes embodiments of a PCM (phase change material) switching device and a corresponding method for forming the PCM switching device. The PCM switching device includes a phase change material strip connected between first and second RF terminals, and a heating element disposed adjacent to the phase change material strip. The heating element is configured to control the conductive connection between the first and second RF terminals by heating the phase change material strip. Advantageously, the heating element is self-aligned to the first and second RF terminals. As a result, the device exhibits less variation in performance parameters attributable to process variations (e.g., capacitance between the heating element and the RF terminals, thermal resistance between the heating element and the surrounding area of ​​the PCM switching device). Furthermore, the self-alignment technique used to form the heating element and the RF terminals advantageously eliminates costly photolithography steps.

[0032] refer to Figure 1The image depicts a PCM switching device 100 according to an embodiment. The PCM switching device 100 includes a substrate 102. Generally, the substrate 102 can comprise any material compatible with semiconductor processing techniques such as deposition, etching, etc. For example, the substrate 102 can comprise semiconductor materials such as silicon (Si), carbon, silicon carbide (SiC), silicon germanium (SiGe), etc. In another example, the substrate 102 comprises a non-semiconductor material such as sapphire, glass, diamond, etc. In a particular embodiment, the substrate 102 is a commercially available bulk semiconductor wafer, such as a silicon wafer. In another example, the substrate 102 is a so-called SOI (silicon-on-insulator) substrate 102, which includes a buried layer of insulating material. The substrate 102 includes a main surface, which can be a substantially flat surface.

[0033] The PCM switching device 100 includes an electrically insulating material region 104 formed on the main surface of a substrate 102. Generally, the electrically insulating material region 104 can comprise any electrically insulating material that can be formed using typical semiconductor processing techniques such as CVD (chemical vapor deposition). Examples of such electrically insulating materials include semiconductor oxides and nitrides, such as silicon nitride (SiN), silicon dioxide (SiO2), silicon oxynitride (SiOxNY), etc. In another embodiment, the electrically insulating material region 104 comprises aluminum nitride (AlN). The electrically insulating material region 104 can be thermally insulating or thermally conductive. The electrically insulating material region 104 can comprise multiple layers of the same or different materials.

[0034] The PCM switching device 100 also includes first and second RF terminals 106 and 108. The first and second RF terminals 106 and 108 may be formed of a conductive metal, such as copper, aluminum, or alloys thereof. As shown, the PCM switching device 100 may also include an upper metallization 110 electrically connected to the first and second RF terminals 106 and 108 via a vertical through-hole structure 112. The upper metallization 110 may be a structured metallization, such as copper, aluminum, or alloys thereof, and the vertical through-hole structure 112 includes a conductive metal such as tungsten, copper, nickel, or aluminum. The upper metallization 110 may be connected to or form externally accessible terminals of the PCM switching device 100.

[0035] The PCM switching device 100 also includes a phase change material strip 114. The phase change material strip 114 may have an elongated geometry extending longitudinally parallel to the main surface of the substrate 102. The phase change material strip 114 is formed of a material capable of transitioning between two different phases, each of which has a different electrical conductivity. For example, the phase change material strip 114 may include a material that changes from an amorphous state to a crystalline state based on the application of heat to the phase change material, wherein the phase change material is electrically insulating in the amorphous state (i.e., blocking conductive connections) and conductive in the crystalline state (i.e., providing a low-resistance current path). Generally, phase change materials with this property include chalcogenides and chalcogenide alloys. Specifically, these phase change materials include germanium-antimony-tellurium (GST), germanium-tellurium, and germanium-antimony.

[0036] A phase change material strip 114 is connected between the first and second RF terminals 106 and 108. That is, the phase change material strip 114 makes low-ohmic contact with both the first and second RF terminals 106 and 108 through direct physical contact or through one or more conductive intermediates providing a low-resistance electrical connection. In one example, a conductive material such as TiN, W, or TiPtAu is provided between the first and second RF terminals 106 and 108 and the phase change material to improve the electrical connection between them. When the phase change material strip 114 is in a conductive state, current flows between the first and second RF terminals 106 and 108 in the direction of current flow through the phase change material strip 114.

[0037] The PCM switching device 100 also includes at least one heating element 116. The heating element 116 is arranged adjacent to a phase change material strip 114. In the depicted embodiment, the phase change material strip 114 is disposed above each of the first and second RF terminals 106, 108 and the heating element 116. The heating element 116 is arranged and configured to apply heat to the phase change material strip 114. For example, the heating element 116 may comprise a conductive or semi-conductive material that converts electrical energy into heat by ohmic heating. The heating element 116 may be connected between conductive heating terminals, which are located at... Figure 1 The cross-sectional view is not shown. For example, the heating element 116 may extend transversely to the current flow direction of the phase change material strip 114, and the contact position is with... Figure 1 Heating terminals spaced apart by a cross-sectional plane. The heating terminals are conductive structures that can be biased to force current through the heating element. The heating element 116 is separated from the phase change material strip 114 by an insulating liner 118. The insulating liner 118 electrically isolates the heating element 116 from the phase change material strip 114 while allowing significant heat transfer between them. For this purpose, the insulating liner 118 can be a relatively thin (e.g., less than 1 μm thick, and more typically less than 100 nm thick) layer of dielectric material, such as silicon dioxide (SiO2), silicon nitride (SiN), etc.

[0038] The PCM switching device 100 operates as follows. The heating element 116 is configured to control the conductive connection between the first and second RF terminals 106, 108 by applying heat to the phase change material strip 114. In the off state of the PCM switching device 100, the phase change material of the phase change material strip 114 is in an amorphous or partially amorphous state. As a result, the phase change material strip 114 blocks the voltage applied to the first and second RF terminals 106, 108. In the on state of the PCM switching device 100, the phase change material of the phase change material strip 114 is in a crystalline state. As a result, the phase change material strip 114 provides a low-resistance electrical connection between the first and second RF terminals 106, 108. The PCM switching device 100 performs the switching operation by heating the phase change material strip 114 using the heating element 116. Phase change materials (PCMs) can be transformed into an amorphous state by applying short pulses of high-intensity heat (e.g., pulses in the range of 50–1000 nanoseconds), causing the PCM to reach its melting temperature, for example, in the range of 600°C to 750°C, followed by rapid cooling. This is known as a "reset pulse." PCMs can also be transformed into a crystalline state by applying longer pulses of lower-intensity heat (e.g., pulses in the range of 0.5–10 microseconds), causing the PCM to reach a temperature at which the material rapidly crystallizes and becomes highly conductive, for example, in the range of 250°C to 350°C. This is known as a "set-up pulse."

[0039] According to an embodiment, the first and second RF terminals 106, 108 and the heating element 116 are formed by a photolithography process that self-aligns the heating element 116 with the first and second RF terminals 106, 108. This means that a photomask and a photolithography step form the first and second RF terminals 106, 108 and the heating element 116 either by directly forming these features or by forming features such as structured mask layers, trenches, etc., which in turn define the geometry of the first and second RF terminals 106, 108 and the heating element 116. The photolithography step utilizes a photomask with a predetermined pattern that selectively blocks light to replicate the predetermined pattern in a photosensitive material (e.g., a photoresist layer) formed on a semiconductor substrate 102. This pattern is used to produce the first and second RF terminals 106, 108 and the heating element 116 through a series of processing steps (e.g., etching, deposition, polishing, etc.). In some processes described herein, the heating element 116 and the first and second RF terminals 106, 108 are formed simultaneously using an etching step. In other processes described herein, the first and second RF terminals 106, 108 are formed by an initial etching step, and the heating element 116 is subsequently formed by a second etching step using the first and second RF terminals 106, 108 as etching masks. In any case, the first and second RF terminals 106, 108 and the heating element 116 are self-aligned because the geometry of each feature is attributed to a single photolithography step.

[0040] The advantages of forming the first and second RF terminals 106, 108 and the heating element 116 according to the self-aligned technique include the following: The position of the heating element 116 relative to the first and second RF terminals 106, 108 can be well controlled. For example, the heating element 116 can be centered between the first and second RF terminals 106, 108 with high precision. The spacing between the heating element 116 and the first and second RF terminals 106, 108, individually or in combination, can be well controlled to a high degree of precision. Conversely, in an apparatus in which the first and second RF terminals 106, 108 and the heating element 116 are not self-aligned (i.e., have geometries defined by two different photolithography steps), the position of the heating element 116 relative to the first and second RF terminals 106, 108 and / or the spacing between the heating element 116 and the first and second RF terminals 106, 108 is not well controlled due to the possibility of mask misalignment. Even small misalignments can have a significant impact on device performance by altering the capacitive coupling between the heating element 116 and the first and second RF terminals 106, 108 and / or by changing the thermal resistance of the heating element 116 to the surrounding environment. The self-alignment technique described herein largely mitigates this problem by eliminating potential sources of unreliability in the manufacturing process. Furthermore, the self-alignment technique advantageously eliminates costly photolithography steps.

[0041] Referring to Figure 2, the method for forming Figure 1 Selected process steps for the PCM switching device 100.

[0042] like Figure 2A As shown, a substrate 102 is provided, and an electrically insulating material region 104 is formed on the main surface of the substrate 102. The electrically insulating material region 104 can be formed by a deposition technique such as CVD (chemical vapor deposition), in which one or more layers of electrically insulating material, such as silicon nitride (SiN), silicon dioxide (SiO2), silicon oxynitride (SiOxNY), etc., are formed on the substrate 102. A first trench 120, a second trench 122, and a third trench 124 are formed in the electrically insulating material region 104. The first, second, and third trenches 120, 122, and 124 can be formed by a photolithography process that self-aligns the third trench 124 with the first and second trenches 120, 122. For example, a photoresist material layer (not shown) can be provided on the electrically insulating material region 104, and the photoresist material layer can be photolithographically patterned using a photomask (not shown) to form openings in the photoresist material layer. A patterned photomask can be directly used as an etching mask to form the first, second, and third trenches 120, 122, and 124. Alternatively, a patterned photomask can be used to form corresponding openings in a hard mask layer (not shown), which are then used to etch the first, second, and third trenches 120, 122, and 124 in sequence. In either case, an etching process, such as chemical etching, reactive ion etching, plasma etching, etc., can be performed to etch the electrically insulating material region 104. As a result, the first, second, and third trenches 120, 122, and 124 are formed to be self-aligned with each other.

[0043] According to an embodiment, an etch stop layer 126 is provided within the electrically insulating material region 104. The etch stop layer 126 exhibits lower selectivity for the etchant used to form the first, second, and third trenches 120, 122, 124 than the overlying region of the electrically insulating material region 104. For example, the etch stop layer 126 may comprise nitrides and / or metals, while the overlying material comprises oxides. In this case, a mask etching process is performed by etching the electrically insulating material region 104 until each of the first, second, and third trenches 120, 122, 124 reaches the etch stop layer 126. Thus, the depths of the first, second, and third trenches 120, 122, 124, and consequently the thicknesses of the functional elements of the PCM switching device 100, are well controlled.

[0044] like Figure 2BAs shown, a first metal layer 128 is deposited on the electrically insulating material region 104. The first metal layer 128 is conformally deposited to completely fill the first, second, and third trenches 120, 122, and 124. That is, the thickness of the first metal layer 128 is at least equal to the depth of the first, second, and third trenches 120, 122, and 124. Generally, the first metal layer 128 may comprise any metal or metal alloy having sufficient material properties to perform the function of the heating element 116 as described above. Examples of such metals include tungsten, tantalum, titanium, platinum, and any alloys or combinations thereof.

[0045] like Figure 2C As shown, the upper surface of the first metal layer 128 is planarized. The planarization step can be performed using any technique that continuously removes material from the upper surface of the first metal layer 128 (e.g., polishing such as CMP (chemical mechanical polishing)). The planarization step removes all portions of the first metal layer 128 outside the first, second, and third trenches 120, 122, and 124. As a result, the first, second, and third portions 130, 132, and 134 of the first metal layer 128 remain within the trenches. The first, second, and third portions 130, 132, and 134 are laterally isolated from each other, meaning there are no conductive paths between each portion.

[0046] It is possible Figure 2C Following the steps shown, subsequent processing is performed to complete the PCM switching device 100. The phase change material strip 114 and the insulating liner 118 can be formed, for example, by uniform thickness deposition and subsequent mask etching steps. For example, another layer or multiple layers of electrically insulating material can be formed on top of the functional elements of the PCM switching device 100 by deposition techniques such as CVD (chemical vapor deposition). For example, the upper metallization 110 and the vertical through-hole structure 112 can be formed by etching and deposition techniques. In the completed device, the first lateral isolation portion 130 and the second lateral isolation portion 132 of the first metal layer 128 correspond to the first and second RF terminals 106, 108 of the PCM switching device 100, respectively, and the third lateral isolation portion 134 of the first metal layer 128 corresponds to the heating element 116 of the PCM switching device 100.

[0047] Instead of about Figure 2A-2CThe process illustrated, alternative metal structuring techniques can be used to create the first, second, and third lateral isolation portions 130, 132, and 134 of the first metal layer 128. For example, the first metal layer 128 can be deposited on a flat surface of an electrically insulating material and subsequently structured using a direct metal etching technique (e.g., wet or dry etching). In another example, the first, second, and third lateral isolation portions 130, 132, and 134 of the first metal layer 128 can be formed using a stripping technique. According to this technique, a structured layer of stripping material is provided on a flat surface of the electrically insulating material. The first metal layer 128 is conformally deposited on the structured layer to fill the openings in the structured layer of the stripping material. The stripping material is removed, for example, by chemical dissolution, such that only the portion of the first metal layer 128 disposed within the openings is retained. In each case, only one photomask is used to structure the first metal layer 128 and the first, second, and third lateral isolation portions 130, 132, and 134 are self-aligned.

[0048] refer to Figure 3 The image depicts a PCM switching device 100 according to an embodiment. The PCM switching device 100 can be used with reference to... Figure 1 The PCM switching device 100 described is substantially the same, except that a phase change material strip 114 is disposed below each of the first and second RF terminals 106, 108 and the heating element 116.

[0049] Referring to Figure 4, the method for forming Figure 3 Selected process steps for the PCM switching device 100.

[0050] like Figure 4A As shown, a substrate 102 is provided, and an electrically insulating material region 104 is formed on the main surface of the substrate 102. Subsequently, a phase change material strip 114 and an insulating liner 118 are formed. This can be accomplished by depositing a uniform-thickness layer of phase change material on the electrically insulating material region 104 and subsequently structuring this uniform-thickness layer in a manner similar to that described above. The insulating liner 118 can be formed as a uniform-thickness layer and structured simultaneously with the phase change material. Alternatively, the insulating liner 118 can be formed by a separate deposition and etching sequence.

[0051] like Figure 4B As shown, an electrically insulating material is further deposited to grow an electrically insulating material region 104. As a result, a phase change material strip 114 and an insulating liner 118 are embedded within the electrically insulating material region 104. A planarization step, such as polishing, e.g., CMP (chemical mechanical polishing), can be performed after the deposition of the electrically insulating material to planarize the upper surface of the electrically insulating material region 104, thereby preparing the surface for the mask etching step described below.

[0052] like Figure 4CAs shown, first, second, and third trenches 120, 122, and 124 are formed in the region of the electrically insulating material. The first, second, and third trenches 120, 122, and 124 can be formed using a self-aligned mask etching technique, for example, with reference to a reference. Figure 2B The same manner is described. A third trench 124 is formed to expose the insulating liner 118, and first and second trenches 120, 122 are formed to expose the outer ends of the phase change material strip 114.

[0053] like Figure 4D As shown, the first, second, and third portions 130, 132, and 134 of the first metal layer 128 are formed within the first, second, and third trenches 120, 122, and 124, respectively. This can be achieved by depositing the first metal layer 128 and subsequently with reference... Figure 2B-2C A similar method is used to planarize the first metal layer 128. As a result, the functional elements of the PCM switching device 100 are formed. Figure 4D The steps shown are followed by subsequent processing to complete the PCM switching device 100 in a manner similar to that previously described.

[0054] refer to Figure 5 The image depicts a PCM switching device 100 according to an embodiment. The PCM switching device 100 differs from the previously described embodiment as follows. In the previously described embodiment, each of the first and second RF terminals 106, 108 and the heating element 116 is formed of a first metal layer 128, and therefore has the same metallic composition. Conversely, in… Figure 5 In the PCM switching device 100, the heating element 116 has a different metallic composition than the first and second RF terminals 106, 108. For example, the first and second RF terminals 106, 108 may be formed of a first metal or metal alloy (e.g., copper, aluminum, alloys thereof) having preferred conductivity. The heating element 116 may be formed of a second metal or metal alloy (e.g., tantalum, tungsten, nickel, etc., alloys thereof) having preferred heating properties, different from the first metal or metal alloy. Thus, there is no compromise between the preferred characteristics of the heating element 116 and the preferred characteristics of the first and second RF terminals 106, 108. Additionally, the PCM switching device 100 includes a dielectric layer 136 separating the first and second RF terminals 106, 108 from the heating element 116. The thickness of the dielectric layer 136 can be well controlled according to the deposition techniques described below, thereby maintaining favorable control over the lateral positioning of the heating element 116.

[0055] Referring to Figure 6, the method for forming Figure 5 Selected process steps for the PCM switching device 100.

[0056] like Figure 6AAs shown, a substrate 102 is provided, and an electrically insulating material region 104 is formed on the main surface of the substrate 102. The first and second lateral isolation portions 130, 132 of the first metal layer 128, for example, use a reference... Figure 2A-2C The same technique described is formed in the electrically insulating material region 104. The first metal layer 128 used to form the first and second lateral insulating portions 130, 132 may comprise a first metal or metal alloy having preferred conductive properties, such as copper, aluminum, or alloys thereof.

[0057] like Figure 6B As shown, a hard mask layer 138 is formed over the first and second lateral isolation portions of the first metal layer 128. The thickness and material composition of the hard mask layer 138 prevent the first and second lateral isolation portions 130, 132 from being etched during subsequent etching processes, which will be described below. For example, the hard mask layer 138 is structured using photolithographic patterning techniques to form openings that expose the inner ends of the first and second lateral isolation portions 130, 132. Subsequently, an etching process (e.g., wet chemical etching, reactive ion etching, plasma etching, etc.) is performed to remove the electrically insulating material through the openings in the hard mask layer 138. During this etching step, the first and second lateral isolation portions 130, 132 corresponding to the first and second RF terminals 106, 108 of the PCM switching device 100 are used as etching masks to form a central trench 140 (e.g., between the first and second lateral isolation portions 130, 132) between the first and second lateral isolation portions 130, 132. Figure 6C (As shown). The central trench 140 is therefore self-aligned to the first and second lateral isolation portions 130, 132 of the first metal layer 128, because the geometry of the central trench 140 is directly defined by the first and second RF terminals 106, 108, and the geometry of each structure is attributed to a single photomask.

[0058] like Figure 6C As shown, a dielectric layer 136 is deposited within a central trench 140 such that the dielectric layer 136 covers the inner ends of the first and second lateral isolation portions 130, 132. The dielectric layer 136 may be a relatively thin (e.g., less than 1 μm thick, more typically less than 100 nm thick) dielectric material layer, such as silicon dioxide (SiO2), silicon nitride (SiN), etc.

[0059] like Figure 6D As shown, a second metal layer 142 is deposited in a central trench 140 above the dielectric layer 136. The second metal layer 142 may be conformally deposited and have sufficient thickness to completely fill the central trench 140. The second metal layer 142 may comprise a second metal or metal alloy having preferred heating properties, such as tantalum, tungsten, nickel, and alloys thereof.

[0060] like Figure 6EAs shown, the upper surface of the second metal layer 142 is planarized to remove the portion of the second metal layer 142 outside the central trench 140. The planarization step can be performed using any technique that continuously removes material from the upper surface of the second metal layer 142, such as polishing, for example, CMP (chemical mechanical polishing). As a result, a second metal region 164 is formed in the central trench 140, wherein the second metal region 164 has a different material composition than the first and second lateral isolation portions 130, 132.

[0061] After performing the above steps, the second metal region 164 can be configured as the heating element 116 of the PCM switching device 100 described with reference to FIG. 6, and the first and second lateral isolation portions 130, 132 of the first metal layer 128 can be configured as the first and second RF terminals 106, 108 of the PCM switching device 100 according to the previously described technology. For example, the insulating liner 118 and the phase change material strip 114 can be formed on top of the second metal region 164 by a mask etching technique. Figure 5 As shown, a via 166 extending through the dielectric layer 136 can be formed to complete the electrical connection between the phase change material strip 114 and the first and second RF terminals 106, 108.

[0062] refer to Figure 7 The image depicts a PCM switching device 100 according to an embodiment. The PCM switching device 100 can be used with reference to... Figure 5 The described PCM switching device 100 is substantially the same, except that the phase change material strip 114 is disposed below each of the first and second RF terminals 106, 108 and the heating element 116. In this case, the dielectric layer 136 provides electrical isolation between the phase change material strip 114 and the heating element 116 in a manner similar to the previously described insulating liner 118.

[0063] Referring to Figure 8, the method for forming Figure 7 Selected process steps for the PCM switching device 100.

[0064] like Figure 8A As shown, a substrate 102 is provided, and an electrically insulating material region 104 is formed on the main surface of the substrate 102. A phase change material strip 114 is formed, for example, in accordance with a previously referenced... Figure 4B A similar manner is embedded within the electrically insulating material region 104. A planarization step, such as polishing with CMP (chemical mechanical polishing), can be performed after the deposition of the electrically insulating material to form a flat upper surface in the electrically insulating material region 104, thereby preparing the surface for the mask etching step described below.

[0065] like Figure 8BAs shown, the first and second lateral isolation portions 130, 132 of the first metal layer 128 are formed in the electrically insulating material region 104. The first metal layer 128 is deposited to fill the first and second trenches 120, 122 by forming the first and second trenches 120, 122 in the electrically insulating material region 104, and, for example, with reference to the preceding reference... Figure 6A The method described above is similar to that used to planarize the upper surface of the first metal layer 128, which can form the first and second lateral isolation portions 130, 132.

[0066] like Figure 8C As shown, a hard mask layer 138 is formed over the first and second lateral isolation portions 130, 132 of the first metal layer 128. Openings are formed in the hard mask layer 138 that expose the inner ends of the first and second lateral isolation portions 130, 132 of the first metal layer 128, and are, for example, aligned with the previously referenced... Figure 6B The method described above is similar to that described above, where an opening is etched into the electrically insulating material region 104 to form a central trench 140.

[0067] like Figure 8D As shown, a dielectric layer 136 is deposited within a central trench 140, such that the dielectric layer 136 is, for example, in conjunction with the preceding reference. Figure 6C The inner ends of the first and second lateral isolation portions 130, 132 are covered in a similar manner.

[0068] like Figure 8E As shown, the second metal region 164, for example, is in accordance with the previous reference. Figure 6D-6E The manner described is similar to that described above, formed in the central trench 140 above the dielectric layer 136.

[0069] The methods and structures disclosed herein with reference to specific accompanying drawings are equally applicable to all other embodiments to the extent consistent with these other embodiments. For example, specific techniques, materials, steps, etc., describing a method of forming an apparatus represented by one figure can be applied to any other method represented by other figures to the extent consistent with these other methods. Similarly, to the extent consistent with these other apparatuses, specific apparatus features, structures, or arrangements disclosed in conjunction with an apparatus represented by one figure can be incorporated into an apparatus represented by any other figure.

[0070] The terms “electrical connection”, “direct electrical connection”, etc., used in this article describe permanent low-impedance connections between electrically connected components, such as direct contact between related components or low-impedance connections via metals and / or highly doped semiconductors.

[0071] As used herein, the terms “having,” “containing,” “including,” “comprising,” etc., are open-ended terms indicating the presence of the said element or feature, but not excluding additional elements or features. The articles “a” and “said” are intended to include both plural and singular unless the context clearly indicates otherwise.

[0072] It should be understood that the features of the various embodiments described herein can be combined with each other unless otherwise specifically stated.

[0073] Although specific embodiments have been illustrated and described herein, those skilled in the art will understand that various alternatives and / or equivalent implementations may be used instead of the specific embodiments shown and described without departing from the scope of the invention. This application is intended to cover any modifications or variations of the specific embodiments discussed herein. Therefore, the invention is intended to be limited only by the claims and their equivalents.

Claims

1. A method for forming a phase-change switching device, the method comprising: Provide substrate; A first RF terminal and a second RF terminal are formed on the substrate; A phase change material strip is formed on the substrate connecting the first RF terminal and the second RF terminal; as well as A heating element is formed adjacent to the phase change material strip, such that the heating element is configured to control the electrical conductivity of the phase change material strip. The first RF terminal, the second RF terminal, and the heating element are formed by a photolithography process, wherein the photolithography process self-aligns the heating element with the first RF terminal and the second RF terminal, and wherein the photolithography process includes: An electrically insulating material region is formed on the substrate; A first trench and a second trench are formed in the region of the electrically insulating material; The first RF terminal and the second RF terminal are formed in the first trench and the second trench, respectively; A third trench is formed in the region of the electrically insulating material; and The heating element is formed in the third groove.

2. The method of claim 1, wherein, Each of the first trench, the second trench, and the third trench is formed simultaneously through a single mask etching step.

3. The method of claim 1, wherein, Before forming the third trench, the first RF terminal and the second RF terminal are formed in the first trench and the second trench, respectively, and wherein forming the third trench includes using the first RF terminal and the second RF terminal as an etching mask.

4. The method of claim 3, wherein, The heating element has a different metal composition than the first RF terminal and the second RF terminal.

5. The method of claim 1, wherein, The heating element is positioned below the phase change material strip.

6. The method of claim 1, wherein, The heating element is positioned above the phase change material strip.

7. A method for forming a phase-change switching device, the method comprising: Provide substrate; An electrically insulating material region is formed on the substrate; A first metal layer is deposited on the electrically insulating material region; The first metal layer is structured to form a first lateral isolation portion, a second lateral isolation portion, and a third lateral isolation portion of the first metal layer; as well as The first lateral isolation portion, the second lateral isolation portion, and the third lateral isolation portion of the first metal layer are configured such that the first lateral isolation portion and the second lateral isolation portion are respectively the first RF terminal and the second RF terminal of the phase change switch device, and the third lateral isolation portion is the heating element of the phase change switch device.

8. The method according to claim 7, wherein, Structuring the first metal layer includes: A first trench, a second trench, and a third trench are formed in the region of the electrical insulating material; Depositing the first metal layer on the electrically insulating material region to fill the first trench, the second trench, and the third trench; and The upper surface of the first metal layer is planarized to form the first lateral isolation portion, the second lateral isolation portion, and the third lateral isolation portion of the first metal layer. The first trench, the second trench, and the third trench are formed by photolithography, and the photolithography process self-aligns the third trench with the first trench and the second trench.

9. The method according to claim 8, wherein, Forming the first trench, the second trench, and the third trench includes performing a mask etching process that simultaneously forms the first trench, the second trench, and the third trench.

10. The method of claim 9, further comprising providing an etch stop layer within the electrically insulating material region, wherein, The mask etching process is performed by etching the electrically insulating material region until each of the first trench, the second trench, and the third trench reaches the etch stop layer.

11. The method according to claim 7, wherein, The first metal layer comprises any one or more of the following: tungsten, tantalum, titanium, and platinum.

12. The method of claim 7, further comprising forming a phase change material strip on the substrate, wherein, The heating element is formed adjacent to the phase change material strip, such that the heating element is configured to control the electrical conductivity of the phase change material strip.

13. A method for forming a phase-change switching device, the method comprising: Provide substrate; An electrically insulating material region is formed on the substrate; A first metal layer is deposited on the electrically insulating material; The first metal layer is structured to form a first lateral isolation portion and a second lateral isolation portion of the first metal layer; A central trench is formed in the electrical insulating material region between the first lateral isolation portion and the second lateral isolation portion of the first metal layer; A second metal region is formed in the central trench; The first lateral isolation portion and the second lateral isolation portion of the first metal layer are respectively configured as the first RF terminal and the second RF terminal of the phase change switch device, and The second metal region is configured as a heating element of the phase-change switching device, and the heating element is configured to control the conductive connection between the first RF terminal and the second RF terminal. The central trench is formed by photolithography, which enables the central trench to self-align with the first lateral isolation portion and the second lateral isolation portion of the first metal layer.

14. The method according to claim 13, wherein, The photolithography process includes: A hard mask layer is formed over the first lateral isolation portion and the second lateral isolation portion of the first metal layer; An opening is formed in the hard mask layer to expose the inner ends of the first lateral isolation portion and the second lateral isolation portion of the first metal layer; and The electrically insulating material region is etched through the opening to form a first trench.

15. The method of claim 14, further comprising: After the central trench is formed, a dielectric layer is deposited to cover the inner ends of the first lateral isolation portion and the second lateral isolation portion. A second metal layer is deposited in the central trench, on top of the dielectric layer; as well as The upper surface of the second metal layer is planarized to remove the portion of the second metal layer outside the central trench, and The second metal region is formed by the second metal layer.

16. The method of claim 13, wherein structuring the first metal layer to form the first lateral isolation portion and the second lateral isolation portion of the first metal layer comprises: A first trench and a second trench are formed in the region of the electrically insulating material; Deposit the first metal layer to fill the first trench and the second trench; as well as The upper surface of the first metal layer is planarized to form the first lateral isolation portion of the first metal layer in the first trench, and the second lateral isolation portion of the first metal layer in the second trench.

17. The method according to claim 13, wherein, The heating element has a different metal composition than the first RF terminal and the second RF terminal.

18. The method of claim 13, further comprising forming a phase change material strip on the substrate, wherein, The heating element is formed adjacent to the phase change material strip, such that the heating element is configured to control the electrical conductivity of the phase change material strip.

Images