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EP-4739060-A1 - RADIO FREQUENCY SWITCH AND RADIO FREQUENCY DEVICE

EP4739060A1EP 4739060 A1EP4739060 A1EP 4739060A1EP-4739060-A1

Abstract

A radio frequency switch (100) is provided. The switch includes a first radio frequency terminal (106), a second radio frequency terminal (108), and a phase change material (114) electrically coupled between the first radio frequency terminal (106) and the second radio frequency terminal (108). The phase change material comprises an alloy of at least three different chemical elements, wherein the alloy contains at least one of In, Ag and Sn.

Inventors

  • KADOW, CHRISTOPH
  • Stenz, Christian
  • WUTTIG, MATTHIAS

Assignees

  • Infineon Technologies AG
  • RWTH Aachen University

Dates

Publication Date
20260506
Application Date
20241029

Claims (15)

  1. A radio frequency switch, comprising: a first radio frequency terminal, a second radio frequency terminal, and a phase change material electrically coupled between the first radio frequency terminal and the second radio frequency terminal, wherein the phase change material (PCM) comprises an alloy (A1) of at least three different chemical elements, characterized in that the alloy contains at least one of In, Ag and Sn.
  2. The radio frequency switch according to claim 1, wherein the alloy (A1) has the following chemical formula (I): (X 1 (n-m) X 2 m )Y p Z r (I), wherein: • X 1 and X 2 are each independently selected from Ag, In and a combination of Ag and In, • Y is selected from Sb, Sn, Bi and a combination thereof, • Z is selected from Te, Se and a combination of Te and Se, • n is an integer between 1 and 3, • m is any number between 0 and 3, provided that (n-m) is > 0, and • p and r are each independently an integer between 1 and 3.
  3. The radio frequency switch according to claim 1 or 2, wherein the alloy (A1) is selected from the group consisting of In 3 SbTe 2 , AgSnSe 2 and AgSnTe 2 .
  4. The radio frequency switch according to any of the preceding claims, wherein the PCM further comprises a second alloy (A2) of at least two different chemical elements, wherein the second alloy contains at least one of Ge, Sn, Pb, Sb, Bi, S, Se, Te and Ag.
  5. The radio frequency switch according to claim 4, wherein the second alloy (A2) is: - an alloy of at least three different chemical elements selected from the group consisting of Sb, Bi, Se, Te and Ag, or - an alloy of at least two different chemical elements selected from the group consisting of Ge, Sn, Pb, Sb, S, Se and Te.
  6. The radio frequency switch according to claim 4 or 5, wherein the alloy (A2) has one of the following chemical formulae (II), (III) and (IV): X 3 X 4 (X 5 ) 2 (II) X 6 X 7 (III) X 6 X 7 :X 8 s X 9 t (IV) wherein: • X 3 and X 4 are each independently selected from Ag, Sb, Bi and a combination thereof, • X 5 is selected from Se, Te and a combination of Se and Te, • X 6 is selected from Ge, Sn, Pb and combinations thereof, • X 7 is selected from S, Se, Te and combinations thereof, • X 8 is selected from Pb, Sb and a combination of Pb and Sb, • X 9 is selected from Se, Te and a combination of Se and Te, and • s and t are each independently an integer between 1 and 3.
  7. The radio frequency switch according to any of claims 4 to 6, wherein the alloy (A2) is selected from the group consisting of AgSbSe 2 , AgSbTe 2 , AgBiSe 2 , AgBiTe 2 , PbS, PbSe, PbTe, SnTe, GeTe, PbS:PbSe (1:1), PbSe:PbTe (1:1), GeTe:Sb 2 Te 3 (1:1) and GeTe:Sb 2 Te 3 (2:1).
  8. The radio frequency switch according to any of claims 4 to 7, wherein the PCM comprises the alloy (A1) in an amount of 50 - 95 at.% and the alloy (A2) in an amount of 5 - 50 at.%.
  9. The radio frequency switch according to any of claims 4 to 8, wherein the alloy (A1) and the alloy (A2) both have an octahedral-like atomic arrangement (preferably rock salt like structure) and the following condition is fulfilled: C 1 − C 2 / C 1 ≤ 5 % C1: lattice constant of alloy (A1) in Å C2: lattice constant of alloy (A2) in Å.
  10. The radio frequency switch according to any of the preceding claims, wherein the PCM has a crystallization temperature above 150°C, and/or the PCM has an annealing temperature below 400°C.
  11. The radio frequency switch according to any of the preceding claims, wherein the PCM in an on-state of the radio frequency switch has a resistivity below 3.4E-4 Ohm-cm, and/or the PCM has a resistance ratio between an off state of the radio frequency switch and an on state of the radio frequency switch of at least 3E4.
  12. The radio frequency switch according to any of claims 4 to 11, wherein the first alloy (A1) is a bad metal and the second alloy (A2) is a metavalent material.
  13. The radio frequency switch of any one of claims 1 to 12, further comprising a heater thermally coupled to and electrically insulated from the phase change material.
  14. A radio frequency device comprising: the radio frequency switch of any one of claims 1 to 13, and a radio frequency circuit coupled to at least one of the first radio frequency terminal and the second radio frequency terminal.
  15. The radio frequency device of claim 14, wherein the radio frequency device is configured such that the radio frequency switch switches a signal having a frequency of at least 1 GHz when the radio frequency device is in operation.

Description

TECHNICAL FIELD The present application relates to radio frequency switches and radio frequency devices. BACKGROUND The technical requirements for radio frequency (RF) applications using high frequencies, such as radar sensing and mobile communication according to the 5G standard and future 6G, are increasing. In particular, switches having improved characteristics compared to state-of-the-art CMOS switches will be required to meet future demands. Phase change switches are considered as promising candidates for switching RF signals. Such phase change switches use a phase change material (PCM) which typically exhibits a higher electric conductivity in a crystalline phase state than in an amorphous phase state. By changing the phase state of the phase change material, a switch device including such a material may be switched on and off. For example, to change the phase state from amorphous to crystalline, typically a heater is employed heating the phase change material causing crystallization. This switching on by causing crystallization is also referred to as a set operation. In the set operation, the heater is actuated in such a way that the temperature of the phase change material is above its crystallization temperature, typically about 250°C, but below the melting point typically in a range of 600°C to 900°C, for example. The length of the heating pulse caused by the heater is chosen such that any amorphous region present in the PCM can regrow into the crystalline phase state. When switching off the switching device, also referred to as reset operation, the heater is actuated in such a way that the temperature of the PCM is raised above the melting point (for example above about 600°C to 900°C) followed by a comparatively rapid cool-down which freezes the phase change material into an amorphous state. Suitable phase change materials conventionally used for such phase change switches include germanium telluride (GeTe), antimony telluride (Sb2Te3) or germanium-antimony-tellurium (GeSbTe, usually referred to as GST), and heaters may be made of a material like polycrystalline silicon or tungsten. While these materials allow the manufacturing of switches for RF applications, requirements for such switches regarding their properties are increasing. There is a need for RF switches with very low insertion loss. This need is driven by several applications: The first are RF-tuners for mobile phone antennas which require low insertion loss on smaller and smaller chip areas at established 5G frequencies up to 6GHz. The second are RF systems operating at higher frequencies, e.g. X-band and above, which also need low insertion loss switches. The present invention addresses the technical problem of providing improved RF-switches and RF-tuners. This is achieved by finding more suitable phase-change materials (PCMs) than are used in the state-of-the-art. So far, the only phase-change materials, used successfully for PCM-based RF-switches, are GeTe and Sb2Te3. Another option are PCMs from the Ge-Sb-Te ternary phase diagram. While ternary Ge-Sb-Te compounds are widely used for memory applications, they are not a good choice for RF-applications for the following reasons: First, their electrical resistivity in the on-state (= crystalline) state is fairly high compared to GeTe and Sb2Te3. Second, their switching behavior is very complex due to multiple crystalline phases which makes it hard to switch into a low-resistance on-state. Usually, advanced functional materials like PCMs are discussed in terms of their band structure and the resulting properties. Recently, a rather different approach and its potential for designing advanced functional materials has been described. This approach is based on the assumption that a quantification of chemical bonding provides the metric to describe systematic trends in the resulting material properties. The close interrelation between precise quantum chemical bonding descriptors and materials properties hence enables the application of these descriptors as property predictors. SUMMARY According to an embodiment, a radio frequency switch is provided, comprising: a first radio frequency terminal,a second radio frequency terminal, anda phase change material electrically coupled between the first radio frequency terminal and the second radio frequency terminal, wherein the phase change material comprises an alloy of at least three different chemical elements, characterized in that the alloy contains at least one of In, Ag and Sn. According to another embodiment, a radio frequency device is provided, comprising: the radio frequency switch explained above, anda radio frequency circuit coupled to at least one of the first radio frequency terminal and the second radio frequency terminal. The above summary is merely a brief overview over some embodiments and is not to be construed as limiting. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a schematic side view of a radio frequency switch according t