CN101109056B - Aluminum-doping phase transiting storing thin-film material Alx(Ge2Sb2Te5)100-x and method of preparing the same - Google Patents

Abstract

The invention belongs to the phase transformation memory material technology field, in particular to an aluminum-doped phase transformation memory film material Alx (Ge2Sb2Te5)100 minus x and the preparation method thereof. The invention prepares the aluminum-doped phase transformation memory film Alx (Ge2Sb2Te5)100 minus x by ultilizing a magnetron sputtering coating system and a co-sputtering mode. Compared with the Ge2Sb2Te5 film without doping, the microstructure and the physical property of the film are changed. The research result shows that the phase transformation temperature of the sample is increased as the increase of the aluminum-doped and the FCC of the sample is stable, which is helpful to change the application condition and the service life of the phase transformation disc; meanwhile, the doping in aluminum is quite good for the strength of the reflection contrast gradient of the Ge2Sb2Te5 film and is capable of change the signal-to-noise ratio of the phase transformation optical memory read-out signal.

Description

Aluminum-doping phase transiting storing thin-film material Al x(Ge 2Sb 2Te 5) 100-xAnd preparation method thereof

Technical field

The invention belongs to the phase-change storage material technical field, be specifically related to a kind of aluminum-doping phase transiting storing thin-film material Al _x(Ge ₂Sb ₂Te ₅) _100-xAnd preparation method thereof.

Background technology

Nineteen sixty-eight, Ovshinsky has proposed the notion of phase change memory (Phase-Change Memory (PCM)), and he has found in the chalkogenide thin-film material that atom is arranged and can change between the order-disorder attitude.Phase change memory is also referred to as Ovonic Unified Memory (OUM), is a kind of technology of changing canned data based on the crystalline state and the non-crystalline state biphase of chalcogenide material.When being in crystalline state and non-crystalline state, the optical property of film and electrical properties have very big difference, mainly show in the variation of reflectivity and resistivity.Reversible transition between crystalline state and the non-crystalline state can be realized by heat effect.

1971, people such as Ovshinsky reported that Te base alloy is used for wiping the possibility of phase transformation optical storage, and from then on investigators have just begun the research to the phase transformation optical memory material.

Along with going deep into of research, investigators have found a collection of phase change material with reversible optical storage performance, mainly are some semiconductor materials, as Te base, Se base and In-Sb base alloy etc.Wherein become the most rising reversible transformation optical memory material of a class with Te base alloy especially.Binary Te base alloy mainly contains Te-Ge, Te-Sn, Sb-Te, Te-Ox etc.; Ternary Te base alloy mainly is the Ge-Sb-Te ternary alloy.Se base alloy mainly is Sb ₂Se ₃Binary alloy and Sb-Se-Bi ternary alloy.In the In-Sb base alloy mainly is the In-Ag-Sb-Te quad alloy.What research was maximum at present is Ge-Sb-Te ternary alloy and In-Ag-Sb-Te quad alloy.

In the Ge-Sb-Te alloy, as the compound that meets stoichiometric ratio that is generally of recording film, as Ge ₁Sb ₂Te ₄, Ge ₂Sb ₂Te ₅, Ge ₁Sb ₄Te ₇, on phasor, all be positioned at GeTe and Sb ₂Te ₃Line on.Ge ₁Sb ₂Te ₄By GeTe and Sb ₂Te ₃Form, and Ge ₂Sb ₂Te ₅By two parts of GeTe and Sb ₂Te ₃Form.The Ge-Sb-Te phase conversion mechanism is conversion between amorphous phase and the FCC metastable phase.Increase Sb ₂Te ₃Content can improve crystallization rate.The nucleation time of Ge-Sb-Te material shows that less than the crystal growth time its crystallization is determined by nucleation process rather than growth process.The outstanding advantage of this material be write, wiping speed is all very fast, can be used for phase change disc and directly rewrite at a high speed, and significantly improve the message transmission rate of phase change disc, is research and use maximum in the current phase transformation optical memory material.

As the direct carrier of information, the performance of material is the problem of most critical in the memory technology.The development of memory technology depends on the research and development to the storage medium of excellent property.Towards high-density, high transfer rate and high stability development, this has proposed more and more higher requirement to storage medium to memory technology always.Based on the superior phase-change characteristic of Ge-Sb-Te based material, existing so far Many researchers was done many correlative studys to the optical property (uptake factor, reflectivity etc.) of this class material.Because the composition and the structure of film have directly determined its optical property, therefore to focusing on that the Ge-Sb-Te based material is studied by different elements or the change preparation condition of mixing, adjust film composition and structure, research and analyse its phase transformation and optical characteristics, in the hope of obtaining to satisfy the phase change memory medium of requirements at the higher level.Domestic and international many discovering, some elements that mix in right amount (as mixing N, O, Sn etc.) have not only increased reflectivity contrast, can improve the film crystallization temperature simultaneously, and signal to noise ratio (snr) and erasable performance are significantly improved, and have greatly improved the material memory property.

When having at least 10 ²During the particle of eV kinetic energy/particle beam bombardment solid material surface, can obtain the portion of energy of projectile and break away from solid and enter into vacuum near the atom/atomic group of solid surface, this phenomenon is called as sputter.In fact sputter coating is exactly the interaction by projectile and the nearly top layer of solid material atom, obtains energy less than electroneutral atom of 20eV or molecule, and having only seldom a part of product (0.02%-10%) is ion, all is called as the sputter product.The ultimate principle of magnetron sputtering is to utilize magnetic field to change the electronic motion direction, electronic motion is limited near the negative electrode, constraint and prolongation electronic motion track, thereby improve the specific ionization of electronics and working gas, effectively utilize electron energy, make the caused sputter of ion bombardment target more effective.Sputtering method (comprising DC direct current mode and RF RF-wise) is a class most important method of the various films of preparation, height C axle orientation, surface finish height, higher transmittance and good electricity, the film of optical property can be obtained, and industrialization big area high speed deposition can be realized.Nearly all domestic and international investigator and industry all adopt sputtering method to prepare Ge ₂Sb ₂Te ₅Thin-film material.

Summary of the invention

The objective of the invention is to propose the good aluminum-doping phase transiting storing thin-film material Al of a kind of phase change memory performance _x(Ge ₂Sb ₂Te ₅) _100-xAnd preparation method thereof.

The aluminum-doping phase transiting storing thin-film material that the present invention proposes, its chemical structural formula is: Al _x(Ge ₂Sb ₂Te ₅) _100-x, utilize magnetron sputtering coating system, adopt the double target co-sputtering method to prepare.Wherein, 0＜x≤5.

Al _x(Ge ₂Sb ₂Te ₅) _100-xThe Ge of phase change memory film and undoped ₂Sb ₂Te ₅Film is compared, and variation has all taken place for its microstructure and rerum natura, and test result shows that its phase change memory performance is improved.

The preparation method of above-mentioned aluminum-doping phase transiting storing thin-film material is as follows: use magnetron sputtering coating system, with metallic aluminium target and Ge ₂Sb ₂Te ₅Target is installed in respectively in magnetic control direct current (DC) sputtering target and magnetic control radio frequency (RF) sputtering target, and wherein the purity of target all is better than 99.99%.Substrate adopts Si (100) substrate, and the background vacuum pressure is 4.0 * 10 ^-6Mbar--6.0 * 10 ^-6Mbar, working gas are high-purity argon (more than 99.997%), and operating air pressure is 6.0 * 10 ^-3Mbar--8.0 * 10 ^-3Mbar, plated film under the room temperature, in the sputter procedure, the sputtering power of metal A l target is 15 ± 1w, Ge ₂Sb ₂Te ₅The sputtering power of target is 40-100w, and sputtering time is 300 seconds-500 seconds.And realize the phase transformation of film at each warm area by annealing.

In the film, the change of aluminium doping can realize by multiple usual manner, the target position height of for example regulating two sputtering targets and aligning direction or the different sputtering parameters (as sputtering power etc.) of the DC sputtering target that the metallic aluminium target is housed are set, or be provided with Ge is housed ₂Sb ₂Te ₅The different sputtering parameters of the RF sputtering target of target (as sputtering power etc.), or change working environment parameter in the chamber (as the flow change operating air pressure by the control working gas, coating temperature etc. is set) or the like.Be the stability of guaranteeing preparation condition, easy to control, the present invention is fixing on the basis of other contingent conditions, by changing wherein a kind of sputtering target (as Ge ₂Sb ₂Te ₅Target) sputtering power and the sputtering power of fixing another sputtering target (as metal A l target) is realized the effective control to aluminium doping in the film.Thereby obtain according to the required Al of design requirements (different doping) _x(Ge ₂Sb ₂Te ₅) _100-xThe aluminum-doping phase transiting film.For example, the sputtering power of fixing metal Al target is 15w, Ge ₂Sb ₂Te ₅The sputtering power of target is regulated in the 50-100w scope, can obtain different x values.

To Al by above method preparation _x(Ge ₂Sb ₂Te ₅) _100-xThe composition analysis of aluminum-doping phase transiting film, microstructure analysis and optical parametric test thereof are the UVISEL that utilizes x-ray photoelectron power spectrum (XPS), X-ray diffraction (XRD) and temperature controllable respectively ^TMType on-position measure elliptic polarization spectrometer is realized.

The X-ray photoelectron spectroscopic analysis method is to utilize the lower x-ray source of energy as excitaton source, with the sample surfaces atomic interaction after, the intratomic shell electron is excited ionization, by the electronics that analytic sample emits, realize a kind of surface analysis technique of analytic sample chemical ingredients with characteristic energy.Its analytical element wide ranges can be analyzed dehydrogenation all elements in addition in principle; Analysis depth is more shallow, greatly about the surface below 25～ Scope.Its absolute sensitivity is very high, is a kind of ultramicro-analysis technology.Therefore, adopt this technology to Al _x(Ge ₂Sb ₂Te ₅) _100-xThe composition of aluminum-doping phase transiting film is analyzed, and can obtain the aluminium doping in the film sample more exactly.

Structures shape character, the character reflect structure.The constitutional features of analysis of material and the preparation condition of material are the Basic Ways that obtains material character to the influence of structure.Utilize the Al of X-ray diffractometer experiments of measuring preparation _x(Ge ₂Sb ₂Te ₅) _100-xSample structure under aluminum-doping phase transiting film and the differing temps after the annealing, the diffraction angle sweep limit is from 10.0 ° to 60.0 °, and sweep velocity is 2 °/min, and step-length is 0.02 °.

Will be by the Al of design requirements preparation _x(Ge ₂Sb ₂Te ₅) _100-xThe aluminum-doping phase transiting film sample, the UVISEL of use temperature controllable ^TMType on-position measure ellipsometer carries out short annealing on the throne, carries out the measurement of optical constant simultaneously.Annealing region is from room temperature to 400 ℃, and temperature rise rate is set to 40-50 ℃/min, and temperature-controlled precision is ± 0.1 ℃.The opticmeasurement temperature interval is 10 ℃, each temperature spot annealing 5 minutes, and the optical constant of while on-position measure annealing specimen, the measure spectrum scope is 275.5～826.6nm.

Description of drawings:

Fig. 1 is two kinds of Al of preparation attitude _x(Ge ₂Sb ₂Te ₅) _100-xThe XRD figure spectrum of film sample.

Fig. 2 is through 200 ℃ of each Al of annealed _x(Ge ₂Sb ₂Te ₅) _100-xThe XRD figure spectrum of film sample.

Fig. 3 is through 400 ℃ of each Al of annealed _x(Ge ₂Sb ₂Te ₅) _100-xThe XRD figure spectrum of film sample.

Fig. 4 is each Al before and after the thermal treatment _x(Ge ₂Sb ₂Te ₅) _100-xThe optical extinction coefficient spectrum of film sample.Wherein, (a) be Al ₀(Ge ₂Sb ₂Te ₅) ₁₀₀, (b) be Al _1.43(Ge ₂Sb ₂Te ₅) _98.57, (c) be Al _1.67(Ge ₂Sb ₂Te ₅) _98.33, (d) be Al _3.19(Ge ₂Sb ₂Te ₅) _96.81.

Fig. 5 is 200 ℃ of each Al of annealed _x(Ge ₂Sb ₂Te ₅) _100-xThe reflection contrast curves of film sample.

Embodiment:

Use the LAB600sp magnetic control sputtering system, adopt metal A l target and Ge ₂Sb ₂Te ₅Target spatters mode altogether, at room temperature prepares Al on Si (100) substrate _x(Ge ₂Sb ₂Te ₅) _100-xThe aluminum-doping phase transiting film sample.In the experiment, the sputtering power of fixing metal Al target is 15W, Ge ₂Sb ₂Te ₅The sputtering power of target is respectively 50W, 75W and 100W, to change Ge ₂Sb ₂Te ₅The sputtering power of target obtains the film sample of different al doping.Undoped Ge ₂Sb ₂Te ₅Film sample is Ge ₂Sb ₂Te ₅Single target sputter obtains.The background vacuum pressure is 6.0 * 10 ^-6Mbar, working gas are high-purity argon (99.997%), and operating air pressure is 8.0 * 10 ^-3Mbar, sputtering time is 400s.And by XPS analysis the content of aluminium in the film sample.The film sample parameter and the numbering that prepare under the above condition are listed in the table below 1.

The Ge for preparing under table 1 different condition ₂Sb ₂Te ₅Film sample and aluminium content wherein

Sample number into spectrum	GST target sputtering power (W)	Al target sputtering power (W)	Al content (%)
				Al 0GST 100	75	0	0
Al 1.43GST 98.57	100	15	1.43
				Al 1.67GST 98.33	75	15	1.67

Sample number into spectrum	GST target sputtering power (W)	Al target sputtering power (W)	Al content (%)
				A l3.19 GST 96.81	50	15	3.19

Utilize the Al of X-ray diffractometer experiments of measuring preparation _x(Ge ₂Sb ₂Te ₅) _100-xSample structure under aluminum-doping phase transiting film and the differing temps after the annealing, the diffraction angle sweep limit is from 10.0 ° to 60.0 °, and sweep velocity is 2 °/min, and step-length is 0.02 °.Measure the gained result shown in Fig. 1～3.Only there is less fluctuating in Fig. 1 at about about 29 ° for the X ray diffracting spectrum of deposition attitude film before the thermal treatment, corresponding (200) peak, and deposition attitude film is non-crystalline state basically.Fig. 2 is Al _x(Ge ₂Sb ₂Te ₅) _100-xFilm sample is the X ray diffracting spectrum of 200 ℃ of annealing after 5 minutes under nitrogen atmosphere, and finding has tangible crystalline state FCC structure diffraction peak to occur after each film sample thermal treatment.Obviously, the film sample after Overheating Treatment has taken place by the phase transformation of non-crystalline state to crystalline state.Fig. 3 is Al _x(Ge ₂Sb ₂Te ₅) _100-xFilm sample is the X-ray diffractogram of 400 ℃ of annealing after 5 minutes under nitrogen atmosphere, finds not have adulterated Ge ₂Sb ₂Te ₅Film sample has become the HCP structure mutually, the adulterated Al of Al _x(Ge ₂Sb ₂Te ₅) _100-xFilm sample, though the HCP phase also occurred, FCC still exists mutually, the result shows: adulterated Al atom has suppressed the transformation that FCC arrives the HCP phase mutually to a certain extent.

Will be by the Al of design requirements preparation _x(Ge ₂Sb ₂Te ₅) _100-xThe aluminum-doping phase transiting film sample, the UVISEL of use temperature controllable ^TMType on-position measure ellipsometer carries out short annealing on the throne, carries out the measurement of optical constant simultaneously.Annealing region is from room temperature to 400 ℃, and temperature rise rate is 40-50 ℃/min, temperature-controlled precision ± 0.1 ℃.Annealing 4-8 minute at each temperature section in 8-12 ℃ of opticmeasurement temperature interval, and measures the optical constant of annealing specimen simultaneously, and the measure spectrum scope is 275.5～826.6nm.Measuring result as shown in Figure 4.Obviously, the variation of sample optical constant has reflected the variation of sample microstructure in essence.So, according to the result of variations of sample optical extinction coefficient in the experiment as can be known: along with the increase of Al doping ratio, film sample by disordered state to the Tc of FCC phase also in rising.By Fig. 4 (a) as can be seen: after 180 ℃ of annealing, do not have the optical extinction coefficient of the adulterated film sample of aluminium to tend towards stability, show and change the FCC phase into; Fig. 4 (b), after 180 ℃ of annealing, the Al that the Al doping content is minimum _1.43GST _98.57The optical extinction coefficient of film sample also tends towards stability, and shows also to have changed the FCC phase into.And among Fig. 4 (d), the Al that the Al doping content is the highest _3.19GST _96.81The optical extinction coefficient of film sample just tends towards stability after 200 ℃ of annealing, changes the FCC phase into, and the measuring result of this and XRD is coincide.

From experimental result, also can find out, after 380 ℃ of annealing, there is not the optical extinction coefficient of the film sample of doped with Al telomutation being arranged than long-wave band, according to XRD result as can be known, this moment, structure changed the HCP phase into mutually by FCC, and the adulterated film sample of Al is after 380 ℃ of annealing, and the variation of its optical extinction coefficient is all less.This shows that the Al doped samples has suppressed it by the FCC transformation of HCP phase in opposite directions, make its FCC more stable mutually.

The reflection contrast gradient of recording medium is important parameters in the phase transformation optical storage.For any recording medium of wiping rewriting, the key of practicability is to obtain higher signal to noise ratio.In the phase transformation optical storage, just require than higher reflection contrast C, C is defined as:

$C=2\×\left|\frac{R_c-R_a}{R_c+R_a}\right|\×100\%$

R wherein _cAnd R _aRepresent the reflectivity of recording medium when crystalline state and non-crystalline state respectively.

Fig. 5 has provided 200 ℃ of each Al of annealed _x(Ge ₂Sb ₂Te ₅) _100-xThe reflection contrast curves of film sample.As can be seen, when the content of Al when higher, the reflection contrast gradient all is significantly improved at whole wave band, particularly at the 630nm place, has reached 30%.With the adulterated Ge of no aluminium ₂Sb ₂Te ₅Film sample is compared, and has both made the wave band at 405nm, and its reflection contrast gradient has also brought up to 26% from 24%.The result shows that Al mixes and can improve the record signal to noise ratio of phase transformation optical storage at whole wave band.

Claims (3)

1. the preparation method of an aluminum-doping phase transiting storing thin-film material, the chemical structural formula of this thin-film material is: Al _x(Ge ₂Sb ₂Te ₅) _100-x, wherein 0＜x≤5 is characterized in that the concrete steps of this method are as follows: use magnetron sputtering coating system, with metallic aluminium target and Ge ₂Sb ₂Te ₅Target is installed in respectively in a magnetic control d.c. sputtering target and the magnetic control radio-frequency sputtering target, and wherein the purity of target all is better than 99.99%, and substrate adopts Si (100) substrate, and the background vacuum pressure is 4.0 * 10 ^-6Mbar-6.0 * 10 ^-6Mbar, working gas are the high-purity argon more than 99.997%, and operating air pressure is 6.0 * 10 ^-3Mbar-8.0 * 10 ^-3Mbar, plated film under the room temperature; In the sputter procedure, the sputtering power of metallic aluminium target is 15+1W, Ge ₂Sb ₂Te ₅The sputtering power of target is 40-100W, and sputtering time is 300 seconds-500 seconds; And realize the phase transformation of film at each warm area by annealing.

2. the preparation method of aluminum-doping phase transiting storing thin-film material according to claim 1, the sputtering power that it is characterized in that fixing metal aluminium target is 15W, Ge ₂Sb ₂Te ₅The sputtering power of target is 50-100W.

3. the preparation method of aluminum-doping phase transiting storing thin-film material according to claim 1 is characterized in that annealing temperature is that scope is a room temperature-400 ℃, and temperature rise rate is 40 ℃/min-50 ℃/min, temperature-controlled precision ± 0.1 ℃.

Images