JP2009105383A - Variable resistance element and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a variable resistance element capable of achieving stable switching operation with good reproducibility, and a manufacturing method thereof. <P>SOLUTION: On a semiconductor substrate 11, a first electrode 14, a second electrode 17, and a variable resistive element 51 formed between the both electrodes are provided. The variable resistive element 51 is formed of metal oxide or metal oxynitride having an oxygen concentration gradient in a prescribed gradient direction d1, wherein a first connection region 14x electrically connecting the first electrode 14 and variable resistive element 51 to each other and a second connection region 17x electrically connecting the second electrode 17 and variable resistive element 51 to each other are formed apart from each other in a direction d2 orthogonal to the gradient direction d1. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention includes a first electrode, a second electrode, and a variable resistor formed between the two electrodes, and an electric resistance between the two electrodes is increased according to application of a voltage pulse between the two electrodes. The present invention relates to a reversible variable resistance element and a method for manufacturing the same.

  In recent years, various devices such as next-generation non-volatile random access memory (NVRAM: Nonvolatile Random Access Memory) capable of operating at high speed instead of flash memory include FeRAM (Ferroelectric RAM), MRAM (Magnetic RAM), and PRAM (Phase Change RAM). A structure has been proposed, and intense development competition has been conducted from the viewpoint of high performance, high reliability, low cost, and process consistency. However, each of these current memory devices has advantages and disadvantages, and it is still far from the ideal realization of a “universal memory” having the advantages of SRAM, DRAM, and flash memory.

  For these existing technologies, a resistive non-volatile memory RRAM (Resistive Random Access Memory) (registered trademark) using a variable resistive element whose electric resistance reversibly changes by applying a voltage pulse has been proposed. This configuration is shown in FIG.

  As shown in FIG. 27, the variable resistance element of the conventional configuration has a structure in which a lower electrode 103, a variable resistor 102, and an upper electrode 101 are sequentially stacked, and a voltage is applied between the upper electrode 101 and the lower electrode 103. By applying a pulse, the resistance value can be reversibly changed. A novel nonvolatile semiconductor memory device can be realized by reading a resistance value that changes by this reversible resistance change operation (hereinafter referred to as “switching operation”).

  In this nonvolatile semiconductor memory device, a plurality of memory cells including variable resistance elements are arranged in a matrix in the row direction and the column direction to form a memory cell array, and data is written to each memory cell in the memory cell array. Peripheral circuits for controlling erase and read operations are arranged. As the memory cell, a memory cell is composed of one selection transistor T and one variable resistance element R (referred to as “1T / 1R type”) because of the difference in its constituent elements. There are cells, memory cells composed of only one variable resistance element R (referred to as “1R type”), and the like. Of these, FIG. 28 shows a configuration example of a 1T / 1R type memory cell.

  FIG. 28 is an equivalent circuit diagram showing a configuration example of a memory cell array including 1T / 1R type memory cells. The gate of the selection transistor T of each memory cell is connected to the word lines (WL1 to WLn), and the source of the selection transistor T of each memory cell is connected to the source lines (SL1 to SLn) (n is a natural number). . One electrode of the variable resistance element R for each memory cell is connected to the drain of the selection transistor T, and the other electrode of the variable resistance element R is connected to the bit lines (BL1 to BLm) (m Is a natural number). The word lines WL1 to WLn are connected to the word line decoder 106, the source lines SL1 to SLn are connected to the source line decoder 107, and the bit lines BL1 to BLm are connected to the bit line decoder 105, respectively. Yes. A specific bit line, word line, and source line for writing, erasing, and reading operations to specific memory cells in the memory cell array 104 are selected in accordance with an address input (not shown).

  FIG. 29 is a schematic cross-sectional view of one memory cell constituting the memory cell array 104 in FIG. In this configuration, the select transistor T and the variable resistance element R form one memory cell. The selection transistor T includes a gate insulating film 113, a gate electrode 114, a drain diffusion layer region 115, and a source diffusion layer region 116, and is formed on the upper surface of the semiconductor substrate 111 on which the element isolation region 112 is formed. The variable resistance element R includes a lower electrode 118, a variable resistor 119, and an upper electrode 120.

  Further, the gate electrode 114 of the transistor T forms a word line, and the source line wiring 124 is electrically connected to the source diffusion layer region 116 of the transistor T through the contact plug 122. The bit line wiring 123 is electrically connected to the upper electrode 120 of the variable resistance element R through the contact plug 121, while the lower electrode 118 of the variable resistance element R is connected to the transistor T through the contact plug 117. The drain diffusion layer region 115 is electrically connected.

  As described above, the selection transistor T and the variable resistance element R are arranged in series, so that the transistor of the memory cell selected by the change in the potential of the word line is turned on, and the memory selected by the change in the potential of the bit line. The cell can be selectively written or erased only to the variable resistance element R of the cell.

  FIG. 30 is an equivalent circuit diagram illustrating a configuration example of a 1R type memory cell. Each memory cell includes only the variable resistance element R, and one electrode of the variable resistance element R is connected to the word lines (WL1 to WLn) and the other electrode is connected to the bit lines (BL1 to BLm). The word lines WL1 to WLn are connected to the word line decoder 133, and the bit lines BL1 to BLm are connected to the bit line decoder 132, respectively. A specific bit line and word line for writing, erasing and reading operations to specific memory cells in the memory cell array 131 are selected in accordance with an address input (not shown).

  FIG. 31 is a schematic perspective view showing an example of a memory cell constituting the memory cell array 131 in FIG. As shown in FIG. 31, the upper electrode wiring 143 and the lower electrode wiring 141 are arranged so as to cross each other, one of which forms a bit line and the other forms a word line. In addition, the variable resistor 142 is arranged at the intersection (usually referred to as “cross point”) of each electrode. In the example of FIG. 31, for convenience, the upper electrode 143 and the variable resistor 142 are processed into the same shape, but the portions that contribute electrically to the switching operation of the variable resistor 142 are the upper electrode 143 and the lower electrode 141. It becomes the area of crossing points.

Note that the variable resistor material used for the variable resistor 119 in FIG. 28 or the variable resistor 142 in FIG. 30 is known by the giant magnetoresistive effect by Shanqing Liu, Alex Ignatiev, etc. of the University of Houston, USA. The following Patent Document 1 and Non-Patent Document 1 disclose a method for reversibly changing the electric resistance by applying a voltage pulse to the perovskite material. Although this method uses a perovskite material known for its giant magnetoresistive effect, this method is extremely epoch-making in that a resistance change of several orders of magnitude appears even at room temperature without applying a magnetic field. In the element structure exemplified in Patent Document 1, a crystalline praseodymium / calcium / manganese oxide Pr _1-x Ca _x MnO ₃ (PCMO) film, which is a perovskite oxide, is used as a variable resistor material. Yes.

Other variable resistor materials include oxides of transition metal elements such as titanium oxide (TiO ₂ ) films, nickel oxide (NiO) films, zinc oxide (ZnO) films, and niobium oxide (Nb ₂ O ₅ ) films. It is known from Non-Patent Document 2 and Patent Document 2 that reversible resistance change is exhibited. Among these, the phenomenon of the switching operation using NiO is reported in detail in Non-Patent Document 3.

US Pat. No. 6,204,139 JP 2002-537627 A Liu, S .; Q. In addition, “Electric-pulse-induced reversible resistance change effectin magnetosensitive films”, Applied Physics Letter, Vol. 76, pp. 2749-2751, 2000 H. Pagna, et al., “Bistable Switching in Electroformed Metal-Insulator-Metal Devices”, Phys. Stat. Sol. (A), vol. 108, pp. 11-65, 1988 Baek, I. et al. G. In addition, “Highly Scalable Non-volatile Resistive Memory Using Simple Binary Oxide Driven Asymmetric Universal Voltage Pulses”, EDDM 2004, pp. 197 587-590, 2004

  According to each of the conventional techniques described above, the element structure is a variable resistance element having a laminated structure in which a lower electrode, a variable resistor, and an upper electrode are formed in this order on a substrate. As for the resistance change of the element, a region (hereinafter referred to as a “filament path”) in which the resistivity is locally reduced is formed in the variable resistor due to the heat rise caused by the current flowing into the variable resistance element, depending on the voltage pulse application condition. Or the fact that the filament path is disassembled is considered to be based on a phenomenon of low resistance or high resistance.

  That is, since the resistance value depends on the formation of the filament path, the resistance value fluctuates due to the change of the filament path diameter and the filament density due to the increase in the number of switching operations. There are problems such as not being able to be seen, and resistance value control is difficult.

  In order to obtain a switching operation, it is necessary to first form a filament path (hereinafter referred to as a “forming process”) by applying a voltage that requires a voltage larger than that of a normal switching operation. In this forming process, for example, if the variable resistor is made of a metal oxide, a voltage several times to 10 times higher than the normal operating voltage is applied to the metal oxide, which is essentially an insulator, for a certain time or more. It is considered that this is realized by forming a current path in the insulator forcibly. This occurs because the element before forming is basically an insulator, or at least a part of the current path such as near the electrode interface is originally an insulator.

  That is, since this forming process is a process of forcibly forming a current path in the insulator, the electrical characteristics of the variable resistance element realized through such a process become unstable. Resistance value control may be made more difficult.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a variable resistance element capable of achieving a stable switching operation with good reproducibility and a method for manufacturing the same.

  In order to achieve the above object, a variable resistance element according to the present invention includes a first electrode, a second electrode, and a variable resistor formed between the two electrodes on a semiconductor substrate, and the gap between the two electrodes. A variable resistance element in which an electrical resistance between the electrodes changes reversibly in response to application of a voltage pulse to the first connection region for electrically connecting the first electrode and the variable resistor; A second connection region for electrically connecting the second electrode and the variable resistor is formed to be spaced apart in a predetermined first direction, and the variable resistor is orthogonal to the first direction. The first feature is that it is made of a metal oxide or metal oxynitride having an oxygen concentration gradient in the direction in which it is formed.

  When the variable resistor is made of a metal oxide or metal oxynitride having an oxygen concentration gradient in a predetermined direction, the concentration of the metal component has a gradient in accordance with the gradient of the oxygen concentration. That is, the region having a high oxygen concentration is in a high resistance state because the concentration of the metal component is low, whereas the region having a low oxygen concentration has a relatively high metal concentration and is not so high as to be an insulator. In other words, in the variable resistor body, a region having a relatively high resistance state (hereinafter referred to as “high resistance region”) and a region having a lower resistance state (hereinafter referred to as “low resistance region”). Will exist.

  The high resistance region exists in a region having a high oxygen concentration in the variable resistor, while the low resistance region exists in a region having a low oxygen concentration. Therefore, it can be seen that the resistance of the variable resistor decreases as the oxygen concentration decreases. In other words, the resistivity in a certain region of the variable resistor is determined by the displacement with respect to the direction in which the oxygen concentration decreases from the position where the oxygen concentration is highest, and is in the direction orthogonal to the direction in which the oxygen concentration decreases, that is, the first Little affected by displacement in one direction.

  Accordingly, the first connection region that electrically connects the first electrode and the variable resistor and the second connection region that electrically connects the second electrode and the variable resistor are spaced apart in the first direction. When formed, since the first direction is a direction orthogonal to the direction in which the oxygen concentration decreases, a variable resistor (low resistance region) having a low resistivity always exists between the two regions. Therefore, when a voltage is applied between both electrodes, a current can flow through the low resistance region existing between the two connection regions. That is, in such a configuration, since a low resistance region, in other words, a region having relatively high conductivity, is formed in the variable resistor in advance, a current path (filament path) is forcibly formed by applying a high voltage. There is no need to perform a forming process.

  Therefore, according to the first characteristic configuration of the variable resistance element according to the present invention, since a current can flow in the variable resistance body without performing the forming process in advance, the electrical characteristics of the variable resistance element by the forming process can be improved. Can be eliminated, and a stable switching operation can be realized.

  At this time, the first direction may be a direction parallel to the substrate surface of the semiconductor substrate, and the variable resistor may have the oxygen concentration gradient in a direction orthogonal to the substrate surface of the semiconductor substrate. . The first direction may be a direction perpendicular to the substrate surface of the semiconductor substrate, and the variable resistor may have the oxygen concentration gradient in a direction parallel to the substrate surface of the semiconductor substrate.

  In the variable resistance element, the variable resistor is made of an oxide or oxynitride of a transition metal containing at least one of Cu, Ni, V, Zn, Nb, Ti, W, Co, and Ta. Can be.

  A variable resistance element manufacturing method according to the present invention is a variable resistance element manufacturing method having the first characteristic configuration described above, wherein the contact structure is formed immediately above a predetermined metal wiring region on the semiconductor substrate. A first step of forming the first electrode, and then a second step of depositing and patterning a predetermined resistive material film as a material of the variable resistor on the entire surface immediately above the first electrode, and thereafter The resistance material film is subjected to an oxidation process, and the oxidation proceeds from the exposed surface of the resistance material film toward the inner side, so that an oxygen concentration gradient is provided in a direction perpendicular to the substrate surface of the semiconductor substrate. A third step of changing to the variable resistor, and then forming the second electrode having a contact structure in contact with the variable resistor in a predetermined region except above the formation region of the first electrode. 4th process , The first, comprising a.

  In the oxidation treatment according to the third step, a variable resistor having an oxygen concentration gradient in the direction of progress of oxidation is formed. In the third step, the oxidation proceeds inward from the exposed surface, so that the oxidation proceeds in a direction orthogonal to the semiconductor substrate surface at almost all portions of the resistive material film. Therefore, by forming the second electrode in a predetermined region except above the region where the first electrode is formed, both electrodes are formed apart from each other in a direction parallel to the semiconductor substrate surface. This means that the first electrode and the second electrode are formed apart from each other in the direction (the first direction) perpendicular to the direction having the oxygen concentration gradient of the variable resistor. Therefore, according to the first feature of the method of manufacturing a variable resistance element according to the present invention, the variable resistance element is manufactured in a state in which a region having relatively high conductivity exists in advance between both connection regions. A variable resistance element exhibiting switching characteristics can be realized without performing a process.

  The variable resistance element manufacturing method according to the present invention, in addition to the first feature, at least above the first electrode formation region after the second step and before the start of the third step. The resistance material film is thinned to have a fifth step of providing a step in the resistance material film, and the third step is equivalent to the film thickness of the resistance material film thinned by the fifth step. Is oxidized, so that the resistance material film in the region not thinned by the fifth step is partially left unoxidized, and the fourth step is the unoxidized resistor. A second feature is a step of forming the second electrode of a contact structure so as to be in contact with the unoxidized resistive material film in a region where the material film exists.

  In addition to the first feature, the variable resistance element manufacturing method according to the present invention includes at least a region above the first electrode formation region after the first step and before the start of the second step. Forming a predetermined conductive film in a region to be removed, thereby providing a sixth step of providing a step between the formation region and the non-formation region of the conductive film, and the second step includes a surface having the step. The resist material film is deposited on the entire surface and then patterned, and the fourth step is performed on the conductive film in a region where the conductive film is formed immediately below the variable resistor. A third feature is a step of forming the second electrode having a contact structure so as to be in contact with each other.

  In addition to the third feature, the variable resistance element manufacturing method according to the present invention includes a step interlayer between the sixth step and the conductive film formation region immediately after the first step. Forming the conductive film after forming an insulating film, and forming a step between the conductive film forming region and the conductive film non-forming region by the step interlayer insulating film and the conductive film. The fourth feature is that it is a step of providing.

  A variable resistance element manufacturing method according to the present invention is a variable resistance element manufacturing method having the first characteristic configuration, wherein a predetermined resistance material film to be a material of the variable resistor is deposited on the entire surface. A first step of patterning, and thereafter, an oxidation treatment is performed on the resistive material film, and the oxidation proceeds from the exposed surface of the resistive material film toward the inside, thereby forming a substrate surface of the semiconductor substrate. A second step of changing to the variable resistor having a gradient of oxygen concentration in a vertical direction, and thereafter, the contacts are spaced apart in a direction parallel to the substrate surface of the semiconductor substrate so as to contact the variable resistor. And a third step of forming the second electrode of the structure and the second electrode of the contact structure.

  According to the fifth feature of the variable resistance element manufacturing method according to the present invention, the first electrode and the second electrode are formed apart from each other in a direction parallel to the semiconductor substrate. That is, the direction parallel to the semiconductor substrate corresponds to the first direction. On the other hand, the variable resistor is formed with an oxygen concentration gradient in a direction perpendicular to the substrate surface of the semiconductor substrate. Therefore, as in the first feature of the method for manufacturing a variable resistance element according to the present invention, the variable resistor has an oxygen concentration gradient in a direction orthogonal to the first direction. As a result, the variable resistance element is manufactured in a state in which a region having relatively high conductivity exists in advance between both connection regions, and a variable resistance element exhibiting switching characteristics can be realized without performing a forming process.

  A variable resistance element manufacturing method according to the present invention is a variable resistance element manufacturing method having the first characteristic configuration described above, and a plurality of metal wirings formed apart from each other in a direction parallel to the semiconductor substrate. A first step of forming the first electrode of the contact structure and the second electrode of the contact structure on the layer immediately above the region, and then a predetermined resistance to be the material of the variable resistor on the layer immediately above the first electrode A second step of depositing and patterning a material film on the entire surface, and then performing an oxidation treatment on the resistive material film, and proceeding oxidation inward from the exposed surface of the resistive material film, And a third step of changing to the variable resistor having an oxygen concentration gradient in a direction perpendicular to the surface of the semiconductor substrate.

  In addition to the sixth feature, the variable resistance element manufacturing method according to the present invention includes the first electrode formation region and the first electrode after the second step and before the third step. The resistance material having a fourth step of thinning the resistive material film located in a predetermined region sandwiched above the formation region of the second electrode, wherein the third step is thinned by the fourth step The step corresponding to the film thickness of the film is oxidized to leave a part of the resistance material film in the region that has not been thinned by the fourth step in an unoxidized state. By changing the thickness of the resistive material film thinned in the third step to an amount corresponding to the film thickness, the variable resistance body having an oxygen concentration gradient in a direction perpendicular to the substrate surface of the semiconductor substrate is obtained. And not thinned by the third step. The resistance material film in the region is partially left unoxidized, so that the resistance material film remaining immediately above the first electrode and the resistance remaining directly above the second electrode A seventh feature is that the material film is divided by the variable resistor.

  In addition to the sixth feature, the variable resistance element manufacturing method according to the present invention includes the first electrode and the second electrode after the first step and before the second step. By depositing a predetermined conductive film directly on the upper layer and patterning it, the conductive film is divided into a region in contact with the first electrode and a region in contact with the second electrode, and a region where the conductive film is formed A fifth step of providing a step between the formation region and the second step is a step of patterning after depositing the resistive material film over the entire surface including the surface having the step. Eight features.

  Moreover, in addition to any one of the first to eighth features, the variable resistance element manufacturing method according to the present invention includes Cu, Ni, V, Zn, Nb, Ti, W, A ninth feature is that it is made of a transition metal containing at least one of Co and Ta, or a transition metal nitride.

  According to the configuration of the present invention, a current can flow through the variable resistor body without performing a forming process in advance, so that the influence of the forming process on the electrical characteristics of the variable resistance element can be eliminated and stable switching can be performed. Operation can be enabled.

  Hereinafter, each embodiment of a variable resistance element according to the present invention (hereinafter referred to as “the present invention element” as appropriate) and a manufacturing method thereof (hereinafter referred to as “the present invention method” as appropriate) will be described with reference to the drawings. To do.

[First Embodiment]
A first embodiment of the element of the present invention and the method of the present invention (hereinafter referred to as “this embodiment” as appropriate) will be described with reference to FIGS. FIG. 1 schematically shows a schematic cross-sectional view in each process when manufacturing a semiconductor device in this embodiment, and is divided into FIGS. 1A to 1K for each process. Show. FIG. 2 is a flowchart of the manufacturing process of the present embodiment, and each step # 11 to # 21 in the following sentence represents each step of the flowchart shown in FIG.

  Note that the schematic cross-sectional structure diagram shown in FIG. 1 is schematically illustrated, and the dimensional ratio on the drawing does not necessarily match the actual dimensional ratio. Moreover, the numerical value of the film thickness of each film | membrane deposited at each process is an example to the last, Comprising: It is not limited to this value. The same applies to the following embodiments.

First, as shown in FIG. 1A, an insulating film 13 such as a SiO ₂ film (hereinafter referred to as “first interlayer insulation”) is formed on a semiconductor substrate 11 on which a transistor circuit or the like (not shown) and a metal wiring 12 are appropriately formed. A film 13 ") is deposited on the entire surface with a thickness of about 400 nm by a CVD (Chemical Vapor Deposition) method (step # 11).

  Next, as shown in FIG. 1B, the first interlayer insulating film 13 is opened by using a resist formed by a known photolithography technique as a mask so as to expose the upper surface of the metal wiring 12 by a known etching technique. Then, the contact hole 20 is formed (step # 12).

  Next, as shown in FIG. 1C, a first electrode material film 14 of tungsten (W) or the like is deposited on the entire surface with a thickness of about 500 nm by a CVD method, and all the contact holes 20 are deposited on the first electrode material. The film 14 is filled (step # 13).

  Next, as shown in FIG. 1D, the first interlayer insulating film 13 is first exposed until at least the upper surface of the first interlayer insulating film 13 is exposed by a flattening technique using a known CMP (Chemical Mechanical Polishing) method or the like. The electrode material film 14 is planarized (step # 14). Thereby, an electrode having a contact structure (hereinafter referred to as “first electrode 14” as appropriate) is formed by the first electrode material film 14 filled in the contact hole 20.

  Next, as shown in FIG. 1E, a resistive material film 15 such as TiN is deposited on the entire surface with a predetermined thickness (for example, 30 nm) by sputtering (step # 15).

  Next, as shown in FIG. 1F, the resistive material film 15 is patterned by a known etching technique using a resist formed by a known photolithography technique as a mask (step # 16). At this time, the resistive material film 15 is patterned so as to completely cover at least the upper surface of the first electrode 14.

  Next, as shown in FIG. 1G, for example, the resistance material film 15 is oxidized by thermal oxidation in an atmosphere containing oxygen at 250 to 450 ° C. to form the variable resistor 51 (step) # 17). At this time, for example, when a TiN film is employed as the resistance material film 15, thermal oxidation proceeds inward from the exposed surface of the TiN film 15, particularly from the upper surface side downward on the paper surface. As a result, a titanium oxide film is formed.

Next, as shown in FIG. 1H, an insulating film 16 such as a SiO ₂ film (hereinafter referred to as “second interlayer insulating film 16”) is deposited on the entire surface by a CVD method to a thickness of about 400 nm. (Step # 18).

  Next, as shown in FIG. 1 (i), the second interlayer insulation is used so that at least a part of the upper surface of the variable resistor 51 is exposed by a known etching technique using a resist formed by a known photolithography technique as a mask. The film 16 is opened and a contact hole 30 is formed (step # 19). At this time, as shown in FIG. 1 (i), the contact hole 30 is opened apart from the first electrode 14 in the horizontal direction so as not to overlap at least the region above the first electrode 14. In other words, the contact hole 30 is formed in a region where the first electrode 14 does not exist immediately below the exposed portion of the variable resistor 51 exposed by the formation of the contact hole 30.

  Next, as shown in FIG. 1 (j), a second electrode material film 17 such as W is deposited on the entire surface with a thickness of about 500 nm by the CVD method, and all the contact holes 30 are made of the second electrode material film 17. Fill (step # 20).

  Next, as shown in FIG. 1 (k), the second electrode material film 17 is flattened by using a known flattening technique by CMP or the like until at least the upper surface of the second interlayer insulating film 16 is exposed (step #). 21). Thereby, an electrode having a contact structure (hereinafter referred to as “second electrode 17” as appropriate) is formed by the second electrode material film 17 filled in the contact hole 30. Thereby, the element 1 of the present invention is manufactured. In addition, this invention element 1 manufactured in this way will be formed in the state in which the 1st electrode 14 and the 2nd electrode 17 were spaced apart in the horizontal direction.

  Next, the characteristics of the element 1 of the present invention manufactured through the above steps # 11 to # 21 will be described.

  FIG. 3 is a graph showing the switching characteristics of the element 1 of the present invention manufactured through steps # 11 to # 21, and shows the characteristics of the element 1 of the present invention manufactured with the variable resistor 15 having a thickness of 30 nm. ing. 3A is a photograph of the cross-sectional structure of the variable resistor 15 taken using a TEM (Transmission Electron Microscope), and FIG. 3B is a graph showing the characteristics. is there. In the photograph, the first electrode 14 is not formed in the lower layer of the variable resistor 51, and the second electrode 17 is not formed in the upper layer (that is, the first interlayer insulating film 13 is in the lower layer and the second interlayer is in the upper layer). This is a photograph of a cross-sectional structure taken at a location where the insulating film 16 is formed (corresponding to the region C in FIG. 1 (k)).

  Further, the graph shown in FIG. 3 shows that the first pulse voltage (voltage −2.6 [V], pulse width 35 [nsec]) between the first electrode 14 and the second electrode 17. .6V ") and the second pulse voltage (voltage +2.0 [V], pulse width 35 [nsec]. Indicated on the drawing as" + 2.0V ") are alternately applied and measured after each voltage application. The range of the measurement result of the resistance value (readout resistance value) is displayed on the graph. In the reading process, a resistance value measured by applying a voltage of 0.5 [V] is shown.

  According to FIG. 3, a phenomenon in which the resistance value transitions between a high resistance and a low resistance under the above voltage condition, that is, a switching phenomenon is observed. Moreover, the switching phenomenon can be caused without going through a forming process in which a high voltage is applied in advance to the initial state to form a current path in the insulator. The reason for this will be discussed below.

  FIG. 4 shows the atomic% of the variable resistor film 51 manufactured based on the method of the present invention according to this embodiment by energy dispersive X-ray analysis (EDX: Energy Dispersive X-ray Spectroscopy: hereinafter referred to as “EDX”). The result of profile analysis is shown. As a measurement object, titanium oxide having a variable resistor 51 with a thickness of 10 nm was used.

As shown in FIG. 1 (k), the variable resistor 51 includes a first interlayer insulating film in a portion (region C) where the first electrode 14 is not formed in the lower layer and the second electrode 17 is not formed in the upper layer. Since it is sandwiched between the (SiO ₂ film) 13 and the second interlayer insulating film (SiO ₂ film) 16, measurement was performed with O, Si, and Ti as atoms to be analyzed by EDX. In FIG. 4, the direction from the second interlayer insulating film 16 toward the variable resistor 51 and the first interlayer insulating film 13 is defined as a scanning direction d1, and the variation in the scanning direction d1 is laterally measured from the second interlayer insulating film 16 side. The graph is graphed with the axis and the content% of each atom as the vertical axis, wherein (1) indicates O, (2) indicates Si, and (3) indicates each content% of Ti.

  According to FIG. 4, in the variable resistor film 51, the content percentage of O in (1) decreases as it advances in the scanning direction d1, while the content percentage of Ti in (3) increases. . From this, it can be seen that in the variable resistor film (titanium oxide film) 51, oxygen has a concentration gradient in the same direction as the scanning direction d1, while Ti has a concentration gradient in the direction opposite to d1. . That is, in the variable resistor film 51, oxygen is most present in the second interlayer insulating film 16 side, that is, the upper region of the variable resistor film 51, and the first interlayer insulating film 13 side, that is, the lower portion of the variable resistor film 51. In the region, oxygen is relatively low, while a large amount of Ti, which is a metal, is present. In other words, the upper region with a high oxygen concentration is in a high resistance state because the Ti concentration is low, while the lower region with a low oxygen concentration has a high resistance so that the Ti concentration becomes relatively high even if it is partially oxidized. It is thought that it has not become.

  FIG. 5 is a schematic diagram in which the cross-sectional structure diagram shown in FIG. As shown in FIG. 5, the first electrode 14 is formed in the lower layer of the variable resistor 51, and the second electrode 17 is formed in the upper layer.

  As described above, the variable resistor 51 has a relatively high resistance value in the upper region (region 51a in FIG. 5) and a relatively low resistance value in the lower region (region 51b in FIG. 5). Here, for example, when a voltage pulse is applied between both electrodes so that the second electrode 17 is positive with respect to the first electrode 14, the current flows in the order of the second electrode 17, the variable resistor 51, and the first electrode 14. I flows. At this time, as described above, since the second electrode 17 and the first electrode 14 are formed apart from each other in the horizontal direction, the current I flows in the variable resistor 51 in the horizontal direction. Since the variable resistor 51 has a region 51b having a relatively low resistance value in the horizontal direction in the lower region, the region 51b can be used as a path from the second electrode 17 to the first electrode 14. it can.

  That is, when a voltage is applied to the variable resistor 51, a direction (hereinafter referred to as “first direction” as appropriate) perpendicular to the direction (direction d1) of the oxygen concentration gradient, that is, the first in FIG. When a voltage is applied between two points (two regions) separated in the direction d2, the current I can flow in the vicinity of the relatively low resistance lower region 51b in the variable resistor 51. In this current path, there is no region having a high resistance value, that is, an insulator region. Therefore, it is not necessary to perform a forming process for forming a current path in the insulator in advance. On the other hand, since the variable resistor 51 shows a constant oxygen concentration distribution as shown in FIG. 4, it does not easily function as a perfect conductor because of its switching characteristics as shown in FIG. It functions as a variable resistance element that changes the value.

  That is, the variable resistor 51 has a conductive distribution in the film thickness direction d1, and a voltage pulse is applied between two different regions in the variable resistor 51 spaced apart in the first direction d2 perpendicular to d1. Then, it is suggested that a current flows through the region 51b having a relatively high conductivity in the variable resistor 51. That is, in the variable resistor 51, the region 51b having a relatively high conductivity already exists as a current path from the second electrode 17 to the first electrode 14, so that it is not necessary to perform a forming process in advance.

  The element 1 of the present invention has two electrodes (first electrode 14 and second electrode 17) for applying a voltage to the variable resistor 51. The first electrode 14, the variable resistor 51, The first connection region 14x that is electrically connected to the second connection region 17x that is electrically connected to the second electrode 17 and the variable resistor 51 has a direction d1 that the oxygen concentration gradient in the variable resistor 51 has. And spaced apart in a first direction d2 perpendicular to (see FIG. 1 (k), FIG. 5). As a result, by applying a voltage between the two electrodes, a path of a current I flowing from one electrode through the variable resistor 51 toward the other electrode serves as a relatively conductive material in the variable resistor 51. The high area 51b can be used.

  FIG. 6 shows another configuration example of the element of the present invention in this embodiment. 6A shows the case where both the first electrode 14 and the second electrode 17 are formed in the upper layer of the variable resistor 51. FIG. 6B shows the case where both electrodes are formed in the lower layer of the variable resistor 51. This is the case. Further, FIG. 6B shows a configuration further including a metal wiring 12a for forming electrical connection with the second electrode 17 and a contact connection electrode 17a.

  6 (a) and 6 (b), this is realized only by partially changing the order of the steps # 11 to 21 described above or by additionally forming a metal wiring layer or a contact hole. Therefore, detailed description of the process is omitted.

  6A and 6B, the variable resistor 51 has a gradient in oxygen concentration in the film thickness direction d1. The first connection region 14x in which the first electrode 14 and the variable resistor 51 are electrically connected, and the second electrode 17 and the variable resistor 51 are electrically connected in the first direction d2 orthogonal to the d1 direction. The second connection region 17x to be connected is separated. Therefore, similarly to the configuration of FIG. 1 (k), when a voltage is applied between the first electrode 14 and the second electrode 17, the relatively high conductivity formed in the lower region in the variable resistor 51 is high. Since a current path can be formed through the region, a variable resistance element having switching characteristics can be realized without performing a forming process.

  FIG. 7 shows still another configuration example of the element of the present invention in the present embodiment. 7A, the second electrode 17 penetrates the variable resistor 51 and is formed in the upper layer and the lower layer of the variable resistor as compared with the configuration of FIG. Further, in FIG. 7B, as compared with the configuration of FIG. 1K, the first electrode 14 and the second electrode 17 both penetrate the variable resistor 51 and are formed in the upper and lower layers of the variable resistor. Is formed.

  7A and 7B can be realized only by changing the formation shape of the contact hole or omitting some of the steps in the steps # 11 to 21 described above. Detailed description of the process will be omitted.

  7A and 7B, the variable resistor 51 has a gradient in oxygen concentration in the film thickness direction d1. The first connection region 14x in which the first electrode 14 and the variable resistor 51 are electrically connected, and the second electrode 17 and the variable resistor 51 are electrically connected in the first direction d2 orthogonal to the d1 direction. The second connection region 17x to be connected is separated. Therefore, similarly to the configuration of FIG. 1 (k), when a voltage is applied between the first electrode 14 and the second electrode 17, the relatively high conductivity formed in the lower region in the variable resistor 51 is high. Since a current path can be formed through the region, a variable resistance element having switching characteristics can be realized without performing a forming process. Note that the first connection region 14x in FIG. 7A and the first connection region 14x and the second connection region 17x in the seventh (b) are regions where the outer surface of each electrode and the variable resistor 51 are in contact with each other. Equivalent to.

  Further, in the present embodiment described above, as shown in the graph of FIG. 4, the higher the oxygen concentration in the variable resistor 51, the lower the Ti concentration, thereby indicating that the conductivity is low. The variable resistor 51 is formed by oxidizing the TiN film 15 in step # 17, and the oxygen concentration in the variable resistor 51 is adjusted by controlling the processing time related to step # 17. Can do. In other words, since the resistance value of the variable resistor 51 can be controlled by the processing time related to step # 17, the current consumption during writing and erasing can be reduced, and the writing resistance cannot be prevented by low resistance. Thus, it is possible to realize the variable resistance element having the switching operation with good reproducibility.

  In the present embodiment, TiN is used as the resistance material film 15 and the variable resistor 51 is formed by the titanium oxide film generated by oxidizing the film. However, oxidation such as oxidation temperature and oxygen concentration is performed. By appropriately adjusting the conditions, the variable resistor 51 can be a titanium oxynitride film having variable resistance characteristics. The same applies to the following second to fifth embodiments.

[Second Embodiment]
A second embodiment (hereinafter referred to as “this embodiment” as appropriate) of the element of the present invention and the method of the present invention will be described with reference to FIGS. 8 to 9. FIG. 8 schematically shows a schematic cross-sectional view in each process when manufacturing a semiconductor device in the present embodiment, and is divided into FIG. 8A to FIG. 8L for each process. Show. FIG. 9 is a flowchart of the manufacturing process of the present embodiment, and each step # 25 to # 36 in the following sentence represents each step of the flowchart shown in FIG. Moreover, about the step by the process similar to each step of 1st Embodiment, that effect is described and detailed description is omitted.

  First, the metal wiring 12, the first interlayer insulating film 13, and the first electrode 14 are formed on the semiconductor substrate 11 by the same processing as steps # 11 to # 14 (FIGS. 8A to 8D, step #). 25- # 28).

  Next, as shown in FIG. 8E, a resistive material film 15 such as TiN is deposited on the entire surface to a thickness of 60 nm, for example, by sputtering (step # 29). The film thickness of the resistive material film 15 deposited here is larger than the deposited film thickness of Step # 15 in the first embodiment.

  Next, as in step # 16, as shown in FIG. 8F, the resistive material film 15 is patterned by a known etching technique using a resist formed by a known photolithography technique as a mask (step # 30).

  Next, as shown in FIG. 8G, a part of the resistive material film 15 is thinned to a predetermined thickness (for example, 30 nm) by a known etching technique using a resist formed by a known photolithography technique as a mask. (Step # 31). As a result, the resistance material film 15 is composed of a thick portion 15a and a thin portion 15b. In step # 31, an etching process is performed so that the thin portion 15b completely covers at least the upper surface of the first electrode 14, and the thick portion 15a does not cover the upper surface of the first electrode 14. Hereinafter, the thick portion 15a and the thin portion 15b are simply referred to as “resistive material film 15a” and “resistive material film 15b”, respectively.

  Next, as shown in FIG. 8H, the variable resistance body 51 is formed by oxidizing the resistance material film 15 in the same manner as in Step # 17 (Step # 32). At this time, the oxidation condition is set so that the resistance material film 15b is completely oxidized for the film thickness and the variable resistor 51 is formed in the formation region. As a result, the resistance material film 15a is oxidized from the surface by a predetermined film thickness (almost equivalent to the film thickness of the resistance material film 15b), and the remaining film thickness remains without being oxidized.

  At this time, the variable resistor 51 in the region J is formed in a state having an oxygen concentration gradient in the direction d1 as in the first embodiment.

  Next, as shown in FIG. 8I, the second interlayer insulating film 16 is formed (step # 33) as in step # 18.

  Next, as shown in FIG. 8J, as in step # 19, a part of the second interlayer insulating film 16 is opened to form a contact hole 30 (step # 34). At this time, unlike the first embodiment, the variable resistor 51 is also etched, and the contact hole 30 is formed by etching until the upper surface of the electrode film 15a is exposed. As in the first embodiment, the contact hole 30 is formed in a region where the first electrode 14 does not exist immediately below the exposed portion of the variable resistor 51 exposed by the formation of the contact hole 30.

  Next, as shown in FIG. 8 (k), as in step # 20, the second electrode material film 17 is deposited on the entire surface, and all the contact holes 30 are filled with the second electrode material film 17 (step # 35). ).

  Next, as shown in FIG. 8L, like the step # 21, the second electrode material film 17 is flattened until at least the upper surface of the second interlayer insulating film 16 is exposed (step # 36). Thereby, an electrode having a contact structure (hereinafter referred to as “second electrode 17” as appropriate) is formed by the second electrode material film 17 filled in the contact hole 30.

  In the element of the present invention formed through the steps # 25 to # 36, the first electrode 14 and the variable resistor 51 are electrically connected in the first connection region 14x. The second electrode 17 and the variable resistor 51 are electrically connected in the second connection region 17x via the resistance material film 15a.

  That is, as shown in FIG. 8L, the first connection region 14x in which one electrode (first electrode 14) and the variable resistor 51 are electrically connected, and the other electrode (second electrode 17 and The resistance material film 15a) and the second connection region 17x in which the variable resistor 51 is electrically connected are formed apart from each other in a first direction d2 orthogonal to the gradient direction d1 of the oxygen concentration in the variable resistor 51. The Therefore, similarly to the first embodiment, also in the variable resistance element in the present embodiment, a voltage is applied between the first electrode 14 and the second electrode 17 so that one electrode can pass through the variable resistor 51. As a path of the current I flowing toward the other electrode, a relatively highly conductive region in the variable resistor 51 can be used, so that it is not necessary to perform a forming process. Since the variable resistor 51 exhibits a constant oxygen concentration distribution, it exhibits the same switching characteristics as in FIG. 3 and functions as a variable resistance element.

[Third Embodiment]
A third embodiment (hereinafter referred to as “this embodiment” as appropriate) of the element of the present invention and the method of the present invention will be described with reference to FIGS. FIG. 10 schematically shows a schematic cross-sectional view in each process when manufacturing a semiconductor device in the present embodiment, and is divided into FIGS. 10A to 10I for each process. Show. FIG. 11 is a flowchart of the manufacturing process of this embodiment, and each step # 40 to # 48 in the following sentence represents each step of the flowchart shown in FIG. Moreover, about the step by the process similar to each step of the said 1st Embodiment, that effect is described and detailed description is omitted.

First, as shown in FIG. 10A, an insulating film 13 such as a SiO ₂ film (hereinafter referred to as “first”) is formed on a semiconductor substrate 11 on which a transistor circuit (not shown) and metal wirings 12c and 12d are appropriately formed. (Referred to as “interlayer insulating film 13”) is deposited on the entire surface to a thickness of about 400 nm by the CVD method (step # 40).

  Next, as shown in FIG. 10B, as in step # 12, the first interlayer insulating film 13 is opened to expose the upper surfaces of the metal wirings (12c, 12d), and contact holes 20c, 20d are formed. (Step # 41).

  Next, as shown in FIG. 10C, as in step # 13, a first electrode material film 14 such as W is deposited on the entire surface with a thickness of about 500 nm by the CVD method to form all the contact holes 20c and 20d. The first electrode material film 14 is filled (step # 42).

  Next, as shown in FIG. 10D, as in step # 14, the first electrode material film 14 is flattened until at least the upper surface of the first interlayer insulating film 13 is exposed (step # 43). Thus, the first electrode material film 14 filled in the contact hole 20 is connected to each of the metal wirings 12c and 12d to form an electrode having a contact structure (hereinafter referred to as “first electrode 14c” and “second electrode 14d” as appropriate). Is formed).

  Next, as shown in FIG. 10E, a resistive material film 15 such as TiN is deposited on the entire surface to a thickness of 60 nm, for example, by sputtering (step # 44). The film thickness of the resistive material film 15 deposited here is larger than the deposited film thickness of Step # 15 in the first embodiment.

  Next, as in step # 16, as shown in FIG. 10F, the resistance material film 15 is patterned by a known etching technique using a resist formed by a known photolithography technique as a mask (step # 45).

  Next, as shown in FIG. 10G, a part of the resistive material film 15 is thinned to a predetermined thickness (for example, 30 nm) by a known etching technique using a resist formed by a known photolithography technique as a mask. (Step # 46). As a result, the resistance material film 15 is composed of a thick portion 15a and a thin portion 15b. In step # 46, the thick portion 15a covers the upper surfaces of the first electrode 14c and the second electrode 14d, and the thin portion 15b does not cover the upper surfaces of both electrodes, and is sandwiched between the two electrodes. Etching is performed so as to be formed on the upper surface of the region. Hereinafter, the thick portion 15a and the thin portion 15b are simply referred to as “resistive material film 15a” and “resistive material film 15b”, respectively.

  Next, as shown in FIG. 10H, the variable resistance body 51 is formed by oxidizing the resistance material film 15 in the same manner as in Step # 17 (Step # 47). At this time, the oxidation condition is set so that the resistance material film 15b is completely oxidized for the film thickness and the variable resistor 51 is formed in the formation region. As a result, the resistance material film 15a is oxidized from the surface by a predetermined film thickness (almost equivalent to the film thickness of the resistance material film 15b), and the remaining film thickness remains without being oxidized. That is, as shown in FIG. 10H, when the resistance material film 15b is changed to the variable resistor 51, the resistance material film 15a is divided into two resistance material films 15c and 15d. The variable resistor 51 is electrically connected to the resistance material film 15c and the resistance material film 15d.

  At this time, the variable resistor 51 in the region J is formed in a state having an oxygen concentration gradient in the direction d1 as in the first embodiment.

  Next, as shown in FIG. 10I, the second interlayer insulating film 16 is formed in the same manner as in Step # 18 (Step # 48).

  In the element of the present invention formed through the above steps # 40 to # 48, the first electrode 14c and the variable resistor 51 are electrically connected to each other in the first connection region 14x through the resistive material film 15c. Further, the second electrode 17 and the variable resistor 51 are electrically connected in the second connection region 17x via the resistive material film 15d. In other words, if the first electrode 14c and the resistive material film 15c are regarded as one electrode, this electrode is electrically connected to the variable resistor 51 in the second connection region 17x, and similarly, If the electrode 14d and the resistive material film 15d are regarded as one electrode, the electrode is electrically connected to the variable resistor 51 in the second connection region 17x.

  That is, as shown in FIG. 10 (i), the first connection region 14 x in which one electrode (the first electrode 14 c and the resistance material film 15 c) and the variable resistor 51 are electrically connected, and the other electrode ( The second connection region 17x in which the second electrode 14d and the resistive material film 15d) and the variable resistor 51 are electrically connected is in a first direction d2 perpendicular to the gradient direction d1 of the oxygen concentration in the variable resistor 51. They are formed apart. Therefore, similarly to the first embodiment, also in the variable resistance element in the present embodiment, a voltage is applied between the first electrode 14 and the second electrode 17 so that one electrode can pass through the variable resistor 51. As a path of the current I flowing toward the other electrode, a relatively highly conductive region in the variable resistor 51 can be used, so that it is not necessary to perform a forming process. Since the variable resistor 51 exhibits a constant oxygen concentration distribution, it exhibits the same switching characteristics as in FIG. 3 and functions as a variable resistance element.

  FIG. 12 shows another configuration example of the element of the present invention in this embodiment. The configuration shown in FIG. 12 is different from the case of FIG. 10 in that two electrodes electrically connected to the variable resistor are formed in different layers. The manufacturing process will be briefly described below.

  First, as shown in FIG. 12A, a first interlayer insulating film 13 having a thickness of about 400 nm is deposited on the entire surface of a semiconductor substrate 11 on which a transistor circuit and the like (not shown) and a metal wiring 12 are appropriately formed. Thereafter, the first interlayer insulating film 13 is opened so that the upper surface of the metal wiring 12 is exposed, and a contact hole 20 is formed.

  Next, as shown in FIG. 12B, a resistive material film 15 such as TiN is deposited on the entire surface by sputtering so as not to completely fill the contact hole 20, and then patterned. At this time, the film thickness deposited on the inner side wall in the contact hole 20 is sufficiently thinner than the film thickness deposited on the bottom of the contact hole 20 and the upper layer of the first interlayer insulating film 13.

  Next, as illustrated in FIG. 12C, the variable resistance body 51 is formed by oxidizing the resistance material film 15 by, for example, thermal oxidation in an atmosphere containing oxygen at 250 to 450 ° C. At this time, the resistance material film 15 deposited on the inner wall of the contact hole 20 having a small film thickness is subjected to oxidation corresponding to the film thickness and deposited on the upper layer of the metal wiring 12 and the upper layer of the first interlayer insulating film 13. As for the resistance material film 15, a part of the film thickness is oxidized, and a part of the unoxidized resistance material film 15 is left. That is, as shown in FIG. 12C, the resistance material film 15 is deposited on the metal wiring upper layer by changing the metal film deposited on the inner wall of the contact hole 20 to the variable resistor 51. The resistive material film 15 d is divided into a resistive material film 15 c deposited on the first interlayer insulating film 13. The variable resistor 51 is electrically connected to the resistance material film 15c and the resistance material film 15d.

  In the inner wall portion (region J) of the contact hole 20, oxidation proceeds from the central axis of the contact hole 20 toward the outside. For this reason, the variable resistor 51 formed in such a region has an oxygen concentration gradient in the same direction (direction d1) as the oxidation direction.

  Next, as shown in FIG. 12D, a second interlayer insulating film 16 is formed. Then, as shown in FIG. 12E, a contact hole 30 is formed by opening a part of the upper region of the resistive material film 15c. At this time, similarly to step # 34 of the second embodiment, the variable resistor 51 is also etched, and etching is performed until the upper surface of the electrode film 15c is exposed, thereby forming the contact hole 30.

  Next, as shown in FIG. 12 (f), the first electrode material film 14 is deposited on the entire surface, and the contact holes 30 are all filled with the first electrode material film 14.

  Next, as shown in FIG. 12G, the first electrode material film 14 is planarized until at least the upper surface of the second interlayer insulating film 16 is exposed. Thereby, the first electrode 14 having a contact structure is formed by the first electrode material film 14 filled in the contact hole 30.

  That is, in the element of the present invention formed based on the above method, one electrode (the first electrode 14 and the resistive material film 15c) and the variable resistor 51 are electrically connected in the first connection region 14x. On the other hand, the other electrode (resistance material film 15d) and the variable resistor 51 are electrically connected in the second connection region 17x. The first connection region 14x and the second connection region 17x are formed apart from each other in a first direction d2 orthogonal to the oxygen concentration gradient direction d1 in the variable resistor 51. Accordingly, also in the configuration example shown in FIG. 12, by applying a voltage between the first electrode 14 and the second electrode 17, it flows from one electrode toward the other electrode through the variable resistor 51. As a path of the current I, a region having a relatively high conductivity in the variable resistor 51 can be used, so that it is not necessary to perform a forming process. Since the variable resistor 51 exhibits a constant oxygen concentration distribution, it exhibits the same switching characteristics as in FIG. 3 and functions as a variable resistance element.

  In the case of the configuration example of FIG. 12, the resistive material film 15 c that is electrically connected via the variable resistor 51 is formed at two locations with respect to the resistive material film 15 d at one location. For this reason, as shown in FIG. 13, by forming the first electrode 14 so as to be electrically connected to each resistive material film 15c, the variable resistor is sandwiched between two different electrodes. Can be formed (variable resistors 51a and 51b). Accordingly, 2 bits can be stored in one structural unit, and the storage capacity can be increased while suppressing an increase in element size.

[Fourth Embodiment]
A fourth embodiment of the method of the present invention (hereinafter referred to as “this embodiment” as appropriate) will be described with reference to FIGS. FIG. 14 schematically shows a schematic cross-sectional view in each step when manufacturing a semiconductor device in the present embodiment, and is divided into FIG. 14A to FIG. 14M for each step. Show. FIG. 15 is a flowchart of the manufacturing process of the present embodiment, and each step # 50 to # 62 in the following sentence represents each step of the flowchart shown in FIG. Moreover, about the step by the process similar to each step of 1st Embodiment, that effect is described and detailed description is omitted.

  First, the metal wiring 12, the first interlayer insulating film 13, and the first electrode 14 are formed on the semiconductor substrate 11 by the same processing as steps # 11 to # 14 (FIGS. 14A to 14D, step #). 50- # 53).

  Next, as shown in FIG. 14E, a conductive film 18 such as Pt is deposited on the entire surface with a thickness of 60 nm, for example, by sputtering (step # 54).

  Next, as shown in FIG. 14F, the conductive film 18 is patterned by a known etching technique using a resist formed by a known photolithography technique as a mask (step # 55). By this step, the formation region of the conductive film 18 has a top surface higher than the other regions, and a step is formed.

  Next, as shown in FIG. 14G, a resistive material film 15 such as TiN is deposited on the entire surface by sputtering, for example, to a thickness of 30 nm (step # 56). By this step, the resistive material film 15 is also deposited on the outer surface of the conductive film 18.

  Next, as in step # 16, as shown in FIG. 14H, the resistance material film 15 is patterned by a known etching technique using a resist formed by a known photolithography technique as a mask (step # 57). .

  Next, as in step # 17, as shown in FIG. 14I, the resistance material film 15 is oxidized to form the variable resistor 51 (step # 58). At this time, the resistance material film 15 is oxidized by the deposited film thickness, and the entire resistance material film 15 is changed to the variable resistor 51. Note that oxidation proceeds in the downward direction d1 for the resistive material film 15 (region J) deposited on the upper layer of the first interlayer insulating film 13 by this step. For this reason, the variable resistor 51 formed in such a region also has an oxygen concentration gradient in the same direction as the oxidation direction (direction d1).

  Next, as in step # 18, as shown in FIG. 14J, the second interlayer insulating film 16 is formed (step # 59).

  Next, as in step # 19, as shown in FIG. 14K, the second interlayer insulating film 16 is opened and a contact hole 30 is formed using a resist formed by a known photolithography technique as a mask (see FIG. 14K). Step # 60). At this time, similarly to Step # 34 of the second embodiment, the variable resistor 51 is also etched and etched until the upper surface of the conductive film 18 is exposed to form the contact hole 30.

  Next, as in step # 20, as shown in FIG. 14L, the second electrode material film 17 is deposited on the entire surface, and the contact holes 30 are all filled with the second electrode material film 17 (step #). 61).

  Next, as in step # 21, as shown in FIG. 14M, the second electrode material film 17 is flattened until at least the upper surface of the second interlayer insulating film 16 is exposed (step # 62). Thereby, the second electrode 17 having a contact structure is formed by the second electrode material film 17 filled in the contact hole 30.

  In the element of the present invention formed through the above steps # 50 to # 62, the first electrode 14 and the variable resistor 51 are electrically connected in the first connection region 14x. The second electrode 17 and the variable resistor 51 are electrically connected to each other in the second connection region 17x through the conductive film 18.

  That is, as shown in FIG. 14 (m), the first connection region 14x in which one electrode (first electrode 14) and the variable resistor 51 are electrically connected, and the other electrode (second electrode 17 and The second connection region 17x in which the conductive film 18) and the variable resistor 51 are electrically connected to each other is in a first direction d2 (paper surface) perpendicular to the oxygen concentration gradient direction d1 (up and down on the paper surface) in the variable resistor 51. It is formed apart in the horizontal direction. Therefore, similarly to the first embodiment, also in the variable resistance element in the present embodiment, a voltage is applied between the first electrode 14 and the second electrode 17 so that one electrode can pass through the variable resistor 51. As a path of the current I flowing toward the other electrode, a relatively highly conductive region in the variable resistor 51 can be used, so that it is not necessary to perform a forming process. Since the variable resistor 51 exhibits a constant oxygen concentration distribution, it exhibits the same switching characteristics as in FIG. 3 and functions as a variable resistance element.

  FIG. 16 shows another configuration example of the element of the present invention in this embodiment. 16, compared with FIG. 14 (m), the third interlayer insulating film 61 is formed in a partial region of the upper layer of the first interlayer insulating film 13, and the conductive film 18 and the second electrode 17 are formed thereon. This is the configuration. Compared to the configuration of FIG. 14, the third interlayer insulating film 61 deposition process and the etching process can be realized only by adding a new process, and the description of the process is omitted.

  Also in the case of the configuration example shown in FIG. 16, as in the case of FIG. 14 (m), the first connection region 14 x in which one electrode (first electrode 14) and the variable resistor 51 are electrically connected, The other electrode (the second electrode 17 and the conductive film 18) and the second connection region 17x in which the variable resistor 51 is electrically connected are in the gradient direction d1 of oxygen concentration in the variable resistor 51 (upward and downward in the drawing). Since the first electrode 14 and the second electrode 17 are applied with a voltage between the first electrode 14 and the second electrode 17, they are separated from each other in the variable resistor 51. As a path of the current I flowing toward the other electrode via the, a region having a relatively high conductivity in the variable resistor 51 can be used, and there is no need to perform a forming process. Since the variable resistor 51 exhibits a constant oxygen concentration distribution, it exhibits the same switching characteristics as in FIG. 3 and functions as a variable resistance element.

[Fifth Embodiment]
A fifth embodiment of the method of the present invention (hereinafter referred to as “this embodiment” as appropriate) will be described with reference to FIGS. FIG. 17 schematically shows a schematic cross-sectional view in each process when manufacturing a semiconductor device in the present embodiment, and is divided into FIGS. 17A to 17J for each process. Show. FIG. 18 is a flowchart of the manufacturing process of the present embodiment, and each step # 65 to # 74 in the following sentence represents each step of the flowchart shown in FIG. Moreover, about the step by the process similar to each step of said each embodiment, that is described and detailed description is omitted.

  First, as shown in FIGS. 17A to 17D, similarly to steps # 40 to # 43 of the third embodiment, a semiconductor in which transistor circuits and the like (not shown) and metal wirings 12c and 12d are appropriately formed. A first interlayer insulating film 13, a first electrode 14c, and a second electrode 14d are formed on the substrate 11 (steps # 65 to # 68).

  Next, as shown in FIG. 17E, a conductive film 18 such as Pt is deposited on the entire surface as in Step # 54 of the fourth embodiment (Step # 69).

  Next, as shown in FIG. 17F, the conductive film 18 is patterned by a known etching technique using a resist formed by a known photolithography technique as a mask to form conductive films 18c and 18d (step # 70). ).

  Next, as shown in FIG. 17G, as in step # 56 of the fourth embodiment, a resistive material film 15 such as TiN is deposited on the entire surface by sputtering, for example, to a thickness of 30 nm (step # 71). . By this step, the resistive material film 15 is also deposited on the outer surfaces of the conductive films 18c and 18d.

  Next, as shown in FIG. 17H, the resistive material film 15 is patterned similarly to Step # 57 of the fourth embodiment (Step # 72).

  Next, as shown in FIG. 17I, the variable material 51 is formed by oxidizing the resistive material film 15 in the same manner as in Step # 58 of the fourth embodiment (Step # 73). Also in this step, as in the fourth embodiment, the resistance material film 15 is oxidized by the deposited film thickness, and the entire resistance material film 15 is changed to the variable resistor 51. Note that oxidation proceeds in the downward direction d1 for the resistive material film 15 (region J) deposited on the upper layer of the first interlayer insulating film 13 by this step. For this reason, the variable resistor 51 formed in such a region also has an oxygen concentration gradient in the same direction as the oxidation direction (direction d1).

  Next, as shown in FIG. 17J, the second interlayer insulating film 16 is formed (step # 74) as in step # 59 of the fourth embodiment.

  As shown in FIG. 17J, the element of the present invention formed through the above steps # 65 to # 74 has the first electrode 14 and the variable resistor 51 connected to the first connection region 14x via the conductive film 18c. Are electrically connected. The second electrode 17 and the variable resistor 51 are electrically connected in the second connection region 17x via the conductive film 18d.

  That is, as shown in FIG. 17J, the first connection region 14x in which one electrode (the first electrode 14 and the conductive film 18c) and the variable resistor 51 are electrically connected, and the other electrode (the first electrode) The second connection region 17x in which the two electrodes 17 and the conductive film 18d) and the variable resistor 51 are electrically connected to each other is perpendicular to the gradient direction d1 of oxygen concentration in the variable resistor 51 (upward and downward in the drawing). They are spaced apart in the direction d2 (the horizontal direction on the paper). Therefore, similarly to the first embodiment, also in the variable resistance element in the present embodiment, a voltage is applied between the first electrode 14 and the second electrode 17 so that one electrode can pass through the variable resistor 51. As a path of the current I flowing toward the other electrode, a relatively highly conductive region in the variable resistor 51 can be used, so that it is not necessary to perform a forming process. Since the variable resistor 51 exhibits a constant oxygen concentration distribution, it exhibits the same switching characteristics as in FIG. 3 and functions as a variable resistance element.

  FIG. 19 shows another configuration example of the element of the present invention in this embodiment. The configuration shown in FIG. 19 is different from the case of FIG. 17 in that two electrodes electrically connected to the variable resistor are formed in different layers. The manufacturing process will be briefly described below.

  First, as shown in FIG. 19A, after depositing a metal film such as Pt on the semiconductor substrate 11 on which a transistor circuit or the like (not shown) is appropriately formed, a conductive film 18a is formed by patterning.

  Next, as shown in FIG. 19B, after depositing a first interlayer insulating film 13 with a thickness of about 400 nm on the entire surface, a metal film such as Pt is deposited, and this metal film is patterned to form a conductive film. 18b and 18c are formed. At this time, the conductive films 18b and 18c are formed so as to be spaced apart in the horizontal direction and the conductive film 18a positioned below the region sandwiched between the two metal films.

  Next, as shown in FIG. 19C, the first interlayer insulating film 13 is opened until the upper surface of the conductive film 18a is exposed, and a contact hole 20 is formed.

  Next, as shown in FIG. 19D, a resistive material film 15 such as TiN is deposited on the entire surface by sputtering so as not to completely fill the contact hole 20.

  Next, as shown in FIG. 19E, after the resistance material film 15 is patterned, the resistance material film 15 is subjected to thermal oxidation in an atmosphere containing oxygen at 250 to 450 ° C. The variable resistor 51 is formed by partial oxidation.

  In the inner wall portion (region J) of the contact hole 20, oxidation proceeds from the central axis of the contact hole 20 toward the outside. For this reason, the variable resistor 51 formed in such a region has an oxygen concentration gradient in the same direction (direction d1) as the oxidation direction.

  Next, as shown in FIG. 19F, after the second interlayer insulating film 16 is deposited on the entire surface, the second interlayer insulating film 16 and the variable thickness are exposed until the conductive film 18b is exposed at a position above the conductive film 18b. The resistor 51 is etched to form the contact hole 30.

  Next, as shown in FIG. 19G, after an electrode material film such as W is formed on the entire surface, a planarization process is performed to form a second electrode 17 having a contact structure.

  That is, in the element of the present invention formed based on the above method, one electrode (conductive film 18a) and the variable resistor 51 are electrically connected in the first connection region 14x. On the other hand, the other electrode (the second electrode 17 and the conductive film 18b) and the variable resistor 51 are electrically connected in the second connection region 17x. The first connection region 14x and the second connection region 17x are formed apart from each other in a direction d2 perpendicular to the gradient direction d1 of the oxygen concentration in the variable resistor 51. Accordingly, also in the configuration example shown in FIG. 19, by applying a voltage between one electrode and the other electrode, the current I flowing from the one electrode toward the other electrode through the variable resistor 51. Since a region having a relatively high conductivity in the variable resistor 51 can be used as the path of the variable resistor 51, there is no need to perform a forming process. Since the variable resistor 51 exhibits a constant oxygen concentration distribution, it exhibits the same switching characteristics as in FIG. 3 and functions as a variable resistance element.

  In the case of the configuration example of FIG. 19, as in the case of the configuration example of FIG. 12, two metal films that are electrically connected via the variable resistor 51 are formed on one conductive film 18 a. (18b, 18c). For this reason, as shown in FIG. 20, by forming the second electrode 17 so as to be electrically connected to the respective metal films (18b, 18c), a variable resistor is formed between two different electrodes. Two variable resistance elements sandwiched between the two can be formed (variable resistors 51a and 51b). Accordingly, 2 bits can be stored in one structural unit, and the storage capacity can be increased while suppressing an increase in element size.

[Sixth Embodiment]
A sixth embodiment (hereinafter referred to as “this embodiment” where appropriate) of the element of the present invention and the method of the present invention will be described with reference to FIGS. In addition, this embodiment is a structure from which the material utilized as a resistance material film differs compared with said each embodiment. Below, description is simplified about the component and process which are the same as said each embodiment.

  Specifically, a difference is that a Co film is used instead of the TiN film used as the resistance material film in each of the above-described embodiments. For example, when manufacturing by the same process as in the first embodiment, first, the metal wiring 12 and the first interlayer insulating film 13 are formed on the semiconductor substrate 11 by the same process as steps # 11 to # 14 in the first embodiment. After the first electrode 14 is formed, a Co film is deposited as a resistive material film instead of Step # 15. Thereafter, in steps # 16 to # 17, the resistance material film 15 (Co film 15) made of Co is patterned, and then the resistance material film 15 is oxidized to form the variable resistor 51. At this time, thermal oxidation proceeds inward from the exposed surface of the Co film 15, particularly downward from the upper surface side on the paper surface, and as an example, a cobalt oxide film is formed. As in the case of the first embodiment, the variable resistor 51 in the region C is formed in a state having an oxygen concentration gradient in the direction d1 by the oxidation treatment in step # 17.

  Thereafter, the contact hole 30 is formed through the same processes as steps # 18 to # 21 of the first embodiment, and the contact hole 31 is filled with the second electrode material film 17. Thereby, the element 1 of the present invention is manufactured. The element 1 of the present invention thus manufactured is formed in a state where the first electrode 14 and the second electrode 17 are spaced apart from each other in the horizontal direction, as in the first embodiment. The variable resistor 51 is electrically connected in the first connection region 14x.

  FIG. 21 is a graph showing the switching characteristics of the element 1 of the present invention manufactured by using the Co film as the resistance material film by the above method, and the film thickness of the variable resistor 15 is the same as the graph of FIG. The characteristics of the element 1 of the present invention manufactured with a thickness of 30 nm are shown. The switching characteristic acquisition method and the graph display method are the same as those in FIG. That is, between the first electrode 14 and the second electrode 17, the first pulse voltage (voltage −2.0 [V], pulse width 35 [nsec]. Indicated on the drawing as “−2.0 V”) and the first pulse voltage. Two pulse voltages (voltage +4.0 [V], pulse width 35 [nsec], expressed as “+4.0 V” in the drawing) are alternately applied, and the resistance value (readout resistance value) measured after each voltage application. The measurement result range is displayed on a graph. In the reading process, a resistance value measured by applying a voltage of 0.5 [V] is shown.

  According to FIG. 21, as in FIG. 3, a phenomenon in which the resistance value transitions between a high resistance and a low resistance under a voltage condition, that is, a switching phenomenon is observed. And it turns out that the same switching phenomenon as FIG. 3 can be produced, without passing through the forming process which applies a high voltage previously with respect to an initial state, and forms a current pathway in an insulator.

  FIG. 22 shows the result of atomic% profile analysis by EDX on the variable resistor film 51 manufactured using the Co film as the resistive material film by the above method, as in FIG. In addition, as a measuring object, the cobalt oxide whose film thickness of the variable resistor 51 is 10 nm was used. In addition, the atoms to be analyzed by EDX were also measured as O, Si, and a resistive material film material (ie, Co) for the same reason as in FIG. Further, in FIG. 22, as in FIG. 4, the direction from the second interlayer insulating film 16 toward the variable resistor 51 and the first interlayer insulating film 13 is the scanning direction d1, and the scanning direction d1 from the second interlayer insulating film 16 side. Are plotted on the horizontal axis, and the content percentage of each atom is plotted on the vertical axis. (1) is O, (2) is Si, and (3) is Co.

  According to FIG. 22, in the variable resistor film 51, the content percentage of O in (1) decreases as it advances in the scanning direction d1, while the content percentage of Co in (3) increases. . From this, it can be seen that in the variable resistor film (cobalt oxide film) 51, oxygen has a concentration gradient in the same direction as the scanning direction d1, while Co has a concentration gradient in the direction opposite to d1. . That is, in the variable resistor film 51, oxygen is most present in the second interlayer insulating film 16 side, that is, in the upper region of the cobalt oxide film 51, and in the first interlayer insulating film 13 side, that is, in the lower region of the cobalt oxide film 51. This shows that oxygen is relatively small, while a large amount of Co, which is a metal, is present. In other words, the upper region with a high oxygen concentration is in a high resistance state because the Co concentration is low, while the lower region with a low oxygen concentration has a high resistance so that the Co concentration becomes relatively high even if it is partially oxidized. It is thought that it has not become.

  Therefore, even when Co is used as the resistance material film, the variable resistor 51 has a relatively high resistance value in the upper region (region 51a in FIG. 5) and the lower region (in FIG. 5) as in the case of TiN. It can be seen that the resistance value is relatively low in the region 51b). Therefore, when a voltage is applied to the variable resistor 51, the first direction orthogonal to the direction d1 having the oxygen concentration gradient, that is, between two points (two regions) separated in the first direction d2 in FIG. When a voltage is applied, the current I can flow in the vicinity of the lower region 51 b having a relatively low resistance in the variable resistor 51. As described above in the first embodiment, since there is no region having a high resistance value, that is, an insulator region in this current path, it is not necessary to perform a forming process for forming a current path in the insulator in advance. On the other hand, since the variable resistor 51 shows a constant oxygen concentration distribution as shown in FIG. 22, it does not function easily as a perfect conductor because it easily exhibits switching characteristics by voltage application as shown in FIG. It functions as a variable resistance element that changes the value.

  Accordingly, the present embodiment also has two electrodes (first electrode 14 and second electrode 17) for applying a voltage to the variable resistor 51, as in the first embodiment. The first connection region 14x in which the first electrode 14 and the variable resistor 51 are electrically connected and the second connection region 17x in which the second electrode 17 and the variable resistor 51 are electrically connected include the variable resistor 51. It is the structure formed apart in the 1st direction d2 perpendicular | vertical to the direction d1 which an inside oxygen concentration gradient has (refer FIG.1 (k) and FIG. 5). Therefore, by applying a voltage between these two electrodes, a path of current I flowing from one electrode through the variable resistor 51 to the other electrode is used as a relatively conductive material in the variable resistor 51. Since the high area 51b can be used, it is not necessary to perform a forming process in advance. That is, even when the Co film is used as the resistance material film, the same effect as that of the TiN film can be obtained.

  Therefore, in the case where the element of the present invention is manufactured by the method described in the second to fifth embodiments, even when Co is used instead of TiN as the resistance material film, the switching characteristic is exhibited without performing the forming process. The same effect as in the case of the second to fifth embodiments can be obtained.

  In this embodiment, the case where the Co film is used as the resistance material film has been described. However, the same effect can be obtained even when the Ta film or the Ni film is used.

  FIG. 23 is a graph showing the switching characteristics of the element 1 of the present invention manufactured by the same method as that of the above embodiment except that the Ta film is deposited in Step # 15. As in the graphs of FIGS. The characteristics of the element 1 of the present invention manufactured with the variable resistor 15 having a thickness of 30 nm are shown. The switching characteristic acquisition method and the display method on the graph are also the same as those shown in FIGS.

  According to FIG. 23, similar to the case of FIG. 3 and FIG. 21, a switching phenomenon is observed in which the resistance value changes between a high resistance and a low resistance under a voltage condition. And it turns out that the same switching phenomenon as FIG. 3 can be produced, without passing through the forming process which applies a high voltage previously with respect to an initial state, and forms a current pathway in an insulator.

  FIG. 24 shows the result of atomic% profile analysis by EDX on the variable resistor film 51 manufactured using the Ta film as the resistance material film, similarly to the case of FIGS. As a measurement object, tantalum oxide having a variable resistor 51 with a film thickness of 10 nm was used. Note that the measurement method and the graph display method for obtaining the graph of FIG. 24 are the same as those of FIGS. 4 and 22, and (1) is O, (2) is Si, and (3) is Ta. Respectively.

  According to FIG. 24, the content% of O in (1) decreases in the scanning direction d1 in the variable resistor film 51, while the content% of Ta in (3) increases. . From this, it can be seen that in the variable resistor film (tantalum oxide film) 51, oxygen has a concentration gradient in the same direction as the scanning direction d1, while Ta has a concentration gradient in the direction opposite to d1. . That is, as in the case of using TiN and Co as the resistance material film, the variable resistor film 51 has the most oxygen in the second interlayer insulating film 16 side, that is, in the upper region of the tantalum oxide film 51, and the first interlayer In the insulating film 13 side, that is, in the lower region of the tantalum oxide film 51, oxygen is relatively low, while a large amount of Ta, which is a metal, is present. Therefore, even when Ta is used as the resistive material film, the variable resistor 51 has a relatively high resistance value in the upper region (region 51a in FIG. 5) and the lower region (see FIG. 5) as in the case of TiN and Co. It can be seen that the resistance value is relatively low in the region 51b) in FIG. Therefore, when a voltage is applied to the variable resistor 51, the first direction orthogonal to the direction d1 having the oxygen concentration gradient, that is, between two points (two regions) separated in the first direction d2 in FIG. When a voltage is applied, the current I can flow in the vicinity of the lower region 51 b having a relatively low resistance in the variable resistor 51. As described above in the first embodiment, since there is no region having a high resistance value, that is, an insulator region in this current path, it is not necessary to perform a forming process for forming a current path in the insulator in advance. On the other hand, since the variable resistor 51 shows a constant oxygen concentration distribution as shown in FIG. 24, the variable resistor 51 does not easily function as a perfect conductor because of its switching characteristics as shown in FIG. It functions as a variable resistance element that changes the value.

  FIG. 25 is a graph showing the switching characteristics of the element 1 of the present invention manufactured by the same method as the above embodiment except that the Ni film is deposited in Step # 15. Similarly, the characteristics of the element 1 of the present invention manufactured with the variable resistor 15 having a thickness of 30 nm are shown. The switching characteristic acquisition method and the display method on the graph are also the same as those shown in FIGS.

  According to FIG. 25, as in the case of FIG. 3 and FIG. 21, a switching phenomenon is observed in which the resistance value changes between a high resistance and a low resistance under a voltage condition. And it turns out that the same switching phenomenon as FIG. 3 can be produced, without passing through the forming process which applies a high voltage previously with respect to an initial state, and forms a current pathway in an insulator.

  FIG. 26 shows the result of atomic% profile analysis by EDX on the variable resistor film 51 manufactured using the Ni film as the resistance material film, similarly to the case of FIG. 4 and FIG. As a measurement object, nickel oxide whose variable resistor 51 has a thickness of 10 nm was used. The measurement method and the graph display method for obtaining the graph of FIG. 26 are also the same as those in FIGS. 4 and 22, and (1) is O, (2) is Si, and (3) is Ni. Respectively.

  According to FIG. 26, in the variable resistor film 51, the content percentage of O in (1) decreases as it proceeds in the scanning direction d1, while the content percentage of Ni in (3) increases. . From this, it can be seen that in the variable resistor film (nickel oxide film) 51, oxygen has a concentration gradient in the same direction as the scanning direction d1, while Ni has a concentration gradient in the direction opposite to d1. . That is, as in the case of using TiN or Co as the resistance material film, the variable resistor film 51 has the largest amount of oxygen in the second interlayer insulating film 16 side, that is, in the upper region of the nickel oxide film 51, and the first interlayer In the insulating film 13 side, that is, in the lower region of the nickel oxide film 51, oxygen is relatively low, while a large amount of Ni, which is a metal, is present. Therefore, even when Ni is used as the resistance material film, the variable resistor 51 has a relatively high resistance value in the upper region (region 51a in FIG. 5) and the lower region (FIG. It can be seen that the resistance value is relatively low in the region 51b) in FIG. Therefore, when a voltage is applied to the variable resistor 51, the first direction orthogonal to the direction d1 having the oxygen concentration gradient, that is, between two points (two regions) separated in the first direction d2 in FIG. When a voltage is applied, the current I can flow in the vicinity of the lower region 51 b having a relatively low resistance in the variable resistor 51. As described above in the first embodiment, since there is no region having a high resistance value, that is, an insulator region in this current path, it is not necessary to perform a forming process for forming a current path in the insulator in advance. On the other hand, since the variable resistor 51 shows a constant oxygen concentration distribution as shown in FIG. 26, the variable resistor 51 does not easily function as a perfect conductor because of its switching characteristics as shown in FIG. It functions as a variable resistance element that changes the value.

  As described above, the material that can be used as the resistance material film is not limited to TiN, and even if Co, Ta, or Ni is used, the same effects as those in the first to fifth embodiments can be obtained. Further, the present invention is not limited to the metal materials exemplified in the present embodiment, and the same effect can be obtained when other transition metals (Cu, V, Zn, Nb, W, etc.) or transition metal nitrides are used as the resistance material film. Can be shown. In this case, the variable resistor 51 included in the variable resistance element is formed of the metal oxide or metal oxynitride generated by oxidizing the metal or metal nitride used as the resistance material film.

[Another embodiment]
Hereinafter, another embodiment will be described.

<1> In the first embodiment described above, the first interlayer insulating film 13 deposited in step # 11 and the second interlayer insulating film 16 deposited in step # 18 are both SiO ₂ films. The interlayer insulating film is not limited to the SiO ₂ film, and any appropriate insulating film having oxidation resistance such as a SiN film, a SiON film, a SiOF film, or a SiOC film can be used. Further, the first interlayer insulating film 13 and the second interlayer insulating film 16 may be formed of insulating films made of different materials. The same applies to each of the second and subsequent embodiments.

  <2> In the first embodiment described above, the electrode material films 14 and 17 formed in step # 13 and step # 20 are both W films, but other metal material films (Ti 2, Cu 2) exhibiting conductivity are used. , Fe, W, Ni, V, Co, or other transition metals, transition metal nitrides, or alloys containing Pt or Ir. In step # 11, the semiconductor substrate 11 serving as a base on which the first interlayer insulating film 13 is deposited has a transistor circuit and the like formed as appropriate. However, the circuit does not necessarily have to be formed. The same applies to each of the second and subsequent embodiments.

  <3> In step # 11 and step # 18 in the first embodiment described above, each interlayer insulating film is deposited by the CVD method. However, pulsed laser deposition, rf-sputtering, electron beam evaporation, thermal evaporation are performed. It is also possible to deposit using any suitable deposition technique such as spin-on deposition. The same applies to each of the second and subsequent embodiments.

<4> In the first embodiment described above, the oxidation process according to step # 17 is a thermal oxidation method using molecules containing oxygen such as O ₂ , O ₃ , H ₂ O, N ₂ O, NO in the gas species. In addition, a plasma oxidation method, an ion implantation method, or the like may be used. The same applies to each of the second and subsequent embodiments.

  <5> In the fourth and fifth embodiments described above, the conductive film 18 is a Pt film, but a transition metal such as Ti, Cu, Fe, W, Ni, V, Co, or a transition metal nitride, or It is also possible to form an alloy containing Pt or Ir. The same applies to the sixth embodiment.

The schematic sectional drawing of each process in the manufacturing process of 1st Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. The flowchart which shows the manufacturing process of 1st Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. Sectional view of variable resistance element according to the present invention, and graph showing switching characteristics Atomic content profile of variable resistance element and variable resistance film according to the present invention The schematic diagram which expanded partially the cross-section figure of the variable resistance element concerning this invention Another configuration example of the first embodiment of the variable resistance element according to the present invention Still another configuration example of the first embodiment of the variable resistance element according to the present invention. The schematic sectional drawing of each process in the manufacturing process of 2nd Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. The flowchart which shows the manufacturing process of 2nd Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. The schematic sectional drawing of each process in the manufacturing process of 3rd Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. The flowchart which shows the manufacturing process of 3rd Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. Another configuration example of the third embodiment of the variable resistance element according to the present invention Another configuration example of the third embodiment of the variable resistance element according to the present invention The schematic sectional drawing of each process in the manufacturing process of 4th Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. The flowchart which shows the manufacturing process of 4th Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. Another configuration example of the fourth embodiment of the variable resistance element according to the present invention Schematic sectional drawing of each process in the manufacturing process of 5th Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. The flowchart which shows the manufacturing process of 5th Embodiment of the manufacturing method of the variable resistance element which concerns on this invention. Another configuration example of the fifth embodiment of the variable resistance element according to the present invention Another configuration example of the fifth embodiment of the variable resistance element according to the present invention The graph which shows the switching characteristic of 6th Embodiment of the variable resistance element which concerns on this invention Atomic content profile of variable resistance film in sixth embodiment of variable resistance element according to present invention Another graph showing the switching characteristics of the sixth embodiment of the variable resistance element according to the present invention Another atomic content profile of the variable resistor film in the sixth embodiment of the variable resistance element according to the present invention Still another graph showing the switching characteristics of the sixth embodiment of the variable resistance element according to the present invention. Still another atomic content profile of the variable resistance film in the sixth embodiment of the variable resistance element according to the present invention Schematic structure diagram of variable resistance element with conventional configuration Equivalent circuit diagram showing one configuration example of 1T / 1R type memory cell Cross-sectional schematic diagram of a 1T / 1R type memory cell Equivalent circuit diagram showing one configuration example of 1R type memory cell Cross-sectional schematic diagram of 1R type memory cell

Explanation of symbols

1: Variable resistance element according to the present invention 11: Semiconductor substrate 12, 12c, 12d: Metal wiring 13: First interlayer insulating film (SiO ₂ film)
14, 14c: First electrode material film (W film), first electrode 14d: Second electrode 14x: First connection region 15, 15c, 15d: Resistance material film (TiN film)
16: Second interlayer insulating film (SiO ₂ film)
17: Second electrode material film (W film), second electrode 17x: Second connection region 18: Conductive film (Pt film)
20, 20c, 20d: Contact hole 30: Contact hole 51: Variable resistor film 101: Upper electrode 102: Variable resistor 103: Lower electrode 104: Memory cell array 105: Bit line decoder 106: Word line decoder 107: Source line decoder 111: Semiconductor substrate 112: Element isolation region 113: Gate insulating film 114: Gate electrode 115: Drain diffusion layer region 116: Source diffusion layer region 117: Contact plug 118: Lower electrode 119: Variable resistor 120: Upper electrode 121: Contact Plug 122: Contact plug 123: Bit line 124: Source line 131: Memory cell array 132: Bit line decoder 133: Word line decoder 141: Lower electrode wiring 142: Variable resistor 143: Upper part Pole wiring 210
BL1 to BLm: Bit line R: Variable resistance element SL1 to SLn: Source line T: Select transistor WL1 to WLn: Word line

Claims (13)

A first electrode, a second electrode, and a variable resistor formed between the two electrodes on a semiconductor substrate, and an electric resistance between the two electrodes according to application of a voltage pulse between the two electrodes. Is a variable resistance element that reversibly changes,
A first connection region that electrically connects the first electrode and the variable resistor, and a second connection region that electrically connects the second electrode and the variable resistor are in a predetermined first direction. Are spaced apart from each other,
The variable resistance element is made of a metal oxide or metal oxynitride having an oxygen concentration gradient in a direction orthogonal to the first direction. The first direction is a direction parallel to a substrate surface of the semiconductor substrate;
The variable resistance element according to claim 1, wherein the variable resistor has the oxygen concentration gradient in a direction orthogonal to a substrate surface of the semiconductor substrate. The first direction is a direction orthogonal to the substrate surface of the semiconductor substrate;
The variable resistance element according to claim 1, wherein the variable resistor has the oxygen concentration gradient in a direction parallel to a substrate surface of the semiconductor substrate.   The variable resistor includes an oxide or oxynitride of a transition metal containing at least one of Cu, Ni, V, Zn, Nb, Ti, W, Co, and Ta. Item 4. The variable resistance element according to any one of Items 1 to 3. It is a manufacturing method of the variable resistance element according to claim 1,
Forming a first electrode of a contact structure on a layer immediately above a predetermined metal wiring region on the semiconductor substrate;
Then, a second step of depositing and patterning a predetermined resistive material film as a material of the variable resistor on the entire surface immediately above the first electrode, and patterning;
Thereafter, an oxidation treatment is performed on the resistance material film, and the oxidation proceeds from the exposed surface of the resistance material film toward the inner side, whereby an oxygen concentration gradient in a direction perpendicular to the substrate surface of the semiconductor substrate is obtained. A third step of changing to the variable resistor having:
And a fourth step of forming the second electrode having a contact structure so as to come into contact with the variable resistor in a predetermined region except above the formation region of the first electrode. A method for manufacturing a variable resistance element. After the end of the second step, and before the start of the third step, a fifth step of thinning the resistive material film located at least above the formation region of the first electrode and providing a step in the resistive material film, Have
The third step oxidizes a portion corresponding to the thickness of the resistance material film thinned by the fifth step, so that the resistance material film in the region not thinned by the fifth step is oxidized. It is a process that leaves it partially in an unoxidized state,
The fourth step is a step of forming the second electrode having a contact structure in contact with the unoxidized resistive material film in a region where the unoxidized resistive material film exists. A method for manufacturing a variable resistance element according to claim 5. After the first step is finished and before the second step is started, a predetermined conductive film is formed in a region at least excluding the upper portion of the first electrode formation region, so that the conductive film formation region and the non-formation region are formed. A sixth step of providing a step between and
The second step is a step of patterning after depositing the resistive material film over the entire surface including the surface having the step.
The fourth step is a step of forming the second electrode having a contact structure in contact with the conductive film in a region where the conductive film is formed immediately below the variable resistor. 6. The method of manufacturing a variable resistance element according to claim 5, wherein   The sixth step is a step of forming the conductive film after forming the step interlayer insulating film directly under the conductive film forming region after the first step, and forming the step interlayer insulating film. The method of manufacturing a variable resistance element according to claim 7, wherein a step is provided between the conductive film formation region and the conductive film non-formation region by the conductive film and the conductive film. It is a manufacturing method of the variable resistance element according to claim 1,
A first step of depositing and patterning a predetermined resistive material film to be a material of the variable resistor on the entire surface;
Thereafter, an oxidation treatment is performed on the resistance material film, and the oxidation proceeds from the exposed surface of the resistance material film toward the inner side, whereby an oxygen concentration gradient in a direction perpendicular to the substrate surface of the semiconductor substrate is obtained. A second step of changing to the variable resistor having:
A third step of forming the first electrode of the contact structure and the second electrode of the contact structure spaced apart in a direction parallel to the substrate surface of the semiconductor substrate so as to contact the variable resistor; The manufacturing method of the variable resistance element characterized by having these. It is a manufacturing method of the variable resistance element according to claim 1,
A first step of forming the first electrode of a contact structure and the second electrode of a contact structure on a layer immediately above a plurality of metal wiring regions formed apart in a direction parallel to the semiconductor substrate;
Then, a second step of depositing and patterning a predetermined resistive material film as a material of the variable resistor on the entire surface immediately above the first electrode, and patterning;
Thereafter, an oxidation treatment is performed on the resistance material film, and the oxidation proceeds from the exposed surface of the resistance material film toward the inner side, whereby an oxygen concentration gradient in a direction perpendicular to the substrate surface of the semiconductor substrate is obtained. And a third step of changing to the variable resistor having: and a method of manufacturing a variable resistance element. After the end of the second step and before the start of the third step, the resistive material film located in a predetermined region sandwiched between the formation region of the first electrode and the formation region of the second electrode is thinned Having a fourth step,
The third step oxidizes a portion corresponding to the thickness of the resistive material film thinned by the fourth step, so that the resistive material film in the region not thinned by the fourth step It is a process that leaves it partially in an unoxidized state,
The fourth step is
By proceeding with oxidation corresponding to the film thickness of the resistance material film thinned in the third step, the resistance material film is changed to the variable resistor having an oxygen concentration gradient in a direction perpendicular to the substrate surface of the semiconductor substrate. In addition, the resistive material film in the region that has not been thinned by the third step is left in a partially unoxidized state, so that the resistive material film that remains in the layer immediately above the first electrode; The method of manufacturing a variable resistance element according to claim 10, wherein the resistance material film remaining on a layer immediately above the second electrode is divided by the variable resistor. After the completion of the first step and before the start of the second step, a predetermined conductive film is deposited and patterned on the first electrode and the second electrode, thereby patterning the conductive film to the first electrode. A fifth step of dividing the region into contact with the second electrode and the region in contact with the second electrode, and providing a step between the formation region and the non-formation region of the conductive film,
11. The method of manufacturing a variable resistance element according to claim 10, wherein the second step is a step of depositing the resistive material film on the entire surface including the surface having the step and then patterning.   The resistance material film is composed of a transition metal containing at least one of Cu, Ni, V, Zn, Nb, Ti, W, Co, and Ta, or a transition metal nitride. Item 15. The method for manufacturing a variable resistance element according to any one of Items 5 to 12.