CN1698203A - Memory element and storage device using this - Google Patents

Memory element and storage device using this Download PDF

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Publication number
CN1698203A
CN1698203A CN 200480000388 CN200480000388A CN1698203A CN 1698203 A CN1698203 A CN 1698203A CN 200480000388 CN200480000388 CN 200480000388 CN 200480000388 A CN200480000388 A CN 200480000388A CN 1698203 A CN1698203 A CN 1698203A
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memory element
electrode
sample
coating
noncrystalline film
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CN100378998C (en
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荒谷胜久
河内山彰
石田实
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Sony Corp
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Sony Corp
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Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor storage element which can easily record and read information, can stably hold contents recoded under a high temperature environment or at the time of long preservation and can easily be manufactured by a comparatively simple manufacturing method, and to provide a semiconductor storage using the element.

Description

Memory element and use the storage device of this memory element
Technical field
The present invention relates to a kind of memory element, wherein record information, and relate to a kind of storage device that uses this memory element.
Background technology
In the information equipment as computer, high-speed cruising and high density DRAM are widely used in random access storage device.
But, because the manufacturing process of DRAM is too complicated, to compare with uniprocessor with the conventional logical circuit LSI that is used for electric equipment, its production cost is too high.
Equally, DRAM is a kind of volatile memory, and information will disappear when supply of electric power is interrupted, and needs refresh operation frequently, and just the information of reading in is read out and is amplified the operation that also is read once more once more.
Therefore, for example, proposed FeRAM (ferromagnetic random access storage device) and MRAM (magnetic random reference to storage) and other kind, promptly can not disappear when cutting off supply of electric power information as nonvolatile storage.
Under the situation of these memories, do not having to read in the information maintenance for a long time under the electric power.
Equally, under the situation of these memories,, do not need to carry out refresh operation, and can determine that energy consumption can be reduced largely owing to be nonvolatile storage.
But, for above-mentioned nonvolatile storage, with the corresponding to situation of miniaturization of the memory element that constitutes each storage element under, be difficult to guarantee characteristic as memory element.
Therefore, it is very difficult element being narrowed down to the restriction of design discipline and the restriction of manufacturing process.
Thereby, a kind of novel memory cell is proposed, it is as having the memory that is suitable for described structure of dwindling.
This memory element has a kind of like this structure, and the ion conductor that wherein comprises a certain metal remains between two electrodes.
In addition, by making in two electrodes any one comprise metal in the described ion conductor, when applying between two electrodes under the voltage condition, the metal that comprises in described electrode diffuses in the described ion conductor with ionic species, thereby changes such as the resistance of ion conductor or the characteristic of electric capacity.
By utilizing these characteristics just can constitute a storage device, for example, referring to the patent documentation 1 and the non-patent literature 1 of back.
Especially, ion conductor, it comprises the solid solution of chalkogenide and metal, more particularly, it comprises the material of the silver, copper or the zinc that are dissolved among AsS, GeS or the GeSe, and comprises silver, copper or zinc (with reference to the patent documentation 1 of back) in the arbitrary electrode in two electrodes.
And, manufacture method as this memory element, and a kind of method has been proposed, wherein on substrate, accumulate the ion conductor that constitutes by chalkogenide, then, accumulation comprises the electrode of metal on described ion conductor, and, have the light that is higher than ion conductor optical gap energy at this place by irradiation then or by applying heat with metal diffusing in ion conductor, form the ion conductor that comprises metal.
And, proposed to use the various nonvolatile storages of crystallization oxidation material, and for example, in device with a kind of like this structure, in this structure at SrZrO 3Or keeping chromium-doped SrZrO between the top electrode of the bottom electrode of platinum and gold or platinum 3Crystalline material discloses a kind of memory, and by applying the voltage of opposed polarity, resistance reversibly changes (referring to the non-patent literature 1 of back).
But, do not clarified such as the details of principle.
The Japanese translation of patent documentation 1:PCT international patent application NO.2002-536840.
Non-patent literature 1:Nikkei Electronics, No.2003.1.20, the 1 02 page.
Non-patent literature 2:A.Beck.et.Al, Appl.Phys.Lett., 77, (2000), the 139th page.
But in the memory element of said structure, ion conductor comprises the solid solution of chalkogenide and metal, and a kind of metal, and promptly gold, copper or zinc are for example dissolved in advance, and making needs more to diffuse into the desired electric current of line item by metal ion.
Equally, the variation of the resistance value before and after record is smaller.
Therefore, when the information of reading and recording, it is very difficult that the content of identifying information becomes.
In addition, metal diffusing being had than the more light of the energy of described ion conductor or by heating to ion conductor and by irradiation makes the use of dissolving metal manufacture method therein make manufacturing process more complicated.
Equally, above-mentioned memory element, it has and comprises argent or copper and germanium-sulphur or the noncrystalline chalcogenide materials of germanium-selenium in top electrode or bottom electrode any one and be maintained at structure between these electrodes, such memory element has a problem, promptly because the rising of temperature causes crystallization in the chalcogenide film, change according to this properties of materials of described crystallization, and keeping section data to be changed to low-resistance condition under the high resistance condition originally in following time of hot environment or under long preservation or other condition.
When crystalline material during, compared some problems with adopting amorphous material, and be difficult to produce in enormous quantities with low cost as recording materials between described top electrode and bottom electrode.
At first, for the crystallization of growing, basic material is restricted, and for example produces using the demand of monocrystal material
Equally, for example, must carry out 700 degrees centigrade high-temperature process for obtaining fabulous crystalline quality.
And, need coating layer thickness to be for example 50nm or thicker for obtaining the high-performance crystallization, and the viewpoint of the aspect ratio during by described miniature processing, produce for size less than the problem in the miniature processing of for example 50nm.
Also have, need can not cause such as not matching with lattice constant and other problem owing to improve the additional materials of characteristic, described element is limited in special element set, thereby is difficult to obtain desirable characteristics.
In order to address the above problem, the invention provides a kind of memory element, wherein can easily read and can easily make with writing information and by relative simple manufacturing method, and a kind of storage device that uses this memory element.
In addition, the invention provides a kind of memory element, the content that wherein can easily read with writing information and wherein can stably keep under hot environment or in the time of long preservation being write down, and can easily make by relative simple manufacturing method; And a kind of storage device that uses this memory element.
Summary of the invention
Memory element according to the present invention has noncrystalline film, this noncrystalline film is between first electrode and second electrode, and wherein at least a element selected by germanium with from sulphur, selenium, tellurium and antimony of at least one electrode package argentiferous in first and second electrodes or copper and this noncrystalline film is formed.
According to storage device of the present invention, it comprises: memory element, this memory element has noncrystalline film, this noncrystalline film is between first electrode and second electrode, and wherein at least a element selected by germanium with from sulphur, selenium, tellurium and antimony of at least one electrode package argentiferous in first and second electrodes or copper and this noncrystalline film is formed; Be connected to the wiring of the described first electrode side; And the wiring that is connected to the described second electrode side; Wherein said memory element is arranged in a large number.
Structure according to the memory element of the invention described above, because noncrystalline film is between first electrode and second electrode, at least one electrode package argentiferous or copper in described first and second electrodes, and at least a element that this noncrystalline film is selected by germanium with from sulphur, selenium, tellurium and antimony is formed, thereby comes stored information by using the silver will be included in described electrode or copper to diffuse in this noncrystalline film with ionic species.
Especially, when applying positive voltage to one of electrode that comprises silver or copper and after this positive voltage is applied on the element, be contained in that silver in this electrode or copper diffuse in the described noncrystalline film with ionic species and combine and separated out with the electronics of another electrode part in the described noncrystalline film, make described noncrystalline film the resistance step-down and also make the resistance step-down of described element, thereby information can be stored.And, under this condition, when applying negative voltage to one of electrode that comprises silver or copper and after this negative voltage is applied on the element, the silver or the copper of separating out in another electrode side are ionized and turn back to one of described electrode, the resistance that makes the resistance of described noncrystalline film return to initial high-impedance state and described element also uprises, thereby the information that is write down can be wiped free of.
In addition, make it not comprise silver or the copper that becomes ion before record by constructing described noncrystalline film, the electric current that record is required is very little, and changes in resistance can be amplified.In addition, also can shorten the record required time.
Structure according to the storage device of the invention described above, owing to comprise according to above-mentioned memory element of the present invention, be connected the wiring of the first electrode side and be connected to the wiring of the second electrode side, and a large amount of described memory elements are arranged, so enter described memory element and can carry out recording of information and wiping by the electric current described wiring of flowing through.
Another memory element according to the present invention has the noncrystalline film between first electrode and second electrode, at least one electrode package argentiferous or copper in wherein said first and second electrodes, and described noncrystalline film is formed by oxide.
Another storage device according to the present invention comprises: memory element, and it has the noncrystalline film between first electrode and second electrode, at least one electrode package argentiferous or copper in described first and second electrodes, and noncrystalline film is formed by oxide; Be connected the wiring of the first electrode side and be connected to the wiring of the second electrode side, wherein a large amount of memory elements are arranged.
Structure according to another memory element of the invention described above, because noncrystalline film is maintained between first electrode and second electrode, at least one electrode package argentiferous or copper in described first and second electrodes, and noncrystalline film is formed by oxide, therefore the said structure of similar memory element of the present invention is included in the silver of described electrode or copper by use and diffuses in the described noncrystalline film and stored information with ionic species.
Structure according to another storage device of the invention described above, owing to comprise another memory element of the invention described above, be connected the wiring of the first electrode side and be connected to the wiring of the second electrode side, and a large amount of memory elements are arranged, thereby enter described memory element and can carry out recording of information and wiping by the electric current described wiring of flowing through.
According to the invention described above, writing down required electric current to memory element can be reduced, and changes in resistance also can be amplified before and after the record.
Therefore, the energy consumption of recorded information in an element can be reduced, and also reading of information can be easily carried out.
In addition, can shorten the record required time.
And, owing to use in the element changes in resistance in the particularly noncrystalline film of changes in resistance to carry out recording of information, therefore have the following advantages, promptly when element during by microminiaturization, the information that recorded information and storage are write down becomes easier.
Therefore, according to the present invention, recorded information and reading of this information can easily be carried out in storage device, and energy consumption is reduced, and can be configured to operation down at a high speed.Equally, can obtain integrated (towards high density) and the miniaturization of storage device.
In addition, can use the material and the manufacture method of the manufacturing process that is used to make conventional mos logic circuit to make, and therefore can not need special process, for example high-temperature process and rayed etc. according to memory element of the present invention.
In other words, can make memory element with simple relatively method.
Therefore, according to the present invention, can make memory element and storage device with low-cost, and cheap storage device is provided.Can improve the output of storage device equally.
Thus, the energy consumption of recorded information on the element can be reduced in, and also reading of this information can be easily carried out.
And, can shorten the record required time.
And, owing to use in the element changes in resistance in the particularly noncrystalline film of changes in resistance to carry out the information record, therefore have the following advantages, promptly when element during by microminiaturization, the information that recorded information and storage are write down becomes easier.
In addition, according to another memory element and another storage device of the invention described above, because high-resistance stable condition promptly when still keeping recorded data in hot environment or under the condition of long preservation time, has therefore strengthened reliability.
Therefore, according to another memory element of the present invention and another storage device, can obtain a kind of storage device, the information of wherein can easily carrying out writes down and reads, and can cut down the consumption of energy, and can carry out high-speed cruising, and guarantee the high reliability of heat resistanceheat resistant.And, can obtain integrated (towards high density) and the miniaturization of storage device.
Therefore, according to another memory element of the present invention and another storage device, can make the stable storage element and the storage device of heat resistanceheat resistant with low cost, and cheap storage device is provided.Can improve the output of storage device equally.
Description of drawings
Fig. 1 is structure (vertical cross-section) schematic diagram of the embodiment of memory element according to the present invention;
Fig. 2 A is the curve chart of measurement result of I-V characteristic that the memory element sample of Fig. 1 is shown;
Fig. 2 B is the curve chart that is illustrated in the measurement result of the I-V characteristic that adds silver-colored sample in the noncrystalline film;
Fig. 3 A and 3B are the curve charts that is illustrated in the measurement result of the I-V characteristic that adds silver-colored sample in the noncrystalline film;
Fig. 4 A and 4B illustrate the wherein curve chart of the measurement result of the I-V characteristic of the sample of Ge content variation in noncrystalline film;
Fig. 5 A and 5B illustrate the wherein curve chart of the measurement result of the I-V characteristic of the sample of Ge content variation in noncrystalline film;
Fig. 6 illustrates wherein to use the curve chart of tungsten as the measurement result of the I-V characteristic of the sample of bottom electrode and electrode layer;
Fig. 7 is that to illustrate wherein at noncrystalline film be the curve chart of measurement result of I-V characteristic of the sample of silverskin;
Fig. 8 A and 8B illustrate the wherein curve chart of the measurement result of the I-V characteristic of the sample of adding gadolinium in noncrystalline film;
Fig. 9 A is that the wherein curve chart of the measurement result of the I-V characteristic of the sample of adding silicon in noncrystalline film is shown to 9C;
Figure 10 A and 10B illustrate the wherein curve chart of the measurement result of the I-V characteristic of the sample of the coating layer thickness variation of the GeSbTe film of noncrystalline film;
Figure 11 A and 11B illustrate the wherein curve chart of the measurement result of the I-V characteristic of the sample of the coating layer thickness variation of the GeSbTe film of noncrystalline film;
Figure 12 is the curve chart of measurement result of I-V characteristic that the memory element sample of Fig. 1 is shown;
Figure 13 A is to illustrate wherein to use the curve chart of germanium oxide as the measurement result of the I-V characteristic of the sample of noncrystalline film to 13C; And
Figure 14 A and 14B illustrate wherein to use the curve chart of silica as the measurement result of the I-V characteristic of the sample of noncrystalline film.
Embodiment
Fig. 1 illustrates structure (vertical cross-section) schematic diagram of the embodiment of memory element according to the present invention.
Memory element 10 comprises: have on the substrate of high conductivity, for example at the (P of high-concentration dopant P type alloy ++) bottom electrode 2 that forms on the silicon substrate, and the multiple coating layer that comprises noncrystalline layer 4, top electrode 5, electrode layer 6 and conductive layer 7, this multiple coating layer is connected with bottom electrode 2 by the opening that forms in the insulating barrier 3 on the bottom electrode 2.
For example, TiW, titanium and tungsten can be used as bottom electrode 2.
For example, under the situation of using TiW as bottom electrode 2, described coating layer thickness for example can be set in 20nm to the scope of 100nm.
For example, through the photoresist of cure process; Usually be used as the SiO of semiconductor device 2And Si 3N 4Other material, for example SiON, SiOF, Al 2O 3, Ta 2O 5, HfO 2, ZrO 2Etc. inorganic material; And fluorine-based organic material and aromatic radical organic material can be used as insulating barrier 3.
At least a element that noncrystalline film 4 is selected by germanium with from sulphur, selenium, tellurium and antimony is formed.Wherein sulphur, selenium and tellurium belong to chalcogen.
For example, can use GeSbTe, GeTe, GeSe, GeS, GeSbSe, GeSbS etc.These materials have identical electrical characteristics and chemical characteristic for silver or copper.
In addition, for example, if necessary, noncrystalline film 4 can comprise Si (silicon) and other element, as rare earth elements such as gadolinium, As, Bi etc.
Be under the situation of noncrystalline film 4 when using GeSbTe for example, described coating layer thickness for example can be set at 10nm to 50nm.
Top electrode 5 comprises silver or copper.
Top electrode 5 can be by using coating constitute, and this coating comprises coating with the silver that for example is added in described noncrystalline 4 the composition or copper, silver coating, silver alloy coating, copper coating, copper alloy coating etc.
For example, using under the situation of GeSbTeAg as top electrode 5, described coating layer thickness for example can be set at 10nm to the scope of 30nm.In addition, for example under the situation of using silver, described coating layer thickness for example can be set to 3nm to the scope of 20nm.
The silver that is comprised in not comprising top electrode 5 or the material of copper are used to form the electrode layer 6 that is connected with described top electrode 5.
In addition, described electrode layer 6 constitutes by using a kind of element (for example titanium and tungsten etc. are used for the element of bottom electrode 2), in this element when it becomes ion its chemical valence greater than the silver or the copper that in described top electrode 5, comprise.
For example, also can be used as electrode layer 6 as the TiW of bottom electrode 2, titanium, tungsten etc.
Under the situation of using TiW as electrode layer 6, the thickness of described coating for example can be set to 20nm to 100nm.
Conductive layer 7 connecting wiring layer (not shown), and electrode layer 6 can preferably be a low contact resistance.
When TiW is used as described electrode layer 6, for example, consider that using AlSi is described conductive layer 7.
Using AlSi is under the situation of described conductive layer 7, and described coating layer thickness for example can be set to 100nm to the scope of 200nm.
Be noted that the structure of described conductive layer 7 also plays the effect of the wiring layer that connects described memory element 10, and also can use the described wiring layer that is directly connected to described electrode layer 6.
Make memory element 10 operations of one embodiment of the invention as follows, and can stored information.
At first, on the top electrode 5 that comprises silver or copper, apply positive potential (+electromotive force), and apply positive voltage, thereby top electrode 5 sides become positive to memory element 10.So, silver or copper become ionization from described top electrode 5; Diffuse in the described noncrystalline film 4; Combine with the electronics on bottom electrode 2 sides, and separated out.
Then, the resistance step-down of the silver in the described noncrystalline film 4 or copper increase and described noncrystalline film.Because originally the resistance of other layer is lower than described noncrystalline film 4, therefore the all-in resistance of described memory element 10 can be minimized by the resistance that reduces described noncrystalline film 4.
Subsequently, remove positive voltage, and when preventing that voltage is applied to described memory element 10, the maintenance resistance value becomes low condition.Therefore the recorded information possibility that becomes.
On the other hand, during the information that writes down when wiping, on the top electrode 5 that comprises silver or copper, apply negative potential (electromotive force), and apply negative voltage for memory element 10, thereby top electrode 5 sides become negative.So, the silver or the copper of separating out in bottom electrode 2 sides becomes ionization; Move in the described noncrystalline film 4; And revert to initial condition in described top electrode 5 sides.
Then, the resistance in minimizing of silver in the described noncrystalline film 4 or copper and the described noncrystalline film 4 uprises.Because originally the resistance of other layer is lower than described noncrystalline film 4, therefore the all-in resistance of described memory element 10 can be raise by the resistance of the described noncrystalline film 4 that raises.
Subsequently, remove negative voltage, and the voltage on being applied to described memory element 10 is kept high-resistance condition when being removed.Therefore, wipe the described information possibility that becomes.
For described memory element 10,, can fully carry out the record (writing) of institute's recorded information and wipe by repeating such process.
And, for example, when making high resistance state during corresponding to information " 1 ", can be changed to " 1 " and can be changed to " 0 " respectively by applying negative voltage " 1 " in the information recording process by applying positive voltage " 0 " in the information recording process corresponding to information " 0 " and low resistance state.
Be noted that at noncrystalline film described in above-mentioned information record and the erase process to keep noncrystalline (no crystallization) state, and phase transformation will never cause crystallization.
In other words, recording of information is to carry out under the voltage conditions that does not undergo phase transition in described noncrystalline film 4 with wiping.
Structure according to the memory element 10 of the foregoing description, at least a element that noncrystalline film 4 is selected by germanium with from sulphur, selenium, tellurium and antimony is formed, and top electrode 5 comprises silver or copper, thereby by making silver or copper with the ionic species utmost point 5 diffusion from power on and move in the noncrystalline film 4 and come recorded information.
Then,, particularly use the resistance variations of noncrystalline film 4 to carry out recording of information owing to use the changes in resistance of memory element 10, when described memory element 10 quilts are microminiaturized, the information that just can easily carry out recording of information and keep being write down.
And, because noncrystalline film 4 does not comprise silver or the copper that becomes ion, condition before recorded information and under the condition that described information is wiped free of, silver or copper accumulate in around the interface between top electrode 5 and the described noncrystalline film 4, and because silver or copper almost can not diffuse to described noncrystalline film 4 inside, the resistance in the described noncrystalline film 4 can maintain high-impedance state.
Therefore, the condition before recorded information and under the condition that described information is wiped free of can make the resistance value height of noncrystalline film 4, and compare the variation that can enlarge resistance value with the low-resistance value that information is recorded under the state.
Therefore, read and discern the information that is write down and become easy.
Also have, the electric current that record needs can diminish.This is to consider that silver or copper can excessively not exist in noncrystalline film 4, thereby the ion motion of silver or copper carries out smoothly.Needed electrorheological is very little then can to cut down the consumption of energy owing to write down.
Also have, the record required time also can be shortened.
In addition, according to the structure of the memory element 10 of the foregoing description, each bottom electrode 2, noncrystalline film 4, top electrode 5, electrode layer 6 and conductive layer 7 can be by being formed by the material of sputter.Can comprise that the target (target) of the composition of the material that is suitable for each layer carries out sputter by use.
Therefore, be not necessary such as at high temperature the heat treatment and the special process (making the technology of metal) of optical illumination from electrode diffusion.
In addition, can form described coating continuously by on same sputtering equipment, changing target.
Especially, can make memory element by material and the manufacture method (for example forming coating) in conventional mos logic circuit manufacturing process, used such as the conventional etch process of plasma or RIE etching etc. by the sputter electrode material.
Therefore, can make memory element 10 easily by simple relatively method.
For example, the memory element 10 of Fig. 1 can be with following method manufacturing.
At first, have on the substrate of high conductivity, for example on the silicon substrate that high concentration P type alloy mixes, accumulating for example bottom electrode 2 of TiW coating.
Next, form insulation film 3, subsequently, form opening in the insulation film 3 on described bottom electrode 2 to cover described bottom electrode 2.
Then, the described bottom electrode 2 lip-deep oxidized surfaces of etching, and remove thin oxide layer to obtain the favorable conductive surface.
Then, by the noncrystalline film 4 of GeSbTe coating for example of magnetron sputter reactor device fabrication for example.
Then, by the top electrode 5 of GeSbTeAg coating or silver coating for example of magnetron sputter reactor device fabrication for example.
Then, by magnetron sputter reactor the device fabrication for example for example electrode layer 6 of TiW coating and the conductive layer 7 of Production Example such as AlSi coating or copper coating.
And can maintain same magnetic keyholed back plate sputtering equipment under the identical vacuum state by use, and form noncrystalline film 4, top electrode 5, electrode layer 6 and conductive layer 7 with selected various materials continuously by changing sputter target.
Then, by for example plasma etching etc. noncrystalline film 4, top electrode 5, electrode layer 6 and conductive layer 7 are constituted patterns.Can be by being not the grinding of for example ion (ion milling) and RIE engraving methods such as (reactive ion etching (reactive ion etching)) the formation pattern of plasma etching yet.
As mentioned above, can make memory element shown in Figure 1 10.
Be noted that, in the memory element 10 of the foregoing description, though top electrode 5 constitutes and comprises silver or copper and bottom electrode and constitute and do not comprise silver or copper, only comprises the structure that all comprises silver or copper in silver or copper or top electrode and the bottom electrode simultaneously in the bottom electrode 2 and also can use.
When in adopting bottom electrode, comprising the structure of silver or copper, wish between described bottom electrode and substrate, to be provided with the electrode layer of the electrode layer 6 that is equal to Fig. 1 (comprise when being ionized chemical valence greater than the element of silver or copper).
Can constitute storage device (memory storage) by the rectangular memory element 10 of arranging a large amount of the foregoing descriptions.
For each memory element 10 is provided with the wiring that connects bottom electrode 2 sides and the wiring of the utmost point 5 sides that Connect Power, and for example each memory element 10 be disposed in these wirings the crosspoint around.
In addition, especially, for example on column direction, form bottom electrode 2 with respect to memory cell publicly; On line direction, form the wiring of connecting conductive layer 7 with respect to memory cell publicly; By selecting described bottom electrode 2 and applying electromotive force, that the storage element that is recorded is selected to wiring; And the electric current of memory element 10 that can be by flowing through this storage element carries out wiping of information record and institute's recorded information.
For the memory element 10 of the foregoing description, can easily carry out information record and information and read, capable of reducing energy consumption and shortening writing time.Therefore, when using described memory element 10 to constitute storage device, can easily carry out information record and information and read; Can reduce the energy consumption of whole storage device; And acquisition high-speed cruising.
In addition, when being miniaturized, utilize the memory element 10 of described embodiment, can easily carry out reading of information record and institute's recorded information, make it possible to obtain integrated (towards high density) and the miniaturization of storage device.
And, because the memory element 10 of the foregoing description can easily be made by simple method, can reduce the manufacturing cost of storage device and can improve manufacturing output.
[actual example]
Next, the memory element 10 of the foregoing description is made by actual, and its characteristic is studied.
＜experiment 1 〉
At first, have on the substrate of high conductivity, for example the thickness that accumulates as bottom electrode 2 by sputter on the silicon substrate that the P type alloy with high concentration mixes is the TiW coating of 100nm.
Next, form photoresist covering described bottom electrode 2, and after this, by lithoprinting expose and video picture to form opening (through hole) in the photoresist on bottom electrode 2.The size longitudinal length of described opening (through hole) is that 2 μ m are 2 μ m with walking crosswise length.
Subsequently, anneal with 270 degrees centigrade under vacuum, make photoresist become the sclerosis protective layer of insulation film 3, it is stable for temperature, etching etc.Be noted that the sclerosis protective layer is used to described insulation film 3,, and therefore when making this product, also can consider to use other material (silica coating etc.) as insulation film 3 because it is not difficult to this experiment.
Then, carry out etching by surface, and remove thin oxide layer to obtain the favorable conductive surface to the bottom electrode 2 that exposes by through hole.
Then, forming coating layer thickness by the magnetron sputter reactor device is that the GeSbTe coating of 25nm is as noncrystalline film 4.The composition of described GeSbTe is Ge 22Sb 22Te 56(numeral of being added is an atomic weight percentage).
In addition, forming coating layer thickness by the same magnetic keyholed back plate sputtering unit that keeps identical vacuum state is that the GeSbTeAg coating of 25nm is as top electrode 5.The composition of described coating GeSbTeAg is (Ge 22Sb 22Te 56) 41Ag 59(numeral of being added is an atomic weight percentage).
And, by the same magnetic keyholed back plate sputtering unit that keeps identical vacuum state form coating layer thickness be the TiW coating of 100nm as electrode layer 6, the AlSi coating that forms coating layer thickness then and be 100nm is as conductive layer 7.The composition of described TiW coating and AlSi coating is respectively Ti 50W 50And Al 97Si 3(numeral of being added is an atomic weight percentage).
Next, by using the lithoprinting of plasma etching apparatus, be of a size of 50 μ m * 50 μ m compositions on each layer on the insulation film of making by the sclerosis protective layer 3 in noncrystalline film 4, top electrode 5, electrode layer 6 and the conductive layer 7 of accumulation.
As mentioned above, made the memory element 10 of structure shown in Figure 1, and it is the sample 1 of described memory element 10.
For the sample 1 of described memory element 10, on the conductor layer 7 of top electrode 5 sides, apply positive potential (+electromotive force), and earth potential (ground potential) is connected with the rear side of substrate 1.
Then, the positive potential that is applied to described conductor layer 7 begins to increase from 0V, and measures the variation of electric current.But flow restricter is set to when electric current reaches 0.5mA and starts working, thereby is applied to the positive potential on the conductor layer 7, and the voltage that promptly is applied on the element 10 can not increase above this value again.
And, reaching 0.5mA from electric current and make flow restricter work, the electromotive force that is applied on the conductor layer 7 is reduced to 0V, and measures the variation of electric current.
Fig. 2 A shows the I-V indicatrix that is obtained.
In Fig. 2 A, should be appreciated that higher and memory element 10 is positioned at closed condition at initial condition resistance, and electric current surpasses threshold voltage vt h along with voltage and increases sharply; In other words, resistance step-down and enter opening.The information of should be understood that is to be recorded by such operation.
On the other hand, after this, by reducing voltage, electric current also reduces; Though the reduction amount of electric current is big and resistance increases step by step, the resistance that finally reaches enough is lower than the resistance of initial condition, and is held open state, should be understood that the information that is write down is held.
In the situation of this sample 1, resistance is roughly 2M Ω when descending voltage V=0.1V in off position, and is roughly 1K Ω under opening.
And, though be not shown in the characteristic pattern of Fig. 2 A, but the voltage of opposite polarity, it is the conductor layer 7 that negative potential (electromotive force) is applied to top electrode 5 sides, and the rear side of substrate 1 is connected with earth potential (ground potential), and applies the negative potential of V=-1V on conductor layer 7, after this, be set to 0V by electromotive force, can determine that resistance is returned to the high resistance of initial condition conductor layer 7.In other words, should be understood that by apply the information that negative voltage writes down in memory element 10 and can be wiped free of.
＜experiment 2 〉
In the GeSbTe of noncrystalline film 4, add silver, and its characteristic is studied.
At first, form the GeSbTeAg coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 81Ag 19(numeral of being added is an atomic weight percentage, and is hereinafter identical therewith), and other is identical with sample 1, and a memory element is made sample 2.
Next, form the GeSbTeAgO coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 70Ag 30, and other is identical with sample 1, and a memory element is made sample 3.
Next, form the GeSbTeAg coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 58Ag 42, and other is identical with sample 1, and a memory element is made sample 4.
Measure the I-V characteristic of memory element in these samples 2 to 4.Fig. 2 B illustrates the measurement result of sample 2 and shows, Fig. 3 A illustrates the measurement result of sample 3, and Fig. 3 B illustrates the measurement result of sample 4.
Shown in Fig. 2 B, 3A, 3B, when voltage increased corresponding to the increase of the content of silver-colored Ag, threshold voltage vt h also uprised, and should be understood that after it surpasses threshold voltage vt h, the slope dI/dV of I-V, and promptly the changes in resistance rate becomes mild.
If the mechanism of resistance variations is, for example according to the motion of negative electrode side, form narrow current path in the electric field of the silver ion that in top electrode 5, comprises with low resistance and local high silver concentration, can think, by add silver in GeSbTe, the voltage that forms current path raises a little and the formation speed of current path is slack-off or the disperse that forms the voltage of many current paths uprises.
Equally, for Fig. 3 A and 3B, i.e. sample 3 and sample 4, be set at flow restricter under the situation of 0.5mA, resistance also recovers when voltage turns back to 0V, and causes the record can not maintained result, thereby the value that has shown flow restricter is set at the result of 1mA and the result of measurement.
In addition, though the resistance change rate before and after the record is 400 times in the sample 1 of Fig. 2 A, respectively, be 80 times in the sample 2 of Fig. 2 B, be 7 times in the sample 3 of Fig. 3 A and the sample 4 of Fig. 3 B.
In other words, though have relatively low resistance when each sample when record the time applies greater than threshold voltage according, should be understood that the reason that the changes in resistance rate is reduced is that the decline of the voltage that applies of basis makes the increment rate of resistance become big once more.
Especially, the opening that maintenance is recorded when the content of supposition silver increases becomes difficult.
For The above results, make the increase that causes recording voltage and record current that comprises silver in advance of the GeSbTe of noncrystalline film 4, and by like this, the problem of the disperse of meeting occurrence record voltage or the decline of writing speed, and found the problem that resistance change speed descends, the i.e. decline of signal level when beginning to read, and recorded preservation characteristics variation.
Therefore, wish that memory element 10 is manufactured noncrystalline film 4 does not comprise silver or copper, and silver that comprises in the top electrode 5 or copper.
＜experiment 3 〉
Next, change noncrystalline film 4 the GeSbTe coating Ge content and its characteristic studied.
At first, formation thickness is that the titanium coating of 100nm replaces the TiW coating as bottom electrode 2 and electrode layer 6, and other is identical with sample 1, and a memory element 10 is made sample 5.
Next, form a GeSbTe coating as noncrystalline film 4, it consists of Ge 31Sb 19Te 50(numeral of being added is an atomic weight percentage, and is hereinafter identical therewith), and other is identical with sample 1, and a memory element 10 is made sample 6.
Next, form a GeSbTe coating as noncrystalline film 4, it consists of Ge 38Sb 17Te 45, and other is identical with sample 1, and a memory element 10 is made sample 7.
Next, form a GeSbTe coating as noncrystalline film 4, it consists of Ge 49Sb 17Te 37, and other is identical with sample 1, and a memory element 10 is made sample 8.
Measure the I-V characteristic of memory element in these samples 5 to 8.Fig. 4 A illustrates the measurement result of sample 5 and shows, Fig. 4 B illustrates the measurement result of sample 6, and Fig. 5 A illustrates the measurement result of sample 7, and Fig. 5 B illustrates the measurement result of sample 8.
Shown in Fig. 4 A and 5B, can determine the preservation that in these wide germanium composition ranges, can suitably write down and write down.
And, should be understood that if the content of germanium increases that by Fig. 5 A and 5B when the voltage that applies above threshold value, it is mild that described dI/dV becomes.When Ge content increased, memory element had the advantage of the stability increase of heat resistanceheat resistant, though with regard to memory characteristics, Ge content small records more will be easy more.Therefore, the content of germanium should characteristic as requested be controlled.
＜experiment 4 〉
Next, change the material of bottom electrode 2 and electrode layer 6, and its characteristic is studied.
The formation coating layer thickness is that the tungsten coating of 100nm replaces the TiW coating as bottom electrode 2 and electrode layer 6, and other is identical with sample 1, and a memory element 10 is made sample 9.
The I-V characteristic of memory element in the measuring samples 9.Measurement result has been shown among Fig. 6.
According to Fig. 6, should be understood that to obtain the good I-V characteristic identical with other figure, and can easily carry out record with Fig. 2 A.
In addition, when respectively described bottom electrode 2 and electrode layer 6 being become composition right and wrong Ti 50W 50The laminated coating of laminated coating, TiW/W of laminated coating, TiW/Ti of TiW coating, Ti/TiW and make described sample during the laminated coating of W/TiW and when measuring, the good I-V characteristic that acquisition is identical with Fig. 1 and other figure.
In addition, when described conductor layer 7 is changed to the copper coating and the perparation of specimen and when measuring in the same manner, obtain the good I-V characteristic identical with Fig. 1.
＜experiment 5 〉
Next, replace the top electrode 5 of GeSbTeAg coating, and its characteristic is studied as argentiferous with silver coating.
The formation coating layer thickness is that the silver coating of 6nm replaces the GeSbTeAg coating as top electrode 5, and other is identical with sample 1, and a memory element is made sample 10.
The I-V characteristic of the memory element of measuring samples 10 has illustrated measurement result among Fig. 7.
In Fig. 7, identical with Fig. 2 A with other figure, should be understood that to have obtained good I-V characteristic and can easily carry out record.DI/dV when especially, should be understood that record is very precipitous with comparing of Fig. 2 A.
Then, when the result who considers Fig. 7 and Fig. 2 A to 3B as a result the time, the dI/dV that should be understood that when record is along with the difference between the concentration of copper that comprises in the concentration of silver that comprises in the top electrode 5 or copper and the noncrystalline film 4 or silver becomes big more and precipitous more, and can obtain the good record characteristic.
It should be noted that when the coating layer thickness that changes silver coating and make a sample and when similarly measuring,, obtain similar I-V characteristic if coating layer thickness is equal to or greater than 3nm.
＜experiment 6 〉
In noncrystalline film 4, add and be different from the silver that becomes ionic medium or the doping metals of copper, study particularly as the gadolinium (Gd) of rare earth metal, and to its characteristic.
At first, form the GeSbTeGd coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 89Gd 11(numeral of being added is an atomic weight percentage, and is hereinafter identical therewith), and other is identical with sample 1, and a memory element is made sample 11.
Next, form the GeSbTeGd coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 82Gd 18, and other is all identical with sample 1, and a memory element is made sample 12.
Measure the I-V characteristic of each memory element of these samples 11 and 12.Fig. 8 A illustrates the measurement result of sample 11, and Fig. 8 B illustrates the measurement result of sample 12.
In this case, shown in Fig. 8 A and Fig. 8 B, also can determine the preservation that suitably to write down and to write down.
In addition, resistance value before the record raises and becomes greater than 1M Ω, after this it is kept at high temperature, obtain the effect of stable electrical resistance by adding rare-earth element gadolinium, and do not change substantially through the sample that has gadolinium 11 of 270 degrees centigrade of next hours annealing and the resistance value sample of sample 12.
In other words, determine that crystallization temperature rises, and by adding the stability of rare earth element maintenance non-crystalline state.
And owing to increase threshold voltage by for example adding rare earth element, the voltage when setting reproduction (reading) is that Gao Shihui is more effective.
Because rare earth element has identical external electrical structure and has equal characteristic electron and irrelevant with its kind, so be not restricted to the use of gadolinium, and when using element lanthanum, cerium, praseodymium, neodymium, samarium, europium, terbium, dysprosium, holmium and erbium, same effect is expected.
＜experiment 7 〉
In noncrystalline film 4, add particularly silicon of doped chemical, and its characteristic is studied.
At first, form the GeSbTeSi coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 93Si 7(numeral of being added is an atomic weight percentage, and is hereinafter identical therewith), and other is identical with sample 1, and a memory element is made sample 13.
Next, form the GeSbTeSi coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 85Si 15, and other is identical with sample 1, and a memory element is made sample 14.
Next, form the GeSbTeSi coating as noncrystalline film 4, it consists of (Ge 22Sb 22Te 56) 77Si 23, and other is identical with sample 1, and a memory element is made sample 15.
Measure the I-V characteristic of each memory element of these samples 13 to 15.Fig. 9 A illustrates the measurement result of sample 13, and Fig. 9 B illustrates the measurement result of sample 14, and Fig. 9 C illustrates the measurement result of sample 15.
In Fig. 9 A and 9B, roughly less than 15% atomic weight, described I-V characteristic not have to change substantially, and the definite maintenance that can suitably write down and write down up to the silicon that adds.
On the contrary, shown in Fig. 9 C, when the silicon adding was set to 23% atomic weight, threshold voltage increased, and therefore record becomes very difficult under 0.5mA, and the electric current that needs is roughly 1mA.
It should be noted that by in the GeSbTe of noncrystalline film 4, adding silicon and can expect the increase thermal stability.This is because the covalent bond energy of Si-Si is higher, the fusing point of silicon matter is higher, and along with the increase fusing point of silicone content in the Si-Ge alloy cpd also rises, when silicon is added into GeSbTe, covalent bond rises in an identical manner, therefore can expect by adding silicon fusing point and crystallization temperature to be raise.
＜experiment 8 〉
Change the coating layer thickness of noncrystalline film 4, and its characteristic is studied.
At first, bottom electrode 2 is for to paint the titanium coating that thickness is 20nm, and the coating layer thickness of the GeSbTe coating of noncrystalline film 4 is 14nm, and other is identical with sample 1, and a memory element is made sample 16.
Next, the coating layer thickness of the GeSbTe coating of noncrystalline film 4 is 25nm, and other is identical with sample 16, and a memory element is made sample 17.
In addition, in sample 17, the coating layer thickness of the GeSbTe coating of noncrystalline film 4 is identical with thickness in the sample 1.
Next, the coating layer thickness of the GeSbTe coating of noncrystalline film 4 is 38nm, and other is identical with sample 16, and a memory element is made sample 18.
Next, the coating layer thickness of the GeSbTe coating of noncrystalline film 4 is 51nm, and other is identical with sample 16, and a memory element is made sample 19.
Measure the I-V characteristic of each memory element of these samples 16 to 19.Figure 10 A illustrates the measurement result of sample 16, and Figure 10 B illustrates the measurement result of sample 17, and Figure 11 A illustrates the measurement result of sample 18, and Figure 11 B illustrates the measurement result of sample 19.
Can determine, in the thickness range of these coatings, as Figure 10 A to the maintenance that can suitably write down and write down shown in the 11B.
It should be noted that, be roughly 0.1V though the threshold voltage in the thinnest sample 16 of coating layer thickness (Figure 10 A) is low to moderate, in other the sample, threshold voltage variation is little at all, and it doesn't matter with coating layer thickness, and all other threshold voltage is roughly 0.17V.
In addition, in the memory element 10 in the above-described embodiments, the high conductivity silicon substrate with high-dopant concentration is used for substrate 1 and applies earth potential (ground potential) to the rear side of substrate 1; But the structure that applies voltage to the bottom electrode side is not limited thereto, and also can be other structure.
For example, can use on substrate surface, form and with the electrode of silicon substrate electric insulation.
In addition, by the Semiconductor substrate of non-silicon materials manufacturing, or dielectric substrate, for example also can be used as substrate by the substrate that glass and plastics are formed.
Next, the memory element of another embodiment of the present invention is described.
In this embodiment, same as the previously described embodiments, constitute cross section structure memory element 10 as shown in Figure 1.
Then, in this embodiment, noncrystalline film is made up of the oxide of transition metal or germanium and silicon, and this oxide is the oxide from having dystectic titanium, vanadium, iron, cobalt, yttrium, zirconium, niobium, molybdenum, hafnium, tantalum and having at least a element of selecting the tungsten of especially high fusing point.
It should be noted that noncrystalline film can comprise a plurality of elements and germanium and the silicon in the above-mentioned transition metal, perhaps can comprise the element outside these elements.
For example be used under the situation of noncrystalline film 4 in the tungsten oxide coating, described coating layer thickness for example should be set to 5nm to the scope of 50nm, and under the situation of using the germanium oxide coating, and described coating layer thickness for example should be set at 3nm to the scope of 40nm.
Constitute the top electrode 5 that comprises silver or copper.
Can use coating, silver coating, silver alloy coating, copper coating, copper alloy coating etc. that for example silver or copper are added the composition of noncrystalline film 4 compositions to constitute top electrode 5.
For example using under the situation of silver oxide coating as noncrystalline film 4, coating layer thickness for example should be set at 10nm to the scope of 30nm, and is using under the silver-colored situation, and coating layer thickness for example should be set at 3nm to the 20nm scope.
The electrode layer 6 of the utmost point 5 of Connecting Power uses the material that does not comprise silver or copper, and silver or copper-clad are contained in the top electrode 5.
In addition, the material that comprises silver or copper when bottom electrode 2 is similar to described top electrode also can be used for electrode layer.
Because identical with the memory element of the foregoing description, the explanation of other composition is omitted, and omits too much explanation.
Operation to the memory element 10 of present embodiment is as follows, and can store information.
At first, apply positive potential (+electromotive force), and positive voltage is applied to memory element 10, thereby top electrode 5 sides become positive to the top electrode 5 that comprises silver or copper.Like this, the utmost point 5 silver medals or copper become ionization from power on, and diffuse in the noncrystalline film 4 and combine and separated out with electronics in bottom electrode 2 sides.
Then, form the current path that comprises a large amount of silver or copper in noncrystalline film 4 inside, and the resistance step-down in the noncrystalline film 4.Because the resistance of each layer outside the noncrystalline film 4 of beginning is very low, can reduce the resistance of whole memory element 10 by the resistance that reduces noncrystalline film 4.
Subsequently, when removing positive voltage and stoping memory element 10 to have voltage, memory element 10 is maintained at the state that this resistance becomes very low.Therefore, information can be recorded.
On the other hand, during the information that writes down when wiping, on the top electrode 5 that comprises silver or copper, apply negative potential (electromotive force) and on memory element 10, apply negative voltage that to make that the top electrode side becomes negative.Like this, thus silver or the copper formed at the noncrystalline film 4 inner current paths that form become ion and enter the noncrystalline film 4 inner initial conditions that turn back in top electrode 5 sides.
Then, the current path that is made of silver or copper disappears in noncrystalline film 4 inside, and the resistance at this place uprises.Because it is lower to begin the resistance of each layer outside the noncrystalline film 4, uprises by the resistance that makes noncrystalline film 4 overall electrical resistance of memory element 10 is uprised.
Subsequently, when removing negative voltage and stop memory element 10 to have voltage, the state that resistance uprises is held.Like this, become and to wipe the information that is write down.
By repeating such process, on memory element 10, can carry out wiping of recording of information (writing) and institute's recorded information repeatedly.
Then, for example when overall electrical resistance be that high state is corresponding to information " 0 ", and overall electrical resistance is that low state is during corresponding to information " 1 ", in the information recording process, can change to " 1 " by applying positive voltage, and can in the erase process of information, can change to " 0 " by applying negative voltage from " 1 " from " 0 ".
It should be noted that in above-mentioned recording of information process and erase process noncrystalline film remains on noncrystalline (no crystallization) state and never produce the phase transformation of crystallization.
In other words, under the voltage conditions that never causes noncrystalline film 4 generation phase transformations, carry out recording of information and wipe.
In addition, as described above, noncrystalline film 4 must be to have high-resistance material in the initial condition before the record with under the state after wiping.
Compare with the material of forming noncrystalline film 4 with the cell size of memory element, resistance value behind the record more depends on the record condition such as recording impulse width and the electric current when writing down, and when initial resistance is 100k Ω or when higher, the resistance that record changes almost becomes the scope of 50 Ω to 50k Ω.
In order to reappear the data of record, the ratio of the resistance value behind initial resistivity value and the record is roughly twice or more the higher position is enough, thereby when the resistance value before record is 100 Ω and is that 50 Ω or the resistance value before record are that 100k Ω and the resistance value behind record are that 50k Ω is just enough in the resistance value behind the record, and the initial resistivity value of noncrystalline film 4 is set to and satisfies such condition.
The setting of resistance value can be by the area of for example oxygen concentration, coating layer thickness and memory element and is further adjusted by adding dopant material.
Memory element 10 according to the foregoing description, because noncrystalline film 4 comprises above-mentioned oxide (transition metal oxide particularly, hope is germanium oxide and silica), can be by making silver or copper with the ionic species utmost point 5 diffusion from power on and move in the crystalline membrane 4 to come information is stored.
Then, because use the variation of the resistance value of memory element 10 to carry out recording of information, when memory element 10 is made very smallly, can easily carry out the preservation of recording of information and institute's recorded information.
And according to the memory element 10 of the foregoing description, each bottom electrode 2, noncrystalline film 4, top electrode 5, electrode layer 6 and conductor layer 7 can be made of the material that can carry out sputter.Have the target of suitable layers of material composition by use, can carry out described sputter.
And, form described coating serially by in same sputtering unit, changing target.
Also have, use the method for oxide sputter target and use metallic target and import oxygen and when sputter, can be used for forming the sputter coating of oxide as the method such as the inert gas of argon of the guiding gas (introduction gas) that imports gas, so-called reaction method for sputtering etc.In addition, can form coating by deposition process as CVD method or non-sputter.
Equally, for example, can make the memory element 10 of the foregoing description as follows.
At first, has the substrate of high conductivity, for example with accumulation bottom electrode 2, for example TiW coating on the silicon substrate of high-concentration dopant P type alloy.
Next, form insulation film 3, after this, form opening in the insulation film 3 on bottom electrode 2 to cover bottom electrode 2.
Then, etching bottom electrode 2 lip-deep oxidized surfaces, and remove thin oxide coating, obtain the good conductive surface.
Subsequently, make noncrystalline film 4, for example tungsten oxide coating by for example magnetron sputter reactor device.
Next, make top electrode 5, for example comprise the tungsten oxide coating or the silver coating of silver by for example magnetron sputter reactor device.
Then, for example make electrode layer 6, TiW coating for example, and further make conductor layer 7, for example AlSi coating or copper coating by the magnetron sputter reactor device.
Subsequently, for example these noncrystalline films 4, top electrode 5, electrode layer 6 and conductor layer 7 are constituted pattern by plasma etching or other method.Can constitute pattern by engraving method equally as ion grinding and RIE non-plasma etchings such as (reactive ion etchings).
As mentioned above, can make as shown in Figure 1 memory element 10.
It should be noted that, in the memory element 10 of the foregoing description, be not included in the bottom electrode 2 though silver or copper-clad are contained in the top electrode 5, can use silver or copper only to be included in the structure of bottom electrode and silver or copper yet and be included in structure in bottom electrode and the top electrode simultaneously.
Can constitute storage device (memory storage) with rectangular layout by memory element with a large amount of the foregoing descriptions.
For example, for each memory element 10 is provided with the wiring that connects bottom electrode 2 sides and the wiring of the utmost point 5 sides that Connect Power, and each memory element 10 be disposed in these wirings the crosspoint around.
Then, especially, for example on column direction, form bottom electrode 2 with respect to storage element publicly; On line direction, form the wiring that is connected to conductor layer 7 with respect to the storage element public land; By selecting to apply the bottom electrode 2 and the wiring of electromotive force thereon, select the storage element that is recorded; And the electric current of the memory element 10 by flowing into this storage element carries out wiping of information record and institute's recorded information.
For the memory element 10 of the foregoing description, can easily carry out recorded information and read the information that is write down, and described especially memory element is under hot environment and have superperformance aspect the long preservation data stability.
And, for the memory element 10 of the foregoing description,, can obtain integrated (towards high density) and the miniaturization of storage device because the preservation of recording of information and institute's recorded information is easy to when memory element is miniaturized.
[actual example]
Next, the actual memory element 10 of making the foregoing description.And its characteristic is studied.
＜experiment 9 〉
At first, at substrate 1, for example being that the TiW coating of 100nm is as bottom electrode 2 by sputter accumulation coating layer thickness on the silicon substrate of high-concentration dopant P type alloy with high conductivity.
Next, cover bottom electrode 2, and form photoresist, after this,, expose and develop and on the photoresist on the bottom electrode 2, form opening (through hole) by lithoprinting.Described opening (through hole) is of a size of 2 μ m * 2 μ m.
Then, in vacuum state, anneal under 270 degrees centigrade, and photoresist is changed, and form the stable sclerosis protective layer of dielectric film 3 as resistance temperature, resistance etching etc.It should be noted that described sclerosis protective layer as dielectric film 3, because the formation easily for experiment of this protective layer, and therefore when making this product, also can consider to use the situation of other material (silica coating etc.) as insulation film 3.
Then, react method for sputtering by using the magnetron sputter reactor device to introduce oxygen, the tungsten oxide coating that forms coating layer thickness and be 20nm is as noncrystalline film 4.The tungsten oxide coating composition is W xO 100-x(x that is added and numeral are atomic weight percentage), and x is roughly 24.
In addition, form the tungsten oxide coating of coating layer thickness 20nm as top electrode 5 by the magnetron sputter reactor device that remains under the identical vacuum state.Silver concentration in this tungsten oxide coating is roughly 50%.
In addition, to form coating layer thickness be that the TiW coating of 100nm is as electrode layer 6 by remaining on magnetron sputter reactor device under the identical vacuum state.And the AlSi coating that forms coating layer thickness then and be 100nm is as conductor layer 7.The composition of TiW coating and AlSi coating is respectively Ti 50W 50And aluminium 97Silicon 3(numeral of being added is an atomic weight percentage).
Subsequently, by the lithoprinting of using plasma etching apparatus noncrystalline film 4, top electrode 5, electrode layer 6 and the conductor layer 7 of accumulation on the dielectric film 3 that is made of the sclerosis protective layer carried out the composition of 50 μ m * 50 μ m sizes.
As mentioned above, make the memory element 10 of structure as shown in Figure 1, with sample 20 as memory element 10.
For this sample 20 of described memory element 10, apply positive potential (+electromotive force) to the conductor layer 7 of top electrode 5 sides, and the rear side of substrate 1 connects earth potential (ground potential).
Then, begin to increase the positive potential that applies to conductor layer 7, and measure the variation of electric current from 0V.But flow restricter is set to when described electric current arrives 0.5mA and starts working, thereby its setting is applied to the positive potential on the conductor layer 7, and the positive voltage that promptly is applied on the memory element 10 can not further increase.
In addition, after electric current arrives 0.5mA, be applied to the state that the positive potential on the conductor layer 7 starts working from described flow restricter and be reduced to 0V, and measure the variation of electric current.
The I-V characteristic curve that obtains shown in Figure 12 A.
In Figure 12 A, should be understood that: the very high and memory element of resistance 10 is closed condition under the initial condition, and electric current surpasses threshold voltage vt h along with voltage increases and increase sharply, thereby in other words the resistance step-down changes opening into.Therefore, should be understood that information is recorded.
On the other hand, after this, by reducing voltage, electric current also descends, and resistance little by little raises though the amount that electric current descends is big, and last resistance value becomes and is enough to be lower than described initial resistivity value, and is held open state, should be understood that the information that is write down is held.
Under the situation of this sample 20, descend the resistance value of voltage V=0.1V to be roughly 500k Ω and under opening, to be roughly 500 Ω in off position.
In addition,, apply the voltage V of opposite polarity to the conductor layer 7 of top electrode 5 sides as shown in the figure, i.e. negative potential (electromotive force), and make the rear side of substrate 1 connect earth potential (ground potential), and apply negative voltage smaller or equal to V=-0.4V to conductor layer 7; After this, when the electromotive force with conductor layer 7 is set at 0V, can determine that resistance turns back to high resistance initial condition in the closed condition.In other words, should be understood that can be by applying the information erasing that negative potential will be write down in memory element 10.
＜experiment 10 〉
The characteristic of research under the situation that noncrystalline film 4 is made up of germanium oxide.
At first, identical with the tungsten oxide coating, form Ge by the reaction method for sputtering xO 100-xCoating is as noncrystalline film 4.Immediately, the germanium oxide coating layer thickness is 5nm and accumulates the silver of 6nm and form top electrode on this coating.Other is identical with sample 20 and make a memory element.
By said method, in the reaction sputter, change the amount of oxygen that imports, and produce sample 21 to 23.
The germanium and the oxygen concentration that obtain are as follows:
[concentration (atomic weight percentage)]
Sample number into spectrum germanium oxygen
Sample 21 50.5 49.5
Sample 22 44.1 58.9
Sample 23 32.7 67.3
Measure the I-V characteristic of the memory element of each sample 21 to 23.Figure 13 A illustrates the measurement result of sample 21, and Figure 13 B illustrates the measurement result of sample 22, and Figure 13 C illustrates the measurement result of sample 23.
To shown in the 13C, the initial resistance in sample 21 is 300k Ω as Figure 13 A, and the initial resistance in the sample 22 is 500k Ω, and the initial resistance in the sample 23 is 500k Ω, and is all very high.
Then, when voltage became big on positive direction, described electric current began promptly to flow under particular threshold voltage Vth, and it promptly reaches the electric current of flow restricter set point 0.5mA.
Then, when voltage is reduced to about 0V, be appreciated that the resistance ratio initial resistivity value is low.
In addition, all samples has the roughly resistance of 500 Ω, is appreciated that at when record resistance value three orders of magnitude that roughly descend.
On the other hand, when voltage reduces on negative direction, the electric current of each sample roughly-reduction of 0.2V place, and resistance value changes.
When further reduction voltage, there is a sample (sample 21), the immobilising state of its holding current, and have some samples (sample 22 and 23), its magnitude of current is at the dividing value-0.5mA that rapidly increases to flow restricter smaller or equal to the particular threshold voltage place; But when voltage returned 0V once more, each sample was a high resistance state from this state-transition.
Then, the initial resistivity value before sample 21 return recordings, sample 22 and 23 becomes and is roughly 10k Ω.
But, when voltage max on negative direction is controlled as smaller or equal to threshold value, sample 22 with 23 with sample 21 the same return recordings before initial resistivity value.
As mentioned above, by applying the voltage of opposite polarity, in other words the state before the described resistance value return recording, can carry out erase operation.
＜experiment 11 〉
The characteristic of research under the situation that noncrystalline film 4 is made up of silica.
At first, identical with the tungsten oxide coating with the germanium oxide coating, form Si by the reaction method for sputtering xO 100-xAs noncrystalline film 4.
The composition x of silicon roughly equates with the composition of silicon dioxide, and x=33.
Then, forming coating layer thickness is the sample (sample 24) of the silica coating of 3nm and the silica coating sample (sample 25) that coating layer thickness is 6nm.
Next, for each sample, film that the 6nm of accumulation silicon dioxide and silver compound is thick on silica coating and formation top electrode.And, the compound of this silicon dioxide and silver be silver-colored and silicon dioxide with the involved structure of roughly the same ratio.
Other is identical with sample 20, and makes a memory element.
Measure the I-V characteristic of the memory element of two kinds of samples (sample 24 and 25) with different silica coating thickness.Figure 14 A illustrates the measurement result of sample 24, and Figure 14 B illustrates the measurement result of sample 25.
In Figure 14 A and 14B, both resistance is that height arrives more than or equal to 1M Ω under initial condition, and when voltage increased on negative direction, under particular threshold voltage Vth, electric current began to flow rapidly, and arrived the electric current of the 0.5mA of limiter setting rapidly.
Subsequently, when voltage being reduced to when being approximately 0V, the resistance of comparing with initial resistivity value reduces and becomes approximate 1k Ω.
In other words, be to be understood that resistance value has roughly reduced by three orders of magnitude by record.
When voltage further increased on positive direction, the electric current of each sample descended, and resistance value becomes high state once more.
As mentioned above, by apply the voltage of opposite polarity for record, in other words the state before the resistance value return recording, can carry out erase operation.
It should be noted that in the memory element 10 of the foregoing description the silicon substrate with high conductivity of highly doped substrate concentration applies earth potential (ground potential) as substrate 1 and to substrate 1 rear side; But, also can use other structure to apply voltage to the bottom electrode side.
For example, also can use be formed at substrate surface and with the electrode of silicon substrate electric insulation.
In addition, also can use silicon substrate Semiconductor substrate in addition, or dielectric substrate, for example substrate that forms by glass or resin.
In addition, the tungsten oxide of the oxide that in above-mentioned experiment, uses, its fusing point is 1400 degrees centigrade or the higher (value under Ji Zai the crystalline state in the literature, below identical), the fusing point of germanium oxide coating is 1000 degrees centigrade or higher, the fusing point of silica coating is 1700 degrees centigrade or higher, so these are that heat stable material and crystallization temperature are very high.
In addition, record mechanism is the ionic conduction of being undertaken by the electric field that applies silver or copper, therefore state in the use under the transition metal oxide situation outside the tungsten that uses in the experiment, as long as the electronic structure of the external electrical structure of transition metal oxide and tungsten is similar, just can carry out storage operation like that by similar tungsten.
In the middle of transition metal, be dystectic viewpoint from oxide, the oxide of titanium, vanadium, iron, cobalt, yttrium, zirconium, niobium, molybdenum, hafnium and tantalum is suitable, and makes sull easily.
Use memory element of the present invention, can be by arranging that a large amount of memory elements are for example row shape or rectangular formation storage device (memory storage).
In addition, if desired, be used to select the MOS transistor of element or diode to be connected, and constitute memory cell with each memory element.
And, by described memory element is wired to sensor amplifier, the addressing register, write down, wipe with reading circuit and other on.
Memory element of the present invention can be applied on the various memory storages.Described memory element can be applied to various file layouts, and for example so-called PROM (programmable ROM) wherein only can carry out write-once; EEPROM (electrically-erasable ROM (EEROM)).Wherein can carry out electricity wipes; Or so-called RAM (random access memory), wherein can carry out high-speed record, wipe and reproduce; And in other type.
The invention is not restricted to the foregoing description, and in main points of the present invention, can obtain various other structures.

Claims (9)

1. memory element comprises:
Noncrystalline film, it is between first electrode and second electrode, wherein
At least one electrode package argentiferous or copper in described first and second electrodes, and
At least a element that described noncrystalline film is selected by germanium with from sulphur, selenium, tellurium and antimony is formed.
2. memory element according to claim 1, the electrode that wherein comprises silver or copper is connected with an electrode layer, and this electrode layer comprises a kind of element, and the chemical valence of this element is greater than being included in the silver in the described electrode or the chemical valence of copper when ionization.
3. memory element according to claim 1, wherein said first electrode or second electrode are connected to an electrode layer, and this electrode layer is made of one of TiW, titanium and tungsten.
4. memory element according to claim 1, wherein said noncrystalline film is made up of germanium and at least a element and the silicon selected from sulphur, selenium, tellurium and antimony.
5. storage device comprises:
Memory element, this memory element comprises: noncrystalline film, its between first electrode and second electrode, at least one electrode package argentiferous or copper in wherein said first and second electrodes, and at least a element that described noncrystalline film is selected by germanium with from sulphur, selenium, tellurium and antimony is formed;
Be connected to the wiring of the described first electrode side; With
Be connected to the wiring of the described second electrode side; Wherein
Described memory element is arranged in a large number.
6. storage unit comprises:
Noncrystalline film, it is between first electrode and second electrode, wherein
One or whole electrode package argentiferous or copper in described first and second electrodes, and
Described noncrystalline film is made up of oxide.
7. as storage unit as described in the claim 6, wherein said oxide comprises any one in transition metal oxide, germanium oxide and the silica.
8. storage device comprises:
Memory element, this memory element comprises: noncrystalline film, its between first electrode and second electrode, at least one electrode package argentiferous or copper in wherein said first and second electrodes, and described noncrystalline film is made up of oxide;
Be connected to the wiring of the described first electrode side; With
Be connected to the wiring of the described second electrode side; Wherein
Described memory element is arranged in a large number.
9. as storage device as described in the claim 8, wherein said oxide comprises any one in transition metal oxide, germanium oxide and the silica.
CNB200480000388XA 2003-03-20 2004-03-18 Memory element and storage device using this Expired - Fee Related CN100378998C (en)

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