A threshold gating material, a threshold gating device unit and a preparation method thereof

Abstract

The present invention relates to a threshold gating material, a threshold gating device unit and a preparation method thereof. The chemical general formula of the threshold gating material is (In x Te y ) a M 1‑a , where 0.1 ≤ x / y ≤ 1, 0 < x < 100, 0 < y < 100, x + y = 100, 0 < a ≤ 0.2, and M is a threshold switching material including at least one element of Group VI. The threshold gating device unit of the present invention has the advantages of low leakage current, low threshold voltage, large gating ratio, fast turn-on speed, etc., and the service life and reliability of the device are improved.

Description

Technical Field

[0001] The invention belongs to the field of microelectronic technology, and in particular relates to a threshold gating material, a threshold gating device unit and a preparation method thereof. Background Art

[0002] With the popularity of smart phones and various information electronic devices, humans have entered the era of big data with explosive information density. In order to better process this massive amount of data, data storage is crucial. The slow speed of traditional memory is not conducive to high-speed data transmission and processing. Therefore, new storage technologies with high speed, high life and high density have become a solution that has attracted much attention. Representatives of new memories include phase change memory and resistive memory. In order to achieve high-density storage architecture, these two memories often use the result of three-dimensional stacking, which makes the basic building blocks of the two memories a storage unit plus a switch unit. Among them, the switch unit plays the role of suppressing leakage current and gating the storage unit in the chip. In recent years, the threshold transfer switch (OTS) using sulfur compound thin film materials as the medium is considered to be the most valuable gate. The basic principle of the OTS gate is as follows: use electrical signals to control the switch of the gate device. When the electrical signal is applied to the gate device unit and exceeds the threshold voltage, the material changes from a high resistance state to a low resistance state, and the voltage-maintaining device will continue to be in the on state; when the electrical signal is removed, the material changes from a low resistance state to a high resistance state, and the device is in the off state. SROvshinsky first discovered sulfur-based materials with threshold transition characteristics in the late 1960s, which triggered scientists' research on the threshold transition phenomenon. Based on this, a series of sulfur-based compounds with threshold transition characteristics were discovered.

[0003] As a gating device, considering the requirements of limiting leakage, driving storage cells, and being compatible with storage cells and process solutions, its performance requirements are low leakage current, high drive current, high switching ratio, high speed, low threshold voltage, good thermal stability, long life and high reliability. However, for the common gating Ge-Se material, its leakage is large, the threshold voltage is high, and the switching speed is slow, which has problems in practical application. In view of this, how to develop new materials to reduce the threshold voltage, improve the turn-on speed, switching ratio, life and reliability to meet the actual requirements has become a problem to be solved by technicians in this field. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a threshold gating material, a threshold gating device unit and a preparation method thereof, which are used to solve the problem that the leakage current, gating speed, gating ratio, threshold voltage, life and reliability of the OTS gate in the prior art need to be further improved.

[0005] The present invention provides a threshold gating material, the chemical formula of the threshold gating material is (In x Te y ) a M 1-a , wherein 0.1≤x / y≤1, 0<x<100, 0<y<100, x+y=100, 0<a≤0.2, and M is a threshold switching material including at least one sixth main group element.

[0006] The chemical formula of the threshold switch material is Ge b As c Se 100-b-c , 0<b≤20, 10≤c≤45.

[0007] The threshold gating device unit comprises, from bottom to top, a lower electrode layer, a threshold gating material layer as claimed in claim 1, an upper electrode layer, and an extraction electrode arranged on the upper electrode layer.

[0008] The material of the lower electrode layer includes at least one of C, W, Cu, Al, Ti, Ta, TiN, WNx, TaN, Pt, Au, Ag, Co, and Ni.

[0009] The material of the upper electrode layer includes at least one of W, Cu, Al, C, Ti, Ta, TiN, WNx, TaN, Pt, Au, Ag, Co, and Ni.

[0010] The material of the lead-out electrode includes at least one of W, Cu, Al, Co, Pt, Au, and Ag.

[0011] The present invention provides a method for preparing a threshold gating device unit, comprising the following steps:

[0012] (1) preparing a lower electrode layer;

[0013] (2) depositing a threshold gating material layer on the lower electrode layer;

[0014] (3) preparing an upper electrode layer on the threshold gating material layer;

[0015] (4) Prepare lead electrodes on the upper electrode layer.

[0016] The preparation is carried out by sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or atomic layer deposition.

[0017] Beneficial Effects

[0018] The threshold gating device unit of the present invention can realize an instantaneous transition from a high resistance state to a low resistance state under the action of external energy; when the external energy is removed, it can immediately transition from a low resistance state to a high resistance state. x Te y ) a M 1-a When the threshold gating material is used as the medium of the threshold gating device unit, the threshold gating device unit of the present invention has the advantages of low leakage current, low threshold voltage, large gating ratio, fast turn-on speed, etc., and the life and reliability of the device are improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figures 1 to 4 It is a cross-sectional view of the steps of the method for preparing the threshold gating device unit of the present invention.

[0020] Figure 5 The voltage-current (VI) curve diagram of the threshold gating device unit of the present invention measured under voltage excitation.

[0021] Figure 6 This is a fatigue life test of the threshold gating device unit of the present invention. DETAILED DESCRIPTION

[0022] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0023] Example 1

[0024] Figures 1 to 4 It is a step cross-sectional view showing the method for preparing the threshold gating device unit provided by the present invention.

[0025] First, perform step 1): prepare the lower electrode layer. Figure 1As an example, the lower electrode layer can be prepared by any one of 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) or atomic layer deposition (ALD). In this embodiment, the lower electrode layer is preferably prepared by CVD. The material of the lower electrode layer can be at least one of W, Cu, Al, C, Ti, Ta, TiN, WNx, TaN, Pt, Au, Ag, Co, and Ni. In this embodiment, the material of the lower electrode layer is preferably W. The diameter of the electrode of the W lower electrode layer prepared by CVD is 120nm and the height is 200nm.

[0026] Then, step 2) is performed: a threshold gating material layer is prepared on the lower electrode. Figure 2 A threshold gating material layer is prepared on the lower electrode. The threshold gating material layer uses a threshold gating material with a chemical formula of (In x Te y ) a M 1-a , wherein 0.1≤x / y≤1, 0<x<100, 0<y<100, x+y=100, 0<a≤0.2, and M is a threshold switch material including at least one element of the sixth main group. Preferably, the (In x Te y ) a M 1-a The chemical formula of the threshold switch material is (In 40 Te 60 ) 0.1 (Ge 10 As 35 Se 55 ) 0.9 、(In 38 Te 62 ) 0.1 (Ge 15 As 35 Se 50 ) 0.9 、(In 37.5 Te 62.5 ) 0.1 (Ge 20 As 30 Se 50 ) 0.9 The threshold selection material layer can be prepared by any one of the methods such as sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or atomic layer deposition.

[0027] Then, step 3) is performed: forming an upper electrode layer on the threshold gating material layer. Figure 3 As an example, the upper electrode layer can be prepared on the threshold selection material layer by using any one of sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition (AVD) or atomic layer deposition. The material of the upper electrode layer may be, for example, at least one of W, Cu, Al, C, Ti, Ta, TiN, WNx, TaN, Pt, Au, Ag, Co, and Ni.

[0028] In this embodiment, preferably, a magnetron sputtering method is used to prepare an upper electrode layer on the threshold gating material layer. The material of the upper electrode layer is preferably TiN. The process parameters are: the base gas pressure is 1×10 -5 Pa, the gas pressure during sputtering is 0.2 Pa, the gas flow ratio of Ar / N2 is 1:1, the sputtering power is 100 W, the substrate temperature is 25°C, and the sputtering time is 20-25 min. The electrode thickness of the obtained TiN upper electrode layer is about 20 nm.

[0029] Finally, perform step 4): see Figure 4 , preparing an extraction electrode on the upper electrode layer, as an example, the extraction electrode can be prepared by any one of sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or atomic layer deposition. In this way, the upper and lower electrode layers, other components such as storage units, drive circuits and peripheral circuits in the threshold selection device unit can be integrated through the extraction electrode, so as to prepare a complete threshold selection device unit, and the processing method adopted is a conventional semiconductor process.

[0030] As an example, the material of the lead-out electrode may include any one of the single metal materials W, Pt, Au, Ti, Al, Ag, Cu and Ni, or an alloy material composed of any two or more of the above single metal materials W, Pt, Au, Ti, Al, Ag, Cu and Ni, or a nitride containing one of the above single metal materials W, Pt, Au, Ti, Al, Ag, Cu and Ni.

[0031] In this embodiment, preferably, the lead-out electrode is prepared by magnetron sputtering, the material is Al, and the film thickness of the prepared lead-out electrode is 200 nm.

[0032] The following is an explanation of the method based on (In 38 Te 62) 0.1 (Ge 15 As 35 Se 50 ) 0.9 The threshold switch device unit of the threshold switch material is tested for electrical performance. Under voltage excitation, the voltage-current (VI) curve of the threshold switch device unit is tested as follows: Figure 5 As is known to those skilled in the art, as the voltage increases, the current value first increases continuously, and at a certain point, the current suddenly jumps, and then continues to increase. This point is the threshold point of the threshold switch device unit, and the voltage at this point is the threshold voltage.

[0033] See also Figure 5 For the 38 Te 62 ) 0.1 (Ge 15 As 35 Se 50 ) 0.9 The threshold switching device unit of the two DC operations, it can be seen that for the (In 38 Te 62 ) 0.1 (Ge 15 As 35 Se 50 ) 0.9 The threshold switch device unit has a threshold voltage of about 2.9V, which is greatly reduced compared to the threshold voltage of 4.5V of GeSe. At the same time, the device has an extremely low leakage current of 1.32nA. The turn-on current and the switch ratio are increased. Moreover, after the threshold voltage is reduced, the damage to the threshold switch device unit will be relatively small in each operation, which will extend the service life of the device and further improve the reliability. Therefore, the threshold switch device unit improved by the technology of the present invention is more suitable for practical applications.

[0034] See also Figure 6 For the 38 Te 62 ) 0.1 (Ge 15 As 35 Se 50 ) 0.9 Fatigue life test of threshold switch device unit. It can be seen that for the (In 38 Te 62 ) 0.1 (Ge 15 As 35 Se 50 ) 0.9 The fatigue life of the threshold switch device unit can reach 4*107 , much larger than 10 of general GeSe materials 5 Therefore, the threshold switch device unit improved by the technology of the present invention is more suitable for practical applications.

[0035] In addition, other process conditions involved in the present invention are conventional process conditions, which are within the scope familiar to those skilled in the art and will not be described in detail here.

[0036] In summary, the present invention x Te y ) a M 1-a The advantages of threshold switch materials, threshold switch device units and preparation methods thereof are as follows:

[0037] 1. Under the action of external energy, (In x Te y ) a M 1-a Threshold switching materials can smoothly realize instantaneous transition between high resistance state and low resistance state. The high resistance state represents the off state, and the low resistance state represents the on state. The transition between high and low resistance states controls the switching of the device.

[0038] 2. In x Te y ) a M 1-a When the threshold switch material is used as the selection medium of the threshold switch device unit, it achieves extremely low leakage current under relatively low threshold voltage conditions, and can also improve the turn-on current and switching ratio of the threshold switch device unit. At the same time, the lower threshold voltage is helpful to effectively improve the reliability and life of the threshold switch device unit.

Claims

1. A threshold gating material, characterized in that: The chemical formula of the threshold gating material is (In 38 Te 62 ) 0.1 (Ge 15 As 35 Se 50 ) 0.9 .

2. A threshold gating device unit, characterized in that: The threshold gating device unit comprises, from bottom to top, a lower electrode layer, a threshold gating material layer as claimed in claim 1, an upper electrode layer, and an extraction electrode arranged on the upper electrode layer.

3. The threshold gating device unit according to claim 2, characterized in that: The material of the lower electrode layer includes at least one of C, W, Cu, Al, Ti, Ta, TiN, WNx, TaN, Pt, Au, Ag, Co, and Ni.

4. The threshold gating device unit according to claim 2, characterized in that: The material of the upper electrode layer includes at least one of W, Cu, Al, C, Ti, Ta, TiN, WNx, TaN, Pt, Au, Ag, Co, and Ni.

5. The threshold gating device unit according to claim 2, characterized in that: The material of the lead-out electrode includes at least one of W, Cu, Al, Co, Pt, Au, and Ag.

6. A method for preparing a threshold gating device unit, comprising the following steps: (1) preparing a lower electrode layer; (2) depositing the threshold gating material layer as claimed in claim 1 on the above-mentioned lower electrode layer; (3) preparing an upper electrode layer on the threshold gating material layer; (4) Prepare lead electrodes on the upper electrode layer.

7. The preparation method according to claim 6, characterized in that: The preparation is carried out by sputtering, evaporation, chemical vapor deposition, plasma enhanced chemical vapor deposition, low pressure chemical vapor deposition, metal compound vapor deposition, molecular beam epitaxy, atomic vapor deposition or atomic layer deposition.

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