CN110295348A - It is a kind of that HfO is prepared using Pulsed laser molecular beam epitaxy2The method of film - Google Patents

Abstract

HfO is prepared using Pulsed laser molecular beam epitaxy the invention discloses a kind of₂The method of base film, belongs to technical field of material.Using YSZ as substrate, substrate is cleaned and is made annealing treatment first, sufficiently removes the internal stress and surface organic matter of substrate；Then using metal hafnium and doped chemical as target, under ultravacuum state, HfO is grown in substrate surface using Pulsed laser molecular beam epitaxy method₂Base film；In-situ annealing processing is carried out to the film grown later, obtains stable HfO₂Base film.The present invention is using pulse laser deposition and molecular beam epitaxy combination, and refletcion high-energy electron diffraction instrument is combined to monitor in real time, by being optimized to oxygen pressure, laser energy, underlayer temperature and annealing temperature, realize the accurate control of film atomic scale epitaxial growth, have the advantages that purity is high, layer structure are controllable, while the basic research for corresponding high-order harmonics spectrum and film forming procedure provides thinking.

Description

It is a kind of that HfO is prepared using Pulsed laser molecular beam epitaxy2The method of film

Technical field

The invention belongs to technical field of material more particularly to a kind of use Pulsed laser molecular beam epitaxy to prepare HfO₂The method of base film.

Background technique

As microelectronic integrated circuit product constantly develops to high-performance and high density direction, the feature of transistor arrangement Size constantly reduces, when characteristic size enters 0.1 μm or less range, traditional silica (SiO₂) gate dielectric layer thickness " physics limit " close to 2nm is spent, electronics Direct Tunneling Effect causes grid leakage current increased dramatically, so that device be made to face Serious stability and integrity problem.In recent years, hafnium oxide (HfO₂) film with its higher relative dielectric constant, compared with Big forbidden bandwidth (5.8eV), preferable thermal stability and chemical stability, etc. compatible with standard semiconductor integrated technique are excellent Point is widely used to the large-scale industrial production of microprocessor and dynamic RAM (DRAM).

Currently, HfO₂The preparation method of film mainly has magnetron sputtering, pulse laser deposition, chemical vapor deposition etc.. Wherein, magnetron sputtering is the positive ion bombardment target material surface that will have certain energy, sputters atom and molecule from the surface of solids Become gas, is finally film in deposition on substrate, because its deposition and atomic kinetic energy is high, there is film to be combined with substrate, densification Property it is good, at the good advantage of film uniformity, but when sputtering oxide-insulator target, sputtering object is easy covering anode, leads to aura Voltage needed for discharging is unable to maintain that；Pulse laser deposition is that will there is the laser beam of certain energy to be irradiated on target, makes its office Portion's temperature increases rapidly, and fusion and gasification is gaseous atom, to be film in deposition on substrate, it is ensured that film component and target Ingredient height is consistent, quality of forming film and film purity is high, but is unable to accurately control film thickness, it is difficult to prepare the super of atomic layer scale Thin gauge film；Chemical vapor deposition is after the volatile compound of substance to be filmed gasifies, decompose on substrate, The reactions such as reduction, oxidation, displacement, film substrate needed for being formed and are deposited on substrate, byproduct of reaction in a gaseous form by It guides, deposition rate is fast, but is difficult to prepare high-precision ultra-thin type film, and film equality and purity are low.

In view of the above-mentioned problems of the prior art, being badly in need of providing a kind of efficient HfO₂The preparation method of base film, it is real The preparation of the controllable ultrathin film of existing high-purity, thickness.

Summary of the invention

It is prepared in view of the above existing problems in the prior art, the present invention provides a kind of using Pulsed laser molecular beam epitaxy HfO₂The method of base film is combined using pulse laser deposition and molecular beam epitaxy, and combines refletcion high-energy electron diffraction instrument real When monitoring, it can be achieved that film atomic scale epitaxial growth accurate control, apply also for HfO₂The multi-element doping of base film, Complex layered structure-controllable, while also can be carried out the basic research of corresponding high-order harmonics spectrum and film forming procedure.

To achieve the above object, the present invention is implemented with the following technical solutions:

It is a kind of that HfO is prepared using Pulsed laser molecular beam epitaxy₂The method of base film, which is characterized in that including following step It is rapid:

S1. cleaning and polishing treatment are carried out to YSZ substrate, then the YSZ substrate after cleaning is put into tube furnace Anneal 2-3h at 1150-1250 DEG C.

S2. the YSZ substrate after step S1 annealing is put into growth room, under ultra-high vacuum state, is swashed using pulse Light bombardment metal hafnium target and dopant target, it is raw on the YSZ substrate of certain temperature that target fusion and gasification forms gaseous atom It is long, the plasma of oxygen is passed through in growth course；

S3. the sample after the completion of growth is subjected to in-situ annealing processing, stable HfO is made₂Base film.

Further, in step S1, the YSZ substrate refers to the stable zirconium oxide of yttrium, high preferred orientation can for (100), (110), one of (111) three kinds of high preferred orientations.

Further, by the monitoring and research of the growth to different high preferred orientation film on substrate, to explore film growth The rule of dynamic behavior provides thinking.

Further, in step S2, the dopant target is one of yttrium, zirconium, aluminium, silicon, germanium, strontium or neodymium target, described Metal hafnium target and dopant target purity are greater than 99.999%, and metal hafnium and dopant molar ratio are 1:0.01-1.

Further, in the growth course of step S2, using refletcion high-energy electron diffraction instrument (RHEED) to growing surface Pattern and crystallization situation are monitored in real time, and the refletcion high-energy electron diffraction instrument can also monitor film thickness.

Further, in step S2, vacuum degree is less than 1 × 10 in the growth room^-8Torr, in growth course, growth room's gas Pressure is 2.2 × 10^-6-4.2×10^-6torr。

Further, in step S2, in step S2, the underlayer temperature is 400-580 DEG C, the pulse laser beam difference Bombardment metal hafnium target and dopant target, energy 200-320mJ, frequency 20-30Hz, the oxygen plasma source power are 350-400W。

Further, in step S2, the growth time is 5-40min, when one timing of laser energy and frequency, passes through control Made membrane growth time prepares required film thickness.

Further, in step S3, the in-situ annealing temperature is 600-800 DEG C, and annealing atmosphere is oxygen, annealing time For 20-40min, facilitate HfO under oxygen atmosphere₂Crystallization, obtain the complete high-quality thin film of crystallinity.

Further, in order to improve film growth rate, film purity and stability, the underlayer temperature, laser energy are improved It is necessary to meet following condition for the setting of amount, oxygen plasma power, growth time, annealing temperature:

A. guarantee film substrate be thermodynamically infiltration, that is, meet following equation:

γ_sub> γ_film+E_interface

Wherein, γ_subIt is the surface energy of substrate, γ_filmIt is the surface energy of film, E_interfaceIt is the boundary of film and substrate Face energy；

B. system temperature wants sufficiently high, so that atomic energy reaches substrate across energy barrier；

C. the chemical potential of oxidation film wants sufficiently high, to form the phase needed, it usually needs higher partial pressure of oxygen and larger Oxygen activity, such as use oxygen plasma or ozone；

D. underlayer temperature will be suitable for, to guarantee HfO₂The growth of film, and inhibit its desorption.

Further, HfO prepared by the present invention₂Base film with a thickness of 1-30nm.

It is provided by the invention a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The principle of base film are as follows: steady with yttrium Fixed zirconium oxide is substrate, is cleaned, polished and is made annealing treatment to substrate, is cleaned, is orderly, smooth substrate, super Under vacuum state, with high energy pulse laser bombardment metal hafnium and dopant target, and it is passed through the plasma of oxygen, target is former Son fusion and gasification under vapour pressure is gaseous atom, and gaseous atom is depressed in active oxygen, is deposited on the substrate surface of certain temperature Epitaxial growth is hafnia film, in growth course, by refletcion high-energy electron diffraction instrument to growing film surface topography, knot Brilliant situation and thickness are monitored in real time, and when reaching required thickness, then the bombardment of stop pulse laser is centainly being annealed At a temperature of anneal, obtain the good HfO of crystallinity complete, purity is high, stability₂Base film, entire film growth and annealing process Preparation condition according to Pulsed laser molecular beam epitaxy grow HfO₂The thermodynamics and kinetics condition of base film indispensability is set, Reliability is higher.

Beneficial effect

Compared with prior art, the invention has the following beneficial effects:

(1) present invention is combined using pld (pulsed laser deposition) and molecular beam epitaxy, and combines refletcion high-energy electron diffraction Instrument real time monitoring, realizes the accurate control of film atomic scale epitaxial growth, has the advantages that purity is high, layer structure are controllable, Ultra-thin HfO can be prepared₂Base film, while being improved for the basic research of corresponding high-order harmonics spectrum and film forming procedure Thinking；

(3) present invention while selecting high-purity dopant using high purity metal hafnium as target, by strict control oxygen pressure, High-purity doping HfO can be prepared₂Base film, while can be prepared by the growth course of adjusting metal hafnium and dopant To the element doping HfO of various complex layered structure-controllables₂Base film.

(3) present invention is by determining that Pulsed laser molecular beam epitaxy grows HfO₂The thermodynamics and power of base film indispensability Condition optimizes oxygen pressure, laser energy, underlayer temperature and annealing temperature, and realization is made under best film growth conditions Standby HfO₂Base film is remarkably improved film growth rate, improves film purity and stability；

(4) HfO of the present invention₂Rationally, epitaxial growth efficiency can be improved in the setting of base film epitaxial growth conditions, improves film Purity, uniformity and stability.

Specific embodiment

Clear, complete description is carried out below with reference to technical solution of the attached drawing to various embodiments of the present invention, it is clear that is retouched The embodiment stated is only a part of the embodiments of the present invention, instead of all the embodiments；Based on the embodiment of the present invention, originally Field those of ordinary skill obtained all other embodiment without making creative work, belongs to this hair Bright protected range.

It is provided by the invention a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, the pulse Laser molecular beam epitaxy grows HfO₂The necessary condition of base film are as follows:

A. guarantee film substrate be thermodynamically infiltration, that is, meet following equation:

γ_sub> γ_film+E_interface

Wherein, γ_subIt is the surface energy of substrate, γ_filmIt is the surface energy of film, E_interfaceIt is the boundary of film and substrate Face energy；

B. system temperature wants sufficiently high, so that atomic energy reaches substrate across energy barrier；

C. the chemical potential of oxidation film wants sufficiently high, to form the phase needed, it usually needs higher partial pressure of oxygen and larger Oxygen activity, such as use oxygen plasma or ozone；

D. underlayer temperature will be suitable for, to guarantee HfO₂The growth of film, and inhibit its desorption.

In the case where meeting above-mentioned necessary condition, the present invention uses Pulsed laser molecular beam epitaxy method, grows on YSZ substrate HfO₂Base film.

Obtain good epitaxial film, it is necessary first to be cleaned, is orderly, smooth substrate surface.For this purpose, of the invention Chemically YSZ substrate is repeatedly corroded, removes the various weight foreign ions on the surface YSZ, while to YSZ table Face carries out chemical polishing, is finally made annealing treatment, the specific steps are as follows:

1. it is 80 DEG C in temperature, H₂SO₄:H₂O₂5 minutes are kept the temperature in the solution of=3:1, then with HF (10%) rinsing 10 Second；

2. it is 80 DEG C in temperature, not diluted HNO₃Then middle heat preservation 3-5 minutes is rinsed 10 seconds with HF (10%)；

3. it is 80 DEG C in temperature, NH₄OH:H₂O₂:H₂3-5 minutes are kept the temperature in the solution of O=1:1.5:4, then uses HF (10%) it rinses 10 seconds；

4. it is 80 DEG C in temperature, HCI:H₂O₂:H₂5 minutes are kept the temperature in the solution of O=3:1:1, is then floated with HF (10%) It washes 10 seconds；

5. the YSZ substrate after cleaning is put into tube furnace at 1150-1250 DEG C the 2-3h that anneals.

It is packed into Sample Room by the substrate of chemical cleaning and annealing, is evacuated to 10 from atmosphere by turbomolecular pump^-6Torr Near, then by ionic pump Sample Room is evacuated to 10^-7Torr or so.Guaranteeing what the ultrahigh vacuum of growth room was not destroyed in this way Under the conditions of, can fast sample and carry out substrate pretreatment.Then in Sample Room by silicon to 300 DEG C and keep 3 points The various foreign gases of adsorption are desorbed in clock, are then sent into growth room by magnetic force sample transmission rod, at this moment vacuum degree should be less than 1 ×10^-8Torr。

Embodiment 1

It is a kind of that HfO is prepared using Pulsed laser molecular beam epitaxy₂The method of base film, selecting high preferred orientation is (100), The stable zirconium oxide of yttrium (YSZ) is substrate, selects metal hafnium of the purity greater than 99.999% and metal zirconium is object target, gold Belong to hafnium and metal zirconium molar ratio is 1:0.5, prepares zirconium doping HfO₂Base film, specifically includes the following steps:

S1. YSZ substrate is cleaned, polished and is made annealing treatment, specifically comprised the following steps:

It S11. is 80 DEG C in temperature, H₂SO₄:H₂O₂5 minutes are kept the temperature in the solution of=3:1, is then rinsed with HF (10%) 10 seconds；

It S12. is 80 DEG C in temperature, not diluted HNO₃Middle heat preservation 5 minutes, is then rinsed 10 seconds with HF (10%)；

It S13. is 80 DEG C in temperature, NH₄OH:H₂O₂:H₂5 minutes are kept the temperature in the solution of O=1:1.5:4, then uses HF (10%) it rinses 10 seconds；

It S14. is 80 DEG C in temperature, HCI:H₂O₂:H₂5 minutes are kept the temperature in the solution of O=3:1:1, then uses HF (10%) Rinsing 10 seconds；

S15. the YSZ substrate after cleaning is put into tube furnace at 1150-1250 DEG C the 2-3h that anneals.

S2. the YSZ substrate after step S1 annealing is put into growth room, in ultra-high vacuum environment, is swashed using pulse Light bombardment metal hafnium target and dopant target, it is raw on the YSZ substrate of certain temperature that target fusion and gasification forms gaseous atom Long, when growth, is passed through the plasma of oxygen, specifically comprises the following steps:

S21. film growth conditions is selected according to the following conditions:

A. calculating the surface substrate YSZ can γ_sub, doping HfO₂It base film surface can γ_filmAnd the interface energy of film and substrate E_interface, guarantee film is thermodynamically infiltration substrate, that is, meet following equation:

γ_sub> γ_film+E_interface

B. laser energy wants sufficiently high, guarantees that system temperature reaches target atom evaporating temperature, so that atomic energy is across energy It builds and reaches substrate；

C. guarantee enough partials pressure of oxygen and oxygen activity, so that the chemical potential of oxidation film forms the phase of needs enough；

D. underlayer temperature will be suitable for, to guarantee HfO₂The growth of film, and inhibit its desorption；

S22. substrate is packed into Sample Room, is evacuated to 10 from atmosphere by turbomolecular pump^-6Near Torr, then will by ionic pump Sample Room is evacuated to 10^-7Torr or so；

S23. in Sample Room by YSZ silicon to 300 DEG C and keep 3 minutes, make the various foreign gases of adsorption Then desorption is sent into growth room by magnetic force sample transmission rod, at this moment vacuum degree should be less than 1 × 10^-8Torr；

S24. YSZ underlayer temperature is risen to 500 DEG C, opens pulsed laser ablation metal hafnium target and dopant target, carried out HfO₂The growth of base film, wherein the pulsed laser energy of bombardment metal hafnium is 280mJ, bombards the pulse laser energy of metal zirconium Amount is 260mJ；In growth course, oxygen plasma source operating power is 400W, and growth air pressure is 3.4 × 10^-6Torr, growth Time is 30min, during which according to doping and required layer structure, controls two kinds of target bombardment times and bombardment frequency； In growth course, surface topography and crystallization situation are monitored by RHEED in situ；

S3., sample after the completion of growth is carried out to in-situ annealing processing, annealing temperature under an atmospheres oxygen atmosphere It is 700 DEG C, annealing time 30min, stable zirconium doping HfO is made₂Base film in annealing process, is monitored by RHEED Surface topography and crystallization situation.

It is detected, the zirconium doping HfO being prepared₂Base film with a thickness of 20nm.

Embodiment 2

It is a kind of that HfO is prepared using Pulsed laser molecular beam epitaxy₂The method of base film, selecting high preferred orientation is (100), The stable zirconium oxide of yttrium (YSZ) is substrate, selects metal hafnium of the purity greater than 99.999% and metallic yttrium is object target, gold Belonging to hafnium and metallic yttrium molar ratio is 1:0.3, prepares doped yttrium HfO₂Base film.Method for manufacturing thin film compared with Example 1, no It is with place, step S24 are as follows: YSZ underlayer temperature is risen to 450 DEG C, opens pulsed laser ablation metal hafnium target and dopant Target carries out HfO₂The growth of base film, wherein the pulsed laser energy of bombardment metal hafnium is 280mJ, bombards the arteries and veins of metal zirconium Impulse light energy is 230mJ；In growth course, oxygen plasma source operating power is 380W, and growth air pressure is 3.0 × 10^{- 6}Torr, growth time 30min control two kinds of target bombardment times during which according to doping and required layer structure And bombardment frequency；In growth course, surface topography and crystallization situation are monitored by RHEED in situ；

Step S3 are as follows: the sample after the completion of growth is subjected to in-situ annealing processing under an atmospheres oxygen atmosphere, is moved back Fiery temperature is 650 DEG C, annealing time 20min, and stable doped yttrium HfO is made₂Base film in annealing process, passes through RHEED monitors surface topography and crystallization situation.

It is detected, the doped yttrium HfO being prepared₂Base film with a thickness of 12nm.

Embodiment 3

It is a kind of that HfO is prepared using Pulsed laser molecular beam epitaxy₂The method of base film, selecting high preferred orientation is (110), The stable zirconium oxide of yttrium (YSZ) is substrate, selects metal hafnium of the purity greater than 99.999% and metal praseodymium is object target, gold Belonging to hafnium and metal praseodymium molar ratio is 1:0.02, prepares praseodymium doped HfO₂Base film method for manufacturing thin film compared with Example 1, no It is with place, step S24 are as follows: YSZ underlayer temperature is risen to 480 DEG C, opens pulsed laser ablation metal hafnium target and dopant Target carries out HfO₂The growth of base film, wherein the pulsed laser energy of bombardment metal hafnium is 280mJ, bombards the arteries and veins of metal zirconium Impulse light energy is 250mJ；In growth course, oxygen plasma source operating power is 380W, and growth air pressure is 3.0 × 10^{- 6}Torr, growth time 25min control two kinds of target bombardment times during which according to doping and required layer structure And bombardment frequency；In growth course, surface topography and crystallization situation are monitored by RHEED in situ；

Step S3 are as follows: the sample after the completion of growth is subjected to in-situ annealing processing under an atmospheres oxygen atmosphere, is moved back Fiery temperature is 600 DEG C, annealing time 20min, and stable praseodymium doped HfO is made₂Base film in annealing process, passes through RHEED monitors surface topography and crystallization situation.

It is detected, the praseodymium doped HfO being prepared₂Base film with a thickness of 10nm.

Embodiment 4

The present embodiment compared with Example 1, the difference is that, the stable zirconium oxide of yttrium used (YSZ) substrate crystal face takes To for (111), other are all the same with embodiment 1, the zirconium doping HfO being prepared₂Base film with a thickness of 20nm.

Embodiment 5-11

Compared with Example 1, embodiment 5-11 the difference is that, the preparation condition of step S24 and step S3 such as table Shown in 1, other are all the same with embodiment 1.

1 embodiment 5-10 film preparation condition of table

The HfO that embodiment 5-11 is prepared₂Base film thickness is as shown in table 2, it is found that by controlling laser energy Amount and growth time, can prepare thickness down to 1nm HfO₂Base film.

The film thickness of 2 embodiment 5-10 of table preparation

Embodiment	5	6	7	8	9	10	11
								Thickness (nm)	20	25	30	15	10	5	1

The foregoing is only a preferred embodiment of the present invention, but protection scope of the present invention be not limited to This, anyone skilled in the art in the technical scope disclosed by the present invention, according to the technique and scheme of the present invention And its inventive concept is subject to equivalent substitution or change, should be covered by the protection scope of the present invention.

Claims (10)

1. a kind of prepare HfO using Pulsed laser molecular beam epitaxy₂The method of base film, which comprises the following steps:

S1. cleaning and polishing treatment are carried out to YSZ substrate, then the YSZ substrate after cleaning is put into tube furnace in 1150- Anneal 2-3h at 1250 DEG C；

S2. the YSZ substrate after step S1 annealing is put into growth room, under ultra-high vacuum state, using pulse laser beam Metal hafnium target and dopant target are bombarded, target fusion and gasification forms gaseous atom and grows in the YSZ substrate surface of certain temperature, raw The plasma of oxygen is passed through in growth process；

S3. the sample after the completion of growth is subjected to in-situ annealing processing, stable HfO is made₂Base film.

2. according to claim 1 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, feature It is, in step S1, the YSZ substrate refers to that yttria stabilized zirconia, high preferred orientation can be (100), (110), (111) three Any one of kind high preferred orientation.

3. according to claim 1 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, feature Be, in step S2, the dopant target is one of yttrium, zirconium, praseodymium, silicon, germanium, strontium or neodymium target, the metal hafnium target and Dopant target purity is greater than 99.999%, and metal hafnium and dopant molar ratio are 1:0.01-1.

4. according to claim 1 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, feature It is, in the growth course of step S2, growing surface pattern and crystallization situation is carried out using refletcion high-energy electron diffraction instrument Real time monitoring, the refletcion high-energy electron diffraction instrument can also monitor film thickness.

5. according to claim 1 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, feature It is, in step S2, vacuum degree is less than 1 × 10 in the ultravacuum growth room^-8Torr, in growth course, growth room's air pressure is 2.2×10^-6-4.2×10^-6torr。

6. according to claim 1 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, feature It is, in step S2, the underlayer temperature is 400-580 DEG C, and the pulse laser beam bombards metal hafnium target and dopant respectively Target, energy 200-320mJ, frequency 20-30Hz, the oxygen plasma source power are 350-400W.

7. according to claim 1 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, feature It is, in step S2, the film growth time is 5-40min, raw by control film when one timing of laser energy and frequency For a long time, required film thickness is prepared.

8. according to claim 1 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂The method of base film, feature It is, in step S3, the in-situ annealing temperature is 600-800 DEG C, and annealing atmosphere is oxygen, annealing time 20-40min.

9. described in any item a kind of using Pulsed laser molecular beam epitaxy preparation HfO according to claim 5 to 8₂The side of base film Method, which is characterized in that the setting of the underlayer temperature, laser energy, oxygen plasma power, growth time, annealing temperature needs Meet the following conditions:

A. guarantee film substrate be thermodynamically infiltration, that is, meet following equation:

γ_sub> γ_film+E_interface

Wherein, γ_subIt is the surface energy of substrate, γ_filmIt is the surface energy of film, E_interfaceIt is the interface energy of film and substrate；

B. system temperature wants sufficiently high, so that atomic energy reaches substrate across energy barrier；

C. the chemical potential of oxidation film wants sufficiently high, to form the phase needed, it usually needs higher partial pressure of oxygen and biggish oxygen Activity such as uses oxygen plasma or ozone；

D. underlayer temperature will be suitable for, to guarantee HfO₂The growth of film, and inhibit its desorption.

10. according to any one of claims 1 to 8 a kind of using Pulsed laser molecular beam epitaxy preparation HfO₂Base film Method, which is characterized in that the HfO of preparation₂Base film with a thickness of 1-30nm.