Conductive oxide transition zone and contain the phase-changing memory unit of this transition zone
Technical field
The present invention relates to structure, preparation method and the material of phase transition storage, refer in particular to the heat efficiency that improves phase transition storage work and conductive oxide transition zone and its implementation that reduces phase-change memory cell power consumption.The invention belongs to microelectronics nano material and device preparation field.
Background technology
Phase transition storage (Phase Change Memory; PCM) be a kind of emerging semiconductor memory; It is to be storage medium with the chalcogenide compound; Utilize electric energy (heat) to make material between crystalline state (low-resistance) and amorphous state (high resistant), transform writing and wiping of realization information each other, the variation of leaning on measuring resistance of reading of information realizes.Compare with present existing multiple semiconductor memory technologies; Comprise conventional volatibility technology; Like static random access memory (SRAM), dynamic random access memory (DRAM) etc.; And non-volatile technology, like ferroelectric random memory (FeRAM), Electrically Erasable Read Only Memory (EEPROM), flash memory (FLASH) etc., have non-volatile, have extended cycle life (>10
13Inferior), component size is little, low in energy consumption, can multistagely store, read at a high speed, anti-irradiation, high-low temperature resistant (55~125 ℃), anti-vibration, anti-electronic jamming and manufacturing process advantages such as simple (can and prior integrated circuit process be complementary).Therefore not only will be widely applied to civilian daily portable electronic products, and huge potential application arranged in military fields such as Aero-Space.Major companies such as existing in the world Ovonyx, Intel, Samsung, Hitachi, STMicroelectronics and BritishAerpspace are carrying out the R&D work of the aspects such as perfect and manufacturability of technology in the research of carrying out the PCM memory.
Low pressure and low-power consumption when present of paramount importance research focus is to realize the phase transition storage operation.T type structural phase-change memory unit for commonly used discover that the heat that really is applied to the phase transformation of sulphur based material thin layer only accounts for 0.2~1.4% of outside heat supplied total value, and 60~72% heat returns the substrate direction through end W electrode diffusion.Too much heat must cause the increase of operating voltage/electric current in the phase transition process via scattering and disappearing of hearth electrode; Energy consumption increases; Have influence on and the voltage/current of CMOS coupling, and the too much heat that diffuses to the device bottom is potential unfavorable factor for the stability of the CMOS work of bottom.In addition; Contain in the phase-change material of Sb and Te element; In the process of phase transformation operation; Prolonged and repeated high temperature is write and is wiped the component segregation that operation can cause material internal itself, and Sb or Te be to the segregation at the interface of phase-change material and dielectric material, and also is proved to be the very big threat to device reliability with phenomenon that active electrode material reacts.
Given this, be necessary to propose a kind of new technical scheme to address the above problem in fact.
Summary of the invention
The phase-changing memory unit that the technical problem that the present invention will solve is that a kind of conductive oxide transition zone is provided and contains this transition zone; Can improve the operation heat efficiency of phase transition storage; And improve the operating reliability of device simultaneously, prolong the device purpose in useful life thereby reach.
In order to solve the problems of the technologies described above, the present invention adopts following technical scheme:
A kind of conductive oxide transition zone is applied to phase transition storage, and said phase transition storage comprises hearth electrode and chalcogenide compound thin layer; Said conductive oxide transition zone is between hearth electrode and chalcogenide compound thin layer; The material of said conductive oxide transition zone is the oxide with conductive characteristic.
Wherein, the fusing point of the material of said conductive oxide transition zone is 600~2500 ℃; Thermal conductivity is 0.1~120W/mK.
As preferred version of the present invention, the material of said conductive oxide transition zone comprises LaNiO
3, LaSrCoO
3, LaSrMnO
3, SrRuO
3, CaRuO
3One of them, or mix the SrTiO of Nb
3The thickness of said conductive oxide transition zone is 2~10nm.
A kind of phase-changing memory unit comprises hearth electrode and chalcogenide compound thin layer, also comprises the conductive oxide transition zone between hearth electrode and chalcogenide compound thin layer, and the material of said conductive oxide transition zone comprises LaNiO
3, LaSrCoO
3, LaSrMnO
3, SrRuO
3, CaRuO
3One of them, or mix the SrTiO of Nb
3, be preferably LaNiO
3, thickness is 2~10nm.
Wherein, said hearth electrode is the W electrode.
A kind of preparation method of phase-changing memory unit comprises the steps:
(1) use acetone and alcoholic solution, under the ultrasonic wave effect, clean substrate, on substrate, prepare the conductive oxide transition zone then, its thickness is 2~10nm;
(2) on the conductive oxide transition zone of step (1) preparation, prepare chalcogenide compound thin layer and TiN film successively;
(3) use the micro-nano process technology, form the column structure of forming by TiN film, chalcogenide compound thin layer, conductive oxide transition zone;
(4) on step (3) resulting structures, prepare one deck SiO again
2Cover layer uses the micro-nano process technology, at SiO
2Prepare the column hole in the cover layer;
(5) on step (4) resulting structures, prepare the Al electrode layer again, make Al get into SiO
2Intratectal column hole contacts with TiN, uses micro-nano process technology etching Al electrode layer, draws upper and lower electrode.
Wherein, said conductive oxide transition zone, chalcogenide compound thin layer, TiN film, SiO
2The preparation method of cover layer and Al electrode layer comprises: sputtering method, evaporation, atomic layer deposition method, chemical vapour deposition technique, metallo-organic decomposition process and laser assistant depositing method.
Described micro-nano process technology comprises uv-exposure, develops, peels off method and reactive ion etching.
Described substrate comprises: single crystalline Si sheet, the lower electrode layer that on the single crystalline Si sheet, covers, the SiO that on lower electrode layer, covers
2Adiabatic dielectric layer; Said SiO
2There is hole in the adiabatic dielectric layer; Comprise the column W electrode that communicates with lower electrode layer in the hole, W top of electrodes and SiO
2Adiabatic dielectric layer top is concordant.
The material of said conductive oxide transition zone comprises LaNiO
3, LaSrCoO
3, LaSrMnO
3, SrRuO
3, CaRuO
3One of them, or mix the SrTiO of Nb
3
Described chalcogenide compound thin layer is the phase change material film layer, and its material comprises Sb
2Te
3, Ge
1Sb
4Te
7, Ge
1Sb
2Te
4Or Ge
2Sb
2Te
5In a kind of, or it is through one or both compounds that obtain after element modified among doping N, O, Si, Sn, Ag or the In.
Compared to prior art, beneficial effect of the present invention is:
The raising of the phase transition storage heat efficiency that the present invention proposes is to use the conductive oxide transition zone to insert between phase-change material and the end W electrode; Reduce the diffusion of heat to end W electrode; And heat remained on phase-change material inside; Cut down the consumption of energy thereby reach, improve the purpose of the heat efficiency, all have stable physical characteristic (resistivity, film thickness, film roughness, thermal conductivity and specific heat etc.) in the temperature range of this conductive oxide transition zone on room temperature to phase-change material fusing point; Especially have good thermal stability, good adhesiveness is arranged with phase-change material, end W electrode and dielectric material all around.
The operating reliability of the raising device that the present invention proposes is; The conductive oxide buffer layer material can effectively suppress Sb and two kinds of elements of Te in the phase-change material to the diffusion of end W electrode direction; And buffer layer material not can with end W electrode and phase-change material generation chemical reaction; Thereby guaranteed the consistency of operation when device recycles, the reliability and the life-span of having improved device.
Description of drawings
Fig. 1~7th, phase-changing memory unit of the present invention prepares the process sketch map, wherein
Fig. 1 is a preparation conductive oxide transition zone sketch map on substrate;
Fig. 2 is preparation chalcogenide compound thin layer and a TiN film sketch map on the conductive oxide transition zone;
Fig. 3 is for forming TiN/ chalcogenide compound/conductive oxide transition zone column structure sketch map;
Fig. 4 is for covering SiO
2The cover layer sketch map;
Fig. 5 is at SiO
2Prepare column hole sketch map in the cover layer;
Fig. 6 is at SiO
2Preparation Al electrode layer sketch map on the cover layer;
Fig. 7 is for forming Al upper/lower electrode sketch map.
Mark explanation among the figure:
1 single crystalline Si sheet substrate
2 bottom electrode Ti/TiN/Al layers
3 W electrodes
4 SiO
2Adiabatic dielectric layer
5 conductive oxide transition zones
6 chalcogenide compound thin layers
7 TiN films
8 SiO
2Cover layer
9 Al electrode layers
Embodiment
Further specify practical implementation step of the present invention below in conjunction with accompanying drawing, for the convenience that illustrates, accompanying drawing is not proportionally drawn.
Embodiment one
A kind of phase-changing memory unit comprises hearth electrode and chalcogenide compound thin layer, also comprises the conductive oxide transition zone between hearth electrode and chalcogenide compound thin layer.Wherein, the fusing point of said conductive oxide buffer layer material is 600 ℃~2500 ℃; Thermal conductivity is 0.1~120W/mK.
The material of conductive oxide transition zone should have higher thermal stability, at the chalcogenide compound fusing point (like Ge
2Sb
2Te
5Fusing point~600 ℃) on still keep its thermal stability under the temperature conditions, promptly require this kind buffer layer material to have fusing point greater than chalcogenide compound.And in the temperature range between the fusing point of room temperature to chalcogenide compound, its fundamental property of the film of this kind material is that physical property (resistivity, film thickness, film roughness, thermal conductivity and specific heat etc.) does not have violent variation.Also be can be not under the temperature conditions of this kind material more than the fusing point of chalcogenide compound with chalcogenide compound in arbitrary element generation chemical reaction, have the ability of chalcogenide compound interior element that stop to the dielectric material diffusion.
And this kind material should have the thermal conductivity lower than hearth electrode (as lower than hearth electrode W (174W/mK)) or near the thermal conductivity of crystalline phase-change material (as near crystalline state Ge
2Sb
2Te
5Thermal conductivity~0.28W/mK), can heat be remained on phase-change material inside, cut down the consumption of energy thereby reach, improve the purpose of the heat efficiency.
The material of conductive oxide transition zone also should have preferably conductive characteristic can avoid introducing bigger electric capacity.
In addition, the material of conductive oxide transition zone also should be able to use any one preparation in sputtering method, evaporation, atomic layer deposition method, chemical vapour deposition technique, metallo-organic decomposition process or the laser assistant depositing method.
The material of said conductive oxide transition zone can comprise LaNiO
3, LaSrCoO
3, LaSrMnO
3, SrRuO
3, CaRuO
3One of them, or mix the SrTiO of Nb
3, be preferably LaNiO
3, its thickness is 2~10nm, specifically looks preparation condition and decides.
Referring to Fig. 1~7, the preparation method of said phase-changing memory unit comprises the steps:
(1) uses acetone and alcoholic solution successively, under the ultrasonic wave effect, cleaned substrate each 3 minutes; Toasted substrate afterwards 20 minutes, baking temperature is 120 ℃; On substrate, as shown in Figure 1 then, the method conductive oxide transition zone 5 of use magnetron sputtering, its thickness is 2~10nm, is preferably 5nm, base vacuum is 4 * 10 during sputter
-6Torr, operating air pressure is 0.18Pa during sputter, the material of the conductive oxide transition zone 5 of preparation is LaNiO
3, its fusing point is 2150 ℃; Thermal conductivity is 10W/mK;
Described substrate comprises: single crystalline Si sheet 1, at lower electrode layer 2 that covers on the single crystalline Si sheet 1 and the SiO that on lower electrode layer 2, covers
2Adiabatic dielectric layer 4; Said SiO
2There is hole in the adiabatic dielectric layer 4; Comprise the column W electrode 3 that communicates with lower electrode layer 2 in the hole, W electrode 3 tops and SiO
2Adiabatic dielectric layer 4 tops are concordant.
(2) as shown in Figure 2, on conductive oxide transition zone 5, use the method for magnetron sputtering successively to deposit chalcogenide compound thin layer 6 and TiN film 7 respectively, thickness is respectively 200nm and 20nm; The material of the thin layer of chalcogenide compound described in the present embodiment 6 is that phase-change material is Ge
2Sb
2Te
5Or it is through one or both compounds that obtain after element modified among doping N, O, Si, Sn, Ag or the In; Base vacuum is 4 * 10 during sputter
-6Torr, operating air pressure is respectively 0.16Pa and 0.40Pa during sputter, and sputtering power is respectively 200W and 400W;
(3) as shown in Figure 3; Use photoetching processes such as uv-exposure; Carve the square that the length of side is 3~5 μ m; Use method etching TiN film 7, chalcogenide compound thin layer 6 and the conductive oxide transition zone 5 of reactive ion etching; The TiN/ chalcogenide compound that formation is made up of TiN film 7, chalcogenide compound thin layer 6, conductive oxide transition zone 5/conductive oxide transition zone column structure, its cross section is the square of the length of side 3~5 μ m, the thin layer on W electrode 3 tops that this step will link to each other with the substrate hearth electrode simultaneously all etches away;
(4) as shown in Figure 4, on step (3) resulting structures, use the method for ultra vacuum electron beam evaporation to deposit one deck SiO again
2Film, thickness are 200nm, promptly form SiO
2Cover layer 8;
(5) as shown in Figure 5, use uv-exposure at SiO
2Make the square of the length of side 1~2 μ m on the cover layer by lithography, the square center that makes by lithography in this square center and the step (3) overlaps, and the method for using reactive ion etching is at SiO
2Etch the column hole in the cover layer 8; Etching depth is with till reaching TiN film 7 tops; Attention can not the transition etching; This will not make TiN film 7 or its underpart chalcogenide compound layer 6 by over etching and attenuate or cause surface roughening, the W electrode 3 top SiO that this step will link to each other with the substrate hearth electrode simultaneously
2Cover layer 8 etches away;
(6) as shown in Figure 6, and then use the method depositing Al electrode layer 9 of ultra vacuum electron beam evaporation above that, thickness is 300nm, makes Al get into SiO
2Cover layer 8 cylindrical holes contact with TiN is intact;
(7) last; Use uv-exposure on the Al electrode layer, to make the square of the length of side 30~50 μ m by lithography, the square center that makes by lithography in this square center and the step (5) overlaps, and toasts 20 minutes in 120 ℃; Adopt wet etching Al electrode layer 9 under the phosphoric acid medium effect of 65 ℃ of water-baths then; Drawn upper and lower electrode simultaneously, this has promptly accomplished the preparation of phase-changing memory unit, and is as shown in Figure 7.
In addition, can also heat-treat under given conditions, can improve film interface transition zone and chalcogenide compound; Released heat stress; Further reduce the possibility of element counterdiffusion, reduce the influence of change in volume in the chalcogenide compound thin film phase change process, thereby can guarantee the consistency that device is operated in recycling process; Improve the reliability of device work, and then improve its useful life.
Embodiment two
Adopt identical technical scheme with embodiment one, difference is the material of the conductive oxide transition zone of preparation in the step (1) is changed to LaSrCoO
3, LaSrMnO
3, SrRuO
3, CaRuO
3Deng material, or mix the SrTiO of Nb
3, also can reach identical technique effect.The fusing point of these conductive oxide materials is 600 ℃~2500 ℃; Thermal conductivity is 0.1~120W/mK.Wherein, these materials and preparation method thereof are those skilled in the art's known technology, and innovative point of the present invention is not these materials itself, so repeat no more at this.
Embodiment three
Adopt identical technical scheme with embodiment one, difference is the material of the chalcogenide compound thin layer described in the step (2) is replaced with Sb
2Te
3, Ge
1Sb
4Te
7Or Ge
1Sb
2Te
4In a kind of, or it is through one or both compounds that obtain after element modified among doping N, O, Si, Sn, Ag or the In.
Phase-changing memory unit in the foregoing description is used probe or lead extraction electrode, load power on signal, various performances that just can test cell.Test result is following:
Can find out obviously that from embodiment the present invention mainly concentrates in conventional P CM structure, between phase transformation chalcogenide compound and end W electrode, implant the thick particular conductivity oxide transition zone of one deck 5nm.The conductive oxide transition zone all has good adhesive force with thin layer up and down; Do not have the thermal diffusion phenomenon to take place, and have, scatter and disappear in a large number through end heating W electrode thereby suppress heat effectively than the low thermal conductivity of end heating W electrode; Have the device of raising thermal effect, reduce the remarkable effect of power consumption.
Other process conditions that relate among the present invention are the common process condition, belong to the category that those skilled in the art are familiar with, and repeat no more at this.
The foregoing description is the unrestricted technical scheme of the present invention in order to explanation only.Any technical scheme that does not break away from spirit and scope of the invention all should be encompassed in the middle of the patent claim of the present invention.