A switch device and memory

Abstract

The present invention provides a switching device and a memory, the switching device comprises a lower electrode, an upper electrode and a switching material layer sandwiched between the lower electrode and the upper electrode, wherein: the switching material layer comprises at least one element of Te, Se and S; when the switching device is in an on state, the switching material layer is in a liquid state, and the bandgap width is 0; when the switching device is in an off state, the switching material layer is in a crystalline state, and a Schottky barrier is formed between the switching material layer and the upper electrode, and a Schottky barrier is formed between the switching material layer and the lower electrode. The switching device of the present invention adopts a switching material crystalline-liquid-crystalline phase change switching mechanism, has the advantages of large turn-on current, small leakage current, small threshold voltage, high unit consistency, compatibility with CMOS process, good thermal stability, simple elements, low toxicity and extreme shrinkage, etc., can drive phase change storage units, resistive storage units, ferroelectric storage units, magnetic storage units and other storage units, and realize high-density three-dimensional information storage.

Description

Technical Field

[0001] The present invention relates to the field of micro-nanoelectronic technology and relates to a switch device and a memory. Background Art

[0002] The vigorous development of emerging technologies such as artificial intelligence and the Internet of Things has led to an exponential growth in data output, posing a huge challenge to existing memory. At present, the size of transistors has been miniaturized to 2-3 nanometers, approaching its physical limit. To further increase storage density, it is necessary to increase the dimension and develop high-density three-dimensional stacked storage devices.

[0003] In three-dimensional memory, in order to avoid the influence of crosstalk, a switch device needs to be added to the storage layer. The switch device is a switch device that can control whether the unit stores or not. When the electrical signal applied to the switch device is much lower than the switch device opening condition, the switch device is closed, and the electrical signal cannot operate the storage unit; when the applied electrical signal is greater than the switch opening condition, the switch device is turned on, the material changes to a low resistance state, and the electrical signal directly acts on the storage unit, thereby performing a storage operation; when the applied electrical signal is removed, the switch material spontaneously returns from a low resistance state to a high resistance state, avoiding the influence of leakage current on the device unit. Existing switch devices include metal-oxide-semiconductor transistors (Metal-Oxide-SemiconductorTransistor), diodes (Diode), conductive bridge threshold switches (Conductive Bridge ThresholdSwitch), metal-insulator transition switches (Metal-Insulator Transition Switch) and bidirectional threshold switches (Ovonic Threshold Switch, OTS), etc.

[0004] However, existing switches have many limitations. For example, the leakage current of metal oxide semiconductor tubes will increase significantly during the process of miniaturization. For example, the on-state current of conductive bridge switches is in the microampere level, which cannot meet the needs of new memory. For a bidirectional threshold switch that can simultaneously meet the requirements of low leakage conductance and high on-state current, the material needs to be maintained in an amorphous state to switch, but its crystallization temperature is often lower than the post-annealing temperature of the CMOS process. To further meet the crystallization temperature requirements, toxic substances such as As need to be doped, which is not conducive to sustainable development needs.

[0005] Therefore, how to develop a switch material and a switch unit with high thermal stability has become an important technical problem that needs to be solved urgently by those skilled in the art. Summary of the invention

[0006] In view of the above-mentioned shortcomings of the prior art, an object of the present invention is to provide a switching device and a memory for solving the problems of low thermal stability of switching materials, high leakage current, low repeatability, low on-state current, and small switching ratio in the prior art.

[0007] To achieve the above-mentioned object and other related objects, the present invention provides a switching device, comprising a lower electrode, an upper electrode and a switching material layer sandwiched between the lower electrode and the upper electrode, wherein:

[0008] The switch material layer includes at least one element of Te, Se and S;

[0009] When the switch device is in an on state, the switch material layer is in a liquid state and the bandgap width is 0;

[0010] When the switch device is in a closed state, the switch material layer is in a crystalline state, and a Schottky barrier is formed between the switch material layer and the upper electrode, and a Schottky barrier is formed between the switch material layer and the lower electrode.

[0011] Optionally, when the applied voltage is greater than the threshold voltage, the switch material layer melts into the liquid state under the action of Joule heat to turn on the switch device; when the applied voltage is removed or the applied voltage is less than the threshold voltage, the switch material layer recrystallizes to make the switch device spontaneously return to the closed state.

[0012] Optionally, the switching device has a bidirectional threshold switching characteristic.

[0013] Optionally, the on / off current ratio of the switch device is in the range of 1×10 1 ~9.9×10 8 , the switching speed is faster than 200ns.

[0014] Optionally, the switch material still has any of the switching characteristics described above after annealing at a temperature higher than 400° C.

[0015] Optionally, the switch material layer further includes at least one of the elements Ge, Si, Al, Be, Mg, Ca, Sr, Ba and Mn.

[0016] Optionally, the material chemical formula of the switch material layer is (Te x Se y S z ) 1-a-b M a N b, wherein M and N are different elements, and M is selected from one of the elements Ge, Si, Al, Be, Mg, Ca, Sr, Ba and Mn, and N is selected from one of the elements Ge, Si, Al, Be, Mg, Ca, Sr, Ba and Mn; x, y, z, a and b are all atomic components, and satisfy x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤a+b<1, 0≤a≤0.5, 0≤b≤0.5.

[0017] Optionally, the material chemical formula of the switch material layer is Ge s Te 100-s , where s is the atomic component and satisfies 1≤s≤15.

[0018] Optionally, the thickness of the switch material layer is in the range of 0.2 nm to 200 nm.

[0019] Optionally, the thickness of the switch material layer is less than 2 nm.

[0020] Optionally, the switch material layer has atomic scale uniformity.

[0021] Optionally, the material of the lower electrode includes at least one of TiN, TaN, W, WN and TiNSi; the material of the upper electrode includes at least one of TiN, TaN, W, WN and TiNSi.

[0022] Optionally, the diameter or equivalent circular diameter of the switch material layer ranges from 0.4 nm to 500 nm.

[0023] The present invention also provides a memory, comprising a plurality of gated memory cells, wherein the gated memory cells comprise a gate unit and a memory cell, wherein the gate unit is electrically connected to the memory cell to drive the memory cell, wherein the gate unit comprises a switching device as described in any one of the above.

[0024] Optionally, the memory cell is selected from any one of a phase change memory cell, a resistive memory cell, a ferroelectric memory cell and a magnetic memory cell.

[0025] Optionally, a plurality of the selected memory cells form a cross-type memory array or a vertical memory array.

[0026] As described above, the switching device of the present invention includes a lower electrode, an upper electrode and a switching material layer sandwiched between the lower electrode and the upper electrode, and adopts a crystalline-liquid-crystalline phase change switching mechanism of the switching material. When the applied voltage is less than the threshold voltage (turn-on voltage), the crystalline switching material and the electrode material form a Schottky barrier, thereby suppressing the leakage current in the off state; when the applied voltage is greater than the threshold voltage (turn-on voltage), the generated Joule heat melts the crystalline switching material, and the liquid switching material has a band gap of 0 and has a metal-like resistivity. The Schottky junction disappears automatically, generating a large on-state current; when the applied voltage is removed, the liquid switching material rapidly recrystallizes, the device returns to the off state, and the Schottky junction automatically recovers, effectively reducing the leakage current in the off state. The switching device of the present invention has the advantages of large turn-on current, small leakage current, small threshold voltage, high unit consistency, compatibility with CMOS process, good thermal stability, simple elements, low toxicity and extreme shrinkage. It can drive phase change memory cells, resistive memory cells, ferroelectric memory cells, magnetic memory cells and other memory cells to achieve high-density three-dimensional information storage. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Shown is a schematic cross-sectional structure diagram of the switch device of the present invention.

[0028] Figure 2 Shown is a DC current-voltage curve of the switching device of the present invention.

[0029] Figure 3 Shown is a pulse voltage-current curve diagram of the switching device of the present invention.

[0030] Figure 4 A transmission electron microscope image is shown when the switch device of the present invention is in a closed state.

[0031] Figure 5 Display as Figure 4 A magnified image of the area indicated by the dashed box.

[0032] Figure 6 Display as Figure 4 Fourier transform of the area indicated by the dashed box.

[0033] Component number description

[0034] 1 Lower electrode

[0035] 2 Switch material layer

[0036] 3 Upper electrode DETAILED DESCRIPTION

[0037] The following describes the embodiments of the present invention through specific examples, and those skilled in the art can easily understand other advantages and effects of the present invention from the contents disclosed in this specification. The present invention can also be implemented or applied through other different specific embodiments, and the details in this specification can also be modified or changed in various ways based on different viewpoints and applications without departing from the spirit of the present invention.

[0038] Please refer to 1 to Figure 6 It should be noted that the illustrations provided in this embodiment are only used to illustrate the basic concept of the present invention in a schematic manner, and the drawings only show components related to the present invention rather than being drawn according to the number, shape and size of components in actual implementation. In actual implementation, the type, quantity and proportion of each component may be changed arbitrarily, and the component layout may also be more complicated.

[0039] Embodiment 1

[0040] This embodiment provides a switch device. Figure 1 , which is a schematic diagram of the cross-sectional structure of the switching device, includes a lower electrode 1, an upper electrode 3, and a switching material layer 2 sandwiched between the lower electrode 1 and the upper electrode 3, wherein the switching material layer 2 includes at least one element of Te (tellurium), Se (selenium) and S (sulfur).

[0041] Specifically, the switch material layer 2 can be made of Te, Se or S, or a compound, mixture or alloy consisting of any two elements of Te, Se and S, or a compound, mixture or alloy consisting of three elements of Te, Se and S.

[0042] Specifically, in order to further reduce leakage conduction, at least one of Ge, Si, Al, Be, Mg, Ca, Sr, Ba and Mn elements may be further doped on the basis of Te and / or Se and / or S.

[0043] As an example, the material chemical formula of the switch material layer is (Te x Se y S z ) 1-a-b M a N b , wherein M and N are different elements, and M is selected from one of the elements Ge, Si, Al, Be, Mg, Ca, Sr, Ba and Mn, and N is selected from one of the elements Ge, Si, Al, Be, Mg, Ca, Sr, Ba and Mn; x, y, z, a and b are all atomic components, and satisfy x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0≤a+b<1, 0≤a≤0.5, 0≤b≤0.5.

[0044] As an example, the material chemical formula of the switch material layer is Ge s Te 100-s , where s is the atomic component and satisfies 1≤s≤15.

[0045] As an example, the switch material layer 2 can be formed by sputtering, evaporation, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), metal compound vapor deposition (MOCVD), molecular beam epitaxy (MBE), atomic vapor deposition (AVD), atomic layer deposition (ALD) or other suitable methods.

[0046] Specifically, the switch material layer 2 of the switch device is in a crystalline state in a deposited state or when the device is in a closed state. When the applied voltage is less than the threshold voltage (turn-on voltage), the crystalline switch material and the electrode material form a Schottky barrier, which suppresses the leakage current in the closed state; when the applied voltage is greater than the threshold voltage (turn-on voltage), the generated Joule heat melts the crystalline switch material, the liquid switch material has a band gap of 0, has a metal-like resistivity, the Schottky junction disappears automatically, generates a large open current, and the switch device is in an open state; when the applied voltage is removed or the applied voltage is less than the threshold voltage, the liquid switch material quickly recrystallizes, the switch device returns to the closed state, and the Schottky junction automatically recovers, effectively reducing the leakage current in the closed state.

[0047] Specifically, the switch device is a two-terminal device and has a bidirectional threshold switch characteristic. The on / off current ratio range of the switch device is 1×10 1 ~9.9×10 8 , that is, the on / off current ratio is 1 to 8 orders of magnitude, and the switching speed of the switching device is faster than 200ns.

[0048] Specifically, the switch material still has the switching characteristics as described above after being annealed at a temperature higher than 400° C.

[0049] Specifically, the thickness of the switch material layer 2 can be set according to actual needs. For example, the thickness of the switch material layer 2 is in the range of 0.2nm to 200nm. In this embodiment, the thickness of the switch material layer 2 is preferably less than 2nm, so that when the switch device is in the off state, the material bandgap of the switch material layer 2 is increased, which is conducive to reducing the leakage current of the device.

[0050] As an example, the diameter or equivalent circular diameter of the switch material layer 2 ranges from 0.4 nm to 500 nm, and further, can be 0.4 nm to 60 nm, or 0.4 nm to 10 nm, that is, the switch device can be extremely miniaturized at 10 nm to 0.4 nm.

[0051] Specifically, the material of the lower electrode 1 includes but is not limited to at least one of TiN, TaN, W, WN and TiNSi; the material of the upper electrode 3 includes but is not limited to at least one of TiN, TaN, W, WN and TiNSi. The lower electrode 1 and the upper electrode 3 can be formed by sputtering, evaporation, chemical vapor deposition (CVD), plasma enhanced chemical vapor deposition (PECVD), low pressure chemical vapor deposition (LPCVD), metal compound vapor deposition (MOCVD), molecular beam epitaxy (MBE), atomic vapor deposition (AVD), atomic layer deposition (ALD) or other suitable methods.

[0052] Specifically, the switch material layer 2 has atomic-scale uniformity and forms a perfect interface with the TiN, TaN, W, WN or TiNSi electrode without obvious mutual diffusion, and the switch device has stable performance and good consistency between units.

[0053] The following is based on GeTe 16 (equivalent to Ge 5.88 Te 94.02 ) as a switching material to illustrate the switching performance of the switching device of the present invention. Figure 2 , showing the DC current-voltage curve of the switching device, the GeTe 16 The on-state current of the switch unit I on ≥10 -4 A, the leakage current of the switch unit I off ≤10 -6 A, the switching ratio of the switch unit is greater than or equal to 2, and the threshold voltage V th ≤2V.

[0054] Preferably, in this embodiment, the GeTe 16 The on-state current of the switch unit I on ≥10 -3 A, the leakage current of the switch unit I off ≤10 -9 A, the switching ratio of the switching unit can be greater than or equal to 5, and the device life exceeds 10 8 .

[0055] See also Figure 3, which is a pulse voltage-current curve of the switch device. When the voltage applied to the switch device is less than 1.75V, the switch device is in a closed state and the current is almost 0; when the voltage applied to the switch device exceeds the threshold voltage of 1.75V, the switch unit is instantly opened, and the current passing through the switch device increases sharply to 1.0mA; when the voltage applied to the switch device is removed (the voltage is 0.75V), the switch device is instantly closed again, and the current passing through the switch device decreases sharply, becoming a high-impedance state.

[0056] See also Figures 4 to 6 ,in, Figure 4 The transmission electron microscope image of the switch device when it is in the closed state is shown. Figure 5 Display as Figure 4 The enlarged image of the area indicated by the dashed box. Figure 6 Display as Figure 4 The Fourier transform of the area indicated by the dashed box in the figure. Figure 4 and Figure 5 It can be seen that the GeTe in the switch device in the off state 16 The layer is polycrystalline. Figure 6 The diffraction spots shown further prove that GeTe 16 It is crystalline. In addition, it can be seen that GeTe 16 The switching material has atomic-scale homogeneity and forms a perfect interface with the TiN electrode without significant interdiffusion. 16 A high Schottky barrier is formed with the electrode, the resistance of the device is very high, and the device is in the off state.

[0057] The switch device of this embodiment uses a new crystalline-liquid-crystalline switch mechanism. When the applied voltage is less than the threshold voltage (turn-on voltage), the crystalline switch material and the electrode material form a Schottky barrier, which suppresses the leakage current in the off state; when the applied voltage is greater than the threshold voltage (turn-on voltage), the Joule heat generated melts the crystalline switch material, the liquid switch material has a band gap of 0, has a metal-like resistivity, and the Schottky junction disappears automatically, generating a large on-state current; when the applied voltage is removed, the liquid switch material quickly recrystallizes, the device returns to the off state, and the Schottky junction automatically recovers, effectively reducing the leakage current in the off state. The switch device of this embodiment has the advantages of large turn-on current, small leakage current, small threshold voltage, high unit consistency, compatibility with CMOS process, good thermal stability, simple elements, low toxicity, and extreme miniaturization.

[0058] Embodiment 2

[0059] A memory is provided in the present embodiment, which includes a plurality of gated memory cells, wherein the gated memory cells include gated cells and memory cells, wherein the gated cells are electrically connected to the memory cells to drive the memory cells, wherein the gated cells include switching devices as described in the first embodiment, which have the advantages of large turn-on current, small leakage current, good thermal stability, simple materials, non-toxicity and fast switching speed, and can effectively drive phase change memory cells, resistive memory cells, ferroelectric memory cells or magnetic memory cells.

[0060] As an example, a plurality of the gating memory cells may form a cross-type memory array or a vertical memory array, thereby realizing high-density three-dimensional information storage. The cross-type memory array includes a plurality of word lines and a plurality of bit lines, the word lines and the bit lines are arranged crosswise, and the gating memory cells are located at the intersections of the word lines and the bit lines; the vertical memory array includes a plurality of bit lines and a plurality of selection lines, the bit lines and the selection lines are arranged crosswise, the gating cells are located at the intersections of the bit lines and the selection lines, a plurality of word line layers spaced apart in the vertical direction are stacked above the selection lines, and each gating cell has a plurality of memory cells on it to form a storage string.

[0061] In summary, the switching device of the present invention includes a lower electrode, an upper electrode and a switching material layer sandwiched between the lower electrode and the upper electrode. It adopts a crystalline-liquid-crystalline phase change switching mechanism of the switching material. When the applied voltage is less than the threshold voltage (turn-on voltage), the crystalline switching material and the electrode material form a Schottky barrier, thereby suppressing the leakage current in the off state; when the applied voltage is greater than the threshold voltage (turn-on voltage), the generated Joule heat melts the crystalline switching material, the liquid switching material has a band gap of 0, has a metal-like resistivity, the Schottky junction disappears automatically, and a large on-state current is generated; when the applied voltage is removed, the liquid switching material quickly recrystallizes, the device returns to the off state, and the Schottky junction automatically recovers, effectively reducing the leakage current in the off state. The switch device of the present invention has the advantages of large turn-on current, small leakage current, small threshold voltage, high unit consistency, compatibility with CMOS process, good thermal stability, simple elements, low toxicity and extreme shrinkage, etc. It can drive phase change memory cells, resistive memory cells, ferroelectric memory cells, magnetic memory cells and other memory cells to achieve high-density three-dimensional information storage. Therefore, the present invention effectively overcomes various shortcomings in the prior art and has high industrial utilization value.

[0062] The above embodiments are merely illustrative of the principles and effects of the present invention, and are not intended to limit the present invention. Anyone familiar with the art may modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by a person of ordinary skill in the art without departing from the spirit and technical concept disclosed by the present invention shall still be covered by the claims of the present invention.

Claims

1. A switching device, comprising a lower electrode, an upper electrode and a switching material layer sandwiched between the lower electrode and the upper electrode, characterized in that: The material chemical formula of the switch material layer is (Te x Se y S z ) 1-a-b M a N b , wherein M and N are different elements, and M is selected from one of Be, Mg, Ca, Sr, Ba and Mn, and N is selected from one of Be, Mg, Ca, Sr, Ba and Mn; x, y, z, a and b are all atomic components, and satisfy x+y+z=1, 0≤x≤1, 0≤y≤1, 0≤z≤1, 0<a+b<1, 0<a≤0.5, 0<b≤0.5; When the switch device is in an on state, the switch material layer is in a liquid state and the bandgap width is 0; When the switch device is in a closed state, the switch material layer is in a crystalline state, and a Schottky barrier is formed between the switch material layer and the upper electrode, and a Schottky barrier is formed between the switch material layer and the lower electrode.

2. The switch device according to claim 1, characterized in that: When the applied voltage is greater than the threshold voltage, the switch material layer melts into the liquid state under the action of Joule heat to turn on the switch device; when the applied voltage is removed or the applied voltage is less than the threshold voltage, the switch material layer recrystallizes to make the switch device spontaneously return to the closed state.

3. The switch device according to claim 1, characterized in that: The switch device has a bidirectional threshold switch characteristic.

4. The switch device according to claim 1, characterized in that: The on / off current ratio range of the switching device is 1×10 1 ~9.9×10 8 , switching speed is faster than 200 ns.

5. The switch device according to claim 1, characterized in that: The switch material is more than 400 o The invention can be annealed at a temperature of C and still have the switching characteristics of any one of claims 2 to 4.

6. The switch device according to claim 1, characterized in that: The thickness of the switch material layer ranges from 0.2 nm to 200 nm.

7. The switch device according to claim 6, characterized in that: The thickness of the switch material layer is less than 2 nm.

8. The switch device according to claim 1, characterized in that: The switch material layer has atomic scale uniformity.

9. The switch device according to claim 1, characterized in that: The material of the lower electrode includes at least one of TiN, TaN, W, WN and TiNSi; the material of the upper electrode includes at least one of TiN, TaN, W, WN and TiNSi.

10. The switch device according to claim 1, characterized in that: The diameter or equivalent circular diameter of the switch material layer ranges from 0.4 nm to 500 nm.

11. A memory, comprising a plurality of gated memory cells, wherein the gated memory cells comprise a gate unit and a memory cell, wherein the gate unit is electrically connected to the memory cell to drive the memory cell, wherein: The gating unit comprises a switching device as claimed in any one of claims 1 to 10.

12. The memory according to claim 11, characterized in that: The memory cell is selected from any one of a phase change memory cell, a resistive memory cell, a ferroelectric memory cell and a magnetic memory cell.

13. The memory according to claim 11, characterized in that: A plurality of the selected memory cells form a cross-type memory array or a vertical memory array.

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