A low power consumption all-optical phase change memory based on plasma enhancement effect
By designing concentric phase change rings and metal disk rings on silicon-based planar optical waveguides, and utilizing the plasma enhancement effect, the problems of increased power consumption and slow switching speed caused by non-uniform crystallization in phase change materials were solved, realizing a low-power and fast-switching all-optical phase change memory.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- NINGBO UNIV
- Filing Date
- 2022-02-21
- Publication Date
- 2026-04-24
AI Technical Summary
The phase change materials used in existing integrated photonic devices suffer from increased power consumption and slow switching speeds due to non-uniform crystallization.
A low-power all-optical phase-change memory based on plasma enhancement effect is adopted. By using silicon-based planar optical waveguides and concentric phase-change rings, combined with metal disks and rings, the uniform crystalline to amorphous state conversion of phase-change materials is achieved through evanescent field coupling.
Uniform thermal distribution of phase change materials was achieved, reducing power consumption and accelerating switching speed. The crystallization and amorphization processes of the device require only 20pJ and 18pJ, respectively, with switching times of 1ns and 10ns, respectively, significantly improving the performance of traditional devices.
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Figure CN114665011B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of microelectronics, and in particular to a low-power all-optical phase-change memory based on the plasma enhancement effect. Background Technology
[0002] The current surge in data presents new challenges to traditional computing and storage models. Integrated silicon photonics platforms, due to their inherent energy and bandwidth advantages, can alleviate the physical limitations imposed by the use of electrical interconnects and traditional von Neumann computing architectures. For decades, optical signals have dominated long-distance communication. Recently, with the increasing influence of silicon photonics, chip-to-chip and even on-chip optical signals have seen tremendous development. Indeed, by making photoelectric conversion redundant and accessing the inherent high bandwidth and low transmission loss of the optical domain, shifting critical on-chip data operations to all-optical implementations can potentially save energy and increase speed. This work focuses on the development of phase-change all-optical memories (PPCMs), which, by providing non-volatile all-photonic storage capabilities, make it possible to transition from the electrical to the optical domain. PPCM devices allow for all-optical encoding of information on the crystalline portion of a waveguide-realized phase-change material layer, thereby modulating the amplitude of the transmitted signal. Currently, some research groups internationally have reported on integrated phase-change all-optical memories. However, these studies on integrated photonic devices have not yet taken into account the impact of non-uniform crystallization in phase-change materials on the uniform thermal distribution that affects their operational reliability, leading to increased device power consumption. Summary of the Invention
[0003] The technical problem to be solved by the present invention is to provide a low-power all-optical phase-change memory based on plasma enhancement effect, which has uniform phase-change heating, faster switching speed and lower power consumption.
[0004] The technical solution adopted by the present invention to solve the above-mentioned technical problems is as follows: a low-power all-optical phase-change memory based on plasma enhancement effect, including a waveguide, wherein the waveguide is a silicon-based planar optical waveguide, and a phase-change ring structure is disposed on the waveguide, which can undergo a reversible phase transition from crystalline to amorphous state under the waveguide evanescent field coupling effect, wherein the phase-change ring structure is embedded between a metal disk and a metal ring.
[0005] Furthermore, the bottom of the concentric circle structure formed by the phase change ring structure, the metal disk, and the metal ring is located on the upper surface of the waveguide.
[0006] Furthermore, the concentric circle structure formed by the phase change ring structure, the metal disk, and the metal ring is semi-embedded in the waveguide.
[0007] Furthermore, the phase-change ring structure, the metal disk, and the concentric circle structure formed by the metal ring are completely embedded in the waveguide.
[0008] Furthermore, the waveguide is a Si3N4 waveguide located on a SiO2 substrate; or the waveguide is a Si waveguide located on an SOI substrate.
[0009] Furthermore, the phase transition ring structure is a phase transition layer Ge2Sb2Te5 or Ge2Sb2Se4Te, possessing at least two stable states: crystalline and amorphous, with these two states exhibiting significantly different absorption coefficients for the probe light. This phase transition ring structure undergoes a reversible phase transition from crystalline to amorphous state under the waveguide evanescent field coupling, achieving a uniform phase reversal.
[0010] Furthermore, the metal material used in the metal disk and the metal ring is Ag, Au, Al or Cu.
[0011] Furthermore, the phase change ring structure, the metal disk, and the metal ring all have the same thickness.
[0012] Furthermore, the Si3N4 waveguide has a width of 1.2 μm - 1.4 μm and a thickness of 170 nm - 340 nm; the phase transition ring structure has a ring width of 20 nm - 30 nm and a thickness of 20 nm - 50 nm; the metal disk has a diameter of 10 nm - 30 nm, the metal ring has a ring width of 45 - 85 nm, and both the metal disk and the metal ring have a thickness of 20 nm - 50 nm; the silicon substrate has a width of 4 μm and a thickness of 2 μm.
[0013] Furthermore, the Si waveguide has a width of 0.4µm-0.75µm and a thickness of 170nm-340nm; the phase transition ring structure has a ring width of 20nm-30nm and a thickness of 20nm-50nm; the metal disk has a diameter of 10nm-30nm, the metal ring has a ring width of 45-85nm, and both the metal disk and the metal ring have a thickness of 20nm-50nm; the silicon substrate has a width of 4µm and a thickness of 2µm.
[0014] Compared with existing technologies, the advantages of this invention are as follows: This invention provides a low-power all-optical phase-change memory based on the plasma-enhanced effect. This structure enables temperature control during the crystallization process, achieving uniform phase reversal of the phase change material, thereby avoiding power loss problems caused by partial crystallization. Simultaneously, due to the plasma effect, the electric field strength in the phase change region is greatly enhanced, accelerating the switching speed of the device. Furthermore, compared with traditional phase-change memory devices, this structure requires significantly less energy: only 20 pJ for crystallization and only 18 pJ for amorphization, with a crystallization time of 1 ns and an amorphization time of 10 ns. Both power consumption and switching time are improved compared to traditional devices. This result provides an option for developing reconfigurable and multifunctional optoelectronic devices with ultra-compact size, fast switching speed, and low power consumption. Attached Figure Description
[0015] Figure 1 (a) is a schematic diagram of the device structure of the present invention, and (bd) are schematic diagrams of cross-sections under three different structures, respectively;
[0016] Figure 2 A 3D structural simulation diagram of a COMSOL phase-change memory device model;
[0017] Figure 3 The graph shows the transmittance variation of crystalline and amorphous states at room temperature in the range of 1300 nm to 1700 nm.
[0018] Figure 4 Insertion loss diagrams for crystalline and amorphous states at room temperature in the 1300nm-1700nm range;
[0019] Figure 5 Transient temperature distribution diagrams for crystalline and amorphous states and the applied pulse diagrams;
[0020] Figure 6 Schematic diagrams of temperature distribution and temperature difference for three different structures during crystallization;
[0021] Figure 7 This is a schematic diagram showing how temperature difference and power consumption change with embedding depth. Detailed Implementation
[0022] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. I. Specific Implementation Methods
[0024] Example 1
[0025] A Si3N4 waveguide with a width of 1.3 μm and a thickness of 170 nm was constructed. A phase transition ring structure, capable of undergoing a reversible phase transition from crystalline to amorphous state under evanescent field coupling, was placed on the upper surface of the waveguide. This phase transition ring structure was embedded between a metal disk and a metal ring (obtainable using a conventional deposition-exposure-etching process). The phase transition ring structure was made of Ge2Sb2Te5 material, with a ring width of 25 nm and a thickness of 30 nm. Both the metal disk and the metal ring were made of Ag metal, with the Ag disk having a diameter of 20 nm and the Ag ring having a width of 65 nm and a thickness of 30 nm. The silicon substrate was SiO2 with a width of 4 μm and a thickness of 2 μm. The phase transition ring structure has at least two stable states, namely crystalline and amorphous, and these two states have significantly different absorption coefficients for the probe light. Under the waveguide evanescent field coupling, a reversible phase transition from crystalline to amorphous occurs, completing a uniform phase reversal.
[0026] like Figure 1 (a) and Figure 1 As shown in (b), the device mainly consists of a Si3N4 waveguide, a SiO2 substrate, and a phase transition region above the waveguide. The phase transition region is composed of metals Ag and Ge2Sb2Te5, resembling a concentric circle structure. From the inside out, the concentric circle structure consists of a 25nm radius metal disk, a 25nm wide phase transition ring, and a 65nm wide metal ring. The bottom of the entire concentric circle structure is located on the upper surface of the waveguide.
[0027] Table 1. Physical parameters of each material
[0028]
[0029] As shown in Table 1, the high refractive index contrast between crystalline (aGST) and amorphous (cGST) states of GST is beneficial for constructing reconfigurable and non-volatile memory devices. Combining metallic plasmons with phase change materials can reduce the size of devices to tens of nanometers or even smaller, significantly lower than the diffraction limit of traditional optical devices, and achieve greater optical contrast.
[0030] When this concentric circle structure is placed entirely on the waveguide, the overall temperature range of the phase transition region during crystallization is within 2℃, and the temperature within the phase transition region is 327-329℃ when fully crystallized. Figure 6 As shown in (ab).
[0031] Example 2
[0032] Similar to Embodiment 1, the difference lies in that: the concentric circular structure formed by the phase change ring structure, the metal disk, and the metal ring is semi-embedded in the waveguide as a whole, such as... Figure 1As described in (c), the overall temperature range of the phase transition region during crystallization is within 2℃, and the temperature within the phase transition region is 221-223℃ during complete crystallization. Figure 6 (cd) in the middle.
[0033] Example 3
[0034] Similar to Embodiment 1, the difference lies in that the concentric circular structure formed by the phase transition ring structure, the metal disk, and the metal ring is completely embedded into the waveguide, such as... Figure 1 As described in (d), the overall temperature range of the phase transition region during crystallization is within 2℃, and the temperature within the phase transition region is 195-197℃ during complete crystallization. Figure 6 (ef) in.
[0035] Example 4
[0036] Similar to Example 1, the difference is that the waveguide is a Si waveguide, and the Si waveguide is located on an SOI substrate.
[0037] Example 5
[0038] Similar to Example 1, the difference is that the phase change ring structure material is selected as Ge2Sb2Se4Te.
[0039] In addition to the above embodiments, the metal materials used in the metal disk and metal ring can also be Au, Al, or Cu; the Si3N4 waveguide width can also be any value between 1.2 μm and 1.4 μm, and the thickness can be any value between 230 nm and 170 nm-230 nm; the Si waveguide width can also be any value between 0.4 μm and 0.75 μm, and the thickness can be any value between 170 nm and 230 nm; the ring width of the phase change ring structure can also be any value between 20 nm and 30 nm, and the thickness can be any value between 20 nm and 50 nm; the diameter of the metal disk can also be any value between 10 nm and 30 nm, the ring width of the metal ring can be any value between 45 nm and 85 nm, and the thickness of both the metal disk and the metal ring can be any value between 20 nm and 50 nm. Furthermore, the metal materials of the metal disk and the metal ring must be consistent, and the thicknesses of the phase change ring structure, the metal disk, and the metal ring must be consistent.
[0040] II. Results Analysis
[0041] Figure 2 This is a 3D structural simulation diagram of the COMSOL phase-change memory device model (including the three structures of Examples 1-3), provided by... Figure 2It can be seen that the metal and the phase transition ring are similar to a concentric circle structure. By utilizing the plasma effect of the inner and outer metals, the electric field is confined within the gap of the phase transition region, which greatly improves the switching speed of the device and significantly reduces the power consumption of the device.
[0042] Figure 3 and Figure 4 The figures show the transmittance and insertion loss of crystalline and amorphous states at room temperature (including the three structures in Examples 1-3). Figure 3 The device exhibits a maximum optical contrast of 11% at 1550nm. Figure 4 This indicates that the insertion loss of this structure is less than 2dB. This demonstrates that the insertion loss is significantly lower than that of traditional devices, which helps reduce power consumption.
[0043] Figure 5 (ab) in the figure represent the transient temperature change during crystallization and the applied pulse of 20mW, 1ns, respectively. Figure 5 In the diagram, (cd) represents the transient temperature change during amorphization and the applied pulse of 1.8mW for 10ns, respectively. This demonstrates that compared to conventional devices, this device (including the three structures in Examples 1-3) has a faster switching speed and lower power consumption.
[0044] Figure 6 (af) in the diagram represents the phase transition region temperature under three different structures, as well as the maximum and minimum temperature difference in the phase transition region. The temperature difference shown for all structures does not exceed 2℃, which we define as TD (temperature difference). Figure 7 This diagram illustrates how temperature difference and power consumption vary with normalized embedding depth (au). Figure 7 The crystallization process can be completed with only a 20pJ pulse, reducing device power consumption. The performance of this phase-change memory device under three different structures was used to explore the maximum overlap between the phase-change material and the electric field, which affects the device's switching speed and power consumption. The structure located on the waveguide exhibits the highest optical contrast and lowest insertion loss compared to embedded and semi-embedded structures.
[0045] In summary, the device of the present invention can complete the phase transition during crystallization, which is beneficial for multi-level storage and solves the power consumption problem caused by partial crystallization.
[0046] The foregoing description is not intended to limit the invention, nor is the invention limited to the examples given. Any changes, modifications, additions, or substitutions made by those skilled in the art within the scope of the invention should also be considered within the protection scope of the invention.
Claims
1. A low-power all-optical phase-change memory based on plasma enhancement effect, comprising a waveguide, wherein the waveguide is a silicon-based planar optical waveguide, characterized in that: The waveguide is provided with a phase transition ring structure that can undergo a reversible phase transition from crystalline to amorphous state under the evanescent field coupling effect of the waveguide. The phase transition ring structure is embedded between a metal disk and a metal ring. The phase transition ring structure is a phase transition layer Ge2Sb2Te5 or Ge2Sb2Se4Te, which has at least two stable states, namely crystalline and amorphous, and these two states have significantly different absorption coefficients for the probe light.
2. The low-power all-optical phase-change memory based on plasma enhancement effect according to claim 1, characterized in that: The bottom of the concentric circular structure formed by the phase change ring structure, the metal disk, and the metal ring is located on the upper surface of the waveguide.
3. The low-power all-optical phase-change memory based on plasma enhancement effect according to claim 1, characterized in that: The phase-change ring structure, the metal disk, and the concentric circle structure formed by the metal ring are all semi-embedded in the waveguide.
4. The low-power all-optical phase-change memory based on plasma enhancement effect according to claim 1, characterized in that: The phase-change ring structure, the metal disk, and the concentric circle structure formed by the metal ring are completely embedded in the waveguide.
5. A low-power all-optical phase-change memory based on plasma enhancement effect according to claim 1, characterized in that: The waveguide is a Si3N4 waveguide located on a SiO2 substrate; or the waveguide is a Si waveguide located on an SOI substrate.
6. A low-power all-optical phase-change memory based on plasma enhancement effect according to claim 1, characterized in that: The metal disk and the metal ring are made of the same metal material, namely Ag, Au, Al or Cu.
7. A low-power all-optical phase-change memory based on plasma enhancement effect according to any one of claims 2-6, characterized in that: The phase change ring structure, the metal disk, and the metal ring all have the same thickness.
8. A low-power all-optical phase-change memory based on plasma enhancement effect according to claim 5, characterized in that: The Si3N4 waveguide has a width of 1.2 μm - 1.4 μm and a thickness of 170 nm - 230 nm; the phase transition ring structure has a ring width of 20 nm - 30 nm and a thickness of 20 nm - 50 nm; the metal disk has a diameter of 10 nm - 30 nm, the metal ring has a ring width of 45 - 85 nm, and both the metal disk and the metal ring have a thickness of 20 nm - 50 nm; the SiO2 substrate has a width of 4 μm and a thickness of 2 μm.
9. A low-power all-optical phase-change memory based on plasma enhancement effect according to claim 5, characterized in that: The Si waveguide has a width of 0.4µm-0.75µm and a thickness of 170nm-230nm; the phase transition ring structure has a ring width of 20nm-30nm and a thickness of 20nm-50nm; the metal disk has a diameter of 10nm-30nm, the metal ring has a ring width of 45-85nm, and both the metal disk and the metal ring have a thickness of 20nm-50nm; the SOI substrate has a width of 4µm and a thickness of 2µm.