Phase change unit and preparation method thereof
By introducing a low thermal conductivity non-conductor film layer with voids and reduced gradient Ge and Te element concentrations in phase change storage technology, the reliability reduction problem caused by element migration in phase change units is solved, and the effect of improving device reliability and reducing power consumption is achieved.
Patent Information
- Application Number
- CN202311228036.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-09-21
- Publication Date
- 2025-03-28
AI Technical Summary
In the existing phase change storage technology, during repeated phase change operations of small-size restricted phase change units, elements will migrate, resulting in element segregation and voiding, resulting in reduced device reliability.
By forming a low thermal conductivity non-conductor film layer with a gap between the bottom electrode and the phase change resistor, the electric field strength is reduced, and the concentration of Ge and Te elements is reduced in the phase change resistor in the direction away from the bottom electrode, thereby reducing the element mobility.
Effectively reduce element segregation in phase change units, improve device reliability and thermal stability, and reduce device power consumption.
Smart Images
Figure CN119730708A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of semiconductor integrated circuit technology, and in particular to a high-reliability phase change unit and a preparation method thereof. Background Art
[0002] In order to meet the needs of future application scenarios such as unmanned driving, face recognition, and intelligent robots, it is an inevitable trend to develop large-capacity, high-reliability, and high-efficiency memory chips. New memory technologies such as phase change memory and resistive memory can greatly improve the energy efficiency and data processing scale of chips. Among them, phase change memory is the most mature new memory device with the greatest hope of breaking through the practical barriers.
[0003] The existing phase change storage technology, especially for small size restricted phase change units, as the number of device operations increases, during repeated phase change operations, the elements in the phase change film will migrate, causing a certain degree of element segregation (such as the tellurium element in the phase change film migrating toward the top electrode), and even forming voids, which will lead to reduced device reliability or even failure. The common solutions are:
[0004] (1) Improve the circuit design by using reverse electric pulses to reset the distribution of elements after the device has been operated a certain number of times. However, the circuit design required for this method is very complex and difficult to apply on a large scale.
[0005] (2) The method of alternately stacking superlattice phase change films and barrier layers is used to prevent the segregation and drift of phase change film elements. However, this method is prone to cause stress mismatch between films and bring about the problem of high device power consumption. Summary of the invention
[0006] The purpose of the present invention is to overcome the above-mentioned defects in the prior art and to provide a phase change unit and a preparation method thereof.
[0007] To achieve the above object, the technical solution of the present invention is as follows:
[0008] The present invention provides a phase change unit, comprising:
[0009] A bottom electrode, a non-conductor film layer, a phase change resistor and a top electrode connected in sequence;
[0010] The non-conductor film layer has a gap, and the phase change resistor passes through the gap and is connected to the bottom electrode.
[0011] Furthermore, the non-conductor film layer is formed by a plurality of non-conductor bumps; wherein the non-conductor bumps are arranged on the surface of the bottom electrode in a manner of being separated from each other or at least partially connected into a network to form the gap on the non-conductor film layer.
[0012] Furthermore, the thermal conductivity of the non-conductive film layer material is less than or equal to 10-60 W / mK; and / or the non-conductive film layer material has stable chemical properties below 500° C.; and / or the non-conductive film layer material includes a dielectric, a metal oxide or an organic matter.
[0013] Furthermore, the phase change resistor material contains Ge and Te elements, and the concentrations of the Ge and Te elements in the phase change resistor gradually decrease or decrease in a gradient along a direction away from the bottom electrode.
[0014] Furthermore, the phase change resistor includes multiple layers of phase change films stacked in sequence in a direction away from the bottom electrode, and is connected to the bottom electrode through a bottom phase change film adjacent to the non-conductor film layer passing through the gap, and is connected to the top electrode through a top phase change film, and the phase change film material contains Ge and Te elements; wherein the concentrations of the Ge and Te elements gradually decrease in the multiple layers of the phase change films in a direction away from the bottom electrode, or the concentrations of the Ge and Te elements gradually decrease between each layer of the phase change films in a direction away from the bottom electrode.
[0015] Furthermore, it also includes a substrate, on which a dielectric layer is provided, the bottom electrode, the non-conductor film layer, the phase change resistor and the top electrode are sequentially stacked on the substrate and located in the dielectric layer, and the bottom electrode is connected to the substrate.
[0016] The present invention also provides a method for preparing a phase change unit, comprising:
[0017] providing a substrate;
[0018] forming a bottom electrode on the surface of the substrate;
[0019] forming a non-conductor film layer having gaps on the surface of the bottom electrode;
[0020] forming a phase change resistor on the surface of the non-conductor film layer, so that a portion of the phase change resistor fills the gap and is connected to the surface of the bottom electrode;
[0021] A top electrode is formed on a surface of the phase change resistor.
[0022] Furthermore, by controlling the formation time of the non-conductor film layer, the non-conductor film layer is placed in a discontinuous film forming state at the initial stage of nucleation to form a plurality of the non-conductor protrusions serving as nucleation cores, so that the formed non-conductor protrusions are separated from each other, or at least partially connected into a network, thereby forming the non-conductor film layer having the gaps.
[0023] Furthermore, one or more phase change films containing Ge and Te elements are used to form the phase change resistor; wherein, during the formation of the phase change film, the process addition amounts of the Ge and Te elements are adjusted to be continuously or abruptly reduced, so that the concentrations of the Ge and Te elements in the formed phase change resistor gradually decrease or decrease in a gradient along the direction away from the bottom electrode, or the concentrations of the Ge and Te elements are gradually reduced along the direction away from the bottom electrode between the multiple layers of the phase change films.
[0024] Furthermore, the method of forming the bottom electrode, the non-conductor film layer, the phase change resistor and the top electrode specifically includes:
[0025] forming a first dielectric layer on the substrate;
[0026] forming a bottom electrode groove on the surface of the first dielectric layer, stopping on the surface of the substrate;
[0027] Filling the bottom electrode groove to form a bottom electrode connected to the surface of the substrate;
[0028] Forming a plurality of non-conductor bumps in the early stage of nucleation on the surfaces of the first dielectric layer and the bottom electrode to form a non-conductor film layer with discontinuous distribution and gaps;
[0029] Forming one or more phase change films containing Ge and Te elements on the surface of the non-conductor film layer, so that the bottom of the phase change film passes through the gap and is connected to the bottom electrode, and the concentrations of the Ge and Te elements decrease in a direction away from the bottom electrode;
[0030] Patterning the phase change film to form a phase change resistor on the surface of the non-conductor film layer, the bottom of which is connected to the bottom electrode;
[0031] forming a second dielectric layer on the surface of the first dielectric layer to cover the non-conductor film layer and the phase change resistor;
[0032] forming a top electrode groove on the surface of the second dielectric layer, stopping on the top surface of the phase change resistor;
[0033] The top electrode trench is filled to form a top electrode connected to the phase change resistor.
[0034] It can be seen from the above technical scheme that the present invention forms a non-conductor film layer with low thermal conductivity and gaps between the bottom electrode and the phase change resistor, which is beneficial to reducing the electric field strength at the interface between the bottom electrode and the phase change material, thereby effectively reducing the mobility of the elements (such as Ge, Te) at the bottom of the phase change material toward the top electrode, and at the same time reducing the contact area between the phase change material and the bottom electrode, thereby increasing the heating efficiency and reducing the power consumption of the device. In addition, by decreasing the concentration of Ge and Te elements contained in the phase change material in the direction away from the bottom electrode, the impact of subsequent migration of Ge and Te to the top electrode on the device performance can be reduced; at the same time, the high content of Ge near the bottom electrode is also helpful to improve the thermal stability of the device. Therefore, the present invention has the comprehensive advantages of being able to effectively reduce the problem of segregation of phase change film elements in the phase change unit, improve the reliability and thermal stability of the device, and reduce the power consumption of the device. BRIEF DESCRIPTION OF THE DRAWINGS
[0035] Figure 1 The figure is a schematic structural diagram of a phase change unit according to a preferred embodiment of the present invention.
[0036] Figure 2-Figure 7 The figure is a schematic diagram of the process steps of a method for preparing a phase change unit according to a preferred embodiment of the present invention. DETAILED DESCRIPTION
[0037] In order to make the purpose, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention. Unless otherwise defined, the technical terms or scientific terms used herein should be understood by people with general skills in the field to which the present invention belongs. "Including" and similar words used in this article mean that the elements or objects appearing before the word include the elements or objects listed after the word and their equivalents, without excluding other elements or objects.
[0038] The specific implementation modes of the present invention are further described in detail below in conjunction with the accompanying drawings.
[0039] refer to Figure 1 A phase change unit of the present invention comprises: a bottom electrode 103, a non-conductor film layer 104, a phase change resistor 106 and a top electrode 108 which are sequentially arranged and connected on a substrate 101. The non-conductor film layer 104 has a gap 110, and the phase change resistor 106 passes through the gap 110 and is connected to the bottom electrode 103.
[0040] In some embodiments, the non-conductive film layer 104 is formed of a plurality of non-conductive bumps 1041 , and gaps 110 are formed between the non-conductive bumps 1041 .
[0041] In some embodiments, the non-conductor bumps 1041 are arranged on the surface of the bottom electrode 103 in a mutually separated manner, forming an island structure of the non-conductor bumps 1041, thereby forming a gap 110 on the non-conductor film layer 104. That is, the non-conductor film layer 104 is composed of a plurality of mutually separated non-conductor bumps 1041. At this time, the gap 110 will be connected into one piece.
[0042] Alternatively, a portion of the non-conductor bumps 1041 are separated from each other to form isolated islands, and another portion is connected to each other to form a network with gaps 110, and are arranged together on the surface of the bottom electrode 103, thereby forming a non-conductor film layer 104 with multiple gaps 110. Multiple non-conductor bumps 1041 can be connected to each other to form larger isolated islands.
[0043] Alternatively, the non-conductor bumps 1041 are interconnected to form an overall network with gaps 110 , and are arranged on the surface of the bottom electrode 103 , thereby forming a non-conductor film layer 104 with a plurality of gaps 110 .
[0044] It can be understood that the sizes of the non-conductor bumps 1041 can be the same or different.
[0045] In some embodiments, the material of the non-conductive film layer 104 has low thermal conductivity, preferably less than or equal to 10-60 W / mK.
[0046] Furthermore, the material of the non-conductive film layer 104 has stable chemical properties at high temperatures, for example, below 500°C.
[0047] The material of the non-conductor film layer 104 includes an insulating material or a semiconductor material. Further, the insulating material or the semiconductor material used for the non-conductor film layer 104 includes a dielectric, a metal oxide or an organic matter. For example, the material of the non-conductor film layer 104 includes silicon nitride.
[0048] In some embodiments, the particle size of the non-conductor bump 1041 when projected on the surface of the substrate 101 is 3 to 8 nm. The height of the non-conductor bump 1041 in a direction perpendicular to the surface of the substrate 101 is 2 to 10 nm. In one example, the particle size of the non-conductor bump 1041 made of silicon nitride material is 3 to 5 nm, and the height is about 2 to 3 nm.
[0049] refer to Figure 1In some embodiments, the phase change resistor 106 is formed by one or more phase change films 105. The multi-layer phase change film 105 may be a stacked structure of 3 to 6 layers. The thickness of each layer of the phase change film 105 may be 5 to 15 nm.
[0050] When the phase change resistor 106 is formed by a layer of phase change film 105, the thickness of the phase change film 105 is greater than the thickness of the non-conductor film layer 104 (the height of the non-conductor bump 1041); the bottom of the phase change film 105 is filled into the gap 110 of the non-conductor film layer 104, so that the phase change resistor 106 forms an ohmic connection with the bottom electrode 103.
[0051] When the phase change resistor 106 is formed by a multi-layer phase change film 105, for example Figure 1 The phase change resistor 106 shown is formed by three layers of phase change films 105, namely, a bottom phase change film 1051, an intermediate phase change film 1052 and a top phase change film 1053 stacked in sequence from bottom to top. The thickness of each phase change film 105 is 10 nm, and the thickness of the bottom phase change film 1051 is greater than the thickness of the non-conductor film layer 104 (the height of the non-conductor bump 1041); the bottom of the bottom phase change film 1051 is filled into the gap 110 of the non-conductor film layer 104, so that the phase change resistor 106 forms an ohmic connection with the bottom electrode 103; the phase change resistor 106 forms an ohmic connection with the top electrode 108 through the top phase change film 1053.
[0052] In some embodiments, the phase change resistor 106 (phase change film 105) material contains Ge and Te elements. For example, the phase change resistor 106 material can be a GeTe-Sb2Te3 system, or a GeTe-Sb2Te3 system doped with Sc, Ag, In, Al, C, S, Se, N, Cu, and W elements. In one example, the phase change resistor 106 (phase change film 105) material is Ge2Sb2Te5 doped with C.
[0053] In some embodiments, when the phase change resistor 106 is formed by one or more phase change films 105 , the concentrations of Ge and Te contained in the phase change resistor 106 material gradually decrease or decrease in a gradient in a direction away from the bottom electrode 103 .
[0054] In some embodiments, when the phase change resistor 106 is formed by a multilayer phase change film 105, the concentration of Ge and Te elements contained in the phase change resistor 106 material gradually decreases in the multilayer phase change film 105 in a direction away from the bottom electrode 103; or, the concentration of Ge and Te elements gradually decreases between each layer of phase change film 105 in a direction away from the bottom electrode 103.
[0055] In some embodiments, when the concentrations of Ge and Te elements decrease in a gradient in the phase change resistor 106 , the gradient change rate of the concentrations of Ge and Te elements is 3-10%.
[0056] refer to Figure 1 In some embodiments, a dielectric layer 109 is disposed on the substrate 101 , and the bottom electrode 103 , the non-conductive film layer 104 , the phase change resistor 106 and the top electrode 108 are sequentially stacked on the substrate 101 and located in the dielectric layer 109 .
[0057] Further, the dielectric layer 109 includes a first dielectric layer 102 and a second dielectric layer 107. The first dielectric layer 102 is located on the surface of the substrate 101, the bottom electrode 103 is located in the first dielectric layer 102, and the bottom of the bottom electrode 103 is connected to the substrate 101, and the top surface of the bottom electrode 103 is exposed from the surface of the first dielectric layer 102 and is flush with the surface of the first dielectric layer 102. The second dielectric layer 107 is located on the surface of the first dielectric layer 102, the non-conductor film layer 104, the phase change resistor 106 and the top electrode 108 are located in the second dielectric layer 107, and the top surface of the top electrode 108 is exposed from the surface of the second dielectric layer 107 and is flush with the surface of the second dielectric layer 107.
[0058] In some embodiments, the substrate 101 includes a semiconductor material, such as a silicon substrate 101, a gallium arsenide substrate 101, a germanium substrate 101, a germanium silicon substrate 101, or a fully depleted silicon on insulator (FDSOI) substrate 101. The substrate 101 may also be an integrated circuit, including an integrated circuit having a gate transistor such as a triode, a diode, and the like.
[0059] The material of the bottom electrode 103 and / or the top electrode 108 may be at least one of Ti, W, Ta, Cu, WCN, WN, TaN, etc. In one example, the material of the bottom electrode 103 is W, and the material of the top electrode 108 is a Cu wire.
[0060] The dielectric layer 109 may be made of silicon oxide, silicon nitride, low-K material, etc.
[0061] In some embodiments, the projection of the phase change resistor 106 on the surface of the substrate 101 may be linear, circular, elliptical, etc., and the minimum size of the phase change resistor 106 in each projection direction is greater than or equal to the size of the bottom electrode 103, that is, the bottom electrode 103 is completely covered. In this embodiment, the projection of the phase change resistor 106 on the surface of the substrate 101 is circular, that is, the phase change resistor 106 is cylindrical, and completely covers the bottom electrode 103 whose projection is also circular.
[0062] In some embodiments, the projection of the top electrode 108 on the surface of the substrate 101 may be linear, circular, elliptical, etc.
[0063] A method for preparing a phase change unit of the present invention is further described in detail below through specific implementation modes and in conjunction with the accompanying drawings.
[0064] refer to Figure 2-Figure 7 The phase change unit preparation method of the present invention can be used to prepare, for example Figure 1 A phase change unit of the present invention is shown, and may include the following steps:
[0065] Step S1: providing a substrate 101 .
[0066] like Figure 2 As shown, a silicon substrate 101 is used, and a first dielectric layer 102 made of, for example, silicon dioxide is deposited on the surface of the silicon substrate 101 .
[0067] Step S2 : forming a bottom electrode 103 on the surface of the substrate 101 .
[0068] like Figure 2 As shown, then, a bottom electrode 103 groove is formed on the surface of the first dielectric layer 102 by using photolithography and etching processes, and stops on the surface of the substrate 101. The bottom electrode 103 groove is, for example, a circular through-hole groove.
[0069] Next, the bottom electrode 103 trench may be filled with, for example, tungsten metal and planarized to form a tungsten through-hole type bottom electrode 103 connected to the surface of the substrate 101 .
[0070] Step S3 : forming a non-conductor film layer 104 having gaps 110 on the surface of the bottom electrode 103 .
[0071] like Figure 3 As shown, a non-conductor film layer 104 is prepared on the surface of the first dielectric layer 102 and the bottom electrode 103 by chemical vapor deposition, atomic layer deposition or solution spin coating. By controlling the film forming time of the non-conductor film layer 104, the formed non-conductor film layer 104 is in a discontinuous film forming state at the initial stage of nucleation, so as to form a plurality of non-conductor bumps 1041 as nucleation cores. And the formed non-conductor bumps 1041 can be separated from each other, or at least partially connected into a network, so as to form a non-conductor film layer 104 with gaps 110. In this embodiment, chemical vapor deposition is used to form a non-conductor film layer 104 with discontinuous distribution of silicon nitride material and gaps 110 on the surface of the first dielectric layer 102 and the bottom electrode 103, so that the formed non-conductor film layer 104 is a plurality of non-conductor bumps 1041 at the initial stage of nucleation, and the particle size of the non-conductor bumps 1041 is 3-5nm, and the height is about 2nm.
[0072] By forming discontinuous low thermal conductivity non-conductor bumps 1041 on the bottom electrode 103, the phase change material layer elements in contact with the bottom electrode 103 can be reinforced, which is beneficial to reducing the electric field strength at the interface between the bottom electrode 103 and the phase change material, effectively reducing the mobility of the Te element at the bottom of the phase change material, preventing interface voids caused by element segregation, and increasing the reliability of the device. At the same time, the introduction of the non-conductor bumps 1041 reduces the contact area between the phase change material and the bottom electrode 103, which can increase the heating efficiency and reduce the power consumption of the device.
[0073] Step S4 : forming a phase change resistor 106 on the surface of the non-conductive film layer 104 , so that a portion of the phase change resistor 106 fills the gap 110 and is connected to the surface of the bottom electrode 103 .
[0074] like Figure 4 As shown, a multilayer phase change film 105 containing Ge and Te elements is deposited on the surface of the non-conductor film layer 104, so that the bottom of the phase change film 105 passes through the gap 110 of the non-conductor film layer 104 to connect with the bottom electrode 103, and the concentration of the Ge and Te elements decreases in the direction away from the bottom electrode 103. In this embodiment, a three-layer phase change film 105 of Ge2Sb2Te5 material doped with C is formed, which has a bottom phase change film 1051, an intermediate phase change film 1052 and a top phase change film 1053, and the thickness of each layer of phase change material is 10nm. The bottom of the bottom phase change film 1051 passes through the gap 110 of the non-conductor film layer 104 to connect with the bottom electrode 103. During the formation of the three-layer phase change film 105, the process addition amount of Ge and Te elements is adjusted to decrease continuously or abruptly, so that the concentration of Ge and Te elements in the formed phase change resistor 106 (i.e., the whole of the three-layer phase change film 105) gradually decreases or decreases in a gradient along the direction away from the bottom electrode 103; or, the concentration of Ge and Te elements is decreased in a gradient along the direction away from the bottom electrode 103 between the multi-layer phase change films 105. For example, by adjusting the process addition amount of Ge and Te elements to decrease abruptly, the concentration of Ge in the formed bottom phase change film 1051, the middle phase change film 1052, and the top phase change film 1053 can be 1.1, 1.05, and 1, respectively, and the concentration of Te can be 1.2, 1.1, and 1, respectively. In this way, the atomic mass ratio of Ge, Sb, and Te in the top phase change film 1053 can be 2:2:5. It can be seen that the Ge content and Te content of the bottom phase change film 1051 in contact with the bottom electrode 103 and the non-conductor film layer 104 are the highest. Among them, the high Te content here can effectively reduce the influence of the migration of Te and Ge elements at the bottom of the phase change material to the top electrode 108, solve the problem of element segregation in the phase change film 105 of the phase change unit, and improve the reliability of the device. At the same time, the high Ge content in the bottom phase change film 1051 can improve the thermal stability of the device.
[0075] like Figure 5 As shown, the phase change film 105 and the non-conductor film layer 104 are patterned by photolithography and etching processes, and a phase change resistor 106 whose bottom is connected to the bottom electrode 103 is formed on the surface of the non-conductor film layer 104. In this embodiment, a cylindrical phase change resistor 106 having three layers of phase change film 105 is formed, and the circular non-conductor film layer 104 and the circular tungsten through-hole bottom electrode 103 below are completely covered.
[0076] Step S5 : forming a top electrode 108 on the surface of the phase change resistor 106 .
[0077] like Figure 6 As shown, a second dielectric layer 107 such as silicon dioxide is deposited on the surface of the first dielectric layer 102 to cover the non-conductor film layer 104 and the phase change resistor 106, and the surface of the second dielectric layer 107 is flattened so that the surface of the flattened second dielectric layer 107 is higher than the top surface of the phase change resistor 106. The second dielectric layer 107 and the first dielectric layer 102 together form a Figure 1 The dielectric layer 109 in the.
[0078] like Figure 7 As shown, a top electrode 108 groove is formed on the surface of the second dielectric layer 107 by photolithography and etching processes, and stops on the top surface of the phase change resistor 106 .
[0079] Next, the top electrode 108 trench may be filled with, for example, Cu metal and planarized to form a Cu wire-type top electrode 108 whose bottom is connected to the top surface of the phase change resistor 106 .
[0080] In summary, the present invention forms a non-conductor film layer 104 with low thermal conductivity and a gap 110 between the bottom electrode 103 and the phase change resistor 106, which is conducive to reducing the electric field strength at the interface between the bottom electrode 103 and the phase change material, thereby effectively reducing the mobility of the elements (such as Ge, Te) at the bottom of the phase change material toward the top electrode 108, and at the same time reducing the contact area between the phase change material and the bottom electrode 103, thereby increasing the heating efficiency and reducing the power consumption of the device. In addition, by decreasing the concentration of Ge and Te elements contained in the phase change material in the direction away from the bottom electrode 103, the impact on the device performance caused by the subsequent migration of Ge and Te to the top electrode 108 can be reduced; at the same time, the high content of Ge near the bottom electrode 103 is also helpful to improve the thermal stability of the device. Therefore, the present invention has the comprehensive advantages of being able to effectively reduce the problem of element segregation of the phase change film 105 in the phase change unit, improve the reliability and thermal stability of the device, and reduce the power consumption of the device.
[0081] Although the embodiments of the present invention are described in detail above, it is obvious to those skilled in the art that various modifications and variations can be made to these embodiments. However, it should be understood that such modifications and variations are within the scope and spirit of the present invention as described in the claims. Moreover, the present invention described herein may have other embodiments and may be implemented or realized in a variety of ways.
Claims
1. A phase change unit, characterized in that: include: A bottom electrode, a non-conductor film layer, a phase change resistor and a top electrode connected in sequence; The non-conductor film layer has a gap, and the phase change resistor passes through the gap and is connected to the bottom electrode.
2. The phase change unit according to claim 1, characterized in that: The non-conductor film layer is formed by a plurality of non-conductor bumps, wherein the non-conductor bumps are arranged on the surface of the bottom electrode in a form of being separated from each other or at least partially connected into a network, so as to form the gap on the non-conductor film layer.
3. The phase change unit according to claim 1, characterized in that: The thermal conductivity of the non-conductive film layer material is less than or equal to 10-60 W / mK; and / or the non-conductive film layer material has stable chemical properties below 500° C.; and / or the non-conductive film layer material includes a dielectric, a metal oxide or an organic matter.
4. The phase change unit according to claim 1, characterized in that: The phase change resistor material contains Ge and Te elements, and the concentrations of the Ge and Te elements in the phase change resistor gradually decrease or decrease in a gradient along a direction away from the bottom electrode.
5. The phase change unit according to claim 1, characterized in that: The phase change resistor includes multiple layers of phase change films stacked in sequence in a direction away from the bottom electrode, and is connected to the bottom electrode through a bottom phase change film adjacent to the non-conductor film layer passing through the gap, and is connected to the top electrode through a top phase change film, and the phase change film material contains Ge and Te elements; wherein the concentrations of the Ge and Te elements gradually decrease in the multiple layers of the phase change films in a direction away from the bottom electrode, or the concentrations of the Ge and Te elements gradually decrease between each layer of the phase change films in a direction away from the bottom electrode.
6. The phase change unit according to claim 1, characterized in that: It also includes a substrate, on which a dielectric layer is provided, the bottom electrode, the non-conductor film layer, the phase change resistor and the top electrode are sequentially stacked on the substrate and located in the dielectric layer, and the bottom electrode is connected to the substrate.
7. A method for preparing a phase change unit, characterized in that: include: providing a substrate; forming a bottom electrode on the surface of the substrate; forming a non-conductor film layer having gaps on the surface of the bottom electrode; forming a phase change resistor on the surface of the non-conductor film layer, so that a portion of the phase change resistor fills the gap and is connected to the surface of the bottom electrode; A top electrode is formed on a surface of the phase change resistor.
8. The method for preparing a phase change unit according to claim 7, characterized in that: By controlling the formation time of the non-conductor film layer, the non-conductor film layer is placed in a discontinuous film forming state at the initial stage of nucleation to form a plurality of the non-conductor protrusions serving as nucleation cores, so that the formed non-conductor protrusions are separated from each other, or at least partially connected into a network, thereby forming the non-conductor film layer having the gaps.
9. The method for preparing a phase change unit according to claim 7, characterized in that: The phase change resistor is formed by using one or more phase change films containing Ge and Te elements; wherein, during the formation of the phase change film, the process addition amounts of the Ge and Te elements are adjusted to be continuously or abruptly reduced, so that the concentrations of the Ge and Te elements in the formed phase change resistor gradually decrease or decrease in a gradient along a direction away from the bottom electrode, or the concentrations of the Ge and Te elements are gradually reduced along a direction away from the bottom electrode between the multiple phase change films.
10. The method for preparing a phase change unit according to claim 7, characterized in that: The method for forming the bottom electrode, the non-conductor film layer, the phase change resistor and the top electrode specifically includes: forming a first dielectric layer on the substrate; forming a bottom electrode groove on the surface of the first dielectric layer, stopping on the surface of the substrate; Filling the bottom electrode groove to form a bottom electrode connected to the surface of the substrate; Forming a plurality of non-conductor bumps in the early stage of nucleation on the surfaces of the first dielectric layer and the bottom electrode to form a non-conductor film layer with discontinuous distribution and gaps; Forming one or more phase change films containing Ge and Te elements on the surface of the non-conductor film layer, so that the bottom of the phase change film passes through the gap and is connected to the bottom electrode, and the concentrations of the Ge and Te elements decrease in a direction away from the bottom electrode; Patterning the phase change film to form a phase change resistor on the surface of the non-conductor film layer, the bottom of which is connected to the bottom electrode; forming a second dielectric layer on the surface of the first dielectric layer to cover the non-conductor film layer and the phase change resistor; forming a top electrode groove on the surface of the second dielectric layer, stopping on the top surface of the phase change resistor; The top electrode trench is filled to form a top electrode connected to the phase change resistor.